JP2001270880A - Method for producing propylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing propylene oxide, which has excellent characteristics that comprise the conversion of propylene into the propylene oxide by the employment of an oxygen carrier comprising isopropylbenzene hydroperoxide obtained from isopropylbenzene, the repeated employment of the isopropylbenzene, the effective use of reaction capacities in the processes, respectively, the efficient execution of the oxidation reaction and the epoxidation reaction, and the efficient production of the propylene oxide. 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 obtained in the oxidation process with propylene to obtain propylene oxide and cumyl alcohol, and a hydrogenolysis process: a process for hydrogenolyzing the cumyl alcohol obtained in the epoxidation process to obtain isopropylbenzene and then recycling the isopropylbenzene to the oxidation process, which is characterized in that the concentration of phenolic compounds in the isopropylbenzene- containing solution recycled to the oxidation process is <=5 wt.%.

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 present invention relates to a method for producing propylene oxide, which has an excellent feature that it is possible to effectively utilize, and to efficiently perform an oxidation reaction and an epoxidation reaction, and thus to efficiently produce propylene oxide.

[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 Czechoslovakian patent CS14.
No. 0743, the method described in this patent publication does not include detailed descriptions of necessary steps other than the oxidation step, the epoxidation step, and the hydrogenolysis step, and isopropyl benzene is actually recycled. Then, various problems occur, and it is hard to say that it is sufficient 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. A method for producing propylene oxide having an excellent feature that a reaction volume can be effectively utilized, an oxidation reaction and an epoxidation reaction can be efficiently performed, and thus propylene oxide can be efficiently produced. It exists in.

[0005]

That is, the present invention relates to a method for producing propylene oxide comprising the following steps, wherein the concentration of a phenolic compound in a solution containing isopropylbenzene recycled to an oxidation step is 5% by weight. % Or less of 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 the alkaline reagent, an alkali metal compound such as NaOH or KOH,
Alkaline earth metal compound or Na ₂ CO ₃ , NaHCO ₃
Alkali metal carbonates such as or ammonia and (NH
₄ ) ₂ CO ₃ , alkali metal ammonium carbonate and the like 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.

In the present invention, the concentration of the phenolic compound in the solution containing isopropylbenzene to be recycled to the oxidation step needs to be 5% by weight or less, preferably 2% by weight or less.

Examples of the phenolic compound include phenol produced by the decomposition of isopropylbenzene hydroperoxide in the oxidation step and epoxidation step, and alkylphenol produced by the successive reaction of the produced phenol. The phenolic compound is a component accumulated in the system, and if the recycling is continued, the concentration increases with time, the effective reaction volume in each step is reduced, and the phenolic compound can be an oxidation reaction inhibitor. In order to obtain the desired isopropyl hydroperoxide in the inhibited oxidation reaction step, it is necessary to lengthen the reaction time or increase the reaction temperature, but in any case, a by-product that inhibits the epoxidation reaction is reduced. Will happen. In consideration of effective use of the reaction volume and inhibition of oxidation reaction and epoxidation reaction, the concentration of the phenolic compound in the solution containing isopropylbenzene recycled to the oxidation step must be kept within the range of the present invention.

As a method for controlling the concentration of phenol within the scope of the present invention, a method of removing all or a part of phenol to the outside of the system comprising the process of the present invention by distillation, washing with an extracted alkali, etc. And a method of reducing the concentration with an adsorbent or the like. The step of removing the phenolic compound out of the system (hereinafter, sometimes referred to as a “phenol removal step”) is performed in
In at least one of the oxidation step, the epoxidation step and the hydrocracking step or at least one place connecting the respective steps, the step can be usually carried out by distillation, extraction, alkali washing, or the like. Is preferably performed. Reagents used for alkali washing include alkali metal compounds such as NaOH and KOH,
Alkaline earth metal compound or Na ₂ CO ₃ , NaHCO ₃
Alkali metal carbonates such as ammonia or ammonia and NH ₄
CO ₃ and alkali metal ammonium carbonate are used. The phenol can be removed from the oil layer by mixing the phenol-containing oil layer and the alkali-containing aqueous layer and separating the aqueous layer. The mixing ratio of the oil layer and the aqueous layer is preferably 100 to 0.01 in terms of the oil layer / aqueous layer weight ratio. After separating the aqueous layer, it is preferable to wash the oil layer with water for the purpose of removing the alkali remaining in the oil layer.

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 hydrogen ion concentration (pH) in the solution containing isopropylbenzene recycled to the oxidation step is preferably 5 to 10.
Thereby, the yield of the oxidation step can be maintained at a high level. The pH here 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.

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.

[0020]

Embodiment 1Oxidation process  Isopropylbenes recycled from the hydrocracking process
Zen (isopropylbenzene recycled to oxidation process)
The concentration of phenolic compounds in the solution containing
It is as follows. ) Is mixed with air at a pressure of 300 kPa and a temperature of 300 kPa.
The reaction is carried out at 150 ° C. for 5 hours. Oxidizing liquid generated
Has the following composition: Oxidizing solution composition Cumene hydroperoxide 35% by weight Cumyl alcohol 2% by weight Isopropylbenzene 60% by weight Phenol 0.0% by weightEpoxidation process  The oxidizing solution obtained in the oxidizing step is converted to a Ti-containing silicon oxide catalyst.
In a fixed bed flow reactor in the presence of
Per mole of benzene hydroperoxide
Into the reactor continuously with 10 times the mole of propylene
Let it pass. By adjusting the entrance temperature,
Hydroperoxide conversion rate is maintained at 99% and steady
To be standardized. At this time, the reaction temperature was 60 ° C., and the selectivity was
95%. From the obtained epoxidized solution,
Separation and recovery of light-boiling components such as propylene and propylene oxide
I do. The composition of the reaction solution obtained is as follows. Epoxidation liquid composition Cumene hydroperoxide 0.4% by weight Cumyl alcohol 33.6% by weight Isopropylbenzene 62.4% by weight Phenol 0.4% by weightHydrocracking process  The reaction solution obtained in the epoxidation step is treated with a copper chromium catalyst.
Under the fixed bed flow reactor, cumyl alcohol 1
Continuous reaction with 2 moles of hydrogen per mole
Let go through the vessel. By adjusting the inlet temperature,
Approximately 100% conversion of the mill alcohol. At this time
The reaction temperature is 180 ° C. The resulting set of hydrocracking liquids
The result is as follows. Hydrolysis solution composition Cumene hydroperoxide 0 wt% Cumyl alcohol 0 wt% Isopropylbenzene 96.2 wt% Phenol 0.5 wt%Phenol removal process  From the hydrocracking solution obtained in the hydrocracking step, NaOH
Phenol is removed by neutralization washing using an aqueous solution.
The composition of the obtained oil layer is as follows. Phenol removal liquid composition Cumene hydroperoxide 0 wt% Cumyl alcohol 0 wt% Isopropylbenzene 97 wt% Phenol 0 wt%

Comparative Example 1 Oxidation, epoxidation, and hydrocracking under the same conditions as in Example 1 except that phenol was not removed, the phenol concentration in the recycled oil layer continued to rise, and the oxidation process The concentration of the phenolic compound in the solution containing isopropylbenzene recycled to
The reaction volume in each step cannot be used effectively, and the oxidation reaction efficiency and epoxidation reaction efficiency gradually decrease.

[0022]

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. In addition, the reaction volume of each step can be effectively utilized, the oxidation reaction and the epoxidation reaction can be efficiently performed, and thus the propylene oxide production method has an excellent feature that propylene oxide can be efficiently produced. Could be provided.

Claims (2)

[Claims] 1. A method for producing propylene oxide, comprising the following steps, wherein the concentration of a phenolic compound in a solution containing isopropylbenzene recycled to an oxidation step is 5% by weight or less. 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 2. The method according to claim 1, further comprising a step of removing the phenolic compound out of the system at least in each step or in each step connecting the steps.