| dc.description.abstract | This project focuses on the ionothermal synthesis and characterization of conventional and hierarchical SAPO-11 and the incorporation of iron into the SAPO-11 framework. Conventional SAPO-11 was synthesized by following the one-pot synthesis method reported by Azim et al.1 Synthesis of hierarchical SAPO-11 was investigated by adapting and modifying the method reported by Azim et al.1 It is significant to note that an ionothermal synthetic approach has not been previously reported in the literature to synthesize hierarchical SAPO-11. CTAB, PVA, TPOAC, and F127 were employed as meso-SDA. Iron was introduced to the synthesis in order to study the possibility of incorporating iron into the framework isomorphically, and a study of ionothermal approach to synthesize FeSAPO-11 has also not been previously reported in the literature. Characterization of synthesized material was carried out by PXRD, N2 physisorption, CO probed FTIR, and EDX. XAS was conducted for the iron introduced conventional and hierarchical SAPO-11. Further, activity and the accessibility of incorporated iron were tested by employing propene HC-SCR for deNOx as a model reaction.
The PXRD studies confirmed that the novel approach of introducing meso-SDA to the ionothermal synthesis gel was successful in producing phase pure SAPO-11. Nitrogen physisorption studies were used as a primary tool to investigate the presence of a bimodal pore system. BET surface area, pore-volume, BJH pore size distribution, and hysteresis information obtained from nitrogen physisorption studies were further compared with SEM images to understand the actual hierarchical nature of synthesized materials. Among the meso-SDA been used, only CTAB has effectively increased the external surface area and the external pore volume indicating the possible presence of hierarchical nature containing mesopores with a broad pore size distribution. The acidity of the conventional and the hierarchical SAPO-11 samples was investigated using CO-probed FTIR. Unfortunately, there was no significant Brønsted acidity present in the samples, limiting the possibilities of employing catalytic model reactions that require stronger acid sites.
Iron incorporated samples were analyzed with XAS to understand the valance state and the nature of local coordination. It was confirmed that iron had been incorporated in single-site, possibly isomorphically into the AEL framework of SAPO-11. | |