Synthesis of nanosized IM-5 zeolite and its CH4/N2 adsorption and separation

Abstract

Reduction of zeolite crystal size from the micron scale to the nanoscale leads to a significant increase in specific surface area, favoring mass-transfer pathways. Here, we have prepared nanoscale (ca. 30–80 nm) IM-5@100 zeolite (IMF type) by a facile strategy of regulating the amount of Al source in the starting gel, and have investigated its CH4/N2 adsorption and separation properties. We found that on decreasing the amount of Al source, the crystal size of the product changed significantly, decreasing from strips of length about 1 μm to irregular nanocrystals. Compared with micron-sized IM-5@50, the mesopore volume of IM-5@100 was increased fourfold from 0.12 cm3/g to 0.49 cm3/g, its external surface area was increased from 38 m2/g to 118 m2/g, and its DFT pore size distribution based on N2 adsorption/desorption showed a mesopore distribution in the range 5–10 nm. Adsorption kinetics tests showed that nano-IM-5@100 can achieve adsorption equilibrium more swiftly and exhibits better mass-transfer performance. Moreover, IM-5@100 showed good adsorption capacity for CH4 (17.8 cm3/g) and high IAST selectivity (4.7) for CH4/N2 (50:50, v/v). Breakthrough experiments have indicated that IM-5@100 permits efficient practical separation of CH4/N2.