Improvement of potassium species dispersed on hierarchical zeolite NaY by using combined methods between ultrasound and microwave-assisted impregnation as catalysts for transesterification of refined Jatropha seed oil

Abstract

Refined Jatropha seed oil, non-edible vegetable oil is an interesting source for biodiesel production because it has low commercial value. Thus, this work aimed to develop a novel method, combined techniques between ultrasound and microwave-assisted impregnation ((UA-IP and MA-IP) for potassium (K) loaded on hierarchical NaY zeolite synthesized from rice husk silica as catalysts for transesterification of Jatropha seed oil. Hierarchical NaY zeolite was impregnated with potassium acetate in an acetic acid buffer solution with various contents (xK/NaY, where X = 6, 8, 10, and 12 wt%) by UA-IP and MA-IP. The best catalyst from the novel method was further compared to the control method, prepared by only UA-IP. Results from XRD and N2-sorption indicated the remaining NaY structure in all samples after calcination. The total surface area determined by BET method decreased with the K loading but basicity increased with K loading suggested by CO2 -TPD. The active species was mainly K2CO3 confirmed by FTIR. When tested in transesterification at a temperature of 60 °C and 3 h with methanol: oil molar ratio of 16:1, the biodiesel yield improved with the K loading and the highest biodiesel yield of 97 ± 1.4% was obtained by 12K/NaY. The 12K/NaY gave a higher yield than 12K/NaY-control (97 ± 1.4% vs 90.7 ± 1.1%), providing the high reusability of five cycles with the biodiesel yield of 88.2 ± 1.3%.