New Catalyst For The Preparation Of Biodiesel And Kinetic Studies

As a kind of cleaning liquids fuel, biodiesel is made from vegetable oils and animal fats, and it is an excellent substitute of fuel. Biodiesel was prepared through transesterification using alkali as catalyst in industrial production. Raw materials may contain little amounts of free fatty acids and moisture, but these catalysts will lead to the production of more fat soap which effected the separation between biodiesel and glycerol and thus reduce the yield of biodiesel. Our group discovered a new biodiesel catalyst, SXL, which had solved the above problems. In this paper, the experimental and pilot-test conditions were optimized by using the crude rapeseed oil as raw material, and capability of the SXL for biodiesel made from animal fats was also studied. The kinetics of the transesterification under SXL was also analysed. The contents in this paper were as follows:The researches on types of biodiesel catalysts, kinetic studies and preparation of biodiesel from animal oil were summarized.Firstly, at a small scale, the reaction were that when the amount of oil was 100g, alcohol-oil ratio was 5:1～8:1, the amount of catalyst was 0.5%～4.0% of material oil, reaction time was 1～3h, and temperature was 40～60℃, the conversion rate and yield reached more than 98%. At a middle scale with 20-liter reactor, when the feedstock input was 6.5kg, alcohol-oil ratio was 5:1～8:1, the amount of catalyst was 0.5%～5.0% of material oil, reaction time was 1～3h, and temperature was 40～60℃, the conversion rate, yield of biodiesel and the amount of glycerol reached more than 95%.Secondly, the preparation of biodiesel using lard as raw material was also studied. The optimal reaction conditions were that when the alcohol-oil ratio was 10:1～16:1, and the amount of catalyst was 0.5%～3.0% of lard, reaction time was 30～80min, and temperature was 40～60℃, the conversion rate and yield reached more than 98%.Structural characterization of biodiesel: the biodiesel respectively made from crude rapeseed oil and lard were analyzed by GC-MS, and the result showed that biodiesels were both mainly composed of the fatty acid methyl esters. The biodiesel made from crude rapeseed oil were oil methyl ester and linoleic acid methyl ester; the one made from lard were of oil methyl ester, palmitic acid methyl ester and stearic acid methyl ester.Thirdly, the kinetics of transesterification catalysed by catalyst SXL was investigated by using the refined rapeseed oil and methanol as raw materials. In the range of 40～60℃, reaction rate increased; when the amount of catalyst was 2.2% , the reaction had a result with faster rate and higher yield; when alcohol-oil ratio was 16:1, higher production rate could be reached in a relatively short time. The transesterification under the role of SXL was a transformation process from second-order to zero-order, and the average activation energy of reaction was 35.33kJ/mol, frequency factor k₀ was 4.73×10⁵L/(mol·min).