Thin SAPO-34 membranes synthesized in stainless steel autoclaves for N2/CH4 separation

SAPO-34 membranes were synthesized in stainless steel autoclaves and teflon autoclaves with water bath, ice/water bath and flowing water cooling towards N-2/CH4 separation. The best membrane displaying unprecedented N-2 permeance of similar to 2600 GPUs and N-2/CH4 separation selectivity of 7.4 was prepared in the stainless steel autoclave with a water bath cooling. A more selective membrane with a N-2/CH4 selectivity of 8.6 and N-2 permeance of similar to 2150 GPUs was also prepared in the stainless steel autoclave but with an ice/water bath cooling. The heat flux, rate of the stainless steel autoclaves during membrane preparation was similar to two orders of magnitude higher than that of the membranes prepared in conventional teflon autoclaves. The higher heat flux rate decreased the gel temperature faster, and slowed the kinetics of crystal growth. The slow crystal growth rate during the cooling translated into thinner and more permeable membranes. These SAPO-34 membranes may have great potential for economic N-2 rejection from natural gas.