Processes for the production of methanol using sweep-based membrane separation steps

摘要

Disclosed herein are methanol production processes that include a sweep-based membrane separation step using a membrane that is selective to carbon dioxide over hydrogen. Using the processes of the invention, the efficiency of methanol production from syngas is increased by reducing the compression requirements of the process and/or improving the methanol product yield. In certain embodiments, a hydrogen-rich stream is generated; this hydrogen-rich stream can be sent for other uses. An additional benefit is that the processes of the invention may debottleneck existing methanol plants if more syngas or carbon dioxide is available, allowing for feed of imported carbon dioxide into the synthesis loop. This is a way of sequestering carbon dioxide.

主权项

1. A methanol synthesis loop production process comprising the following steps:
(a) providing a source of syngas, wherein the syngas has a composition parameter R1, where R1>2; (b) performing a methanol synthesis reaction to react the syngas to produce methanol; (c) performing a condensation step to recover methanol; (d) withdrawing a purge stream from the condensation step to limit the concentration of inerts and excess hydrogen; (e) withdrawing non-condensed methanol synthesis loop syngas from the condensation step; (f) performing a sweep-based membrane separation step comprising,
(i) providing a membrane having a feed side and a permeate side, where the membrane exhibits a selectivity to carbon dioxide over hydrogen,(ii) passing a carbon dioxide-containing gas across the feed side,(iii) passing at least a portion of the methanol synthesis loop syngas as a sweep stream across the permeate side,(iv) withdrawing from the feed side a carbon dioxide-depleted residue stream,(v) withdrawing from the permeate side a carbon dioxide-enriched permeate stream; (g) compressing the permeate stream; and (h) passing the compressed permeate stream to the methanol synthesis reaction.