Defect-free gamma-Al2O3 and La2O3-modified gamma-Al2O3 membranes were prepared for recovery of acetone from nitrogen by multilayer diffusion and capillary condensation mechanisms. There existed an optimum range for acetone permeance (similar to 8 x 10(-7)mol/m(2).s.Pa) and acetone-nitrogen separation factor (similar to 1000) with respect to membrane temperature or feed composition. Hysteresises of acetone permeability and separation factor were also found between desorption and adsorption. The La2O3-modified gamma-Al2O3 membrane appears to be the most effective for use in the VOC recovery process as compared to polymeric, Vycor, and unmodified gamma-Al2O3 membranes.