# US 5,706,674 A · Argon recovery from silicon crystal furnace > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,674 A - Document ID: US5706674A - Status: Granted - Kind: A - Application number: 08/785,515 - Filed: 1997-01-17 - Granted: 1998-01-13 - Earliest claimed: 1997-01-17 - Assignees: Air Products and Chemicals, Inc. - Inventors: Thomas Hsiao-Ling Hsiung; Zbigniew Tadeusz Fidkowski; Rakesh Agrawal - Web page: https://patentgrep.com/patent/US5706674A ## CPC - F25J 3/08: Separating gaseous impurities from gases or gaseous mixtures {or from liquefied gases or liquefied gaseous mixtures}(cold traps B01D8/00) - C01B 23/0094: {Combined chemical and physical processing} - C30B 15/00: Single-crystal growth by pulling from a melt, e.g. Czochralski method (under a protective fluid C30B27/00) - C30B 29/06: Silicon - F25J 3/0285: {of argon} - C01B 2210/0004: by oxidation - C01B 2210/0006: by reduction - C01B 2210/0014: by adsorption in solids - C01B 2210/0045: Oxygen - C01B 2210/005: Carbon monoxide - F25J 2200/04: in a dual pressure main column system - F25J 2200/72: Refluxing the column with at least a part of the totally condensed overhead gas - F25J 2215/58: Argon - Y10S 62/924: Argon - F25J: LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS {OR LIQUEFIED GASEOUS} MIXTURES BY PRESSURE AND COLD TREATMENT {OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE (cryogenic pumps F04B37/08; gas storage vessels, gas holders F17; filing vessels with, or discharging from vessels, compressed, liquefied or solidified gases F17C; refrigeration machines, plants, or systems F25B)} - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract The present invention is directed to two embodiments of a process for recycling an impure argon effluent from a silicon crystal growing furnace using cryogenics. The first embodiment uses cryogenic distillation techniques, and the second embodiment uses cryogenic adsorption, both of which use catalytic treatments and adsorption in conjunction with their cryogenic process steps to provide a pure argon recycle stream for a silicon crystal growth furnace. ## Claims ### Claim 1 A process for the recovery and purification of impure argon containing residual dopants from a silicon crystal growth furnace using the steps of: (1) contacting the impure argon with a deoxygenation catalyst and hydrogen to remove any contained oxygen; (2) contacting the impure argon with a zeolitic adsorbent selective to the adsorption of water and carbon dioxide from the impure argon to remove any water and carbon dioxide from the impure argon; (3) further purifying the impure argon in a cryogenic temperature separation to remove remaining impurities from the impure argon and produce an argon product stream having a purity of at least 99.5% by volume; the improvement comprising removing dopants from the impure argon prior to step (1) by contact of the impure argon with a liquid absorbent to strip the dopants from the impure argon. ### Claim 2 (depends on 1) The process of claim 1 wherein the cryogenic temperature separation is a cryogenic dual column distillation separation with a high pressure distillation column separation of nitrogen and carbon monoxide from the impure argon and a low pressure distillation column separation of hydrocarbons from the impure argon. ### Claim 3 (depends on 2) The process of claim 2 wherein the cryogenic temperature is no greater than -260.degree. F. ### Claim 4 (depends on 1) The process of claim 1 wherein the impure argon after contact with the deoxygenation catalyst is contacted with a cupric oxide catalyst to convert carbon monoxide and hydrogen to water and carbon dioxide. ### Claim 5 (depends on 4) The process of claim 4 wherein the cupric oxide catalyst is contained in two parallel switching adsorbent beds with one bed contacting the impure argon while the other bed is being regenerated with an oxygen containing inert gas and portion of the argon product stream. ### Claim 6 (depends on 4) The process of claim 4 wherein the cryogenic temperature separation is a cryogenic selective adsorption of nitrogen and hydrocarbons from the impure argon on a calcium X-zeolite adsorbent. ### Claim 7 (depends on 6) The process of claim 6 wherein the cryogenic temperature is no greater than -220.degree. F. ### Claim 8 (depends on 1) The process of claim 1 wherein the argon product stream is recycled to the silicon crystal growth furnace. ### Claim 9 (depends on 1) The process of claim 1 wherein the liquid absorbent is selected from the group consisting of sodium hydroxide, potassium hydroxide and mixtures thereof. ### Claim 10 (depends on 1) The process of claim 1 wherein the cryogenic temperature is no greater than -200.degree. F. ### Claim 11 A process for the recovery and purification of impure argon containing residual dopants from a silicon crystal growth furnace using the steps of: (1) contacting the impure argon with a deoxygenation catalyst and hydrogen to remove any contained oxygen; (2) contacting the impure argon with a zeolitic adsorbent selective to the adsorption of water and carbon dioxide from the impure argon to remove any water and carbon dioxide from the impure argon; (3) introducing the impure argon into a cryogenic distillation column to separate nitrogen from the impure argon to produce an argon product stream having a purity of at least 99.5% by volume; and (4) recycling the argon product stream to the silicon crystal growth furnace; the improvement comprising removing the dopants from the impure argon prior to step (1) and performing step (3) in a cryogenic dual column distillation separation with a high pressure distillation column separation of nitrogen, hydrogen and carbon monoxide from the impure argon and a low pressure distillation column separation of hydrocarbons from the impure argon. ### Claim 12 (depends on 11) The process of claim 11 wherein the zeolite adsorbent is contained in two parallel switching adsorbent beds with one bed contacting the impure argon while the other bed is being regenerated by elevated temperature. ### Claim 13 A process for the recovery and purification of impure argon containing residual dopants from a silicon crystal growth furnace using the steps of: (1) contacting the impure argon with a deoxygenation catalyst and hydrogen to remove any contained oxygen; (2) contacting the impure argon with a cupric oxide catalyst to convert carbon monoxide and hydrogen to water and carbon dioxide; (3) contacting the impure argon with a zeolitic adsorbent selective to the adsorption of water and carbon dioxide from the impure argon to remove any water and carbon dioxide from the impure argon; (4) contacting the impure argon at a cryogenic temperature with calcium X-zeolite adsorbent to remove nitrogen and hydrocarbons from the impure argon and produce an argon product stream having a purity of at least 99.5% by volume; and (5) recycling the argon product stream to the silicon crystal growth furnace; the improvement comprising removing the dopants from the impure argon prior to step (1) by contact of the impure argon with aqueous sodium hydroxide to strip the dopants from the impure argon. ### Claim 14 (depends on 13) The process of claim 13 wherein the calcium X-zeolite adsorbent is contained in two parallel switching adsorbent beds with one bed contacting the impure argon while the other bed is being regenerated with a portion of the argon product stream. ### Claim 15 (depends on 13) The process of claim 13 wherein the zeolite adsorbent is contained in two parallel switching adsorbent beds with one bed contacting the impure argon while the other bed is being regenerated initially with nitrogen gas and then by a portion of the argon product stream.