C3H6-permselective silica hybrid membranes were prepared by using a counter-diffusion chemical vapor deposition (CVD) method. Propyltrimethoxysilane and hexyltrimethoxysilane (HTMOS) were used as silica precursors and O-3 and O-2 were used as oxidants. HTMOS was a suitable silica precursor for high-temperature CVD because of its high thermal stability. The N-2/SF6 permeance ratio decreased from 64 to 12 as the deposition time increased from 5 to 90 min. The maximum N-2/SF6 permeance ratio was 2.2 Chi 10(5) through the membrane deposited at 450 degrees C for 5 min. The C3H6/C3H8 permeance ratio was 414 (C3H6 permeance 1.0 Chi 10(-8) mol m(-2) s(-1) Pa-1). through this membrane. (C) 2014 Elsevier B.V. All rights reserved.