Manufacturing of Biodiesel from Mahua (Madhuca Indica) Oil

Abstract

In recent years, increased environmental awareness and energy shortages have encouraged researchers to investigate the possibility of using alternate fuels which are environment friendly and renewable such as vegetable oils or animal fats instead of fossil fuels. Vegetable oils have considerable potential to be considered as appropriate alternative as they possess fuel properties similar to that of diesel oil. The major problem associated with direct use of vegetable oil is their high viscosity and gum content. One possible method to overcome the problem of high viscosity is the transesterification of potential vegetable oils to produce biodiesel (esters) of respective oils. This interest is because biodiesel is biodegradable, sulphur free, oxygenated and renewable alternative diesel fuel derived from vegetable oils or animal fats. In the present investigation, Mahua oil ester (biodiesel) was prepared from non-edible feedstock of Mahua raw oil. Raw Mahua oil as obtained from the market has very high value of FFA (free fatty acid) i.e. around 19%. Different samples of Mahua oil biodiesel were obtained through Transesterification process using Potassium Hydroxide (KOH) as a base catalyst, Sodium Hydroxide (NaOH) as a base catalyst and through a Two-Step Esterification & Transesterification process using Sulphuric Acid (H₂SO₄) and Potassium Hydroxide (KOH) as acid-base catalyst. Among the above three different methods/process, the process which reduces the FFA level to minimum was selected for further characterization and comparison of fuel properties were made for further use in C.I. Engines. In the investigation it was observed that the Two-Step Process of Esterification & Transesterification reduces the FFA level to 0.40% which was the least among other processes of transesterification which was having FFA level of 2.04% (using KOH) and 1.44% (using NaOH) respectively. The optimum process for reducing the FFA level to less than 1% was carried out with 0.33 v/v (methanol/Mahua oil) ratios and with 1.30% v/v (H₂SO₄/Mahua oil) ratios for acid catalyst in the first step. The above mixture of methanol and acid was mixed with preheated Mahua oil for about 1.30 h’s reaction time and at 60 °C. After completion of the first step i.e. esterification process, the mixture was allowed to settle for 1–2 h. Methanol water and biodiesel layers were formed at the top and bottom respectively and the top layer of methanol water was removed. The bottom layer was collected and the second step i.e. Transesterification was carried out with 0.25 v/v (methanol/Mahua oil) ratio and 0.75% w/v KOH as base catalyst for 1 h at 60 °C. The produced mixture was kept for settling for about 24 h and after removing glycerol from the separated layers, pure biodiesel with 98.4% yield was obtained which was washed and dried later to get pure and clean biodiesel that was found to have properties comparable to Diesel.