Question

Explain production of biodiesel from Jatropha seeds.

Answer 1

Source of jatropha Oil: The plant that is generally cultivated for the purpose of extracting jatropha oil is Jatropha curcas. The seeds are the primary source from which the oil is extracted. Owing to the toxicity of jatropha seeds, they are not used by humans. The major goal of jatropha cultivation, therefore, is performed for the sake of extracting jatropha oil. Analysis of jatropha curcus seed shows the following chemical compositions. Moisture: 6.20% Protein: 18.00% Fat: 38.00% Carbohydrates: 17.00% Fiber: 15.50% Ash: 5.30% The oil content is 25-30% in the seed. The oil contains 21% saturated fatty acids and 79% unsaturated fatty acids. These are some of the chemical elements in the seed, cursin, which is poisonous and render the oil not appropriate for human consumption. Oil has very high saponification value and being extensively used for making soap in some countries. Also oil is used as an illuminant in lamps as it burns without emitting smoke. It is also used as fuel in place of, or along with kerosene stoves. Jatropha curcus oil cake is rich in Nitrogen, Phosphorous and Potassium and can be used as organic manure.

Production of Biodiesel

Process Biodiesel is produced by chemically reacting vegetable oil/ animal fat with alcohol to produce a new compound called fatty acid alkyl ester by trans-esterification. A catalyst such as sodium/potassium hydroxide is used and glycerol is obtained as by-product. Methanol is recovered in the process. The main trans-esterification reaction using methanol is carried out in stainless steel reaction tank. The required amount of jatropha oil was filtered, measured and poured into the conical bottomed reactor tank. Jatropha oil was heated to the required temperature and the alkoxide solution (NaOH/kOH) was prepared simultaneously. The prepared alkoxide solution was introduced into the reactor and the mixture was stirred vigorously for required reaction time. After that, the reaction was stopped and the mixture was allowed to settle in the separation tank for 12 hours. After settling the mixture for 12 hours, it was separated into two layers. The lower glycerine layer was drawn off from the bottom of the settling tank. Then, the crude biodiesel was pumped into the washing tank. It was equipped with a stirrer. The crude biodiesel layer was needed to purify by washing with warm water. First, the catalyst residue in the biodiesel layer was neutralized by adding phosphoric acid. After neutralization process, the washing process of biodiesel was started. During the washing process, gentle agitation is required to avoid the emulsion. The wash water layer was drained off from the bottom of the washing tank. The washing process was repeated two to four times. After the washing process, it was required to measure the pH of the biodiesel layer. When the pH of the biodiesel layer reached 7, the washing process was completed. After that, the biodiesel layer was sent to the sand filtration tank. After filtration, biodiesel was obtained as a clear amber-yellow liquid with a viscosity similar to that of petrodiesel.