Biodiesel production from waste cooking oil selecting a solid catalyst derived from activated coconut coir

Abstract

In the quest for cost-effective production of biodiesel, selection of cheap feedstocks and catalysts play the significant role. Waste cooking oil is abundantly available from all types of restaurants throughout the world. Catalyst selected for this feedstock should be heterogeneous. Coconut coir, which is biomass and source of carbon, was selected for its study as a catalyst for biodiesel production. This paper is based on a comparison of a solid catalyst by two processes: (i) sulphonation of coconut coir char (pyrolysed at 500°C for 3 hours) and (ii) digestion of pyrolysed coconut coir with 10% NaOH at 70°C for 4 hours followed by sulphonation. Comparison of both the solid catalysts thus prepared was done based on their physical properties, total acid density, SEM and FT-IR analysis. The higher percentage of fixed carbon content, higher acid density and BET surface area, better morphological surface and pronounced presence of sulphonic (-SO3H), carboxylic (-COOH) and hydroxyl (-OH) groups favours the selection of catalyst prepared by the second method for further study for biodiesel formation using waste cooking oil as the feedstock. Effects of various parameters on biodiesel production: alcohol to oil ratio (A:O), time of reaction, reaction temperature and catalyst loading were studied. At the optimised conditions, the biodiesel conversion was 90.12%. Biodiesel produced by the method was characterised regarding fuel properties and were found close with the standard values.