# US 2014/0194540 A1 · Methods and Apparatus for Sulfur Management in Catalytic Mixed-Alcohol Synthesis > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0194540 A1 - Document ID: US20140194540A1 - Status: Published application - Kind: A1 - Application number: 14/240,338 - Filed: 2012-08-21 - Published: 2014-07-10 - Earliest claimed: 2011-08-22 - Assignees: Albemarle Corporation - Inventors: Ronald C. Stites; Shakeel H. Tirmizi; Karl Kharas - Web page: https://patentgrep.com/patent/US20140194540A1 ## CPC - C07C 29/156: containing iron group metals, platinum group metals or compounds thereof - C07C 29/15: by reduction of oxides of carbon exclusively - C07C 29/151: with hydrogen or hydrogen-containing gases - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS ## Abstract The present invention provides methods to maintain selectivity to ethanol from syngas during mixed-alcohol synthesis when methanol is being recycled. In some variations, syngas is fed to an alcohol-synthesis reactor that contains a sulfided metal catalyst, and methanol is separated from ethanol to form a methanol recycle stream that contains sulfur-containing compounds. Recycling the methanol stream back to the alcohol-synthesis reactor allows for adding sulfur to, or reducing sulfur loss from, the sulfided metal catalyst. Optionally, additional sulfur compounds may be introduced to maintain sulfur levels in sulfided metal catalysts. Preferred sulfiding agents, concentrations, and recycle strategies are disclosed herein. ## Claims ### Claim 1 A method of producing ethanol from syngas, said method comprising: (a) feeding syngas to an alcohol-synthesis reactor that contains a sulfided metal catalyst, under suitable conditions for converting said syngas into an intermediate stream comprising methanol, ethanol, and one or more sulfur-containing compounds; (b) sending at least part of said intermediate stream to a separation unit, whereby at least a portion of said methanol is separated from said ethanol to form a methanol recycle stream and an ethanol product stream, and wherein at least a portion of said sulfur-containing compounds are contained in said methanol recycle stream; (c) recycling some or all of said methanol recycle stream back to said alcohol-synthesis reactor to add sulfur to, or reduce sulfur loss from, said sulfided metal catalyst; and (d) optionally introducing one or more additional sulfur compounds, into said alcohol-synthesis reactor and/or into said methanol recycle stream, to add sulfur to, or reduce sulfur loss from, said sulfided metal catalyst. ### Claim 2 (depends on 1) The method of claim 1, wherein said sulfided metal catalyst is a base-promoted cobalt-molybdenum-sulfur catalyst. ### Claim 3 (depends on 1) The method of claim 1, wherein said separation unit includes one or more distillation columns. ### Claim 4 (depends on 3) The method of claim 3, wherein one of said distillation columns is adapted for separation of both methanol and sulfur-containing compounds. ### Claim 5 (depends on 1) The method of claim 1, comprising introducing one or more additional sulfur compounds into said alcohol-synthesis reactor to add sulfur to, or reduce sulfur loss from, said sulfided metal catalyst. ### Claim 6 (depends on 1) The method of claim 1, comprising introducing one or more additional sulfur compounds into said methanol recycle stream to add sulfur to, or reduce sulfur loss from, said sulfided metal catalyst. ### Claim 7 (depends on 1) The method of claim 1, wherein at least one of said sulfur-containing compounds is selected from the group consisting of methyl sulfide, dimethyl sulfide, dimethyl disulfide, di-tert-butyl disulfide, and any analogues, derivatives, oligomers, polymers, reaction products, and combinations thereof. ### Claim 8 (depends on 1, 5) The method of any one of claims 1, 5, or 6, wherein at least one of said additional sulfur compounds is selected from the group consisting of methyl sulfide, dimethyl sulfide, dimethyl disulfide, di-cert-butyl disulfide, and any analogues, derivatives, oligomers, polymers, and combinations thereof. ### Claim 9 The method of any one of the preceding claims, wherein said methanol recycle stream has a sulfur-atom concentration of at least 10 ppm S. ### Claim 10 (depends on 9) The method of claim 9, wherein said sulfur-atom concentration is between about 50 ppm S and about 500 ppm S. ### Claim 11 (depends on 10) The method of claim 10, wherein said sulfur-atom concentration is between about 100 ppm S and about 300 ppm S. ### Claim 12 (depends on 11) The method of claim 11, wherein said sulfur-atom concentration is less than 200 ppm S. ### Claim 13 (depends on 1) The method of claim 1, wherein said methanol recycle stream has a sulfur-atom concentration optimized for the extent of said recycling some or all of said methanol recycle stream back to said alcohol-synthesis reactor. ### Claim 14 (depends on 1, 5) The method of any one of claim 1, 5, or 6, wherein said step (c) and/or said step (d) retards or eliminates a mechanism by which ethanol selectivity is otherwise lost as a result of recycling said methanol. ### Claim 15 (depends on 14) The method of claim 14, wherein said mechanism includes at least partial conversion of said sulfided metal catalyst to metal carbides. ### Claim 16 A method of producing ethanol from syngas, said method comprising: (a) feeding syngas to an alcohol-synthesis reactor that contains a sulfided metal catalyst, under suitable conditions for converting said syngas into an intermediate stream comprising methanol and ethanol; (b) co-feeding hydrogen sulfide with said syngas to said alcohol-synthesis reactor, to add sulfur to, or reduce sulfur loss from, said sulfided metal catalyst; (c) sending at least part of said intermediate stream to a separation unit, whereby at least a portion of said methanol is separated from said ethanol to form a methanol recycle stream and an ethanol product stream; and (d) recycling some or all of said methanol recycle stream back to said alcohol-synthesis reactor, wherein said hydrogen sulfide is fed in step (b) at a concentration between about 50 ppm H2S and about 400 ppm H2S. ### Claim 17 (depends on 16) The method of claim 16, wherein said hydrogen sulfide is fed in step (b) at a concentration between about 50 ppm H2S and about 250 ppm H2S. ### Claim 18 (depends on 16) The method of claim 16, wherein said hydrogen sulfide is fed in step (b) at a concentration between about 75 ppm H2S and about 150 ppm H2S. ### Claim 19 (depends on 16) The method of claim 16, wherein said hydrogen sulfide is fed in step (b) at a concentration between about 90 ppm H2S and about 130 ppm H2S. ### Claim 20 (depends on 16) The method of claim 16, wherein said hydrogen sulfide is fed in step (b) at a concentration optimized for the extent of said recycling some or all of said methanol recycle stream back to said alcohol-synthesis reactor. ### Claim 21 (depends on 16) The method of claim 16, wherein said hydrogen sulfide is fed in step (b) at a concentration optimized for retarding or eliminating a mechanism by which ethanol selectivity is otherwise lost as a result of recycling said methanol. ### Claim 22 (depends on 16) The method of claim 16, wherein said hydrogen sulfide is fed in step (b) at a concentration optimized for reducing or eliminating conversion of said sulfided metal catalyst to metal carbides. ### Claim 23 A method of producing ethanol from syngas, said method comprising: (a) feeding syngas to an alcohol-synthesis reactor that contains a sulfided metal catalyst, under suitable conditions for converting said syngas into an intermediate stream comprising methanol and ethanol; (b) co-feeding hydrogen sulfide with said syngas to said alcohol-synthesis reactor, to add sulfur to, or reduce sulfur loss from, said sulfided metal catalyst; (c) sending at least part of said intermediate stream to a separation unit, whereby at least a portion of said methanol is separated from said ethanol to form a methanol recycle stream and an ethanol product stream; and (d) recycling some or all of said methanol recycle stream back to said alcohol-synthesis reactor, wherein said hydrogen sulfide is fed in step (b) at a concentration optimized for the specific extent of said recycling some or all of said methanol recycle stream back to said alcohol-synthesis reactor. ### Claim 24 An apparatus adapted for carrying out the method of any one of the preceding claims.