Direct formation of element chlorides from the corresponding element oxides through microwave-assisted carbohydrochlorination reactions.

A series of technically and economically important element chlorides-such as SiCl4, BCl3, AlCl3, FeCl2, PCl3 and TiCl4-was synthesized through reactions between hydrogen chloride and the corresponding element oxides in the presence of different carbon sources with microwave assistance. This process route was optimized for demonstration purposes for tetrachlorosilane formation and successfully demonstrates the broad applicability of various silicon oxide-containing minerals and materials for carbohydrochlorination. The chlorination reaction occurs at lower temperatures than with conventional heating in a tubular oven, with substantially shorter reaction times and in better yields: quantitatively in the case of tetrachlorosilane, based on the silicon content of the starting material. The experimental procedure is very simple and provides basic information about the suitability of element compounds, especially element oxides, for carbohydrochlorination. According to the general reaction sequence element oxide-->element-->element chloride used in today's technology, this one-step carbohydrochlorination with hydrogen chloride is considerably more efficient, particularly in terms of energy input and reaction times, avoiding the isolation of the pure elements required for chlorination to give the element chlorides with use of the more corrosive and toxic chlorine gas.