Reactive distillation-vapor permeation coupling process for polyoxymethylene dimethyl ether synthesis

Abstract

The invention relates to a reactive distillation-vapor permeation coupling process for the polyoxymethylene dimethyl ether synthesis. According to the coupling process, a methylal and a formaldehyde solution, a hydrous trioxymethylene, a hydrous paraformaldehyde, a hydrous gaseous formaldehyde or a mixture of substances are used as raw materials, a polyoxymethylene dimethyl ether mixed product with multiple polymerization degrees is obtained by carrying out a reaction under the action of an acidic catalyst, by the separation action of a polyoxymethylene dimethyl ether reactive distillation tower, reaction products with polymerization degrees of more than 2 are extracted out from the tower kettle, DMM2 with low polymerization degrees, unreacted methylal, reaction by-product methanol, and water in the reaction system are extracted out from the tower top, the extracted products from the tower kettle is subjected to product refining tower separation, and the target product DMM3-5 is obtained. According to the process, defects in the existing process that the target product DMM3-5 has low yield, the circulation amount in the process is large, the energy consumption is high, and the likeare solved, the reaction balance limit can be broken, the conversion rate of the raw material and the selectivity and yield of DMM3-5 are greatly improved.

Description

technical field [0001] The invention belongs to the technical field of chemical production technology and equipment, and relates to the synthesis and separation and purification of polyoxymethylene dimethyl ether, in particular to a reactive distillation-steam permeation coupling process device for synthesizing polyoxymethylene dimethyl ether and method. Background technique [0002] With the increase of diesel demand, the exhaust emission problem is becoming more and more serious. Diesel combustion performance can be improved by adding appropriate additives, which will bring economic and environmental benefits. According to the use characteristics of compression ignition of diesel engines and the characteristics of oxygen-containing fuels, oxygen-containing compounds can reduce the soot and soot during diesel combustion, and are suitable as diesel additives. Polyoxymethylene dimethyl ether has a relatively high oxygen content and cetyl octane number. Adding an appropriate...

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Problems solved by technology

These methods all have anhydrous chain growth reactant (as, paraformaldehyde, gas-phase formaldehyde, paraformaldehyde) reaction raw material price is higher, product economy is not high, lacks market competitiveness

Patent CN108383696A proposes a method for preparing polyoxymethylene dimethyl ether by reacting aqueous paraformaldehyde and methylal, but the preparation of polyoxymethylene dimethyl ether in this method uses a reactor, and the product components after the reaction are complex and There is still a small amount of water, the subsequent separation is more difficult, and the energy consumption required to obtain DMM3~5 in the process is relatively large, and the product economy is still limited

Patent CN106748678A proposes a process device and method for the joint production of high-concentration formaldehyde and gas-phase formaldehyde method polyoxymethylene dimethyl ether. Although this method can solve the problem of gas-phase formaldehyde outsourcing and transportation, but the introduction of isooctyl alcohol in the process, The process of preparing gas-phase formaldehyde has high energy consumption, and the reaction of polyoxymethylene dimethyl ether uses a reactor, the yield of DMM3-5 is low, and the subsequent separation process is complicated and energy-consuming

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