JP2006131562A - Method for producing propylene oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing propylene oxide, having an excellent feature of increasing the yield of a whole epoxidation reaction. <P>SOLUTION: This method for continuously producing propylene oxide comprises epoxidation reaction of an organic peroxide with propylene by using at least two reactors, wherein the method for producing propylene oxide is characterized by controlling the reaction conditions by at least monitoring a peroxide dimer concentration of a final stage reactor outlet. An analytical method using chromatogram can be used for analyzing the peroxide dimer. As some kinds of peroxide dimer are thermally unstable, so liquid chromatography capable of analyzing without heating is generally used. By using near infrared rays, on-line analysis is possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing propylene oxide. More specifically, the present invention relates to the production of propylene oxide by an epoxidation reaction of organic peroxide and propylene using at least two reactors, and at least the peroxide dimer at the outlet of the last stage reactor. It is related with the manufacturing method of propylene oxide characterized by monitoring the density | concentration of and controlling reaction conditions.

  It is known to produce propylene oxide continuously by reacting an organic peroxide and propylene using a plurality of reactors. Patent Document 1 describes a method for producing propylene oxide from ethylbenzene hydroperoxide and propylene, and discloses a temperature control method for each reactor. Patent Document 2 discloses a method for producing propylene oxide from cumene hydroperoxide and propylene, and discloses a method for improving the yield by regulating moisture in the epoxidation reaction raw material. However, according to known technical information, an epoxidation step that requires a high degree of reaction condition control (herein, an epoxidation step is a reaction of propylene oxide and alcohol by reacting an organic peroxide with propylene. In terms of controlling the reaction conditions so that the yield of the obtained process is high) is not always satisfactory.

International Publication No. 02/090340 Pamphlet JP 2001-270876 A

  Under such circumstances, the problem to be solved by the present invention is that when at least two reactors are used to continuously produce propylene oxide by epoxidation reaction of organic peroxide and propylene, at least at the outlet of the last stage reactor. A method for producing propylene oxide characterized in that the reaction conditions are controlled by monitoring the concentration of peroxide dimer, and has an excellent feature that the yield of the entire epoxidation reaction can be increased. The point is to provide a method for producing propylene oxide.

  That is, in the present invention, when continuously producing propylene oxide by epoxidation reaction of organic peroxide and propylene using at least two reactors, at least the concentration of the peroxide dimer at the outlet of the last stage reactor The method relates to a method for producing propylene oxide, characterized in that the reaction conditions are controlled by monitoring the reaction conditions.

  According to the present invention, when continuously producing propylene oxide by epoxidation reaction of organic peroxide and propylene using at least two reactors, at least the concentration of the peroxide dimer at the outlet of the last stage reactor is monitored. Propylene oxide production method characterized in that the reaction conditions are controlled to provide a method for producing propylene oxide having an excellent feature that the yield of the entire epoxidation reaction can be increased. it can.

  Hereinafter, the present invention will be described in detail. First, an outline of a method for producing propylene oxide by an epoxidation reaction of an organic peroxide and propylene will be described.

The organic peroxide solution is usually obtained by auto-oxidation of an organic compound with an oxygen-containing gas such as air or oxygen-enriched air. This oxidation reaction may be carried out without adding an alkali, but an additive such as an alkali may be used. The normal oxidation reaction temperature is 50 to 200 ° C., and the reaction pressure is between atmospheric pressure and 5 MPa. In the case of the oxidation method using additives, alkaline reagents include alkali metal compounds such as NaOH and KOH and aqueous solutions thereof, alkaline earth metal compounds or alkali metal carbonates such as Na ₂ CO ₃ and NaHCO ₃ , or ammonia and (NH4) ₂ CO ₃ and aqueous solution is used.

  As organic peroxides, cumene hydroperoxide produced by oxidation of cumene, ethylbenzene hydroperoxide produced by oxidation of ethylbenzene, and tert-butyl hydroperoxide produced by oxidation of isobutane are well known. .

  Propylene oxide is produced by conducting an epoxidation reaction of propylene using the organic peroxide thus produced. The epoxidation step is a step of obtaining propylene oxide and alcohol by reacting an organic peroxide with propylene.

  As the catalyst, a catalyst comprising a titanium-containing silicon oxide is preferable from the viewpoint of obtaining the target product in a high yield. 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.

  The organic peroxide used as a raw material for the epoxidation process may be a diluted or concentrated purified product or non-purified product.

  The epoxidation reaction is performed by bringing propylene and an organic peroxide into contact with a catalyst. The reaction is carried out in the liquid phase using a solvent. The solvent must be liquid under the temperature and pressure during the reaction and be substantially inert to the reactants and products. The solvent may consist of substances present in the organic peroxide solution used. For example, when cumene hydroperoxide is a mixture consisting of cumene as a raw material, ethylbenzene hydroperoxide is a mixture consisting of ethylbenzene as a raw material, or isobutane where tert-butyl hydroperoxide is a raw material. In the case of a mixture consisting of the above, it is possible to substitute for the solvent without adding a solvent. Other useful solvents include aromatic monocyclic compounds (eg benzene, toluene, chlorobenzene, orthodichlorobenzene) and alkanes (eg octane, decane, dodecane).

  The epoxidation reaction temperature is generally 0 to 200 ° C, but a temperature of 25 to 200 ° C is preferable. The pressure may be sufficient to keep the reaction mixture in a liquid state. In general, the pressure is advantageously between 100 and 10000 kPa.

  The solid catalyst can be advantageously carried out in the form of a slurry or a fixed bed. For large scale industrial operations, it is preferred to use a fixed bed. Moreover, it can implement by a batch method, a semi-continuous method, a continuous method, etc.

  The molar ratio of propylene / organic peroxide supplied to the epoxidation step is preferably 2/1 to 50/1. If the ratio is too small, the reaction rate decreases and the efficiency is poor. On the other hand, if the ratio is too large, it is very difficult to separate and recover from the epoxidation reaction solution in order to recycle excessive amounts of unreacted propylene. Requires a lot of energy.

  The reaction conditions for the epoxidation reaction include temperature, pressure, propylene / organic peroxide molar ratio, and the like. These reaction conditions are adjusted based on the analytical value of the reaction product. The reaction rate in each reactor can be grasped by analyzing the concentration of the organic peroxide. Analyzing methods include iodometric titration and liquid chromatography. When there are a plurality of reactors, the concentration of peroxide at the inlet of each reactor and the residual activity of the catalyst are often different, so there are a plurality of combinations in setting reaction conditions in each reactor. The present inventors measured at least the concentration of the peroxide dimer at the outlet of the last-stage reactor as an index of the combination, and each reactor so that the total amount of peroxide dimer generated is minimized. It was found that a high yield can be obtained in the entire epoxidation reaction by adjusting the reaction conditions.

  As a method for analyzing the peroxide dimer, an analysis method using a chromatogram can be used. Depending on the type of peroxide dimer, the thermal stability is low, so it is common to use liquid chromatography that can be analyzed without heating. Moreover, online analysis is possible by using near infrared rays.

  The peroxide dimer is mainly generated by the decomposition reaction of the organic peroxide that is the raw material of the epoxidation reaction. When the organic peroxide is ethylbenzene hydroperoxide, the peroxide dimer is diethylbenzene peroxide, when it is cumene hydroperoxide, dicumyl peroxide, when it is tert-butyl hydroperoxide, tert -Butyl peroxide is produced.

When the peroxide dimer is dicumyl peroxide, by minimizing the amount of this compound generated, it is possible to suppress the production of propylene glycol, which results in a loss in yield of the epoxidation reaction. Production of methanol, aldehydes, light boiling hydrocarbons, and the like, which are impurities during purification, can be suppressed to a low level.
As a place for monitoring the concentration of the peroxide dimer, the total amount generated can be grasped by analyzing at least at the outlet of the last-stage reactor. If the concentration of the peroxide dimer is monitored at the outlet of each reactor, it becomes a standard for the reaction conditions of each reactor, and the reaction conditions can be easily changed.

Next, an example explains the present invention.
Example 1
A solution containing 25 wt% cumene hydroperoxide, in which a fixed bed adiabatic flow reactor comprising three independent catalyst layers is filled with a Ti-containing silicon oxide catalyst prepared according to the method described in JP-A-2004-195379. 430 parts to the first catalyst layer, 250 parts to the second catalyst layer, and 400 parts to the third catalyst layer. On the other hand, 800 parts of propylene was fed to the first catalyst layer. A total of 1230 parts of the effluent reactant at the outlet of the first catalyst layer is mixed with a solution containing 250 parts of the 25% by weight cumene hydroperoxide after cooling and fed to the second catalyst layer. Part of the effluent reactant was mixed with a solution containing 400 parts of the 25 wt% cumene hydroperoxide after cooling and fed to the third catalyst layer. The concentration of dicumyl peroxide (DCMPO) at the outlet of each reactor was measured, and the temperature of each catalyst layer was adjusted so that the total amount of DCMPO generated was minimized. The conversion of cumene hydroperoxide in all three reactors was adjusted to 80%. Table 1 shows the amount of acetaldehyde (AA) that is an impurity in the purification of propylene glycol (PG) and propylene oxide, which are causes of a decrease in the epoxidation reaction yield.

Claims (4)

When producing propylene oxide continuously by epoxidation reaction of organic peroxide and propylene using at least two reactors, the reaction conditions are monitored by monitoring the concentration of the peroxide dimer at the outlet of the last stage reactor. A process for producing propylene oxide, characterized in that By reacting the organic peroxide with propylene, the reaction conditions of each reactor are set so that the amount of peroxide dimer generated in the entire epoxidation process, which is a process for obtaining propylene oxide and alcohol, is minimized. The manufacturing method according to claim 1 to be controlled. The method according to claim 1, wherein the organic peroxide is cumene hydroperoxide and the peroxide dimer is dicumyl peroxide. The process according to claim 1, wherein the catalyst used in the epoxidation reaction is a catalyst comprising titanium-containing silicon oxide.