Mechanism of the Methylchlorosilane Reaction: Improved Lab Reactor Design and Kinetic Data

Abstract

An extensive laboratory reaction kinetics study was performed on the “direct process” of methyl chloride and silicon, also commonly referred to as the methylchlorosilane (MCS) reaction. Temperature and concentrations of copper, zinc, and tin were varied. Reaction rate reproducibility and repeatability were improved by increasing temperature homogeneity in our fixed-bed reactor system. A stripped gas chromatograph (GC) oven, a detailed standard operating procedure, and small-diameter fixed-bed reactors were used to achieve good temperature control. The kinetics study incorporated multiple sample points per run as opposed to a single sample. The complete kinetics data set was analyzed with statistical analysis tools (SAS, Minitab). Three silicon utilization windows (0−15%, 15−30%, and ≥30%) were assumed to determine reaction rate descriptions by so-called transfer functions. The developed model supports a proposal wherein at least two processes exist. The main reaction (the MCS reaction) produces dimethyldichlorosilane (Di) and equimolar amounts of trimethylchlorosilane (mono) and methyltrichlorosilane (Tri). At least one side reaction occurs during the MCS deactivation phase resulting in higher levels of Tri and other byproducts.