Method of rectification separation of fluid containing acrylic acid

FIELD: process engineering.

SUBSTANCE: invention relates to rectification separation of fluid containing acrylic acid whereat said fluid is fed through loading point to rectification column and mass flow is discharged there through at discharge point arranged above said loading point. Content of acrylic acid in said mass flow in terms of mass flow weight makes ≥90 % by weight and exceeds acrylic acid content in fluid in rectification column zone located at least two theoretical separation stages above said loading point. Content of di-acrylic acid in reflux in terms of reflux weight in at least partial zones, makes ≥550 ppm by weight. Note here that said content of di-acrylic acid in reflux is defined from the presence of Bronsted acid with pKa ≤ 16 in fluid containing acrylic acid, or at least one Bronsted base with pKb ≤ 10, and/or adding to reflux of at least one compound from the group comprising aforesaid Bronsted acid with pKa ≤ 16, Bronsted base with pKa ≤ 10, di-acrylic acid and acrylic acid that contains acrylic acid. That is, mass flow enriched with acrylic acid is discharged from rectification column at the point above loading point while radial polymerisation is inhibited by di-acrylic acid at rectification column top.

EFFECT: efficient separation of fluids.

23 cl, 3 ex

 

The present invention relates to a method of distillation separation of a liquid containing acrylic acid, in which the liquid containing acrylic acid, is fed through a download location to a distillation column, and the download location of the distillation column in place of unloading unload the mass flow, the content of acrylic acid in which, calculated on the weight of the mass flow is ≥90 wt.% and is higher than the corresponding content of acrylic acid in the liquid in wt.%.

Under the liquid in the download location should be same mass flow, which is more than 80%, preferably more than 85%, or more than 90%, or more than 95%, or more than 99% of the total available as of the condensed phase. In other words, the present invention does not include the methods of fractional or full condensation, as described, for example, in DE-A 19924532 or DE-A 19924533.

Acrylic acid due to its reactive double bonds, as well as their acid function is a valuable monomer for polymerization products, which, for example, used as a water absorbent resin.

In addition, acrylic acid can be obtained heterogeneous catalytic partial oxidation in the gas phase of propene, propane and/or acrolein oxygen or gas containing color is d, in the presence of solid catalysts at elevated temperatures (see, for example, EP-A 700714).

However, when implementing this method are not pure acrylic acid, and a mixture of the product gas, which, along with acrylic acid as a side component contains unreacted acrolein and/or propene, and components such as water vapor, carbon oxides (CO, CO2), nitrogen, oxygen, propane, methane, lower saturated carboxylic acids, such as formic, acetic and propionic acid, lower aldehydes such as formaldehyde, benzaldehyde, acrolein and furfural, and higher carboxylic acids or their anhydrides, such as benzoic acid, phthalic anhydride and maleic acid anhydride.

Main compartment acrylic acid from a gaseous mixture of the product gas is carried out, as a rule, by absorption in a solvent (e.g. water or an organic solvent) or by fractional condensation of a mixture of the product gas. After that obtained when the condensate or absorbed rectification (usually in several stages) to share more or less pure acrylic acid (cf. WO 03/051810, EP-A 982289, EP-A 982287, DE-A 19606877 and DE-A 10224341). Instead of fractional condensation, first it is possible to carry out a full condensation, and the resulting condensate to separate rectify is the situation.

The disadvantage of distillation separation of a liquid containing acrylic acid, is the fact that we are talking about thermal separation processes in which the required separation requires a supply of thermal energy. This separation is disadvantageous, since in the liquid phase acrylic acid, in particular, under the influence of thermal energy are prone to undesired free-radical polymerization.

Despite the additional use of a radical polymerization inhibitors (e.g., such as fentazin, simple onomatology ether of hydroquinone, hydroquinone, N-oxylene radicals etc), distillation separation of liquids containing acrylic acid, it is necessary from time to time to suspend removal of the distillation column formed in the process of rectification unwanted product of polymerization (particularly in its upper part) (see, for example, DE-A 19746688, DE-A 10211273, DE-A 19536179, EP-A 1033359 and DE-10213027).

However, this stopping operation of the distillation column is equivalent production losses, why in the world have taken a huge effort to find an improved system of polymerization inhibitors, which would allow to implement a longer distillation separation of liquids containing acrylic acid.

Last, cha is in the surrounding area, refers to the zone of the distillation column, which is located above the loading shared by distillation liquid containing acrylic acid. The reason for this is, among other things, that in this zone accumulate such by-products that are more volatile than acrylic acid. However, many of these volatile by-products (e.g., acrolein) increase the tendency of acrylic acid radical polymerization (see, for example, EP-A 1041062), so its inhibition in this area is of particular importance.

The disadvantage of known methods for distillation separation of a liquid containing acrylic acid, in which the liquid containing acrylic acid load in the distillation column, and above the loading of the distillation column unload the mass flow, the content of acrylic acid in which ≥90 wt.% and is higher than the content of acrylic acid in the liquid, is that the inhibition of polymerization in the upper part of the distillation column is insufficient. Thus, the present invention is to improve the inhibition of polymerization.

Others, as a rule, undesirable side-effects of acrylic acid in the condensed phase is the formation of oligomers containing ≥Monomeric units, by joining Michael acrylic acid to another molecule of acrylic acid, and formed the dimer of acrylic acid (oligomer). For statistical reasons, of particular importance is primarily education diacrylates acid

while the formation of higher oligomers of acrylic acid (trimers, tetramers, etc.) can in General be neglected.

Because dikalova acid has a less pronounced tendency to free-radical polymerization of acrylic acid, it is required that the acrylic acid contained as low as possible amount of diacrylates acid (see DE-a 19923389, DE-A 19627679 and WO-03/064367). First of all, because education diacrylates acid is reversible, and in the case of radically copolymerizable diacrylates acid during the subsequent thermal treatment of the product of polymerization (for example, when drying resin, absorbing water) can be chipped off of Monomeric acrylic acid, which generally is undesirable.

Department diacrylates acid from acrylic acid, due to their significantly different boiling points can be realized by a simple method of rectification. Dikalova acid accumulates in the lower part of the distillation column, and acrylic acid in the upper part of the column, which, as a rule is, contains almost no diacrylate acid, primarily because education diacrylates acid is a very long process.

If acrylic acid under normal conditions to provide for some time to herself, education 150 hours/million, diacrylates acid, depending on the weight of acrylic acid, will take approximately 24 hours. Thus, the presence diacrylates acid in the upper part of the distillation column due to the above is still undesirable.

Unexpectedly, it was found that dikalova acid, present in the radical polymerization of acrylic acid, active inhibitor of polymerization, which formed the basis of the present invention. This is because dikalova acid has a less pronounced tendency to radical polymerization in comparison with acrylic acid. In all probability contained in the acrylic acid dikalova acid due to its less pronounced tendency to polymerization affects the size of circuits of polymerization products of acrylic acid in the radical polymerization as the agent of the termination of the growing chains.

Thus, underlying the invention the task is solved by the method of distillation separation of a liquid containing acrylic acid, according to which the LM is bone, contains acrylic acid, is fed through a download location to a distillation column, and the download location of the distillation column in place of unloading unload the mass flow, the content of acrylic acid in which, calculated on the weight of the mass flow is ≥90 wt.% and is higher than the corresponding content of acrylic acid in the liquid in wt.%, which is characterized by the fact that within the zone of the distillation column, which is at least two theoretical stages of separation above content diacrylates acid in the phlegm, calculated on the weight of phlegmy, at least in partial areas is ≥550 hours/million by weight.

Inside of the distillation column descending liquid phase (phlegm) and the ascending vapour phase serves countercurrent to each other. The result is formed between the mass flow imbalance occurs heat and mass transfer, which causes the desired separation process. Typically, distillation column to increase the volume of mass transfer has built effective separation elements. As such this method is used, for example, gaskets, nozzles and/or mass transfer plates of any kind.

Mass transfer plates, in which there is a balance between the descending liquid phase and an ascending vapor, called Teoreticheskie the mi plates. This concept also applies to all other built-in effective separation of the elements used for rectification in a counter (for example, gaskets and nozzles).

Thus, in the present invention in General we are talking about theoretical stage of separation. Under theoretical stage of separation imply such a unit volume, which contributes to the enrichment in accordance with thermodynamic equilibrium.

The method according to the invention is particularly suitable in the case where the content of acrylic acid in the mass flow rate of ≥93 wt.% or ≥95 wt.%. However, it is advantageously used when the content of acrylic acid in the mass flow rate ≥97 wt.%, or ≥98 wt.%, or ≥99 wt.%, or of 99.5 wt.%, or ≥99,8 wt.%.

Preferably in the process according to the invention the content diacrylates acid in the phlegm, calculated on the weight of phlegmy, within the zone of the distillation column located on at least two (or three, or four, or five) theoretical stage of separation above the location of the boot, at least in partial areas not only ≥550 hours/million by weight, and ≥600 hours/million by weight, or ≥650 hours/million by weight, or ≥700 hours/million by weight, or ≥750 hours/million by weight or ≥800 hours/million by weight.

Particularly preferably, the content diacrylates acid in the implementation of the JV the soba according to the invention is ≥850 hours/million by weight, or ≥900 hours/million by weight, or ≥950 hours/million by weight, or ≥1000 hours/million by weight.

Even more preferably above content diacrylates acid in the process according to the invention is ≥1250 hours/million by weight, or ≥1500 hours/million by weight, or ≥1750 hours/million by weight, or ≥2000 hours/million by weight, or ≥2500 hours/million by weight, or ≥3000 hours/million by weight.

However, the aforementioned content diacrylates acid does not exceed 10 or 5 wt.%, it usually ≤3 wt.% or ≤2 wt.%.

According to the invention is suitable above preferred within the framework of the invention the content diacrylates acid in the phlegm, at least in the zone of the distillation column, at least two theoretical stages of separation above the location of the boot, which, proceeding from the outlet mass flow is in the range from 0.5-5 theoretical stages of separation.

The method according to the invention is particularly advantageous when the above preferred content diacrylates acid in the phlegm are available throughout the area, located in a distillation column, at least two, or at least four, or at least six, or at least eight, or more theoretical stages of separation above the location of the download.

However, the method according to the invention is advantageous when the unloading site h is located on, at least two or at least four, or at least six, or at least eight or more theoretical stages of separation above download and all values of the content diacrylates acid in the phlegm are available throughout the area of the distillation column above the point of unloading.

With the method according to the invention the place of unloading is at least 2, or at least 5, or at least 8, or at least 10 or at least 12 theoretical stages of separation over the download location of the distillation column.

The preferred methods of distillation separation according to the invention are above the place of unloading is also at least 0,5, or at least 1, or at least 1,5 theoretical stage of separation.

Dikalova acid, which in the process according to the invention, if necessary, is contained in the discharged mass flow, can, at need, to be separated at the subsequent stages of separation. This phase separation can be, for example, crystallization or distillation character. The latter is especially true for those cases where rectification is carried out in such conditions, in which the tendency of acrylic acid to the polymerization decreases and does not require any additional inhibition by the measures contained in the phlegm diacrylates acid. Separated at this dikalova acid may be a known manner (see, for example, WO 03/048100) split to acrylic acid.

Necessary according to the invention the regulation of the content of diacrylates acid in the phlegm can be done in various ways, for example in the phlegm (for example, the head of the column) can be submitted other than acrylic acid acid Bronsted, which catalyzes the joining of acrylic acid on Michael. According to the invention the strength of such acid Branstad expressed its value PKand(at 25°C, 1 ATM, water as a solvent; see Grundlagen der allgemeinen und anorganischen Chemie, H.R.Christen, Verlag Sauerländer, Aarau, 1973, S.354) is ≤16, preferably ≤7, particularly preferably ≤5.

Especially preferred according to the invention are, for example, H2O and strong proton mineral acid, such as H2SO4, HCl, or H3PO4. Among them, particular preference is given to volatile mineral acids (or more volatile than acrylic acid, i.e. acids Branstad with a lower boiling point than acrylic acid, when PKand≤16). In the lower part of the distillation columns, catalytic activity of mineral acid can be eliminated by adding a neutralizing base Branstad.

Instead of the acids Given which you can also add base Branstad, catalyzes the formation of diacrylates acid. According to the invention the strength of such base Branstad expressed in its value PKand(at 25°C, 1 ATM, water as a solvent; see Grundlagen der organischen Chemie, H.R.Christen, Verlag Sauerländer, Aarau, 1975, S.392) is ≤10, preferably ≤8 and particularly preferably ≤5. According to the invention is especially suitable are, for example, amine base Branstad, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, tetramethylethylenediamine, n-Propylamine, n-butylamine, benzylamine, pyridine, aniline, urea or ammonia. Among them, particular preference is given to volatile aminoven grounds of Branstad. Of course, in the head of the column, you can add the corresponding aqueous solutions. In the lower part of the distillation column catalytic activity base Bronsted can again be eliminated by adding a neutralizing acid Branstad. However, if necessary, towards the lower part of the distillation column is automatic elimination of catalytic activity base Branstad in which they are dwindling down temperatures react with acrylic acid to the formation of the corresponding amides and accumulate in Cuba columns.

Additionally or alternatively, the above substances, on the example of water, you can also add in the subject of the separation liquid. This is especially adding more volatile than acrylic acid, acids or bases Bronsted. If the liquid is produced by absorption of acrylic acid from mixtures of the reaction gas obtained by partial oxidation, the addition can be carried out in the absorption process.

Needless to say in the process according to the invention can also add the necessary diacrylate acid phlegmy as such. Diacrylate acid is obtained, for example, in such a way that first it is enriched acrylic acid, and then allocate by distillation or crystallization. Instead additives selected diacrylates acid may be added to the phlegm is also rich diacrylates acid acrylic acid in the upper part of the distillation column. This acrylic acid is preferable to add other necessary in a distillation column inhibitor of polymerization. Of course, in this case, the acrylic acid, the purity of which, despite it contains, if necessary, the inhibitor of at least corresponds to the degree of purity mass flow P to be the separation method according to the invention, enrich diacrylates acid.

Naturally, the method according to the invention carried out with the addition of so the e other well-known add polymerization inhibitors, such as, for example, phenothiazines, onomatology ether of hydroquinone, N-oxylene radicals, etc. Preferably they are added in the column head in the form of solutions (for example, dikalova acid contained in the acrylic) or melts. Of course, in the process according to the invention of them the amount consumed may be reduced.

The method according to the invention is suitable in particular when the distillation column is a disc column. This distillation column as an effective built-dividing elements, which contains almost exclusively mass-transfer plates. In this preferred according to the invention are such column trays, at least 80% of the number of mass-transfer plates which are net. Preferably used according to the invention the disc column as mass transfer plates contains only mesh plates. Below them, in this text shall be interpreted to mean plate in which the place of passage of the ascending gas or vapor phase (the term "gas" and "vapor" in this text are synonymous) are simple holes and/or slots.

Used mesh dish to share at the same time, as a rule, in two groups, namely a plate with a forced and without forced the nutrient fluid supply.

In General terms, the forced flow of the liquid in the mesh plates is obtained by equipping the mass transfer plates, at least one drain pipe (drain)through which the fluid regardless of the direction of the steam flow flowing from above to below the plates (flow). Horizontal fluid flow in the direction from the inflow to outflow is chosen in accordance with the underlying the way the task. The gas or vapor passes through the open cross sections of the plate.

If through the plate in the reverse flow serves fluid inflow and outflow plate placed on one side), we are talking about the plates return flows. In the case of plates radial flow fluid flows radially from the middle (inflow) to the runoff at the edge of the dish.

Under the plates with cross flow) understand that the fluid under consideration throughout the area of fluidity, flowing across the plate from inflow to outflow. Typically, plates with cross current are single-threaded. This means that the inflow and outflow placed on opposite sides of the plate. Although they can be also a two-line (or multi-threaded). In this case, the flow may, for example, be placed in the center, and each flow on opposite sides of the plate.

Thus, in the case of mesh plates force the flow of liquid is produced by about the nasienia mesh plates along with places of passage of the upward flow of the gas or vapor phase, at least one drain pipe (drain)through which the fluid regardless of the direction of the steam flow flowing from above to below the plates (flow). The fluid flows, for example, cross-current through the plate from at least one of the inflow to the at least one flow, and inlet and outlet pipes ensure the liquid valve and the required level of liquid in the dish. Often (especially in small diameter columns) sieve trays with forced fluid flow are single-threaded, that is, the inflow and outflow placed on opposite sides of the plate. Although they can be also a two-line (or multi-threaded). In this case, the flow may, for example, be placed in the center, and each flow on opposite sides of the plate. Thus, such a mesh plate should be called forced sieve plates. When using the “sprinkler” fluid dampening effect of the separation, it is impossible to prevent with the help of pipes for exhaust gases (as in the case of hydraulically sealed plates with cross-currents), which are through holes, this requires a minimum load on the vapor phase. Pairs of upward flow passes through the through hole and penetrates the layer of liquid held graduation is ruby.

Double-flow or failure sieve trays differ from force plates so that they do not contain the final segment. Due to the lack of final segments (drain pipes) the upward flow of gas disastrous mesh plates and downward flow of the liquid of the distillation column are passed through the same passages plates. In the case of a failure of the sieve plates, as in the case of compulsory mesh plates, to achieve the desired effect separation they require a minimum load on the vapor phase. If this load is significantly increased, the upward flow of gas and the downward reverse flow without exchange are past each other, resulting in the danger of drying plates.

This means that in the event of a failure of the sieve plates must be of the low velocity limit, so that the plate was supported by a certain layer of liquid, which would give the plate an opportunity to function. In normal workspace fluid failure sieve trays scapulae throughput through the openings of the plate to a plate, and between the plates passes a closed gas phase separated liquid phase. According to the invention preferred sieve plates used distillation columns are disastrous sieve trays.

Preferred for the implementation of the management method according to the invention of distillation columns, containing sieve trays, columns are described in DE-A 10230219. In addition, for implementing the method according to the invention used as a distillation column, containing sieve trays is described in DE-A 10156988 or in EP-A 1029573.

Hydraulically sealed plates with transverse current is different from the mesh plates so that when they shut down the columns may not work at idle, except for a tiny hole idling (their cross-section, usually, more than 200 times smaller than the total cross-section of the passageway areas)that the principles of expediency contains each plate with transverse current.

Thus, even at low loads columns hydraulically sealed plates with transverse current contain the accumulated liquid (the phlegm and/or feed liquid) and not in danger of drying out. This is because in the case of places of passage hydraulically sealed plates with transverse current, unlike mesh plates, it is not about the holes for the exhaust gases. On the contrary, each passage ends with a pipe for exhaust gases, which prevents drying out. Above the pipe is caused to swivel caps (caps), immersed in the accumulated fluid plates. Often the edges of the caps have slots or teeth (i.e. working slots). Colpack is change the direction of the current upward flow of gas, which then flows parallel to the plate, that is, across the columns, the accumulated liquid.

Bubbles of steam which rise from neighboring caps, which are typically located above the plate and equidistant from each other, the accumulated liquid form flowing layer.

The exhaust pipe or segments, which, as a rule, alternately to the right or left face of the plate, adjust using the valve - liquid level mass-transfer plates and serve the liquid in the lower plate. For hydraulic sealing important is the fact that the exhaust pipe or the segments of the upper plate immersed in the stored liquid under her plate. Preferably do not use any hydraulic inlet valves. Adjustable caps allow adjustment to the conditions of flow and alignment of the height of the dive when the non-uniformity of manufacture, so that all caps plates hairout the same.

Depending on the shape and location of single-threaded caps hydraulically sealed plates with transverse current is divided into plates with round caps (place of passage, a pipe for gas outlet and cap are round), tunnel plate (place of passage, a pipe for gas outlet and cap are rectangular, the caps are arranged one behind the other, moreover, the longest edge is parallel to the direction of cross-flow of liquid and plates of Thormann (place of passage, pipe for gas outlet and cap are rectangular, the caps are arranged one behind the other, with the longest edge is perpendicular to the transverse direction of a liquid).

Under the valve in this context, see plates with transverse current, which contain holes, equipped with disc, ballast, or lifting (floating) valve restrictors, which fit the size of the access hole under the corresponding load of the column. The upward flow of gas away, it flows parallel to the plate in the accumulated phlegm and forms a flowing layer. Equipped with valves exhaust pipes direct the phlegm from plate to plate. They are often double-flow, although there may be three - and multi-threaded (for example, to cosmipolitan).

Of course, the method according to the invention are also carried out when the distillation column is a disc column, at least 80% of the number of mass-transfer plates which are hydraulically sealed plates with transverse current. Naturally, all plates can be hydraulically sealed plates with transverse current. Often for implementing the method according to the invention is used, however, column trays, plates in which the upper part of the distillation column, not only is jut a valve plates.

Preferred hydraulically sealed plates with transverse current are plates of Tormann, especially in those cases where, in the upper part of the distillation columns used valve plates.

Necessary for implementing the method according to the invention provide heat supply, for example, by using internal and/or external heat exchanger of conventional design and/or heating double wall. Often use external circulation evaporators with natural or forced circulation.

According to the invention it is possible to use several in series or parallel connected evaporators.

Supply of thermal energy in the method according to the invention is preferably carried out using an external evaporator with forced circulation and particularly preferably by means of an external pressure reducer evaporator with forced circulation, described for example in DE-a 10332758 and in EP-A 854129.

Reducing evaporation apparatus with forced circulation in contrast to the evaporator with forced circulation is separated from the distillation column in a throttling device. Continuously take part of the liquid contents of the distillation column under pressure Pxand the introduction of the circulation pump into the tributaries of the tubular evaporator (shell and tube heat exchanger). Internal pipes of the tubular evaporator the heat transfer medium flows, for example district heating steam (typically under pressure of water vapor), the temperature above the liquid environment of the distillation column. Passing through inlet and outlet tubes of the tubular evaporator discharged from the distillation column a liquid by indirect heat exchange heated to a temperature Tythat is higher than the temperature of liquid of the distillation column.

Throttling device divides the tubular evaporator apparatus and distillation column and allows by varying the capacity of the circulation pump to install in excess of Rxinitial pressure throttling device Pythat is higher than the corresponding temperature Ty'boiling pressure Py'discharged from the distillation column of liquid. The above method is able to suppress the boiling liquid fraction, pumped from the distillation column in pipe tubular evaporator. The fluid pumped from the distillation column in pipe tubular evaporator, significantly overheat compared to the existing in the liquid environment of the distillation column pressure Pxthus the process of boiling is moved toward passage dressaire the feeder (in other words, the contents of the tubes of the tubular evaporator is single-phase, tubular evaporating device operates only as a superheater). The release of the hot fluid through the throttling device in the distillation column can be made directly in the liquid contents of the distillation column (rectifying column bottom). Under such conditions, the temperature of the liquid contents of the cube distillation columns typically corresponds to the boiling temperature of Txat a pressure Pxon bottom of the liquid.

Typically, the release of the hot fluid through the throttling device in the distillation column above the liquid level of the cube of the distillation column. Under such conditions, the temperature of the liquid contents of the cube of the distillation column is typically below the boiling temperature Txwhen the pressure Pxon bottom of the liquid. Important is the fact that the effect of boiling outside the distillation column tube evaporator first occurs in a distillation column, that is, outside the circulation evaporator. When this throttling can, for example, to carry out mechanically (jumpers, valves) and/or hydrostatically (using the corresponding high columns over the place of the passage of the hot fluid is tis).

The flow of the liquid in the distillation column in the method according to the invention can be implemented as columns in the cube, and in its lower or middle part. The middle of this determined using the number of theoretical stages of separation distillation columns. Where (bottom-up) is half of theoretical stages of separation, called the middle. The middle part is directly under it, and the lower part begins where it ends up in the middle, namely, above the place of the distillation column, where it ends 1/3 of theoretical stages of separation (looking upward).

Preferably the method according to the invention is carried out at reduced pressure. According to the invention, the preferred pressure at the column head ≤500 mbar, particularly preferably from 10 to 500 mbar, frequently from 10 to 200 mbar, in particular from 10 to 150 mbar. The pressure loss in the whole volume of the distillation column in the process according to the invention is preferably from 300 to 100, or from 250 to 150 mbar. The temperature in the cube distillation column in the process according to the invention is from 100 to 230°C., preferably from 120 to 210°C., or from 160 to 200°C.

Of course, the distillation column as built-dividing elements may also contain fillers or/and the nozzles. The nozzle layer using, for example, rings, spirals, saddles, rings process, Intesa or Palla, saddles Barrel or Intalox, top-Pak or nozzles in the form of wire meshes. Of course, the distillation column may also contain all described in this application is possible built-in elements of a column in a mixed form.

As mentioned above, all inhibitors of polymerization in the process according to the invention, generally load in the head of the column. Additionally you can download them in a cube columns or add to be the separation that contains acrylic acid liquid. As typical representatives of such polymerization inhibitors should again be called phenothiazines, 4-methoxyphenol and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl. Depending on the content of the liquid phase in acrylic acid, typically use up to several hundred weight. ppm of polymerization inhibitors.

It is also known (see, for example, DE-A 10256147, DE-A 19501325 and Chem. Eng. Technol. 21 (1998) 10, S.829-836)for additional inhibition of polymerization through the distillation column during the distillation miss gas containing molecular oxygen (e.g. air or depleted air) (see also DE-a 10238145)that can be implemented according to this invention.

Place of unloading In the mass flow of the ri implementation of the method according to the invention can be in the head of the column, and as a side tip can be placed under the head of the column (for example, in the upper or middle part of a distillation column). The latter is preferred according to the invention.

Preferably place the side discharge is at least 0.2 to 5, usually 0.5-3 or 0.6-2 theoretical separation stages below the head of the column.

Subject to separation fluid may contain acrylic acid in a more or less pure form or in solution.

The solvent may be used as water and an organic solvent. Specific type of solvent according to the invention is not critical. Preferably it is water or an organic solvent, if necessary, containing a small amount of water.

The content of acrylic acid in the liquid can be ≥2 wt.%, or ≥5 wt.%, or ≥10 wt.%, or ≥20 wt.%, or ≥40 wt.%, or ≥60 wt.%, or ≥80 wt.%, or ≥90 wt.%, or ≥95 wt.%, or ≥99 wt.%.

In particular, the method according to the invention can be applied in the case of a distillation method for the allocation of acrylic acid from a mixture, as a main component containing acrylic acid (usually from 10 to 35 wt.%, often from 15 to 30 wt.%, in terms of the weight of liquid) and (preferably inert) hydro is one of the organic liquid from 50-80 wt.% with a higher boiling point, than acrylic acid, as well as additional components (e.g., lower) aldehydes (for example, up to 10,000 or 5,000 hours/million by weight) in the liquid prior to its distillation process according to the invention can be added primary amine and/or its salt, as, for example, described in EP-A 717029), as, for example, is carried out in the framework of the allocation of acrylic acid from the reaction gas mixture resulting from the oxidation in the gas phase, according to the methods described in DE-A 4436243, DE-PS 2136396 EP-A 925272 and DE-A or DE-A 10336386 (unloaded mass flow contains as a rule, do not over 99.5 wt.%, often not more than 99 wt.%, often no more than 98,5% wt. acrylic acid). In other words, in the case when the mixture as a main component containing acrylic acid and an inert hydrophobic organic liquid with a higher boiling point than acrylic acid, as well as additional components of the lower aldehydes, for implementing the method according to the invention receives, for example, from a mixture of reactive gases by catalytic oxidation in the gas phase as the flow of liquid in countercurrent absorption with subsequent desorption by cleaning according to DE-PS 213639, EP-A 925272 or DE-A 4308087 or DE-A 10336386 or as a flow of fluid, followed by distillation according to DE-A 4436243. Under inert hydrophobic org the organic liquid with high boiling point means such fluid, the boiling point of which at normal pressure (1 bar) higher than the temperature of acrylic acid and in which the solubility (wt.%, in recalculation on weight of solution) of the products of the oligomerization and/or polymerization of acrylic acid at 25°C and 1 ATM is lower than in pure acrylic acid.

In particular, they are such organic liquids with high boiling point, which at least 70 wt.% consist of such molecules that do not contain polar groups and, thus, not capable of forming hydrogen bridges. In a narrow sense, it covers the high-boiling organic absorption fluid recommended in DE-PS 2136396, DE-A 4308087, DE-A 4436243.

They are primarily liquid, the boiling point of which at normal pressure is above 160°C. as examples should be called the middle oil fraction of the paraffin distillation, diphenyl ether, diphenyl, or mixtures of the above liquids, for example, a mixture of 70-75 wt.% diphenyl ether and 25-30 wt.% of diphenyl (also called devil). Preferred high-boiling hydrophobic organic absorption liquid is a mixture of 70-75 wt.% diphenyl ether and 25-30 wt.% of diphenyl, and depending on these components of 0.1 to 42.5 wt.% o-dimethylphthalate.

Thus, the method according to the invention can b shall be applied for liquids W, which contain such components (quantitative indicators relate to the total number):

devilfrom 50 to 75 wt.%,
dimethylphthalatefrom 10 to 25 wt.%,
dikalova acidfrom 0.2 to 3 wt.%,
acrylic acidfrom 15 to 35 wt.%, often from 15 to 25 wt.%,
waterfrom 0.07 to 0.2 wt.%,
acetic acidfrom 0.01 to 0.2 wt.%,
formic acidfrom 0.001 to 0.02 wt.%,
propionic acidfrom 0.001 to 0.02 wt.%,
phenothiazinesfrom 0.01 to 0.1 wt.%,
phthalic anhydridefrom 0.1 to 1 wt.%,
benzoic acidfrom 0.2 to 2 wt.%,
the anhydride of maleic acidfrom 0.1 to 2 wt.%,
benzaldehydeabout the 0.1 to 1 wt.% and
furfuralfrom 0.01 to 0.05 wt.%.

The distillation unit may be of known form and may include conventional built-in items. As built-in elements, as a rule, use all the known elements, such as plates, gaskets and/or nozzles. Under the plates mean the cap, mesh, valve trays, plates of Tormann and/or double-flow plates, under layers of nozzles rings, spirals, saddles, rings process, Intesa or Palla, saddles Barrel or Intalox, top-Pak or nozzles in the form of wire meshes. I prefer double-flow plates.

Typically, distillation node contains from 10 to 25 theoretical plates. The distillation is usually carried out at reduced pressure, preferably at a pressure in the head of the column from 70 to 140 mbar. The pressure in the cube is determined by the pressure head of the column, the number and form of built-in elements of a column, and dynamic requirements of rectification and is preferably from 300 to 400 mbar.

When using double-flow plates as built-in elements, the diameter of the holes of the plates over the place of the flow is generally from 5 to 25 mm, preferably from 10 to 20 mm. Diameter holes of the plates below where the flow is generally from 5 to 80 mm, preferably from 25 to 50 mm and particularly preferably is a cascade, as described, for example, in German patent application DE-A 10156988. The distance between the plates (usually plates equidistant from each other) is from 300 to 700 mm, preferably from 350 to 400 mm, and particularly preferably 380 mm

Preferably the upper part of the distillation node simultaneously heated. In the case of distillation node containing n theoretical plates, it concerns the area over the n/2-th theoretical plate. The temperature of the associated heating is chosen so that on the outer wall of the column could not condense acrylic acid. Preferably the temperature at 5-10°C. above the boiling point of acrylic acid at the pressure existing in the area in question rectifying element.

Rectifying node is usually made of austenitic steel, preferably of a material 1.4571 (DIN EN 10020).

The flow in the rectifying element is carried out, as a rule, in its lower zone, preferably 2-5 theoretical plates (stages of separation) above the rectifying column bottom. The temperature of the inflow is usually 150°C.

Provide heat supply using internal and/or external heat exchanger (cooled again is water vapor) of conventional design and/or heating double wall. Preferably the external circulation evaporators with natural or forced circulation. Especially preferably the external circulation evaporators with forced circulation. It is possible to use several in series or parallel connected evaporators. Preferably use from 2 to 4 connected in parallel evaporators. The temperature of the cube rectifying element is usually from 170 to 210°C, preferably from 180 to 200°C. the high-boiling fraction is condensed in Cuba distillation column, contains, as a rule, the following components (quantitative indicators relate to the total number):

devilfrom 70 to 85 wt.%,
dimethylphthalatefrom 10 to 25 wt.%,
dikalova acidfrom 0.5 to 5 wt.%,
acrylic acidfrom 0.2 to 2 wt.%,
phenothiazinesfrom 0.01 to 0.1 wt.%,
phthalic anhydridefrom 0.1 to 1 wt.%,
benzoic acidfrom 0.2 to 2 wt.%,
the anhydride of maleic acidfrom 0.1 to 2 wt.%,
benzaldehydefrom 0.1 to 0.5 wt.% and
furfuralfrom 0.01 to 0.05 wt.%.

Leaving the rectifying element cubic liquid containing condensed high-boiling absorbent, partially discharged through the gateway, preferably from 75 to 90 wt.%, in terms of flow in the rectifying junction, and partially through the heat exchanger back to the cubic part of the distillation column.

Above the place of the flow through the lateral discharge of the distillation column unload crude acrylic acid, preferably 8 to 20, theoretical plates above the cube column. Unloading crude acrylic acid is carried out in the usual way, which is not subject to any restrictions. Preferably unloading carried out by means of the arresting plates, and delayed the whole cycle recirculation, one part of phlegmy is discharged, and the other as the return use below catching dish or on a plate with the possibility of output, preferably above the catching plate with the possibility of withdrawal. Unloaded crude acrylic acid, as a rule, the soda is incorporated the following components (quantitative indicators relate to the total number):

acrylic acidfrom 98 to 99.9 wt.%,
acetic acidfrom 0.05 to 0.3 wt.%,
waterfrom 0.001 to 0.05 wt.%,
formic acidfrom 0.001 to 0.005 wt.%,
propionic acidfrom 0.01 to 0.05 wt.%,
furfuralfrom 0.01 to 0.05 wt.%,
allylacetatefrom 0.001 to 0.01 wt.%,
benzaldehydefrom 0.001 to 0.01 wt.%,
the anhydride of maleic acidfrom 0.002 to 0.02 wt.%,
dikalova acidfrom 0.01 to 0.05 wt.% and
phenothiazinesfrom 0.01 to 0.05 wt.%.

Unloaded crude acrylic acid cooled cold raw (prior) acrylic acid and/or using heat as the refrigerant used, for example, surface water). It is possible to also use several them in series or parallel connected heat exchangers. In heat exchangers known in the art, the crude acrylic acid is cooled preferably 40-70°C.

The crude acrylic acid, preferably from 10 to 25 wt.%, in terms of flow in the distillation column and discharged through the gateway, and part of it is used as a solvent for polymerization inhibitor.

Cooling highlighted in the head of the distillation column flow low-boiling components can be done indirectly, for example, by means of heat exchangers (as a refrigerant is used, for example, surface water), known to specialists, or directly, for example, by direct cooling. Preferably it is carried out by direct cooling. To this end the condensed low-boiling fraction is cooled by a suitable heat exchanger, and the cooled liquid is sprayed over the place of unloading. This dispersion can be performed in an appropriate apparatus or in the distillation site. When spraying in a distillation node in place of unloading of the low-boiling fraction is a catching plate. Using the built-in elements, which improve the mixing of the cooled low-boiling fraction, it is possible to increase the effect of direct cooling. For this purpose, use all the usual built-in items, such as plates, gaskets and/or nozzles. Under what Uralkali mean the cap, net, valve trays, plates of Tormann and/or double-flow plates, under the nozzles - rings, spirals, saddles, rings process, Intesa or Palla, saddles Barrel or Intalox, top-Pak or nozzles in the form of wire meshes. I prefer double-flow plates. As a rule, enough for 2 to 5 theoretical plates. These plates were not taken into account when specifying the number of theoretical plates of the rectifying element. Direct condensation of the low-boiling fraction can be carried out in several stages, with a decreasing bottom-up temperature. Allocated in the head of the distillation column a stream of low-boiling fraction mainly contains the following components (quantitative indicators relate to the total number):

acrylic acidfrom 90 to 99 wt.%,
acetic acidfrom 0.5 to 3 wt.%,
waterfrom 0.5 to 2 wt.%,
phenothiazinesfrom 0.02 to 0.1 wt.%,
allylacetatefrom 0.01 to 0.1 wt.%,
furfuralfrom 0.002 to 0.01 wt.%,
propionic acidfrom 0.01 to 0.05 wt.%,
formic acidfrom 0.1 to 1 wt.% and
acroleinfrom 0.001 to 0.002 wt.%.

Part paged as a low-boiling fraction of liquid, preferably from 30 to 50 wt.%, in terms of flow in a distillation column is used as the phlegm, and the remaining amount of low-boiling fraction, preferably from 0.5 to 2 wt.%, in terms of flow in the distillation column and discharged through the gateway. According to the invention of the distillation column is used preferably in such a way that the content diacrylates acid in the phlegm, in terms of its weight is at least 550 hours/million by weight. Preferably the content of the above diacrylates acid is 1000 hours/million by weight, or even 1500 hours/million by weight or more.

Exhaust gas rectifying site contains typically the following components (quantitative indicators relate to the total number):

nitrogenfrom 70 to 80 wt.%,
oxygenfrom 15 to 25 wt.%, often from 15 to 21 wt.%,
acrylic is Aya acid from 1 to 5 wt.%,
acetic acidfrom 0.05 to 0.5 wt.%,
waterfrom 0.2 to 0.8 wt.%,
acroleinfrom 0.001 to 0.005 wt.%,
formic acidfrom 0.02 to 0.2 wt.%,
allylacetatefrom 0.001 to 0.005 wt.% and
oxides of carbonfrom 0.02 to 0.06 wt.%.

The exhaust gas is burned together with other commercial wastes for disposal.

As inhibitors of polymerization in the distillation column can be used ALKYLPHENOLS such as o-, m - or p-cresol (METHYLPHENOL), 2-tert-butyl-4-METHYLPHENOL, 6-tert-butyl-2,4-dimethylphenol, 2,6-di-tert-butyl-4-methyl-phenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 4-tert-butyl-2,6-dimethylphenol or 2,2'-methylene-bis(6-tert-butyl-4-METHYLPHENOL), hydroxyphenol, such as hydroquinone, 2-methylhydroquinone, 2,5-di-tert-butylhydroquinone, brenzcatechine (1,2-dihydroxybenzene) or benzoquinone, aminophenols, such as, for example, para-aminophenol, nitrosophenol, such as, for example, para-nitrosophenol, alkoxyphenyl, for example 2-methox the phenol (guaiacol, onomatology ether brincadeira), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (onomatology ether of hydroquinone), mono - or di-tert-butyl-4-methoxy-phenol, Tocopherols, such as α-tocopherol, and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzophenone (2,2-dimethyl-7-hydroxycoumarin), N-oxely, such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 2,2,6,6-tetramethylpiperidine-N-oxyl, postit 4,4',4"-Tris(2,2,6,6-tetramethylpiperidine-N-oxyl) or 3-oxo-of 2.2.5.5-tetramethylpyrrolidine-N-oxyl, aromatic amines or phenyldiamine, such as, for example, N,N-diphenylamine, N-nitrosodiphenylamine, N,N'-dialkyl-para-phenylenediamine, and the alkyl radicals may be the same or different and independently from each contain from 1 to 4 carbon atoms and can be linear or branched, hydroxylamine, such as, for example, N,N-diethylhydroxylamine, phosphorus-containing compounds, for example triphenylphosphine, triphenylphosphite, phosphonoacetate acid or triethylphosphite, sulfur containing compounds, such as diphenylsulfide or phenothiazines, if necessary, in combination with metal salts, for example chlorides, dithiocarbamate, sulfates, salicylates or acetates of copper, manganese, cerium, Nickel or chromium. Of course, there can be used the same mixture of the above polymerization inhibitors.

Preferably in a distillation node as the polymerization inhibitor used phenothiazines or other polymerization inhibitor that exhibits the same activity as the phenothiazines.

The polymerization inhibitor is preferably in the form of a solution in a relatively pure acrylic acid, particularly preferably in the form of a solution in pure acrylic acid, uploaded in place of the side unloading, add in the condensed low-boiling the phlegm. The total concentration of aldehyde compounds used for the stabilization of acrylic acid is less than 500 hours/million by weight. The concentration of the stabilizer (inhibitor) in the stabilization solution depends on the stabilizer and solvent used. The optimum concentration of stabilizer in the stabilization solution can be determined by tests on the solubility, in the case of fenotiazina as stabilizer and acrylic acid as solvent, it ranges from 0.1 to 2 wt.%, preferably from 1.2 to 1.7 wt.%. The stabilizer is metered in such a way that the concentration of the stabilizer in the unloaded pure acrylic acid is from 50 to 500 hours/million by weight, preferably from 150 to 350 hours/million by weight.

Form of solid polymerization inhibitors, which are served in a vessel containing a solution of the stabilizers, the can is to be in principle any. For example, can be used flakes, granules or tablets. Because of the relatively low content of dust particles and profitable ratio flowability give preference to tablets. Solid inhibitors of polymerization with the help of screw conveyors can be enjoyed in the solution of the stabilizers from the repository.

For further support stabilization (inhibition of polymerization) can be used, a gas containing oxygen, for example air, or a mixture of air and nitrogen (lean air), particularly preferably the air.

This oxygen-containing gas preferably serves in the cubic area of the distillation column and/or in circulation evaporating device.

The take air directly from the atmosphere, preferably in one or more places of sampling.

According to the invention used in this manner the air before applying it preferably filtered, as described above in connection with partial oxidation.

Especially preferably use the air, the salt content in which, for example, organic and inorganic chlorides, in particular alkali metal chlorides, is less than 10 hours/million by weight.

Oxygen-containing gas is metered in such a way that the partial pressure of oxygen in the head of the distillation node is at least 0.5 mbar, prepost is positive at least 2 mbar.

Additionally, the rectifying element can be added surfactant, as described, for example, in DE-A 19810962.

The method according to the invention may also include a distillation purification of the mixture of acrylic acid containing from 95 to 99.5 or 99.8 wt.% acrylic acid (this is advantageous in particular when it contains ≥2, or ≥5 h/million by weight, or ≥10 parts/million by weight, or ≥ 20 hours/million by weight, or ≥50 PM/million by weight aldehydes, such as acrolein, furfural, benzaldehyde, etc.; in particular when their boiling point at normal pressure (1 ATM) below the boiling point of acrylic acid). Before rectification they can be treated with amines such as hydrazine or hydrazine derivatives (such as aminoguanidinium), as described, for example, in DE-A 10219592, EP-A 713854 and EP-A 270999.

Examples and comparative example

Prepare 4 samples of 0.5 ml each (distillation, then freeze), the content of acrylic acid in which is and 99.8 wt.%.

Then by adding mostly pure acrylic acid in each of the 4 samples establish the following content diacrylates acid:

sample 1:≤5 parts/million by weight;
sample 2: 500 parts/million by weight;
sample 3:1000 weight. hours/million by weight;
sample 4:1500 parts/million by weight;
sample 5:10000 parts/million by weight;
sample 6:15000 parts/million by weight.

Samples of acrylic acid did not contain another inhibitor of polymerization. In addition to all 4 samples were added such an amount of benzaldehyde that benzaldehyde is 500 hours/million by weight.

In an atmosphere of air each sample is transferred into a 1.8 ml glass test tube. Then the test tube at 120°C is placed in a chamber dryer air circulation and rotate to ensure complete mixing. After that, visually estimate the time T required for complete polymerization of the corresponding samples.

The experience is repeated three times, the indicators calculated arithmetically. The average results of time T for each sample as follows:

sample 1:128 min;
sample 2:136 min;
sample 3:143 min;
sample 4:153 min;
sample 5:175 min;
sample 6:195 minutes

Considering the above, there are numerous changes and deviations from the present invention. In addition, it can be assumed that the invention within formula can be implemented in any other way than described here.

Comparative example

As described in DE-A 10336386 the final mixture of gases undergo a two-stage heterogeneously catalytic gazofaznom oxidation of propylene to acrylic acid, the absorption of acrylic acid in a mixture of defile and dimethylphthalate followed by distillation of low-boiling components with the formation of absorbate And*having the following composition:

is 18.40 wt.%acrylic acid
0,0328 wt.%acetic acid
0,0197 wt.%water
61,77 wt.%defile
15,48 wt.%dimethylphthalate
0,0045 wt.% propionic acid
0,0123 wt.%furfural
0,0007 wt.%allylacetate
0,165 wt.%benzaldehyde
0,619 wt.%maleic anhydride
0,267 wt.%benzoic acid
3.14 wt.%diacrylates acid
0,0341 wt.%fenotiazina and
0,0003 wt.%molecular oxygen.

With the mission of the Department is contained in absorbate And* acrylic acid in the form of crude acrylic acid, absorbed And* subjected to distillation in a distillation column.

Distillation column represents a tray type column, which as a separation element contains only a two-line plate. The internal diameter of the column is 4600 mm, and the height of the column 32790 mm. In total column contains 46 twin plates.

The bottom two plate is located on the height of the column 9586 mm double-flow plates with 1 to 8 form the first series tarel is to, located equidistant at a distance of 400 mm above each other. The number of the exhaust holes on one double-flow plate for plates 1 and 2 is 1506 when the hole diameter is 50 mm

The number of outlets for plates 3 and 4 is 1440 when the hole diameter is 50 mm for each outlet, and the number of exhaust holes for the plates 7 and 8 is 1460 when the hole diameter is 50 mm for each outlet. The mutual position of the outlet strictly follows a triangular distribution.

The free space between the plates 8 (bottom) and 9 (bottom) is 1000 mm double-flow plate 9 is a first plate of the second series also located equidistant at a distance of 400 mm above each other and a two-line plates. In total, this second series contains 38 twin plates.

The number of the outlet plate 9 is 1002 when the hole diameter is 50 mm, the Plate 10 includes 4842 exhaust holes with a hole diameter of 25 mm, the Number of the exhaust holes of the plates 11 and 12 is 4284 for each plate with a diameter of 25 mm, the Number of exhaust holes for the plate 13 is 4026 with a diameter of 25 mm, the Number of the exhaust holes of the plates 14 to 28 is 12870 for each plate with a diameter of 14 mm Plates from 29 to 31 and out 13632 outlet with a diameter of 14 mm. The plate 32 has 14361 outlet with a diameter of 14 mm Plates 33 to 39 have 14365 exhaust holes with a diameter of 14 mm Plate 40 constituting the exhaust plate (see below), has 14362 outlet with a diameter of 14 mm Plates from 41 to 46 have 14577 exhaust holes for each plate with a diameter of 14 mm

Absorbed And*, heated to 152.5°C, served with speed 193580 kg/h in the distillation column through 6 nozzles reflective plates (similar to those disclosed in EP-A 1345881)installed along the perimeter of the column and form a place of submission of Z, on a two-line plate 8 from below.

Below the bottom of a twin plate, but above the liquid level in the distillation column serves the air (water content = 0,4369 wt.%, temperature = 20°C) speed 1091 kg/hour, a Pressure in the upper part of the column is 107 mbar. The pressure under the bottom plate and above the liquid surface is 278 mbar.

The flow of energy carried out by means of forced circulation heat exchanger. To do this, using a centrifugal pump cubic liquid in a distillation column under the lower separating plate, with a speed 1155440 kg/h is withdrawn from the distillation column (from 188 to 193°C). This fluid flow return with speed 160043 kg/h as the absorbent in the absorption process.

The remaining 995397 kg/h return in re tification the column by a pump through a heat exchanger (temperature 197,2°C). The recirculation is carried out under the bottom separation plate, but above the liquid level in the distillation column. This pump has closed the impeller. As the sealing liquid, a mixture of 50 wt.% glycol and 50 wt.% water. The pump is a type SVN 12×22 manufacturer Ruhrpumpen.

The heat exchanger contains 2911 pipes for heat transfer. The internal diameter of this pipe is uniformly 20 mm with wall thickness of 2 mm and pipe length 5000 mm, an Inner diameter of the heat exchanger is 2540 mm, and the thickness of its walls is 30 mm as a carrier serves 22,000 kg/h of saturated steam (226°C, 29 bar). The steam condensate produced in the heat exchanger, is removed at a temperature of 206°C. using 6 guide elements (ratio of the free cross-section to the closed cross-section is in each case 1:126) the flux of water vapor in the regenerator spend around the tubes of the exchanger.

Waste liquid has the following composition:

0,976 wt.%acrylic acid
of 0.0001 wt.%acetic acid
74,72 wt.%defile
18,72 wt.% dimethylphthalate
of 0.0001 wt.%propionic acid
0.01 wt.%furfural
0,199 wt.%benzaldehyde
0,747 wt.%maleic anhydride
0,324 wt.%benzoic acid
4,20 wt.%diacrylates acid and
0,0545 wt.%Fenotiazina.

From the top of the distillation column divert the flow of secondary vapor of the following composition (73991 kg/h, 107 mbar, to 78.7°C):

97,31 wt.%acrylic acid
0,711 wt.%acetic acid
0,416 wt.%Water
is 0.023 wt.%propionic acid
0,0067 wt.%Furfural
0,0124 wt.%allylacetate
of 0.0005 wt.%benzaldehyde
0,0003 wt.%maleic anhydride and
0,3788 wt.%molecular oxygen.

This stream is subjected to two-stage condensation in two straight refrigerators) with the formation of the recirculating liquid. As the coolant used was obtained in the previous stages of the condensate, which complement solution fenotiazina in the crude acrylic acid withdrawn from the distillation column.

The coolant used in the first stage of condensation (34,4°C, 961965 kg/h), has the following composition:

98,89 wt.%acrylic acid
0,634 wt.%acetic acid
0,325 wt.%water
0,0238 wt.%propionic acid
0,0080 wt.%furfural
0,0112 wt.%allylacetate
0,0008 wt.%benzaldehyde
0,0007 wt.%maleic anhydride
0,0100 wt.%diacrylates acid
0,0500 wt.%fenotiazina and
0,0003 wt.%Molecular oxygen.

Over two-flow plate 46 (bottom) in a distillation column returns with a temperature of 50.9°C (84890 kg/h) liquid discharged from the effluent, panchamuga on the first stage of kodenshi. Recirculated liquid has the following components:

98,89 wt.%acrylic acid
0,636 wt.%acetic acid
0,325 wt.%water
0,0238 wt.%propionic acid
0,0079 wt.%furfural
0,0113 wt.%allylacetate
0,0008 wt.%benzaldehyde
0,0006 wt.% maleic anhydride
0.01 wt.%diacrylates acid
0,046 wt.%fenotiazina and
0,0003 wt.%molecular oxygen.

Kladusa liquid (18,7°C, 55400 kg/h)used in the second stage of condensation, has the following components:

97,75 wt.%acrylic acid
0,679 wt.%acetic acid
1,135 wt.%water
of 0.0001 wt.%acrolein
0,0232 wt.%propionic acid
0,0067 wt.%furfural
0,0161 wt.%allylacetate
0,0006 wt.%benzaldehyde
of 0.0005 wt.%maleic anhydride
0,0148 wt.%diacrylates sour is you
0,0291 wt.%fenotiazina and
0,0034 wt.%molecular oxygen.

Of the exhaust from the second stage condensing fluid return flow speeds 3224 kg/h (24°C) at the stage of absorption.

Two plate 40 in a distillation column made in the form of a plate with a side outlet. She is in the middle of the tub, which is given to gathering in her fluid. This liquid is withdrawn from the plate 40 columns, is a crude acrylic acid (to 85.2°C, 33560 kg/h).

This stream of acrylic acid is cooled in two stages (cooling water cooling cooling brine) to a temperature of 25.6°C.

Part of the flow of the cooled crude acrylic acid with speed 30311 kg/h served in the store. To the residual flow of the cooled crude acrylic acid in a mixer add the phenothiazines and the obtained solution containing 1.4 wt.% fenotiazina, served in the streams fed to the two-stage condensation.

Crude acrylic acid has the structure:

99,771 wt.%acrylic acid
is 0.102 wt.%acetic acid
0,0094 wt.%water
0,0025 wt.%propionic acid
0,0245 wt.%furfural
0,0025 wt.%allylacetate
0,0068 wt.%benzaldehyde
0,0069 wt.%maleic anhydride
0,0250 wt.%diacrylates acid
0,0400 wt.%fenotiazina and
0,0094 wt.%glyoxal.

Absorbed And* serves in a distillation column on a two-line plate 8 (bottom).

Exhaust with twin plates 40 (bottom) of the crude acrylic acid contains 99,711 wt.% acrylic acid.

Recirculated liquid flowing in the distillation column with a two-line plate 14 (bottom) on a two-line plate 13 (bottom), contains 127 ppm-wt. diacrylates acid.

After the age of 30 days on the surface of the double-flow plate 13 is formed a clearly visible layer of polymerizate.

Example

Proceed as in the comparative example. Additionally, the recirculated fluid with a temperature of 50.9°C and speed 84890 kg/h add extract acidic water in the distillation column above the double-flow plates 46 (bottom), heated to 50.9°C, with a speed 782,4 kg/h (see p.18/19 and 24 from DE-A 10336386).

Extract the acidic water has the following composition:

77,45 wt.%Water
3,55 wt.%formic acid
4,925 wt.%acetic acid
2,507 wt.%maleic acid
0,0570 wt.%benzoic acid
0,0012 wt.%propionic acid and
4,094 wt.%diacrylates acid,

and

0,0054 wt.%molecular oxygen
0,0300 wt.%defile
0,420 wt.%dimethylphthalate
0,0048 wt.%furfural
0,0028 wt.%allylacetate
0,0301 wt.% benzaldehyde and
6,875 wt.%acrylic acid.

Thanks to the additional supply of the extract acidic water in the upper part of the distillation column content diacrylates acid in the recycled liquid flowing down from the double-flow plates 14 (bottom) on a two-line plate 13 (bottom), increased to 643 ppm-mass.

After the age of 30 days on the surface of the double-flow plate 13 does not observe the formation of polymerizate.

1. The method of distillation separation of a liquid containing acrylic acid, in which the liquid containing acrylic acid, is fed through a download location to a distillation column, and the download location of the distillation column in place of unloading unload the mass flow, the content of acrylic acid in which, calculated on the weight of the mass flow rate of ≥90 wt.% and is higher than the corresponding content of acrylic acid in the liquid in wt.%, characterized in that within the zone of the distillation column, which is at least two theoretical stages of separation above content diacrylates acid in the phlegm in terms of weight phlegmy, at least in partial areas is ≥550 hours/million by weight, and the establishment of the specified content is diacrylates acid in the phlegm is carried out by a liquid, contains acrylic acid, at least one non-acrylic acid acid Bronsted relevant pKa≤16, or, at least, one Bronsted relevant b≤10, and/or additions to the phlegm at least one compound from the group comprising non-acrylic acid acid Bronsted relevant pKa≤16, the base Bronsted relevant b≤10, diacrylate acid and acrylic acid containing diacrylate acid.

2. The method according to claim 1, characterized in that the content diacrylates acid in the phlegm is ≥650 hours/million by weight.

3. The method according to claim 1, characterized in that the content diacrylates acid in the phlegm is ≥1000 hours/million by weight.

4. The method according to claim 1, characterized in that the specified content diacrylates acid has a total area of the distillation column, are at least two theoretical stages of separation above the location of the download.

5. The method according to claim 1, characterized in that the specified content diacrylates acid in the phlegm has a total area of the distillation column located on at least four theoretical stages of separation above the location of the download.

6. The method according to claim 1, characterized in that the place of unloading is in a distillation column, at least two theoretical stages above zag is narrow.

7. The method according to claim 1, characterized in that you want to split the liquid contains acid Bronsted with a lower boiling point than acrylic acid with PKand≤16.

8. The method according to claim 1, characterized in that the phlegm add diacrylate acid in pure form and/or acrylic acid containing diacrylate acid.

9. The method according to claim 1, characterized in that the distillation column as built effective separation of elements contains at least one mesh plate.

10. The method according to claim 1, characterized in that the distillation column as built effective separation of elements includes at least one hydraulically reinforced plate.

11. The method according to one of claims 1 to 10, characterized in that are necessary to implement the process of thermal energy are served using an external pressure reducer evaporator with forced circulation.

12. The method according to claim 11, characterized in that the reducing evaporator with forced circulation using a tubular evaporating device.

13. The method according to one of claims 1 to 10, characterized in that the liquid is a mixture which contains from 10 to 35 wt.% acrylic acid, from 50 to 80 wt.% hydrophobic organic liquid having a boiling point above acrylic acid is you, and up to 5000 hours/million by weight aldehydes.

14. The method according to claim 11, characterized in that the liquid is a mixture which contains from 10 to 35 wt.% acrylic acid, from 50 to 80 wt.% hydrophobic organic liquid having a boiling point of acrylic acid, and up to 5000 hours/mil, by weight aldehydes.

15. The method according to item 12, wherein the liquid is a mixture which contains from 10 to 35 wt.% acrylic acid, from 50 to 80 wt.% hydrophobic organic liquid having a boiling point of acrylic acid, and up to 5000 hours/million by weight aldehydes.

16. The method according to one of claims 1 to 10, 12, 14 or 15, characterized in that the liquid contains the following components:
devil from 50 to 75 wt.%,
dimethylphthalate from 10 to 25 wt.%,
dikalova acid from 0.2 to 3 wt.%,
acrylic acid is from 15 to 35 wt.%, often from 15 to 25 wt.%,
water from 0.07 to 0.2 wt.%,
acetic acid is from 0.01 to 0.2 wt.%,
formic acid is from 0.001 to 0.02 wt.%,
propionic acid is from 0.001 to 0.02 wt.%,
phenothiazines from 0.01 to 0.1 wt.%,
phthalic anhydride from 0.1 to 1 wt.%,
benzoic acid is from 0.2 to 2 wt.%,
the anhydride of maleic acid is from 0.1 to 2 wt.%,
the benzaldehyde from 0.1 to 1 wt.% and
furfural from 0.01 to 0.05 wt.%.

17. The method according to claim 11, characterized in that the liquid contains the following components:
devil from 50 to 75 wt.%,
dimethylphthalate from 10 to 25 wt.%,
dikalova Ki the lot from 0.2 to 3 wt.%,
acrylic acid is from 15 to 35 wt.%, often from 15 to 25 wt.%,
water from 0.07 to 0.2 wt.%,
acetic acid is from 0.01 to 0.2 wt.%,
formic acid is from 0.001 to 0.02 wt.%,
propionic acid is from 0.001 to 0.02 wt.%,
phenothiazines from 0.01 to 0.1 wt.%,
phthalic anhydride from 0.1 to 1 wt.%,
benzoic acid is from 0.2 to 2 wt.%,
the anhydride of maleic acid is from 0.1 to 2 wt.%,
the benzaldehyde from 0.1 to 1 wt.% and
furfural from 0.01 to 0.05 wt.%.

18. The method according to item 13, wherein the liquid contains the following components:
devil from 50 to 75 wt.%,
dimethylphthalate from 10 to 25 wt.%,
dikalova acid from 0.2 to 3 wt.%,
acrylic acid is from 15 to 35 wt.%, often from 15 to 25 wt.%,
water from 0.07 to 0.2 wt.%,
acetic acid is from 0.01 to 0.2 wt.%,
formic acid is from 0.001 to 0.02 wt.%,
propionic acid is from 0.001 to 0.02 wt.%,
phenothiazines from 0.01 to 0.1 wt.%,
phthalic anhydride from 0.1 to 1 wt.%,
benzoic acid is from 0.2 to 2 wt.%,
the anhydride of maleic acid is from 0.1 to 2 wt.%,
the benzaldehyde from 0.1 to 1 wt.% and
furfural from 0.01 to 0.05 wt.%.

19. The method according to one of claims 1 to 10, characterized in that the liquid contains from 95 to 99.8 wt.% acrylic acid.

20. The method according to claim 11, characterized in that the liquid contains from 95 to 99.8 wt.% acrylic acid.

21. The method according to one of p, 14, 15, 17 or 18, characterized in that the liquid contains from 95 to 99.8 wt.% acrylic acid is.

22. The method according to item 13, wherein the liquid contains from 95 to 99.8 wt.% acrylic acid.

23. The method according to item 16, characterized in that the liquid contains from 95 to 99.8 wt.% acrylic acid.



 

Same patents:

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of continuous, heterogeneous, catalytic, partial gas-phase oxidation of at least one organic compound selected from a group comprising propene, acrolein, isobutene, methacrolein, isobutene and propane, in an oxidation reactor loaded with a gas mixture which, along with at least one compound to undergo partial oxidation and molecular oxygen as an oxidation agent, includes at least one diluent gas which is essentially inert in conditions of heterogeneous, catalytic, gas-phase partial oxidation, where the source of oxygen and inert gas for the loaded gas mixture is air which is compressed in a compressor beforehand from a low initial pressure value to a high final pressure value, where before entering the compressor, the air undergoes at least one mechanical separation procedure through which particles of solid substance dispersed in the air can be separated.

EFFECT: method prevents negative effect of solid particles on the air compression stage, undesirable increase in pressure loss and reduction of activity or selectivity of the catalyst.

21 cl, 2 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method for prolonged heterogeneously catalysed partial oxidation of propene to acrylic acid in gaseous phase, in which the initial gaseous reaction mixture 1, containing propene, molecular oxygen and at least one inert gas, where molecular oxygen and propene are in molar ratio O2:C3H6≥1, is first passed through a fixed catalyst bed 1 at high temperature at the first stage of the reaction, where the active mass of the catalysts is at least one multimetal oxide, containing molybdenum and/or tungsten, as well as at least one element from a group consisting of bismuth, tellurium, antimony, tin and copper, so that, conversion of propene in a single passage is ≥93 mol % and associated selectivity of formation of acrolein, as well as formation of acrylic acid by-product together is ≥90 mol %, temperature of the product gaseous mixture 1 leaving the first reaction stage is reduced if necessary through direct and/or indirect cooling, and if necessary, molecular oxygen and/or inert gas is added to the product gaseous mixture 1, and after that, the product gaseous mixture 1, acting as initial reaction mixture 2, which contains acrolein, molecular oxygen and at least one inert gas, where molecular oxygen and acrolein are in molar ratio O2:C3H4O≥0.5, is passed through a second fixed catalyst bed 2 at high temperature at the second reaction stage, where the active mass of the catalysts is at least one multimetal oxide, containing molybdenum and vanadium so that, conversion of acrolein in a single passage is ≥90 mol % and selectivity of the resultant formation of acrylic acid at both stages is ≥80 mol % in terms of converted propene, and temperature of each fixed catalyst bed is increased independently of each other. Partial oxidation in gaseous phase is interrupted at least once and at temperature of fixed catalyst bed 1 ranging from 250 to 550°C and temperature of fixed catalyst bed 2 ranging from 200 to 450°C, gaseous mixture G, which consists of molecular oxygen, inert gas and water vapour if necessary, is first passed through fixed catalyst bed 1, and then, if necessary, through an intermediate cooler and then finally through fixed catalyst bed 2, in which at least a single interruption takes place before temperature of the fixed catalyst bed 2 increases by 8°C or 10°C, wherein prolonged increase of temperature by 8°C or 10°C, is possible when virtual passage of temperature of the fixed catalyst bed in the period of time on the leveling curve running through the measuring point using the Legendre-Gauss method of the least sum of squares of errors, temperature increase of 7°C or 10°C is achieved.

EFFECT: method increases service life of catalyst.

24 cl, 1 ex, 3 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to improved method of carrying out heterogenous catalytic partial oxidation in gas phase of acrolein into acrylic acid, during which reaction gas mixture, containing acrolein, molecular oxygen and at least one inert gas-thinner, is passed through having higher temperature catalytic still layer, whose catalysts are made in such way that their active mass contains at least one oxide of multimetal, containing elements Mo and V, and in which during time, temperature of catalytic still layer is increased, partial oxidation in gas phase being interrupted at least once and at temperature of catalytic still layer from 200 to 450°C acrolein-free, containing molecular oxygen, inert gas and, if necessary, water vapour, as well as, if necessary, CO, gas mixture of G oxidative action is passed through it, at least one interruption being performed before increase of catalytic still layer temperature constitutes 2°C or 4°C or 8°C or 10°C during a long period of time, temperature increase constituting 2°C or 4°C or 8°C or 10°C over a long period of time occurring when in plotting factual course of temperature of catalytic still layer during time on laid through measurement points equation curve according to elaborated by Legendre and Gauss method of the least sum of error squares 2°C or 4°C or 8°C or 10°C temperature increase is achieved.

EFFECT: ensuring spread of hot point with time which is less than in previous methods.

21 cl, 3 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: method of (meth)acrolein or (meth)acrylic acid production is implemented by of catalytic phase oxidation reaction of propane, propylene, isobutylene or (meth)acrolein with oxygen-containing gas. Non-organic salt is used as heat carrier for reaction temperature adjustment. Pipeline for heat carrier feeding has adjustment valve adjusting heat carrier feed and circulation rate and rotating freedom of rotation axis. Rotation axis adjoins case with capability of sliding against each other. Gasket filling material sealing the case of adjustment valve is based on mica.

EFFECT: high-precision temperature adjustment ensuring stable process of gas phase catalytic oxidation.

5 cl, 5 dwg, 2 ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to an improved method for synthesis of acrolein or acrylic acid or their mixture. Method involves at step (A) propane is subjected for partial heterogenous catalyzed dehydrogenation in gaseous phase to form a gaseous mixture A of product comprising molecular hydrogen, propylene, unconverted propane and components distinct from propane and propene, and then from a gaseous mixture of product from step (A) distinct from propane and propylene at least partial amount of molecular hydrogen is isolated and a mixture obtained after this isolation is used as a gaseous mixture A' at the second step (B) for loading at least into one oxidation reactor and in at least one oxidation reaction propylene is subjected for selective heterogenous catalyzed gas-phase partial oxidation with molecular oxygen to yield as the end product of gaseous mixture B containing acrolein or acrylic acid, or their mixture, and the third (C) wherein in limits of partial oxidation of propylene at step (B) of gaseous mixture B acrolein or acrylic acid or their mixtures as the end product are separated and at least unconverted propane containing in gaseous mixture at step (B) is recovered to the dehydrogenation step (A) wherein in limits of partial oxidation of propylene at step (B) molecular nitrogen is used as additional diluting gas. Method provides significant decreasing of by-side products.

EFFECT: improved method of synthesis.

39 cl, 11 ex

FIELD: industrial production of methacrylic acids at reduced amount of industrial wastes.

SUBSTANCE: proposed method is performed by catalytic oxidation of propane, propylene or isobutylene in vapor phase at separation of final product and forming of high-boiling mixture as by-product which contains (according to Michaels addition) water, alcohol or methacrylic acid added to methacrylic group. By-product is decomposed in thermal decomposition reactor at simultaneous distillation of decomposition products in distilling column from which methacrylic acid is taken in form of distillate. Flow of liquid decomposition residue is forced for peripheral direction by means of mixing blades before withdrawal from reactor. Peripheral direction is obtained with the aid of liquid fed from the outside of decomposition reactor; to this end use is made of initial high-boiling material or flow of liquid discharged from decomposition reactor. If necessary, etherification stage is performed through interaction with alcohol for obtaining methecrylic ester. Decomposition of by-product formed at obtaining methacrylic acid by oxidation of propylene or isobutylene or at obtaining methacrylic acid by interaction of acid with alcohol by alcohol through introduction of by-product into thermal decomposition reactor provided with distilling column which has plates made in form of disks and toroids for simultaneous decomposition and distillation. Plant proposed for realization of this method includes thermal decomposition reactor and distilling column, level meters and lines for discharge of liquid containing easily polymerized compounds. Level indicator mounted at area of accumulation of liquid shows pressure differential. Line for detecting the side of high pressure of this level meter is connected with accumulated liquid discharge line.

EFFECT: updated technology; increased yield of target products.

38 cl, 14 dwg, 2 tbl, ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for synthesis of acrolein and/or acrylic acid from propane and/or propene. Method involves the following steps: (a) isolating propane and/or propene from gaseous mixture A containing propane and/or propene by their absorption with adsorbent; (b) isolating propane and/or propene from adsorbent to form gas B containing propane and/or propene, and (c) using gas B obtained in stage (b) for oxidation of propane and/or propene to acrolein and/or acrylic acid wherein the heterogeneous catalytic dehydrogenation of propane without feeding oxygen is not carried out. Method shows economy and maximal exploitation period of used catalyst without its regeneration.

EFFECT: improved method of synthesis.

12 cl, 7 dwg, 1 ex

The invention relates to an improved method for the removal of formaldehyde or its adducts of organic liquid mixtures obtained in the production of methyl methacrylate containing at least a carboxylic acid or an ester of carboxylic acid and formaldehyde or its adducts, which forms a two-phase mixture of water, comprising at least one extraction liquid organic mixture in the system liquid-liquid using water as the extractant with getting the flow of the organic phase and flow of the aqueous phase, and the flow of the organic phase contains significantly reduced the concentration of formaldehyde or its adducts compared with the liquid organic mixture

The invention relates to an improved process for the preparation of methyl methacrylate, comprising the stages of (i) interaction propionic acid or its ester with formaldehyde or its predecessor in the condensation reaction with the formation of the stream of gaseous products containing methyl methacrylate, residual reactants, methanol and by-products, (ii) processing at least one portion of the stream of gaseous products with the formation of a stream of liquid products containing almost all of the methyl methacrylate and at least one impurity, which melts at a temperature above the melting temperature of pure methyl methacrylate, run over the flow of the liquid product at least one operation fractional crystallization, which contains the stage (iii) cooling the specified flow of liquid product to a temperature between about -45oAnd about -95oSo that the flow of liquid product forms solid crystals of methyl methacrylate and uterine fluid, and these crystals have a higher content of methyl methacrylate than the specified stream of liquid products or uterine fluid, (iv) the separation of these crystals of solid methyl methacrylate from the specified match Azania impurity in a lower concentration, than the specified stream of liquid products

The invention relates to the production of Ethylenediamine acids or their esters

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of producing butylacrylate involving: reaction of acrylic acid with butanol in the presence of water and a catalyst in a reactor; where the starting material is an aqueous solution of acrylic acid which is at least one of: (1) condensed water, obtained from vapour used in a kinetic vacuum pump which transports gas after trapping fluid process medium- vapour which is blown at high speed, (2) water for hydraulic sealing in a liquid ring pump which isolates liquid-water after air is let into the housing, (3) water used for collecting acrylic acid in the device which collects acrylic acid from an acrylic acid-containing gas, and acrylic acid which is not present in the aqueous solution of acrylic acid, where the device used for collecting acrylic acid is one or more devices selected from a group comprising a packed column, a plate-type column, a spray column and a scrubber. The invention also relates to a method of producing a super-absorbing polymer based on acrylic acid, involving the following steps: polymerisation of acrylic acid, in which the aqueous phase used is an emulsified aqueous solution of an acrylic acid monomer and water, dehydration of the obtained mixture during azerotropic distillation, where the starting material is aqueous acrylic acid solution which is at least one of the following: condensed water obtained from vapour used in a kinetic vacuum pump which transports gas after trapping fluid process medium - vapour, which is blown at high speed, water for hydraulic sealing in a liquid ring pump which isolates liquid-water after air is let into the housing, water used for collecting acrylic acid in the device which collects acrylic acid from an acrylic acid-containing gas, and acrylic acid which is not present in the aqueous solution of acrylic acid, where the device used for collecting acrylic acid is one or more devices selected from a group comprising a packed column, a plate-type column, a spray column and a scrubber.

EFFECT: design of an efficient method of using aqueous solution of (meth)acrylic acid with low concentration, formed at the stage for producing/storing (meth)acrylic acid.

13 cl, 2 ex

FIELD: explosives.

SUBSTANCE: method is described for reducing amount and/or removing permanganate-reducing compounds for methanol carbonylation process to produce acetic acid, where the method involves a stage for separating the said carbonylation product, resulting in a volatile fraction containing acetic acid, organic iodide, water and at least one permanganate-reducing compound, and a less volatile fraction; distillation of the said volatile fraction, resulting in a purified acetic acid product and a first overhead fraction containing organic iodide, water, acetic acid and at least one permanganate-reducing compound; distillation of at least part of the first overhead fraction in a first distillation apparatus to form a second overhead fraction rich in permanganate-reducing compound; addition of dimethyl ether to the second overhead fraction, extraction of the second overhead fraction with water to form a second overhead extraction stream and a water stream containing at least one permanganate-reducing compound and separation from the water stream, containing at least one permanganate-reducing compound; and returning at least the first part of the extracted second overhead fraction to the said distillation apparatus, method of producing acetic acid and method of separating a mixture obtained during carbonylation of methanol.

EFFECT: more efficient removal of permanganate-reducing compound from a system by returning part of the stream of purified product, reduced loss during waste removal.

34 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of reducing and/or removing reducing permanganate compounds (RPC), carboxylic acids C3-8 and C2-12 of alkyl iodide compounds, formed during carbonylation of a carbonylation-capable reagent, chosen from a group consisting of methanol, methylacetate, methyl formate, dimethyl ether and their mixture, into commercial-grade acetic acid, in which products of the said carbonylation include a volatile phase, which is distilled thereby obtaining purified commercial-grade acetic acid and the first distillate, containing methyl iodide, water and at least one reducing permanganate compound, where improvement includes stages: (a) separation of the obtained first distillate into a light and a heavy phase, with subsequent distillation of at least part of the light phase for obtaining a second distillate, containing methyl iodide, dimethyl ether and at least said one reducing permanganate compound, which is taken to the next distillation stage, where a stream is formed as distillate, containing reducing permanganate compound; (b) addition of dimethyl ether into supply of said stream containing reducing permanganate compound, and extraction of this stream with water to form the first raffinate and first aqueous extraction stream, containing at least said one reducing permanganate compound; and (c) extraction of the first raffinate with water to form the second raffinate and second aqueous extraction stream, containing at least said one reducing permanganate compound. Invention also relates to a method of separating a mixture, containing water, acetic acid, methyl iodide, methyl acetate, methanol and at least one reducing permanganate compound (RPC), obtained by separating the liquid-vapour phase of the output stream of the methaol carbonylation reactor to form a vapour phase and a liquid phase, distillation of the vapour phase to form a liquid product which contains acetic acid, and first distillate, condensation of at least part of the first distillate thereby obtaining a liquid composition which contains methyl acetate, methyl iodide, water, methanol and at least one reducing permanganate compound (RPC), separation of the obtained liquid composition into a light and a heavy phase, which includes methyl iodide, where the light phase is the said mixture, where the said method involves stages: (a) distillation of the mixture to obtain a second distillate which contains at least one reducing permanganate compound (RPC), which is taken for the next distillation stage, where a stream is formed as distillate, containing reducing permanganate compound and dimethyl ether; and (b) extraction of concentrated reducing permanganate compound with water, where stage (b) includes at least two consecutive extraction stages, where each extraction stage involves bringing concentrated reducing permanganate compound into contact with water and separation of the aqueous stream, containing at least said one reducing permanganate compound, where dimethyl ether is added to the said distillate stream concentrated with reducing permanganate compound before extraction of the concentrated reducing permanganate compound with water.

EFFECT: process is described for removing reducing permanganate compounds from a stream from carbonylation of methanol.

28 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a thermal separation method using fractional condensation of a product-gas mixture, obtained through heterogeneous catalysed partial oxidation of propene and/or propane in gaseous phase to acrylic acid, for separating at least one mass flow, concentrated with acrylic acid, from a product-gas mixture containing acrylic acid, which involves continuous static operation of at least one device for thermal separation, containing at least one effective separation chamber with a fractionation column which has mass-transfer trays as built-in separating elements, in which the product-gas mixture is loaded, containing acrylic acid as at least one mass flow, and from which at least one mass flow containing acrylic acid is unloaded under the condition that, the overall mass flow loaded into the effective separation chamber and obtained from combining separate mass flows loaded into the separating chamber, contains X wt % components distinct from acrylic acid, the mass flow which is unloaded from the effective separation chamber with the largest content of acrylic acid, contains Y wt % components distinct from acrylic acid, ratio X:Y is ≥5, effective separation chamber, except the loading and unloading place, is bordered by a solid phase and contains, besides the mass-exchange trays as built-in separating elements in the fractionation column, at least one circulating heat exchanger, and total volume of the chamber, filled with liquid phase, is ≥1 m3, wherein temperature of the liquid phase is at least partially ≥80°C, when the effective separation chamber is divided into n separate volume elements, wherein the highest and lowest temperature of liquid phase in a separate volume element differ by not more than 2°C, and the volume element in the effective separation chamber is solid, total dwell time ttotal.

≤20 h, where A = (Ti-To)/10°C, To= 100°C, Ti = arithmetic mean value of the highest and lowest temperature of the ith volume element in the liquid phase in °C, msi = total mass of acrylic acid in the volume of the liquid phase of the ith volume element, mi = total liquid phase mass unloaded from the ith volume element, and is the sum of all volume elements i, under the condition that, volume elements i with liquid phase mass mi and as volume elements with a dead zone are also not included in the sum of all volume elements i, as well as volume elements i, which do not contain liquid phase, and total amount of liquid phase contained in volume elements with a dead zone is not more than 5 wt % of the total amount of liquid phase contained in the effective separation chamber.

EFFECT: separation of mass flow concentrated with acrylic acid.

10 cl, 12 dwg, 2 ex, 2 tbl

FIELD: chemistry.

SUBSTANCE: proposed method involves the following stages: (a) reaction of carbon monoxide with at least one reagent chosen from a group, consisting of methanol, methyl acetate, methyl formate and dimethyl ether and their mixture in a reaction medium, containing water, methyl iodide and catalyst for obtaining the reaction product, containing acetic acid; (b) gas-liquid separation of the said reaction product to obtain a volatile phase, containing acetic acid, water and methyl iodide and a less volatile phase, containing the said catalyst; (c) distillation of the above mentioned volatile phase to obtain a purified product of acetic acid and a first overhead fraction, containing water, methylacetate and methyl iodide; (d) phase separation of the above mentioned first overhead fraction to obtain the first liquid phase, containing water, and second liquid phase, containing methyl iodide and methyl acetate; and (e) feeding dimethyl ether directly or indirectly into a decantation tank of light fractions for phase separation of the said first overhead fraction in a quantity, sufficient for increasing separation of the first overhead fraction to form the first and second liquid phases.

EFFECT: improvement of the method of producing acetic acid.

8 cl, 1 dwg

FIELD: chemistry.

SUBSTANCE: method of (meth)acrylic acid purification includes the stages as follows: distillations of the liquid containing raw (meth)acrylic acid being acrylic acid or methacrylic acid with one or more polymerisation inhibitors added as chosen from group consisting of phenol derivative, phenothiazine derivative, copper (meth)acrylate and copper dithiourethane, for the purpose to produce condensate of (meth)acrylic acid, containing (meth)acrylic acid of purity at least 90%; adding polymerisation inhibitor containing phenol derivative to condensate; and delivery of oxygen-containing gas that contains oxygen to condensate of (meth)acrylic acid in reflux tank wherein condensate of (meth)acrylic acid is collected, wherein oxygen-containing gas is delivered to condensate in reflux tank with using small-size bubble liquid injector, and pressure connection for oxygen-containing gas delivery to liquid injector whereat ratio (nm/tn) of oxygen delivery in oxygen-containing gas and condensate flow supplied to reflux tank at 0°C, 1 atm complies with ratio shown in equation 0.004≤A/B≤1.0, where A stands for O2 delivery (nm3/hour), B stands for condensate flow (tn/hour) of the condensate supplied to reflux tank, and symbol n in nm3/hour specifies the value under normal conditions (0°C, 1 atm: normal conditions).

EFFECT: effective method of high purity acid production wherein acid polymer formation in made condensate is prevented.

12 cl, 6 dwg, 7 ex

FIELD: chemistry.

SUBSTANCE: present invention pertains to improvement of the method of producing (met)acrylic acid and complex (met)acrylic esters, involving the following stages: (A) reacting propane, propylene or isobutylene and/or (met)acrolein with molecular oxygen or with a gas, containing molecular oxygen through gas-phase catalytic oxidation, obtaining crude (met)acrylic acid; (B) purification of the obtained crude (met)acrylic acid, obtaining a (met)acrylic acid product; and (C) reacting raw (met)acrylic acid with alcohol, obtaining complex (met)acrylic esters, in the event that the installation used in any of the stages (B) and (C), taking place concurrently, stops. The obtained excess crude (met)acrylic acid is temporarily stored in a tank. After restoring operation of the stopped installation, the crude (met)acrylic acid, stored in the tank, is fed into the installation, used in stage (B), and/or into the installation used in stage (C). (Met)acrylic acid output of the installation used in stage (A) should be less than total consumption of (met)acrylic acid by installations used in stages (B) and (C).

EFFECT: the method allows for processing (met)acrylic acid, temporarily stored in a tank, when stage (B) or (C) stops, without considerable change in workload in stage (A).

2 ex

FIELD: chemistry.

SUBSTANCE: invention concerns improved method for obtaining (meth)acrylic acid involving steam phase catalytic oxidation of propylene, propane or isobutylene for production of reaction mix, absorption of oxidised reaction product in water to obtain water solution containing (meth)acrylic acid, concentration of water solution in the presence of azeotropic agent and distillation of obtained (meth)acrylic acid in distillation column to obtaining purified (meth)acrylic acid. During operation of distillation column, including operation interruption and resumption, the column is washed with water, and afterwards azeotropic distillation is performed in the presence of azeotropic agent.

EFFECT: efficient and fast cleaning of distillation column with extraction of valuable substance.

5 cl, 5 dwg, 3 ex

FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to separation of product and by-product stream in production of alkylaromatic acids, in particular terephthalic acid, via oxidation of hydrocarbon with molecular oxygen in acetic acid solution. In order to recover acetic acid, it is separated from methyl acetate in distillation column in the form of bottom stream. Distillate containing methyl acetate by-product is catalytically hydrolyzed in hydrolysis reactor using preferably water withdrawn from emission gas washing column. Non-decomposed methyl acetate is separated from methanol and recovered in the form of high-concentration aqueous solution by extractive distillation with water, after which routed back to hydrolysis so that essentially all methyl acetate by-product is recovered and reused in the form of acetic acid. Reaction mixture in the hydrolysis stage contains no more than 30% acetic acid and weight amount of water by 3 or more times exceeding amount of recovered methyl acetate.

EFFECT: improved economic characteristics of process due to reduced loss of acetic acid and additional recovery of acetic acid when performing hydrolysis of methyl acetate.

6 cl, 3 dwg, 6 tbl, 3 ex

Rectification plant // 2393904

FIELD: process engineering.

SUBSTANCE: invention relates to chemical, petrochemical, food and other industries, in particular to method of separating bi- and multi-component mixes by rectification. Rectification plant comprises rectification column representing tubular-case heat exchange apparatus with tube space making column bearing section with tubular annulus making column distillation section, heat exchanger communicated with top part of tubular annulus, compressor to compress vapors, distiller communicated with top part of column concentration section, line to feed vapor-fluid mix from column bottom via heat exchanger into top part of tubular annulus, and reducer valve arranged in aforesaid line and fitted on one shaft with compressor. Tubular annulus and space inside tube are filled with packing, grid or screen is arranged nearby tube bottom edge while tube walls are corrugated.

EFFECT: higher efficiency due to lower power consumption.

4 cl, 4 dwg

Up!