Biodiesel production from crude rice bran oil using eggshell waste as catalyst impregnated with silver nanoparticles

Abstract

Biodiesel is a promising renewable fuel with many attractive features such as high combustion efficiency, biodegradability, and less toxic exhaust emission. This study investigated an environmentally friendly method for biodiesel production from crude rice bran oil (CRBO) using calcium oxide (CaO) from eggshell waste as a catalyst via transesterification reaction. A two-level three-factor full factorial experimental design was used to determine the effect of the impregnation of silver nanoparticles (AgNPs), calcination temperature and heating rate as independent variables on the biodiesel yield. An optimum biodiesel yield of about 92% was obtained using AgNPs impregnated CaO catalyst prepared from eggshell waste using a heating rate of 5oC/min during calcination at temperatures in 800-1000oC range. Biodiesel production was carried out using esterified CRBO. The optimization of transesterification of CRBO was carried out by response surface methodology (RSM) based on central composite design (CCD) with reaction conditions of methanol-to-oil molar ratio, catalyst loading, and reaction time. A maximum value of biodiesel yield of about 89% was obtained at 9:1 methanol to oil molar ratio, catalyst loading of 2.5 (w/w) and reaction time of 9 h. The validation experiments for transesterification of CRBO and RRBO under optimum reaction conditions was 92.6% and 92.0%, respectively. The assessment of catalyst reusability indicated that the catalyst performance declined gradually and resulted in about 5% loss in performance. In comparison, under the optimum transesterification condition using CaO catalyst without AgNPs impregnation resulted in a slightly lower biodiesel yield of about 90.5%. The assessment of catalyst reusability indicated that the catalyst performance declined gradually and resulted in about 5% loss in performance after being recycled and reused for five consecutive cycles.