[1][2] The process involves copper-catalyzed reactions of alkyl halides with elemental silicon, which take place in a fluidized bed reactor.
Although theoretically possible with any alkyl halide, the best results in terms of selectivity and yield occur with chloromethane (CH3Cl).
[3] Few companies actually carry out the Rochow process, because of the complex technology and high capital requirements.
[4] The relevant reactions are (Me = CH3): Dimethyldichlorosilane (Me2SiCl2) is of particular value (precursor to silicones), but trimethylsilyl chloride (Me3SiCl) and methyltrichlorosilane (MeSiCl3) are also valuable.
It is proposed that close proximity of the Si-Cl to a copper-chloromethane "adduct" allows for formation of the Me-SiCl units.
Among the many promoter metals, zinc, tin, antimony, magnesium, calcium, bismuth, arsenic, and cadmium have been mentioned.
Although the boiling points of the various chloromethylsilanes are similar (Me2SiCl2: 70 °C, MeSiCl3: 66 °C, Me3SiCl: 57 °C, MeHSiCl2: 41 °C, Me2HSiCl: 35 °C), the distillation utilizes columns with high separating capacities, connected in series.