JP2011201823A - Method for producing propylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing propylene oxide, having an industrially effective advantage that a solid catalyst in a state of increasing the differential pressure in the catalyst layer can be reused therein and hence the catalyst cost in producing propylene oxide can significantly be reduced.SOLUTION: The method of producing propylene oxide by causing propylene and a peroxide to react with each other in the presence of a catalyst layer formed by filling a reactor with a solid catalyst, comprises a process of discharging the catalyst from the reactor if the differential pressure in the catalyst layer reaches a specified value, a process of separating and removing a substance sticking to the catalyst discharged and causing the increase of the differential pressure, and a process of reusing the catalyst removed of the substance causing the increase of the differential pressure.

Description

  The present invention relates to a method for producing propylene oxide. More specifically, the differential pressure in a catalyst layer increases, and a solid catalyst that has reached a specified value can be reused, thereby greatly increasing the catalyst cost in production. The present invention relates to a method for producing propylene oxide having an industrially excellent effect of being able to be improved.

  Propylene oxide is produced by reacting propylene with an organic peroxide in the presence of an epoxidation catalyst. As a method for producing such propylene oxide, for example, in Patent Document 1, a reactor is charged with a heterogeneous catalyst containing titanium chemically bonded to solid silica and / or inorganic silicate, and propylene oxide is obtained. Is described as a continuous process. Patent Document 2 describes a method for suppressing an increase in pressure loss of a solid catalyst layer of an epoxy reactor filled with a solid catalyst.

JP-A-2-42072 JP 2006-232753 A

However, in the case of continuously producing propylene oxide, the differential pressure of the catalyst layer formed in the reactor is increased, and there is a concern that the crushing strength of the catalyst may be exceeded, or the supply flow rate of the raw material to avoid destruction of the catalyst. When the differential pressure in the catalyst layer reaches the specified value, the reactor must be disconnected and the catalyst replaced with a catalyst even if the catalyst activity is sufficient. This was an increase factor of the catalyst cost in the oxide production.
In such a situation, the problem to be solved by the present invention is that the solid catalyst having an increased differential pressure in the catalyst layer can be reused, and thus the industrially excellent effect that the catalyst cost in production can be greatly improved. It is in the point which provides the manufacturing method of the propylene oxide which has.

  That is, the present invention is a process for producing propylene oxide by obtaining a propylene oxide by filling a reactor with a solid catalyst to form a catalyst layer and reacting propylene with a peroxide in the presence of the catalyst layer. In this method, a catalyst whose differential pressure in the catalyst layer has reached a specified value is extracted from the reactor, and after the differential pressure increase causing substance adhering to the extracted catalyst is separated and removed, the differential pressure increase causing substance is separated. The present invention relates to a method for producing propylene oxide having a step of reusing the removed catalyst.

  According to the present invention, the differential pressure in the catalyst layer is increased, and the solid catalyst that has reached the specified value can be reused. Therefore, there is an industrially excellent effect that the catalyst cost in production can be greatly improved.

It is a figure which shows the reactor and catalyst layer of this invention.

  In the method for producing propylene oxide of the present invention, propylene oxide is obtained by filling a catalyst into a reactor to form a catalyst layer, and reacting propylene with a peroxide in the presence of the catalyst layer. A method for producing oxide, wherein a catalyst whose differential pressure in the catalyst layer has reached a specified value is extracted from the reactor, and the differential pressure increasing cause substance adhering to the extracted catalyst is separated and removed, and then the differential pressure increasing cause A step of reusing the catalyst from which the substance has been separated and removed.

  As the reactor used in the present invention, a reactor usually used for filling a solid catalyst is used. For example, a fixed bed reactor in which a mesh-like floor called a catalyst support is installed in a cylindrical cylindrical container or a pipe is used. Can be mentioned. In the present invention, the catalyst layer is formed by filling the reactor with the catalyst.

  As the solid catalyst, a titanium-containing silicon oxide catalyst is preferable from the viewpoint of obtaining the target product in a high yield. The titanium-containing silicon oxide catalyst is preferably a so-called titanium-silica catalyst containing titanium chemically bonded to silicon oxide. Examples of the titanium-silica catalyst include a titanium compound supported on a silica carrier, a titanium compound combined with a silicon oxide by a coprecipitation method or a sol-gel method, and a zeolite compound containing titanium.

  In the present invention, propylene oxide is produced by reacting propylene and peroxide in the presence of the catalyst layer. Preferably, propylene and peroxide are continuously added to the catalyst layer. And propylene oxide is continuously produced.

  Examples of peroxides include hydrogen peroxide and organic peroxides, among which organic hydroperoxides are preferable, for example, cumene hydroperoxide, ethylbenzene hydroperoxide, tert-butyl hydroperoxide, and the like. It is done. A peroxide is synthesized by an oxidation reaction or the like of a corresponding hydrocarbon compound, and an organic acid by-produced in the course of the oxidation reaction acts as a catalyst poison of the solid catalyst used in the present invention. Therefore, in order to remove the organic acid, the peroxide is preferably subjected to a neutralization treatment in contact with an aqueous solution of a compound containing an alkali metal during and / or after the oxidation reaction. Examples of the compound containing an alkali metal include sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate and the like, and any of these compounds or a mixed aqueous solution thereof can be used. The alkali metal concentration in the aqueous solution is preferably 0.05 to 10% by weight. If the concentration is too low, the effect of removing the organic acid may be insufficient. On the other hand, if the concentration is too high, the decomposition reaction of the generated peroxide may be promoted and the yield may be reduced. After contacting the peroxide with an aqueous solution of a compound containing an alkali metal, it is usually separated into an oil phase / water phase. The compound containing an alkali metal remaining in the oil phase significantly increases the differential pressure of the catalyst layer, so that it is washed with water in contact with water to remove it, and further separated into an oil phase / water phase. . Although this water washing operation is repeated as necessary, the organic acid alkali metal salt contained in the oil phase does not cause an increase in the differential pressure of the catalyst layer of the present invention under economically feasible economy. Is difficult to remove.

  The oil phase after separation from the aqueous phase contains a trace amount of water. Since this water reduces the yield of the epoxidation reaction of the present invention and also acts as a catalyst poison, it is preferably removed as much as possible. Examples of the method for removing water include a method for removing using a separation membrane such as a coalescer, a method for consuming and removing by a reaction, a method for removing by distillation, and the like, and removing by distillation from an industrial viewpoint. Is preferred.

  The reaction between propylene and peroxide (hereinafter sometimes referred to as “epoxidation reaction”) is usually carried out in a liquid phase using a solvent. The solvent must be liquid under the temperature and pressure during the reaction and be substantially inert to the reactants and products. The solvent may consist of substances present in the peroxide solution used. For example, when cumene hydroperoxide is a mixture composed of cumene as a raw material, ethylbenzene hydroperoxide is a mixture composed of ethylbenzene as a raw material, or tert-butyl hydroperoxide is a raw material. In the case of a mixture composed of certain isobutane, this can be used as a substitute for the solvent without particularly adding a solvent.

  The temperature of the epoxidation reaction is usually 0 to 200 ° C, preferably 25 to 200 ° C. The pressure of the epoxidation reaction may be sufficient to keep the reaction mixture in a liquid state, and is preferably 0.1 to 10 MPa.

  The molar ratio of propylene to peroxide is preferably 2/1 to 50/1. If the ratio is too small, the reaction rate is lowered and the efficiency is poor. On the other hand, if the ratio is excessive, it is very difficult to separate and recover from the epoxidation reaction solution in order to recycle an excessive amount of unreacted propylene. Requires energy.

  When the production method of propylene oxide of the present invention is continuously performed, the liquid linear velocity of the reaction mixture varies depending on the composition of the mixture and the particle size of the solid catalyst, but preferably 0.1 to 3 cm / sec. It is.

Unreacted propylene contained in the mixed solution after the epoxidation reaction is separated and recovered and recycled to the reactor. Distillation can be used as a method for separating and recovering unreacted propylene. Distillation usually uses conditions where propylene is easily vaporized from the reaction solution. The distillation conditions vary depending on the temperature and composition of the reaction solution supplied to the distillation step, but usually the pressure is 0 to 5 MPa in gauge pressure, preferably 0 to 3 MPa, the top temperature is −50 to 150 ° C., The tower bottom temperature is 50 to 200 ° C, preferably 80 to 200 ° C. Moreover, you may use the method of distilling propylene in steps using a some distillation column.
The unreacted propylene separated and recovered in this way can be mixed with newly supplied propylene and supplied to the reactor.
However, also in the above preferred embodiment, as the propylene oxide is continuously produced, the differential pressure of the solid catalyst layer gradually increases.

In the present invention, the differential pressure in the catalyst layer refers to a pressure loss that occurs when a fluid passes through the catalyst layer, and the differential pressure increase refers to a catalyst that is caused by adhesion of a substance that causes a differential pressure increase to the catalyst. It means a phenomenon in which the void resistance of the layer is blocked and the resistance when the fluid passes increases.
In the present invention, examples of the method for measuring the differential pressure include a method of measuring at least two points of the inlet pressure and outlet pressure of the catalyst layer or the position of an arbitrary catalyst layer with a differential pressure gauge or a pressure gauge. Normally, the differential pressure is often monitored using two pressures at the inlet and outlet of the reactor. However, when one reactor is divided into a plurality of catalyst layers, The pressure at the inlet and outlet may be used, or when the adhesion of the substance causing the differential pressure increase is limited to the catalyst near the inlet of the catalyst layer, the differential pressure in any section of the catalyst layer near the inlet may be used. good.
When one reactor is divided into a plurality of catalyst layers, the height per catalyst layer when one reactor is filled with the same amount of catalyst is reduced, and the differential pressure per layer is suppressed. be able to. On the other hand, the equipment cost is increased due to the installation of additional catalyst support for splitting, and the space utilization rate (catalyst filling space ratio) inside the reactor is reduced because the catalyst is not filled in a part of the space under the catalyst support. Will do. Therefore, the number of catalyst layers inside one reactor may be determined by the practitioner in consideration of economy and operability.

  In the present invention, the catalyst whose differential pressure in the catalyst layer has reached the specified value is extracted from the reactor, and after the differential pressure increase causing substance adhering to the extracted catalyst is separated and removed, the differential pressure increase causing substance is separated. A step of reusing the removed catalyst.

In the present invention, the catalyst in which the differential pressure in the catalyst layer has reached a specified value means that the pressure loss caused when the fluid passes through the catalyst layer is determined from the limit of the strength of the catalyst and the strength of the catalyst support. Is a catalyst that exceeds a specified value in operation (a value determined by a practitioner in consideration of a margin for safety with respect to a mechanical limit value). The specified value is preferably 50 to 500 kPa, more preferably 100 to 300 kPa, most preferably 150 to 250 kPa.
If the specified value is too large, it is not preferable because an additional cost such as excessively dividing the catalyst layer or increasing the strength of the catalyst support is generated in order to suppress the packing height of one catalyst layer inside the reactor. .
On the other hand, when the specified value is too small, the operation interval for reusing the catalyst of the present invention becomes extremely short, which is not preferable.

  A compound containing an organic acid alkali metal salt is preferable as a substance causing a differential pressure increase.

  Examples of means for separating and removing the substance causing the differential pressure increase include dissolution removal by liquid washing. In particular, when the substance causing the differential pressure increase in the catalyst layer is a compound containing an organic acid alkali metal salt, water or warm water can be exemplified as a cleaning liquid used for liquid cleaning. By doing so, it is possible to dissolve and remove substances that adhere to the catalyst and cause the differential pressure to increase. It is preferable to dry the catalyst after liquid washing. The catalyst thus obtained can be recharged into the reactor and reused.

  As another means for separating and removing the substance causing the differential pressure in the catalyst layer of the present invention, sieving with a vibrating sieve can be mentioned. The sieving of the catalyst in which the differential pressure of the catalyst layer has reached a specified value by the vibrating sieve in the present invention means that the used catalyst extracted from the reactor is placed on a sieve having a predetermined opening, This means an operation of passing a solid finer than the opening of the sieve and collecting a solid larger than the opening on the sieve. By doing so, it is possible to separate the fine solid that is attached to the catalyst and causes the differential pressure to rise, and the catalyst recovered on the sieve is charged again into the reactor and can be reused.

  In the present invention, when sieving with a vibration sieve is performed, it is preferable that the sieve opening used is coarser than 20 mesh. When the mesh opening is finer than 20 mesh, the amount of fine solids to be sieved is small and the amount of recovered catalyst is increased, but the differential pressure recovery of the refilled catalyst may be insufficient.

  Next, the present invention will be specifically described with reference to examples.

[Example 1]
Cumene was oxidized in the presence of an aqueous sodium carbonate solution to obtain an oxidation reaction solution containing cumene hydroperoxide.
The oxidation reaction liquid was separated into oil and water, the obtained oil phase was further washed with water, and then the oil phase obtained by oil and water separation was used as a peroxide raw material liquid for epoxy reaction.
The peroxide raw material liquid contained a trace amount of an organic acid alkali metal salt.
The reactor (1) was filled with a solid catalyst to form a catalyst layer (2), which was an epoxy reactor.
As the upper limit of the differential pressure of the catalyst layer, a specified value of 200 kPa calculated from the strength of the catalyst itself and the strength of the catalyst support was determined.
Propylene oxide and cumyl alcohol were obtained by reacting propylene (5) and peroxide raw material liquid (6) in the presence of the catalyst layer.
The differential pressure of the catalyst layer (2) was calculated from the difference between the indicated values of the pressure gauge (3) and the pressure gauge (4).
During the operation, when the differential pressure of the catalyst layer (2) increased and reached a specified value, the reactor (1) was stopped and the catalyst was extracted from the reactor (1).
The extracted catalyst was subjected to sieving with a 16-mesh sieve to separate and remove the differential pressure increasing substance adhering to the catalyst.
The sieving catalyst obtained in this way is stored in a single reactor up to the required filling amount, the catalyst is filled again into the reactor, and a catalyst layer (reused catalyst layer) is formed to form a new epoxy reaction. It was a vessel.
The differential pressure of the reused catalyst layer was 42 kPa, and the differential pressure was 154 kPa lower than that of the catalyst layer whose differential pressure was increased before the reactor was stopped.
In the reused catalyst layer, the epoxy reaction was normally performed.

(1) Reactor (2) Catalyst layer (3) Pressure gauge (4) Pressure gauge (5) Propylene (6) Peroxide raw material liquid (7) Epoxy reaction liquid

Claims (5)

A method for producing propylene oxide, wherein propylene oxide is obtained by filling a solid catalyst in a reactor to form a catalyst layer and reacting propylene with a peroxide in the presence of the catalyst layer, The catalyst whose differential pressure in the catalyst layer has reached the specified value is extracted from the reactor, and after removing the differential pressure increase causing substance adhering to the extracted catalyst, the catalyst from which the differential pressure increase causing substance is separated and removed is reused. The manufacturing method of propylene oxide which has a process to do. The method according to claim 1, wherein the differential pressure increase causing substance comprises an organic acid alkali salt. The method according to claim 1 or 2, wherein the means for separating and removing the substance causing the differential pressure increase is dissolution removal by liquid washing. The method according to claim 1 or 2, wherein the means for separating and removing the substance causing the differential pressure increase is sieving with a vibrating sieve. The method according to any one of claims 1 to 4, wherein the peroxide is an organic hydroperoxide and is a peroxide subjected to a neutralization treatment using an aqueous solution of a compound containing an alkali metal.

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