Comparison of T and W zeolite membranes for separation of O2/SF6 mixtures

Greenhouse effect is one of the most significant dilemmas in environmental aspects that cause negative results in nature and society. SF6 is a very potent greenhouse gas. The global warming potential of the gas is 23,900 times greater than that of CO2, and its atmospheric lifetime is about 3,000 years. Two different zeolite membranes (T (0.36 – 0.67 nm) and W (0.27 – 0.51 nm) were synthesized and their performances were evaluated in separation of O2/SF6 mixtures. They were selected due to their different silicon modules (SiO2/Al2O3) and their polarities. Effect of feed pressure on separation of O2/SF6 was also investigated. The results showed that T zeolite membrane (silicon module = 25) provides higher separation factor of O2/SF6 (50) compared with W zeolite membrane (20.1). Also, increasing feed pressure from 3 up to 5 bar decreases separation factor of O2/SF6 and increases O2 and SF6 permeances through both the zeolite membranes. From the results, it was concluded that increasing pressure decreases the surface diffusion contribution through the molecular sieve pores, and increasing the Knudsen flow and the viscous flow contributions.

T zeolite membrane, W zeolite membrane, Gas separation, Ideal selectivity of O2/SF6, Silicon module effect