Method for treatment of a gas stream containing silicon tetrafluoride and hydrogen chloride

Abstract

The present invention is directed to a method for treatment of a gas stream comprising silicon tetrafluoride and hydrogen chloride. For example, the present invention is directed to a method for treatment of such a gas stream that involves contacting the gas stream with a metal that reacts with the hydrogen chloride to provide a treated gas stream having reduced hydrogen chloride content. The present invention is further directed to methods for subjecting silicon tetrafluoride and hydrogen chloride-containing gas streams to elevated pressure to provide gas streams suitable for transport.

1 . A process for removing hydrogen chloride from a gas stream comprising silicon tetrafluoride and having an initial hydrogen chloride content, the process comprising contacting the gas stream with a source of a metal, wherein the metal reacts with the hydrogen chloride, thereby preferentially removing hydrogen chloride from the gas stream and providing a treated gas stream comprising silicon tetrafluoride and having a reduced hydrogen chloride content that is no more than about 90% (v/v) of the initial hydrogen chloride content. 
     
     
         2 . A process as set forth in  claim 1  wherein the gas stream has a moisture content of at least about 100 ppm. 
     
     
         3 . A process as set forth in  claim 1  wherein the gas stream has a moisture content of from about 100 ppm to about 2500 ppm. 
     
     
         4 . A process as set forth in  claim 1  wherein the metal exhibits a removal efficiency that is at least about 95%. 
     
     
         5 . A process as set forth in  claim 1  wherein the reduced hydrogen chloride content is no more than about 10% (v/v) of the initial hydrogen chloride content. 
     
     
         6 . A process as set forth in  claim 1  wherein the reduced hydrogen chloride content is achieved within about 2 minutes of beginning said contacting. 
     
     
         7 . A process as set forth in  claim 1  wherein no more than about 10% (v/v) of the silicon tetrafluoride is removed from the gas stream during said contacting. 
     
     
         8 . A process as set forth in  claim 1  wherein the metal source comprises a metal oxide, metal hydroxide, or a combination thereof. 
     
     
         9 . A process as set forth in  claim 1  wherein the metal exhibits an electronegativity of less than about 1.65. 
     
     
         10 . A process as set forth in  claim 1  wherein the source of metal is a metal oxide or a metal hydroxide of a metal of Groups 2-4 or 12-14 of the Periodic Table of the Elements. 
     
     
         11 . A process as set forth in  claim 1  wherein said contacting is conducted at a temperature of from about 25° C. to about 90° C. 
     
     
         12 . A process as set forth in  claim 1  wherein said contacting is conducted at a pressure of from about 50 psig to about 1500 psig. 
     
     
         13 . A process as set forth in  claim 1  wherein the surface area of the metal source is at least about 80 ft 2 /ft 3 . 
     
     
         14 . A process as set forth in  claim 13  wherein the surface area of the metal source is from about 80 ft 2 /ft 3  to about 600 ft 2 /ft 3 . 
     
     
         15 . A process as set forth in  claim 1  wherein the gas stream is contacted with the metal at a rate of at least about 0.05 lb/hr·ft 2 . 
     
     
         16 . A process as set forth in  claim 1  wherein at least a portion of the metal source is in the form of particles ranging in size of from about 500 μm to about 5000 μm. 
     
     
         17 . A process as set forth in  claim 1  wherein the metal source exhibits a porosity of from about 30% to about 80%. 
     
     
         18 . A process as set forth in  claim 1  wherein the gas stream is contacted with a bed comprising the metal source. 
     
     
         19 . A process as set forth in  claim 18  wherein the pressure drop across the bed is from about 1 psig to about 25 psig. 
     
     
         20 . A process as set forth in  claim 18  wherein the gas stream passes over the bed of metal source at a space velocity of at least about 0.1 ft/minute. 
     
     
         21 . A process as set forth in  claim 18  wherein the bed is in the form of a packed bed, fluidized bed, or moving bed. 
     
     
         22 . A process as set forth in  claim 1  wherein the metal exhibits a removal efficiency that is at least about 90%. 
     
     
         23 . A process as set forth in  claim 1  wherein the metal exhibits a removal efficiency that is at least about 98%. 
     
     
         24 . A process as set forth in  claim 1  wherein the gas stream has a moisture content of from about 300 ppm to about 800 ppm. 
     
     
         25 . A process as set forth in  claim 1  wherein the reduced hydrogen chloride content is no more than about 5% (v/v) of the initial hydrogen chloride content. 
     
     
         26 . A process as set forth in  claim 1  wherein the reduced hydrogen chloride content is no more than about 0.5% (v/v) of the initial hydrogen chloride content. 
     
     
         27 . A process as set forth in  claim 1  wherein no more than about 0.5% (v/v) of the silicon tetrafluoride is removed from the gas stream during said contacting. 
     
     
         28 . A process as set forth in  claim 1  wherein said contacting is conducted at a temperature of from about 45° C. to about 70° C. 
     
     
         29 . A process as set forth in  claim 1  wherein the surface area of the metal source is at least about 200 ft 2 /ft 3 . 
     
     
         30 . A process as set forth in  claim 1  wherein the surface area of the metal source is from about 200 ft 2 /ft 3  to about 400 ft 2 /ft 3 . 
     
     
         31 . A process as set forth in  claim 1  wherein at least a portion of the metal source is in the form of particles ranging in size of from about 1000 μm to about 4000 μm. 
     
     
         32 . A process as set forth in  claim 1  wherein the metal source exhibits a porosity of from about 40% to about 70%. 
     
     
         33 . A process for removing hydrogen chloride from a gas stream comprising silicon tetrafluoride and having an initial pressure and initial hydrogen chloride content, the process comprising:
 compressing the gas stream during one or more stages of increasing pressure greater than said initial pressure; and   contacting the gas stream with a source of a metal, thereby providing a treated gas stream having a reduced hydrogen chloride content that is no more than about 90% (v/v) of the initial hydrogen chloride content.   
     
     
         34 . A process as set forth in  claim 33  wherein said compressing comprises subjecting the gas stream to a first stage of increasing pressure of at least about 100 psig. 
     
     
         35 . A process as set forth in  claim 33  wherein said compressing comprises subjecting the gas stream to a first stage of increasing pressure of from about 100 psig to about 700 psig. 
     
     
         36 . A process as set forth in  claim 34  wherein, prior to said first stage, the gas stream has a moisture content of at least about 100 ppm. 
     
     
         37 . A process as set forth in  claim 34  wherein, prior to said first stage, the gas stream has a moisture content of from about 100 ppm to about 2500 ppm. 
     
     
         38 . A process as set forth in  claim 34  wherein said compressing comprises subjecting the gas stream to a second stage of increasing pressure of at least about 800 psig. 
     
     
         39 . A process as set forth in  claim 38  wherein, prior to said second stage, the gas stream has a moisture content of at least about 100 ppm. 
     
     
         40 . A process as set forth in  claim 38  wherein, prior to said second stage, the gas stream has a moisture content of from about 100 ppm to about 2500 ppm. 
     
     
         41 . A process as set forth in  claim 38  wherein said contacting occurs between said first stage and said second stage. 
     
     
         42 . A process as set forth in  claim 34  wherein said compressing comprises subjecting the gas stream to a second stage of increasing pressure of from about 1000 psig to about 1800 psig. 
     
     
         43 . A process as set forth in  claim 34  wherein said contacting occurs prior to said first stage. 
     
     
         44 . A process as set forth in  claim 33  wherein during said contacting the metal reacts with the hydrogen chloride, thereby providing a treated gas stream comprising silicon tetrafluoride and having a reduced hydrogen chloride content. 
     
     
         45 . A process as set forth in  claim 44  wherein the reduced hydrogen chloride content is no more than about 70% (v/v) of the initial hydrogen chloride content. 
     
     
         46 . A process as set forth in  claim 44  wherein the reduced hydrogen chloride content is achieved within about 2 minutes of beginning said contacting. 
     
     
         47 . A process as set forth in  claim 33  wherein no more than about 1% (v/v) of the silicon tetrafluoride is removed from the gas stream during said contacting. 
     
     
         48 . A process as set forth in  claim 33  wherein the source of metal is a metal oxide or a metal hydroxide of a metal of Groups 2-4 or 12-14 of the Periodic Table of the Elements. 
     
     
         49 . A process as set forth in  claim 33  wherein said contacting is conducted at a temperature of from about 25° C. to about 90° C. 
     
     
         50 . A process as set forth in  claim 33  wherein said contacting is conducted at a pressure of from about 50 psig to about 1500 psig. 
     
     
         51 . A process as set forth in  claim 33  wherein said compressing comprises subjecting the gas stream to a first stage of increasing pressure of at least about 200 psig. 
     
     
         52 . A process as set forth in  claim 33  wherein, prior to said first stage, the gas stream has a moisture content of at least about 800 ppm. 
     
     
         53 . A process as set forth in  claim 33  wherein said compressing comprises subjecting the gas stream to a second stage of increasing pressure of at least about 1000 psig. 
     
     
         54 . A process as set forth in  claim 53  wherein, prior to said second stage, the gas stream has a moisture content of from about 300 ppm to about 1700 ppm. 
     
     
         55 . A process as set forth in  claim 33  wherein the metal exhibits a removal efficiency that is at least about 95%. 
     
     
         56 . A process as set forth in  claim 33  wherein the reduced hydrogen chloride content is no more than about 5% (v/v) of the initial hydrogen chloride content. 
     
     
         57 . A process as set forth in  claim 33  wherein no more than about 10% (v/v) of the silicon tetrafluoride is removed from the gas stream during said contacting. 
     
     
         58 . A process as set forth in  claim 33  wherein the surface area of the metal source is from about 200 ft 2 /ft 3  to about 400 ft 2 /ft 3 . 
     
     
         59 . A process as set forth in  claim 33  wherein at least a portion of the metal source is in the form of particles ranging in size of from about 1000 μm to about 4000 μm. 
     
     
         60 . A process as set forth in  claim 33  wherein the metal source exhibits a porosity of from about 40% to about 70%. 
     
     
         61 . A process as set forth in  claim 33  wherein the gas stream is contacted with a bed comprising the metal source at a space velocity at least about 4 ft/minute.