VERFAHREN ZUR HERSTELLUNG VON ACYLOXYSILANEN

Acyloxysilanes are prepared by reacting a chlorosilane with an aliphatic carboxylic acid in a column at an elevated temperature wherein the aliphatic carboxylic acid in the vapor phase reacts with the chlorosilane in the column. The improvement comprises introducing the carboxylic acid into the column in a plurality of feed streams preferably at such a rate that the carboxylic acid exceeds 1.3 moles per gram atom of silicon-bonded chlorine in the column and removing low boiling reaction by-products and hydrogen chloride gas from the top of the column while collecting the acyloxysilane product dissolved in the aliphatic carboxylic acid at the bottom of the column. At least one feed stream of aliphatic carboxylic acid must be located above the chlorosilane feed stream. Aliphatic carboxylic acid is also provided from at least one source located below the chlorosilane feed stream, for example, from at least one feed stream located below the chlorosilane feed stream or from aliphatic carboxylic acid in a reboiler at the bottom of the column or both. In a preferred embodiment, methyltriacetoxysilane is prepared by reacting methyltrichlorosilane with acetic acid in a heated fractionation column.