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 g30%) 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.
The direct reaction of silicon with 1,4-dichlorobutane in the presence of a CuCl catalyst gives high selectivity for dichlorosilacyclopentane under some conditions. The effects of residence time, temperature, and promoters are explored, and the highest selectivity occurs at short residence time and in the presence of a Cd promoter. The reaction of silicon with methyl chloride is discussed as well. The methyl chloride reaction is usually promoted by Zn and not by Cd. The reaction of silicon with 1,3-dichloropropane and with 1,5dichloropentane was also explored; however poor selectivity to any product occurred with these other dichloroalkanes. The origin of the selectivity for the silacyclopentane is discussed in terms of low activation energy for ring closure in the five-membered ring case. Other low activation options such as reaction of silylene intermediate with C-H vs C-Cl prevent good selectivity in the dichloropropane and dichloropentane reactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.