Investigation of the permeability of pure gases in sol-gel derived Al2O3 membrane

The preparation, characterization and pure gas permeation of sol-gel derived alumina membranes were investigated in this work. The effects of acid concentration/type and water content on the particle size in the sols and pore size distributions of the unsupported membrane were investigated by N-2 adsorption/desorption isotherms and Dynamic Light Scattering. Increasing the H+/Al3+ mole ratio from 0.1 to 0.25 caused the hydrodynamic sol particle size and BJH pore size to decrease from 65 to 30 nm and 3.6 to 2.9 nm, respectively. The pore size increased from 2.8 nm to 3 rim upon increasing the calcination temperature from 500 to 600degreesC. Unsupported membranes were heat treated in the 200 to 1200 T range for the characterization of the phase structure. Pinhole and crack free alumina membranes about 3 mum (2-layer) in thickness was observed from the SEM pictures with insignificant infiltration. The CO2 permeability through the double layer gamma-Al2O3 membrane calcined at 600degreesC was 2.25*10(-7) mol/m(2).s.Pa, and had a slight pressure dependence indicating Knudsen Diffusion and Laminar Flow being the effective transport mechanisms. Upon the calcination of a similar 2-layer alumina membrane at 500degreesC, the CO2 permeability decreased to 1.51*10(-8) mol/m(2).s.Pa. without pressure dependence.