Method of separation of fumaric acid and other side components in obtaining maleic acid anhydride

FIELD: chemistry.

SUBSTANCE: method is realised by heterogeneous catalytic oxidation of carbon by molecular oxygen, selected from group of benzol, n-butane, n-butene, in presence of catalyst, which contains vanadium, phosphorus and oxygen, which includes: (a) maleic acid anhydride absorption from impure mixture of products by absorbing agent, which contains organic solvent, in absorption column; (b) desorption of maleic acid anhydride from absorbing agent, which is obtained at stage (a), enriched by maleic acid anhydride, in desorption column; as well as (c) total or partial return to stage (a) of absorbing agent, depleted at stage (b) by content of maelic acid anhydride, is differ in fact, that (d) total or partial quantity of absorbing agent, depleted on stage (b) by content of maelic acid anhydride, for required sedimentation of fumaric acid is cooled and/or subjected to concentration by evaporating absorbing agent to such degree, that difference between concentration of fumaric acid in reverse flow at output from desorption column c (FA, at output from desorption column) at there existing conditions, expressed in weight p/mln, and balanced concentration of fumaric acid, corresponding to solubility curve, after cooling and/or evaporation of absorbing agent part c (FA, balanced, after cooling/steaming), expressed in weight p/mln, constitutes value larger or equal 250 wt, p/mln, and for sedimentation and separation of fumaric acid applied is reservoir with built-in nozzle elements, and average time of staying in reservoir with built-in nozzle elements constitues from 0.05 to 6 hours; (e) fumaric acid, precipitated in form of solid substance due to operations at stage (d), totally or partially, in continuous or periodic mode is removed from reverse flow of absorbing agent; and (f) depleted by content of fumaric acid absorbing agent from stage (e) totally or partially returns on stage (a).

EFFECT: reduction of formation of fumaric acid sedimentations with obtaining maelic acid anhydride.

12 cl, 3 dwg, 5 ex

 

This invention relates to a method of reducing the formation of deposits fumaric acid in obtaining maleic anhydride by heterogeneous catalytic oxidation with molecular oxygen of a hydrocarbon selected from the group of benzene, n-butane, n-butene and 1,3-butadiene, in the presence of a catalyst containing vanadium, phosphorus and oxygen, including:

(a) absorption of maleic anhydride from crude mixture of products absorbing agent containing an organic solvent in the absorption column;

(b) desorption maleic anhydride obtained from stage (a) absorbent agent enriched with maleic acid anhydride, in the desorption column; and

(c) a complete or partial return to the step (a) absorbent agent, depleted at the stage (b) on the content of maleic anhydride.

The method according to the invention is used to improve the process of industrial production of maleic anhydride. The anhydride of maleic acid is an important intermediate product in the synthesis of γ-butyrolactone, tetrahydrofuran and 1,4-butanediol, which, for their part, are used as solvents and can be processed further, for example, polymers, such as polytetrahydrofuran or polyvinylpyrrolidone.

The maleic anhydride is islote can be obtained through partial oxidation of hydrocarbons, in particular, benzene or hydrocarbons containing 4 carbon atoms, such as 1,3-butadiene, n-butene or n-butane. This reaction is highly exothermic and requires discharge of the heat of reaction sufficiently. Typically, the interaction is carried out in shell-and-tube reactor with a circulation of brine or in the fluidized bed. Typically, the anhydride of maleic acid formed in the reaction, the resulting crude mixture of products absorb with a solvent. In addition to the maleic anhydride is also absorbed by other components contained in the crude mixture of products, such as, for example, formed by the oxidation of water. However, the water partially reacts with the anhydride of maleic acid with the formation of maleic acid, which, in turn, partially isomerized in fumaric acid. Fumaric acid is a dicarboxylic acid, very slightly soluble in water or organic solvents, which forms deposits and thus may cause clogging of the equipment elements, such as, for example, columns, exchangers, pumps, pipes and the like.

To prevent such clogging caused fumaric acid, in the prior art there are already proposals.

So, in the international application WO 96/029,323 described that the absorbent agents who, containing fumaric acid, after separation of maleic anhydride distillation of the washed aqueous extracting agent, so as to prevent the formation of deposits. The disadvantage of this method is the considerable complexity, which is necessary to mix the wash water in industrial equipment to obtain a dicarboxylic acid containing 4 carbon atoms, or derivatives thereof, and then to separate the phases. Moreover, because of the inevitable losses of expensive product and a solvent having a large cost. In addition, because of the additional contribution in the process of water formation of fumaric acid is further enhanced.

In the German patent DE 102006024903.8 offered after separation by distillation of maleic anhydride absorbing agent containing fumaric acid, fully or partially subjected to catalytic hydrogenation, and fully or partially return to the stage of absorption.

Proceeding from the prior art, in this invention was the goal to significantly reduce the formation of fumaric acid on the equipment elements, and also caused thereby clogging, installation and cleaning of equipment, and it is terminated when receiving maleic anhydride, with a minimum of technical complexity and without fuss the breath described above disadvantages.

According to this, a method was found to reduce the formation of deposits of fumaric acid in obtaining maleic anhydride by heterogeneous catalytic oxidation with molecular oxygen of a hydrocarbon selected from the group of benzene, n-butane, n-butene and 1,3-butadiene, in the presence of a catalyst containing vanadium, phosphorus and oxygen, including:

(a) absorption of maleic anhydride from crude mixture of products absorbing agent containing an organic solvent in the absorption column;

(b) desorption maleic anhydride from the absorbent agent, enriched anhydride maleic acid, obtained in stage (a), in the desorption column; and

(c) a complete or partial return to the step (a) absorbent agent, depleted at the stage (b) on the content of maleic anhydride, characterized in that

(d) full or partial amount of absorbent agent, depleted at the stage (b) on the content of maleic anhydride, necessary for the deposition of fumaric acid is cooled and/or subjected to concentration by evaporation of part of the absorbent agent in such an extent that the difference between the concentration of fumaric acid in the reverse flow at the outlet of the desorption column (FC, at the outlet of the desorption column) and when audica there conditions expressed in mass ppm, and the equilibrium concentration of fumaric acid corresponding to the solubility curve, after cooling and/or evaporation of part of the absorbent agent (FC, equilibrium, after cooling/evaporation), expressed in mass ppm, has a value greater than or equal to 250 ppm, mass.;

(e) fumaric acid, precipitated as solids due to the operations in stage (d), fully or partially, in a continuous or periodic mode is removed from the reverse flow of absorbent agent; and

(f) depleted on the content of fumaric acid absorbing agent from step (e) wholly or partly returned to the step (a).

The method according to the invention significantly reduces the undesirable formation of fumaric acid through targeted deposition of fumaric acid in the reverse flow absorbent agent with operations according to the invention, and separating precipitated fumaric acid.

According to the invention unexpectedly found that fumaric acid under the conditions of heterogeneous catalytic obtain maleic anhydride by oxidation of hydrocarbons has an extraordinary tendency to form supersaturated solutions. So, contrary to the expectations of the expert, for example, cooling of absorbiruetsa, depleted on the content of maleic anhydride from stage (b), it is deposited in accordance with the solubility curve, and even in the presence of existing crystalline fumaric acid forms more supersaturated solution. The saturation can amount to several hundred ppm, mass., and partly even more than a thousand ppm, mass., and, consequently, an amount several times greater than the solubility. The corresponding is true also for the case of concentration by evaporation of part of the absorbent agent. This unexpected behavior leads to the fact that, in accordance with the method of obtaining maleic anhydride according to the level of technology fumaric acid, apparently uncontrolled deposited in returning back flow of absorbent agent and downstream elements of the equipment and at the same time clog the apparatus and pipelines.

According to the invention thanks to these operations has been purposefully to besiege fumaric acid, despite the pronounced tendency to form supersaturated solutions.

Targeted deposition is achieved using listed for stage (d) operations targeted cooling and/or focused concentration by evaporation of part of the absorbent agent, and listed by op the walkie-talkies purposefully set the difference between the concentration of fumaric acid in the reverse flow at the outlet of the desorption column (FC, at the outlet of the desorption column) under the existing conditions, expressed in ppm, mass., and the equilibrium concentration of fumaric acid corresponding to the solubility curve, after cooling and/or evaporation of part of the absorbent agent (FC, equilibrium, after cooling/evaporation), expressed in ppm, mass., component value is greater than or equal to 250 ppm of the mass. The upper bound of this difference is realized with the minimum equilibrium concentration of fumaric acid according to the solubility curve 0 ppm mass. when correspondingly lower temperature, and therefore corresponds to the concentration of fumaric acid in the reverse flow at the outlet of the desorption column (FC, at the outlet of the desorption column). Preferably the difference with (FC, at the outlet of the desorption column) minus C (FC, equilibrium, after cooling/evaporation) is set to be greater than or equal to 350 and preferably greater than or equal to 500. In some cases, for example, at relatively high concentrations of fumaric acid in the absorbent agent, usually above 1500 ppm, mass., beneficial to maintain the difference with (FC, at the outlet of the desorption column) minus C (FC, equilibrium, after cooling/evaporation) is particularly preferably greater than or equal to 700, most preferably greater than or equal to 1000 and, in castnet is, greater than or equal to 1500 ppm of the mass. Preferably this difference is the value less than or equal to 5000, and particularly preferably less than or equal to 3000 ppm of the mass.

The concentration of fumaric acid in the reverse flow at the outlet of the desorption column (FC, at the outlet of the desorption column) can be analytically determined in a simple way. This analysis can be conducted, for example, using gas chromatography with calibration mixtures. Calibration is preferably used an internal standard, such as, for example, a simple dimethyl ether of diethylene glycol. Before gas chromatographic analysis of a sample, usually homogenized, that is, dissolved in the solvent. The most appropriate solvent is, for example, N,N-dimethylformamide. After homogenization, the sample is preferably subjected to siciliani using a suitable cilleruelo agent, e.g. N,O-batrineteasinguratatea (BSTFA). As the separation columns are particularly suitable capillary column containing 100% dimethylpolysiloxane (for example, type DB-1 firm Agilent) or (14%cyanopropyl)methylpolysiloxanes (for example, type DB-1701 company Agilent), respectively, preferably having a length of 60 m, inner diameter 0.32 mm and a film thickness of 1 μm.

Under the outlet of the desorption column ledue the same point, where the stream leaves the column. Preferably this is done through the conclusion of the cube column. From it also it is necessary to take samples for the analytical determination of the concentration.

The equilibrium concentration of fumaric acid in accordance with the solubility curve after cooling and/or evaporation of part of the absorbent agent (FC, equilibrium, after cooling/evaporation) can easily be taken from the appropriate curve of solubility specific temperature. This curve temperature-dependent solubility of fumaric acid used, if necessary, one stripped off partially absorbing agent (solubility curve) can be determined experimentally, according to the following method:

(1) the Absorbent agent, which must be defined temperature dependence of the solubility of fumaric acid, cooled to 0°C in mixed condition in a thermostatted vessel with a stirrer.

(2) Then cooled to 0°C. the absorbent agent is added approximately 1% of the mass. fumaric acid in the form of pure substances, however, at least twice the number of maximum solubility, which should be expected and measured.

(3) After addition of fumaric acid obtained mixture was stirred for 24 hours at 0°C.

(4) If you want ODA is to divide the solubility at 0°C, after the 24-hour time mixing of the mixed suspensions select the sample. The sampling is performed with a syringe, which is equipped with a filter attachment for a syringe for retaining undissolved fumaric acid. As filter nozzle of the syringe is used a membrane filter with a size of pores of 0.2 micrometer. Selected through this filter, not containing solids sample fluid contains dissolved fumaric acid. Its concentration is determined similarly to the method of analysis described for the determination of C (FC, at the outlet of the desorption column). A specific analysis of the content of fumaric acid corresponds to the solubility of fumaric acid in the solvent at 0°C.

(5) If you want to determine the solubility at temperatures above 0°C, the suspension remaining after step (4), is heated to the desired temperature with further stirring. When the new regulation, the higher the temperature of the suspension may deviate from the desired temperature of not more than 3°C. When the desired temperature is set, further stirring at a constant temperature continue at least for 4 hours.

(6) At the end of this time subsequent mixing occurs re-sampling so that campisano in paragraph (4). At each sampling, as a rule, apply a new filter cap for the syringe. If the desired temperature is more than 10°C above room temperature, the syringe and filter cap for syringe respectively pre heated (e.g., thermostat).

(7) Filtered the liquid sample is then analyzed for the concentration of fumaric acid in accordance with the methodology described in paragraph (4). A specific analysis of the content of fumaric acid corresponds to the solubility of fumaric acid in the solvent at a fixed temperature.

(8) If should be determined solubility in other, even higher temperatures, then act similar to paragraphs (5) through (7). It should be taken into account that discussed in chronological order the solubility of fumaric acid on the basis of its pronounced tendency to saturation should be determined only from a lower to a higher temperature measurements.

Temperature dependence of the solubility of fumaric acid in pure di-n-butylphthalate and absorbent agent on the basis of di-n-butylphthalate used in industry equipment defined in this way, in simplified form presented in figure 1. The type and number of present side is komponentov in the case of absorbent agent on the basis of di-n-butylphthalate used in industry equipment not significantly affect the solubility of fumaric acid. As a side component, due to technical conditions, should lead, for example, water, the anhydride of maleic acid, maleic acid, acrylic acid, methacrylic acid, acetic acid, propionic acid, phthalic anhydride and phthalic acid. Therefore, a region located in the grey area in figure 1, gives the interval in which the solubility of fumaric acid in pure di-n-butylphthalate and investigated absorbent agent on the basis of di-n-butylphthalate used in industry equipment. Drawn through it line corresponds to the curve of alignment.

It should be emphasized that according to the invention, of course, the solubility of fumaric acid should always be taken into account in the corresponding specific present absorbent agent. Thus, ideally, when technically implemented method should also determine the temperature dependence of the solubility of fumaric acid using the production test in the reverse flow of the absorbent agent. When more accurate qualitative and quantitative data regarding side components of the alternative, but also possible is the use of appropriate synthetic mix.

In the case of concentration by evaporation of the absolute is berousek agent full or partial amount of absorbent agent, depleted on the content of maleic anhydride from stage (b), is fed into the column, usually working under vacuum, and one stripped off the absorbent agent is distilled off via the top of column. However increases the concentration of dissolved fumaric acid, and then when exceeding the solubility and saturation. In order to facilitate the concentration usually is preferable to operate the column at a temperature above the temperature of the return stream absorbent agent, and then cooling the concentrated absorbent agent. When used in highly preferred di-n-butylphthalate the concentration process can be carried out particularly preferably at an absolute pressure of between 0.001 and 0.004 MPa and a temperature of from 180 to 250°C.

Particularly preferably in stage (d) of the method according to the invention the total or partial amount of absorbent agent, depleted on the content of maleic anhydride in stage (b), for the targeted deposition of fumaric acid is cooled to very low temperatures in the reverse flow of the absorbent agent. This decreases the solubility of fumaric acid in the absorbent agent, and fumaric acid partially precipitates in the form of solids.

Obtained in stage (b), containing depleted in the July maleic anhydride absorbent agent depending on the type of separation, as a rule, has a temperature of from 100 to 300°C. In the General case it contains from 0.01 to 5 wt. -%, and preferably from 0.02 to 2% of the mass. fumaric acid, and, as a rule, from 0.01 to 2 wt. -%, and preferably from 0.02 to 0.5% of the mass. water. As a rule, the content of fumaric acid is higher, the higher the water content, and the higher the temperature during the absorption stage (a) and in the separation stage (b). In addition, fumaric acid, depleted absorbent agent also contains as by-products of maleic acid, alkyl substituted derivatives of maleic acid, acrylic acid, methacrylic acid, acetic acid and propionic acid. Here are also other compounds that can be formed from absorbent agent, and this depends on the nature of the absorbent agent. For example, if you are esters of phthalic acid (phthalates), in addition to the anhydride of phthalic acid, phthalic acid and its complex monoufia, are also possible esters formed by transesterification of the above acids.

Specified in stage (a), the preferred cooling obtained in stage (b), depleted on the content of maleic anhydride absorbent agent can be done in a variety of ways. As a rule, use the cooling medium, which act is via the surface of the heat exchanger. Suitable cooling media within the energy systems should be called, for example, water, air, or other gaseous or liquid streams. Thus, it is preferable cooling to the lowest temperature in the return flow of the absorbent agent. The reverse flow of absorbent agent should understand the entire area between the Department of maleic anhydride at the stage (b) and the absorption of maleic anhydride at the stage of (a)wrapped around the absorbent agent is depleted on the content of maleic anhydride. In order to achieve a particularly preferred degree of deposition of fumaric acid to the desired local region in reverse, the flow of the absorbent agent, this absorbent agent for targeted cooling is cooled preferably to a value from 1 to 250°C, particularly preferably from 50 to 200°C. and most preferably in the amount from 100 to 150°C relative to other areas in the reverse flow of the absorbent agent. The temperature indicated at stage (d) as the lowest temperature is preferably from 10 to 100°C., particularly preferably from 20 to 90°C. and most preferably from 30 to 70°C.

Preferably the absorbent agent is depleted on the content of maleic anhydride, cooled to such an extent and is and accordingly concentrated by evaporation absorbent agent to such an extent, the number of deposited fumaric acid with at least a degree of formation of fumaric acid in the entire installation.

The absolute pressure of the absorbing agent in the reverse flow of the absorbent agent is from 0.01 to 1 MPa, preferably from 0.09 to 0.5 MPa, and especially preferably from 0.09 to 0.3 MPa.

With the method according to the invention as the total number or partial number absorbent agent, depleted at the stage (b) on the content of maleic anhydride, may, at stage (d) for targeted deposition of fumaric acid to be cooled and/or subjected to concentration by evaporation of part of the absorbent agent. If only a partial quantity is cooled to precipitate and/or concentration by evaporation of part of the absorbent agent, the residual stream is preferably fed back to the stage of deposition, and then combined with the stream depleted in the content of fumaric acid, or alternatively, is fed to the absorption stage (a) in divided form. The deposition of the partial quantities compared to deposition from the total may be particularly preferred. So, due to the small volume can be used the device of a smaller size and usually also cheaper. Cu is IU, for example, if the preferred cooling with equal cooling capacity in this partial flow can be achieved with lower temperatures, and, consequently, also more intense depletion by fumaric acid. In General, it may be preferable from the total flow to achieve less intense impoverishment for fumaric acid in the apparatus of larger size with the same cooling capacity. Similarly, the corresponding is true for the process of concentrating by evaporation of part of the absorbent agent.

Preferably in stage (d) is cooled and/or subjected to concentration by evaporation of part of the absorbent agent is from 5 to 100% and particularly preferably from 5 to 90% absorbent agent, depleted on the content of maleic anhydride in stage (b).

Due to the described cooling or concentration by evaporation of part of the absorbent agent fumaric acid partially precipitated as solids, and the deposition due to the previously mentioned exceptional tendency to saturation is clearly less than expected in accordance with the solubility curve. In addition to fumaric acid upon cooling deposited, if necessary, also other, less soluble by-products and degradation products is possible. In particular, when used as an absorbent agent esters of phthalic acid is also produced from them phthalic anhydride or phthalic acid. In the deposition process can be detected crystalline or amorphous structure. This could occur in the heat exchanger or after him. The deposition may take place in the liquid phase or in the form of deposits or deposits on the wall of the tube or vessel. By providing a relevant large surface, for example, by using nozzles and nozzle bodies and/or the appropriate long residence time in the tank, which should be the target deposition, the deposition process can be arranged particularly effective. Mainly, you can refer to the General knowledge in the art of crystallization.

The deposition of fumaric acid, and other undesired components may be carried out in continuous or batch mode.

To further improve the deposition of fumaric acid from the cooled or concentrated by evaporation of part of the absorbent agent flow, if necessary, is preferred cooled or concentrated flow prior to its further transmission of the first still hold through reservoirs is to complete the process. This tank should preferably have a large internal surface area, to further promote the deposition of fumaric acid. Suitable for this purpose, the devices are, for example, tanks, filled with liners or sleeves. If necessary, they can in a short time be removed from the stream and cleaned. For cleaning accepted calculation methods described below to remove precipitated fumaric acid.

In a preferred embodiment of the invention for the deposition and separation of fumaric acid used tanks with internal nozzles. The purpose of the Packed items is, in particular, to provide adequate surface for deposition of the fallen, and, therefore, already in the presence of particles fumaric acid, or drop-down fumaric acid and, therefore, fumaric acid, which is deposited on the surface of the still dissolved state. Thus, especially preferred are Packed items with a large specific surface. The share of unfilled volume in the vessel should preferably be from 30 to 99.5% and preferably from 90 to 99%. Specific surface area is preferably from 50 to 2000 m2/m3and particularly preferably from 250 to 1200 m2/m3. For this purpose can be used, for example, traditional bulk liners, nozzles or wire mesh from steel, ceramic, porcelain or polymer, preferably stainless steel. The surface of the Packed items and vessel walls may be smooth or rough. For the Packed items can also be used caloricity metal or metal sieve cloth. The direction of injection of the Packed items is any, but preferably vertical or horizontal. If applied to the nozzle, the angle of bending structures with cross-channels must have the location of 10° to 80°, preferably from 40° to 60° with respect to the direction of the internal thread.

If volume is used for the deposition, provided with supplementary elements, it is preferably in the apparatus in which cooling and/or concentrated by evaporation of part of the absorbent agent, or in the direction of flow after this device.

The average residence time in the tank with the nozzle elements is preferably from 0.05 to 6 hours, particularly preferably from 0.1 to 2 hours, and most preferably from 0.2 to 1 hour. The velocity of the flow in this case is preferably from 0.0005 to 1.0 m/s and particularly preferably from 0.001 to 0.1 m/s Reservoir exp is watermedia thus, that by adjusting the velocity of the flow and the specific surface area is obtained such hydrodynamic regime, which sets the deposition of precipitated, suspended and/or coagulated particles on the inner surface.

In a separate embodiment of the invention, the nozzle elements with different specific surface applied and installed in such a way that the specific surface in the direction of the flow increases, and this specific surface area is increased by a value of from 1.5 to 10 times, preferably from 2 to 5 times. In another separate embodiment of the invention, the nozzle elements are arranged in such a way that between the nozzle elements are free spaces for submission or selection of liquids.

In another particular embodiment of the invention described above the tank with the nozzle elements can also be an absorption of the structural element from stage (a), according to which stage (f) is cooled and saturated absorbent agent from stage (d) fully or partially fed back to the step (a). In this case, the absorption of the structural element, which may be designed, for example, in the form of so-called absorption column, in the area of supply depleted absorbent agent preferably had the s-force elements, such as those described in the above paragraphs, concerning reservoirs with supplementary elements.

Then fumaric acid (and also other drop-down side products), deposited by operations in stage (d) in the form of solids, partially or completely removed from the reverse flow of absorbent agent at stage (e) in continuous or batch mode. As a rule, at the stage (e) remove from 5 to 100%, preferably from 20 to 100% and particularly preferably from 50 to 100% fumaric acid precipitated in the form of solid substances by means of the operations in stage (d). Preferably at stages (d) and (e) use the apparatus, which can be in continuous or batch mode to remove precipitated fumaric acid from reverse flow absorbent agent, depleted on the content of maleic anhydride in continuous flow. In the case of purposefully used the Packed items in the absorption of structural element of stage (a) cleaning it is advisable to carry out with the standard prescribed mode of operation stop of the equipment.

Remove precipitated fumaric acid can be carried out in various ways, for example, mechanically, physically, thermally or chemically. So, besieged fumaric acid may, for example, mechanical SOS is to rebates from the surface, it was besieged. In addition, it is also possible after unloading absorbent agent from the corresponding reservoir to dissolve precipitated fumaric acid physical method, for example, in water, preferably warm or hot water. However, due to less good solubility in water, as a rule, more preferably chemically translate besieged fumaric acid salt is readily soluble and dissolve this salt. This is done, for example, by using washing water base, preferably aqueous sodium hydroxide solution. In addition, it is also possible to thermally burn besieged fumaric acid in the presence of oxygen. If fallen into the sediment fumaric acid in the absorbent agent is present in the form of a suspension or suspended, it can be separated, for example, by using a filter, sump, a centrifugal separator or a centrifuge. Especially preferred are, depending on the design of the apparatus, in which is deposited fumaric acid, washed by dissolving in aqueous sodium hydroxide solution or mechanical removal by scraping.

As for the hardware design precipitation and separation of fumaric acid with the preferred cooling, mainly special value what are the three basic principles, which, of course, can also be combined. They further explained in more detail.

A) In the first embodiment, hardware design stages (d) and (e) use the apparatus having at least two parallel zones of deposition, in which continuous current through at least one of these areas of deposition flux absorbing agent, depleted on the content of maleic anhydride, at least one of the other zones precipitation can remove deposited fumaric acid in periodic mode.

The simplest form of this is the use of specifically two parallel zones of deposition. Special jargon it comes to the design of A/C. In this case, for example, the first absorbent agent that you want to impoverish the content of fumaric acid, is carried out only through the zone of deposition And in which it is cooled, and fumaric acid falls. If the area of deposition And fell a sufficient amount of fumaric acid, it is possible to switch on an area of deposition, and then remove precipitated fumaric acid from the zone of deposition of A. Then, if the area of precipitation fell In enough fumaric acid, then again switch on ready to operate the zone of deposition of A.

Alternatively, both the areas of deposition and also the parallel be used for deposition of fumaric acid. If one of the two zones of precipitation fell a sufficient amount of fumaric acid, it can be removed after switching to another zone of deposition. Then, after cleaning the area deposition can again be connected in parallel. Naturally, in the preferred embodiment, both the deposition zone are operated in such a way that the cycles of their work respectively displaced relative to each other.

In accordance with the foregoing description of the structural design And/, of course, you can also use more than two parallel zones of deposition (hereinafter referred to as n deposition zones). In this case, for deposition of fumaric acid, preferably in parallel using n-1 zone deposition or all n zones of deposition. If one of the zones of precipitation fell a sufficient amount of fumaric acid, it can be detached for cleaning. If you are ready for operation not used area of deposition, then can be connected to this zone. After cleaning off the area of deposition, it can either be directly connected again or be on standby until then, until you turn it off one of the other zones of deposition. Naturally, in the preferred embodiment, in the case of more than two zones of deposition, they are operated in such a way that the cycles of their work is respectively displaced relative to each other.

A special advantage of this first variant of instrumentation is that this method can be carried out without interrupting the target deposition fumaric acid. The disadvantage of this is that required at least two parallel zones of deposition. However, this disadvantage does not matter, if for technical reasons you have or use a parallel installation. As the preferred versions for these purposes include use of air coolers with multiple partitions.

In the case of the second variant of instrumentation in the stages (a) and (e) use the apparatus with a bypass, in which a continuous flow of absorbent agent, depleted on the content of maleic anhydride, through a bypass line of the apparatus can periodically remove deposited fumaric acid.

In this embodiment, the absorbent agent that you want to impoverish the content of fumaric acid, carried out through the area of the deposition apparatus. If it had deposited a sufficient amount of fumaric acid, the machine will shut off for cleaning, and the absorbent agent is carried out by, through a bypass line of the apparatus. Then reattach the device after cleaning.

Alternatively, also is possible to continuously apply the part of the absorbent agent, want to impoverish the content of fumaric acid, through the bypass. Set for the deposition apparatus is thereby loaded with only slight fluid flow, and, therefore, can also be designed for smaller settings. For the same cooling power due to small stream absorbent agent can be achieved with lower temperatures, which leads to greater relative allocation of fumaric acid. If the machine must be cleaned, then for a short time the entire flow is diverted through the bypass.

In some designs, the area of deposition can also be integrated into one of the available devices, preferably in the apparatus for the absorption of maleic anhydride.

A special advantage of the second variant of instrumentation is that you need only one device with an area of deposition. However, the disadvantage of this is that in the process of refining this device, can not happen the target deposition of fumaric acid. However, using the fast and simple purification procedure disconnected device this disadvantage can be greatly mitigated.

(C) In the case of the third variant of instrumentation in stages (d) and (e) use the apparatus in which when a continuous flow of absorbent agent, depleted of postergenius maleic anhydride, in continuous or batch mode, you can delete deposited fumaric acid during continuous operating zone of deposition.

These include, for example, devices that are in continuous operation soskrebajut and assign fumaric acid, deposited on the surface, in a continuous or intermittent mode, as, for example, in the case of known, conventional mold cooling and internal cooling rollers. In addition, it also includes apparatus in which the drop-down fumaric acid is formed in the form of suspension or suspension from which it can then be separated using mechanical and physical methods, such as, for example, by using a filter, sump, a centrifugal separator or a centrifuge.

A special advantage of the third variant of instrumentation is that you need only one device with an area of deposition, and it may be operated continuously without shutting down and separate treatment. However, the disadvantage of this is the slightly increased hardware complexity due to the use of special apparatus such as, for example mold, filter, sump, a centrifugal separator or a centrifuge.

When selecting equipment for deposition of fumaric acid is particularly preferable to relate to each other the above advantages and disadvantages from the point of view of the whole system.

Absorbent agent from stage (d), depleted in content fumaric acid, at stage (f) is completely or partially returns to the step (a). As a rule, at the stage (f) is recycled back to the step (a) from 10 to 100%, preferably from 50 to 100% and particularly preferably from 90 to 100% absorbent agent, depleted on the content of fumaric acid from stage (d). From the point of view of loss of fumaric acid, as a rule, it can be returned to the step (a) without pre-heating, as a result of supersaturation in the technically relevant timescale able to fall fumaric acid, as a rule, already besieged. However, if necessary, for example, to achieve the desired flow temperature in the absorption column, nothing prevents the heat.

With the method according to the invention the crude mixture of products that should be used in stage (a), containing the anhydride of maleic acid, can be obtained at the preliminary stage by heterogeneous catalytic oxidation with molecular oxygen of a hydrocarbon selected from the group of benzene, n-butane, n-butene and 1,3-butadiene, in the presence of a catalyst containing vanadium, phosphorus and oxygen. Typically, heterogeneous catalytic oxidation is carried out in shell-and-tube reactor. Methods of oxidation of n-butane is described, for example,in the publication Ullmann''s Encyclopedia of Industrial Chemistry, 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, "Maleic and Fumaric Acids - Maleic Anhydride".

Thus obtained crude mixture of products then at stage (a) is extracted with a suitable organic solvent as an absorbent agent.

The crude mixture of products containing the anhydride of maleic acid, may be brought in contact with the solvent (absorbent agent) in a variety of ways, preferably at pressures of from 0.08 to 1 MPa and a temperature of from 50 to 300°C for one or more stages of absorption: (i) by filing a gas stream in a solvent (for example, through a nozzle for introducing a gas or a ring bubbler), (ii) by spraying solvent into the gas stream or (iii) using the contact in countercurrent flow between going upstairs gas stream and moving down stream of the solvent in tray or Packed column. In all three variants can be used well-known specialist devices for the absorption of gases. When applying solvent (absorbent agent) should pay attention to the fact that it has not entered into reaction with the original product used by the anhydride of maleic acid. Moreover, due to the subsequent separation of maleic anhydride from absorbent agent should pay attention to the corresponding difference in the boiling points of absorbent agent and the anhydride is alienboy acid. Preferably the organic solvent at atmospheric pressure has a boiling point at least 30°C higher than the anhydride of maleic acid.

Suitable absorbing agents are, for example, esters of phosphoric acid (for example, tricresylphosphate), esters of maleic acid (for example, dibutylated, butylmalonate), high molecular weight waxes, aromatic hydrocarbons with molecular weight between 150 and 400 g/mol and having a boiling point above 140°C (for example, dibenzyline), esters of phthalic acid (e.g., alkylphenate and diallylphthalate containing alkyl groups with carbon atoms of 1 to 18, for example, dimethylphthalate, diethylphthalate, di-n-propietat, Diisopropylamine, di-n-butylphthalate vondelstraat, methylphthalic, ethylphthalate, n-propietat, isopropylmalate, butylphthalate, undeciphered), complex dialkyl ethers of other aromatic and aliphatic dicarboxylic acids with the number of carbon atoms in the alkyl from 1 to 4 (for example, dimethyl-2,3-naphthalenyloxy, dimethyl-1,4-cyclohexanedicarboxylate), complex alkalemia esters of other aromatic and aliphatic dicarboxylic acids with the number of carbon atoms in the alkyl from 1 to 4 and long-chain fatty acids containing, for example, from 14 to 30 carbon atoms, high-boiling ethers (for example, issue the Oh dimethyl ether polyethylene glycol or a simple dimethyl ether of tetraethyleneglycol).

Preferably use esters of phthalic acid, particularly preferably diallylphthalate with the number of carbon atoms in the alkyl from 1 to 12 and most preferably di-n-butylphthalate.

The solution resulting from the absorption stage (a)generally has a content of maleic anhydride from about 5 to 400 g/L.

The residual gas stream after the absorption stage (a) in addition to water mainly contains by-products prior to oxidation, such as carbon monoxide, carbon dioxide, unreacted source hydrocarbons, as well as acetic acid and acrylic acid. The exiting gas stream substantially free of maleic anhydride.

Then, in stage (b) the anhydride of maleic acid is separated from the obtained at stage (a) absorbent agent, enriched in the content of maleic anhydride. The separation is preferably effected by distillation with a suitable gas, in particular hydrogen, or by distillation.

Stripping with hydrogen is particularly advantageous when the anhydride of maleic acid then may be subjected to hydrogenation to tetrahydrofuran, 1,4-butanediol and/or gamma-butyrolactone. In this case, the distillation is preferably carried out at a temperature of from 100 to 250°C and absolute giving the situation from 0.08 to 3 MPa, moreover, the pressure is preferably in the field of up to 10% greater than the pressure in the subsequent hydrogenation. In the column for distillation, generally follow such a temperature profile, which is obtained from the boiling maleic anhydride in the upper part of the column and the absorbent agent, almost not containing maleic anhydride, cubed columns with a corresponding pressure in the column and the prescribed dilution with carrier gas (hydrogen). To prevent loss absorbing agent, the place of supply of absorbent agent, enriched in the content of maleic anhydride, can be built-in items for rectification.

Alternatively, the Stripping with hydrogen anhydride of maleic acid dissolved in the absorbent agent can be separated in the apparatus for distillation at an absolute pressure of generally from 0.001 to 0.5 MPa and temperatures from 65 to 300°C. When the distillation may be conducted in one or several stages, for example, in apparatus for the separation having one or more steps such as, for example, columns with multiple stages of separation, for example, distillation columns, columns with inserts, columns with bubble cap plates or Packed columns.

Preferably in stage (C) who is rasaut back to the step (a) from 50 to 100% and particularly preferably from 90 to 100% absorbent agent, depleted at the stage (b) on the content of maleic anhydride.

In the main method of carrying out the process of the absorbent agent is released from maleic anhydride, is first subjected to degassing, and then in the air the fridge is cooled to a temperature slightly above the temperature required at the next stage of the absorption process. This temperature is chosen in such a way that has not yet happened deposition of fumaric acid in the absorbent agent, enriched in its content. At the following stage of cooling, which can be made in the form of air or water fridge, now in the deposition of fumaric acid, produce cooling to a temperature that causes the difference between the concentration of fumaric acid in the reverse flow at the outlet of the desorption column (FC, at the outlet of the desorption column) under the existing conditions, expressed in ppm, mass., and the equilibrium concentration of fumaric acid corresponding to the solubility curve, after cooling (FC, equilibrium, after cooling), expressed in ppm, mass., component value is greater than or equal to 250 ppm of the mass. Due to this loss of fumaric acid can be adjusted so that only this unit must be cleaned at regular intervals lying is neither. Stop operation of all equipment can be prevented by the execution of this refrigerator according to the principle of the connection of the a/C.

If after precipitating the fridge is only part of the flow, it can additionally be reduced. In addition, for a short interval at the cleaning stage of crystallization can simply be dispensed with, and thus preventing the execution of the scheme A/C. Also in this case, the fridge may be in the form of a single refrigerator or that, as a rule, is more effective as a combination air cooler with cross ventilation and cooler with precipitation, as described in the previous paragraph.

If the available equipment, whose main refrigerator consists of several parallel lines, as in the case of air cooling in the form of separate sections, using throttle valves of the individual sections can be achieved is also very simple and efficient deposition of fumaric acid: section adjusted by means of the throttle valve is cooled noticeably stronger, and fumaric acid deposition occurs very effectively, while the warmer the main section largely remains clean from deposits. Contaminated section in this case can also be cleaned of th is branch of butterfly valves in the inlet and outlet pipes, in operation, the main section without interrupting the process.

The method according to the invention makes possible a significant reduction in the formation of deposits of fumaric acid on the equipment elements, and also caused thereby clogging, installation and cleaning of equipment, and off when receiving maleic anhydride, and this method can be carried out at relatively low technical complexity, and the disadvantages known from the prior art can be avoided.

Examples

Example 1 (according to the invention)

In theoretical example di-n-butylphthalate depleted on the content of maleic anhydride selected from Cuba desorption column at a temperature of 150°C. the Concentration of fumaric acid is 2500 ppm of the mass. Reverse flow is fully served in the air cooler, having ten equal sections. 50% heated to 150°C flow is conducted through the two sections and is cooled to 100°C. the Other 50% are held in four sections and cooled to 50°C. in four sections deposited part of fumaric acid, and the concentration of dissolved fumaric acid (determined by sampling using the already described membrane filter with a pore size of 0.2 micrometer) is reduced to 2000 ppm of the mass. Then both streams are combined into a single stream, is within the temperature 75°C and the concentration of dissolved fumaric acid 2250 ppm mass., and served in the absorption column. The process of changing the concentration of fumaric acid passed through the four sections of the flow shown schematically in figure 2. The equilibrium concentration of fumaric acid, the corresponding solubility curve after cooling to 50°C (FC, equilibrium, after cooling/evaporation) is approximately 400 ppm of the mass. Therefore, the difference (FC, at the outlet of the desorption column) minus C (FC, equilibrium, after cooling/evaporation) is about 2100 ppm mass.

Once in four sections, used for cooling up to 50°C, for the deposits of fumaric acid significantly increased resistance to flow, under conditions of continuous operation switch to the other four sections, and covered with fumaric acid section is cleaned by an aqueous solution of caustic soda or hot water.

The experimental process for examples 2 through 5

For experimental examples 2 to 5 was used experimental equipment in laboratory scale. Figure 3 shows a simplified diagram of this experimental equipment. Dibutyl phthalate was subjected to enrichment of fumaric acid in a vessel with a mixing device (1), which had a capacity of 8 liters, at a temperature of from 95°C to 120°C, with a pump (2) through the filter, which (3) was cooled in a refrigerator (4) to a temperature from 30°C to 70°C and passed through the land to complete the process (5). The site for the passage of process consisted of 2 glass tubes with an inner diameter of 30 mm Glass tubes were respectively filled with nozzles (Kuhni Rombopak 9M), with a layer height of the nozzle 2×1 m To maintain a constant temperature vessel with a stirrer and glass tubes were made with double walls. After the site for the passage of process solution again was served in a vessel with a stirrer and were enriched by fumaric acid. At the polling process in the establishment of supersaturation according to the invention fumaric acid was partially deposited. Sampling to determine the concentration of fumaric acid was carried out to the refrigerator (Q1) and after section to complete the process (Q2). In a vessel with a stirrer were always so much fumaric acid to precipitate.

Example 2 (according to the invention)

The experiment was carried out with a mixture of dibutyl phthalate and fumaric acid. The saturation concentration of fumaric acid in solution at 50°C was 250 ppm of the mass. The equipment for the experiment was set volumetric flow rate of 15.7 l/h, which corresponded to the time spent on the site to complete the process of 0.09 h or, respectively, the flow rate 0,00617 m/C. In a vessel with a stirrer was set temperature of 100°C. at the outlet of the refrigerator 50°C. The concentration of fumaric acid, measured in front of the fridge, amounted to 657 ppm mass. Therefore, the difference of the concentrations (in front of the fridge) - s (saturation at 50°C after the refrigerator) amounted to 407 ppm mass. The concentration of fumaric acid after polling process proceeds amounted to 359 ppm mass. Thus, at the polling process was besieged 298 ppm, mass.

Example 3 (Example for comparison)

The experiment was carried out with a mixture of dibutyl phthalate and fumaric acid. The saturation concentration of fumaric acid in solution at 50°C was 250 ppm of the mass. The equipment for the experiment was set volumetric flow rate of 15.7 l/h, which corresponded to the time spent on the site to complete the process of 0.09 h or, respectively, the flow rate 0,00617 m/C. In a vessel with a stirrer was set temperature of 115°C. at the outlet of the refrigerator 50°C. the Concentration of fumaric acid, measured in front of the fridge, amounted to 435 ppm mass. Therefore, the difference of the concentrations(in front of the fridge) - s (saturation at 50°C after the refrigerator) amounted to 185 ppm mass. The concentration of fumaric acid after polling process proceeds amounted to 416 ppm mass.

Taking into account the accuracy of the measurements and analysis, this example shows that in certain conditions produced the runs less fumaric acid deposition at the site to complete the process.

Example 4 (according to the invention)

The experiment was conducted with a solution of used industrial equipment to produce maleic anhydride (concentration of dibutyl phthalate >98.5% of the mass). The saturation concentration of fumaric acid in solution at 30°C was 250 ppm of the mass. The equipment for the experiment was set volumetric flow rate of 3.5 l/h, which corresponded to the time spent on the site to complete the process 0,404 h or, respectively, the flow rate 0,00138 m/C. In a vessel with a stirrer was set temperature of 120°C, the output from the refrigerator 30°C. the Concentration of fumaric acid, measured in front of the fridge, was 1043 ppm mass. Therefore, the difference of the concentrations(in front of the fridge) - s (saturation at 30°C after the refrigerator) amounted to 793 ppm mass. The concentration of fumaric acid after polling process proceeds amounted to 634 ppm mass. Thus, at the polling process was besieged 409 ppm mass.

Example 5 (according to the invention)

The experiment was conducted with a solution of used industrial equipment to produce maleic anhydride (concentration of dibutyl phthalate >98.5% of the mass). The saturation concentration of fumaric acid in solution at 50°C was 400 ppm, mass. The equipment for the experiment which was set volumetric flow rate of 3.5 l/h, which corresponded to the time spent on the site to complete the process 0,404 h or, respectively, the flow rate 0,00138 m/C. In a vessel with a stirrer was set temperature of 95°C. at the outlet of the refrigerator 50°C. the Concentration of fumaric acid, measured in front of the fridge, made FROM ppm mass. Therefore, the difference of the concentrations (in front of the fridge) - s (saturation at 50°C after the refrigerator) amounted to 730 ppm mass. The concentration of fumaric acid after the polling process was 1059 ppm mass. Thus, at the polling process was besieged 71 ppm of the mass.

1. A method of reducing the formation of deposits of fumaric acid in obtaining maleic anhydride by heterogeneous catalytic oxidation with molecular oxygen of a hydrocarbon selected from the group of benzene, n-butane, n-butene and 1,3-butadiene, in the presence of a catalyst containing vanadium, phosphorus and oxygen, including:
(a) absorption of maleic anhydride from crude mixture of products absorbing agent containing an organic solvent in the absorption column;
(b) desorption maleic anhydride from absorbing agent obtained in stage (a), enriched with maleic acid anhydride, in the desorption column; and
(c) the full and the partial return to the step (a) absorbent agent, depleted at the stage (b) on the content of maleic anhydride, characterized in that
(d) full or partial amount of absorbent agent, depleted at the stage (b) on the content of maleic anhydride, necessary for the deposition of fumaric acid is cooled and/or subjected to concentration by evaporation of part of the absorbent agent in such an extent that the difference between the concentration of fumaric acid in the reverse flow at the outlet of the desorption column (FC, at the outlet of the desorption column) under the existing conditions, expressed in parts by weight per million), and the equilibrium concentration of fumaric acid corresponding to the solubility curve, after cooling and/or evaporation of part of the absorbent agent (FC, equilibrium, after cooling/evaporation), expressed in parts by weight per million) is greater than or equal to 250 parts by weight per million, and for the precipitation and separation of fumaric acid is used the tank with built-Packed items, and the average time of stay in the tank with built-Packed elements ranges from 0.05 to 6 hours;
(e) fumaric acid, precipitated as solids due to the operations in stage (d), fully or partially, in a continuous or periodic mode is removed from the reverse flow of absorbent agent; and
(f) depleted in content is of fumaric acid absorbing agent from step (e) wholly or partly returned to the step (a).

2. The method according to claim 1, characterized in that in stage (d) average duration of stay in the tank with built-Packed elements is from 0.1 h to 2 hours

3. The method according to claim 1, characterized in that in stage (d) full or partial amount of absorbent agent, depleted at the stage (b) on the content of maleic anhydride, for targeted deposition of fumaric acid is cooled and/or subjected to concentration by evaporation of part of the absorbent agent in such an extent that the difference(FC, at the outlet of the desorption column) - C (FC, equilibrium, after cooling/evaporation) is a value greater than or equal to 500 parts by weight of/million

4. The method according to claim 1, characterized in that all the reverse flow of the absorbent agent produce cooling to the lowest temperature in stage (d).

5. The method according to claim 1, characterized in that in stage (d) is cooled to a temperature in the range from 10 to 100°C.

6. The method according to claim 1, characterized in that in stage (d) and (e) use the apparatus, which can be in continuous or batch mode to remove precipitated fumaric acid from reverse flow absorbent agent, depleted on the content of maleic anhydride in continuous flow.

7. The method according to claim 1, characterized in that in stage (d) and (e) use the apparatus having at least DV is parallel zones of deposition, with continuous current through at least one of these areas of deposition flux absorbing agent, depleted on the content of maleic anhydride, at least one of the other zones precipitation can remove deposited fumaric acid in periodic mode.

8. The method according to claim 1, characterized in that in stage (d) and (e) use the apparatus with a bypass, in which a continuous flow of absorbent agent, depleted on the content of maleic anhydride, through a bypass line of the apparatus can periodically remove deposited fumaric acid.

9. The method according to claim 1, characterized in that in stage (d) is cooled and/or subjected to concentration by evaporation of part of the absorbent agent is from 5 to 100% absorbent agent, depleted on the content of maleic anhydride in stage (b).

10. The method according to claim 1, characterized in that in stage (f) is recycled back to the step (a) from 50 to 100% absorbent agent, depleted on the content of fumaric acid from stage (d).

11. The method according to claim 1, characterized in that the organic solvent to be used in stage (a) for the absorption of maleic anhydride from crude mixture of products is used diallylphthalate with the number of carbon atoms in the alkyl from 1 to 12.

12. Spasibo one of claims 1 to 11, characterized in that in stage (C) is recycled back to the step (a) from 50 to 100% absorbent agent, depleted at the stage (b) on the content of maleic anhydride.



 

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FIELD: chemistry.

SUBSTANCE: method is realised by heterogeneous catalytic oxidation of carbon by molecular oxygen, selected from group of benzol, n-butane, n-butene, in presence of catalyst, which contains vanadium, phosphorus and oxygen, which includes: (a) maleic acid anhydride absorption from impure mixture of products by absorbing agent, which contains organic solvent, in absorption column; (b) desorption of maleic acid anhydride from absorbing agent, which is obtained at stage (a), enriched by maleic acid anhydride, in desorption column; as well as (c) total or partial return to stage (a) of absorbing agent, depleted at stage (b) by content of maelic acid anhydride, is differ in fact, that (d) total or partial quantity of absorbing agent, depleted on stage (b) by content of maelic acid anhydride, for required sedimentation of fumaric acid is cooled and/or subjected to concentration by evaporating absorbing agent to such degree, that difference between concentration of fumaric acid in reverse flow at output from desorption column c (FA, at output from desorption column) at there existing conditions, expressed in weight p/mln, and balanced concentration of fumaric acid, corresponding to solubility curve, after cooling and/or evaporation of absorbing agent part c (FA, balanced, after cooling/steaming), expressed in weight p/mln, constitutes value larger or equal 250 wt, p/mln, and for sedimentation and separation of fumaric acid applied is reservoir with built-in nozzle elements, and average time of staying in reservoir with built-in nozzle elements constitues from 0.05 to 6 hours; (e) fumaric acid, precipitated in form of solid substance due to operations at stage (d), totally or partially, in continuous or periodic mode is removed from reverse flow of absorbing agent; and (f) depleted by content of fumaric acid absorbing agent from stage (e) totally or partially returns on stage (a).

EFFECT: reduction of formation of fumaric acid sedimentations with obtaining maelic acid anhydride.

12 cl, 3 dwg, 5 ex

FIELD: chemistry.

SUBSTANCE: invention relates to an apparatus for producing maleic acid anhydride via heterogeneous catalytic gas-phase oxidation of an initials stream containing hydrocarbons with at least 4 carbon atoms per molecule, which includes a reactor with a bundle of reaction tubes in which there is a solid-phase catalyst on which an exothermic reaction of the initial stream and an oxygen-containing stream occurs, one or more pumps and one or more heat exchangers mounted outside the reactor, through which a heat carrier flows, which is a molten salt which follows through the space between the reaction tubes, thereby receiving the reaction heat, wherein temperature of the molten salt lies in the range between 350 and 480°C. The reaction tubes are made of heat-resistant alloy steel containing at least 0.25 wt % molybdenum, or at least 0.5 wt % chromium and at least 0.25 wt % molybdenum.

EFFECT: apparatus is characterised by high stability.

5 cl, 4 ex

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing raw maleic anhydride. In particular, method includes steps where: reactor output stream, containing maleic anhydride, is fed into bottom part of absorption column, where it comes into contact with a non-cyclic solvent, that is fed close to its upper part and is a diester, having a boiling point under normal conditions between 250 °C and 350 °C, solubility of fumaric acid at least 0.06 wt% at temperature of 60 °C, solubility of maleic anhydride at least 10 wt% at temperature of 60 °C, water solubility not higher than 100 mg/l, density, different from water density at least to 0.020 g/ml, and a water-soluble hydrolysis product with molecular weight not higher than that of pentanol, with transfer of maleic anhydride of outlet stream of reactor into a solvent, wherein gas stream to be extracted is blown off from absorption column, and enriched solvent, containing maleic anhydride, is removed from absorption column near bottom of absorber and directed into flash tower near its middle part, untreated maleic anhydride is removed from stripping column near its middle or upper part.

EFFECT: methods make it possible to use cheaper solvent than phthalates.

11 cl, 1 dwg, 1 tbl

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