Study on improving the SO2 tolerance of low-temperature SCR catalysts using zeolite membranes: NO/SO2 separation performance of aluminogermanate membranes

A novel idea is proposed to improve the SO2 tolerance of low-temperature selective catalytic reduction (SCR) catalysts by using a RHO zeolite membrane to separate NO from SO2 to reduce the contact between SO2 and the SCR catalysts. RHO zeolite membranes were prepared on a macroporous stainless steel tube. The results from XRD and SEM measurements indicated that the crystals on the surface were pure RHO zeolites and a uniform and continuous layer of RHO zeolite membrane covered the surface of the support. Permeation measurements using different feed gases indicated that the prepared RHO zeolite membrane could effectively separate NO from SO2. A maximum NO/SO2 selectivity of 36.14 was obtained when using NO/SO2/N2 mixtures. The SO2 permeation decreased a lot in the present of water. Surface diffusion and activated diffusion were believed to be the main transport mechanisms of the RHO zeolite membrane.