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Research on Preparation of Biodiesel from Soapstock Biodiesel is fatty acid methyl ester. Its properties are similar to ordinary diesel and can be used as a good substitute for ordinary diesel. It is generally produced by transesterification of vegetable oil or animal oil, and can also be produced by esterification of fatty acids. Biodiesel has the advantages of being renewable, easily biodegradable, non-toxic, low in sulfur content and low in harmful emissions in exhaust gas, making it an environmentally friendly fuel⋯1. The demand for diesel will increase in the future. With the increasing depletion of petroleum resources and the improvement of people's environmental awareness, the development of environmentally friendly diesel alternative fuels has greatly accelerated in various countries around the world. Especially since the 1990s, biodiesel has attracted the attention of various countries for its superior environmental performance. At present, the main problem affecting the widespread application of biodiesel is cost. Biodiesel is produced through transesterification reaction using vegetable oil or animal oil as raw materials. Although biodiesel with better quality can be obtained, it is currently difficult to promote and apply it in our country. my country's vegetable oil soap stock production is huge. In the past, soap stock was only used as acidified oil and low-grade soap, or even discarded, resulting in waste. Using vegetable oil soap stock as raw material to prepare biodiesel can make full use of soap stock and turn waste into treasure. * * Reduce the production cost of biodiesel and promote the popularization and application of biodiesel. 1 Materials and methods 1.1 Raw materials and reagents Cottonseed oil soap stock was provided by an oil factory in Weishi County, Henan Province. All reagents used in the experiment were of analytical grade. 1.2 Experimental instrument 101-2B type electric heating constant temperature blast drying oven ； S. C. Type 101 blast electric heating constant temperature drying oven ； Analytical balance (sensitive to 0.0001 g) ； BS201 electronic analytical balance (sensitivity 0.0001 g) ； HH-S series electronic constant temperature water bath (4 holes) ； Type 800 low-speed centrifuge. 1.3 Experimental Methods Received Issue 13-'2005-l1-o8 Author Introduction: Ma Chuanguo (1966), male, associate professor ； Mainly engaged in teaching and scientific research on oleochemistry and oil technology. 1.3.1 Pretreatment of soap stock: soap stock - additional saponification - acidolysis - washing - drying - fatty acid centrifugation to remove solid impurities. The saponification reaction and acidolysis reaction are carried out in a 500 mL three-necked flask. The flask is connected to a reflux condenser and heated and stirred with an electric heating mantle. The determination of saponification value and acid value are carried out according to GB/T 5534-1995 and GB/T 5530-1985 respectively [2_ 2. 1.3.2 Preparation of fatty acid methyl ester. Add a certain proportion of fatty acid and methanol into a three-necked flask, then add a certain amount of concentrated sulfuric acid as a catalyst, connect the reflux device, and heat to reflux in an electric heating mantle. After the reaction is completed, cool down, pour the reaction mixture into a separatory funnel for separation, and take the upper methyl ester solution and wash it with distilled water until neutral. Then it was dried with anhydrous sodium sulfate and filtered to obtain a yellow, clear and transparent product. 1.3.3 Determination of esterification rate: Take samples to analyze the acid value of the reactants, and calculate the esterification rate l3 of the system based on the change in acid value before and after the reaction.] . Ester%) = x 100 2 Results and discussion 2.1 Single factor experiment 2.1.1 Effect of reaction temperature on esterification rate When the ratio of methanol to fatty acid is 1: 1 (V/W), time of 60 inln, and 0.1% sulfuric acid as a catalyst under fixed conditions, the experimental results of the fatty acid esterification rate changing with temperature are shown in Figure 1. One Palm One Synergy Temperature ( ) Figure 1 Effect of reaction temperature on esterification rate VIP Information http://www.cqvip.com China Oils and Fats 2006 Volume 3l Issue 4 As can be seen from Figure 1, as the temperature increases, the esterification rate of fatty acid methyl esterification continues to increase. When 60cc, the esterification rate reaches the maximum ； Subsequently, as the temperature increased, the esterification rate slowly decreased. If the reaction temperature is higher than the boiling point of methanol, the volatilization and leakage of methanol will inevitably increase, and the methanol participating in the reaction will decrease. At the same time, considering the energy consumption issue, the temperature of fatty acid methyl esterification should not be too high, and the selected temperature should be around 60cc. 2.1.2 Effect of reaction time on esterification rate Reaction time is one of the important factors affecting the reaction. The reaction temperature is 60cIC, and the ratio of methanol to fatty acid is 1: 1(V/IV), when 0.1% sulfuric acid is used as the catalyst, the esterification effect at different times is shown in Figure 2. 一{jlL{ ； Wangshi Iming (rain) Figure 2 Effect of reaction time on esterification rate As can be seen from Figure 2, the esterification rate of fatty acids increases with time, but after the reaction time exceeds 90 min, the esterification rate increases slowly and remains basically unchanged. Extending the time too long will cause more solvent consumption, waste of energy and decrease in production efficiency. After methyl esterification for 60 minutes, the esterification rate of fatty acids can reach 98%, so the esterification time can be controlled at about 60 minutes during the experiment. 2.1.2 Effect of the ratio of methanol to fatty acids on the esterification rate. Under the conditions of a reaction time of 60 min, a reaction temperature of 60°C, and 0.1% sulfuric acid as the catalyst, the relationship between different ratios of methanol to fatty acids (V/W) and the esterification rate is shown in Figure 3. 11 by {L Jiang alcohol ship ratio ( , J Figure 3 The effect of the ratio of methanol to fatty acids on the esterification rate. It can be seen from Figure 3 that the amount of methanol has a greater impact on the esterification rate of fatty acids. If the amount of methanol is too small, the reaction speed is slow and incomplete, resulting in a low esterification rate of fatty acids. ； When methanol is excessive, the esterification rate does not increase significantly. When the ratio of methanol to fatty acids is 1: When 1 (V/W), the esterification rate can reach 97.8%. If methanol is excessive, the esterification rate will increase slowly and remain basically unchanged. Considering the methyl esterification effect, recovery and methanol consumption, the ratio of methanol to fatty acids should be selected as 1: l(v/w). 2.2 Orthogonal experiment Based on the above single-factor experimental results, the three factors of reaction temperature, reaction time, and the ratio of methanol and fatty acids were selected to conduct a 3-factor and 3-level orthogonal experiment. The experimental design is shown in Table 1, and the experimental results and range analysis are shown in Table 2. Table 1 Orthogonal experiment factor level package 2 The results of the orthogonal experiment can be seen from Table 2. Among the three reaction factors, the most influential factor on the esterification rate is the alkyd-to-acid ratio, followed by the reaction temperature, and finally the reaction time. ； The best reaction conditions are: The reaction temperature is 60cc, the reaction time is 60 minutes, and the ratio of methanol to fatty acid is 1.4: 1(/). The experimental conditions with the highest fatty acid esterification rate obtained from the single factor experiment are: The reaction temperature is 60°C, the reaction time is 60 min, and the ratio of methanol to fatty acid is 1: 1(/). If the two are not consistent, do a verification experiment to verify it. The results are shown in Table 3. Decay 3 Verification experiment results can be seen from Table 3. The conversion rate of fatty acid methyl esterification under both conditions is around 98%. However, considering the utilization rate of raw materials, the consumption of methanol and the energy consumption in the recycling process, the greater the proportion of alkyd acid. VIP Information http://www.cqvip.com 20O6 Volume 31 Issue 4 China Oils and Fats 61 The more methanol that needs to be recycled, the more methanol consumption will increase and the energy consumption will also increase. Therefore, the optimal conditions for fatty acid methyl esterification can be determined as: The reaction temperature is 6o°C, the reaction time is 60 minutes, and the ratio of methanol to fatty acid is 1: 1( ). 3 Conclusion The preferred experimental method during the experiment is: The soap stock is converted into acidified oil (a mixture of fatty acids and neutral oil) through concentrated sulfuric acid, and then decolorized and centrifuged to remove impurities, and finally methyl esterified. During the experiment, 0.1% sulfuric acid was used as the catalyst, and the ratio of methanol to fatty acids was controlled at 1: 1(), the reaction temperature is controlled at 6o°C, the reaction time is 60 minutes, and the esterification rate can reach 97.8% under these conditions.