Preparation Of Biodiesel Catalyzed By Solid Base

Biodiesel produced is a new-renewable and promising alternative fuel to diesel regarding to limited resources fossil fuel and the environmental concerns. For developing an environmentally benign process and reduction of the production cost, the preparation of heterogeneous solid base catalyst was studied, and the transesterification of rapeseed oil and methanol were investigated catalyzed by solid base.Firstly, the analytical procedures of material and the biodiesel products were developed. GC-MS was used to identify the compositions of fatty acid in material and the composition of fatty acid methyl ester in product. The results showed that the main composition of fatty acid in the material included oleic acid, linoleic acid, linolenic acid, erucic acid and cis-11-eicosenoic. The main compositions of products were methyl ester of the fatty acids. HPLC was used to quantitative analysis the fatty acid methyl ester in product.Secondly, various solid base catalysts were developed by impregnation method, in which KOH/γ-Al2O3 was chosen as the target catalyst. The preparation conditions of the catalyst were investigated and optimized as follows: the loading amount of KOH is 45g/100g(carrier), the calcinations temperature is up to 500℃, and the granularity of carrier is between 140-160 mesh.BET, XRD and IR were separately used to analysis the solid base KOH/γ-Al2O3. The results showed its specific surface area was 3.889m2/g, pore size was 243.0nm and there existed a new substance of KAlO2, which is considered to be the active point of the catalyst.The solid base KOH/γ-Al2O3 prepared under the optimal preparation conditions was used to catalyze the transesterification of rapeseed oil and methanol. The transesterification conditions were optimized by orthogonal test. The optimal transesterification conditions were developed as follows: methanol/oil molar ratio 15:1, amount of catalyst 2.5wt%, reaction temperature 65℃, reaction time 6h. The results showed that the highest yield of methyl ester was up to 96.49%. Finally, the influences of acid value and water content in material on yield of methyl ester of transesterification catalyzed by KOH/γ-Al2O3 were investigated. The experimental results showed that the influences of acid value and water content in material on the active of KOH/γ-Al2O3 were much small compared to the conventional KOH catalyst.Compared with the literature reported catalyst of alkali compound, the activity of KOH/γ-Al2O3 towards transesterification is higher and the preparation method is simpler. The material of KOH is also inexpensive. The use of solid base catalyzed transesterification can not only make the separation process easier after the reaction,but also reduce waste water pollution. Therefore, the use solid base of KOH/γ-Al2O3 will be benefit to develop an environmentally benign process for preparing biodiesel.