Comparison of three different structures of zeolites prepared by template-free hydrothermal method and its CO2 adsorption properties

Abstract

In this study, zeolite sodalite SOD (50NaO2:Al2O3:5SiO2), zeolite LTA (2NaO2:Al2O3:1.926SiO2) and zeolite FAU (16NaO2:Al2O3:4SiO2) of different structures were synthesized successfully through simple conventional hydrothermal crystallization technique without using any template agent. Morphological analysis of three different types of zeolites revealed that the samples exhibit three different shapes such as the “Raspberry-like”, “Dice” cube like and “Octahedral” shaped morphology respectively. The thermal stability was found to be about 4.8%, 14.6% and 20.5% for the synthesized zeolites SOD, LTA and FAU respectively. From the N2 adsorption-desorption studies, it was observed that adsorption types IV and I correspond to the synthesized samples. CO2 adsorption by the synthesized zeolite SOD, LTA and FAU were examined in the pressure range from 0 to 101.325 kPa at a constant temperature of 297.15 K. The highest adsorption capacity of 3.7 mmol/g was obtained for zeolite FAU. The synthesized zeolite was studied using a nonlinear regression curve fit to determine the adsorption isotherm model using Langmuir and Freundlich isotherm model. It has been found that the synthesized zeolites have a large electric field gradient due to which they can strongly adsorb quadrupole of CO2 molecules.