Properties of layered [Al]- and [V,Al]-magadiite catalysts as revealed by ethanol dehydration

This work describes the synthesis of the layered silicate magadiite and the insertion of V and/or Al (Si/V = 33 and Si/Al = 15 M ratios) by the seed-induced crystallization method (SIC), aiming at studying the influence of these heteroatoms in the ethylene production through the ethanol dehydration reaction. The preparation of these materials without contaminating phases or amorphization was observed by X-ray diffraction, and the presence of single and double rings characteristic of the magadiite structure was confirmed by FTIR. The presence of structural Al in tetrahedral and octahedral coordination was verified by 27Al-NMR, while the acid sites generated by the presence of this heteroatom were confirmed by TPD-NH3. In addition, this work reports for the first time a quantitative study of the use of magadiite-based lamellar catalysts in the production of ethylene from ethanol. Among the catalysts studied, the ones that generated the highest ethanol conversion, selectivity and yield to ethylene were those containing only structural aluminum ([Al]-maga-(V), [Al]-maga-(Si) and [Al]-maga-(Al)). The least active and selective to ethylene was pure silicon magadiite (maga-(Si)), which presented low ethanol conversion and higher selectivity to acetaldehyde and diethylether. Worse results were obtained for the lamellar catalysts where aluminum and vanadium were together in the framework ([V,Al]-maga-(Si), [V,Al]-maga-(Al) and [V,Al]-maga-(V)). In general, these results show that layered solids can be interesting catalysts in reaction where framework acidity is needed and are stable at high temperatures even in the presence of the water produced in the reaction.