Reactive distillation process device and method for synthesis of PODEn (polyoxymethylene dimethyl ethers)

Abstract

The invention provides a reactive distillation process device and method for synthesis of PODEn (polyoxymethylene dimethyl ethers). According to the method, industrial methylal for product chain termination and one or a mixture of two or more of trioxymethylene, paraformaldehyde and gas-phase formaldehyde for product chain propagation are taken as raw materials, no water exits in a reaction system, a PODEn mixed product with multiple degrees of polymerization is obtained through a reaction under the action of an acidic catalyst, a reaction product with the degree of polymerization higher than2 is recovered from the column bottom under the separation action of a PODEn reactive distillation reaction column, and DMM2 with low degree of polymerization and incompletely reacted methylal are recovered from the column top; a product recovered from the column bottom is separated by a production refinery column, a target product DMM3-5 is obtained, DMM2 with low degree of polymerization and DMM6-10 with high degree of polymerization are returned to the PODEn reactive distillation reaction column; incompletely reacted methylal is recycled as a raw material. By use of the characteristic of reactive distillation, excessive methylal is adopted in the reaction process, the conversion rate of formaldehyde substances is substantially increased, and the selectivity and the yield of DMM3-5 are increased.

Description

technical field [0001] The invention belongs to the technical field of chemical production technology and equipment, and relates to polyoxymethylene dimethyl ether, which is a reactive distillation process device and method for synthesizing polyoxymethylene dimethyl ether. Background technique [0002] Polyoxymethylene dimethyl ether is a low-molecular-weight acetal polymer with methoxy as the main chain, and its structural formula is: CH3O(CH2O)nCH3, referred to as DMMn (or PODEn). When n=3~8 (especially 3~5), the substance has a higher cetane number and oxygen content, and there is no sulfur element in the substance, it is a kind of diesel oxygen enhancer with excellent performance, which can Significantly reduce the emission of carbon monoxide and nitrogen oxides in the exhaust of diesel vehicles, without producing sulfur compounds. At the same time, the addition of the substance can improve the combustion performance of diesel without modifying the engine of the vehicle...

AI Technical Summary

Problems solved by technology

However, the preparation of existing anhydrous paraformaldehyde requires extraction and multi-step rectification processes, the manufacturing cost is relatively high, the market price of anhydrous paraformaldehyde is relatively high, and the preparation process of polyoxymethylene dimethyl ether is economically limited. Moreover, the reaction in the reactor is still limited by the reaction balance, the reaction conversion rate and target product selectivity are still not high, the flow rate of the circulating stream is relatively large, and the process economy needs to be further improved

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