Rational design of hierarchical porous Cu/SAPO-34 obtained with sustainable templates

Abstract

A simple procedure was developed to synthesize hierarchical Cu exchanged SAPO-34 material by bottom-up method. To induce two levels of porosity (micro and mesoporosity) in SAPO-34, traditional tetraethylammonium hydroxide (TEAOH) to address the micropores formation and sucrose, a low-cost and green mesoporogen to address the mesopore formation, have been used. The Si loading was also modulated to achieve hierarchical SAPO-34 with a high concentration of Brønsted acid sites that are the locus of the exchange with Cu ions. The exchange method to introduce Cu in chabazite (CHA) architecture was deeply investigated to reduce the number of post-synthetic steps and to obtain a hierarchical Cu/SAPO-34 catalyst with Cu(II) sites stabilized in the 6-membered ring (6 MR) available to perform selective catalytic reduction of NOx with NH3 (NH3-SCR). Physico-chemical characterization was performed by using structural and spectroscopic techniques to elucidate the properties of hierarchical SAPO-34 before and after Cu introduction.