Production of organosilanes from polysilanes

Abstract

The present invention is a process for the production of organosilanes from the high-boiling residue resulting from the reaction of organohalides with silicon metalloid in a process typically referred to as the "direct process." The present process comprises forming a mixture comprising a organotrihalosilane and the high-boiling residue in the presence of hydrogen gas, a hydrogenolysis catalyst, and a redistribution catalyst. The organotrihalosilane and high-boiling residue are converted into commercially useful di- and triorganosilanes and organohydrosilanes. The present process results in consumption of the organotrihalosilane rather than the net increase which typically occurs in the absence of the redistribution catalyst.

We claim: 
     
       1. A process for converting .Iadd.a high-boiling residue comprising .Iaddend.polysilanes to organosilanes, the process comprising: (A) forming a mixture comprising .Iadd.a high-boiling residue comprising .Iaddend.polysilanes of formula   R.sub.a H.sub.b Si.sub.n X.sub.2n+2-a-b        and an organotrihalosilane of formula   RSiX.sub.3       (B) contacting the mixture with hydrogen gas at a pressure of 50 psig to 10,000 psig, a hydrogenolysis catalyst, and a redistribution catalyst, at a temperature of 100° C. to 400° C. and   (C) recovering organohalosilanes of formula   R.sub.c H.sub.d SiX.sub.4-c-d        where each R is a radical independently selected from a group consisting of alkyls of one to six carbon atoms, aryls, alkoxys of one to six carbon atoms, trimethylsilyl, and trifluoropropyl, X is a halogen, n=2 to 20, a=0 to 2n+2, b=0 to 2n+2, a+b=0 to 2n+2, c=1, 2, 3, or 4, d=0, 1, or 2, and c+d=2, 3, or 4.   
     
     
       2. A process according to claim 1, where n is two. 
     
     
       3. A process according to claim 1, where a=(2n+2)/2 to 2n+2. 
     
     
       4. A process according to claim 1, where R is methyl. 
     
     
       5. A process according to claim 1, where X is chlorine. 
     
     
       6. A process according to claim 1, where the polysilanes are disilanes. 
     
     
       7. A process according to claim 1, where the organotrihalosilane is methyltrichlorosilane. 
     
     
       8. A Process according to claim 1, where the organotrihalosilane is about 30 to 50 weight percent of the mixture. 
     
     
       9. A process according to claim 1, where the hydrogen gas is at a pressure of about 1000 psig to 1500 psig. 
     
     
       10. A process according to claim 1, where the hydrogenolysis catalyst is selected from a group consisting of organometallic nickel compounds, complexed nickel salts, organometallic palladium compounds, complexed palladium salts, organometallic platinum compounds, and complexed platinum salts. 
     
     
       11. A process according to claim 1, where the hydrogenolysis catalyst is selected from a group consisting of complexed nickel and complexed palladium salts consisting of the complex addition compound formed between two moles of a trialkyl, triaryl, dialkylaryl, or an alkyldiarylphosphine. 
     
     
       12. A process according to claim 1, where the hydrogenolysis catalyst is bis(tributylphosphine)nickel(II)dichloride. 
     
     
       13. A process according to claim 1, where the hydrogenolysis catalysis is selected from a group consisting of nickel, inorganic nickel compounds, palladium, inorganic palladium compounds, platinum, and inorganic platinum compounds. 
     
     
       14. A process according to claim 1, where the hydrogenolysis catalyst is selected from a group consisting of supported nickel, supported palladium, and supported platinum. 
     
     
       15. A process according to claim 14, where the support is selected from a group consisting of silica, carbon, alumina, and diatomaceous earth. 
     
     
       16. A process according to claim 15, where the hydrogenolysis catalyst is nickel supported on kieselguhr. 
     
     
       17. A process according to claim 1, where the hydrogenolysis catalyst is present at a concentration within a range of about 1.0 to 10.0 weight percent of the combined weight of the high-boiling residue, organotrihalosilane, and catalysts. 
     
     
       18. A process according to claim 1, where the redistribution catalyst is selected from a group consisting of quaternary phosphonium halides, quaternary ammonium halides, aluminum halides, and boron halides. 
     
     
       19. A process according to claim 1, where the redistribution catalyst is selected from a group consisting of alumina, aluminosilicates, acid-exchange zeolites, acid activated clays, and quaternized ion exchange resins containing quaternary ammonium halides or phosphonium halides. 
     
     
       20. A process according to claim 19, where the redistribution catalyst is alumina. 
     
     
       21. A process according to claim 1, where the redistribution catalyst is present within a range of about 1.0 to 10.0 weight percent of the combined weights of the high-boiling residue, organotrihalosilane, and catalysts. 
     
     
       22. A process according to claim 1, where the hydrogenolysis catalyst and the redistribution catalyst are added to the process as a single heterogeneous catalyst where one catalyst serves as a support for the other. 
     
     
       23. A process according to claim 22, where palladium metal is supported on alumina. 
     
     
       24. A process according to claim 1, where the temperature is within a range of about 300° C. to 350° C. 
     
     
       25. A process according to claim 1, where the organosilane is selected from a group consisting of dimethyldichlorosilane and methyldichlorosilane. 
     
     
       26. A process according to claim 1, where the polysilane is dimethyltetrachlorodisilane. 
     
     
       27. A process according to claim 1, where R is methyl, n=2, X is chlorine, the hydrogen gas pressure is at a pressure of about .[.1000.]. .Iadd.500 .Iaddend.psig to .[.1500.]. .Iadd.2000 .Iaddend.psig the temperature is within a range of about 300° C. to 350° C., the hydrogenolysis catalyst is selected from a group consisting of bis(tributylphosphine)nickel(II)dichloride, palladium supported on carbon, and nickel supported on kieselguhr, and the redistribution catalyst is alumina. .Iadd.28. A process according to claim 1, where the hydrogen gas is at a pressure of about 500 psig to 2000 psig and the temperature is within a range of about 300° C. to 350° C. .Iaddend. .Iadd.29. A process according to claim 1, where the high-boiling residue further comprises disilmethylenes. .Iaddend. .Iadd.30. A process for converting polysilanes to organosilanes, the process comprising: (A) forming a mixture comprising polysilanes of formula   R.sub.a H.sub.b Si.sub.n X.sub.2n+2-a-b        and an organotrihalosilane of formula   RSiX.sub.3       (B) contacting the mixture with hydrogen gas at a pressure of 50 psig to 10,000 psig, a hydrogenolysis catalyst, and a redistribution catalyst, at a temperature of 100° C. to 400° C.,    and   (C) recovering organohalosilanes of formula   R.sub.c H.sub.d SiX.sub.4-c-d        where each R is a radical independently selected from a group consisting of alkyls of one to six carbon atoms, aryls, alkoxys of one to six carbon atoms, trimethylsilyl,    and trifluoropropyl, X is a halogen, n=2 to 20, a=0 to 2n+2, b=0 to 2n+2, a+b=0 to 2n+2, c=1, 2, 3, or 4, d=0, 1, or 2, and c+d=2, 3, or 4. .Iaddend.