Tailoring pores of AFN-related zeolites for enhanced separation of CO2/N2 and CO2/CH4

Abstract

Zeolites with small-pores (8-ring) are widely used in separation of small-molecule gas, however, the precise tuning of aperture sizes to achieve the ideal selectivity still remains challenge due to their limited topology structures. In this work, SAPO-14 zeolite with AFN topology featuring by different 8-ring windows in three-dimension directions has been synthesized and studied in the separation of CO2/N2 or CO2/CH4. Aiming to further adjust pores and channels of the adsorbents, the composite zeolites of SAPO-14 and SAPO-34 (CHA) are prepared by seed-assisted method, and multi-cycle crystallization is adopted to form the interconnected pores of composites and reduce the crystal size. SAPO-14/SAPO-34 zeolites exhibit the comprehensive performance of high CO2 capacity of SAPO-34 and good selectivity of SAPO-14 due to their appropriate pore structure. At 298 K, the CO2 capacity of S-1 composite is 47.24 cm3 g−1, giving a high gas selectivity for CO2/N2 (68.64) and CO2/CH4 (21.61). The highly-efficiency and good reproducibility in gas separation are verified by the binary breakthrough experiments. The strategy of composite zeolite proposed by this work can effectively regulate the pores of adsorbent, thus endow them acceptable selectivity and capacity for target gas.