A New Process for the Production of Biodiesel from Used Vegetable Oil

Abstract

Production of biodiesel from triglycerides (vegetable oil) is usually done through transesterification with alcohols in the presence of acid or base catalyst. When this oil contains free fatty acid of more than 5 percent due to repeated use for frying, the transesterification process can not be used to produce biodiesel. In this paper, a new method for producing biodiesel even for used vegetable containing higher or any amount of free fatty acid is discussed. This method involves complete saponification of the triglycerides and free fatty acids (FFA) by reacting it with sodium hydroxide solution to give sodium salt of fatty acid (SOAP). This soap when treated with a mineral acid, separates into four layers, the top layer which is also the primary layer is the free fatty acid (FFA), the second layer is the glycerol, the third layer is the water layer, and the bottom layer is the residue of solid sodium salt. The top layer free fatty acid(FFA) is easily separated and then esterified with ethanol in the presence of a mineral acid as a catalyst to get the biodiesel (ethyl ester of FFA). The product obtained by the above process is analyzed and confirmed by FT-IR spectra. This process does not involve high temperature and pressure. The advantages of this new process are that it is much environmentally friendly compared with any other methods of production of biodiesel with less processes time. Since the washing of biodiesel to remove the soap formed due to the presence of free fatty acid content in the feedstock is completely eliminated, there will be no effluent discharge to the environment and at the same time resulting in more yield. The significance of this method is that it can be used to obtain biodiesel from used vegetable oils, raw vegetable oil and tallows and especially for any feedstock material which contains any amount of free fatty acids.