Micro- and mesoporous CuBTCs for CO2/CH4 separation

Micro- and mesoporous CuBTCs, referred to as micro- and meso-CuBTCs, were synthesized, and tested for their capacity to adsorptively remove CO2 from a binary mixture of CO2-CH4. Physicochemical analyses of the thermally treated Cu-BTCs were performed. The CO2 and CH4 adsorption isotherms for the Cu-BTCs at 25 °C in the pressure range 0-3MPa were experimentally measured and implemented for calculating the CO2/CH4 selectivity as a function of pressure and CO2 concentration using the ideal adsorbed solution theory (IAST). The CH4 adsorption capacity of meso-CuBTC at 3MPa was reduced to 43% of that of micro-CuBTC, whereas the CO2 adsorption capacity of meso-CuBTC at 3MPa was reduced to 27% of that of micro-CuBTCs. Consequently, meso-CuBTC shows a higher CO2/CH4 selectivity compared to micro-CuBTC. It was also found that the selectivity of the CuBTCs could be enhanced by lowering the partial pressure of CO2. This was ascribed to the larger abatement of the adsorption capacity for CH4 than for CO2, resulting from a reduction of the interaction of CH4 with the surface of pores of meso-CuBTC of which the pore size had been augmented.