Synthesis of hierarchical porous Zeolite-Y for enhanced CO2 capture

In the present study, a facile and one step approach has been developed for the synthesis of hierarchical porous zeolite-Y using bifunctional cationic polymer, polydiallyldimethyl ammonium chloride (PDDA) as a mesopore directing template. The effects of various synthesis parameters such as hydrothermal reaction temperature, time, amount of PDDA and NaOH were systematically investigated to produce crystalline and hierarchical zeolite-Y crystals (PDYs). All the synthesized zeolite-Y samples were characterized by XRD, FT-IR, SEM, EDAX, TEM, TGA, CO2-TPD and Nitrogen adsorption-desorption measurements. The characterization results showed that the zeolite-Y samples synthesized at optimized ratios of PDDA/Al2O3 and NaOH/Al2O3 exhibited higher crystallinity, higher BET surface area and larger total pore volume in comparison to the sample synthesized in the absence of the template (ZY). Interestingly, the hierarchical porous zeolite-Y samples (PDY-7) displayed substantial enhancement in CO2 adsorption capacity (5.40 mmol/g) at 298 K and 100 kPa as compared to the non-templated one (ZY) (4.5 mmol/g). The effective improvement in CO2 adsorption performance of PDY samples is attributed to the existence of interconnected micro-meso channel network, the higher total pore volume and higher concentration of acid-base sites (due to the lower Si/Al ratio). Owing to the higher CO2 adsorption capacity, the PDY samples also displayed high equilibrium selectivity for CO2 over N2 (~250) as well as over CH4 (~110) at 298 K. The enhanced CO2 adsorption capacity combined with the high CO2 adsorption selectivity renders the hierarchical zeolite-Y an excellent contender for the efficient CO2 capture.