Processes and systems for purifying silane
View Patent ↗Processes and systems for purifying silane-containing streams and, in particular, for purifying silane-containing streams that also contain ethylene are disclosed. The processes and systems may be arranged such that one or more ethylene reactors are downstream of light-end distillation operations.
1. A process for purifying a silane-containing stream, the stream comprising silane, ethylene and one or more compounds having a boiling point less than silane, the process comprising:
introducing the silane-containing stream into a reactor to convert ethylene to at least one of ethylsilane and ethane and to produce an ethylene-depleted stream relative to the silane-containing stream; and
introducing the ethylene-depleted stream into a light-ends distillation column to produce a silane-depleted overhead fraction and a silane-enriched bottoms fraction relative to the ethylene-depleted stream, the silane-enriched bottoms fraction comprising silane and at least one of ethylsilane and ethane.
2. The process as set forth in claim 1 wherein the silane-enriched bottoms fraction produced from the light-ends distillation column is introduced into a heavy-ends distillation column to produce a silane-enriched overhead fraction and a silane-depleted bottoms fraction relative to the silane-enriched bottoms fraction produced from the light-ends distillation column, the silane-depleted bottoms fraction being enriched in at least one of ethylsilane and ethane.
3. The process as set forth in claim 2 wherein the silane-containing stream comprises compounds having a boiling point greater than silane other than ethylsilane and ethane, wherein the silane-depleted bottoms fraction produced from the heavy-ends distillation column is enriched in such compounds.
4. The process as set forth in claim 3 wherein the one or more compounds having a boiling point greater than silane are selected from the group consisting of diethyl silane, toluene, dimethoxyethane and mixtures thereof.
5. The process as set forth in claim 1 wherein the silane-containing stream is heated to a temperature of at least about 25° C. prior to entry into the reactor.
6. The process as set forth in claim 1 wherein the silane-containing stream is pressurized to a pressure of at least about 2000 kPa prior to introduction into the reactor.
7. The process as set forth in claim 1 wherein the silane-containing stream is contacted with a zeolite catalyst in the reactor.
8. The process as set forth in claim 7 wherein the zeolite catalyst is in the form of a molecular sieve.
9. The process as set forth in claim 1 wherein the reactor comprises a zeolite-supported platinum, palladium or nickel catalyst.
10. The process as set forth in claim 1 wherein the ethylene-depleted stream is cooled to a temperature less than about 35° C. before introduction into the light-ends distillation column.
11. The process as set forth in claim 1 wherein the one or more compounds having a boiling point less than silane are selected from the group consisting of hydrogen, nitrogen, and methane.
12. The process as set forth in claim 1 wherein there is a unit operation directly upstream of the reactor and the difference in temperature between the stream discharged from the upstream unit operation and the silane-containing stream introduced into the reactor is less than about 125° C.
13. The process as set forth in claim 1 wherein the difference in temperature between the stream discharged from the reactor and the ethylene-depleted stream introduced into the light-ends distillation column is less than about 300° C.
14. The process as set forth in claim 1 wherein at least about 75% of the ethylene introduced into the reactor in the silane-containing stream is converted to at least one of ethylsilane and ethane.