Process for the separation of the gas mixture from the catalytic synthesis of methyl mercaptan

摘要

A process for separating the gas mixture (at 100-150 degrees C and 6-12 bar) produced in the catalytic synthesis of methyl mercaptan MM from hydrogen sulphide (H2S) and methanol, to give MM, dimethyl sulphide (DMS), polysulphides, water, methanol, H2S and inert gas. The process comprises (a) separation of the product gas stream by 2-stage partial condensation into (a1) an aqueous condensate containing methanol and water which is condensed at 55-65 degrees C, (a2) an organic condensate containing H2S, MM and DMS which is condensed at 15-30 degrees C, and (a3) a residual gas stream containing H2S and MM, (b) absorption of MM and DMS from fraction (a3) in a first wash with methanol to give an H2S-rich gas stream which is divided into (b1) a circulating stream and (b2) a discharge stream in a vol. ratio of (5:1)-(20:1), (c) absorption of H2S from stream (b2) in a second wash with fresh methanol, removal of the scrubbed stream from the process and recycling the H2S-containing methanol to stage (b), (d) distillation of the loaded methanol and the aqueous and organic condensates to give H2S as a gaseous top product and the other components as a crude liquid bottom product, and feeding the separated H2S into the circulating gas stream or the residual gas stream, and (e) further distillation of the crude product to give MM, DMS, polysulphides, methanol and water.