Separation of light gas mixtures using SAPO-34 membranes

Continuous SAPO-34 membranes were prepared on porous alumina tubular suppor ts, and shown to be useful for light gas separations at low and high temper atures. Single-gas permeances of CO2, N-2 and CH4 decreased with increasing kinetic diameter. For the best membrane at 300 K, the He and H-2 permeance s were less than that of CO2, because He, H-2, and CO2 were small compared to the SAPO-34 pore, and differences in the hear of adsorption determined t he permeance order The smaller component permeated the fastest in CO2/CH4, CO2/N-2, N-2/CH4, H-2/CH4 and H-2/N-2 mixtures between 300 and 470 K. For H -2/CO2 mixtures, which were separated by competitive adsorption at room tem perature, the larger component permeated faster below 400 K. The CO2/CH4 se lectivity at room temperature was 36 and decreased with temperature. The H- 2/CH4 mixture selectivity was 8 and constant with temperature up to 480 K. Calcination, slow temperature cycles, and exposure to water vapor had no pe rmanent effect on membrane performance, but temperature changes of approxim ately 30 K/min decreased the membrane's effectiveness.