JP2001270873A - Method for producing propylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing propylene oxide, in which isopropylbenzene can repeatedly be used and by which the reaction yield and the activity of a catalyst are maintained at high levels. SOLUTION: This method for producing the propylene oxide comprises the following processes; an oxidation process: a process for oxidizing isopropylbenzene to obtain isopropylbenzene hydroperoxide, an epoxidation process: a process for reacting the isopropylbenzene hydroperoxide with propylene to obtain propylene oxide and cumyl alcohol, and a hydrogenolysis process: a process for hydrogenolyzing the cumyl alcohol to obtain isopropylbenzene and then recycling the isopropylbenzene to the oxidation process, which is characterized in that the pH value of the recycled isopropylbenzene solution is 5 to 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing propylene oxide. More specifically, the present invention can convert propylene to propylene oxide using isopropylbenzene hydroperoxide obtained from isopropylbenzene as an oxygen carrier, and can use the isopropylbenzene repeatedly. The reaction yield of the oxidation step of converting to hydroperoxide can be maintained at a high level, and the activity of the catalyst used in the epoxidation reaction for obtaining propylene oxide from propylene can be maintained at a high level for a long time. And a method for producing propylene oxide having the following characteristics.

[0002]

BACKGROUND OF THE INVENTION Propylene is oxidized using ethylbenzene hydroperoxide as an oxygen carrier,
The process for 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.

The concept of a process for converting propylene to propylene oxide using isopropylbenzene hydroperoxide obtained from isopropylbenzene as an oxygen carrier and repeatedly using the isopropylbenzene is described in Czechoslovak Patent CZ14.
No. 0743, the method described in this patent is at an insufficient level for industrial realization.

[0004]

Under such circumstances,
The problem to be solved by the present invention is to convert propylene to propylene oxide using isopropylbenzene hydroperoxide obtained from isopropylbenzene as an oxygen carrier, and to be able to use the isopropylbenzene repeatedly. The reaction yield of the oxidation step of converting to isopropyl benzene hydroperoxide can be maintained at a high level, and the activity of the catalyst used in the epoxidation reaction for obtaining propylene oxide from propylene can be maintained at a high level for a long time. The present invention is to provide a method for producing propylene oxide having such excellent characteristics.

[0005]

That is, the present invention relates to a method for producing propylene oxide comprising the following steps, wherein the hydrogen ion concentration (pH) of the recycled isopropylbenzene solution supplied to the oxidation step is 5 to 10: Which relates to a method for producing propylene oxide. Oxidation step: Step of obtaining isopropylbenzene hydroperoxide by oxidizing isopropylbenzene Epoxidation step: Step of obtaining propylene oxide and cumyl alcohol by reacting isopropylbenzene hydroperoxide obtained in the oxidation step with propylene Hydrogen Chemical decomposition step: a step of hydrogenating and decomposing cumyl alcohol obtained in the epoxidation step to obtain isopropylbenzene, and recycling the isopropylbenzene to the oxidation step as a raw material for the oxidation step

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The oxidation step of the present invention is a step of obtaining isopropylbenzene hydroperoxide by oxidizing isopropylbenzene. Oxidation of isopropylbenzene is usually performed by auto-oxidation using 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. Typical reaction temperatures are 50-200
° C and the reaction pressure is between atmospheric pressure and 5 MPa.
In the case of the oxidation method using an additive, as an alkaline reagent, an alkali metal compound such as NaOH or KOH and an aqueous solution thereof, an alkaline earth metal compound or Na ₂ C
Alkali metal carbonates such as O ₃ and NaHCO ₃ or ammonia and (NH ₄ ) ₂ CO ₃ , alkali metal ammonium carbonate and the like and aqueous solutions thereof are used.

The epoxidation step of the present invention is a step of reacting isopropylbenzene hydroperoxide obtained in the oxidation step with propylene to obtain propylene oxide and cumyl alcohol. Epoxidation step, from the viewpoint of obtaining the desired product under high yield and high selectivity,
It is preferable to carry out the reaction in the presence of a catalyst comprising a titanium-containing silicon oxide. These catalysts are preferably Ti-silica catalysts containing Ti chemically bonded to silicon oxide. For example, a titanium 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.

[0008] In the present invention, isopropylbenzene hydroperoxide used as a raw material in the epoxidation step may be a diluted or concentrated purified or non-purified product.

The epoxidation reaction is carried out by bringing propylene and isopropylbenzene hydroperoxide into contact with a catalyst. The reaction can be carried out in a liquid phase using a solvent. The solvent must be liquid at the temperature and pressure of the reaction and must be substantially inert to the reactants and products. The solvent may consist of the substances present in the hydroperoxide solution used. For example, when isopropylbenzene hydroperoxide is a mixture of isopropylbenzene, which is the raw material, isopropylbenzene hydroperoxide can be used in place of a solvent without adding a solvent. Other useful solvents include aromatic monocyclic compounds (eg, benzene, toluene, chlorobenzene, orthodichlorobenzene) and alkanes (eg, octane, decane, dodecane).

[0010] The epoxidation reaction temperature is generally 0 to 200 ° C.
However, a temperature of 25 to 200 ° C. is preferred. The pressure is
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 10000 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 preferable to use fixed beds. Also,
It 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 hydrocracking step of the present invention is a step of hydrocracking the cumyl alcohol obtained in the epoxidation step to obtain isopropylbenzene, and recycling the isopropylbenzene as a raw material in the oxidation step to the oxidation step. . That is, the same isopropylbenzene used in the oxidation step is regenerated by hydrocracking. The hydrocracking reaction is usually performed by bringing cumyl alcohol and hydrogen into contact with a catalyst. 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 cumyl alcohol solution used. For example, when cumyl alcohol is a mixture consisting of isopropylbenzene, which is a product, it is possible to substitute the solvent without adding a solvent. Other useful solvents include alkanes (eg, octane, decane, dodecane) and aromatic monocyclic compounds (eg, benzene, ethylbenzene, toluene). The hydrocracking reaction temperature is generally from 0 to 500 ° C, but from 30 to 40 ° C.
A temperature of 0 ° C. is preferred. Generally, the pressure is 100-1000
Advantageously, it is 0 kPa. The hydrocracking reaction is
It can be advantageously carried out using a catalyst in the form of a slurry or a fixed bed. As the catalyst, any catalyst having a hydrogenation ability can be used. Examples of the catalyst include a Group 8A metal-based catalyst such as cobalt, nickel and palladium, and a catalyst such as copper and zinc.
Although group B and group 2B metal catalysts can be used, it is preferable to use a copper catalyst from the viewpoint of suppressing by-products. Examples of the copper catalyst include copper, Raney copper, copper / chromium, copper / zinc, copper / chromium / zinc, copper / silica, copper / alumina, and the like. The method of the present invention can be performed by a batch, semi-continuous or continuous method. When the liquid or gas containing the reactants is passed through the fixed bed, the liquid mixture leaving the reaction zone contains no or substantially no catalyst.

The greatest feature of the present invention is that the hydrogen ion concentration (pH) of the recycled isopropylbenzene solution supplied to the oxidation step is 5 to 10. When the hydrogen ion concentration is too low, an organic acid and a heavy component that deteriorate the catalytic performance of the next epoxidation step are easily generated in the oxidation step, and a phenolic compound as a by-product is easily generated, and isopropyl This results in benzene loss. On the other hand, if the hydrogen ion concentration is too high, hydroperoxide is decomposed to generate acetophenone, which leads to loss of isopropylbenzene. In addition, acetophenone is converted into ethylbenzene through hydrogenolysis, but ethylbenzene further generates an epoxidation reaction inhibitor in the oxidation step. In order to control the hydrogen ion concentration within the range of the present invention, for example, if the recycled isopropylbenzene solution is acidic, an alkali metal compound, an alkaline earth metal compound or an alkali metal salt or ammonia and an alkali metal ammonium carbonate, etc. Can be used to adjust the pH, and if the solution is alkaline,
The pH can be adjusted using an inorganic acid, an organic acid or a salt thereof. In any case, it is preferable to further wash with water or the like in order to remove salts and the like remaining in the oil phase after pH adjustment. Here, the recycled isopropylbenzene solution supplied to the oxidation step means a solution containing recycled isopropylbenzene, and in addition to the isopropylbenzene solution recycled through the hydrocracking step, fresh isopropylbenzene solution And other solvents and the like. The hydrogen ion concentration (pH) of the present invention is a value measured as follows.
That is, the value is obtained by mixing the isopropylbenzene solution and water at a weight ratio of 1: 1 and shaking the mixture sufficiently, and then measuring the pH in the aqueous phase separated from the oil phase.

Further, in the present invention, the concentration of the organic acid in the solution containing isopropylbenzene hydroperoxide supplied to the epoxidation step is preferably 0.5% by weight or less, more preferably 0.1% by weight or less. % By weight or less. Thus, the activity of the catalyst used in the epoxidation step can be maintained at a high level, and the catalyst life can be maintained long.

Further, in the present invention, the concentration of ethylbenzene in the solution containing isopropylbenzene recycled to the oxidation step is preferably 10% by weight or less. Thereby, the reaction volume of each step can be effectively utilized, and the epoxidation reaction can be efficiently performed.

Further, in the present invention, the concentration of phenol in the solution containing isopropylbenzene recycled to the oxidation step is preferably 5% by weight or less. Thereby, the reaction volume of each step can be effectively utilized, and the oxidation reaction and the epoxidation reaction can be efficiently performed.

Furthermore, in the present invention, the concentration of cumene dimer in the solution containing isopropylbenzene recycled to the oxidation step is preferably 5% by weight or less. This makes it possible to effectively utilize the reaction volume in each step, and to prevent a blockage trouble in the system.

[0018]

As described above, according to the present invention, propylene can be converted to propylene oxide using isopropylbenzene hydroperoxide obtained from isopropylbenzene as an oxygen carrier, and the isopropylbenzene can be used repeatedly. Moreover, the reaction yield of the oxidation step of converting isopropylbenzene to isopropylbenzene hydroperoxide can be maintained at a high level, and the activity of the catalyst used in the epoxidation reaction for obtaining propylene oxide from propylene is maintained at a high level for a long time. Thus, a method for producing propylene oxide, which has an excellent characteristic that it can be performed, can be provided.

Claims (1)

[Claims] 1. A method for producing propylene oxide, comprising the following steps, wherein a hydrogen ion concentration (pH) of a recycled isopropylbenzene solution supplied to an oxidation step is 5 to 10. Oxidation step: Step of obtaining isopropylbenzene hydroperoxide by oxidizing isopropylbenzene Epoxidation step: Step of obtaining propylene oxide and cumyl alcohol by reacting isopropylbenzene hydroperoxide obtained in the oxidation step with propylene Hydrogen Chemical decomposition step: a step of hydrogenating and decomposing cumyl alcohol obtained in the epoxidation step to obtain isopropylbenzene, and recycling the isopropylbenzene to the oxidation step as a raw material for the oxidation step