KOH-modified Nano-ZnO from hydration-dehydration as efficient catalyst in the basic transesterification of rice bran oil

Abstract

Amphoteric zinc oxide has low toxicity and solubility and KOH was proved to be very effective in enhancing catalytic performance of many substances. In this research, nano-zinc oxide (Nano-ZnO) was prepared through environmental-friendly hydration-dehydration method, modified with 5-25 % KOH by wet impregnation and used in esterification/transesterification of rice bran oil (RBO) to form biodiesel. The catalyst was characterized by Branneur-Emmer-Teller (BET) surface analysis, X-Ray powder Diffraction (XRD) and basic strength determination by Temperature Programmed Desorption (TPD)-CO₂ and the biodiesel prepared was characterized by Nuclear Magnetic Resonance (NMR) spectroscopy. The result shows this method produced nano-ZnO having average crystallite size of 30-40 nm at an optimum temperature of 400^oC and the wet impregnation method used disperses KOH well into the ZnO crystal lattice and improves its basic strength. Basic heterogeneous transesterification was carried out at 65 ^oC, 5% catalyst, 9:1 methanol to oil ratio and 3 hours-time. It shows the formation of biodiesel and that there is increase in basic strength of modified catalyst causing increase in catalyst activity and biodiesel yield. Optimum 96 % conversion was obtained from 15 % KOH-modified catalyst, proving that ZnO can be prepared by hydration-dehydration and its modification with KOH produced effective catalyst in transesterification for biodiesel preparation.

Keywords: Catalyst modification, TPD-CO₂, nano-zinc oxide, transesterification, biodiesel