Catalytic cracking of CH₃Cl on copper-based phases

Abstract

The methylchlorosilanes synthesis from Si and CH3Cl, also called the direct synthesis suffers from a side-reaction during which the CH3Cl reactant cracks and forms carbonaceous compounds, called coke. It leads...

Toward Understanding the Formation of Coke during the MCS Reaction: A Theoretical Approach

“…Experiments show that metallic copper catalyzes the cracking reaction . While it is shown that Cu can be converted to CuCl when reacting with CH 3 Cl at lab-scale, it is also known that stable Cu 0 is formed during the reaction. , From their results, Blaser et al. suggest that coke can reduce the CuCl and thus deactivate copper as catalyst for the direct synthesis.…”

“…6 While it is shown that Cu can be converted to CuCl when reacting with CH 3 Cl at lab-scale, 6 it is also known that stable Cu 0 is formed during the reaction. 6,12 From their results, Blaser et al suggest that coke can reduce the CuCl and thus deactivate copper as catalyst for the direct synthesis. At the same time experimental results indicated that CH 3 cracking may initiate at elemental Cu.…”

“…Cu can be introduced in several ways, such as in metallic form or as chloride or oxide. ,, The catalytic effect of copper was discovered by Rochow, thus naming the reaction . Even though the mechanism of the Cu-mediated catalysis in the MCS reaction is debated, formation of a Cu 3 Si active phase, initially formed from reaction of added Cu with Si, is well accepted as essential for promoting the main reaction between Si and CH 3 Cl. , Consumption of Si can then lead to formation of elemental Cu (Cu 0 ), which is often associated with the occurrence of cracking. , Elemental copper might therefore be critical for the cracking initiation.…”

“…The coke formed in the MCS process may also contain Cl. Blaser et al have shown that, depending on reaction conditions, cracking and coke formation may occur via either a catalytic 6 or a thermal 7 route. The thermal route starts at elevated temperatures compared to the typical reaction conditions and is therefore related to hot-spots in the industrial reactor, 7 while the catalytic route is possible also under typical reaction conditions.…”

“…5,11 Consumption of Si can then lead to formation of elemental Cu (Cu 0 ), which is often associated with the occurrence of cracking. 6,12 Elemental copper might therefore be critical for the cracking initiation. Under realistic process conditions, the system is even more complex as, e.g., promoters are introduced to facilitate the reaction, 1,13 while the silicon powder used in production has a heterogeneous microstructure and contains various intermetallic phases.…”