Synthesis of organohalosilane monomers from conventionally uncleavable Direct Process Residue
Disclosed herein is a catalytic process for the synthesis of organohalosilane monomers from tetraorganodihalodisilanes and other compounds that are not cleaved during the conventional hydrochlorination of Direct Process Residue. The process is characterized by the use of a catalyst containing (1) one or more heterocyclic amines and/or one or more heterocyclic ammonium halides, and (2) one or more quaternary Group 15 onium compounds.
1. A catalytic process for producing an organohalosilane monomer composition from a high-boiling residue, said process comprising
(A) heating the high-boiling residue in the presence of a catalyst comprising (1) one or more heterocyclic amines and/or one or more heterocyclic ammonium halides, and (2) one or more quaternary Group 15 onium compounds,
optionally in the presence of an organohalide and/or a hydrogen halide and/or an inert gas,
at a temperature within the range of about 75° C. to about 300° C. under atmospheric pressure or superatmospheric pressure
to convert the high-boiling residue to an organohalosilane monomer composition containing at least one organohalosilane monomer having a general formula selected from the group consisting of R 1 SiHX 2 , R 1 2 SiHX, R 1 2 SiX 2 and R 1 3 SiX, R 1 being an aromatic, aliphatic, alkaryl or cycloaliphatic univalent hydrocarbyl group, X being a halogen atom selected from the group consisting of fluorine, chlorine, bromine, and iodine, and
(B) optionally recovering the catalyst,
wherein the high-boiling residue comprises (1) an uncleavable component containing at least one of tetraorganodihalodisilanes and optionally one or more compounds selected from carbosilanes, organohalopolysilanes, hexaorganodisilanes, and pentaorganohalodisilanes; and (2) optionally a cleavable component containing at least one of diorganotetrahalodisilanes and triorganotrihalodisilanes with the proviso that if present, the cleavable component has a concentration less than that of the uncleavable component; and
wherein the quaternary Group 15 onium compound is of the general formula, R 4 Q + X − , wherein each R is independently an alkyl, cycloalkyl, aryl or alkaryl group of from 1 to 30 carbon atoms, Q is phosphorus, arsenic, antimony and bismuth, and X is a halide selected from the group consisting of F, Cl, Br or I.
2. The process of claim 1 wherein the heterocyclic amine has at least one nitrogen atom in at least one 4- to 8-membered hydrocarbon ring, wherein the ring atoms adjacent to the nitrogen are carbon or nitrogen, and the hydrocarbon ring or rings are, independently of one another, aromatic or non-aromatic hydrocarbon rings.
3. The process of claim 2 wherein the heterocyclic amine has a pKa of about 6.9 to about 7.9.
4. The process of claim 2 wherein the heterocyclic amine contains a five-membered ring with 1 to 3 nitrogen atoms.
5. The process of claim 4 wherein the heterocyclic amine is selected from the group consisting of imidazole, 1-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropyl-imidazole, 4-methylimidazole, 2,4-dimethylimidazole, 2-(2-imidazolyl)imidazole, 2-phenylimidazole, imidazoline, imidazolidine, pyrazole, 3-methylpyrazole, pyrrolidone, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidone, 1,2,3-triazole, and 1,2,4-triazole.
6. The process of claim 1 wherein the heterocyclic ammonium halide is derived from a heterocyclic amine having at least one nitrogen atom in at least one 4- to 8-membered hydrocarbon ring, wherein the ring atoms adjacent to the nitrogen are independently carbon or nitrogen atoms, and the hydrocarbon ring or rings are, independently of one another, aromatic or non-aromatic hydrocarbon rings, wherein the halide is fluoride, chloride, bromide or iodide.
7. The process of claim 6 wherein the heterocyclic ammonium halide is derived from a heterocyclic amine with 1 to 3 nitrogen atoms in a five-membered ring, and the halide is fluoride, chloride, bromide or iodide.
8. The process of claim 7 wherein the heterocyclic ammonium halide is 1,2-dimethyl-3-(n-propyl)-imidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1,2-dimethyl-3-(n-butyl)imidazolium chloride, 1-butyl-3-methyl-imidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, or 1-methylimidazolium chloride.
9. The process of claim 6 wherein the heterocyclic ammonium halide is an ionic liquid selected from the group consisting of 1-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-(3-cyanopropyl)-3-methylimidazolium chloride.
10. The process of claim 1 wherein the quaternary Group 15 onium compound, R 4 Q + X − , contains compounds of general formulae R 3 QHX and HX, wherein R is an alkyl, cycloalkyl, aryl or alkaryl group of from 1 to 30 carbon atoms, Q is phosphorus, antimony or arsenic, and X is F, Cl, Br or I.
11. The process of claim 1 wherein the quaternary Group 15 onium compound, R 4 Q + X − , is tetra(n-butyl)phosphonium chloride, tetra(n-butyl)phosphonium bromide, trihexyl(tetradecyl)phosphonium bromide, methyltri(isobutyl)phosphonium bromide, methyltri(isobutyl)phosphonium chloride, tetra(n-octyl)phosphonium chloride, tri(n-butyl)tetradecylphosphonium chloride, or octyltri(butyl)phosphonium chloride.
12. The process of claim 11 wherein the quaternary Group 15 onium compound is an ionic liquid selected from the group consisting of tri(n-hexyl)tetradecylphosphonium chloride, tetra(n-butyl)phosphonium bromide, tetra(n-butyl)phosphonium chloride, tri(n-butyl)tetradecylphosphonium chloride, and methyltri(isobutyl)phosphonium chloride.
13. The process of claim 1 wherein the step (A) is conducted in the presence of an organohalide being methyl chloride or methyl bromide.
14. The process of claim 1 wherein the step (A) is conducted in the presence of a hydrogen halide being HCl or HBr.
15. The process of claim 1 wherein the step (A) is conducted in the presence of an inert gas being nitrogen or argon.
16. The process of claim 1 wherein R 1 is methyl, ethyl or phenyl and X is chloride or bromide.
17. The process of claim 1 wherein the organohalosilane monomer composition comprises (CH 3 ) 2 SiHCl, CH 3 SiHCl 2 , (CH 3 ) 3 SiCl, (CH 3 ) 2 SiCl 2 , and CH 3 SiCl 3 , wherein the content of (CH 3 ) 2 SiCl 2 and CH 3 SiHCl 2 , individually or collectively, exceeds that of CH 3 SiCl 3 .
18. The process of claim 1 wherein the high-boiling residue is heated under a superatmospheric pressure of up to 7 MPa at 150° C. to 250° C. in a mechanically stirred reactor for a period of 30 to 120 minutes.
19. The process of claim 1 wherein the high-boiling residue is heated under ambient atmospheric pressure at 150° C. to 250° C.
20. The process of claim 1 wherein the catalyst contains 0.01 wt % to 99.95 wt % of (1) at least one or more heterocyclic amines and/or one or more heterocyclic ammonium halides, and 0.05 wt % to 99.9 wt % of (2) one or more quaternary Group 15 onium compound based on the total weight of components (1) and (2).
21. The process of claim 20 wherein the catalyst contains 5 wt % to 85 wt % of 2-methylimidazole and 95 wt % to 15 wt % of tetra(n-butyl)-phosphonium chloride based on the total weight of the 2-methylimidazole and the tetra(n-butyl)-phosphonium chloride.
22. The process of claim 21 wherein the molar ratio of 2-methylmidazole to tetra(n-butyl)phosphonium chloride is from 1.1 to 100.
23. The process of claim 21 wherein the 2-methylimidazole contains about 0.05 to about 5 weight percent of imidazole and the tetra(n-butyl)phosphonium chloride contains about 0.05 to about 5 weight percent of HCl and about 0.05 to about 5 weight percent of (n-C 4 H 9 ) 3 PHCl.
24. The process of claim 1 wherein the weight of the catalyst is 1 to 50 percent of the weight of the high-boiling residue.
25. The process of claim 1 wherein the catalyst is recovered and reused.
26. The process of claim 1 wherein multiple batches of the high-boiling residue are converted to the organohalosilane monomer composition on a single catalyst charge and the ultimate catalyst usage, defined as 100×(weight of the catalyst/total weight of the high-boiling residue), is about 0.1 to about 5 weight percent.
27. The process of claim 1 wherein the catalytic process comprises reactions selected from the group consisting of disproportionation, redistribution, silylene extrusion, silylene insertion and the combinations thereof.
28. The process of claim 27 wherein the reactions are conducted batchwise or continuously in ionic liquids in a mechanically-stirred reactor, a gas-sparged reactor or a bubble column.