Catalytic performance and ultrasonic-assisted impregnation effects on WO3/USY zeolites in esterification of oleic acid with methyl acetate

USY commercial zeolite was used in the esterification of oleic acid and methyl acetate. Ultrasonic-assisted and conventional wet-impregnations of WO3 were compared and influence on catalytic activity and selectivity were evaluated. The reaction was performed with a methyl acetate to oleic acid molar ratio of 10:1, 10 wt% of catalyst and 240 degrees C. The catalyst samples were characterized using XRD, XRF, SEM, BET, Al-27 and Si-29 MAS-NMR, FTIR and NH3-TPD and a liquid pyridine adsorption method to identify acid sites nature. Characterization results showed high dispersion of WO3 species. Acid sites nature, strength, and distribution showed that the strongest sites of the parent USY were changed to moderated ones. Bronsted acid sites of USY were partially blocked by tungsten oxide species. Ultrasonic-assisted activation presented the highest selectivity in the esterification of oleic acid with methyl acetate. 10% and 20% WO3/USY/US zeolites reached 79.4 wt% and 80.8 wt% conversion into methyl oleate, showing similar catalytic performance to short-chain alcohols as acyl acceptors.