A comparative study on chemical characteristics of waste cooking oil biodiesel synthesized using nanohybrid catalyst at low methanol / Nur Shaqira Shamsol Kamal and Prof. Madya Dr. Abdul Hadi Zainal

Biodiesel is considered among the developed biofuels as a promising replacement for fossil diesel, which can minimize greenhouse gas and pollutant emissions. Due to the decreasing trend in economic oil reserves, environmental problems triggered by the use of fossil fuel, and the price of petroleum products that costing a bomb on the global market, biodiesel production from waste cooking oils (WCO) for diesel substitute is particularly important. Nanohybrid catalyst has already been identified as an excellent biodiesel synthesis catalyst. Nevertheless, the alcohol to oil molar ratio is considered to be the most crucial in the biodiesel production dynamics. The present review paper briefly cover the effect of different process conditions, type of catalyst used, low methanol-to-oil molar ratio (< 6), reaction time, the chemical component which includes flash point, pour point, cloud point (CP), cetane number (CN) and the optimum process condition for the waste cooking oil (WCO) biodiesel production. The recent advancements involving nanohybrid catalyst for enhancing the overall quality of biodiesel have been discussed. Twenty-two papers are used as the main references to identify the type of nanohybrid catalyst used and the optimum process conditions for the waste cooking oil (WCO) biodiesel production at low methanol to oil molar ratio. In conclusion, all the catalyst investigated in this present review paper shown the positive result where the quality of the biodiesel produced meets the ASTM D6751 standard. Graphical representation in this present review paper shows that among all the catalysts investigated in this present review paper, the Na2SiO3 nanohybrid catalyst has great potential to be used as a low-cost catalyst in waste cooking oil (WCO) biodiesel production as Na2SiO3 nanohybrid catalyst yield 77.33 % biodiesel at 65 °C, 180 minutes reaction time and 6:1 methanol to oil molar ratio.