System and method for continuously producing polyoxymethylene dialkyl ethers

摘要

A reaction system and method for producing polyoxymethylene dialkyl ethers (RO(CH2O)nR, n=1-8) by continuous acetalation of formaldehyde and aliphatic alcohol in the presence of an acid ionic liquid catalyst. The reaction system includes an acetalation reaction unit, a product separation unit, and a catalyst regeneration unit. The recyclable material and catalyst are separated by combining extraction and rectification, and a recovery rate of more than 99% for the catalyst is achieved. Water, as the byproduct, is separated from the reaction system by destroying the azeotrope of water, alcohol, aldehyde, and RO(CH2O)nR, so that the product separation and catalyst regeneration are facilitated and the catalytic cycle is achieved.

主权项

1. A reaction system for continuously producing polyoxymethylene dialkyl ethers, comprising:
an acetalation reaction unit, comprising a single or multi-stage reactor and a heat exchanger, wherein the reactor is in flow communication with the heat exchanger, and a reaction solution circulates between the reactor and the heat exchanger; an acetalation reaction of formaldehyde and aliphatic alcohol is continuously conducted by using an acid ionic liquid as a catalyst in the reactor; a product separation unit, comprising an extraction column and a single or multi-stage rectification column connected to each other in series, wherein a light phase and a heavy phase are extracted from a reaction effluent discharged from the acetalation reaction unit by using an extractant in the product separation unit; the light phase is a product phase containing recyclable materials, the extractant, and products RO(CH2O)3-8R wherein R is CH3, CH2CH3, CH2CH2CH3, or CH(CH3)2; and the heavy phase is an aqueous catalyst solution; and a catalyst regeneration unit, comprising a film separator, wherein the catalyst regeneration unit receives the heavy phase separated from the product separation unit, and the catalyst in the heavy phase is recycled to the acetalation reaction unit after dehydration in the catalyst regeneration unit.