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Tetrafluorosilane Process Improvement

IP.com Disclosure Number: IPCOM000239382D
Publication Date: 2014-Nov-04
Document File: 1 page(s) / 30K

Publishing Venue

The IP.com Prior Art Database

Abstract

Tetrafluorosilane (SiF4) production requires the removal of CO2 impurity. Standard practice is to use 4A (Na-LTA) zeolite; however, SiF4 slowly, but irreversibly reacts with 4A reducing its CO2 capacity with use. A different adsorbent, AW-500 (mined chabazite manufactured by UOP), has been found to be more resistant to reaction with SiF4 and remains an effective removal agent for CO2 for a much longer time versus 4A which reduces costs and improves uptime for the SiF4 process.

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Title: Tetrafluorosilane Process Improvement

Abstract:

Tetrafluorosilane (SiF4) production requires the removal of CO2 impurity. Standard practice is to use 4A (Na-LTA) zeolite; however, SiF4 slowly, but irreversibly reacts with 4A reducing its CO2 capacity with use. A different adsorbent, AW-500 (mined chabazite manufactured by UOP), has been found to be more resistant to reaction with SiF4 and remains an effective removal agent for CO2 for a much longer time versus 4A which reduces costs and improves uptime for the SiF4 process.

Disclosure:

Tetrafluorosilane (SiF4) is an important raw material in the electronics industry, finding use in the production of optical fibers, semiconductors, and solar cells. One route to the manufacture of SiF4 involves the thermolysis of sodium hexafluorosilicate (Na2SiF6):

Na2SiF6 = SiF4 + 2NaF.

Production of SiF4 by this route requires further purification to remove traces of CO2, which likely arises from impurities in the Na2SiF6, from the final product. Removal of CO2 has been done by passing crude SiF4 product through an adsorption column containing NaA (type 4A) zeolite, which selectively adsorbs CO2 from the SiF4 product stream. The adsorption column is periodically regenerated by increasing temperature and passing a clean purge gas through the column. A problem with this method is that the SiF4 product reacts slowly but irreversibly with the NaA zeolite, which causes a loss in effective capacity for adsorption of CO2 result...