The flat sheet composite membranes with selective layer made from poly (1-trimethylsilylpropyne) (PTMSP) based on TaCl5/TIBA and NbCl5 were developed and studied. The structure of composite membranes was investigated by scanning electronic microscopy (SEM). It was found that non-defected PTMSP layer is achieved on polyacrylonitrile (PAN) support (the effective thickness of selective layer is 1-7 mu m). The permeability of membrane in relation to single gases (O-2, N-2, CO2, H-2) and C-1-C-4 hydrocarbons were measured by differential GC permeability method. It is shown that selectivity of homogenous PTMSP films of simple gases is realized for composite membrane. High separation properties for hydrocarbons alpha (propane/methane)approximate to 5, alpha (i-butane/methane)approximate to 11.5 at high flux of components through membrane are demonstrated. (C) 2006 Elsevier B.V. All rights reserved.