JPH1135498A - Production of cumene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce cumene usable as a raw material for producing phenol and acetone by oxidation and degradation by carrying out an alkylation reaction of benzene with isopropyl alcohol, removing water from the reaction product, and recovering the unreacted benzene therefrom. SOLUTION: This method for producing cumene by alkylating benzene with isopropyl alcohol comprises a step for carrying out an alkylation reaction of the benzene by the isopropyl alcohol in a molar ratio of the benzene to the isopropyl alcohol supplied to the reaction, regulated so as to be (15:1) to (2:1) in the presence of a zeolite catalyst at 130-280 deg.C reaction temperature under a pressure sufficient to keep the liquid phase at the temperature, a step for removing water from the reaction product by a liquid-liquid separating method, and a step for recovering the unreacted benzene to provide the objective cumene efficiently. The cumene is an extremely important compound used in large quantities for producing phenol and acetone by oxidizing the cumene to provide cumene hydroperoxide, and degrading the cumene hydroxide in the presence of an acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing cumene efficiently by alkylating benzene using isopropyl alcohol instead of propylene as an alkylating agent. Cumene obtained by the method of the present invention is a very important compound that is oxidized to cumene hydroperoxide, which is used in a large amount to produce phenol and acetone by decomposing it in the presence of an acid.

[0002]

2. Description of the Related Art When producing phenol using cumene as a starting material, an equimolar amount of acetone is always produced as a by-product of phenol. Acetone as a by-product has a wide range of uses as a solvent or as a raw material for organic synthesis, but depending on the market trends at that time, acetone may be excessive or the market price of acetone may be poor, which lowers the economics of the phenol produced. Cause.

[0003] Cumene is usually produced by alkylating benzene with propylene. Propylene is produced by the thermal decomposition of naphtha, and propylene is often insufficient due to the demand balance between ethylene and propylene produced at the same time, which often becomes a bottleneck for cumene production. For the purpose of avoiding this bottleneck, there has been a proposal or attempt to hydrogenate acetone produced co-producing phenol to isopropyl alcohol, further dehydrate it, collect propylene and recycle it as a raw material for producing cumene or other compounds. It has been done.

[0004] The present invention provides a method for producing cumene by reacting benzene with benzene without dehydrating isopropyl alcohol obtained by hydrogenating acetone produced as a by-product during phenol production and converting it to propylene. It is about.

It has been known that alcohols function as alkylating agents for aromatics. However, when an alcohol is used as an alkylating agent, it has been considered that an equivalent amount of water is generated with the alkylating agent and the nucleophilicity of water with respect to the alkylation catalyst is high, thereby inhibiting the catalytic reaction. Therefore, the catalytic alkylation reaction using an alcohol as an alkylating agent has hardly been carried out industrially.

As a method for alkylating benzene with an olefin, alcohol or alkyl halide, there has been proposed a method using mordenite having a Hammett acidity function value less than -8.2 (JP-A-58-2161).
28). According to this, the reaction can be carried out in a liquid phase, but is preferably carried out in a gas phase. However, there is no description about the method and the working example when the reaction is carried out in the liquid phase. When alkylation and transalkylation are performed using mordenite mixed with alumina as a catalyst, olefins, alkyl halides, alcohols, ethers, or esters are listed as types of alkylating agents. No description (US Pat. No. 4,826,801, US.4849)
570).

[0007] An alkylation method using a mordenite catalyst having a silica to alumina ratio (silica / alumina molar ratio) of 15 or more and a symmetry index (SI) of 1 or more has been proposed (Japanese Patent Laid-Open No. 1-165531). The above specification also lists olefins, diolefins, or alcohols as alkylating agents, but does not disclose any alkylation method using other than olefins.

[0008]

An object of the present invention is to provide a method for efficiently producing cumene by alkylating benzene using isopropyl alcohol as an alkylating agent. According to the findings of the present inventors, if a zeolite, particularly a high-silica zeolite having a high silica-to-alumina ratio, is used as a catalyst for the alkylation reaction and reaction conditions are selected, isopropyl alcohol is used as an alkylating agent and a liquid phase is used. Even when the reaction is carried out, the alkylation reaction proceeds with almost the same reaction results as when an olefin is used as the alkylating agent. The problem with using isopropyl alcohol as the alkylating agent is that it produces cumene and an equimolar amount of water, which affects the product separation and purification steps. That is, the water produced by the reaction forms an azeotrope with unreacted benzene, isopropyl alcohol and the like, which complicates the process of isolating and obtaining cumene and disproportionating diisopropylbenzene and benzene as by-products.

[0009]

Means for Solving the Problems The present inventors have studied in detail a method for efficiently obtaining cumene by reacting benzene with benzene using isopropyl alcohol as an alkylating agent. As a result, in producing cumene by reacting benzene with isopropyl alcohol, zeolite is used as a catalyst, and water is first separated and removed from the mixture containing the target product after the reaction, which has come out of the catalyst layer, and then excessively. The inventors have found that cumene can be efficiently isolated and obtained industrially by separating and removing the unreacted benzene thus charged, and have completed the present invention.
That is, the present invention provides a method for producing cumene, which comprises producing water by alkylating benzene with isopropyl alcohol, removing water from a reaction product after the alkylation reaction, and then recovering unreacted benzene. It is.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The catalyst used in the method of the present invention is zeolite (crystalline aluminosilicate or an analog thereof), and a benzene ring can enter into its pores.
Various zeolites can be used as long as they exhibit solid acidity. Examples of preferred zeolites include mordenite, Y-type zeolite, faujasite, MFI
Type or MCM-22 type. As other zeolites, crystalline metallosilicates such as gallium silicate and borosilicate or crystalline metallophosphates such as silicoaluminophosphate can be used.

These zeolites are used as catalysts by imparting solid acidity as hydrogen ion type or polyvalent metal ion type such as rhenium and lanthanum. To form the hydrogen ion type, zeolite is ion-exchanged with an aqueous solution of ammonium salt such as ammonium chloride or ammonium nitrate to form an ammonium type and then calcined at 400 to 600 ° C, or treated with a dilute aqueous solution of a mineral acid such as hydrochloric acid or sulfuric acid. Similarly, baking is performed according to a conventional method.

When the zeolite used is a crystalline aluminosilicate, its silica to alumina ratio has a preferable range for this reaction. Usually, the silica to alumina ratio (silica / alumina molar ratio) is in the range of 10-300, more preferably 20-250. When the silica to alumina ratio (silica / alumina molar ratio) is less than the above range, tar-like organic substances are apt to accumulate in the catalyst, which causes a reduction in catalytic activity during long-term operation. If the silica to alumina ratio (silica / alumina molar ratio) is more than the above range, the accumulation of tar-like organic substances on the catalyst will not be recognized, but the above range will be selected because the catalytic activity becomes insufficient. The zeolite is alumina cement,
It is mixed with a molding aid such as silica sol or clay, molded by a conventional method, calcined, and used as a catalyst.

The method of the present invention is a method in which benzene and isopropyl alcohol are reacted in the presence of the above-mentioned zeolite catalyst, and water contained in the reaction mixture flowing out from the catalyst layer outlet is separated prior to the separation of other components. Of course, when light fractions such as propane or propylene produced by the reaction prior to the separation of water are generated, a method of performing these light fractions prior to the separation of water is also included in the scope of the present invention.

The reaction mixture flowing out of the alkylation reactor usually contains 3 to 8% by weight of water. The amount of water contained mainly varies depending on the molar ratio of benzene and isopropyl alcohol used for the reaction.

The separation and removal of the water can be carried out by various methods such as distillation and adsorption separation. In the system of the present invention, a liquid-liquid separation method is often used as a preferable method. In order to separate water by liquid-liquid separation, the component liquid at the outlet of the alkylation reactor is collected and left in a tower-type standing tank, and water settles at the bottom of the tower as a continuous phase, and cumene, benzene, and Since the oil phase containing diisopropylbenzene as a main component separates, water is extracted from the bottom of the column, and the upper oil phase is used for the isolation step of the target product.

In the case where the liquid-liquid separation is performed only by the stationary tank, 2
In some cases, the standing time required for the separation of the liquid phase takes a long time, or minute water droplets are suspended in the oil phase to form an emulsion, and the separation efficiency of the water and oil phases is poor. In such a case, the aqueous phase is separated using a centrifugal sedimentation separator. As the centrifugal sedimentation separator, a cylindrical centrifugal sedimentation separator, a separation plate type centrifugal sedimentation separator, or the like is frequently used. In the case of the present reaction system, there is a sufficient difference in density between water and the oil phase, and the viscosity of the oil phase is sufficiently low, so that water can be easily separated by a centrifugal sedimentation separator. The liquid-liquid separation may be performed using only a stationary tank, only a centrifugal sedimentation separator, or a combination of both in series.

The oil phase after the separation and removal of water is then separated and removed from unreacted benzene. Benzene is separated by a conventional method such as distillation. If there are light fractions such as propane and propylene dissolved in the oil phase, remove them in the process before removing the unreacted benzene if the light fraction has not been removed before the water separation and removal operation May be. A method of combining the step of removing the light fraction with the step of removing the unreacted benzene is of course included in the scope of the present invention.

In the process of the present invention, the molar ratio of benzene and alkylating agent to be used for the reaction is often in the range of 15: 1 to 2: 1, particularly in the range of 10: 1 to 4: 1. These molar ratios affect the ratio of the product cumene to diisopropylbenzene. The resulting diisopropylbenzene is converted to cumene by transalkylation with benzene, and an appropriate molar ratio of benzene to isopropyl alcohol is selected depending on the capacity of the transalkylator used.

When the process of the present invention is carried out in a flow reactor on an industrial scale, benzene and isopropyl alcohol are usually not supplied to the catalyst layer at the same time, but the catalyst layer is divided into multiple stages. A method is often used in which isopropyl alcohol is divided and supplied in multiple stages.
The catalyst layer is divided into two to six stages, and isopropyl alcohol is also supplied to two to six supply points in accordance with the division.

The benzene used in the method of the present invention is preferably of high purity, but it can be used in the method of the present invention as it is if it is dissolved in water. Those containing nitriles are not preferred. In addition, the incorporation of a substance exhibiting a surface-active action is not preferred because it lowers the efficiency of liquid-liquid separation of water from the reaction product.

Those containing higher alcohols, higher olefins, organic amines, or nitriles as impurities in isopropyl alcohol are not preferred raw materials for the method of the present invention. When a raw material containing these impurities is used, the catalytic activity decreases and the catalyst life is shortened.

The reaction temperature of the process according to the invention is between 130 and 280.
The range of ° C is often used. The pressure during the reaction may be higher than the pressure required to keep the reactant in the liquid phase at the reaction temperature. In the above reaction temperature range, 20 to 40 kg / cm ² G. Range. The contact time between the catalyst and the reactants is WHSV (weight
0.5 to 30 kg in terms of hourly space velocity)
/ Hr. kg. cat. Is frequently used. Preferably, the conversion of isopropyl alcohol is kept high. It usually operates at a conversion of 90% or more, more preferably 95% or more. If the conversion of isopropyl alcohol is low, not only the one-pass yield of the target product is lowered, but also the efficiency of separating and removing water from the reactor outlet component is lowered, which is not preferable.

[0023]

The present invention will be described more specifically with reference to the following examples. Example 1 A silica to alumina ratio (silica / alumina molar ratio) of 12
Hydrogen ion type high silica mordenite powder 0
To 5 parts by weight, 25 parts by weight of alumina cement powder manufactured by Condea were mixed, and a 10% aqueous solution of oxalic acid was added, followed by kneading into a paste. This was extruded and formed into 2 mmφ x 2 mm, and 500
The catalyst was calcined at ℃ to give a catalyst. A reaction tube made of stainless steel having an inner diameter of 22 mm was filled with 63 ml (40 g) of the above catalyst, and the outside of the reaction tube was heated in a sand fluidized bath to adjust the temperature of the catalyst layer to 180 ° C. Benzene to isopropyl alcohol in molar ratio of 5
As a reaction raw material, a solution prepared by adding 0.2% of water to a solution mixed in a ratio of 1: 1 was fed to a catalyst layer through a preheater at a rate of 320 g / hour (WHSV = 8) for reaction. The components at the outlet of the reactor 20 to 30 hours after the start of the reaction were collected and analyzed by a conventional method. As a result, the conversion of isopropyl alcohol was 98.5%, the selectivity of cumene was 85.5%, and the selectivity of diisopropylbenzene was 1
3.5% and diisopropyl ether selectivity 0.1
%Met.

The collected product liquid was placed in a glass cylindrical stationary tank and allowed to stand overnight to separate an aqueous phase and an oil phase. As a result of titrating the water in the oil phase after extracting the water phase from the lower part of the stationary tank with the Karl Fischer reagent, the water in the oil phase was 0.35%.
Met. At this time, the temperature of the oil phase is 30 ° C., and the solubility of water in the oil phase at this temperature is in the range of 0.08 to 0.1%. Therefore, the water suspended as an emulsion in the oil phase is It was recognized that the amount was as small as about 0.2 to 0.3%. The oil fraction from which the water had been removed was used to isolate the light fraction, benzene, cumene, and diisopropylbenzene using an Oldershaw still, and the results were obtained by distillation of the reaction mixture obtained using propylene as the alkylating agent. Similar to the result.

[0025]

According to the method of the present invention, even when isopropyl alcohol is used as the alkylating agent, benzene, cumene and diisopropylbenzene can be isolated and obtained without the influence of water generated in the stoichiometric amount by the reaction. it can.

Claims (8)

[Claims] 1. A method for producing cumene, which comprises removing water from a reaction product after the alkylation reaction and then recovering unreacted benzene when alkylating benzene with isopropyl alcohol to produce cumene. 2. The method according to claim 1, wherein the method for removing water from the reaction product is a liquid-liquid separation method. 3. The method according to claim 1, further comprising a step of removing a light fraction by-produced by the reaction, as a step before or after the operation of removing water from the reaction product. 4. The method according to claim 1, wherein the catalyst for the alkylation reaction is zeolite. 5. The method according to claim 1, wherein the alkylation reaction is carried out in a liquid phase. 6. The method according to claim 1, wherein the molar ratio of benzene and isopropyl alcohol used for the reaction is 15: 1 to 2: 1.
The method according to any one of claims 1 to 5. 7. The temperature of the alkylation is from 130 to 280 ° C.
The method according to any one of claims 1 to 6, wherein the reaction is carried out under a pressure sufficient to maintain a liquid phase at the above temperature. 8. The conversion of isopropyl alcohol to 90
%.