Process for preparing polyoxymethylene dimethyl ethers from formaldehyde and methanol in aqueous solutions

摘要

Process for preparing polyoxymethylene dimethyl ethers having ≥3 oxymethylene units (OME_n≥3), comprising the steps:;(i) introduction of formaldehyde, methanol and water into a reactor R and reaction to give a reaction mixture containing formaldehyde, water, methylene glycol, polyoxymethylene glycols, methanol, hemiformals, methylal (OME_n=1) and polyoxymethylene dimethyl ethers (OME_n1);(ii) introduction of the reaction mixture into a reactive distillation column K1 and separation into a low boiler fraction F1 containing formaldehyde, water, methylene glycol, polyoxymethylene glycols, methanol, hemiformals, methylal (OME_n=1) and polyoxymethylene dimethyl ethers having from 2 to 3 oxymethylene units (OME_n=2-3) and a high boiler fraction F2 containing polyoxymethylene dimethyl ethers having more than two oxymethylene units (OME_n≥3).