Production process for preparing dimethyl ether by methanol reaction fractional distillation stepwise reaction

Abstract

The invention provides a production process for preparing dimethyl ether through stepwise reaction by a methanol reactive distillation method, comprising the following steps: the material methanol is pressurized to 0.6-1.0MPa by a charge pump, after being heated by a heat exchanger and a sewage heat exchanger, part of the methanol is sent to a dimethyl ether reactive rectification tower by a liquid-phase raw material inlet, and most part is sent to a rectification section of a methanol vaporization and recovery tower for vaporization; the vaporized methanol is heated to 130 DEG C by a heater and sent to a gas-phase inlet of a dimethyl ether reactive rectification tower reactor and quickly react with a liquid-phase catalyst at 130-200 DEG C and at the pressure of 0.05-1.0 MPa; the products dimethyl ether, water vapor and the unreacted methanol go upwards to pass through a washing section to contact with backflow methanol for washing and removing heavy phase, and then are sent to the rectification section for rectifying and removing water and the methanol; the water is pumped from a water outlet of the dimethyl ether reactive rectification tower, part of the water exchanges heat by the heat exchanger and then flows back, the other part thereof is sent to a stripping section of the methanol vaporization and recovery tower for circularly removing the methanol by a reboiler, and sewage is discharged from the bottom of the methanol vaporization and recovery tower, sent to a sewage workshop for treatment after exchanging heat; the dimethyl ether with the water and the methanol removed is cooled to normal temperature, is kept at the pressure or pressurized to over 0.6MPa by a compressor, and is sent to the dimethyl ether rectification tower; and the rectified dimethyl ether runs through the heat exchanger, a water cooler and a dimethyl ether reflux accumulator to obtain the high-purity dimethyl ether product.

Description

1. Technical field [0001] The invention provides a production process for preparing dimethyl ether by a step-by-step reaction of a methanol reactive distillation method, which belongs to the field of coal chemical industry. 2. Background technology [0002] At present, the production process of DME mainly includes one-step method and two-step method. [0003] The one-step method is to combine the three-step reactions of water gas shift reaction, methanol synthesis reaction and methanol dehydration reaction into one step under the action of the dual-functional composite catalyst of methanol synthesis and methanol dehydration, and realize the production of dimethyl ether in the same reactor. Preparation Process. At present, the technology of one-step method is still immature, and large-scale industrialization is facing many problems. [0004] The two-step method is to produce methanol first, and then dehydrate methanol. The two-step method has two processes, one is methanol...

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Problems solved by technology

[0009] Patent application CN1111231A discloses a process for synthesizing dimethyl ether by catalytic distillation. Sulfuric acid is used as a dehydration catalyst, and dimethyl ether is prepared by catalytic distillation with a rectification column in a kettle type, so that the reaction product does not contain methyl sulfate toxic substances and acidic substances. The process is simple, and the anti-corrosion requirements of the equipment are reduced, but there is also the fact that the raw material methanol is directly added from the middle and lower part of the rectification column, and the water generated by the reaction returns to the reaction kettle while the heavy phase is removed. There are also defects that are difficult to mass-produce

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