WO2005030745A1

WO2005030745A1 - Method for producing propyleneoxide

Info

Publication number: WO2005030745A1
Application number: PCT/JP2004/013993
Authority: WO
Inventors: Junpei Tsuji; Masaru Ishino
Original assignee: Sumitomo Chemical Company, Limited
Priority date: 2003-09-25
Filing date: 2004-09-16
Publication date: 2005-04-07
Also published as: JP2005097184A

Abstract

A method for producing a propyleneoxide comprising the following steps is disclosed wherein the concentration of water in a solution containing a cumenehydroperoxide which is used in the epoxidation step is not more than 1 weight%. Oxidation step: A cumenehydroperoxide is obtained through oxidation of a cumene. Epoxidation step: A propyleneoxide and a cumyl alcohol are obtained through reaction between the cumenehydroperoxide obtained in the oxidation step and a propylene. Dehydration step: A α-methylstyrene is obtained through dehydration of the cumyl alcohol obtained in the epoxidation step in the presence of a dehydration catalyst. Hydrogenation step: A cumene is obtained by hydrogenating the α-methylstyrene in the presence of a hydrogenation catalyst and the thus-obtained cumene is recycled to the oxidation step.

Description

Description Production method of propylene oxide Technical field

The present invention relates to a method for producing propylene oxide. More specifically, the present invention allows the use of cumene hydroperoxide obtained from cumene as an oxygen carrier to convert propylene to propylene oxide, and that the cumene can be used repeatedly, and furthermore, it is possible to use propylene from propylene. The present invention relates to a method for producing propylene oxide, which can carry out an epoxidation reaction for obtaining pyrene oxide at a high yield and can further reduce the load on a purification step of propylene oxide as a product. . Background art

The process of converting propylene to propylene oxide using cumene hydroperoxide obtained from cumene as an oxygen carrier and repeatedly using the cumene is described in Czechoslovak Patent CS 14 074 43, U.S. Pat. No. 6,639,085, etc., this process is a process comprising an oxidation step, an epoxidation step, and a hydrocracking step. If cumyl alcohol obtained in the above is converted into cumene only by hydrogenolysis, the life of the catalyst is shortened and the yield is reduced, which is hardly sufficient for industrial realization. Disclosure of the invention

An object of the present invention is to convert propylene to propylene oxide by using cumene hydroperoxide obtained from cumene as an oxygen carrier, and to be able to use the cumene repeatedly. The epoxidation reaction for obtaining propylene oxide can be carried out at a high yield, the load on the purification process of the product propylene oxide can be reduced, and the activity of the dehydration catalyst can be prevented from lowering. An object of the present invention is to provide a method for producing propylene oxide that can be used.

That is, the present invention is a method for producing propylene oxide including the following steps, wherein the concentration of water in a solution containing cumene hydroperoxide to be subjected to an epoxidation step is 1% by weight or less. The present invention relates to a method for producing propylene oxide, which is characterized in that:

Oxidation step: Step of obtaining cumene hydroperoxide by oxidizing cumene

Epoxidation step: Step of reacting cumene hydroperoxide obtained in the oxidation step with propylene to obtain propylene oxide and cumyl alcohol.

Dehydration step: Step of obtaining α-methylstyrene by dehydrating cumyl alcohol obtained in the epoxidation step in the presence of a dehydration catalyst

Hydrogenation process: In the presence of a hydrogenation catalyst, a process for hydrogenating methylstyrene to make cumene and recycling it to the oxidation process Best mode for carrying out the invention

The oxidation step is a step of obtaining cumene hydroperoxide by oxidizing cumene. The oxidation of cumene is usually performed by autoxidation with oxygenated gas such as air or oxygen-enriched air. This oxidation reaction may be carried out without using an additive, or an additive such as an alkali may be used. Typical reaction temperatures are 50-200 ° C. and reaction pressures are between atmospheric pressure and 5 MPa. In the case of an oxidation method using an additive, alkaline reagents such as Na〇H and KOH, alkaline earth metal compounds or Na ₂ C〇 ₃ , Na HC〇 alkali metal carbonates or ammonia and like _{_{_{3 (NH 4) 2 C 0}}} 3, an alkali metal carbonate Anmoniumu salt or the like is used. The epoxidation step is a step of reacting cumene hydroperoxide obtained in the oxidation step with propylene to obtain propylene oxide and cumyl alcohol. The epoxidation step is preferably carried out in the presence of a solid catalyst composed of a titanium-containing silicon oxide from the viewpoint of obtaining the target product with high yield and high selectivity. These catalysts are preferably so-called Ti-silica catalysts containing Ti chemically bonded to silicon oxide. For example, a T i compound supported on a silica carrier, a compound compounded with a silicon oxide by a coprecipitation method or a sol-gel method, or a zeolite compound containing T i can be mentioned. In the present invention, cumene hydropoxide used as a raw material in the epoxidation step may be a diluted or concentrated purified or unpurified product.

The epoxidation reaction is carried out by bringing propylene and cumene hydroperoxide into contact with a catalyst. The reaction can be carried out in a liquid phase using a solvent. The solvent should be liquid at the temperature and pressure of the reaction and be substantially inert to the reactants and products. The solvent may consist of the substances present in the hydroperoxide solution used. For example, when cumene hydroperoxide is a mixture of cumene as a raw material, the mixture can be used as a solvent without adding a solvent.

The epoxidation reaction temperature is generally from 0 to 200 ° C, but a temperature of from 25 to 200 ° C is preferred. The pressure may be sufficient to keep the reaction mixture in a liquid state. In general, the pressure is advantageously between 100 and 1000 kPa. The epoxidation reaction can advantageously be carried out using a catalyst in the form of a slurry or fixed bed. For large-scale industrial operations, it is preferred to use a fixed bed. It can be carried out by a batch method, a semi-continuous method, a continuous method, or the like. When the liquid containing the reactants is passed through a fixed bed, the liquid mixture leaving the reaction zone contains no or substantially no catalyst. The dehydration step is a step in which cumyl alcohol obtained by the epoxidation reaction is used as a dehydration catalyst to obtain α-methylstyrene and water. The propylene oxide obtained in the epoxidation step is preferably separated from cumyl alcohol before the dehydration step, from the viewpoint of obtaining a high propylene oxide yield. As a method for separation, distillation can be used.

Examples of the catalyst used in the dehydration step include acids such as sulfuric acid, phosphoric acid, and ρ-toluenesulfonic acid, and metal oxides such as activated alumina, titania, zirconia, silica alumina, and zeolite. In this respect, a solid catalyst is preferred, and activated alumina is more preferred from the viewpoints of catalyst life, selectivity, and the like.

Although the dehydration reaction is usually performed by bringing cumyl alcohol into contact with the catalyst, in the present invention, hydrogen may be fed to the catalyst because a hydrogenation reaction is performed following the dehydration reaction. The reaction can be carried out in a liquid phase using a solvent. The solvent should be substantially inert to the reactants and products. The solvent may consist of the substances present in the cumyl alcohol solution used. For example, when cumyl alcohol is a mixture of the product, cumene, it can be used as a substitute for the solvent without particularly adding a solvent. The dehydration reaction temperature is generally from 50 to 450 ° C, but a temperature of from 150 to 300 ° C is preferred. In general, the pressure is advantageously between 10 and: L O O O O k Pa. The dehydration reaction can be advantageously carried out using a catalyst in the form of a slurry or a fixed bed.

The hydrogenation step is a step in which methyl styrene and water obtained by the dehydration reaction are supplied to a hydrogenation catalyst, α-methyl styrene is hydrogenated to be converted into cumene, and cumene is recycled to the oxidation step as a raw material for the oxidation step.

Examples of the hydrogenation catalyst include a solid catalyst containing a metal of Group 10 or Group 11 of the periodic table, and specific examples thereof include nickel, palladium, platinum, and copper. Palladium or copper is preferred from the viewpoint of suppressing the hydrogenation reaction and increasing the yield. Copper catalysts include copper, Raney copper, copper 'chromium, copper -Zinc, copper 'Chromium' zinc, copper 'silica, copper' alumina. Examples of the palladium catalyst include palladium 'alumina, palladium' silica, and palladium-carbon. These catalysts can be used alone or in combination.

The hydrogenation reaction is usually carried out by bringing permethylstyrene and hydrogen into contact with a catalyst.In the present invention, since the hydrogenation reaction is carried out subsequent to the dehydration reaction, part of the water generated in the dehydration reaction is separated into oil and water. May be separated, or may be subjected to a hydrogenation catalyst together with α-methylstyrene without separation. The amount of hydrogen required for the reaction may be equimolar to that of methyl styrene, but usually the raw material also contains other components that consume hydrogen, and an excess of hydrogen is required. Since the reaction proceeds more rapidly as the partial pressure of hydrogen is increased, a hydrogen-methylstyrene molar ratio of 1 to 10 is usually used. More preferably, it is 1 to 5. Excess hydrogen remaining after the reaction can be recycled after separation from the reaction solution. The reaction can be carried out in a liquid or gas phase using a solvent. The solvent must be substantially inert to the reactants and products. The solvent may consist of the substances present in the methylstyrene solution used. For example, when —methylstyrene is a mixture of the product cumene, it can be used as a substitute for the solvent without adding a solvent. The hydrogenation reaction temperature is generally 0 to 500 ° C., but a temperature of 30 to 40 is preferred. In general, it is advantageous for the pressure to be between 100 and 1000 kPa. Both the dehydration reaction and the hydrogenation reaction can be advantageously carried out by a continuous method using a catalyst in the form of a fixed bed. The dehydration reaction and the hydrogenation reaction may be performed in separate reactors or in a single reactor. The continuous method reactor includes a thermal cutoff reactor and an isothermal reactor. However, since an isothermal reactor requires equipment for removing heat, an adiabatic reactor is preferable. In the case of a single adiabatic reactor, the dehydration reaction of cumyl alcohol is an endothermic reaction, and the temperature decreases with the progress of the reaction.On the other hand, the hydrogenation reaction of permethylstyrene is an exothermic reaction. The temperature rises as it progresses. As a whole, the calorific value is higher, so the outlet temperature is higher than the reactor inlet temperature.

The reaction temperature and pressure are selected so that water contained in the α-methylstyrene solution after the dehydration reaction does not condense. The reaction temperature is preferably from 150 to 300 ° C., and the reaction pressure is preferably from 100 to 2000 kPa. If the temperature is less than 150 or the pressure exceeds 2000 kPa, water may condense at the outlet of the dehydration reaction, and may degrade the performance of the hydrogenation catalyst. If the pressure is too high, it is disadvantageous in the reaction equilibrium of the dehydration reaction. On the other hand, if the temperature exceeds 300 ° C or the pressure is lower than 100 kPa, a large amount of gas phase may be generated and fouling may occur, resulting in a reduction in catalyst life. May be disadvantaged.

Hydrogen can be fed from either the inlet of the fixed bed reactor or the inlet of the hydrogenation catalyst, but is preferably fed from the inlet of the fixed bed reactor in view of the activity of the dehydration catalyst. In other words, the constant presence of hydrogen in the dehydration reaction zone promotes the vaporization of water generated by dehydration, increases the equilibrium dehydration conversion rate, and obtains a higher conversion rate more efficiently than without hydrogen. Can be done. The water generated in the dehydration reaction passes through the hydrogenation catalyst.However, by operating at a level that does not condense as described above, it can be operated at low cost without providing any equipment for removing water. be able to. Unreacted hydrogen at the reactor outlet can be recycled and reused after the gas-liquid separation operation. It is also possible to separate the water generated in the dehydration reaction from the reaction liquid during the gas-liquid separation operation. A part of the obtained reaction liquid (mainly cumene) can be recycled to the reactor inlet for use. The amount of the dehydration catalyst may be any amount that can sufficiently convert cumyl alcohol, and the conversion of cumyl alcohol is preferably 90% or more. The amount of the hydrogenation catalyst may be an amount that can sufficiently convert -methylstyrene, and the α-methylstyrene conversion rate is preferably 98% or more. From a cost perspective, the dehydration catalyst and hydrogenation catalyst can be combined into a single fixed-bed reactor instead of a multi-stage reactor. Preferably, it is filled. The reactor may be divided into several beds or not. If not separated, the dehydration catalyst and hydrogenation catalyst may be in direct contact, but may be separated by inert packing.

In the present invention, it is necessary that the concentration of water in the solution containing cumene hydrooxide to be subjected to the epoxidation step is 1% by weight or less, preferably 500 ppm by weight or less. is there. Water reacts with propylene oxide in the epoxidation process to form darikols, which lowers the yield of propylene oxide. In addition, the glycols generated at this time remain until the dehydration step, which lowers the activity of the dehydration catalyst. Usually, propylene oxide is separated from the reaction solution after the epoxidation reaction. However, since water in the reaction solution is separated to the propylene oxide side, extra water is required to separate propylene oxide and water. Energy is required. From such a viewpoint, it is necessary to keep the concentration of water in the solution containing cumene hydroperoxide to be subjected to the epoxidation step within the range of the present invention. Methods for suppressing the concentration of water include a method of removing all or part of the water to the outside of the system comprising the process of the present invention by distillation, extraction, etc., a method of converting it to another compound by a reaction, an adsorbent, etc. Any method such as a method of reducing the concentration may be used. When removing water outside the system, the step of removing water (hereinafter sometimes referred to as “water removal step”) may be performed within at least each of the oxidation, epoxidation, dehydration, and hydrogenation steps. It can be carried out at at least one place connecting each process.However, there are cases where water is generated in the oxidation process, water may be added in the oxidation process, water washing may be performed after the oxidation process, etc. Considering this, it is preferable to remove water before the epoxidation step from the viewpoint of efficient batch removal. Example

Example A solution containing cumene hydroperoxide having a water concentration of 0.2% by weight was placed in a fixed-bed flow reactor in the presence of a Ti-containing silicon oxide catalyst in a fixed bed flow reactor, per mole of peroxide at the methane oxide port in the oxidizing solution. Was continuously passed through the reactor together with 10-fold molar propylene. By adjusting the inlet temperature, the conversion of cumene hydroperoxide was kept at 99%, and was stabilized stably. At this time, the reaction temperature was 60 ° C., the selectivity for propylene oxide was 95.0%, and the selectivity for propylene glycol was 1%.

Comparative Example 1

When the epoxidation reaction was carried out under the same conditions as in Example 1 except that the water concentration was 2% by weight, the selectivity of propylene oxide was reduced to 91.4%, and the selectivity of propylene glycol was 3%. Increased to 4%. Further, when propylene oxide is separated from the reaction solution after the epoxidation reaction, water in the reaction solution is separated to the propylene oxide side, so that extra water is required in the step of separating propylene oxide and water as compared with Example 1. Requires energy. Industrial applicability

According to the present invention, propylene can be converted to propylene oxide by using cumene hydroperoxide obtained from cumene as an oxygen carrier, and the cumene can be used repeatedly. The epoxidation reaction can be carried out at a high yield, the load on the purification process of propylene oxide as a product can be reduced, and the decrease in the activity of the dehydration catalyst can be suppressed. A method for producing propylene oxide can be provided.

Claims

The scope of the claims

1. A method for producing propylene oxide comprising the following steps, wherein the concentration of water in a solution containing cumene hydroperoxide to be subjected to an epoxidation step is 1% by weight or less. Propylene oxide production method.

Oxidation step: Step of obtaining cumene hydroperoxide by oxidizing cumene

Dehydration step: A step of obtaining methyl styrene by dehydrating the cumyl alcohol obtained in the epoxidation step in the presence of a dehydration catalyst.

Hydrogenation process: A process in which α-methylstyrene is hydrogenated into cumene in the presence of a hydrogenation catalyst and recycled to the oxidation process

2. The method according to claim 1, wherein the concentration of water is not more than 500 weight ppm.

3. The method according to claim 1 or 2, further comprising a step of removing water in the solution containing cumene hydroperoxide to be subjected to the epoxidation step. .