Process for methanol production
First Claim
1. In a methanol synthesis process wherein methanol is synthesized from a synthesis gas comprising hydrogen and carbon dioxide by passing said synthesis gas over a methanol synthesis catalyst at methanol-forming conditions to form a gaseous mixture including methanol, water and unreacted carbon dioxide, said gaseous mixture is cooled, methanol and water are condensed therefrom and separated from the uncondensed gaseous mixture, a portion of said uncondensed gaseous mixture is removed as purge gas and the remaining uncondensed gaseous mixture is recycled to contact said methanol synthesis catalyst, the improvement comprising contacting said purge gas with the outside surfaces of a plurality of hollow fiber membranes selectively permeable to both hydrogen and carbon dioxide to form a permeant gas stream depleted in hydrogen and carbon dioxide and a permeate gas stream enriched in both said gases, and combining said enriched permeate gas stream with said synthesis gas.
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Abstract
An improved methanol synthesis process is provided wherein synthesis gas containing hydrogen and carbon dioxide is passed over a methanol synthesis catalyst, cooled to condense methanol and water in the reacted gas, the liquids separated, a purge gas stream removed while the remaining reacted gas is recycled to the synthesis catalyst, the purge gas separated by contacting the outer surfaces of a plurality of hollow fiber membranes selectively permeable to hydrogen and carbon dioxide to form a permeant gas depleted in hydrogen and carbon dioxide and a permeate gas enriched in said gases and the enriched permeate gas is combined with the synthesis gas. In an optional embodiment, methanol vapor is first recovered from the purge gas prior to contacting the selectively permeable membranes, preferably by a water scrub.
51 Citations
30 Claims
- 1. In a methanol synthesis process wherein methanol is synthesized from a synthesis gas comprising hydrogen and carbon dioxide by passing said synthesis gas over a methanol synthesis catalyst at methanol-forming conditions to form a gaseous mixture including methanol, water and unreacted carbon dioxide, said gaseous mixture is cooled, methanol and water are condensed therefrom and separated from the uncondensed gaseous mixture, a portion of said uncondensed gaseous mixture is removed as purge gas and the remaining uncondensed gaseous mixture is recycled to contact said methanol synthesis catalyst, the improvement comprising contacting said purge gas with the outside surfaces of a plurality of hollow fiber membranes selectively permeable to both hydrogen and carbon dioxide to form a permeant gas stream depleted in hydrogen and carbon dioxide and a permeate gas stream enriched in both said gases, and combining said enriched permeate gas stream with said synthesis gas.
- 12. In a methanol synthesis process wherein methanol is synthesized from a synthesis gas comprising hydrogen and carbon dioxide by passing said synthesis gas over a methanol synthesis catalyst at methanol-forming conditions to form a gaseous mixture including methanol, water and unreacted carbon dioxide, said gaseous mixture is cooled, methanol and water are condensed therefrom and separated from the uncondensed gaseous mixture, a portion of said uncondensed gaseous mixture is removed as purge gas and the remaining uncondensed gaseous mixture is recycled to contact said methanol synthesis catalyst, the improvement comprising contacting said purge gas with the outside surfaces of a plurality of hollow fiber membranes selectively permeable to both hydrogen and carbon dioxide and having an outside diameter of from about 150 to 800 microns and a wall thickness of from about 50 to 300 microns to form a permeant gas stream depleted in hydrogen and carbon dioxide and a permeate gas stream enriched in both said gases, and combining said enriched permeate gas stream with said synthesis gas.
- 23. In a methanol synthesis process wherein methanol is synthesized from a synthesis gas comprising hydrogen and carbon dioxide by passing said synthesis gas over a methanol synthesis catalyst at methanol-forming conditions to form a gaseous mixture including methanol, water and unreacted carbon dioxide, said gaseous mixture is cooled, methanol and water are condensed therefrom and separated from the uncondensed gaseous mixture, a portion of said uncondensed gaseous mixture is removed as purge gas and the remaining uncondensed gaseous mixture is recycled to contact said methanol synthesis catalyst, the improvement comprising contacting said purge gas with the outside surfaces of a plurality of hollow fiber membranes selectively permeable to both hydrogen and carbon dioxide and having an outside diameter of from about 150 to 800 microns and a wall thickness of from about 50 to 300 microns to form a permeant gas stream depleted in hydrogen and carbon dioxide and a permeate gas stream enriched in both said gases, adding carbon dioxide gas to the enriched permeate gas stream, and combining said enriched permeate gas stream with said synthesis gas.
Specification