Diffusion of methane in high-silica CHA zeolite

Diffusivity of methane in CHA-type zeolite (Si/Al=160) was investigated by uptake rate method using a volumetric adsorption setup. The methane diffusivities were measured over a range of temperature (298-393K) and pressure (0-0.9bar) to study the effect of temperature and pressure on the diffusion coefficients. The results showed that the diffusivities decrease with pressure while they increase with increase in temperature. Furthermore, activation energy of diffusion decreases with pressure. The limiting values of activation energy and diffusivity of methane (at 298K) at p=0 (zero loading) were estimated to be 18.0kJ/mol and similar to 3.2x10(-13)m(2)/s, respectively. The results were compared with the diffusivities of CH4 in 12-, 10- and 8-MR zeolites.