Influence of the support on the catalytic properties of Keggin type heteropolyacids supported on niobia according to two different methodologies: evaluation of isopropanol dehydration and Friedel–Crafts alkylation reaction

In this study, Keggin type heteropolyacids (HPW) supported on niobia were prepared following two different methodologies, including the incipient wetness impregnation technique, and using water as a polar solvent. In methodology I, the support was impregnated after calcination at 300 °C, with HPW concentrations equivalent to 30 and 50% of coverage, while in methodology II the support, without pretreatment, was impregnated with HPW concentrations equivalent to 30 and 50% of coverage and further calcined at 300 °C. The catalysts were characterized by X-ray diffraction, nitrogen adsorption, chemical analysis by optical emission spectrometry from plasma, FT-IR, FT-Raman, 31P MAS NMR, and acidity determination by catalytic decomposition of isopropanol. It was found that the best catalysts, after lixiviation tests, were the ones with 50% of HPW content produced through methodology II (50MIIL300). After identification of the best catalyst in the reaction of dehydration of isopropanol, we studied the reaction of anisole with benzyl alcohol and benzyl chloride and the results obtained were comparable to other catalysts reported in literature.