CN1180064A

CN1180064A - Method for producing dimethy ether

Info

Publication number: CN1180064A
Application number: CN97116983A
Authority: CN
Inventors: 刘鸿逵; 张桂荣; 陈文�; 陆峥嵘; 郭连敬
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-10-10
Filing date: 1997-10-10
Publication date: 1998-04-29

Abstract

The production process of dimethyl ether uses methyl alcohol as raw material, and under the condition of low temp. (100-125 deg. C) and normal pressure (0-0.05 MPa) and under the action of new catalyst to proceed esterification and dehydration so as to produce dimethyl ether gas, and said gas is passed through condensation, washing, separation, drying, pressure liquifying and bottling. Said liquified dimethyl ether can be provided for industrial application and domestic application. Said invention mainly solves the technical problems of esterification-dehydration and catalyst regeneration and reaction synchronization, etc., and possesses the advantages of simple process, easy operation, high conversion rate, good quality and less investment, etc..

Description

Process for the production of dimethyl ether

The invention relates to the technical field of synthesis gas, in particular to a method for producing dimethyl ether by using synthetic methanol.

In recent years, the atmospheric ozone layer is seriously damaged due to the heavy use of fluorine-containing refrigerants, aerosols and propellants, ultraviolet radiation is intensified, and the "greenhouse effect" of global warming is threatening the health and survival of human beings. Therefore, the united nations environmental protection organization has called an urgent call: fluorine-containing refrigerants were banned by 2000. The countries of Europe, America, Japan, etc. will develop the third generation refrigerant from 1998. The ministry of chemical industry in China also requires that chlorofluorocarbon refrigerants be stopped as soon as possible, and the development of substitute products is attempted. In view of this, the development and development application of fluorine-free refrigerants are promising. Currently, research and pilot work is underway by the agency of the Ministry of chemical industry on substitutes for chlorofluorocarbons that meet aerosol requirements, and dimethyl ether is the preferred refrigerant for the first time.

The traditional dimethyl ether production method is a gas phase synthesis reaction method: namely, the methanol vapor is prepared by vapor phase dehydration under the action of an aluminum phosphate solid catalyst at 350-400 ℃ and 1.4709 Mpa. However, the process has the defects of high heating temperature, large applied pressure, unstable reaction, low conversion rate, high production cost and the like. In order to overcome the defects, the applicant specially provides the technical scheme of the invention.

The invention aims to: provides a method for producing dimethyl ether with lower heating temperature, low pressure, stable reaction, high conversion rate and low cost.

The technical scheme of the invention is realized as follows: liquid methanol is at a lower temperature: 100 to 125 ℃ and atmospheric pressure: carrying out reaction esterification dehydration under the action of 0-0.50 Mpa gauge pressure and a cationic liquid catalyst to generate dimethyl ether gas, and carrying out condensation, alkali washing, water-gas separation drying, compression, oil-gas separation, cooling and pressure stabilization to obtain dimethyl ether liquid, wherein the chemical reaction formula is as follows:

in the above formula, CH₃OH: methanol, CH₃OCH₃: dimethyl ether.

The reaction characteristics are as follows: the regeneration and reaction (production) processes of the catalyst are synchronous, namely the regeneration of the catalyst is completed while the gas is produced, and the continuity of the production process is realized.

Compared with the prior art, the invention has the following beneficial effects:

① the heating temperature needed in the reaction process is low, the applied pressure is not high, the reaction is mild and stable, the energy consumption is low, and the control is easy.

②, because of using the cationic liquid catalyst, the investment is small, the process is simple and easy to operate, the most outstanding advantage is that the regeneration and reaction (production) process of the catalyst are synchronous, so it not only needs no regeneration process and equipment, but also can greatly improve the quality and quantity of the product and reduce the investment.

③ the present invention adopts the technological route of "gas-solid-gas" in which the contact area of methanol steam and the surface of solid catalyst is limited, so the conversion rate is low, and dimethyl ether gas and reaction gas (synthetic gas) are not easy to separate and purify, and the present invention adopts the technological route of "liquid-gas", so the methanol molecule and the catalyst molecule are fully contacted, so the conversion rate is high, and the dimethyl ether gas is easy to separate from the liquid phase, so the separation and purification are easy.

④ when the dimethyl ether gas is separated from the liquid phase, even if carrying a little unreacted methanol vapor, the dimethyl ether gas is easy to be recovered, thereby reducing the material consumption and the production cost.

Description of the drawings:

FIG. 1 is a flow chart of the production process of the present invention.

The preferred embodiment of the present invention is described below with reference to the accompanying drawings, in which fig. 1:

a. firstly, filling a cationic liquid catalyst into a reaction kettle (2), and then pressing raw material methanol into the reaction kettle (2) through a vane pump (35) and a valve (1) according to a theoretical ratio for reaction: heating the materials to 120 ℃ by a heating pipe (0), and raising the pressure in the kettle to 0.03Mpa to complete esterification and dehydration reaction;

b. then, the raw material methanol is continuously added into the reaction kettle (2) at a low flow rate through the vane pump (35) and the valve (1), the temperature is continuously heated to be within 125 ℃, the valve(3) is opened when the pressure in the kettle is increased to 0.05Mpa, and part of water vapor and unreacted methanol enter the condenser (4) along with the generated dimethyl ether gas and are cooled by cooling water from the cooling water pipe (36);

C. unreacted methanol and a part of water vapor fall into a recovery kettle (6) through a valve (5), the recovery kettle (6) is also heated through a heating pipe (0) to keep the temperature between 70 and 80 ℃, the pressure is maintained between 0 and 0.03MPa, at the moment, the dimethyl ether gas carries a small amount of water vapor and a large part of unreacted methanol in the recovery kettle (6) to enter a condenser (8) through a valve (7), substances left in the recovery kettle (6) are dilute methanol solution, and the dilute methanol is returned to a concentration workshop and is concentrated to a specified concentration for reuse;

d. in the condenser (8), a small amount of steam brought by the dimethyl ether gas from the recovery kettle (6) and most of unreacted methanol are cooled by cooling water from a cooling water pipe (36) and then enter the receiving kettle (10) through a valve (9) to become crude methanol, and the crude methanol is recovered to participate in the reaction or returned to a raw material storage tank;

e. dimethyl ether gas enters an alkaline washing tower (13) through valves (11) and (12) to remove redundant cations, then enters a water washing tower (15) through a valve (14), further removes water through a packing layer on a tower plate, then enters a water-gas separator (18) through valves (16) and (17), further removes water through a drying agent on the tower plate, and enters a compressor (21) through valves (19) and (20) to compress the dimethyl ether gas to 4-6 kg/cm²(gauge pressure) is changed into liquid, the liquid enters an oil-gas separator (24) through valves (22) and (23) to remove oil stains, and then is cooled to normal temperature through a valve (25) and a cooling calandria (26);

f. the dimethyl ether liquid at normal temperature passes through a valve (27), a pressure stabilizing cylinder (28) and a valve (29), is discharged through a valve (37), is sampled and tested to be qualified, and then is stored in a storage tank (31) through a valve (30);

g. and opening the valve (32), starting the vane pump (33), opening the valve (34), and performing bottle distribution, filling and factory leaving.

Claims

1. The production method of the dimethyl ether is characterized by comprising the following steps: liquid methanol is at a lower temperature: 100 to125 ℃ and atmospheric pressure: carrying out reaction esterification and dehydration under the action of 0-0.05 Mpa gauge pressure and a cationic liquid catalyst to generate dimethyl ether gas, and carrying out condensation, alkali washing, water-gas separation and drying, compression, oil-gas separation, cooling and pressure stabilization to obtain the dimethyl ether liquid, wherein the reaction formula is as follows: in the above formula, CH₃OH: methanol, CH₃OCH₃: dimethyl ether.

2. The process for producing dimethyl ether according to claim 1, wherein: the regeneration and reaction (production) processes of the catalyst are synchronous, namely, the regeneration of the catalyst is completed while the gas is produced, so that the continuity of the production process is realized.

3. The process for producing dimethyl ether according to claim 1, wherein the process comprises the following steps:

a. putting a cationic liquid catalyst into a reaction kettle (2), pressing raw material methanol into the reaction kettle (2) by using a vane pump (35) and a valve (1) according to a theoretical ratio for reaction: heating the materials to 120 ℃ by a heating pipe (0), and raising the pressure in the kettle to 0.03Mpa to complete esterification and dehydration reaction;

b. then, the raw material methanol is continuously added into the reaction kettle (2) at a low flow rate through the vane pump (35) and the valve (1), the temperature is continuously heated to be within 125 ℃, the valve (3) is opened when the pressure in the kettle is increased to 0.05Mpa, and at the moment, part of water vapor and unreacted methanol enter the condenser (4) along with the generated dimethyl ether gas and are cooled by cooling water from the cooling water pipe (36);

e. dimethyl ether gas enters an alkaline washing tower (13) through valves (11) and (12) to remove redundant cations, then enters a water washing tower (15) through a valve (14), further removes moisture through a packing layer on a tower plate, then enters a water-gas separation dryer (18) through valves (16) and (17), further removes moisture through a drying agent on the tower plate, and enters a compressor (21) through valves (19) and (20) to compress the dimethyl ether gas to 4-6 kg/cm²(gauge pressure) is changed into liquid, the liquid enters an oil-gas separator (24) through valves (22) and (23) to remove oil stains, and then is cooled to normal temperature through a valve (25) and a cooling calandria (26);