Facile fabrication of aluminum-promoted vanadium phosphate: A highly active heterogeneous catalyst for isopropylation of toluene to cymene

Vanadium phosphate is well known as a heterogeneous catalyst in gas phase oxidation reactions. To date, there has been little interest in carrying out liquid-phase reactions with vanadium phosphate as catalyst. Herein, we report the catalytic activity of vanadium phosphate and aluminum-promoted vanadium phosphate toward liquid-phase isopropylation of toluene to cymene. The catalysts were unambiguously characterized by X-ray diffraction, N2 adsorption–desorption, FT-IR technique, UV–vis DRS, and FE-SEM. The total acid sites were estimated by an NH3 TPD analyzer. XPS was used as a powerful tool to know the electronic environment of the catalysts. The optimization of the reaction was carried out by varying temperature from 75 to 150 °C and molar ratio (toluene: isopropanol) from 1:1–1:3. Under optimum reaction conditions, 5 wt.% aluminum-promoted vanadium phosphate showed 90% conversion with 85% selectivity to p-cymene.