Abstract
GIS-NaP1 zeolite samples were synthesized using seven different Si/Al ratios (5–11) of the hydrothermal reaction mixtures having chemical composition Al2O3:xSiO2:14Na2O:840H2O to study the impact of Si/Al molar ratio on the water vapour adsorption potential, phase purity, morphology and crystal size of as-synthesized GIS-NaP1 zeolite crystals. The X-ray diffraction (XRD) observations reveal that Si/Al ratio does not affect the phase purity of GIS-NaP1 zeolite samples as high purity GIS-NaP1 zeolite crystals were obtained from all Si/Al ratios. Contrary, Si/Al ratios have remarkable effect on the morphology, crystal size and porosity of GIS-NaP1 zeolite microspheres. Transmission electron microscopy (TEM) evaluations of individual GIS-NaP1 zeolite microsphere demonstrate the characteristic changes in the packaging/arrangement, shape and size of primary nano crystallites. Textural characterisation using water vapour adsorption/desorption, and nitrogen adsorption/desorption data of as-synthesized GIS-NaP1 zeolite predicts the existence of mix-pores i.e., microporous as well as mesoporous character. High water storage capacity 1727.5 cm3 g−1 (138.9 wt.%) has been found for as-synthesized GIS-NaP1 zeolite microsphere samples during water vapour adsorption studies. Further, the total water adsorption capacity values for P6 (1299.4 mg g−1) and P7 (1388.8 mg g−1) samples reveal that these two particular samples can absorb even more water than their own weights.
Highlights
Technology and adsorption heat pumps (AHPs) enhances the great interest in new porous materials especially nano/microporous[4]
The XRD patterns of as-synthesized GIS-NaP1 zeolite microspheres obtained from different Si/Al ratio precursor reaction mixtures are shown in Fig. 1 and phase identification was made by comparing them with standard XRD data
An extensive comparison was made among the reported water adsorption capacities for common molecular sieves, aluminophosphates, titanosilicates, metal organic frameworks (MOFs), mesoporous materials, silica-alumina based materials etc. and as-synthesized GIS-NaP1 zeolite microspheres
Summary
Technology and AHPs enhances the great interest in new porous materials especially nano/microporous[4]. With increasing concerns over ozone depletion and the global warming potential of chlorofluorocarbons and Hydrofluorocarbons, augmented energy demand and the resulting CO2 emissions, the interest in energy-efficient systems and especially, new cooling and heating technologies that make use of environmentally friendly refrigerants has grown rapidly[5]. Hierarchical porous structure of self-assembled GIS-NaP1 zeolite microspheres containing micro-, meso- as well as macropores can significantly improve the diffusion of guest molecules, transport resistance, etc., compared with single-sized micropore materials which consequentially increase mass transport through the material and maintenance of a specific surface area on the level of fine pore systems. The importance of morphology and particle size is well established for the application of microporous solids to adsorption, separation and many other applications, effect of Si/Al ratio on the phase purity, morphology and crystal size of GIS-NaP1 zeolite microspheres has been investigated. As the prime focus of this study to develop novel water adsorption material, effect of Si/Al ratio on the water adsorption potential of as-synthesized GIS-NaP1 zeolite microspheres has been studied
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