Esterification of valeric acid over PTA supported mesoporous Al-SBA-15 as efficient solid acid catalysts

Valeric acid can be produced by selective hydrogenation of biomass-derived levulinic acid. The present work aims to synthesize ethyl valerate (EV), a fuel, fuel additive through the esterification of valeric acid with ethanol using Al-SB and x% PTA/Al-SB (x = 20%, 30% and 40 wt.%) catalysts prepared by hydrothermal and impregnation methods. Physicochemical properties were distinguished by various analytical methods. The characterization results revealed that Al-SB conserved the mesoporous structure up to 40% loading of PTA. Transmission electron microscope images exhibited that PTA species well dispersed in the uniform  pore channels of Al-SB. The catalytic performance of all the obtained catalysts towards the esterification of valeric acid with ethanol under mild reaction conditions was studied. The reaction parameters such as catalyst weight, reaction time, alcohol molar ratio and reaction temperature were optimized. Among them, 30% PTA/Al-SB catalyst exhibited the highest catalytic activity with 96% conversion of valeric acid and 100%  selectivity towards ethyl valerate. The recyclability of the prepared catalyst was also studied and it was found to be excellent.