METHOD FOR TREATMENT OF A GAS STREAM CONTAINING SILICON TETRAFLUORIDE AND HYDROGEN CHLORIDE
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.