The way counterflow obtain products of the oxidation of cyclohexane

 

(57) Abstract:

The invention relates to a method for producing oxidation products of cyclohexane catalytic liquid-phase oxidation of oxygen-containing gases. Liquid cyclohexane and oxygen-containing gases countercurrent flow through a reaction zone, which is divided into several inter-connected chambers with perforated plates. Oxygen-containing gas is injected along the reaction zone through the nozzle holes, evenly distributed over the cross section of the reaction zone, resulting in the reaction zone does not create a continuous gas phase. The distance of the input gas is 0.1 to 3 times the diameter of the reaction zone. Moreover, the gas is introduced into the reaction zone, where oxygen from the previous input is not fully spent. The temperature in the reactor 120-180oWith the pressure - 5-30 bar. The technical result - reduced formation of by-products, increase in the productivity of the reactor. 9 C.p. f-crystals, 1 table.

The invention relates to a continuous method for producing oxidation products of cyclohexane by catalytic liquid-phase oxidation of oxygen-containing gases, and gases mainly evenly in contact with sirimanne molecular oxygen and, in particular, the oxidation of cyclohexane to cyclohexanol and cyclohexanone known from the prior art. For example, in the application DE 2136744 and in U.S. patent 3957876 describes how to obtain solutions containing cyclohexyl-Gidropress, by oxidation of cyclohexane areas, with a mixture of cyclohexane and soluble catalyst based on cobalt top-down pass through the supplied plates column, and the oxygen-containing gas is fed countercurrent from the bottom up. Column is placed at its upper end zone of oxygen depletion and bottom adjacent to this zone oxidation zone, the latter being made with the possibility of independent feed them oxygen in varying amounts.

The aim of the invention is solely getting cyclohexyl-gidroperekisi, which is obtained with a yield of 15 wt.% in terms of the total number of oxidation products.

In U.S. patent 4675450 describes how to obtain cyclohexyl-gidroperekisi same way according to the application DE 2136744, and the oxidation of cyclohexane is carried out in the presence of a soluble catalyst based on cobalt and complex ester of phosphoric acid.

In the application DE 1287575 described by way of the oxidation of liquid cyclohexane is carried on is the seer gas. When the gas is injected with the provision that at each stage, the feed rate of oxygen mainly corresponds to the flow rate of oxygen, and at the last stage additionally served inert gas. Thus, inevitably turns out uneven feeding and uneven distribution of oxygen in the reaction mixture, resulting in reduced output. The reaction zone is divided into chambers by means of the bent-down plates do not overlap each cross-section. Gas is injected under the said plates in the current down the gas phase subsequent stage of oxidation, which is described as suitable as the reaction with loaded plates" also leads to irregular supply of oxygen, uneven flow of the reaction mixture and in the worst case to the formation filled with the oxygen-containing gas space under the plates, which increases the risk of education capable of combustion and explosion.

In the patent DE 2515419, corresponding to U.S. patent 3987100 described a method of producing cyclohexanone and cyclohexanol by oxidation of cyclohexane in counter-current mode in the supplied plates column in the presence of soluble binary catalyst system, vklyuchyeny, for example, in the form of perforated plates through which the oxygen-containing gas may rise and cyclohexane to drain down.

Similarly, the application DE 1287575 part of the plates or on all plates can also introduce oxygen-containing gas (except oxygen depletion in the upper part of the column). And in this case, the introduction of oxygen is done by ensuring that virtually all the oxygen supplied to each phase of the project is spent at this stage. In addition, the number and/or size of the holes of the perforated plates is increased in the direction from the bottom to the top of the reactor and on the top plates do not enter the oxygen. This means that in the case of this method, as the method according to the application DE 1287575, the introduction of oxygen and its distribution in the reactor, but also the course of the reaction mixture are uneven. Because the spare area of the plates is very small, it is only about 1.2%, and in the case of this method, there is the risk of education under the plates gas-filled spaces, privedhsih to danger of explosion.

None of the above references do not describe the method of obtaining a oxidation products of Ziklag is Ki, resulting in the reactor no longer has a continuous gas phase, and according to which oxygen is introduced into the reaction mixture more evenly.

In the application EP 0135718 described continuous method of oxidation of hydrocarbons in the liquid phase, in particular, the oxidation of cyclohexane, whereby the oxygen-containing gas is introduced into the liquid reaction mixture in some places the reaction zone through the downstream nozzle holes. While the reaction zone is divided into several chambers, and may not form a continuous gas phase. Specifically this can be achieved, for example, by using a bubble column, by means of perforated plates is divided into chambers through which the bottom-up pass with cyclohexane dissolved in the catalyst based on cobalt. Above the perforated plates through the nozzle injected oxygen-containing gas, and owing to well-defined rate of release of gas and the quantity of gas bubbles of a certain size. Due to this, the liquid reaction mixture throughout the reaction zone mostly evenly kontaktirajte with molecular oxygen, and avoid the disadvantages of the method according to the application D through the reactor.

This method requires improvements to the relatively high content of cyclohexane produced gas and selectivity of oxidation relative to the formation of cyclohexanol and cyclohexanone. In particular, it is desirable to reduce the number containing the acid by-products (for example, Caproic acid), which must be removed from the reaction mixture by washing with water and sodium lye, and get the waste water with a high salt content and a high content of organic compounds.

Therefore, the present invention is to develop an improved method of obtaining a oxidation products of cyclohexane, which eliminated the above described disadvantages.

It has been unexpectedly found that the above problem is solved by a method of producing oxidation products of cyclohexane by oxidation of oxygen-containing gases in the liquid phase due to the fact that the liquid cyclohexane and oxygen-containing gases countercurrent flow through a reaction zone with providing a steady supply of oxygen in the reaction environment.

Thus, the object of the invention is a method for oxidation products of cyclohexane by catalytic liquid is Vomero in at least one reaction zone, which differs in that the liquid cyclohexane and oxygen-containing gases countercurrent flow through the reaction zone.

For the implementation of the proposed method is suitable reactors with lying or, preferably, with standing the reaction zones. According to a preferred variant of the reaction zone is divided into chambers, that is, to avoid the effect of reciprocal mixing. If the underlying reaction zones this goal can be achieved, for example, by using overflow or dividing walls with crossing channels, and in the case of standing the reaction zones, for example, by using perforated plates installed at regular distances.

Preferably through these design characteristics in the reaction zone is no longer to form a continuous gas phase.

In the proposed method, unlike the method according to application EP 0135718 liquid cyclohexane and oxygen-containing gases reverse current is passed through the reaction zone.

For oxidation using gases containing molecular oxygen. When the oxygen concentration is preferably from 5 to 30 vol.%. Preferably oxygen-containing gases introduced into the liquid cvline down.

According to a preferred variant of the proposed method the rate of production of oxygen-containing gases from each of the nozzles is from 0.01 to 1 m/s, preferably from 0.03 to 0.3 m/s

Further, preferably the flow rate of each nozzle is from 0.01 to 10 l/s, in particular from 0.1 to 1.0 l/s

Nozzle openings are mostly evenly distributed over the volume of the reaction zone. This is achieved, for example, by placing the nozzle holes in different places of the reaction zone, generally at equal distances, which are evenly distributed over the cross section of the reaction zone.

Preferably the distance along the reaction zone is 0.1 to 3 times the diameter of the reaction zone. In particular, they are selected to ensure that the ascending gas bubbles from the previous place of introduction of the gas molecular oxygen used is still not complete and is, for example, from 60 to 90% of the initial content. Through this event provided mainly uniform spatial distribution of the oxygen-containing gas in the underlying oxidation of cyclohexane. Through each coplowe hole is introduced in essentially the same amount of gas. By combin, is in areas of the reaction zone, in which oxygen from the previous introduction is not yet fully used, is achieved a uniform oxygen concentration in the reactor. This differs method according to the invention described in the application DE 1287575 method and similar methods.

Due to the above introduction of the oxygen-containing gas through the nozzle openings in the liquid phase cyclohexane bubbles having a certain diameter, preferably equal to or greater than 10 mm, for example comprising from 10 to 100 mm Bubbles first have a larger diameter than the "equilibrium" bubbles, in which they raspador during passage through the reaction zone. Under "equilibrium" bubbles understand bubbles formed at a certain distance from the nozzle holes by the collapse or coalescence, and, for example, cyclohexane and air are formed "equilibrium" bubbles with an average diameter constituting about 1 to 10 mm

In a suitable setting for the introduction of oxygen-containing gas may be supplying pipelines with a large number of very small holes, providing a predetermined reduced pressure, and the oxygen-containing gas is fed evenly in every place gas release is to provide the above-described preferred amounts of exhaust gas and the rate of introduction of gas into a liquid reaction medium. This can, for example, to introduce oxygen-containing gas through a small hole in the extended area that is open downwards and closed - with the exception of thin holes on top. Extended area may be cylindrical, conical, rectangular or square shape, or form in the form of a bell or extended at one end of the pipe. While its lower edge may be zigzag or oblique. The geometric shape of the extended zone is selected to meet the above flow rates of gas and quantities discharged from the nozzle of the gas hole, and a specialist will be able to easily calculate it based on the specified data.

Variable oxidation of the cyclohexane to add a catalyst, preferably a catalyst based on cobalt. Suitable catalysts are described, for example, in the patent DE 2515419.

The reaction temperature in the reaction zone ranges from 120 to 180oC, preferably from 130 to 160oC and a pressure of from 5 to 30 bar, preferably from 10 to 20 bar. The pressure and temperature agree with the provision that at any time the interaction proceeds in the liquid phase.

According to a particular variant of the proposed method of obtaining a oxidation products of cyclohexane, and the only consistently included tower reactors. Standing the reaction zone is divided into chambers by perforated plates installed at equal distances. Mostly perforated plates have a free cross-section (the total area of the holes) from 3 to 20%, in particular from 5 to 10%. Above each perforated plate uniformly over the cross section is divided nozzle, and the outlet can be done with extensions, the holes are preferably directed downwards. Through the reaction zone from the top down pass the liquid cyclohexane. At the same time through the nozzle injected oxygen-containing gas. Liquid cyclohexane and oxygen-containing gas is passed through a reaction zone countercurrent, and the exhaust gas is separated in the upper part of the reaction zone. When this interaction is carried out, for example, at a temperature of from about 140 to 160oC and at a pressure of from about 12 to 16 bar.

Proportion of introduced gas containing molecular oxygen, and preferably cyclohexane agree with providing the content of molecular oxygen produced from the reaction zone of the gas not exceeding 2,5 vol.%, for example, of 0.1 to 1.5 vol.%.

Gas output by 40% vol., which after condensation can be recycled to the reactor. Thus, the proposed method is advantageous manner by reducing the concentration of cyclohexane in the produced gas, which in the case of the above reactors, allowing restriction the quantity of waste gas, improves performance, i.e. the maximum attainable conversion of cyclohexane. The temperature of the produced gas is preferably lower than the lowest temperature of the reaction zone.

The processing of the raw product of the oxidation is carried out by known methods, for example, by rinsing with water and/or aqueous liquor as, for example, sodium hydroxide, and the obtained waste water containing acid and/or salt. The separation of the pure product on the main products, namely, cyclohexanol and cyclohexanone, and the allocation of unreacted cyclohexane and formed in a smaller number of further oxidation products carry a conventional method, for example, by fractionated distillation.

The proposed method is the best way enables you to evenly distribute the molecular oxygen in the underlying oxidation of cyclohexane, and does not require extra is>/P>By submitting reagents countercurrent through the reaction zone can avoid the above drawbacks. Increases the overall conversion of cyclohexane, and simultaneously improves the selectivity of the oxidation of the preferred formation of cyclohexanol and cyclohexanone. In particular, by reducing the content of carboxylic acids (Caproic acid) oxidation products decreases the pollution of waste water obtained by washing the crude oxidation product with water and aqueous liquor.

The proposed method is illustrated using the following examples, but is not limited to them.

Example 1 (comparative)

Cyclohexane is subjected to oxidation in an oxidizing system consisting of three series-connected reactors, each with a displacement of 40 m3height 16 m, with a diameter of 1.8 m, the node processing (removal of acid by washing with water and separation, as well as neutralization using sodium liquor) and a node for distillation. The reactor is equipped with a node for uniform air distribution over the cross section and the height of the reactor. The reactor liquid injected gas in 7 levels at a distance of 2 m from each other. To reduce the effect of reciprocal mixing podiatr holes 40 mm, the free space in terms of the cross-section of the reactor 4%). The node for the distribution of gas each level is made in the form of a pipe with a nominal diameter of 32 cm, in the lower side of which is made of 33 holes 3 mm in diameter, uniformly distributed over the cross section of the reactor. Each hole is equipped with a tube length of 60 mm and a diameter of 25 mm, the Rate of production of gas in the work environment is 0.25 m/s In this system reactor in which the pressure of the upper part is approximately 13 bar, bottom at a temperature of 140oServed with 80 t 1 h of cyclohexane, and the reaction is carried out parallel. Before serving in the first reactor to the cyclohexane add 0.1 parts per million of cobalt in the form of salts of ethylhexanoic acid.

Example 2 (according to the invention)

The reaction is carried out in the installation according to example 1, however, a counter, and cyclohexane served on top.

The results of examples are shown in table. 1.

As can be seen from the data table. 1, the oxidation of cyclohexane is significantly improved when the countercurrent method, and there is still the possibility of increasing performance, if in the above reaction the installation to carry out the reaction under optimal conditions, obespechivayuschim catalytic liquid-phase oxidation of oxygen-containing gases at an elevated temperature, moreover, the gases flow and mostly evenly in contact with liquid cyclohexane standing in the reaction zone, characterized in that the gases introduced into the reaction zone through several nozzles, and the reaction zone through the perforated plates is divided into several chambers, resulting in the reaction zone does not form a continuous gas phase.

2. The method according to p. 1, characterized in that the temperature of the exhaust gas is lower than the lowest temperature of the reaction zone.

3. The method according to p. 1 or 2, characterized in that the rate of production of oxygen-containing gases at each nozzle hole is from 0.01 to 1 m/s, preferably from 0.03 to 0.3 m/s, and the quantity of gas each nozzle hole is from 0.001 to 10 l/s, preferably from 0.1 to 1.0 l/s

4. The method according to any of paragraphs.1-3, characterized in that the oxygen-containing gases are injected along the reaction zone at distances equal to from 0.1 to 3 times the diameter of the reaction zone, and the nozzle holes evenly distributed over the cross section of the reaction zone.

5. The method according to any of paragraphs.1-5, characterized in that the reaction zone is divided into several chambers communicated with each is strong in areas, where oxygen from the previous place of introduction is not yet fully used.

7. The method according to any of paragraphs.1-6, characterized in that the reaction temperature is from 120 to 180oC, preferably from 130 to 160oC.

8. The method according to any of paragraphs.1-7, characterized in that the pressure in the reaction is from 5 to 30 bar, preferably from 10 to 20 bar.

9. The method according to any of paragraphs.1-8, characterized in that the concentration of oxygen in the oxygen-containing gas is from 5 to 30 vol.%.

10. The method according to any of paragraphs.1-9, characterized in that the content of cyclohexane in the exhaust gas amounts to a maximum of 45 vol.%, preferably a maximum of 40 vol.%.

 

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