WO2005030742A1

WO2005030742A1 - Method for producing propyleneoxide

Info

Publication number: WO2005030742A1
Application number: PCT/JP2004/013992
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: JP2005097185A

Abstract

A method for producing a propyleneoxide is characterized in that the concentration of cumenehydroperoxide in a solution containing a cumyl alcohol is not more than 2 weight% at the end of epoxidation step. 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. Background art

The concept of the process of converting propylene to propylene oxide using cumene hydroperoxide obtained from cumene as an oxygen carrier and repeatedly using the cumene is disclosed in Czechoslovakia Patent CS1440743, Although disclosed in Japanese Patent Application Publication No. 2000-277007, etc., this process is a process comprising an oxidation step, an epoxidation step, and a hydrocracking step, and the process obtained in the epoxidation step is performed. If mill alcohol is converted to cumene only by hydrocracking, the catalyst life will be shortened and the yield will be low, which is hardly sufficient for industrial realization. Disclosure of the invention

An object of the present invention is to convert propylene to propylene oxide using cumene hydroperoxide obtained from cumene as an oxygen carrier, and to be able to use the cumene repeatedly, and to obtain by-products after the epoxidation step. It is an object of the present invention to provide a method for producing propylene oxide, which can reduce the production thereof, and thereby reduce the loss of cumene.

That is, the present invention is a method for producing propylene oxide including the following steps, wherein the concentration of cumene hydroperoxide in a solution containing cumyl alcohol at the end of the epoxidation step is 2% by weight or less. The present invention relates to a method for producing propylene oxide.

Oxidation step: Step of oxidizing cumene to obtain cumene hydroperoxide 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 0; -methylstyrene by dewatering cumyl alcohol obtained in the epoxidation step in the presence of a dehydration catalyst

Hydrogenation step: a step of hydrogenating permethylstyrene to form cumene in the presence of a hydrogenation catalyst, and recycling the cumene to an oxidation step. 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. For additives with oxidation, as the alkaline reagent, N a OH, alkali metal hydrosulfide oxides or as K_〇_H, alkaline earth metal compounds or N a ₂ C_〇 _{_3,} N a HC 0 ₃ alkali metal carbonates or ammonia and (NH ₄₎ ₂ C 0 ₃ such as, ammonium alkali metal carbonates two © beam salts and the like are used.

The epoxidation step is a step in which propylene oxide and cumyl alcohol are obtained by reacting cumene hydroperoxide obtained in the oxidation step with propylene. The epoxidation step is preferably carried out in the presence of a catalyst comprising a titanium-containing silicon oxide from the viewpoint of obtaining the desired 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 Ti compound supported on a silica carrier, a compound compounded with silicon oxide by a coprecipitation method or a sol-gel method, or a zeolite compound containing Ti can be used.

In the present invention, cumene hydroxide used as a raw material in the epoxidation step may be a diluted or concentrated purified or non-purified product. The epoxidation reaction is performed 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 the raw material and cumene, it can be used as a substitute for the solvent without particularly adding a solvent.

The epoxidation reaction temperature is generally 0 to 200 ° C, but a temperature of 25 to 200 ° C is preferred. The pressure may be sufficient to keep the reaction mixture in a liquid state. In general, it is advantageous for the pressure to be between 100 and 1000 kPa.

The epoxidation reaction can be advantageously 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. The reaction can be performed by a batch method, a semi-continuous method, a continuous method, or the like. When the liquid containing the reactants is passed through the fixed bed, the liquid mixture exiting 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 monomethylstyrene. 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. Distillation can be used as a separation method.

Examples of the catalyst used in the dehydration step include acids such as sulfuric acid, phosphoric acid, and p-toluenesulfonic acid, and metal oxides such as activated alumina, titania, zirconia, silica alumina, and zeolite. Solid catalysts are preferred from the standpoint of separation, and activated alumina is more preferred from the viewpoints of catalyst life and selectivity.

The dehydration reaction is usually performed by bringing cumyl alcohol into contact with the catalyst. However, in the present invention, hydrogenation 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 cumene as a product, 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, it is advantageous for the pressure to be between 10 and 1000 kPa. The dehydration reaction can be advantageously carried out using a catalyst in slurry or fixed bed form.

The hydrogenation process is a process in which α-methylstyrene obtained by the dehydration reaction is supplied to a hydrogenation catalyst, α-methylstyrene is hydrogenated and converted into cumene, and cumene is recycled to the oxidation process as a raw material in the oxidation process. .

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 viewpoints of suppressing the nuclear hydrogenation reaction and increasing the yield. Examples of the copper catalyst include copper, Raney copper, copper chromium, copper zinc, copper chromium zinc, copper silica, copper alumina, and the like. Examples of the palladium catalyst include palladium-alumina, palladium-silica, palladium-carbon, and the like. These catalysts can be used alone or in combination.

The hydrogenation reaction is usually carried out by bringing a-methylstyrene and hydrogen into contact with a catalyst, but in the present invention, since the hydrogenation reaction is carried out subsequent to the dehydration reaction, a part of the water generated in the dehydration reaction is obtained. May be separated by oil-water separation or the like, or may be subjected to hydrogenation catalyst together with —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. In addition, since the reaction proceeds more rapidly as the partial pressure of hydrogen is increased, usually a hydrogen / 0! -Methylstyrene molar ratio of 1 to 10 is preferably used. More preferably, it is 1 to 5. Excess hydrogen remaining after the reaction can be recycled and used after being separated from the reaction solution. The reaction can be carried out in a liquid or gas 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 used methyl styrene solution. For example, a mixture of a-methylstyrene and the product cumene In the case of a compound, this can be used as a substitute for a solvent without adding a solvent. The hydrogenation temperature is generally between 0 and 500 ° C, preferably between 30 and 400 ° C. 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 use separate reactors, or may use a single reactor. The reactor of the continuous method includes an adiabatic 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, since the dehydration reaction of cumyl alcohol is an endothermic reaction, the temperature decreases as the reaction proceeds.On the other hand, the hydrogenation reaction of -methylstyrene is an exothermic reaction. The temperature rises. As a whole, the calorific value is larger, so the outlet temperature is higher than the reactor inlet temperature.

The reaction temperature and pressure are selected so that the water contained in the Q! -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 lower than 150 ° C. or the pressure exceeds 2000 kPa, water may condense at the dehydration reaction outlet, deteriorating 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 less than 100 kPa, a large amount of gaseous phase may be generated and fouling may occur, thereby shortening the catalyst life. May be disadvantageous.

Hydrogen can be fed from either the inlet of the fixed bed reactor or the inlet of the hydrogenation catalyst, but it is preferable to feed hydrogen from the inlet of the fixed bed reactor in view of the activity of the dehydration catalyst. That is, the presence of hydrogen at all times in the dehydration reaction zone promotes the dehydration of water generated by dehydration, increases the equilibrium dehydration conversion rate, and achieves a higher conversion rate more efficiently than in the absence of hydrogen. Can be obtained. Water generated in the dehydration reaction passes through the hydrogenation catalyst, but as described above, By operating at a level that does not shrink, it is possible to operate at low cost without having to install equipment for removing water in particular. 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 an 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 capable of sufficiently converting methyl styrene, and the conversion rate of methyl styrene is preferably 98% or more. From the viewpoint of cost, it is preferable that the dehydration catalyst and the hydrogenation catalyst be packed in a single fixed-bed reactor without using a multi-stage reactor. The interior of the reactor may be separated into several beds or not separated. If not separated, the dehydration catalyst and the hydrogenation catalyst may be in direct contact, or may be partitioned with an inert packing.

In the present invention, the concentration of cumene hydroperoxide in the solution containing cumyl alcohol at the end of the epoxidation step needs to be 2% by weight or less, preferably 1% by weight or less. Here, the solution containing cumyl alcohol at the end of the epoxidation step refers to a solution composed of components that are liquid at normal temperature and pressure, and the target product propylene oxide and unreacted propylene are separated from the reaction mixture. A solution mainly consisting of cumene and cumyl alcohol obtained by separation.

Cumene hydroperoxide remaining after the epoxidation reaction is decomposed in the subsequent dehydration step, and acetophenone, which causes loss of cumene, is generated. It also produces cumene dimer, which also results in the loss of cumene, and this component causes occlusion trouble in the system. If a step of recovering unreacted propylene or propylene oxide is provided after the epoxidation step, a cumene loss component also occurs in this step. From such a viewpoint, it is necessary to keep the concentration of cumene hydroperoxide in the solution containing cumyl alcohol at the end of the epoxidation step within the scope of the present invention. How to reduce the concentration of cumene hydropoxide and In the epoxidation step, a method of converting to cumyl alcohol by reaction, a method of converting to another compound by reaction after the epoxidation step, all or part of cumene hydroperoxide by distillation, extraction, etc. May be removed from the reaction system, or the concentration may be reduced by an adsorbent or the like. Considering the simplicity of the process, it is preferable to convert most of the cumenehydroxide peroxide in the epoxidation step. Example

Example 1

The raw material for the dehydration and hydrogenation reaction shown below is passed through a fixed bed reactor filled with activated alumina catalyst, and continuously passed through a fixed bed reactor filled with 0.05% by weight palladium / alumina catalyst. I let it. In the reaction solution, 1.5 moles of hydrogen per mole of cumyl alcohol was continuously passed through the reactor. By controlling the inlet temperature of each reactor, cumyl alcohol was converted to approximately 100% monomethyl styrene and further to cumene. The reaction temperature at this time was 200 to 220 ° C. The composition of the obtained reaction solution was as follows. Raw materials for dehydration and hydrogenation reactions

Cumene eight drops 0.6% 1%

Cumyl alcohol 2 2.3 triple i 1%

Cumene 7 6 .6 i 1%

Acetofenone 0.1% 1%

Cumene Daima 0.1 0.1% 1%

Dehydration / hydrogenation reaction liquid composition

Cumene eight drop oxidide 0 layer | · ο

Cumyl alcohol 0.3

Cumene 99.1% by weight

Acetofenone 0.2 double

Cumene dimer 0.1 single Comparative Example 1

Example 1 Using a dehydration / hydrogenation reaction raw material having substantially the same composition as in Example 1 except that the concentration of cumene hydroperoxide was 5% by weight and the concentration of cumene was 72.2% by weight. The reaction was carried out under the same conditions as described above. The composition of the obtained reaction solution was as follows.

Dehydration / hydrogenation reaction liquid composition

0% by weight of cumene

Cumyl alcohol 1.0% by weight

Cumene 9 4.3% by weight

Acetofenone 3.5% by weight

0.6% by weight of cumene dimer

Compared with Example 1, the amount of acetophenone and cumene dimer clearly increased, and the loss of cumene increased. 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. It is possible to provide a method for producing propylene oxide, which can reduce the amount of product generated and thus can suppress the loss of cumene.

Claims

The scope of the claims

1. A method for producing propylene oxide comprising the following steps, wherein the concentration of cumene hydropoxide in a solution containing cumyl alcohol at the end of the epoxidation step is 2% by weight or less. A method for producing propylene oxide.

Oxidation step: Step of oxidizing cumene to obtain cumene hydroperoxide

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

Dehydration step: A step of obtaining permethylstyrene by dewatering cumyl alcohol obtained in the epoxidation step in the presence of a dehydration catalyst.

Hydrogenation process: Hydrogenation of a-methylstyrene in the presence of a hydrogenation catalyst to produce cumene, which is recycled to the oxidation process as a raw material for the oxidation process

2. The method according to claim 1, wherein the concentration of cumene hydroperoxide in the solution containing cumyl alcohol at the end of the epoxidation step is 1% by weight or less.