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At present, **no relevant policies or standards have been established; abroad, favorable policies are in place to support it, and its production cost is 1.5 times higher than that of petrochemical diesel.** It is mainly affected by the prices of raw materials; the best acid value for use as a raw material is below 1. Take rapeseed oil as an example – its price is around 4,000 to 5,000. The price of methanol is also over 4,000 at present, and the price of diesel is around 4,000 to 5,000 as well. The chemical methods used to produce biodiesel require a lot of energy, so it’s not profitable to use them. As for used cooking oil, its raw materials are inexpensive, but it has a high acid value; therefore, it requires acid-catalyzed pre-triesterification, followed by separation, neutralization, and then alkali-catalyzed synthesis – a rather complicated process that demands more stringent requirements in terms of equipment and manufacturing techniques. There are two promising synthetic methods for biodiesel: one is bioenzyme synthesis with low energy consumption, and the other is supercritical synthesis under high temperature and pressure; however, these technologies are not yet mature. So now is not the time for ordinary companies to get involved; if you have the money to invest, that’s another matter – you could handle the whole process from growing oil crops to producing biodiesel. As world oil reserves decline, international crude oil prices keep rising, and energy supply has become a focus of global attention. Petroleum raw materials have a severe impact on the Earth’s ecological environment during use. Given the concern for an environment conducive to sustainable human development, the development of new renewable fuel sources is receiving increasing attention from countries around the world. Biodiesel technology originated during World War II; it boasts excellent environmental benefits and renewable properties. As an alternative energy source, it has a large market potential both domestically and internationally, offering great prospects for further development. 1 International Market Analysis: Biodiesel was invented in Europe in 1988 by the German company Nier; it is produced by refining rapeseed oil. In Europe, the main raw materials used for producing biodiesel are rapeseed and sunflower seeds; in some cases, **used cooking oil and animal fats are also utilized. In terms of usage, different countries place emphasis on different aspects based on their own actual circumstances. In France, biodiesel is primarily used as a lubricity additive for diesel fuel, with 5% biodiesel mixed with diesel to improve its lubricity; only in areas with extremely strict emission regulations is biodiesel used in higher proportions as fuel for diesel engines. Germany uses 100% biodiesel as fuel for buses, taxis, school buses, as well as construction and agricultural machinery. In Italy, 45% of biodiesel is used as heating oil, while the other 45% is used as a lubricity additive in low-sulfur fuels. In Sweden, 80% of biodiesel is used as a pure fuel, while 15% of it is used as a lubricity additive for diesel in concentrations of 2%. Statistical data show that in Europe, biodiesel has been used as a vehicle fuel for over 500 million kilometers, indicating its wide adoption. An overview of the development and application of biodiesel abroad is shown in Table 1. Table 1 Overview of the Development and Application of Biodiesel Abroad ** Raw Material Biodiesel Percentage (%) Current Status United States Soybean B10-B20 In use Germany Rapeseed oil, soybean oil, animal fat B5-B20, B100 Widely used Brazil Castor oil – Under testing Austria Rapeseed oil, used oil B100 Widely used Australia Animal fat B100 Under research and promotion France Various vegetable oils B5-B30 Under research and promotion Italy Various vegetable oils B20-B100 Widely used Sweden Various vegetable oils B2-B100 Widely used Belgium Various vegetable oils B5-B20 Widely used Argentina Soybean B20 Being promoted Canada Turpentine oil, animal fat B2-B100 Being promoted Malaysia Palm oil – Under research and promotion South Korea Rice bran, recycled cooking oil, soybean oil B5-B20 In use Japan Used cooking oil In use According to the Kyoto Protocol, the EU was required to reduce carbon dioxide emissions by 8% between 2008 and 2012. To this end, the EU has issued two new directives to promote the use of biofuels in the automotive fuel market, which will further drive the development of Europe’s biodiesel industry. The EU has introduced new regulations to encourage the development and use of biodiesel, such as exempting biodiesel from value-added tax ； It sets a minimum share of biofuels used in motor vehicles in the total volume of fuel used, raising it from 2% in 2004 to 5.75% by 2010. The introduction of the new regulations caused biodiesel sales to soar from $503.5 million in 2000 to $2.4 billion in 2004. Biodiesel has only begun to gain momentum in the United States in the past two years, and has become the fastest-growing alternative fuel in the country. Biodiesel, as an alternative fuel, has been recognized by three major organizations: the U.S. Department of Energy (DOP), the U.S. Environmental Protection Agency (EPA), and the American Society for Testing and Materials (ASTM). Currently, the United States has several biodiesel producers; for example, NOPEC (also known as Ocean Air Enviromental Fuels and Glycerine Operation) has a designed production capacity of 3,800 × 104 liters. Pacific Biofuels in Hawaii is also quite large in scale. Agua Mansa LLC, a bioenergy company whose main investor is the Southern States Power Company SSPC, produces OXEG brand biodiesel at a rate of 30 million gallons per year ； Western Central Soybean Company began producing its own Soy Power brand diesel in 1996, with a production capacity of 12 million gallons per year. Currently, the production capacity of biodiesel in the United States is between 270,000 and 360,000 tons per year; 1.15 million tons were planned to be produced in 2011, and 3.3 million tons by 2016. The United States also uses biodiesel produced from soybean oil as a raw material to develop degradable, high-value fine chemical products such as lubricants, detergents, and solvents, and an industry has been established in this area. Over 80% of the oil consumed in Brazil must be imported, and the country is also one of the first in the world to master biodiesel technology. In 2002, Brazil restarted its biodiesel program, using its abundant castor oil as a raw material. By 2007, the area dedicated to castor bean cultivation had expanded to 70,000 hectares, and biodiesel production increased to 28.17 million liters. If the B5 biodiesel fuel blending **plan** is implemented, Brazil will need 2 billion liters of biodiesel. Brazil’s Ministry of Mining and Energy predicts that adding 2% biodiesel to diesel could reduce oil imports by $150 million per year. Japan began researching the production of biodiesel from fried oil waste from restaurants in 1995 ； In 1999, an industrial experimental plant was established to produce biodiesel using 259 L/d of frying oil as raw material, thereby reducing the cost of raw materials. Currently, Japan’s capacity to produce biodiesel from used cooking oil has reached 40 ×104 tons per year. Current measures being implemented in Japan to use biodiesel include: 1. Introducing community buses powered by biodiesel ； 2. Some food delivery vehicles use biodiesel as fuel ； 3. Fast-food chains such as McDonald’s and KFC use used cooking oil to produce biodiesel and similar products. 2 Domestic Market Analysis China is a country suffering from a severe shortage of fossil fuels, with very limited resources of coal, oil, and gas. In 2006, China’s imports of crude oil reached 142 million tons. It is predicted that by 2020, China will need to import 500 million tons of crude oil and 100 billion cubic meters of natural gas, accounting for 70% and 50% of the country’s domestic oil and natural gas consumption respectively. The issues related to China’s petroleum resource security and energy security will thus become increasingly prominent, severely affecting economic development and **security; it is necessary to find a fundamental way to ensure energy security. Compared to other countries, China lags far behind in the development of biodiesel; although **no set of policies aimed at supporting, providing incentives for, and encouraging the use of biodiesel has yet been established ； There are also no unified standards for biodiesel nor any strategies for its industrial development. However, with the increasing demand for diesel in our country, and under the dual pressures of rapid economic growth and environmental protection since joining the WTO, it is believed that relevant policies for the biodiesel industry will be introduced in the near future. At present, China’s annual biodiesel production capacity is around 40,000 tons, with production mainly carried out by Fujian Zhuoyue New Energy Company, Sichuan Gushan Oil Chemistry Company, and Hainan Zhenghe Bioenergy Company. The main raw materials used in production are food waste oil or oil pressing residues; the quality of the product is difficult to guarantee, and the supply of these raw materials is also unstable ； Production is primarily carried out using traditional chemical methods, namely through transesterification or hydrolysis-esterification reactions of fats and oils with methanol in the presence of an alkaline catalyst to produce fatty acid methyl esters. These methods suffer from issues such as low conversion rates, high energy consumption and costs, as well as environmental pollution. (1) Hainan Zhenghe Bioenergy Co., Ltd. built China’s first biodiesel production facility in Wu’an City, Hebei Province, in September 2001; using kitchen waste oil, oil pressing residues, and oils from forest fruits as raw materials, it produces 10,000 tons of biodiesel per year. According to tests conducted by the Petroleum and Chemical Science Research Institute, the product quality exceeds the standards for **light diesel, and it meets the American biodiesel standards. The production process is clean and safe, and the product possesses market competitiveness without the need for any **subsidies. At present, Hainan Zhenghe Bioenergy Co., Ltd. has also developed 110,000 mu of Chinese ash planting bases in Hebei, which can produce 20,000 to 30,000 tons of fruit per year, yielding 8,000 to 12,000 tons of biodiesel raw materials. The company plans to build a refinery on this basis, capable of producing 50,000 to 200,000 tons of biodiesel per year. (2) Fujian Longyan Zhuoyue New Energy Development Co., Ltd. invested 12 million yuan in January 2002 to build a biodiesel production facility with an annual output of 2.0×104 tons, which came online in September. By using slightly acidic catalysts and composite alkaline treatment solutions, the product cost can be kept at 2,000 yuan per ton. (3) In 2005, Weihai Bilu Bioenergy Co., Ltd., established solely by the Austrian company BIOLUX, invested 75 million euros to build a bio-refinery with an annual capacity of 250,000 tons in Weihai, Shandong. Production of biodiesel was set to begin by the end of 2006, with all the product being exported to the EU. (4) Jiangxi Jubang Chemical Company imports genetically modified soybean oil from the United States and domestic rapeseed oil to produce biodiesel, and is currently building a production facility with an annual capacity of 100,000 tons. An enzyme-based biodiesel production technology has enabled the establishment of pilot-scale production lines with a capacity of hundreds of tons. Cultivation bases for oil-producing energy plants such as Jatropha and Caragana have been set up over 50,000 mu in regions including Sichuan and Hebei, laying the foundation for large-scale development. A comparison of several specific companies is shown in Table 2 below: Table 2 Major domestic manufacturers: Company, designed annual production capacity, main raw materials used, current status of industrialization, production technologies employed, actual applications, and intellectual property status. Hainan Zhenghe Bioenergy Company: 10,000 tons; waste cooking oil, oil extraction residues, etc.; production facilities already in place; chemical method; details unknown; no patents. Fujian Economic and Trade Commission – Zhuoyue New Energy Development Company: 20,000 tons; gutter oil, swill oil; included in Fujian Province’s key technological development projects; chemical method, slightly acidic catalyst technology; biodiesel has been used in heavy trucks, etc.; yes, patent CN02115477.5. Sichuan Gushan Oil Chemical Company: 10,000 tons; waste swill oil; industrialization capabilities already available; seeking partners for cooperation; chemical method; details unknown; patents available. Hunan Tianyuan Bioclean Energy Co., Ltd.: 20,000 tons; oils from woody plants, jatropha oil, waste materials, etc.; a production facility with a capacity of 200,000 tons is under construction; bioenzyme-assisted chemical method; biodiesel has been used in buses, construction vehicles, etc.; **invention patent. Henan Xinghuo Bioenergy Co., Ltd.: 50,000 tons; waste animal and plant oils; included in the “11th Five-Year Plan”; catalytic continuous hydrolysis process, vacuum continuous distillation process, continuous glycerin recovery process, atmospheric pressure continuous esterification process; diesel for vehicles and fuel for boilers; patent number 74647, international patent classification code C10L1/8. In 2002, China’s consumption of diesel for vehicle use was approximately 1,800 ×104 tons, and it is estimated that this figure will reach 6,100 ×104 tons by 2020. If it is added to low-sulfur, low-aroma clean diesel at a rate of w = 2%, to improve its lubricity, the demand for biodiesel would then reach 122 × 104 tons per year. Therefore, production technologies with independent intellectual property rights should be developed as soon as possible, and demonstration bases for biodiesel, along with the glycerol by-product and fine chemical products derived from it, should be established. The following are some websites related to biodiesel in China: http://www.cbbf.cn/forum/ – China Biodiesel Professional Network; http://www.biodiesel.net.cn/bbs/index.asp – Biodiesel Network; Information on Chinese biodiesel patents: CN1382762A. Process: A process for producing biodiesel from waste animal and vegetable oils. 1. Process: Under the presence of an acidic catalyst, various waste animal and vegetable oils with different acid values undergo alcoholysis and esterification reactions ； The excess alcohol is removed to obtain the crude ester ； Then, the excess components that are not part of the product are separated out, such as acids, glycerin, water, etc., to obtain the crude product ； To the crude product, saturated salt water containing 10% soda ash is added to carry out a neutralization reaction, yielding a washed crude ester. Finally, industrial soda ash is added to this washed crude ester and heated for distillation; the fraction with a vapor temperature of 220–320°C is collected to obtain the finished biodiesel. Its ingredients are as follows: 100% used animal and plant oils, 10–20% alcohols (such as methanol or ethanol), 0.7–1.1% acidic catalysts (sulfuric acid or benzene sulfonic acid), 4–6% alkaline salt water, and 0.4–0.8% soda ash. 2. Specific technical approach: Esterification: Take 3000 kg of corn oil that is brownish-black in color with an acid value of AV=152, add 450 kg of industrial methanol with a concentration of 98%, and 27 kg of industrial sulfuric acid with a concentration of 98%. Pump these used oils, methanol, and sulfuric acid into a 5000-liter esterification tank. Turn on the valves for reflux cooling water and hot oil heating, and raise the temperature. After about 1 hour, methanol will begin to reflux; the temperature of the gas phase at this point is 70℃ ； Under conditions of a gas phase temperature of 70–73°C, methanol was refluxed for 5 hours ； Under conditions of a gas phase temperature of 73–85°C, methanol was refluxed for 3 hours and 15 minutes ； At a gas phase temperature of 85–90°C, methanol was used for refluxing for 3 hours; the acid value AV of the material obtained was ≤15. The total reflux time amounted to 11 hours and 15 minutes. A reflux time of more than 10 hours is sufficient, with 10–12 hours being the optimal range, resulting in a qualified crude ester. Close the reflux valve and open the methanol distillation valve to vaporize the remaining methanol; the vaporized methanol is collected at a gas phase temperature of 98°C. After cooling the crude ester in a crude ester condenser, it is pumped into a storage tank; after standing for 12 hours, the lower layer of dilute sulfuric acid and glycerin water is removed. Neutralization: Pump the crude ester into the neutralization tank, and while stirring, add saturated brine containing 6% sodium hydroxide to bring the pH of the crude ester from 2–3 to 7–8. Allow it to stand for 3 hours, then separate out the lower layer of saturated brine. The separated saturated saline solution is reprocessed using alkali tablets to form a saturated sodium hydroxide saline solution, which is then used for the next batch of neutralization. At atmospheric pressure distillation: The neutral crude ester is pumped into the distillation vessel, and 24 kilograms of industrial solid soda ash are added; then the temperature is raised for heating, with the fractions below 220°C being collected separately ； Fractions between 220–320°C and fractions above 330°C. Among them: the fraction below 220°C serves as an miscible solvent for gasoline and methanol, and is pale yellow in color. The fraction between 220–320°C, used as biodiesel, is pale yellow in color. The fraction above 320°C is brown in color and is fed into the next distillation batch. The material balance is as follows: Input, Output. Raw material name, Quantity (kg), Percentage (%). Product and by-product names, Quantity (kg), Percentage (%). Used vegetable oil: 3000, 100; Biodiesel: 2422, 80.73; Industrial methanol: 450, 15; Low-boiling-point methyl ester: 144, 4.8; Industrial sulfuric acid: 27, 0.9; High-boiling-point methyl ester: 285, 9.5; Alkaline salt water: 150, 5; Recycled methanol: 270, 9; Soda ash: 24, 0.8; Recycled salt water: 141, 4.7; Recycled glycerol and dilute acid: 285, 4.8. Total: 3651; Total: 3547. Material loss: 104 kg, accounting for only 2.84% of the input materials. Process CN1473907A: A method for producing biodiesel. 1. Process: Pretreatment stage: After mechanical impurities are removed, the material enters the raw material storage tank; it is then heated and sent to a dehydrator with a vacuum level of –0.08 Mpa to –0.095 Mpa and a temperature of 60°C to 130°C, where it is dehydrated before being used. Esterification stage: The pretreated raw materials are pumped into the reactor, other ingredients are added, and the temperature is raised to 60–80°C. The water generated during the reaction, along with the methanol used as a reactant, enters the recovery tower in gaseous form, where the water is separated out. Pure methanol returns to the reactor to continue the reaction. When the reaction reaches completion, the catalyst is removed, and the excess methanol that did not participate in the reaction is purified and recovered from the methanol recovery tower. The resulting material enters a sedimentation tank; after having a small amount of water removed from it, it goes into a distillation tower where continuous distillation takes place under reduced pressure. The distillate, after being cooled, becomes the finished product, which is then pumped into a storage tank for the finished products. 2. Process features: (1) It adopts a structure in which the esterification reactor is connected to the methanol recovery tower, allowing for the removal of water generated during the reaction at any time. This ensures that the reaction proceeds in the forward direction at all times, resulting in a complete reaction and a high ester conversion rate of over 93% ； Moreover, the reactor can have a capacity of over 20 cubic meters, making it particularly suitable for large-scale industrial production. It is also because of this structure that the excess methanol that did not participate in the reaction can be recovered and purified, thereby significantly reducing methanol consumption ； (2) Continuous vacuum dehydration is employed; the dehydrator features a specially designed plate structure or packing structure, and the vacuum generation is achieved using a water ring pump or a hydraulic jet vacuum pump ； (3) The use of a composite catalyst system not only enables the conversion of fatty acids into methyl esters but also allows the saponification of neutral oils into methyl esters, resulting in high yields of the products ； Since the esterification reaction is a reversible process, once the desired level of esterification is achieved, the catalyst must be removed first before methanol can be recovered; otherwise, the acid value will increase slightly. (4) The distillation of crude methyl ester is carried out by continuous distillation under reduced pressure. The crude methyl ester is preheated to around 230°C in a rising-film preheater, after which it enters the evaporation tower. Heating in this tower is carried out using a falling-film heat exchanger, in order to prevent the material from deteriorating due to excessive heating. The vacuum level should be maintained at 1–6 mmHg; the equipment used for this purpose is a steam-jet vacuum pump, or a combination of a steam pump and a water-ring pump. After steaming, the product must be cooled to below 35°C to ensure its good color. Process CN1412278: A method for producing biodiesel from waste animal and vegetable oils with high acid values. 1. Process: The acidic catalytic method is used; under the action of an acidic catalyst, these oils react with low-carbon alcohols to produce fatty acid methyl esters through processes such as esterification and transesterification. The process includes the following steps: (1) Dehydration: This is carried out under vacuum at temperatures of 60–100°C ； (2) Esterification, transesterification: carried out at 40–85°C, using methanol and sulfuric acid as catalysts, with a reaction time of 1.5–6.0 hours ； The amounts of methanol and sulfuric acid used are 10–15% and 2–6% of the weight of the waste animal and vegetable oils with high acid values, respectively ； (3) Phase separation: carried out at 40–80°C for 0.3–1.0 hour ； (4) Decolorization: This is carried out at temperatures between 90 and 125°C, with 3–10% of activated clay being used for decolorization. Specific steps: Raw material: 30 kg of degraded waste cottonseed oil with high acid value. First, the degraded waste cottonseed oil with high acid value is placed in a dehydrator, where it is dehydrated under vacuum conditions at 70°C ； After dehydration, it is fed into the reaction vessel, where 3.6 kg of methanol and 1.2 kg of sulfuric acid are added; esterification and transesterification reactions take place at 70°C over a period of 3.0 hours ； The product after the reaction is fed into a phase separator, 1.2 kg of activated clay is added, and phase separation is carried out at 60°C for a total of 0.5 hours ； Finally, decolorization was carried out at 105°C for a total of 0.5 hours, resulting in the production of 28.5 kg of fatty acid methyl ester with a yield of 95%. CN1374370A process: A method for producing biodiesel. 1. Process: In an esterification reactor, the raw material oil is mixed with an excess amount of industrial methanol having a water content of less than 5%; under the catalysis of concentrated sulfuric acid, the mixture is heated by steam at atmospheric pressure and maintained at a temperature of 60–75°C. The reaction proceeds via reflux for 4–8 hours. The ratio of raw oil to methanol to concentrated sulfuric acid is 1000 : (400–800) : 10. After the reflux reaction is complete, the excess methanol vapor is sent to an absorption tower for recovery. The remaining mixture (crude methyl ester) is left to stand for 1.5 hours after which the acidic water is removed. Following washing, it is dehydrated in a dehydration tower. An additive of 1‰ boric acid is added, and after thorough mixing, the mixture is pumped into a distillation vessel. In this vessel, the temperature of the liquid phase is controlled between 220–280°C, and distillation takes place under a vacuum level of 0.9. The distillate accounts for approximately 90–97% of the total output; its main components are mixed fatty acid methyl esters along with a small amount of unreacted fatty acids ； The distillate is cooled to 0°C in a cooling tower; at this temperature, the precipitated solids are removed by filtration. The resulting liquid is biodiesel that can replace 0# diesel. Biodiesel is miscible with diesel in any proportion, making it convenient to use. According to bench tests, the cold-start performance, combustion performance under different loads, power performance, smoke density, and exhaust gas temperature of biodiesel are virtually identical to those of 0# diesel. 2. Specific measures: Add 1,000 kilograms of acidified vegetable oil, 650 kilograms of industrial methanol with a water content of less than 5%, and 10 kilograms of concentrated sulfuric acid into the esterification reactor. Heat it with steam at atmospheric pressure and maintain the temperature at 65–75°C, allowing the reaction to proceed under reflux for 4–8 hours. After the reflux reaction was completed, the mixture was allowed to stand for 1.5 hours; the acidic water was then removed. Subsequent washing and dehydration in a dehydrator followed. Methanol vapor was recovered in a methanol absorption tower. After dehydration, 971 kilograms of crude methyl ester were obtained. 1 kilogram of boric acid was added, and after mixing thoroughly, the mixture was pumped into a distillation vessel. Distillation took place at a liquid phase temperature of 220–280°C under a vacuum level of 0.9, resulting in 859 kilograms of distillate ； The distillate was cooled to 0°C in a cooling tower, and at this temperature the precipitated solids were filtered out, yielding 848 kilograms of fuel methyl ester (i.e., biodiesel). Process CN1560197A: A method for producing biodiesel from swill oil. 1000 parts of swill oil are taken and placed in a beaker; a stirrer is installed on the beaker, and an adjustable-temperature electric furnace is placed below it. Heat under continuous stirring to 75–90°C, with a preferred temperature of 80–85°C. Then, add 250–350 parts of brine at a temperature of 85–90°C and a concentration of 3.5–4.5%. The typical concentration of brine is 4%, and the usual amount used is 300 parts. Stir for more than 25 minutes, usually 30 minutes, after which stop heating and stirring. Allow the mixture to stand for more than 25 minutes, generally 30 minutes, so that separation occurs; this separation can be carried out in a separatory funnel, and the lower layer of wastewater should be discarded. Wash multiple times following these steps; usually 2-3 times is sufficient ； Heat the swill oil, which has been washed with saltwater, to 105–110°C and stir it while dehydrating it for 1–2 hours, until no water vapor or bubbles remain on the surface ； The dehydrated swill oil is mixed with 30–40 parts of activated clay, and stirred at 110–120°C for more than 0.8 hours, usually 1 hour, after which it is filtered using medium-speed qualitative filter paper ； Approximately 610 parts of the aforementioned refined swill oil, about 105–210 parts of methanol – typically 105 parts – and 5–20 parts of tolsulfonic acid – usually 10 parts – are sequentially added to a 1-liter four-necked flask. The flask is equipped with a stirrer with adjustable speed, a mercury thermometer capable of measuring temperatures up to 200°C, a spherical condenser through which cooling water flows, and a 1000W temperature-regulable electric furnace. The reaction is carried out at reflux temperature for more than 6 hours; an optimal time is 7–9 hours, with 8 hours being typical. Stop heating and stirring, and let it stand for more than 1.5 hours; the preferred time is 2–2.5 hours, with 2 hours being a common duration ； The reaction products were separated using a separatory funnel to remove the lower layer of heavier components (mainly excess methanol and glycerol); the lighter components in the upper layer were placed in a distillation flask. Most of the methanol dissolved in the mixture was removed at atmospheric pressure, while the remaining methanol was distilled off under vacuum. The residue remaining in the bottle is biodiesel ； The separated lower-layer recombination components are mainly glycerol and excess methanol; methanol and glycerol are separated through atmospheric distillation, with methanol being able to be reused as a raw material, while glycerol is a widely used basic chemical raw material. CN1654601A process: A method for producing biodiesel. 1. Process: The feed oil is distilled to remove water, reducing its moisture content to below 0.06% ； The dehydrated crude oil enters an ultrasonic transesterification reactor along with a mixture of methanol and catalyst. The molar ratio of methanol to crude oil is maintained at 3:1–20:1, the mass percentage of catalyst is 0.1–1%, the reaction temperature is controlled between 20–64°C, the ultrasound frequency ranges from 18,000–4,000,000 Hz, and the power is kept between 30–1,000 W ； After the reaction is complete, the transesterification product enters a methanol distiller; the methanol distilled off is recycled back to the reactor for reuse. The reaction product after methanol distillation goes into a separator, where glycerol is separated from biodiesel. The biodiesel phase obtained through separation is then neutralized, washed, and subjected to continuous distillation to remove catalysts, saponifies, water, and methanol, thereby achieving further purification and yielding a biodiesel product with a high purity of >99.6 wt%. The glycerol phase, after purification, yields a glycerol by-product of the desired purity. 2. Specific method: The crude material is mechanically cleaned of impurities and then fed into the raw oil storage tank; it is subsequently pumped into a flasher for dehydration at a temperature of 100–150°C for 30 minutes ； The dehydrated crude oil enters the ultrasonic transesterification reactor via a heat exchanger; methanol and a catalyst are added, the temperature is maintained at 20–64°C, and ultrasonic waves are applied to carry out the transesterification reaction ； The ester exchange product after the reaction enters a methanol distiller; the distilled methanol is recycled back to the reactor for reuse. The reaction product after methanol distillation goes into a continuous separator, where glycerin is separated from biodiesel. The biodiesel phase obtained through separation enters a neutralizer, from where the catalyst is removed; it then proceeds to a washer, and after washing it goes into a thin-film evaporator to remove methanol and water. After further separation and purification, it is pumped into a product storage tank. The glycerin phase separated out is dehydrated and free of methanol, resulting in a glycerin by-product of the desired purity ； The residues resulting from neutralization, washing, and evaporation are collected and sent to a distillation unit to recover methanol for reuse. The process described in CN1648208A is a method for rapidly producing biodiesel. 4000 kg of pretreated swine oil (with impurities and moisture removed) is pumped into a 7-cubic-meter sealed tank. Thereafter, it is mixed with a solution composed of a catalyst prepared by combining 20 kg of sodium dodecyl sulfate with 140 kg of sodium hydroxide, along with 1200 kg of methanol. The circulation pump is started, and the mixture is heated to 65–75°C; this process is repeated for 60 minutes. Glycerin and the catalyst, which have a higher density, are removed through centrifugation. The remaining lighter liquid fraction is distilled at 55–90°C to remove water, and the methanol contained in this distillate is recovered for use in subsequent batches. The flocs formed as a result of heating are filtered, yielding 3600 kg of biodiesel. The biodiesel produced from used cooking oil is slightly red in color and transparent; the main reason for this is that used cooking oil usually contains a small amount of chili pigments, which results in trace amounts of these pigments remaining in the final product. Process CN1570029A: A method for preparing biodiesel from natural fats and oils. 1. Process: Natural fats and oils are subjected to a methylation reaction with compounds having a molecular weight of 1–3 carbon atoms. The methyl esters resulting from this methylation, along with those derived from fatty acids containing two or more conjugated double bonds, are mixed together and heated to 100–300°C in the presence of an inorganic acid catalyst. They undergo a blending and polymerization reaction for 1–8 hours. After the reaction is complete, the temperature is reduced to 100–240°C, and vacuum distillation is carried out under a vacuum level of at least 750 mmHg; the liquid obtained as a result of this distillation is biodiesel. The aforementioned inorganic acidic catalysts include bisulfates and various types of activated clay, with activated clay having a pH value of 3–5 being preferred; the amount added is 0–5% by weight of the natural oils. The fatty acid methyl esters containing two or more conjugated double bonds that participate in the blending polymerization reaction can be methyl esters of conjugated flaxseed oil, castor oil, and tung oil, with methyl ester of tung oil being the preferred option. The oil is heated to 70–80°C, and vacuum is applied to achieve a pressure level of over 750 mmHg in order to carry out dehydration for 4 hours. After that, the mixture is cooled to 0–50°C. Alcohols with a molecular weight of 1–3 carbon atoms, along with inorganic catalysts in an amount of 0.1–5% based on the weight of the oil, are added at a molar ratio of oil:alcohol of 1:3 to 1:10. The temperature is then raised to 50–100°C, and the reaction is allowed to proceed for 1–8 hours. Once the reaction is complete, the unreacted alcohol is removed by evaporation. The resulting product is cooled to 0–50°C, and left to stand until the reaction mixture separates into layers; the glycerol in the lower layer is then separated out, yielding the fatty acid ester. 2. Specific measures: In a three-necked flask equipped with a vacuum dehydration device, a thermometer, and a reflux condenser, 296 grams of waste oil were added. The mixture was heated to 120°C, and dehydration was carried out under reduced pressure for 1–2 hours. After cooling to 50°C, 100 grams of methanol and 2.4 grams of 98% concentrated sulfuric acid were added. The reaction was allowed to proceed under reflux for 4 hours; any excess methanol was then recovered. The mixture was cooled again to 50°C and left to stand for 1–2 hours, after which the glycerol layer at the bottom was separated, yielding 288 grams of fatty acid methyl ester. 285 grams of fatty acid methyl ester and 140 grams of tungic acid methyl ester were added to a three-necked flask equipped with a thermometer and a stirrer. A small amount of activated clay and distilled water were also added, the mixture was heated to 240°C, and the reaction was allowed to proceed for 8 hours. Subsequent vacuum distillation yielded 272 grams of dimeric acid methyl ester and 163 grams of pale yellow biodiesel. 272 grams of dimeric acid methyl ester and 406 grams of Mannich-modified amine were added to a three-necked flask equipped with a thermometer and a stirrer. The mixture was heated to 180°C, and the reaction was carried out for about 6 hours until no more methanol was released. As a result, 642 grams of a brownish-yellow viscous liquid was obtained, which is the polyamide used as a flexible curing agent for epoxy resins. Process CN1580218A: A continuous method for preparing short-chain fatty acid esters using animal and vegetable oils as raw materials. (I) Process: 1. Continuous pre-esterification: The raw oil, heated to 100–120°C, is pressurized by a pump and fed into the esterification tank through a nozzle. At the nozzle, 20–30% by weight of the raw oil of short-chain alcohols heated to 70±5°C, along with 0.15–0.3% by weight of an acidic catalyst, are added. Pre-esterification takes place at the nozzle and within the esterification tank; under normal pressure and at the temperature of the material itself, the fatty acids in the oil react with the short-chain alcohols to produce short-chain fatty acid esters and water ； The mixture in the esterification tank, consisting of short-chain fatty acid esters, oils, a small amount of glycerol, and water, is continuously pumped under pressure and returned to the esterification tank through nozzles to form a cycle ； The unreacted short-chain alcohols in the esterification tank, along with the water generated by the reaction, are discharged from the short-chain alcohol gas outlet of the esterification tank and sent to a distiller where the water is separated out. The short-chain alcohol gas, on the other hand, returns to the nozzle without being condensed and is reused in the esterification tank ； When the acidity of the material in the esterification tank is less than 1 (mgKOH/g), a mixture containing short-chain fatty acid esters, oils, a small amount of glycerol, and water from the esterification tank is pumped via its liquid outlet into the supergravity rotating reactor for the next processing step ； At the same time, an equal weight of fat, short-chain alcohols, and acidic catalyst is added to the esterification tank as that of the mixture pumped into the supergravity rotating reactor for the next processing step, in order to maintain balance and ensure continuous reaction. The amount of short-chain alcohols added is 20–30% of the weight of the fat added, while the amount of acidic catalyst added is 0.15–0.3% of the weight of the fat added ； 2. Two-stage supergravity rotational alcoholysis: The mixture obtained at the liquid outlet of the esterification tank in Step 1 – which contains short-chain fatty acid esters, oils, a small amount of glycerol, and water, with an acidity of less than 1 – is used as the raw material. An alkaline catalyst amounting to 0.1–0.5% of the weight of the raw oil is added to this mixture. The mixture then enters the rotor of the supergravity rotational reactor through the liquid nozzle, at a rotation speed of 600–900 revolutions per minute; under the action of the rotor, it moves rapidly in a centrifugal direction. At the same time, gas containing short-chain alcohols, in an amount of 20–30% of the weight of the raw oil, is introduced at the inlet of the reactor’s shell. Under normal pressure and at the temperatures of the reactants themselves, short-chain fatty acid alcohols and glycerol are produced, which are then discharged from the outlet of the supergravity rotational reactor and sent to a disc separator. There, under the high-speed rotation of the disc separator at 1000–7000 revolutions per minute, the short-chain fatty acid alcohols and oils are separated from glycerol, with glycerol, having a higher specific gravity, being discharged from the bottom of the separator. The fatty acid short-chain alcohols and oils with lower specific gravity are discharged from the upper part of the separator and enter the second-stage supergravity rotary reactor, where an equal amount of short-chain alcohol gas and basic catalyst, corresponding to the weight of the oils involved in the reaction, is added. The mixture of fatty acid short-chain alcohols and glycerin that emerges from the outlet of the second-stage rotary hydrolysis reactor enters a disc separator, where glycerin is separated out; thereafter, the mixture of fatty acid short-chain esters along with other components proceeds to the next stage of purification ； 3. Purification: The mixture obtained in step 2, which contains short-chain fatty acid esters, unreacted short-chain alcohols, and trace amounts of oils, is pumped into an evaporator. It is heated to 70–100°C at atmospheric pressure; the short-chain alcohols are then evaporated and recovered. The resulting short-chain fatty acid esters are washed with saline in an amount equivalent to 0.2–1 times their weight ； Then, the pressure is reduced to 10–20 KPa for dehydration, yielding the finished product of mixed fatty acid short-chain esters that meet the quality requirements. (II) Specific measures: 5.0 kg of the mixed oil with a temperature of 100–110°C and an acid value of 20 is pumped into the esterification tank via a nozzle, along with 1 kg of methanol vapor at a temperature of 70±5°C and 0.01 kg of 98% concentrated sulfuric acid as catalyst, for pre-esterification. Once the acidity drops to 1, the mixture is added together with 0.125 kg of a methanol solution containing 20% sodium hydroxide and 1 kg of methanol vapor into a supergravity reactor to carry out the alcoholysis reaction. Glycerin is separated out using a separator; the resulting fatty acid methyl esters and oil are then mixed with 0.04 kg of a methanol solution containing 20% sodium hydroxide and 0.5 kg of methanol vapor and fed into a second supergravity reactor for another alcoholysis reaction. Glycerin is separated again, and unreacted methanol is removed. After washing and dehydration, 4.92 kg of mixed fatty acid methyl esters are obtained, with a yield of 98.4%. With 80% yield, 0.56 kg of crude glycerin is obtained. The process described in CN1556174A is a method for producing biodiesel from vegetable and animal oils with high acid values. (1) The vegetable and animal oils with high acid values are mixed with glycerin in a reaction vessel equipped with a condensation and reflux system. The acid value of these oils ranges from 10–150 mgKOH/g of oil; depending on this acid value, the ratio of the amount of glycerin added to the molar ratio of free fatty acids in the oil is between 0.35 and 2.0. A strong acid is also added as a catalyst, along with a binary or ternary azeotropic distillation solvent. The amount of this azeotropic distillation solvent added is 15–60% by weight of the vegetable and animal oils with high acid values. (2) The reaction is carried out under stirring and heating in a reflux condition; the water generated during the reaction is carried away by the azeotropic distillation solvent. After condensation, the water and the solvent separate automatically. The azeotropic distillation solvent returns to the reaction vessel, while the water is removed. This process continues until no more water is carried out of the reactor, at which point the reaction is complete. The azeotropic distillation solvent is then distilled off, yielding an esterification mixture. The reflux reaction takes place at atmospheric pressure, with the reaction temperature ranging from 60 to 120°C, depending on the azeotropic distillation solvent used. (3) After separating the esterification mixture obtained in step (2) from the catalyst, the esterification mixture is then decolorized using a decolorizing agent. (4) To the decolorized esterification mixture, 15–30% methanol and 0.5–1.2% of a strong base catalyst are added on a weight basis (relative to the amount of the esterification mixture), and transesterification is carried out at a temperature of 60–80°C. (5) The mixture obtained from the transesterification reaction is centrifuged to separate crude glycerol. After acidification and separation, part of the glycerol containing free fatty acids is returned to the transesterification reactor to participate in the esterification reaction in step (1), while most of the crude glycerol is used for glycerol recovery. (6) The fatty acid methyl ester obtained after separating glycerol is washed with 30–45% hot water to remove trace amounts of free glycerol; any excess unreacted methanol also dissolves in the water and is carried away. The fatty acid methyl ester resulting from this washing process (the crude ester) is separated by centrifugation, and the aqueous phase is distilled to recover methanol, which is then sent back to the methanol storage tank. The temperature for the hot water washing is controlled at 60–95°C. (7) The washed fatty acid methyl ester is subjected to winterization in a winterization machine at a temperature of -5 to 3°C; after winterization, the high-melting-point substances are separated to obtain pure fatty acid methyl ester – a biodiesel product. CN1151433A: A method for synthesizing fatty acid methyl esters using cottonseed soap residue as raw material. The process involves preparing mixed fatty acid methyl esters from cottonseed soap residue through acidification, esterification, deacidification, and vacuum distillation. Cottonseed soap residue and concentrated sulfuric acid are mixed in a ratio of 10:0.5–1.5 by weight and placed in a reactor where they are stirred and the temperature is increased. When the temperature reaches 105°C, a sample is taken to check the pH value of the lower layer of solution; thereafter, the pH value is adjusted to 2–3 using cottonseed soap residue. The mixture is then kept at this temperature for 0.5 hour, after which heating and stirring cease. The mixture is allowed to stand for 0.5–1 hour, after which the acidic liquid in the lower layer is transferred to a storage container or reused. The fatty substances in the upper layer are washed with an equal volume of tap water, and this washing process is repeated until the pH value of the wash water reaches 4–5. After that, the mixture is stirred and heated again, and under a vacuum pressure of 600 mm/Hg, it is heated to 250°C for 0.5 hour to carry out dehydration, reducing the water content to less than three parts per ten thousand ； In the esterification reaction, methanol and dehydrated fats are added to the reaction vessel in a weight ratio of 1.5–2.5:1. Then, concentrated sulfuric acid accounting for 2%–5% of the total weight of methanol and dehydrated fats is added to the vessel. The mixture is heated under stirring to the reflux temperature (approximately 65–70°C), and the reaction is allowed to proceed at this temperature for 15 hours. After that, the reflux setup is replaced with a distillation setup; the excess methanol is vaporized and reused. Heating is stopped when the temperature reaches 110°C ； During the deacidification process, an equal volume of tap water is added to the crude ester obtained from the esterification reaction, and repeated washing is carried out until the pH value of the aqueous solution released is close to 7. Then a sample is taken to determine the acid value of the crude ester; based on this value, 5% excess sodium carbonate is added, and after stirring, the temperature is raised rapidly to 100–120°C where the reaction proceeds for 10 minutes ； During the vacuum distillation process, the acid-depleted crude ester is preheated to 200°C and then connected to the distillation vessel via a conduit; a valve is attached to this conduit. Heating and distillation take place while maintaining the temperature between 220 and 230°C and a vacuum level of 750 mmHg. Subsequently, the valve on the conduit is gradually opened to start the vacuum distillation, and the substance distilled out is the mixed fatty acid methyl ester. The sulfuric acid added during the esterification process mainly reacts with the sodium salts of fatty acids present in cottonseed soap scum, producing fatty acids that are insoluble in water as well as in dilute sulfuric acid. These fatty acids, along with neutral oils, monoglycerides, diglycerides and other fatty substances that do not react with dilute sulfuric acid, precipitate out of the solution. After standing, the entire solution separates into three layers: the upper layer consists of fats, the middle layer is gelatinous, and the lower layer is an aqueous solution of waste acid. Since the esterification reaction is reversible, the crude ester obtained after completion of the esterification reaction and washing still contains a small amount of free fatty acids. The presence of these free fatty acids directly affects the acid value of the pure ester obtained through vacuum distillation of the crude ester; therefore, it is necessary to remove as much of the free fatty acids present in the crude ester as possible. Tests show that sodium carbonate is the most effective. The optimal temperature for the deacidification process is 100–120°C. Based on the acid value of the crude ester, the amount of base added only needs to exceed 5% of the theoretical amount required for complete neutralization of the free fatty acids. At this point, the loss of ester is minimal. CN1073474 A method for producing fatty acid methyl esters: 1. Continuous process flow: Crude oil is heated and vacuum-dehydrated using a rotary thin-film evaporator. Dehydrated oils, low-carbon alcohols, and acidic catalysts are fed into a pipe mixer in certain proportions via a material pump, where a pre-esterification reaction takes place at 60–80°C to reduce the acid value to below 1 (mmKOH/g). The pre-esterified oil and the basic catalyst are pumped into a pipeline mixer in a certain ratio, where an alcoholysis reaction takes place at 55–75°C, with the by-product glycerol being removed continuously using a separator. Low-carbon alcohols, basic catalysts, and partially alkoxylated fats are pumped in together into the pipeline mixer, and glycerin is removed using a separator. The resulting crude methyl ester has the excess low-carbon alcohols removed using an evaporator. Condensers and alcohol receivers are used for the recovery of low-carbon alcohols. The crude methyl ester free of alcohol and brine are fed into the washing tank to wash away the soap and residual glycerol in the methyl ester. Place the washed methyl ester along with the washing water in a water separation tank to separate out most of the washing water. The two distributors are used alternately to ensure continuous operation; after washing, the methyl ester is fed into a rotary thin-film evaporator where it is heated under vacuum to remove residual water, resulting in high-quality methyl ester. 2. Semi-continuous process flow: Crude oil is dehydrated using a rotary thin-film evaporator and then placed in a mixing tank. Low-carbon alcohols and acidic catalysts are also placed in the mixing tank. The pre-esterification reaction is carried out in a tubular mixer by pumping in under conditions of 60–80°C; the reactants then enter a mixing tank for continuous reaction until the acid value drops below 1. An alkaline catalyst is added, and the alcoholysis reaction is carried out at 55–75°C using a pump and a tubular mixer. The by-product glycerol can be removed at any time using a separator, and the crude glycerol flows into the glycerol tank. In the later stage of the reaction, a low-carbon alcohol and an alkaline catalyst are added to compensate for what has been taken away by glycerol. Once the alcoholysis is complete, the excess low-carbon alcohols are distilled off; these alcohols are recovered using a condenser and an alcohol receiver. Saltwater is then added to the mixing tank to wash the crude methyl ester, thereby removing impurities such as soaps and residual glycerol from the methyl ester. The final methyl ester is obtained after dehydration. Specific measures: In a setup equipped with a tubular mixer of type Dg25 with a length of L=30m, 100 kg of dehydrated coconut oil with an acid value of 8.57 mgKOH/g, 20 kg of anhydrous methanol, and 0.2 kg of sulfuric acid with a purity of over 95% were used to carry out a pre-esterification reaction via the tubular mixer at temperatures of 65–70°C, resulting in a reduction of the acid value to 0.67 mgKOH/g. Add 1.5 kg of sodium methoxide with a concentration greater than 27%, and carry out an alcoholysis reaction in a pipe mixer at a temperature range of 60–70°C; meanwhile, use a separator to remove the by-product glycerol, and add 10 kg of methanol and 0.5 kg of sodium methoxide. After the reaction was complete, the excess methanol was distilled off, followed by washing with water and dehydration; as a result, 98.5 kg of methyl ester was obtained with a conversion rate of 98.7%, an APHA color value of 150, and 16.9 kg of glycerin with a purity of 79.23%. CN1594504A Supercritical preparation process for biodiesel: The process involves reacting vegetable and animal oils, used cooking oil, gutter oil, and oils from oilseed crops with supercritical low-carbon alcohols. Methyl fatty acid esters are produced through processes such as esterification and transesterification, including the following steps: filtration ； Dehydration ； Esterification, transesterification ； Filter ； Vaporized methanol ； Phase separation. The process conditions are: (1) The filtration of edible oil and gutter oil is carried out at 10–40°C for 20–50 minutes ； (2) The dehydration of used cooking oil and gutter oil is carried out under vacuum at 50–100°C ； (3) Esterification and transesterification are carried out at 220–400°C and 8–25 Mpa, using catalysts such as superstrong solid acids, superstrong solid bases, and metal oxides; the reaction time is 4–30 minutes ； (4) During esterification and transesterification, the amount of low-carbon alcohols used is 6–60 times the mass of the fats and oils ； (5) Oil crop seeds are filtered at 10–40°C for 30–60 minutes ； (6) Methanol evaporation is carried out at 60–70°C for a duration of 30–60 minutes. Methanol can be reused ； (7) Phase separation is carried out at 20–60°C for a duration of 20–50 minutes. Specific measures: Mix 50 g of purified used cooking oil with 120 g of methanol. Heat the mixture to 300°C; at this temperature, the pressure gauge shows a pressure of 13.5 Mpa. Then maintain this temperature for 15 minutes ； The high-temperature and high-pressure reactor is cooled to room temperature using condensate water ； The methanol present during the reaction process is vaporized off at 60–70°C; the methanol can be reused ； Phase separation was carried out at 60°C for a total of 30 minutes, resulting in the production of 44.8 g of fatty acid methyl ester—biodiesel, with a yield of nearly 90%. CN1626621A A new method for producing biodiesel from vegetable oils. Process: Using vegetable oils and small-molecule alcohols as reactants, along with a cosolvent, an ester exchange reaction is carried out under supercritical conditions to convert fatty acid glycerides into fatty acid small-molecule alcohol esters (i.e., biodiesel). Among them, the molar ratio of small molecular alcohols to vegetable oils is 3-45:1; after a reaction time of 4-30 minutes, biodiesel is produced. The production process and process conditions are as follows: 1) The reaction materials and co-solvents are placed in a high-pressure reactor with automatic temperature control and heated to 200-350℃ ； 2) Control the reaction pressure at 10-30 Mpa ； 3) The temperature-controlled reaction is terminated after 4–30 minutes, and the final reaction product is separated to produce the finished biodiesel. Specific measures: 58.1 grams of soybean oil and 70.5 grams of methanol were placed into a high-pressure reactor; the reactor was sealed and the air inside it was replaced with an inert gas, after which 36 grams of co-solvent CO2 was added. The pressure and temperature of the reaction vessel are monitored in real time by instruments. The pressure vessel is heated by an external heater, and the temperature inside the vessel is monitored by thermocouples. The voltage is adjusted to reach 300°C within 30 minutes, with a tolerance of ±5°C; the transesterification reaction is completed within 25 minutes, after which it is transferred to a water bath to stop the reaction. After the reaction, the gas is vented, and the mixture in the pressure reactor is poured into a collector. The reactor is washed with methanol, and the product to be processed is allowed to settle for 60 minutes; it separates into 3 layers, with the methanol phase being the top layer, which is then separated out. The remaining two layers were separated and distilled at 60–80°C for 30 minutes each to remove the remaining methanol. The mass of the residues was measured, and high-performance liquid chromatography was used to analyze them (column length: 25 cm, diameter: 4.6 mm; temperature: 40°C; flow rate of methanol as the mobile phase: 1.0 ml/min; injection volume: 20 ul). The products identified were plant oil methyl ester (biodiesel) and glycerol. Measurement of product quality: 57.2 grams of vegetable oil methyl ester and 6 grams of glycerin, giving a calculated reaction yield of 98%. This post was last edited by kamer on 2008-2-25 11:39.]