Method for removing oxygen from a gas stream

Abstract

A process for removing oxygen from a gas stream and a method of controlling the process are provided herein. The deoxygenation process of the present invention may include the steps of combining a feed stream, such as a natural gas feed stream, with hydrogen and contacting the combined stream with a catalyst composition under conditions sufficient to remove at least a portion of the oxygen from the combined gas. In some cases, the catalyst composition can comprise copper and the conditions of the contacting may be such that at least a portion of the copper remains in a reduced state during deoxygenation. The method of controlling the deoxygenation process described herein includes utilizing measured values of parameters of the deoxygenated stream to control one or more parameters of the feed gas stream introduced into the deoxygenation zone and achieve a desired level of oxygen removal.

We claim: 
     
         1 . A process for removing oxygen from a natural gas stream, said process comprising:
 (a) combining an oxygen-containing natural gas stream with a reducing agent to form a combined gas stream; and   (b) contacting at least a portion of said combined gas stream with at least one copper-containing catalyst in a deoxygenation zone to thereby provide an oxygen-depleted gas stream, wherein said contacting is carried out under conditions sufficient to maintain at least a portion of the copper of said copper-containing catalyst in a reduced state during said contacting.   
     
     
         2 . The process of  claim 1 , wherein said contacting is carried out under conditions sufficient to maintain at least 40 percent of the copper of said copper-containing catalyst in a reduced state during said contacting of step (b). 
     
     
         3 . The process of  claim 1 , wherein said reducing agent comprises hydrogen. 
     
     
         4 . The process of  claim 1 , wherein said contacting of step (b) is carried out at an average temperature of at least about 350° F. and not more than about 480° F. 
     
     
         5 . The process of  claim 1 , wherein the molar ratio of hydrogen to oxygen in said combined gas stream is not 2:1. 
     
     
         6 . The process of  claim 5 , wherein the molar ratio of hydrogen to oxygen in said combined gas stream is less than 2:1. 
     
     
         7 . The process of  claim 1 , wherein the pH of said oxygen-depleted gas stream is at least 5. 
     
     
         8 . The process of  claim 1 , wherein said combining of step (a) is carried out prior to said contacting of step (b). 
     
     
         9 . The process of  claim 1 , wherein said oxygen-containing natural gas stream comprises oxygen in an amount of at least about 50 parts per million by weight (ppmw) and not more than about 15,000, ppmw, based on the total weight of said oxygen-containing natural gas stream. 
     
     
         10 . The process of  claim 1 , further comprising, during at least a portion of said contacting of step (b), adjusting the amount of hydrogen combined with said oxygen-containing natural gas stream. 
     
     
         11 . The process of  claim 1 , wherein said oxygen-containing natural gas stream comprises C 1  to C 6  hydrocarbons in an amount of at least about 25 weight percent, based on the total weight of said oxygen-containing natural gas stream. 
     
     
         12 . The process of  claim 1 , wherein said oxygen-containing natural gas stream comprises less than about 15 weight percent of one or more inert gases selected from the group consisting of nitrogen, neon, xenon, argon, helium, krypton, radon, and combinations thereof. 
     
     
         13 . The process of  claim 1 , further comprising, prior to said combining of step (b), removing at least a portion of one or more sulfur-containing compounds from a natural gas stream to thereby provide a desulfurized natural gas stream, wherein said oxygen-containing natural gas stream combined with said reducing agent comprises said desulfurized natural gas stream. 
     
     
         14 . A process for removing oxygen from a natural gas stream, said process comprising:
 (a) introducing oxygen-containing natural gas and hydrogen into a deoxygenation zone, wherein said hydrogen is present in said deoxygenation zone in a non-stoichiometric amount relative to the amount of oxygen present in said deoxygenation zone; and   (b) removing at least a portion of the oxygen from the natural gas with at least one catalyst in said deoxygenation zone to thereby provide an oxygen-depleted natural gas stream, wherein the average temperature of said deoxygenation zone is less than about 480° F.   
     
     
         15 . The process of  claim 14 , wherein said hydrogen is present in a sub-stoichiometric amount relative to the amount of oxygen present in said deoxygenation zone. 
     
     
         16 . The process of  claim 14 , wherein said catalyst is a copper-containing catalyst. 
     
     
         17 . The process of  claim 16 , wherein the average temperature of said deoxygenation zone is at least 325° F. 
     
     
         18 . The process of  claim 14 , wherein said oxygen-depleted gas stream comprises less than about 25 ppmw of oxygen, based on the total weight of said oxygen-depleted gas stream. 
     
     
         19 . The process of  claim 14 , further comprising, measuring the hydrogen content and/or oxygen content of said oxygen-depleted gas stream and, based on the measured value of said hydrogen and/or oxygen content of said oxygen-depleted gas stream, adjusting the amount of hydrogen introduced into said deoxygenation zone and/or adjusting the average temperature of said deoxygenation zone. 
     
     
         20 . The process of  claim 14 , wherein said oxygen-depleted gas stream comprises less than 20 percent of the total amount of oxygen introduced into the deoxygenation zone. 
     
     
         21 . A method for controlling a process for removing oxygen from a gas stream, said method comprising:
 (a) combining an oxygen-containing feed gas stream with a hydrogen stream to thereby provide a combined feed gas stream; and   (b) passing at least a portion of said combined feed gas stream through a deoxygenation zone, wherein said passing comprises contacting said combined feed gas stream with at least one catalyst to remove at least a portion of the oxygen from said combined feed gas stream and provide an oxygen-depleted gas stream;   (c) measuring a value for at least one parameter of said oxygen-depleted gas stream;   (d) comparing the measured value for said parameter of said oxygen-depleted gas stream determined in step (c) with a target value for said parameter of said oxygen-depleted gas stream to determine a difference; and   (e) based on said difference, controlling at least one parameter of said combined gas stream in order to minimize said difference.   
     
     
         22 . The method of  claim 21 , wherein said parameter of said oxygen-depleted gas stream measured in step (c) is selected from the group consisting of the amount of oxygen in said oxygen-depleted gas stream, the amount of hydrogen in said oxygen-depleted gas stream, the pH of said oxygen-depleted gas stream, and combinations thereof. 
     
     
         23 . The method of  claim 21 , wherein said parameter of said combined gas stream controlled in step (e) is selected from the group consisting of the molar ratio of hydrogen to oxygen of said combined gas stream, the temperature of said combined gas stream, and both the molar ratio of hydrogen to oxygen and the temperature of said combined gas stream. 
     
     
         24 . The method of  claim 21 , wherein said measuring of step (c) includes determining a value for the oxygen content of said oxygen-depleted gas stream, and wherein step (d) comprises comparing the measured value for said oxygen content of said oxygen-depleted gas stream determined in step (c) with a target value for said oxygen content of said oxygen-depleted gas stream to determine said difference. 
     
     
         25 . The method of  claim 24 , wherein said target value is a maximum oxygen limit, wherein said oxygen content of said oxygen-depleted gas stream measured in step (c) is higher than said maximum oxygen limit, wherein said controlling of step (e) includes increasing the molar ratio of hydrogen to oxygen in said combined gas stream and/or increasing the temperature of said combined gas stream. 
     
     
         26 . The method of  claim 24 , wherein said target value is a minimum oxygen limit, wherein the oxygen content of said oxygen-depleted gas stream measured in step (c) is lower than said minimum oxygen limit, wherein said controlling of step (e) includes reducing the molar ratio of hydrogen to oxygen in said combined gas stream. 
     
     
         27 . The method of  claim 21 , wherein said measuring of step (c) includes determining a value for the hydrogen content of said oxygen-depleted gas stream and wherein said comparing of step (d) comprises comparing the value for said hydrogen content of said oxygen-depleted gas stream measured in step (c) with a target value for said hydrogen content of said oxygen-depleted gas stream to determine said difference. 
     
     
         28 . The method of  claim 21 , wherein said measuring of step (c) includes determining a value for the pH said oxygen-depleted gas stream and wherein said comparing of step (d) comprises comparing said value for said pH of said oxygen-depleted gas stream determined in step (c) with a target value for said pH of said oxygen-depleted gas stream to determine said difference. 
     
     
         29 . The method of  claim 21 , further comprising, repeating steps (a) through (e) until said difference has a value that is not more than about 10 percent of said target value. 
     
     
         30 . The method of  claim 21 , wherein at least a portion of steps (a) through (e) are carried out with an automated control system.