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Enzymatic Transesterification for Biodiesel Production from Chinese Kernel Oil

Author: ZouXiaoXia
Tutor: ZuoYunJun；XuLi
School: Huazhong University of Science and Technology
Course: Biochemistry and Molecular Biology
Keywords: Chinese kernel oil Biodiesel Organic solvent reaction medium Compound lipases Synergistic effect
CLC: TE667
Type: Master's thesis
Year: 2009
Downloads: 56
Quote: 0
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Abstract

As a green and renewable fuel, biodiesel has attracted more and more attention. With the development of non-aqueous ezymology and its relating technology, and using lipase to catalyze fat and oil to produce biodiesel is becoming one of the hot spots in the field of bioenergy in recent years. However, the expensive lipase and the lacking of oil feedstock both obstruct the industializtion of enzymatically catalyzing technique on a large scale.Chinese tallow kernel is one of the endemic oil plants in China. Its oil ranks top four of all woody oil plants. Although Chinese kernel oil is not edible, it’s composed of 92% non-saturated fatty acids, making it a good feedstock for biodiesel preparation. In this paper, based on the previous study in our laboratory, the technique to prepare biodiesel catalyzed by compound lipases (Novozym 435 and Lipozyme TLIM) with Chinese kernel oil as a substrate was investigated. The main results were listed as follows:(1) First, the organic solvent systems were sieved. The results showed that tert-butanol was the best organic solvent, in which the biodiesel yield was above 90% using Novozym 435 as the catalyst and Chinese kernel oil as the substrate.(2) In the tert-butanol system, the transesterification conditions were optimized with methanol as acyl acceptor and immobilized lipase Novozym 435 as the catalyst to produce biodiesel. Based on the results of single factorial experiments, response surface method was applied to further optimize the reaction conditions. The results showed that the optimum reaction conditions were loading amount of Novozym 435/oil (wt/wt) 3%, molar ratio of methanol/oil 4.77:1, volume ration of tert-butanol/oil 38.7%(v/v), reaction temperature 40°C, and molecular sleves 11.9% (wt/wt), in which conditions, the conversion rate of biodiesel was up to 97.69%. Washed by hexane, tert-butanol and acetone after each batch, the lipase was repeatedly used for 10 times, the methyl esters yield was still above 90%, which indicates that the above organic solvents could significantly reduce the negative effects on the activity and the stability of lipase from methanol and the by-product glycerol commonly existing in traditional techniques.(3) The transesterification conditions were optimized in the tert-butanol system catalyzed by compound immobilized lipases Novozym 435 and Lipozyme TLIM with Chinese kernel oil to produce biodiesel. Based on the results from single factorial experiments, response surface method was applied to deter mine the optimum reaction conditions. The optimal conditions were 4.2%(wt/wt) total enzyme loading (1.8% Novozym 435 and 2.4% Lipozyme TLIM), reaction temperature 40°C, methanol/oil molar ratio 5.05:1, tert-butanol/oil volume ratio 41%(v/v), molecular sleves 5.5%(wt/wt). Under theoptimal conditions, the biodiesel yield was up to 98.72%, much higher in biodiesel yield and lower in the cost than those of single lipase. Washed by hexane, tert-butanol and acetone after each batch, the lipases were repeatedly used for 10 cycles with no obvious loss of lipase activity. This suggests that the lipase can keep good operational stability under the technique.

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