(520d) Surface Modified SAPO-34 Membranes: Synthesis, Characterization and CO2/CH4 Separation | AIChE

(520d) Surface Modified SAPO-34 Membranes: Synthesis, Characterization and CO2/CH4 Separation

Authors 

Venna, S. R. - Presenter, University of Louisville


SAPO-34 membranes have been successfully employed to separate CO2 from different gases owing to its chemical and thermal stability, unique shape selectivity, molecular sieving properties, and atomically ordered microporous structure. The control of the crystal size, extent of crystallinity, homogeneity, and preferential CO2 adsorption capacity are highly desirable properties to prepare improved SAPO-34 membranes for CO2 separation. Smaller crystal size and narrow particle size distribution potentially lead to thinner membranes, larger-accessible surface area, reduced diffusion resistance, which impact positively the SAPO-34 membrane performance in functional gas separation applications. Rational surface modification of SAPO-34 crystals will lead to membranes displaying preferential CO2 adsorption and consequently to improved membranes for CO2 separation over light gases.

Herein we present the successful synthesis of SAPO-34 seeds and membranes displaying small, uniform crystal size, high surface area and enhanced CO2/CH4 adsorption ratio employing crystal growth inhibitors (CGI) such as polyethylene glycol, Brij-35 and methylene blue. The resultant SAPO-34 crystals displayed BET surface areas up to 700 m2/g, enhanced CO2/CH4 adsorption ratios (>9), and crystal sizes in the ~0.6-0.9 μm range, with narrow particle size distribution. The relatively high N/H molar ratios observed in the SAPO-34 crystals prepared with CGI led to high CO2/CH4 adsorption capacities. Due to its small crystal size, narrow particle size distribution, higher surface area, and preferential CO2 adsorption capacities over CH4, these crystals represent ideal phases to prepare thin supported membranes for CO2/CH4 separations. SAPO-34 membranes were prepared on γ-Al2O3 supports by secondary seeded growth employing these high surface area and surface modified seeds. The separation performance for equimolar CO2/CH4 gas mixtures is presented.