(55e) Direct Process for Methylchlorosilanes: Chemistry and Technology

Dow Performance Silicones (DPS) is the world leader in the direct process technology for the production of methylchlorosilanes (MCS, Me_xSiCl_y). MCS is the intermediate product to produce Poly Dimethyl Siloxanes (PDMS) that is the core base material to produce several thousand final silicone polymers. Silicones are synthetic polymers that combine the characteristics of plastics and glass with mixed properties of organic and inorganic polymers. MCS are produced via the Direct Process reaction of silicon metal with methyl chloride gas in the presence of copper catalysts and other metal promoters such as Sn, P, and Zn. Direct process is a unique solid-gas heterogeneous catalytic reaction that is more efficient with a bulk metal catalyst than a supported metal catalyst. The direct process catalysis involves generation of a consumable reactive site that repeats the cycle via regenerating the catalyst. This is unlike the active site regeneration in traditional heterogeneous catalytic processes. Reaction deactivates by the accumulation of impurity metals on the surface and methyl group decomposition that cause diffusion and kinetic hindrance as well as surface coking. This poster intends to highlight the key catalysis mechanism and technology aspects of this major commercial process and challenges and opportunities that exist in process improvement.