RU2527279C2 - Method of obtaining propylene oxide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to method of obtaining propylene oxide, bulk product, used for production of polyurethanes, glycols, solvents, cosmetic preparations and medications. Method includes the following stages: a) interaction of propylene glycol with hydrogen chloride at higher temperature in presence of carboxylic acids with formation of propylene chlorohydrins; b) dehydrochlorination of propylene chlorohydrins with alkali with formation of propylene oxide. In accordance with invention hydrochlorination of propylene glycol is carried out with simultaneous distillation of water, containing reaction products, and output of reaction products from hydrochlorination reactor by side distillation.

EFFECT: increased rate of formation of propylene chlorohydrins and propylene oxide productivity.

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Description

The invention relates to a method for producing propylene oxide - a large-capacity product used to obtain polyurethanes, glycols, solvents, cosmetics and medical preparations.

The rapid rise in price and a decrease in oil reserves forced us to look for new unconventional sources of raw materials. The source of such raw materials may be renewable plant resources.

Currently, there are highly effective technologies for processing grain raw materials to glucose syrups and Jerusalem artichoke to fructose syrups. The proposed technology for processing glucose-fructose syrups into propylene oxide includes one biochemical (fermentation) and four chemical (esterification, hydrogenation, hydrochlorination and dehydrochlorination) stages. According to this technology, in the hydrogenation of lactic acid esters, propylene glycol is obtained in almost quantitative yield (WO 2009103682).

In the production of propylene oxide to produce propylene chlorohydrins by the chlorine method, it is advantageous to use hydrogen chloride and propylene glycol instead of chlorine and propylene. The use of the obtained concentrated solution of propylene chlorohydrins (over 75% by mass) instead of a 4-6% solution obtained in the chlorine method at the alkali dehydrochlorination stage used in the industry will reduce contact time in the reactor, energy consumption and the amount of production waste compared to the current technology.

A known method of producing propylene by reacting propylene with hydrogen peroxide in an organic solvent using a heterogeneous catalyst (RU 2205181). Propylene oxide according to this method is obtained in a cascade of 3-5 adiabatic reactors with a fixed catalyst bed at a preferred molar ratio of hydrogen peroxide to propylene from 1: 5 to 1:20 and a temperature of 40-80 ° C. The required temperature is maintained by cooling the reaction mass in the intermediate heat exchangers. The solvent used is methanol or isopropanol, the catalyst is titanium silicate.

A significant disadvantage of this method is the need to use a large number of reactors and heat exchangers during epoxidation of propylene with hydrogen hydroperoxide.

Closest to the claimed method is a method for producing epoxides by reacting polyhydroxylated aliphatic hydrocarbons or their esters with a chlorinating agent, followed by adding a base as a dehydrochlorinating agent to the reaction medium (US 2008/0194850). The process is carried out in the presence of a catalyst - a carboxylic acid, preferably acetic and adipic, at elevated temperature.

The disadvantages of this method are the low reaction rate of hydrochlorination of polyhydroxylated aliphatic hydrocarbons and the low productivity of epoxides. This leads to the use of a large reaction volume and an increase in residence time in the reactor to achieve high conversion. The presence of water, which enters into intermolecular interactions with reagents, negatively affects the speed of the process.

The objectives of this method are to increase the rate of formation of propylene chlorohydrins and the performance of propylene oxide.

This problem is solved by the method of producing propylene oxide, in which the formation of propylene chlorohydrins occurs when propylene glycol and hydrogen chloride gas are reacted at elevated temperature in the presence of carboxylic acids, while water containing reaction products is distilled off and the reaction products are removed from the hydrochlorination reactor by a side outlet. The distillation of water from the reactor allows you to increase the rate of hydrochlorination of propylene glycol by increasing the activity of the chlorine anion, which is solvated by water.

The following examples illustrate the method.

Example 1 (prototype)

The process was carried out in a 43 ml glass reactor equipped with a heating system, a stirrer, a bubbler for supplying hydrogen chloride and a reflux condenser for condensing the evaporated reaction mass.

A mixture of propylene glycol with a catalyst — acetic acid — was fed continuously into the reactor in an amount of 42.27 g / h and 1.31 g / h (3% by weight), respectively. Hydrogen chloride gas was supplied through a bubbler in an amount of 21.14 g / h. The process temperature was 105 ° C. The reaction products were taken through the side outlet of the reactor in level to the receiver.

The resulting solution in an amount of 64.72 g / h, which contained 42.48% of the mass. propylene chlorohydrin from the hydrochlorination reactor was fed to a dehydrochlorination column, the cube of which was heated by steam. A solution of propylene chlorohydrins reacted with 20% of the mass. a solution of sodium hydroxide, which was filed in an amount of 121.63 g / h

The resulting propylene oxide was distilled off from the top of the column in an amount of 16.71 g / h. 169.64 g / h of solution was taken from the bottom of the column: water - 108.58 g / h, propylene glycol - 20.38 g / h, sodium chloride - 33.88 g / h, sodium acetate - 1.28 g / h, sodium hydroxide - 0.28 g / h, high molecular weight organic compounds - 0.24 g / h.

According to the results of the experiment, the rate of formation of propylene chlorohydrins and the plant productivity of propylene oxide were calculated.

The results of the example are shown in the table.

Example 2

The process was carried out in a 43 ml glass reactor equipped with a heating system, a stirrer, a bubbler for supplying hydrogen chloride and a direct refrigerator.

A mixture of propylene glycol with a catalyst — acetic acid — in an amount of 41.93 g / h and 1.26 g / h (3 wt%), respectively, was continuously fed into the reactor. Hydrogen chloride gas was supplied through a bubbler in an amount of 21.26 g / h. The process temperature was 105 ° C. The reaction products were taken through the side outlet of the reactor in level to the receiver. The distilled water containing reaction products was condensed into a receiver. The contents of both receivers were combined and received a solution in the amount of 64.45 g / h, containing 78.99% of the mass. propylene chlorohydrins.

The resulting solution was fed to a dehydrochlorination column, the cube of which was heated with steam. A solution of propylene chlorohydrins reacted with 20% of the mass. a solution of sodium hydroxide, which was filed in an amount of 122.32 g / h

The resulting propylene oxide was distilled off from the top of the column in an amount of 30.93 g / h. 155.84 g / h of solution were taken from the cube of the column: water - 118.82 g / h, propylene glycol - 1.18 g / h, sodium chloride - 34.07 g / h, sodium acetate - 1.23 g / h, sodium hydroxide - 0.32 g / h, high molecular weight organic compounds - 0.22 g / h.

According to the results of the experiment, the amount of distilled water from the reaction mass was determined and the rate of formation of propylene chlorohydrins and the performance of the plant for propylene oxide were calculated.

The results of the example are shown in the table.

Example 3

The process was carried out analogously to example 2, but the catalyst was propionic acid in an amount of 3% of the mass. from propylene glycol.

The results of the example are shown in the table.

Example 4

The process was carried out analogously to example 2, but the catalyst was adipic acid in an amount of 3% of the mass. from propylene glycol.

The results of the example are shown in the table.

Example 5

The process was carried out analogously to example 2, but the process temperature was 100 ° C. The results of the example are shown in the table.

Example 6

The process was carried out analogously to example 2, but the process temperature was 110 ° C. The results of the example are shown in the table.

The results of examples 1-6 No. The amount of distilled water, g / h The rate of formation of propylene chlorohydrins, mol / (l · h) The performance of propylene oxide, g / h 1 (prototype) No stripping 6.73 16.71 2 7.57 12.53 30.93 3 7.46 11.84 30.31 four 7.39 13.28 31.80 5 5.81 8.53 21.06 6 8.83 18.68 31.74

Thus, the results presented in the table show that carrying out the process of producing propylene oxide while distilling off the water containing the reaction products and withdrawing the reaction products from the propylene glycol hydrochlorination reactor with a side outlet allows increasing the rate of formation of propylene chlorohydrins and the performance of propylene oxide.

Claims (1)

A method of producing propylene oxide, including hydrochlorination of propylene glycol in the presence of carboxylic acids at elevated temperature and subsequent dehydrochlorination of the obtained propylene chlorohydrins with sodium hydroxide, characterized in that the hydrochlorination of propylene glycol is carried out with simultaneous distillation of the water containing the reaction products and the withdrawal of reaction products from the side hydrochlorination reactor.