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Zeolite Membrane Synthesized Employing Crystal Growth Inhibitors for Carbon Dioxide Separation

Surendar Reddy Venna and Moises A. Carreon. Chemical Engineering Department, University of Louisville, Ernst hall, Chemical Engineering Department, Belknap campus, Louisville, KY 40292

The separation of CO2 from natural gas or H2 at industrially relevant conditions is an important environmental and energy issue. Polymeric membranes have limitations based on operating temperature and chemical interactions that cause swelling and degradation. Due to their high thermal resistance, mechanical strength, chemical stability, and 0.38 nm uniform-sized pores of molecular dimensions SAPO-34 zeolites are ideal materials for carbon dioxide (kinetic diameter 0.33 nm) separation from methane (kinetic diameter 0.38 nm). Typically small crystals (less than 5 m) with narrow size distribution lead to superior CO2 separation performance.

Here, we report the synthesis of SAPO-34 employing the crystal growth inhibitors (PEG, C12E6 & MB) for both seed and secondary growth to decrease the crystal size and improve textural and morphological properties of SAPO-34 membranes. The use of crystal growth inhibitors produced membranes with ~0.6 m crystal size and narrow particle size distribution displaying cubic and rectangular morphologies. The obtained SAPO-34 seeds were characterized by BET, XRD, SEM, FTIR, TGA and CO2/CH4 adsorption studies. The SAPO-34 crystals showed chabazite structure confirming the crystallinity of the material with surface areas up to ~700 m2/g. The SAPO-34 crystals were used as seeds and gels to prepare membranes on the inside surface of the tubular -Al2O3 supports by hydrothermal treatment. The CO2/CH4 separation performance of synthesized SAPO-34 membranes was studied at different conditions of pressure and temperature.