A study of copper oxide catalysts used in the methylchorosilane reaction and determination of the fate of oxygen

Abstract

The relative effectiveness of CuO and Cu2O were compared as catalysts for the methylchlorosilane (MCS) reaction. MCS reactions catalyzed by CuO had higher rates (0.15 g/g Si-h) than MCS reactions catalyzed by Cu2O (0.08) AND higher selectivities (4–5 points in % Di higherfor CuO). A synthetic method was found for making 17O-labeledCu2O based on reaction of CuCl with excess NaCl and >2equivalents of Na17OH. The Na17OH was made from17O-enriched water and Na. The % enrichment of theCu2O was determined by reduction of the Cu2O with H2 to form Cu and water and then subsequent reaction of the water product with Me2SiCl2 to make cyclo-octamethyltetrasiloxane (D4). The 17O enrichment of the D4 wasthen determined by mass spectroscopy. Thus Cu2O was made with27% 17O ±5%. The labeled Cu2Owas used as the catalyst in the MCS lab reactor. A 14% enrichmentin 17O in D4 and dichlorotetramethyldisiloxane(MClMCl) was found vs. the controlexperiment with natural abundance oxygen Cu2O. Thus all of the oxygen from the copper oxide catalyst ends up as siloxane; 50% of the oxygen in the product siloxane comes from other sources. Copper oxide catalyst was used in the presence of the phosphorus promoters Cu3P and PEt3. In both phosphorus promoter experiments, the resultant MCS lab beds were subjected toacetonitrile extraction and then NMR analysis of the extracts. Theseextracts showed that phosphorus-containing species were present and thatwhen Cu3P was the promoter, phosphorus products containing17O were present. Thus for Cu3P, some of thephosphorus reacts with the 17O from the Cu2O catalyst.