Efficient mesoporous SO42−/Zr-KIT-6 solid acid catalyst for green diesel production from esterification of oleic acid

•Hydrothermal synthesis and characterization of mesoporous Sulphated Zr-KIT-6 (SZK) solid acid catalyst.•Biodiesel produced from oleic acid and jatropha oil with the conversion of 96% and 85% at 120 °C.•The conformational mechanism for esterification and transesterification proposed.•SZK is an environmentally benign catalyst and cost effective.•The produced green diesel meets standard petro-diesel properties and can be used as blend for commercial use.

Highly ordered mesoporous sulphated Zr-KIT-6(x) [x = Si/Zr] solid acid catalysts were successfully synthesized by hydrothermal method. Different weight fractions of zirconium were loaded into fixed gel in the acidic medium and then sulphated to get sulphated Zr-KIT-6(x) catalysts. X-ray diffraction (XRD), surface area analysis (Brunauer-Emmett-Teller equation) and microscopic techniques (SEM and TEM) results suggest the incorporation of Zr4+ into the silica KIT-6 framework by isomorphous substitution between Zr4+ and Si4+ ions. Diffuse reflection spectroscopy (DRS-UV) results reveal that Zr atoms are highly dispersed in +4 oxidation state. During the experiments it was observed that sulphated Zr-KIT-6 (20) showed the highest catalytic conversion for esterification of oleic acid (96%) and transesterification of jatropha oil (85%) at an optimized reaction conditions of 120 °C, 20:1 methanol to reactant molar ratio, 4 wt% catalyst loading and 6 h reaction time. The ester yields of 95% and 80% obtained from oleic acid and jatropha oil respectively. The used catalysts could be recycled up to three cycles with significant activity and stability.

Graphical abstractEsterification of oleic acid by Sulphated Zr-KIT-6 (20).Download high-res image (139KB)Download full-size image