Cellulosic semipermeable membranes containing silicon compounds

Claim 1

A semipermeable membrane useful for separating a gaseous mixture of carbon dioxide and methane into enriched fractions of each, the membrane prepared from at least one cellulosic polymer and at least one silicon compound of the formulae ##STR2## where each R is independently a hydrogen radical, a halide radical, or an aliphatic, cycloaliphatic or aromatic radical or an inertly-substituted derivative of any one of them, with the provisoes that where R is directly bonded to oxygen, R is not a halide radical and in formula I when n is zero, at least one R is a radical other than hydrogen; n is an integer of 0-4; p is an integer of at least 1; q is an integer of 1-3; and the silicon compound comprises between about 5 and about 50 weight percent of the membrane, based on the combined weight of the silicon compound and the cellulosic polymer.