JP2003096064A - Production method of propylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of propylene oxide by converting propylene into propylene oxide by using cumene hydroperoxide which is obtained from cumene, as the carrier of oxygen, wherein the cumene can be used repeatedly, further reaction volumes in each of the reaction steps can be effectively applied, and formation of unnecessary organic acids can be controlled. SOLUTION: The method involves the following steps. Oxidation step: Cumene hydroperoxide is obtained by oxidizing cumene. Epoxidation step: Propylene oxide and cumyl alcohol are obtained by reacting cumene hydroperoxide with propylene. Hydrogenating decomposition step: Cumene can be obtained by hydrogenating decomposition of the cumyl alcohol, and the cumene is recycled to the oxidation step. Removal step of cyclohexanol: At least one step in the above-mentioned steps, or at least one point on the line connecting the above- mentioned steps, wherein cyclohexanol is removed to the outside of the system.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing propylene oxide. More specifically, the present invention uses cumene hydroperoxide obtained from cumene as an oxygen carrier to convert propylene to propylene oxide, and the cumene can be repeatedly used, and moreover, the reaction volume of each step becomes effective. The present invention relates to a method for producing propylene oxide, which has an excellent feature that it can be utilized and the production of unnecessary organic acid can be suppressed.

[0002]

Oxidation of propylene using ethylbenzene hydroperoxide as oxygen carrier,
The process of obtaining propylene oxide and styrene is known as the Halcon process. According to this method, styrene is inevitably produced as a by-product together with propylene oxide, which is unsatisfactory from the viewpoint of selectively obtaining only propylene oxide.

[0003]

Under the present circumstances,
The problem to be solved by the present invention is that cumene hydroperoxide obtained from cumene is used as an oxygen carrier to convert propylene to propylene oxide, and the cumene can be repeatedly used, and the reaction volume of each step is increased. It is an object of the present invention to provide a method for producing propylene oxide, which has an excellent feature that it can be effectively utilized and the generation of unnecessary organic acid can be suppressed.

[0004]

That is, the present invention relates to a method for producing propylene oxide including the following steps. Oxidation step: a step of oxidizing cumene to obtain cumene hydroperoxide Epoxidation step: a cumene solution containing cumene hydroperoxide and propylene are reacted in a liquid phase in the presence of a solid catalyst to give propylene oxide. And step of obtaining cumyl alcohol Hydrogenolysis step: Cumyl alcohol obtained in the epoxidation step is hydrolyzed in the presence of a solid catalyst to obtain cumene, and the cumene is recycled to the oxidation step as a raw material for the oxidation step. Step of removing cyclohexanol: a step of removing cyclohexanol out of the system in at least one step of the above steps or at least one place connecting the above steps

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The oxidation step of the present invention is a step of obtaining cumene hydroperoxide by oxidizing cumene. Oxidation of cumene is usually carried out by autoxidation with an oxygen-containing 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. Normal reaction temperature is 50
˜200 ° C. and the reaction pressure is between atmospheric pressure and 5 MPa. In the case of the oxidation method using an additive, the alkaline reagent may be an alkali metal compound such as NaOH or KOH, an alkaline earth metal compound, Na ₂ CO ₃ , or NaH.
Alkali metal carbonates or ammonia and as _{CO 3 (NH 4) 2 CO} 3, alkali metal ammonium carbonate or the like is used.

The epoxidation step of the present invention is a step of obtaining propylene oxide and cumyl alcohol by reacting cumene hydroperoxide obtained in the oxidation step with propylene. The epoxidation step is preferably carried out in the presence of a catalyst containing a titanium-containing silicon oxide, from the viewpoint of obtaining the target product in high yield and high selectivity. These catalysts contain T chemically bonded to silicon oxide.
So-called Ti-silica catalysts containing i are preferred.
Examples thereof include 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.

In the present invention, cumene hydroperoxide used as a raw material in the epoxidation step is
It may be a dilute 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 the liquid phase using a solvent. The solvent must be liquid under the temperature and pressure of the reaction and 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 consisting of cumene as the raw material, it is possible to substitute this solvent without adding a solvent. Other useful solvents include aromatic monocyclic compounds (eg, benzene, toluene, chlorobenzene, orthodichlorobenzene), alkanes (eg, octane, decane, dodecane) and the like.

The epoxidation reaction temperature is generally 0 to 200 ° C.
However, a temperature of 25 to 200 ° C. is preferable. Pressure is
Sufficient pressure may be sufficient to keep the reaction mixture in the liquid state.
Generally, it is advantageous that the pressure is 100 to 10,000 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 fixed beds. Also,
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 the fixed bed, the liquid mixture exiting the reaction zone contains no or substantially no catalyst.

The hydrocracking step of the present invention is a step of hydrolyzing cumyl alcohol obtained in the epoxidation step to obtain cumene and recycling the cumene as a raw material for the oxidation step to the oxidation step. That is, by hydrocracking, the same cumene used in the oxidation step is regenerated. The hydrocracking reaction is usually carried out by bringing cumyl alcohol and hydrogen into contact with a catalyst. The reaction can be carried out in a liquid phase or a 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 cumyl alcohol solution used. For example, when cumyl alcohol is a mixture consisting of the product cumene, it is possible to substitute the solvent without adding a solvent. Other useful solvents are alkanes (eg octane, decane, dodecane).
And aromatic monocyclic compounds (for example, benzene, ethylbenzene, toluene) and the like. The hydrogenolysis reaction temperature is generally 0 to 500 ° C, but 30 to 400 ° C.
Is preferred. Generally the pressure is 100-10000k
Pa is advantageous. The hydrocracking reaction can be advantageously carried out using a catalyst in the form of a slurry or fixed bed. As the catalyst, any catalyst having hydrogenation ability can be used. Examples of the catalyst include Group 8A metal-based catalysts such as cobalt, nickel and palladium, and 1 such as copper and zinc.
The group B and 2B group metal catalysts can be mentioned, but from the viewpoint of suppressing by-products, it is preferable to use a copper catalyst. Examples of the copper-based catalyst include copper, Raney copper, copper / chromium, copper / zinc, copper / chromium / zinc, copper / silica, and copper / alumina. The method of the present invention can be carried out by a batch method, a semi-continuous method or a continuous method. When the liquid or gas containing the reactants is passed through the fixed bed, the liquid mixture exiting the reaction zone contains no or substantially no catalyst.

In the present invention, the concentration of cyclohexanol in the cumene recycled from the hydrocracking step to the oxidation step is preferably 5% by weight or less. Cyclohexanol is a compound produced by the nuclear hydrogenation reaction of phenol in the hydrocracking step. Phenol is a compound mainly produced by the decomposition reaction of cumene hydroperoxide in the epoxidation step. Cyclohexanol is a component that accumulates in the system, and if recycling is continued, the concentration will increase over time, reducing the effective reaction volume of each step, and at the same time, oxidizing part of it in the oxidation step to produce unnecessary organic acids. Inconvenience occurs. Considering effective utilization of the reaction volume and suppression of by-products, it is necessary to keep the concentration of cyclohexanol in the cumene recycled to the oxidation step within the range of the present invention. As a method of suppressing the concentration of cyclohexanol, in addition to a method of selecting a hydrogenolysis reaction condition in which a nuclear hydrogenation reaction is difficult to proceed, a system in which all or part of cyclohexanol is formed by a step of the present invention by distillation, extraction, etc. Examples thereof include a method of removing to the outside, a method of converting to another compound by a reaction, a method of decreasing the concentration with an adsorbent and the like. When removing to the outside of the system, the step of removing cyclohexanol (hereinafter sometimes referred to as “cyclohexanol removing step”) is at least in each step of the oxidation step, the epoxidation step and the hydrogenolysis step or each step. Usually, it can be carried out by distillation, extraction, etc. at at least one point, but the removal by distillation before the oxidation step suppresses the concentration of by-products to a low level and reduces the loss of the active ingredient. From the viewpoint of

[0013]

As described above, according to the present invention, cumene hydroperoxide obtained from cumene can be used as an oxygen carrier to convert propylene into propylene oxide, and the cumene can be repeatedly used, and each step can be repeated. It was possible to provide a method for producing propylene oxide, which has an excellent feature that the reaction volume of can be effectively utilized and the generation of unnecessary organic acid can be suppressed.

Claims (2)

[Claims] 1. A method for producing propylene oxide, which comprises the following steps. Oxidation step: a step of oxidizing cumene to obtain cumene hydroperoxide Epoxidation step: by reacting a cumene solution containing cumene hydroperoxide with an excess amount of propylene in a liquid phase in the presence of a solid catalyst , Step of obtaining propylene oxide and cumyl alcohol Hydrocracking step: Cumyl alcohol obtained in the epoxidation step is hydrolyzed in the presence of a solid catalyst to obtain cumene, and the cumene is oxidized as a raw material in the oxidation step. Step of recycling to a step Cyclohexanol removal step: a step of removing cyclohexanol out of the system in at least one step among the above steps or in at least one place connecting the above steps 2. The production method according to claim 1, wherein the concentration of cyclohexanol in the cumene recycled from the hydrocracking step to the oxidation step is 5% by weight or less.