JP2005089413A - Method for purifying propylene oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for the stable purification of propylene oxide giving high-purity propylene oxide in high efficiency. <P>SOLUTION: The method for the purification of propylene oxide contains the following steps. The 1st step to distillate the stock liquid in a distillation column and separate a column bottom fraction containing aldehydes having a boiling point higher than that of propylene oxide; the 2nd step to carry out the extractive distillation of the column top fraction of the 1st step by using a 7-10C hydrocarbon as an extractant and separate the fraction into a column top fraction containing water and almost all part of the aldehydes and a column bottom fraction containing propylene oxide and the extractant; the 3rd step to separate the column bottom fraction obtained by the 2nd step into a column top fraction containing propylene oxide and a column bottom fraction containing the extractant; and the 4th step to distillate the column top fraction of the 3rd step by a distillation column and separate the fraction into a column top faction containing aldehydes having boiling point lower than that of propylene oxide and a column bottom fraction composed of propylene oxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for purifying propylene oxide. More specifically, the present invention relates to a reaction liquid obtained by reacting an organic peroxide and propylene in the presence of a catalyst, and having a reaction liquid containing at least aldehyde as a raw material liquid. The present invention relates to a method for purifying propylene oxide for separating and recovering propylene oxide from a liquid, and relates to a method for purifying propylene oxide capable of efficiently and stably obtaining high-purity propylene oxide.

  A method for obtaining propylene oxide by reacting an organic peroxide with propylene in the presence of a catalyst is known (patent document). In this case, in addition to the target propylene oxide, alcohols such as water, methanol and ethanol, aldehydes such as acetone, formaldehyde, acetaldehyde and propionaldehyde, and hydrocarbons such as propylene, pentane and hexane are by-produced. Therefore, in order to obtain high purity propylene oxide, a purification process for separating and recovering propylene oxide is required. It is well known in Patent Document 2 that propylene oxide containing water, methyl formate, and acetaldehyde as impurities is extracted and distilled using paraffin having 6 to 18 carbon atoms as an extraction solvent. Furthermore, Patent Document 3 discloses a method in which propylene oxide containing water, methanol, methyl formate, propionaldehyde, and acetone is purified in multiple stages and an alkane having 8 carbon atoms is used as an extractant.

JP 2001-31662 A US Pat. No. 3,338,800 US Pat. No. 5,133,839

  Under such circumstances, the problem to be solved by the present invention is a reaction liquid obtained by reacting an organic peroxide with propylene in the presence of a catalyst, and a reaction liquid containing at least aldehydes. To provide a method for purifying propylene oxide, which is a raw material liquid, and that separates and recovers propylene oxide from the raw material liquid, and which can efficiently and stably obtain high-purity propylene oxide. It is.

That is, the present invention provides a reaction liquid obtained by reacting an organic peroxide and propylene in the presence of a catalyst, and a reaction liquid containing at least aldehydes is used as a raw material liquid. This is a method for purifying propylene oxide for separating and recovering propylene oxide, and relates to a method for purifying propylene oxide including the following steps.
1st process: The process which attaches a raw material liquid to a distillation tower, and isolate | separates it into the tower bottom fraction containing aldehydes whose boiling point is higher than propylene oxide The 2nd process: C7-C10 A process of subjecting it to extractive distillation using hydrocarbons as an extractant and separating it into a top fraction containing most of water and aldehydes and a bottom fraction containing propylene oxide and an extractant. Third step: In the second step A step of separating the obtained bottom fraction into a top fraction containing propylene oxide and a bottom fraction containing an extractant. Fourth step: The top fraction obtained in the third step is attached to a distillation column, and propylene is added. Separating into a tower top fraction containing aldehydes having a boiling point lower than that of oxide and a tower bottom fraction comprising propylene oxide

  According to the present invention, a reaction liquid obtained by reacting a peroxide with propylene in the presence of a catalyst, wherein a reaction liquid containing at least aldehydes is used as a raw material liquid, and propylene oxide is converted from the raw material liquid. A method for purifying propylene oxide to be separated and recovered, the method for purifying propylene oxide including the following steps, and a method for purifying propylene oxide capable of efficiently and stably obtaining high-purity propylene oxide I was able to.

  The raw material liquid subjected to the purification method of the present invention is a reaction liquid obtained by reacting a peroxide with propylene in the presence of a catalyst to obtain propylene oxide. Examples of the peroxide include hydrogen peroxide, ethylbenzene hydroperoxide, cumene hydroperoxide, and the like.

  The catalyst for reacting the peroxide with propylene is preferably carried out in the presence of a catalyst comprising a titanium-containing silicon oxide from the viewpoint of obtaining the desired product with high yield and high selectivity. These catalysts are preferably so-called titanium-silica catalysts containing titanium 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, a zeolite compound containing titanium, and the like can be given.

  As a condition for reacting the peroxide and propylene, for example, in the present invention, the reaction can be carried out in a 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 peroxide solution used. For example, when the peroxide is cumene hydroperoxide or a mixture comprising cumene, it is possible to substitute the solvent without adding a solvent. Other useful solvents include aromatic monocyclic compounds (eg benzene, toluene, chlorobenzene, orthodichlorobenzene) and alkanes (eg octane, decane, dodecane), alcohols (methanol, ethanol), water and the like. . The reaction temperature is generally 0 to 200 ° C, but a temperature of 25 to 200 ° C is preferred. 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 reaction mode 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 a fixed bed. Moreover, it can implement by a batch method, a semi-continuous method, a continuous method, etc. Moreover, in order to perform a propylene oxide yield with a high yield, it is preferable to use it more than the equivalent of the peroxide supplied with propylene. In this case, excess propylene is recycled to the reactor after recovery.

  In the presence of a catalyst, the reaction solution after reacting peroxide with propylene includes organic acids such as formic acid and acetic acid, esters such as methyl formate and methyl acetate, alcohols such as water, methanol and ethanol, acetone and formaldehyde And impurities such as aldehydes such as acetaldehyde and propionaldehyde, and hydrocarbons such as propylene, pentane and hexane.

  In the first step referred to in the present invention, a propylene oxide-containing liquid containing at least aldehydes is used as a raw material liquid, the raw material liquid is attached to a distillation column, and a bottom fraction containing impurities having a boiling point higher than that of propylene oxide and propylene oxide To separate. Examples of impurities having a boiling point higher than that of propylene oxide include hydrocarbons having 6 or more carbon atoms such as organic acids, esters, water, propionaldehyde, methanol, hexane, and heptane. The operating conditions of the distillation column are 5 to 200 theoretical plates, 0.05 to 5 MPa absolute pressure as the operating pressure, and the temperature is 0 ° C to 300 ° C.

  In the second step, the column top fraction obtained in the first step is attached to a distillation column, and further, extractive distillation is performed using a hydrocarbon having 7 to 10 carbon atoms such as heptane and octane as an extractant, and water, formaldehyde, Acetaldehyde and methanol are separated from the tower top, and propylene oxide and extractant are separated from the tower bottom. The operating conditions are 5 to 200 in the theoretical stage, 0.05 to 5 MPa in absolute pressure as the operating pressure, the temperature is operated between 0 ° C. and 300 ° C., and the amount of the extract to be supplied is the propylene supplied An amount of 0.1 to 20 times the weight ratio of the oxide is supplied.

  In the third step, the bottom fraction obtained in the second step is supplied as a raw material to the distillation column, and propylene oxide is separated from the column top, and the extractant is separated from the column bottom. The operating conditions are 5 to 200 in the theoretical stage, 0.05 to 5 MPa in absolute pressure as the operating pressure, and the temperature is operated between 0 ° C and 300 ° C. When the propylene oxide to be supplied contains hydrocarbons having 6 to 10 carbon atoms, hydrocarbons having 7 to 10 carbon atoms such as heptane and octane are supplied as extractants to the distillation tower and extracted and distilled. Can be separated and removed. Further, the extractant at the bottom of the column may be recycled to the second step and / or the third step after purification.

  The fourth step is a step of removing hydrocarbons having 3 to 5 carbon atoms such as formaldehyde, acetaldehyde, propylene, butane, pentane, etc. that could not be removed in the second step with a distillation column. Propylene oxide is separated from the bottom of a hydrocarbon having 3 to 5 carbon atoms such as formaldehyde, acetaldehyde, propylene, butane, pentane and the like that could not be removed. The operating conditions are 5 to 200 in the theoretical stage, 0.05 to 5 MPa in absolute pressure as the operating pressure, and the temperature is operated between 0 ° C and 300 ° C.

The present inventor has found a method for purifying propylene oxide stably by minimizing the loss of propylene oxide by performing the above-described operation. For example, when the fourth step is operated first, high-concentration aldehydes are concentrated at the top of the tower, and the aldehydes become heavier, thereby blocking tower overhead piping and equipment and making stable operation difficult. . Furthermore, in order to suppress these blockages, it must be removed at the expense of the loss of propylene oxide, resulting in a very uneconomic operation. Therefore, by preliminarily separating aldehydes in the presence of water and methanol in the first step and the second step in advance, and finally removing them in the fourth step up to the product standard, the loss of propylene oxide is minimized. The propylene oxide can be stably purified.

Claims (2)

A reaction liquid obtained by reacting an organic peroxide with propylene in the presence of a catalyst, wherein the reaction liquid containing at least aldehydes is used as a raw material liquid, and propylene oxide is separated and recovered from the raw material liquid. A method for purifying propylene oxide, comprising the following steps.
1st process: The process which attaches a raw material liquid to a distillation tower, and isolate | separates it into the tower bottom fraction containing aldehydes whose boiling point is higher than propylene oxide The 2nd process: C7-C10 A process of subjecting it to extractive distillation using hydrocarbons as an extractant and separating it into a top fraction containing most of water and aldehydes and a bottom fraction containing propylene oxide and an extractant. Third step: In the second step A step of separating the obtained bottom fraction into a top fraction containing propylene oxide and a bottom fraction containing an extractant. Fourth step: The top fraction obtained in the third step is attached to a distillation column, and propylene is added. Separating into a tower top fraction containing aldehydes having a boiling point lower than that of oxide and a tower bottom fraction comprising propylene oxide The method for purifying propylene oxide according to claim 1, wherein the organic peroxide is cumene hydroperoxide.