The performance of various novel mixed matrix composite (MMC) membranes for separation Of CO2 from CH4 was investigated as a function of carbon loading. Acrylonitrile-butadiene-styrene (ABS) copolymer was used as the polymer matrix and two micro-mesoporous activated carbons (AC) were chosen as inorganic fillers. A thorough analysis of the effect of temperature and pressure on the permeation rates Of CO2 and CH4 and selective properties of the ABS-AC composite membranes was done. Measurements were made for each system at four different temperatures in the range 20-50 degreesC, and in the feed pressure range from 2 to 8 x 10(5) Pa. The ABS-AC membranes showed a simultaneous increase Of CO2 gas permeabilities (40-600%) and CO2/CH4 selectivities (40-100%) over the intrinsic ABS permselectivity by increasing the percentage of carbon loaded in the mixed matrix composite membrane. (C) 2004 Elsevier B.V. All rights reserved.