Direct reaction between silicon and methanol over the Cu2O, CuO, and metallic Cu0 catalystsa.
| Catalysts | Cu0 (111) crystallite sizesb (nm) | Reaction temperatures (°C) | Methanol conversions (%) | Tetramethoxysilane selectivities (%) | Methyl formate selectivities (%) | Trimethoxysilane selectivities (%) | Activitiesc (molmethanol molCu−1 h−1) |
|---|---|---|---|---|---|---|---|
| Cu2O | 27.1 | 220 | 64.4 | 100 | 0 | — | 3.4 |
| 240 | 93.8 | 98.2 | 1.8 | — | 5.0 | ||
| 260 | 97.0 | 90.9 | 9.1 | — | 5.2 | ||
| CuO | 31.7 | 220 | 55.0 | 99.2 | 0.8 | — | 3.3 |
| 240 | 70.3 | 92.3 | 7.7 | — | 4.2 | ||
| Bulk Cu0 | 150 μm | 220 | 11.1 | 96.9 | — | 3.1 | 0.3 |
| 240 | 45.2 | 90.8 | — | 9.2 | 1.3 | ||
| 260 | 54.2 | 87.9 | — | 12.1 | 1.6 |
a
The reaction mixtures of silicon and copper-based catalyst were pretreated at 240 °C for 2 h in a N2 stream with a flow rate of 20 mL min−1. The reaction conditions: the amount of catalyst/Si was 40 g; weight ratios of Cu2O, CuO, and bulk Cu0 to silicon were 5 : 100, 5 : 100, and 8 : 100, respectively; methanol flow rate was 6 mL h−1.
b
Cu0 (111) crystallite sizes were calculated according to the Scherrer equation. The size for bulk Cu powder was the average particle size.
c
The catalytic activities were based on metallic copper amount in the catalysts.