| 摘要 |
<p>A process for preparing tri- and tetraoxymethylene glycol dimethyl ether (POMDME<sub>n=3,4</sub>) by reacting formaldehyde with methanol and subsequently working up the reaction mixture by distillation, comprising the steps of: a) feeding aqueous formaldehyde solution and methanol into a reactor and reacting to give a mixture a comprising formaldehyde, water, methylene glycol (MG), polyoxymethylene glycols (MG<sub>n>1</sub>), methanol, hemiformals (HF), methylal (POMDME<sub>n=1</sub>) and polyoxymethylene glycol dimethyl ethers (POMDME<sub>n>1</sub>); b) feeding the reaction mixture a into a first distillation column and separating into a low boiler fraction b1 and a high boiler fraction b2 comprising formaldehyde, water, methanol, polyoxymethylene glycols, hemiformals and polyoxymethylene glycol dimethyl ethers (POMDME<sub>n>1</sub>); c) feeding the high boiler fraction b2 into a second distillation column and separating into a low boiler fraction c1 comprising formaldehyde, water, methylene glycol, polyoxymethylene glycols, methanol, hemiformals, di-, tri- and tetraoxymethylene glycol dimethyl ether (POMDME<sub>n=2,3,4</sub>) and a high boiler fraction c2; d) feeding the low boiler fraction c1 into a third distillation column and separating into a low boiler fraction d1 and a high boiler fraction d2 substantially consisting of formaldehyde, water, methylene glycol, polyoxymethylene glycols, tri- and tetraoxymethylene glycol dimethyl ether (POMDME<sub>n=3,4</sub>); e) feeding the high boiler fraction d2 into a phase separation apparatus and separating into an aqueous phase e1 substantially consisting of formaldehyde, water, methylene glycol and polyoxymethylene glycols, and an organic phase e2 comprising tri- and tetraoxymethylene glycol dimethyl ether (POMDME<sub>n=3,4</sub>); f) feeding the organic phase e2 into a fourth distillation column and separating into a low boiler fraction f1 substantially consisting of formaldehyde, water, methylene glycol and polyoxymethylene glycols, and a high boiler fraction f2 substantially consisting of tri- and tetraoxymethylene glycol dimethyl ether (POMDME<sub>n=3,4</sub>).</p> |
