Improvement of Fuel properties and Fatty Acid Composition of Biodiesel from Waste Cooking Oil after Refining Processes

Abstract

This work compares the physicochemical properties and fatty acid (FA) compositions of waste cooking oil (WCO) collected after deep frying periods from local restaurant with samples of refined cooking oil (RCO) produced after degumming, alkaline and bleaching treatments. The refined oil were initially kept/stored in the refrigerator at 4oC and the biodiesel produced was subjected to gas chromatography mass spectroscopy (GCMS) for FA profile, and to Fourier Transform Infrared (FTIR) analyses to monitor esterification reactions. The degree of oil usage affected WCO properties and fatty acid composition. Density of refined cooking oil RCO and WCO varied between 0.90 and 0.93 (g/cm3), and of refined cooking methyl ester (RCME) and waste cooking methyl ester (WCME) between 0.88 and 0.91 (g/cm3). The pH of RCO and WCO varied between 7.36 and 8.61 and that of RCME and WCME between 5.11 and 5.59. The results of RCO and RCME showed corresponding improvements over the WCO and WCME in recovery yield, acid value, saponification value, iodine value, peroxide value, cetane number, kinematic viscosity, pour, smoke, flash, and fire points. Fatty acids analyses similarly showed comparable differences between the RCO and WCO with percent increase in octanoic ethyl acid (276.54%), benzoic acid, butyl ester (69.79%), hexadecanoic acid 15- methyl esters (267.33%) and reduction in 9,17-Octadecanoic acid (99.20%), and 9- octadecenoic acid(35.98%), respectively. The hexadecanoic acid, methyl ester (54.10%) was the most abundant. This result confirms the suitableness of WCO as feedstock for biodiesel.