Process and apparatus for preparation of octachlorotrisilane
View Patent ↗The invention relates to a process and an apparatus for controlled preparation of octachlorotrisilane from monomeric chlorosilanes, by subjecting the chlorosilanes to a thermal plasma.
1. A process for preparing octachlorotrisilane, the process comprising
subjecting chlorosilanes comprising at least one monomeric chlorosilane of formula I in the absence of hydrogen to a thermal plasma:
H x SiCl 4−x (I),
where x is independently selected from 0, 1, 2 and 3.
2. The process according to claim 1 , further comprising
obtaining a mixture of octachlorotrisilane and hexachlorodisilane.
3. The process according to claim 1 , further comprising
isolating ultrahigh-purity octachlorotrisilane.
4. The process according to claim 1 , further comprising
obtaining octachlorotrisilane having a titanium content of less than 1 ppm by weight.
5. The process according to claim 1 , wherein the the chlorosilanes are one or more of an ultrahigh-purity tetrachlorosilane, an ultrahigh-purity trichlorosilane, and an ultrahigh-purity dichlorosilane.
6. The process according to claim 1 , wherein the process is performed in an apparatus comprising a gas discharge reactor, a first column, and a second column.
7. The process according to claim 6 , wherein
the first column is provided with a column inlet for removal of octachlorotrisilane upstream of the gas discharge reactor and the second column is provided with a column inlet for removal of low boilers downstream of the gas discharge reactor and a column outlet,
the column outlet of the second colunm has a dedicated gas divider, and
the gas divider has a dedicated recycle line which supplies the low boilers to the first column or to the gas discharge reactor as a return stream.
8. The process according to claim 7 , wherein the gas divider has a shut-off, a valve, or other regulating unit.
9. The process according to claim 7 , wherein the chlorosilane of the formula I is introduced into the gas discharge reactor or supplied to the first column in a mixture with hexachlorodisilane.
10. The process according to claim 9 , wherein
unconverted mixture of the chlorosilanes of the formula I and hexachlorodisilane leaving the gas discharge reactor via the second column are divided in the apparatus at the gas divider,
a portion of the mixture is recycled as a return stream via the recyle line into the first column and conducted again through the gas discharge reactor, and
high-purity or ultrahigh-purity octachlorotrisilane is obtained at the column outlet of the first column.
11. The process according to claim 10 , wherein a molar ratio of trichlorosilane to tetrachlorosilane in the return stream is from 0.1:20 to 2:20.
12. The process according to claim 6 , wherein a pressure of 300 to 800 mbar abs exists in the gas discharge reactor.