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Research on the preparation of biodiesel from rapeseed oil with methyl acetate. Biodiesel (the main component is fatty acid methyl ester) is a kind of fuel produced with animal and vegetable oils and fats (vegetable oil is currently used more often) as the main raw material, and its properties are very similar to ordinary diesel. Traditionally in industry, strong acids or strong bases are used to catalyze the transesterification reaction of vegetable oil and methanol to obtain fatty acid methyl esters and glycerol. This method has shortcomings such as high energy consumption, high pollution, and difficulty in separating the saponified products and glycerol in the product¨-3] , Therefore, the use of environmentally friendly and mild reaction conditions bioenzymatic methods to prepare biodiesel has attracted increasing attention. A large number of studies have confirmed that the reactant methanol and the by-product glycerol have a great negative impact on lipase activity l41j. This research group developed the use of methyl acetate instead of methanol as the acyl acceptor in the transesterification reaction to obtain biodiesel and the by-product triacetin Es-10] technology, which relieves the inhibitory effects of methanol and glycerol and improves the stability of the enzyme * * Improvement, the activity of the immobilized enzyme did not decrease significantly after continuous reuse for 200 batches. At the same time, studies have shown that phospholipids can inhibit the activity of lipase l1. When the phospholipid content in vegetable oil exceeds 0.2%, it will cause obvious and irreversible inhibition of the commonly used lipase Novozym 435. The vegetable crude oil currently on the market is not suitable to be directly used as a raw material for continuous reactions due to its high phospholipid content. It needs to be degummed to remove most of the phospholipids before it can be used in the reaction. Phospholipids are difficult to dissolve in methyl acetate. By using methyl acetate instead of existing solvents to extract vegetable oil from oil plants, crude oil with low phospholipid content can be obtained and directly used as reaction raw materials. Moreover, the extracted crude oil can be directly reacted with methyl acetate to prepare biodiesel without complete desolvation. * * The energy consumption and solvent loss in the desolvation process in the extraction method are reduced. first author: Master student (Professor Andy Lau is the corresponding author) * 863 Program Bioengineering Technology Theme Funding Project in the Field of Biology and Modern Agricultural Technology (No. 2003AA2146061) - "Research on Key Technologies and Countermeasures of Biodiesel" Received Date: 2005-12-05 This article studied the extraction of vegetable oil from rapeseed using methyl acetate. An orthogonal experiment was used to discuss the effects of solvent dosage, oil extraction time, and temperature on the oil extraction rate and phospholipid content in the extracted crude oil, and compared it with the traditional extraction agent n-hexane. Finally, the extraction of crude oil with methyl acetate and the preparation of biodiesel through the reaction of methyl acetate were studied. 1 Materials and methods 1.1 Experimental materials Rapeseed, refined rapeseed oil, and commercially available crude rapeseed oil were purchased locally. ； Lipase novozym 435 (Novozymes) ； Methyl palmitate, methyl heptadecanoate, methyl oleate, methyl linoleate, methyl linolenate, and methyl erucate are chromatographically pure ； Other chemical reagents were of analytical grade. Solution preparation: 0.5 mol/1． NaOH, 0.5 mol/1. HCL, 1 gg/mL KH2PO4 standard solution, 0.1% turquoise green solution, 12% ammonium molybdate solution, 5 mol/L H2SO4, 0.5% polyvinyl alcohol. 1.2 Extraction of rapeseed oil with methyl acetate: Crush the dried rapeseed with a grinder, weigh 100 g of rapeseed powder, add a certain amount of methyl acetate, soak it on a 110r/min shaker at a certain temperature for a certain period of time, filter out the mixed oil (a mixture of oil and solvent), evaporate the solvent to dryness through rotary evaporation to obtain crude rapeseed oil, and recover the solvent. The orthogonal test method was adopted, and the experimental factor table (Table 1) was designed and arranged according to (3), with oil extraction rate and phospholipid content as the inspection indicators. Oil extraction rate = extracted oil amount / (rapeseed mass × 35%) Table 1 Orthogonal test factor table http://www.cqvip.com 1.3 Analysis method 1.3.1 Determination of phospholipid content ll Introduction (1) Preparation of standard curve of phospholipid content: Take phosphorus standard solutions 1, 2, 3, 4, and 5 mL into 25 mL volumetric flasks, add 5 mol/L H2S()4 to each 5 mL, malachite green-ammonium molybdate mixture (volume ratio 2.5: 3)5 mI,O. 5% polyvinyl alcohol solution 1.0 mL, dilute to volume with water, shake well, place in boiling water bath and heat for 5 minutes, take out, cool with cold water, use reagent blank as reference solution, 635 nITI. 1 cITI cuvette to measure the absorbance. (2) Determination of sample phospholipid content Weigh about 2g of the sample into a crucible (accurate to 0.001 g), carefully carbonize it on an electric furnace, then transfer it to a muffle furnace at 600-660C and burn it for 4 hours until it is completely ashed. Remove the crucible and cool to room temperature. Use hydrochloric acid (1: 1) Dissolve the ash in 1O mL and heat to a gentle boil for 5 minutes. Filter the solution and pour it into a 100 mL volumetric flask. Rinse the crucible and filter paper with hot water. After the filtrate cools to room temperature, dilute to volume with water and shake well. Take 2 mL of the above sample solution and measure the phosphorus content in the sample according to the method in the standard curve preparation, and prepare a blank solution at the same time. 1.3.2 Determination of saponification value of oils and fats GB/T 5534-1995. 1.3.3 Determination of acid value of oils and fats GB/T 553O-1998. 1.3.4 The water content is measured using a Karl Fischer moisture meter. 2 Experimental results and discussion 2.1 Orthogonal experiment results and analysis In order to examine the effects of solvent dosage, oil extraction time, and oil extraction temperature on the oil extraction rate of methyl acetate and the phospholipid content in the extracted crude oil, an orthogonal experiment was designed according to (3). The results are shown in Table 2. Table 2 Orthogonal experiment results Test number Factor level Solvent amount Oil extraction time Oil extraction temperature Oil extraction rate Phospholipid content/%/% 27.07 33.72 40.29 48.24 49.29 42 38 54.40 48. O9 53.42 0.060 0.067 O. 192 0. O9l 0.148 0.047 O. 157 0.038 0 ()78 For the experimental results in Table 2, range analysis was performed on the oil extraction rate and phospholipid content. The results are shown in Table 3 and Table 4 respectively. 6 I 2 — 006 Vo1．32 No —． 5(Total 22f1) Table 3 Analysis of oil extraction rate results % As can be seen from Table 3, the greater the amount of solvent, the higher the oil extraction rate. ； The longer the oil extraction time, the higher the oil extraction rate ； The higher the oil extraction temperature, the higher the oil extraction rate. Under the experimental conditions designed in this article, the amount of solvent is 6 times the mass of rapeseed powder, the oil extraction time is 2 h, and the oil extraction rate is the highest when the oil extraction temperature is 40°C. The oil extraction experiment was repeated under these conditions, and the oil extraction rate reached 55.6%, which was higher than the oil extraction rates of the nine experiments in the orthogonal design. This is also consistent with the results of the orthogonal experimental analysis. Further analysis of the experimental data shows that the amount of solvent has the greatest impact on the oil extraction rate, while the oil extraction time has the least impact on the oil extraction rate. When the oil extraction temperature reaches above 30°C, the temperature has a small effect on the oil extraction rate. Table 4 Analysis of phospholipid content results % Phospholipids are poorly soluble in methyl acetate, but the solubility of phospholipids increases in the ternary system of phospholipids, oil, and methyl acetate. According to the analysis results in Table 4, it can be seen that temperature has the most prominent impact on the phospholipid content in the extracted crude oil. The lower the temperature, the lower the phospholipid content in the crude oil. When the temperature rises, the dissolved phospholipids in the crude oil are extracted * * improve. The solvent dosage and oil extraction time have little impact on the phospholipid content. Under the experimental level designed in Table 1, the amount of solvent is 6 times the mass of rapeseed powder, the oil extraction time is 1 hour, and the oil extraction temperature is 20°C, the lowest phospholipid content is 0.038%. Based on the above results, considering the two aspects of oil extraction rate and phospholipid content, the selected oil extraction conditions are:: The amount of solvent is 6 times that of rapeseed powder, the oil extraction time is 2 h, and the oil extraction temperature is 20 * (2. The oil extraction experiment was repeated under these conditions, and the obtained oil extraction rate was 51%, and the phospholipid content was 0.038%. 2.2 Oil properties of crude oil extracted with methyl acetate. Currently, when solvent extraction is used to extract vegetable oil in industry, the solvent used is mainly n-hexane. Under the same extraction conditions, methyl acetate and n-hexane were used as solvents to extract rapeseed crude oil, and compared with commercially available crude oil. http://www.cqvip.com The properties of various oil products were compared, and the results are shown in Table 5. Table 5 Notes on the properties of extracted crude oil and commercially available crude oil: Extraction conditions - The amount of solvent is 6 times that of rapeseed powder, the oil extraction time is 2 h, and the oil extraction temperature is 2O°C. From the results in Table 5, it can be seen that the saponification value and acid value difference of the three oils are all very small. The water content of crude oil extracted by methyl acetate and n-hexane is very close. The phospholipid content of the two extracted crude oils is much lower than that of commercially available crude oil, and the phospholipid content of the crude oil extracted by methyl acetate is the lowest. Because soybean oil was extracted from rapeseed powder in this experiment, phospholipids are easily adsorbed on rapeseed powder, reducing the phospholipid content in the mixed oil. Secondly, at lower temperatures, the solubility of phospholipids in methyl acetate is very low, so the phospholipid content in crude oil extracted with methyl acetate is lower than that in crude oil extracted with n-hexane. From the above conclusion, we can know that as a solvent for extracting rapeseed oil, methyl acetate has the same extraction capacity as the traditional extraction agent n-hexane, but the phospholipid content in rapeseed crude oil extracted with methyl acetate is lower, so it is feasible to use methyl acetate as the extraction agent for rapeseed oil. The phospholipid content in crude oil extracted with methyl acetate is very low (