CHAPTER 3
METHODOLOGY

3.1 Introduction

The most common way to produce Biodiesel is via Batch Trans-esterification which refers to a catalyzed chemical reaction involving vegetable oil and an alcohol to yield fatty acid alkyl esters (i.e., biodiesel) and glycerol.

Trans-esterification of triglyceride with alcohol to form biodiesel.

3.2 Raw Material

2.1. Chemicals
Methanol (99-100%), ethanol (99-100%), sodium hydroxide pellets (96%), potassium hydroxide pellets (>84%), phenolphthalein (PH 8.2-9.8), acetone (99%), diethyl ether , hydrochloric acid (37%), iodine , sodium iodide, bromine, carbon tetrachloride, glacial acetic acid, potassium dichromate etc. All the chemicals were used as analytical reagent grade.
2.2. Raw Materials
Waste cook oil (palm oil and soybean oil) was collected from local restaurants located in Sylhet city in Bangladesh. The oil was filtered and its properties were measured.
2.3. Preparation of Biodiesel by Three-step Method
Three-step method consists of Saponification followed by acidification to produce FFA and finally esterification of FFA to produce biodiesel [12].

2.3.1. Saponification
For saponification process required amount of WCO was taken in a three necked flask and mixed with different stoichiometric amount of aqueous sodium hydroxide solution. The mixture was heated under reflux with vigorous stirring at temperature of 100°C for different time. The reaction was stopped by cooling the reaction volume. Aqueous sodium hydroxide solution was prepared by dissolving required amount of dry sodium hydroxide (NaOH) in 60-90ml water. The reaction time and different molar ratio of oil to sodium hydroxide solution through saponification process were optimized.

2.3.2. Acidification
After saponification, produced sodium soap solution was treated with different stoichiometric amount of concentrated hydrochloric acid at a temperature of 65-70°C under reflux with vigorous stirring. After dissolving the soap, the fatty acid contents were separated in separatory funnel. After separation, hot water wash was given for removing mineral acid from the fatty acid. The FFA content was determined by titration method. The different molar ratio of soap to hydrochloric acid was given and the ratio was optimized.

2.3.3. Esterification of Free fatty acid (FFA)
When acidification was completed, produced FFA was reacted with different stoichiometric amount of methanol under reflux with vigorous stirring at different temperature, catalyst concentration, different molar ratio of methanol to FFA and different time. All the reaction parameters were optimized. Silica gel was used during esterification reaction to adsorb water produced in esterification reaction.
After preparing the biodiesel from WCO various physico-chemical properties were measured and compared with the standard biodiesel. The yield of biodiesel was calculated by the following equation: | (1) | where, W(biodiesel) is the weight of produced biodiesel and W(oil) is weight of oil.