การผลิตเอทิลเอสเตอร์เชิงอุตสาหกรรมจากน้ำมันปาล์มดิบ

Abstract

This research aimed to study the optimum conditions of commercial ethyl ester production from crude palm oil (CPO) in a pilot scale plant of 500 litre biodiesel/day capacity which including esterification, transesterification, ethanol recovery and resin co-washing processes, all of the units were carried out continuously. in this study. CPO containing free fatty acid (FFA) of 4.43-8.32wt% and commercial grade of ethanol (99.9%V purity) were used as reactants, sulfuric acid (98wt%) and potassium methoxide (32 wt% in methanol) were used as esterified and transesterified catalysts, respectively. Continuous stirred tank reactor for esterification step was 87.4 litres in volume and continuous deglycerolization reactor of 16 litres was used in transesterification step. High pressure at 30 bars and temperature of 220 ํC were carried out with a flash tank of 250 litres. Washing equipment contain 2 tanks of resin adsorption. 1 tank of water washing and 1 tank of salt filter tank, all of thern were 55 litres in volume. It was found that the estentication step with sulfuric acid catalyst could decrease phosphorous content from 11. 24-21.70 mg/kg of crude paim oil to 1.01 -1.46 mg/kg of esteritied palm oil, certainly met the Thai Nation Standard of Methy! Ester which is below 10.0 mg/kg biodiese!. Optimnized continuous esterication step was carried out at 1 hour of retention time, 60 ํC, molar ratio of ethanol to FFA at 30: 1 and suifuric catalyst of 60 wt% of FFA resulted in 0.81 wt% FFA of esterified paim oil. It could be seen that the cause of no phase separation of glycerol in ethyl ester came from the micells formation in the existing of high soap content. This obstacle was solved by lowering water content in the system, potassium methoxide was used as a catalyst and glycerol phase was continuous separated out by using the continuous deglycerolization reactor. The best condition of our trial was at 25 minute of retention time, 66 ํc, molar ratio of ethanol to triglycerige at 5.7: 1 and molar ratio of methoxide to triglyceride of 0.2: 1 resulted in higher than 98% of ethyl ester content in the produced biodiesel. However, the obtained acid value of biodiesel was about 0.6 mg KOH/g higher than the standard value of 0.5 mg KOH/g which came from the fast reaction rate of hydrolysis reaction of water and ester in matrix of ethanol. The soap content in ester phase was very high of nearly 30,000 ppm resulted in a difficulty of washing step and higher loss of biodiesel yield. Also a lower yield of production (90%) which gave a higher production cost, anyhow these problems should be solved in the further studied. According economical study of the ethyl ester production, cost of CPO and ethanol were 26 and 20 baht/kg, respectively. It yielded 34 baht/litre of ethyl ester.