Nanosized copper catalyst precursors for the direct synthesis of trialkoxysilanes
View Patent ↗The present invention provides a process for using nanosized copper, nanosized copper oxides, nanosized copper chlorides, other nanosized copper salts, and mixtures thereof, as sources of catalytic copper in the Direct Synthesis of trialkoxysilanes of the formula HSi(OR) 3 wherein R is an alkyl group containing from 1 to 6 carbon atoms inclusive. The nanosized copper, nanosized copper oxides, nanosized copper chlorides, other nanosized copper salts, and their mixtures of this invention have average particle sizes that are in the range from about 0.1 to about 60 nanometers, preferably from about 0.1 to about 30 nanometers, and most preferably from about 0.1 to about 15 nanometers. Nanosized sources of catalytic copper afford high dispersion of catalytic sites on silicon and contribute to high reaction rates, high selectivity and high silicon conversion. The nanosized copper catalyst precursors of the invention permit the use of substantially reduced levels of copper compared to conventional practice.
1. A method of controlling direct synthesis of trialkoxysilanes comprising the steps of:
providing a silicon metal;
providing a thermally stable solvent;
providing one or more copper catalyst precursors having an average particle size of from about 0.1 to about 60 nm;
heating said silicon metal and said one or more copper catalyst precursors in said thermally stable solvent;
forming copper-silicon intermetallics for reaction with an alcohol; and
maintaining an effective copper concentration during a steady state of the Direct Synthesis wherein selectivity for trialkoxysilane is greater than about 10.
2. The method of claim 1 wherein said thermally stable solvent is a member selected from the group consisting of linear and branched paraffins, cycloparaffins, alkylated benzenes, aromatic ethers, and polyaromatic hydrocarbons.
3. The method of claim 1 wherein said copper catalyst precursor is selected from the group consisting of nanosized copper, nanosized copper oxides, nanosized copper chlorides, other nanosized copper salts, and mixtures thereof.
4. The method of claim 1 wherein the trialkoxysilane has the formula HSi(OR) 3 wherein R is an alkyl group containing from 1 to 6 carbon atoms inclusive.
5. The method of claim 1 wherein the alcohol is methanol and/or ethanol.
6. The method of claim 5 wherein the alcohol is fed into the thermally stable solvent as a gas.
7. The method of claim 1 wherein the step of heating the silicon metal and one or more copper catalyst precursors is performed at a temperature of from about 20° C. to about 400° C.
8. The method of claim 1 wherein the step of heating the silicon metal and one or more copper catalyst precursors is performed at a temperature of from about 150° C. to about 300° C.
9. The method of claim 1 wherein the thermally stable solvent includes a foam control agent.
10. The method of claim 1 wherein the effective copper concentration ranges from about 0.008 to about 4.5 parts weight % of copper per 100 parts by weight silicon.
11. The method of claim 1 wherein the effective copper concentration ranges from about 0.03 to about 1.8 parts by weight % of copper per 100 parts silicon.
12. The method of claim 1 wherein the effective copper concentration ranges from about 0.05 to about 0.9 parts by weight % of copper per 100 parts silicon.