A kind of method for preparing polyoxymethylene dimethyl ether by fixed-bed reactive distillation

Abstract

The invention discloses a method for preparing polymethoxy dimethyl ether through reaction and rectification of a fixed bed. The method comprises the following steps: (1) preheating trioxymethylene, uniformly mixing the preheated trioxymethylene and methylal, and feeding the trioxymethylene and the methylal which are uniformly mixed into a fixed bed reactor for an etherification reaction; (2) feeding materials after the etherification reaction into a reaction rectifying tower for the reaction and the rectification, and discharging PODE2-8 from the tower bottom of the reaction rectifying tower; (3) transporting the PODE2-8 to a dewatering tower loaded with a 3A molecular sieve for dehydration, then transporting the dehydrated PODE2-8 into a first refining tower, transporting materials which are discharged from the tower bottom of the first refining tower into a second refining tower, discharging PODE3-5 from the tower top of the second refining tower, and discharging PODE6-8 from the tower bottom of the second refining tower. When the method disclosed by the invention is used for preparing the PODE3-8, the yield of the polymethoxy dimethyl ether can reach 95%, wherein the products of the PODE3-8 can reach 80%-95%, and after refinement, the PODE3-5 of which the quality purity reaches 99.9% can be obtained.

Description

technical field [0001] The invention belongs to the technical field of polyoxymethylene dimethyl ether preparation, and in particular relates to a method for preparing polyoxymethylene dimethyl ether by fixed-bed reactive distillation. Background technique [0002] Polyoxymethylene dimethyl ether (PODE 3-8 ) is an internationally recognized new type of environmentally friendly diesel oxygen-containing component that can reduce fuel consumption and reduce exhaust pollution. PODE 3-8 The cetane number is greater than 76, the oxygen content is 47% to 50%, and the boiling range is 153°C to 268°C. It has excellent mutual solubility with diesel oil and can be blended into diesel oil in any proportion to increase the oxygen content of diesel oil and improve Diesel combustion performance, reducing vehicle exhaust pollution by more than 50%, especially greatly reducing SO in exhaust 2 , NO X , CO and CmHn emissions. [0003] Polyoxymethylene dimethyl ether (PODE 3-8 ) can be us...

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Problems solved by technology

[0007] Nowadays, when polyoxymethylene dimethyl ether is synthesized by a fixed bed reactor, the reactive distillation tower generally does not have a side line reactor, and there are the following problems in actual use: first, the reactor is arranged in the tower body, Make tower volume larger, input cost is higher, and influence reaction conversion rate and product yield (also claim productive rate); The 2nd, the catalyst that is installed in the reactor is difficult for loading in the tower, time-consuming and labor-intensive; 3rd, The reaction product in the tower is not easy to separate from the catalyst, and the catalyst is easy to cause corrosion to the tower body; fourth, the use effect is poor, the distribution of the reaction product in the tower is uneven and unstable, the reaction conversion rate and product yield are low, and industrialization The degree is low, and the utilization rate of raw materials is low, and the production cost is high

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