JP2012229197A - Production method of propylene oxide, and production apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new production method of propylene oxide which is superior in the productivity of propylene oxide and to provide a production apparatus therefor.SOLUTION: The method for producing propylene oxide includes: (1) a first reaction step of obtaining a first reaction mixture which comprises hydrogen peroxide by reacting hydrogen with oxygen in a solvent in the presence of a palladium catalyst in a first reactor (10); (2) a second reaction step of obtaining a second reaction mixture which comprises propylene oxide by reacting the first reaction mixture and propylene in the presence of a solid titanium catalyst in a second reactor (12); and (3) a return step of returning the second reaction mixture to the first reactor. The steps (1) to (3) are repeated. During that period, a part of the first reaction mixture and a part of the second reaction mixture are taken out to the outside of the system, and propylene oxide included in the same is recovered.

Description

  The present invention relates to a method for producing propylene oxide and an apparatus therefor. Specifically, the present invention relates to a method for producing propylene oxide by reacting hydrogen peroxide with propylene and an apparatus for the method.

  As a method for producing propylene oxide, a method for producing propylene oxide by reacting propylene, oxygen and hydrogen in the presence of solid catalyst particles in a liquid phase is known. For example, in JP-A-2009-256301, in a reactor, a mixed gas containing oxygen and hydrogen and nitrogen for dilution and propylene are supplied into a mixed solvent of acetonitrile and water and a mixture of a solid titanium catalyst and a palladium-supported catalyst. Thus, a method for producing propylene oxide by reacting them is disclosed.

JP 2009-256301 A

  The above-described method for producing propylene oxide is generally said to be excellent in productivity. In this method, a solid titanium catalyst and a palladium-supported catalyst are mixed and used, but the durability of the solid titanium catalyst may be different from the durability of the palladium-supported catalyst. In this case, when one catalyst reaches its endurance limit, it is impossible to recover or replace or regenerate only the one catalyst, or it is not easy. Is not necessarily preferred.

  Therefore, the problem to be solved by the present invention is to provide a new method for producing propylene oxide excellent in productivity and a production apparatus therefor.

  The above-described problems are obtained by obtaining a first reaction mixture containing hydrogen peroxide in the first reaction step, obtaining a second reaction mixture containing propylene oxide by reacting the first reaction mixture and propylene in the second reaction step, The two reaction mixture is returned to the first reaction step, and the first reaction step is performed again to obtain the first reaction mixture, and then the second reaction step is performed again, and the second reaction mixture obtained thereby is again converted into the first reaction mixture. Returning to the reaction step is repeated to return to the first reaction step, the second reaction step and the first reaction step, during which a part of the first reaction mixture and / or a part of the second reaction mixture is taken out and contained therein. It has been found that by recovering the propylene oxide that is recovered, a solution is obtained by a process for obtaining propylene oxide, i.e. producing propylene oxide.

Accordingly, in the first aspect, the present invention provides:
A method for producing propylene oxide, comprising:
(1) a first reaction step in which in a first reactor, hydrogen and oxygen are reacted in a solvent in the presence of a palladium catalyst to obtain a first reaction mixture containing hydrogen peroxide;
(2) a second reaction step in which a first reaction mixture and propylene are reacted in the second reactor in the presence of a solid titanium catalyst to obtain a second reaction mixture containing propylene oxide; and (3) a second Provided is a method for producing propylene oxide, comprising a return step of returning the reaction mixture to the first reactor, wherein steps (1) to (3) are repeated.

  In a preferred embodiment, while repeating the steps (1) to (3) described above, a part of the first reaction mixture is taken out of the system and the propylene oxide contained therein is recovered. In another aspect, while repeating the above-mentioned steps (1) to (3), a part of the second reaction mixture returned to the first reactor is taken out and the propylene oxide contained therein is recovered. In yet another aspect, both a portion of the first reaction mixture and a portion of the second reaction mixture returned to the first reactor are removed and the propylene oxide contained therein is recovered. These recoveries may be performed in a post-treatment step including any suitable method. In another preferred embodiment, the solvent is a mixed solvent of acetonitrile and water.

  In the present specification, hydrogen and oxygen are consumed in the first reaction step to produce hydrogen peroxide, and hydrogen peroxide and propylene are consumed in the second reaction step to produce propylene oxide and water. Of course, in any reaction step, all of the reaction raw materials are not stoichiometrically converted into the desired reaction product.

  The first reaction mixture is a liquid phase mixture obtained in the first reactor as a result of the first reaction step. Usually, in addition to the solvent, hydrogen peroxide as a reaction product, Reacting raw materials that have not reacted (usually gases dissolved in or dispersed therein (oxygen, hydrogen and optionally nitrogen present)). The second reaction mixture further comprises unreacted propylene and propylene oxide as a product in addition to the components contained in the first reaction mixture. Since the second reaction mixture is returned to the first reactor, the first reaction mixture further comprises propylene oxide produced in the second reaction step and unreacted propylene.

  As can be easily understood, since the first reaction mixture reacts in the second reactor and the second reaction mixture is returned to the first reactor, steps (1) to (3) are repeated as described above. After that, the first reaction mixture and the second reaction mixture contain substantially the same components, but hydrogen peroxide is produced in the first reaction step and consumed in the second reaction step, so that the composition Is different. That is, comparing before and after the second reaction step, the amount of hydrogen peroxide decreases, the amount of propylene also decreases, while the amount of propylene oxide increases.

In the second aspect, the present invention provides:
(A) a first reactor for reacting hydrogen and oxygen in a solvent in the presence of a palladium catalyst to produce a first reaction mixture comprising hydrogen peroxide;
(B) a second reactor that reacts the first reaction mixture with propylene in the presence of a solid titanium catalyst to form a second reaction mixture comprising propylene oxide; and (C) the second reaction mixture is first Provided is an apparatus for producing propylene oxide, comprising a return line returning to a reactor. This production apparatus is suitable for carrying out the method for producing propylene oxide of the present invention.

  In the conventional method for producing propylene oxide, propylene oxide is produced by reacting oxygen, hydrogen and propylene in a single reactor, whereas the method for producing propylene oxide of the present invention (or a production apparatus therefor). Then, a hydrogen peroxide production | generation reaction and a propylene oxide production | generation reaction are implemented in another process (or reactor).

  Therefore, the reaction can be carried out by selecting preferable conditions for each reaction. As a result, it becomes possible to further improve the productivity of production of propylene oxide. Further, since the palladium catalyst and the solid titanium catalyst are used in separate reactors, it is very easy to replace or regenerate each used catalyst with a new catalyst.

FIG. 1 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention. FIG. 2 shows a flow sheet schematically showing another embodiment of the method for producing propylene oxide of the present invention. FIG. 3 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention. FIG. 4 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention. FIG. 5 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention. FIG. 6 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention. FIG. 7 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention. FIG. 8 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention. FIG. 9 shows a flow sheet schematically showing one embodiment of the method for producing propylene oxide of the present invention.

  Next, the method for producing propylene oxide of the present invention will be described in more detail with reference to the drawings. 1 to 9, the same reference numerals are used to mean substantially the same elements. In each figure, an example in which the first reactor is a stirred tank reactor and the second reactor is a fixed bed catalyst reactor is shown. However, both the first reactor and the second reactor are stirred. The reactor may be a tank reactor, the first reactor and the second reactor may be fixed bed catalyst reactors, the first reactor may be a fixed bed catalyst reactor, and the second reactor may be A stirred tank reactor may be used. Referring first to FIG. 1, in the method for producing propylene oxide of the present invention, the first reaction step is performed in the first reactor 10, the second reaction step is performed in the second reactor 12, and the second reactor is performed. A return process is performed by a return line 14 from 12 to the first reactor 10.

  In the presence of a palladium catalyst suspended in 16 in a solvent, a reaction for generating hydrogen peroxide by reacting oxygen and hydrogen (diluted with nitrogen if necessary) as a mixed gas 18 is performed in the first reaction step. To do. This reaction is known per se, and details of the reaction can be referred to, for example, JP-A-10-324507 and JP-A-10-330103. Further, in the method described in Patent Document 1, this reaction can be carried out by using no solid titanium catalyst and propylene.

  In the presence of a solid titanium catalyst, a reaction in which propylene and hydrogen peroxide are reacted to epoxidize propylene to produce propylene oxide is performed in the second reaction step. This reaction is known per se, and details of the reaction can be referred to, for example, JP-A-2005-262164 and JP-A-2010-159245. Further, in the method described in Patent Document 1, this reaction can be carried out without using a palladium catalyst and a mixed gas (oxygen and hydrogen).

  The first reactor 10 is previously supplied with a solvent 16, for example, a mixed solvent of acetonitrile / water, in which a palladium catalyst is dispersed in a suspended state. In this state, the mixed gas 18 is supplied to the first reactor 10, and under a predetermined condition, these undergo a liquid phase reaction to generate hydrogen peroxide. As a result, the first reaction mixture is contained in the first reactor 10. There are 20.

  As can be easily understood, the first reaction mixture 20 comprises, in addition to the solvent, the product hydrogen peroxide, oxygen as a reaction raw material, hydrogen and optionally diluting nitrogen, such as The palladium catalyst is suspended in the first reaction mixture. The first reactor 10 may be any suitable reactor, and for example, an autoclave that is a tank reactor having a stirrer as shown in the drawing is preferable.

  In another aspect, the first reactor may be a fixed bed reactor having a palladium catalyst as a fixed bed, such as a tubular reactor. In this case, the mixed gas and the solvent are supplied to the first reactor to perform the first reaction step.

  The second reactor may be in any form, and may be a single reactor in one aspect, or a multistage reaction in which a plurality of unit reactors are connected in series in another aspect. It may be a vessel. In this case, a reaction raw material containing hydrogen, oxygen, and optionally present nitrogen is supplied to the most upstream unit reactor of the plurality of unit reactors constituting the multi-stage reactor, and the reaction is obtained by the reaction. The mixture is fed to the next unit reactor located downstream thereof to further proceed the reaction, where the reaction mixture obtained by the reaction is further fed to the downstream unit reactor to further proceed the reaction. In this way, the hydrogen / oxygen conversion rate can be increased by repeatedly supplying the reaction to the downstream unit reactor and reacting them. In addition, you may comprise a 2nd reactor so that such a reaction raw material may be additionally supplied through the line which connects between adjacent unit reactors as needed.

  Next, a part of the first reaction mixture 20 produced in the first reactor 10 is supplied to the second reactor 12 through the first reaction mixture line 22. Since the palladium catalyst is contained in the first reaction mixture 20, the first reaction mixture 20 is removed from the first reactor 10 through the filter 24 in order to remove it. For example, a filter such as a cross filter may be provided inside the first reactor 10 as shown in FIG. In another aspect, a line for externally circulating the first reaction mixture 20 in the first reactor 10 is provided, and a solid-liquid separation filter such as a cross filter, a centrifuge, etc. are provided in the line to remove the palladium catalyst. The first reaction mixture 20 may be obtained.

  The second reactor 12 is, for example, a fixed bed reactor preliminarily charged with a solid titanium catalyst as shown in the figure, and the first reaction mixture 20 and propylene 26 from the first reactor 10 are supplied to the second reactor 12. In the illustrated embodiment, propylene 26 is mixed with the first reaction mixture 20 before being supplied to the second reactor 12, and then these are supplied to the second reactor 12. In another aspect, before the second reaction step (or before the second reactor 12), a step (or an apparatus for mixing) the first reaction mixture 20 and the propylene 26 may be provided. Thereafter, the obtained mixture is supplied to the second reaction step (or the second reactor 12).

  In another aspect, the second reactor may be a tank reactor, such as a stirred tank reactor. In this case, propylene is reacted in a state where the solid titanium catalyst is dispersed in the tank reactor containing the first reaction mixture.

  Note that the second reactor may be any type of reactor, and may be a single reactor in one aspect, or in another aspect, a multi-unit reactor in series. It may be a connected multistage reactor. In this case, the first reaction mixture and propylene are supplied to the most upstream unit reactor of the plurality of unit reactors constituting the multi-stage reactor, where they are reacted, and the reaction mixture obtained by the reaction is located downstream thereof. To the next unit reactor to further proceed the reaction, where the reaction mixture obtained by the reaction is further fed to the downstream unit reactor to further proceed the reaction. In this way, the conversion rate of propylene can be increased by repeating the supply and reaction to the downstream unit reactor one after another. In addition, you may comprise a 2nd reactor so that a propylene may be supplied additionally via the line which connects between adjacent unit reactors as needed.

  In the second reactor 12, hydrogen peroxide in the first reaction mixture 20 and propylene 26 react with each other in the presence of a solid titanium catalyst to produce propylene oxide, and as a result, a second reaction mixture is obtained. . As can be readily appreciated, the second reaction mixture comprises oxygen, hydrogen, optional diluent nitrogen, hydrogen peroxide, propylene and propylene oxide.

  Such a second reaction mixture is taken out from the second reactor 12 and returned to the first reactor 10 via the return line 14 to perform a return step, and a part of the first reaction mixture 20 is, for example, the first reaction mixture 20. The first reactor 10 is taken out from the system through the first reaction mixture outside line 30. In the method for producing propylene oxide of the present invention, from the first reactor 10 via the first reaction mixture line 22 to the amount of solvent in the first reaction mixture taken out from the system via the first reaction mixture outside extraction line 30. The ratio of the solvent in the first reaction mixture to be taken out, that is, the ratio of the circulating solvent to the solvent taken out of the system is preferably 1 to 12000, more preferably 10 to 5000, and still more preferably 50 to 500. . By increasing the circulation amount in this way, it is possible to obtain the first reaction mixture and the second reaction mixture containing propylene oxide at a high concentration even when the concentration of hydrogen peroxide in the first reaction mixture is low. It becomes possible. As shown in FIG. 2, a part of the second reaction mixture may be taken out from the return line 14 through the second reaction mixture system take-out line 30 ′, and then the propylene oxide produced in the second reactor may be taken out. Good.

  When returning the second reaction mixture via the return line 14, instead of returning directly to the first reactor 10 as shown in FIG. You may return. For example, as shown in FIG. 3, by connecting the return line 14 to the supply line 40 that supplies the reaction raw material to the first reactor 10, the second reaction mixture is supplied to the first reactor 10 via the supply line 40. Can be returned.

  Another embodiment of the method for producing propylene oxide of the present invention is shown in FIG. In the illustrated embodiment, the first reactor 10 is constituted by a plurality of, specifically, three unit reactors 10-1, 10-2 and 10-3, and a connection line 22-1 and 22-2 exists. A reaction feedstock 18 containing hydrogen, oxygen and optionally present nitrogen is sent to the first unit reactor 10-1, where the reaction takes place to produce a reaction mixture, which is connected via the connection line 22-1 to the first. 2 unit reactor 10-2 where further reaction takes place to form a reaction mixture which is routed via connection line 22-2 to third unit reactor 10-3 where the reaction is Further occurs to produce a reaction mixture that is discharged from the third unit reactor 10-3 via connection line 22-3.

  The connection line 22-3 corresponds to the first reaction mixture line 22 and is discharged from the unit reactor 10-3. Accordingly, the first reaction mixture discharged from the first reactor 10 is supplied to the second reactor 12. In this embodiment, a reaction feed containing hydrogen, oxygen and optionally present nitrogen may be added to at least one connecting line. This embodiment is shown in FIG. Here, the raw material addition lines 18-1 and 18-2 are connected to the connection lines 22-1 and 22-2. The additional supply of the reaction raw material in this way means a divided preparation of the reaction raw material, whereby the reaction rate of the reaction raw material can be adjusted for each unit reactor, and as a result, hydrogen and oxygen and The reaction amount of can be easily adjusted.

  Yet another embodiment of the method for producing propylene oxide of the present invention is shown in FIG. In this embodiment, a portion of the first reaction mixture fed to the second reactor is returned to the first reactor. In the embodiment shown in FIG. 6 (a), the first reaction mixture is directly returned to the first reactor 10 via the circulation line 42. In the embodiment shown in FIG. 6 (b), the first reaction mixture is connected to the supply line 40. The first reaction mixture is indirectly returned to the first reactor 10 via the circulation line 44 formed. Thus, by returning a part of the first reaction mixture to the first reactor 10, a part of the first reaction mixture is circulated, and the amount of catalyst used in the first reactor can be suppressed. In other words, the conversion rate in the first reactor is increased, and as a result, the catalyst use efficiency is increased.

  Yet another embodiment of the method for producing propylene oxide of the present invention is shown in FIG. In the illustrated embodiment, the second reactor 12 is constituted by a plurality of, specifically, three unit reactors 12-1, 12-2 and 12-3, and the connection line 23-1 and 23-2 exists. The first reaction mixture and propylene are sent to the first unit reactor 12-1, where the reaction takes place to form a reaction mixture that is sent to the second unit reaction 12-2 via connection line 23-1. Where further reaction takes place to form a reaction mixture which is routed via connection line 23-2 to the third unit reactor 12-3 where further reaction takes place to form a reaction mixture, It is discharged from the third unit reactor 12-3 via the return line 14. In this embodiment, a reaction raw material containing propylene may be added to at least one connecting line. This aspect is shown in FIG. Here, propylene additional lines 26-1 and 26-2 are connected to connection lines 23-1 and 23-2. When the reaction raw material is additionally supplied in this way, the amount of propylene supplied can be adjusted for each unit reactor, and as a result, the reaction heat can be easily controlled.

  FIG. 9 shows still another embodiment of the method for producing propylene oxide of the present invention. In this embodiment, a portion of the second reaction mixture fed to the first reactor is returned to the second reactor. In the embodiment shown in FIG. 9 (a), the second reaction mixture is returned directly to the second reactor 12 via the circulation line 46, and in the embodiment shown in FIG. 9 (b), the first reaction mixture line is returned. The second reaction mixture is indirectly returned to the second reactor 12 via a circulation line 46 connected to the second reactor 22. Thus, by returning a part of the second reaction mixture to the second reactor 12, a part of the second reaction mixture is circulated, and the amount of catalyst used in the second reactor can be suppressed. In other words, the conversion rate in the second reactor is increased, and as a result, the catalyst use efficiency is increased.

  While repeating the first reaction step, the second reaction step, and the return step in this order, the mixed gas 18 and propylene 26 are supplied to the first reactor 10 in accordance with the amount of the first reaction mixture taken out of the system. And fed to the second reactor 12, respectively. In addition, since the solvent is taken out of the system, makeup solvent 28 is supplied to the first reactor 10. A gas mixture 18, propylene 26 and makeup solvent 18 are fed and a portion 30 of the first reaction mixture is removed to form and maintain a steady state. In another embodiment, makeup solvent 28 may be supplied to first reaction mixture line 22 supplying the first reaction mixture instead of, or in addition to, supplying gas mixture 18.

  As can be easily understood by those skilled in the art, in order to form and maintain a steady state, the supply of the mixed gas 18 to the first reaction step, the first reaction mixture 20 from the first reaction step, and the like. It is preferable that the supply to a part of the second reaction step, the supply of propylene 26, and the return of the second reaction mixture from the second reaction step to the first reactor 10 are carried out continuously. Therefore, it is preferable to carry out steps (1) to (3) in the method for producing propylene oxide of the present invention continuously. In this case, it is particularly preferable that the supply into the system and the discharge out of the system are continuously performed.

  However, it is not always necessary to carry out completely continuously as described above, and it may be carried out intermittently so that the compositions of the first reaction mixture and the second reaction mixture vary within a predetermined range. Good. In yet another aspect, at least a portion of the supply and discharge may be continuous and the other portions intermittent.

  In the method for producing propylene oxide of the present invention, the liquid phase of the first reactor 10, that is, the first reaction mixture 20 includes acetonitrile and water as solvents, hydrogen peroxide produced in the first reaction step, and second reaction step. The hydrogen peroxide that was not reacted in step 1 and returned to it, the propylene oxide produced in the second reaction step and supplied to the first reactor 10, and the first reactor 10 not reacted in the second reaction step Propylene. Of course, the same applies to a part of the first reaction mixture taken out of the system from the first reactor 10 via the first reaction mixture outtake line 30. The first reaction mixture is removed through filter 32 to prevent the removed first reaction mixture from entraining the palladium catalyst and leaving the palladium catalyst out of the system.

  As described above, the first reaction mixture 20 contains, in addition to propylene oxide, oxygen, hydrogen, and optionally present nitrogen, hydrogen peroxide, propylene, and a solvent as other components dissolved or dispersed therein. . Therefore, in order to recover the target propylene oxide from the first reaction mixture 20 taken out via the first reaction mixture outtake line 30, other components are removed in a post-treatment step (not shown). . This post-treatment step may be any suitable treatment. For example, the gas components (nitrogen, hydrogen and oxygen) are first removed by reducing the system pressure. Hydrogen peroxide can be removed similarly. Propylene oxide and solvent may be recovered by distillation under pressure to recover propylene oxide. The second reaction mixture includes substantially the same components as the first reaction mixture, although the composition is different. Therefore, as shown in FIG. 2, even when a part of the second reaction mixture returned from the second reactor 12 toward the first reactor 10 is taken out via the second reaction mixture system extraction line 30 ′. From the part of the second reaction mixture taken out, it is possible to recover the target propylene oxide contained therein. This recovery may be carried out by any suitable treatment, similar to the post-treatment step described above.

As can be easily understood from the above description, the propylene oxide production method of the present invention is characterized in that the second reaction mixture is returned to the first reactor 10. The apparatus for producing propylene oxide of the present invention that can be used in such a production method has a return line 14. That is, the propylene oxide production apparatus of the present invention is
(A) a first reactor for reacting hydrogen and oxygen in a solvent in the presence of a palladium catalyst to produce a first reaction mixture comprising hydrogen peroxide;
(B) a second reactor that reacts the first reaction mixture with propylene in the presence of a solid titanium catalyst to form a second reaction mixture comprising propylene oxide; and (C) the second reaction mixture is first It is characterized by having a return line returning to the reactor.

  In the method for producing propylene oxide of the present invention as described above, the first reaction step for generating hydrogen peroxide is performed in the first reactor, and the second reaction step for generating propylene oxide is performed in the second reactor. In addition, as a result of performing the return step of returning the second reaction mixture to the first reactor, even when the concentration of hydrogen peroxide contained in the first reaction mixture supplied to the second reactor is low, propylene oxide is reduced. It can be obtained efficiently.

Specifically, based on the mass balance, the process for producing propylene oxide of the present invention that performs the return step can be simulated as follows:
Propylene oxide is produced substantially only in the second reactor. When the second reaction mixture containing 10% by weight of propylene oxide is taken out at 1 kg / sec via the second reaction mixture system outtake line 30 ′ as shown in FIG. Propylene oxide needs to be produced at a rate of 0.1 kg / sec. This production rate corresponds to a production rate of 1.7 mol / sec of propylene oxide. Assuming that substantially 100% of the hydrogen peroxide fed to the second reactor is used for the oxidation of propylene, to produce propylene oxide at 1.7 mol / sec, the second reactor is overloaded. It is necessary to supply hydrogen oxide at a rate of 1.7 mol / sec. For example, when the first reaction mixture is supplied at a rate of 90 kg / sec, the concentration of hydrogen peroxide contained in the first reaction mixture at this time is 0.064% by weight (1.7 × 34/90000 = 0). .00064). That is, the concentration of hydrogen peroxide in the first reaction mixture may be 0.1% by weight or less.

  In the case where the return step is not performed, similarly to the above, when taking out the second reaction mixture containing 10% by weight of propylene oxide out of the system at 1 kg / sec, propylene oxide is 0.1 kg / sec in the second reactor. It is necessary to produce at a rate of sec, that is, 1.7 mol / sec. In this case, based on the material balance, it is necessary to supply the first reaction mixture to the second reactor at a rate of 0.9 kg / sec. As before, assuming that 100% of the hydrogen peroxide fed to the second reactor is used for propylene oxidation, to produce propylene oxide at 1.7 mol / sec, the second reactor It is necessary to supply hydrogen peroxide at a rate of 1.7 mol / sec. Therefore, the hydrogen peroxide concentration in the first reaction mixture supplied to the second reactor is 6.4% by weight (1.7 × 34/900 = 0.064).

  That is, when the return step is not performed, the concentration of hydrogen peroxide in the first reaction mixture needs to be considerably higher than when the return step is performed.

10 ... 1st reactor, 10-1 ... 1st unit reactor, 10-2 ... 2nd unit reactor,
10-3 ... 3rd unit reactor, 12 ... 2nd reactor, 12-1 ... 1st unit reactor,
12-2 ... 2nd unit reactor, 12-3 ... 3rd unit reactor,
14 ... return line, 16 ... solvent, 18 ... mixed gas,
18-1, 18-2 ... Raw material addition line, 20 ... first reaction mixture,
22 ... 1st reaction mixture line, 22-1, 22-2 ... Connection line,
23-1, 23-2 ... connecting line, 24 ... filter, 26 ... propylene,
26-1, 26-2 ... Propylene addition line, 28 ... Solvent make-up,
30 ... First reaction mixture system out-take line, 30 '... Second reaction mixture system out-take line,
32 ... Filter, 40 ... Supply line, 42, 44 ... Circulation line,
46 ... circulation line.

Claims (19)

A method for producing propylene oxide, comprising:
(1) a first reaction step in which in a first reactor, hydrogen and oxygen are reacted in a solvent in the presence of a palladium catalyst to obtain a first reaction mixture containing hydrogen peroxide;
(2) a second reaction step in which a first reaction mixture and propylene are reacted in the second reactor in the presence of a solid titanium catalyst to obtain a second reaction mixture containing propylene oxide; and (3) a second A method for producing propylene oxide, comprising a return step of returning the reaction mixture to the first reactor, wherein steps (1) to (3) are repeated.   2. The method for producing propylene oxide according to claim 1, wherein a part of the first reaction mixture is taken out of the system and the propylene oxide contained therein is recovered while the steps (1) to (3) are repeated. .   The method for producing propylene oxide according to claim 1, wherein a part of the second reaction mixture is taken out of the system and the propylene oxide contained in the second reaction mixture is recovered while repeating steps (1) to (3). .   The method for producing propylene oxide according to any one of claims 1 to 3, wherein the solvent is a mixed solvent of acetonitrile and water.   In the return step (3), the second reaction mixture is returned to the first reactor directly or indirectly via a feed line connected to the first reactor. 5. The method for producing propylene oxide according to any one of 4 above.   The method for producing propylene oxide according to any one of claims 1 to 5, wherein the first reactor is a multistage reactor composed of a plurality of unit reactors arranged in series.   The reaction raw material containing hydrogen and oxygen is supplied to the uppermost unit reactor of the multiple unit reactors constituting the multistage reactor, and added via a line connecting adjacent unit reactors. The method for producing propylene oxide according to claim 6, wherein the propylene oxide is supplied continuously.   A portion of the first reaction mixture is removed from the first reaction mixture line that feeds the first reaction mixture from the first reactor to the second reactor, and the feed line to the first reactor directly or to the first reactor is provided. The method for producing propylene oxide according to any one of claims 1 to 7, wherein the method is indirectly returned via a route.   The method for producing propylene oxide according to any one of claims 1 to 8, wherein the second reactor is a multistage reactor composed of a plurality of unit reactors arranged in series.   Propylene is supplied to the uppermost unit reactor of a plurality of unit reactors constituting the multistage reactor, and is additionally supplied via a line connecting adjacent unit reactors. The method for producing propylene oxide according to claim 9, wherein   A portion of the second reaction mixture is removed from the return line that feeds the second reaction mixture from the second reactor to the first reactor and directly to the second reactor or via the feed line to the second reactor. It returns indirectly, The manufacturing method of the propylene oxide in any one of Claims 1-10 characterized by the above-mentioned. (A) a first reactor for reacting hydrogen and oxygen in a solvent in the presence of a palladium catalyst to produce a first reaction mixture comprising hydrogen peroxide;
(B) a second reactor that reacts the first reaction mixture with propylene in the presence of a solid titanium catalyst to form a second reaction mixture comprising propylene oxide; and (C) the second reaction mixture is first An apparatus for producing propylene oxide, comprising a return line returning to the reactor.   The return line is a line for returning the second reaction mixture to the first reactor, either directly or indirectly via a feed line connected to the first reactor. The propylene oxide production apparatus as described.   14. The apparatus for producing propylene oxide according to claim 13, wherein the first reactor is a multistage reactor composed of a plurality of unit reactors arranged in series.   It has a raw material supply line that supplies reaction raw materials containing hydrogen and oxygen to the uppermost unit reactor of a plurality of unit reactors constituting a multistage reactor, and passes through a line connecting adjacent unit reactors. The apparatus for producing propylene oxide according to claim 14, further comprising a raw material addition line for the reaction raw material containing hydrogen and oxygen.   A portion of the first reaction mixture is removed from the first reaction mixture line that feeds the first reaction mixture from the first reactor to the second reactor, and the feed line to the first reactor directly or to the first reactor is provided. The apparatus for producing propylene oxide according to any one of claims 12 to 15, further comprising a line for returning indirectly via the line.   The apparatus for producing propylene oxide according to any one of claims 12 to 16, wherein the second reactor is a multistage reactor comprising a plurality of unit reactors arranged in series.   Propylene has a propylene supply line for supplying propylene to the uppermost unit reactor of a plurality of unit reactors constituting a multistage reactor, and propylene is supplied via a line connecting adjacent unit reactors. The apparatus for producing propylene oxide according to claim 17, further comprising a propylene addition line to be additionally supplied.   A portion of the second reaction mixture is removed from the return line that feeds the second reaction mixture from the second reactor to the first reactor and directly to the second reactor or via the feed line to the second reactor. The apparatus for producing propylene oxide according to any one of claims 12 to 18, comprising a line for returning indirectly.

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