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Catalytic esterification technology and biodiesel industrialization 2007-12-7 10:56:02 Abstract: This article introduces the new progress in the production process of biodiesel and some new achievements in recent domestic research on biodiesel. It focuses on the application of chemical transesterification and biological transesterification in the production of biodiesel. In particular, some new technologies proposed in recent domestic research on the industrial production of biodiesel are described in detail. Biodiesel has attracted widespread attention around the world due to its excellent environmental friendliness and renewable nature. Keywords: biodiesel; transesterification; biocatalyst; animal fat As early as 1895, when Rudolf Diesel invented the compression ignition engine, the fuel used was peanut oil. Biodiesel is also called biodiesel. It is a new type of bioenergy that has developed rapidly in recent years. It is produced from renewable biological resources and can replace petrochemical diesel and environmentally friendly green and clean fuel. It is also a raw material for manufacturing biodegradable and value-added fine chemical products. It is the only alternative fuel that meets all health impact testing requirements stipulated in the U.S. Clean Air Act. At present, a new renewable energy industry represented by biodiesel is booming around the world and developing extremely rapidly. It has become a hot commodity in today's international fuel market and will form an important part of the sustainable development of energy in the future, with far-reaching economic and social benefits. 1 Problems and Research The high viscosity characteristics of space primitive animal and vegetable oils are one of the key factors that make them unsuitable for diesel engines, so their fluidity must be improved. Commonly used methods mainly include solvent dilution method, thermal decomposition method, microemulsion method and transesterification method. At present, the more ideal method is transesterification. That is, at a certain temperature, grease and lower alcohols such as methyl (ethanol) alcohol are transesterified under an acid or alkaline catalyst to generate the corresponding fatty acid methyl ester (biodiesel), and at the same time produce glycerin. However, the disadvantages of alkali-catalyzed esterification are that it is difficult to recover glycerol and remove the catalyst, the reaction is incomplete, and when the oil contains free fatty acids and/or water, saponification products will be generated. The process is complex, high energy consumption, and easy to cause environmental pollution. This method still has shortcomings such as a long process flow, the discharge of alkali-containing waste liquid, heterogeneous reaction, slow reaction speed, and long reaction time. When diesel is produced from animal and vegetable oils (triglycerides) with fatty acid esters catalyzed by alkali, this process generally requires a pretreatment step to remove free fatty acids from the feed, because the presence of free fatty acids will reduce the reaction speed, and the phase separation of fatty acid esters and glycerol products is difficult, resulting in a reduction in yield; it is also difficult to remove the alkali catalyst from glycerin; at the same time, alkali-containing wastewater must be pre-treated from the process, which consumes a lot of energy. The main problem with the usual chemical esterification method for producing biodiesel is its high cost. According to statistics, 75% of the cost of biodiesel preparation is the cost of raw materials. Therefore, using cheap raw materials and improving the conversion rate to reduce costs are also one of the keys to whether biodiesel can be scaled up and industrialized. 2 Biological enzyme-catalyzed esterification method If the biological transesterification method using enzymes or whole cells as catalysts replaces the traditional chemical transesterification method, some of the above shortcomings can be overcome. The bioenzymatic process is simple, the reaction conditions are mild, the selectivity is high, the amount of alcohol is small, the by-products are few, the generated glycerol is easy to recover, and no waste liquid treatment is required. The key to this method is the catalyst. Lipase can efficiently catalyze the transesterification reaction between alcohol and fatty acid glycerides. The use of lipase can solve the problems of the current catalysts used in traditional chemical methods to produce biodiesel, such as difficulty in separation and too much energy required. However, the disadvantage is that generally the transesterification efficiency cannot be achieved without the use of organic solvents, but when a certain amount of methanol is used in the reaction system, the lipase will be inactivated and lose its catalytic ability; at the same time, the enzyme price is high and the reaction time is long. Therefore, improving lipase activity and preventing enzyme inactivation are the keys to whether this method can achieve industrial production. 21 Free lipase is used as a catalyst to catalyze the lipases used to synthesize biodiesel, mainly yeast lipase, pseudounicellular lipase, Candida lipase, Rhizopus lipase, Mucor lipase and porcine axillary lipase. For example, Rhizopus lipase can catalyze vegetable oil to produce diesel in a reaction system with an initial water content of 4% to 30%. Various factors for Cryptococcus to catalyze the transesterification of vegetable oil in the aqueous phase have been obtained: the oil/methanol molar ratio is 1:4, the water content mass fraction is 30%, the reaction speed is 160r/min, 30℃ for 120h, and the final fatty acid methyl ester is The mass fraction can reach 80.2%; in n-hexane, Candida lipase catalyzes the conversion of the substrate of palm oil and short-chain alcohol, and the conversion rate reaches 786% in 4 hours of reaction; when n-propanol is the substrate, the conversion rate reaches 96.0% in 8 hours of reaction. Lipase has good selectivity and high catalytic activity, but as a catalyst for large-scale industrial production, it still faces some problems that need to be solved. Lipase is expensive and the production cost of using it as a catalyst is high, which limits its application in industrial-scale production of biodiesel. The methods to solve this problem are: first, to use lipase immobilization technology so that it can be used repeatedly; second, to use the entire cell that can produce lipase as a biocatalyst. 22 Immobilized lipase is used as a catalyst to introduce immobilization technology into the industrial production of biodiesel. * * Improve enzyme stability and reusability and reduce costs. Japan uses immobilized Candida lipase produced by Danish Novozymes to react at 30°C for 48 hours, and the conversion rate can reach 97.3%. At the same time, it was found that the solubility of methanol in the mixed system of triacylglycerol and fatty acid methyl ester is better than that in the pure triacylglycerol system. The reaction took 36 hours and the conversion rate reached 96.8%. In order to avoid enzyme inactivation caused by methanol, Tsinghua University in my country used ethylthiomethyl ester instead of methanol as the acyl acceptor to conduct transesterification reaction with soybean oil (molar ratio = 12:1). Novozym435 was also used as the catalyst, and the corresponding methyl ester yield was 92%. The disadvantage is that the amount of enzyme is too large, and an enzyme with a mass fraction of 30% (compared to the oil mass) must be added. It can be said that the application of immobilization technology has taken a solid step towards the industrial production of biodiesel. Enzymatic synthesis of biodiesel is a potential biocatalytic process. It has been proven that the lipase extracted by fermentation method (Candidasp.99-125) can be used to prepare biodiesel through transesterification reaction by adsorption cold fixation method. When n-hexane is used as the solvent, 15% immobilized lipase (enzyme activity 18000 U/g relative to the mass of oil) is added to 20% mass fraction of water, the temperature is 40°C, and pH=7, and 1 mol equivalent of methanol is added dropwise every 10 hours for a total of 3 times, the maximum conversion rate of the reaction can reach 96%, and the half-life of the immobilized enzyme can reach more than 200 hours. 23. Whole-cell enzymes as catalysts. The above-mentioned lipases are used as catalysts. If whole-cell enzymes are used as catalysts and adsorbed in some porous and permeable biomass supports, the complex enzyme purification and immobilization processes can be omitted. * * Reduce industrial production costs. Some researchers have constructed Saccharomyces cerevisiae MT8-1 based on Rhizopus lipase. Its fat activity can reach 474.5IU/L. After using pre-freeze-thawing or air-drying methods to enhance the permeability of the yeast cells, it was used to catalyze the reaction of synthesizing fatty acid methyl esters from soybean oil. The mass fraction of methyl esters in the reaction solution was 71%. In further research, after the cells were co-cultured with the porous carrier for 80 to 90 hours, methanol was directly added to the fermentation broth three times, and the mass fraction of methyl ester obtained reached 90%, which is equivalent to the effect of using extracellular enzymes as catalysts. Whole-cell enzymes have great potential as catalysts in industrial production. Through genetic engineering technology, improving the expression level of lipase and its tolerance to methanol can further improve the efficiency of whole-cell enzymes. 3 Other Process Technology Progress 3.1 Supercritical Technology The principle of using vegetable oil and supercritical methanol to prepare biodiesel is the same as the chemical esterification method, which is based on transesterification reaction. However, in the supercritical state, methanol and oil are homogeneous, and the rate constant of the homogeneous reaction is large, so the reaction time is short; in addition, because no catalyst is used in the reaction, the subsequent process is simpler, no waste alkali liquid is discharged, and the cost is greatly reduced compared with the chemical method. In the traditional method, due to the poor mutual solubility of methanol and animal and vegetable oils and fats, the reaction system is two-phase. The transesterification reaction can only be carried out on the two-phase interface, the mass transfer is limited, and the reaction rate is low. In order to increase the contact area between the two phases and increase the reaction speed, Japan's Sumitomo Chemical Company has successfully developed a supercritical method to produce diesel. It reacts methanol with vegetable oils such as rapeseed oil and soybean oil. The reaction is carried out at 240°C and 8MPa to generate fatty acid methyl esters and glycerol as a by-product. The output ratio is 1:3 and has been patented. Usually fatty acid methyl ester completes the above reaction in the presence of sodium hydroxide alkali catalyst. However, this route will lead to the production of by-product soap, which must be removed by washing with water, which will increase the cost. Sumitomo Chemical Company's process has a fatty acid methyl ester yield of 100%. Tsinghua University in my country has also studied the reaction conditions of supercritical methanol method for preparing biodiesel and its impact on the methyl ester formation rate. The results show that the greater the amount of alcohol-to-oil substances, the higher the soybean oil conversion rate. Increasing temperature helps to increase the reaction rate. The effect of temperature is particularly obvious near the critical temperature of 239°C. When the pressure is higher than 135MPa, the effect of pressure on the reaction is not obvious. Among the raw materials, The esterification rates of different fatty acid methyl esters are different, and they decrease in the order of linoleate, oleate, palm oil, and stearate; less than 50% (free oleic acid) in soybean oil does not affect the reaction rate, and less than 20% w (H2O) in crude oil has little effect on the reaction. When the ratio of alcohol to oil is 42:1, the reaction temperature is 289°C, and the reaction is 1 hour, the oil conversion rate can reach 78%. Because in the supercritical state, methanol is hydrophobic and has a relatively low dielectric constant, glyceryl ester is completely dissolved in methanol, forming a single-phase reaction system, the transesterification reaction speed is fast, and the overall yield of methyl ester is increased. Since there is no catalyst in the process, not only is the product purification simple, but no wastewater is produced, making the transesterification process simpler, safer and more efficient. The reaction temperature has a significant impact on the conversion rate of esterification exchange reaction. For traditional chemical methods, due to the different vegetable oils used, the optimal reaction temperature is 20 to 60°C. When vegetable oil is in supercritical methanol, the yield of fatty acid methyl esters is also closely related to the temperature. When the molar ratio of methanol to rapeseed oil was 42:1, the reaction temperature was changed from 200 to 500°C. When the reaction is carried out at 200-230°C below the supercritical temperature, the reaction rate decreases. After 1 hour, about 68%-70% of the vegetable oil is converted into fatty acid methyl esters; when the reaction is performed at 270°C, the conversion efficiency is still not very high because it is in the subcritical and supercritical conversion stage; when the reaction temperature reaches above 300°C, 80%-95% of the vegetable oil is converted into fatty acid methyl esters within 4 minutes. But when the temperature reaches 400°C, the decomposition reaction replaces the esterification reaction and produces other substances. Therefore, 350℃ is suitable. Currently, two reaction devices are commonly used in supercritical technology, namely DadanKusdiana's tubular reactor and Ayhan Demirbas' high-pressure reactor. The traditional method takes a long time to produce biodiesel (1 to 8 hours). The use of supercritical methanol can reduce it to 4 minutes. The requirements for raw oil are also low. Waste oil with high water content and acid value can be used. Biodiesel with a conversion rate of more than 98% can be obtained without treatment. Supercritical methanol is not only the reaction medium, but also the reactant and catalyst. The esterification reaction increases with prolongation of time. At 60°C, when the molar ratio of alcohol to oil is 6:1 and the mass fraction of catalyst sodium methoxide is 0.5%, the conversion rate of vegetable oil reaches 95% to 98% after 1 hour. Supercritical methods can be used to * * Improve reaction speed. Rapeseed oil and supercritical methanol reacted at a temperature below 350°C at an alcohol-to-oil ratio of 42:1. The conversion rate of rapeseed oil reached more than 40% after 30 seconds, and 95% of the rapeseed oil was converted into fatty acid methyl esters after 240 seconds. Hazelnut oil reacted with supercritical methanol at a molar ratio of 41:1, and the fatty acid methyl ester absorption rate reached more than 90% after 200 seconds. 3.2 Engineered microalgae to solve the problem of high biodiesel cost, the United States * * The Renewable Energy Laboratory (NREL) constructed "engineered microalgae" through genetic engineering technology, opening up a new technical approach for biodiesel production. Under laboratory conditions, the lipid content in "engineered microalgae" can be increased to more than 60%, and in outdoor production it can be increased to more than 40%. However, in general, the lipid content of microalgae in natural conditions is only 5% to 20%. Due to the efficient expression of the acetyl-CoA carboxylate (ACC) gene in microalgae cells, the lipid content in the "engineered microalgae" has been greatly increased. Currently, research is underway to select appropriate molecular vectors to fully express the ACC gene in bacteria, yeast and plants. The modified ACC gene will be further introduced into microalgae to obtain more efficient expression. Microalgae have high production capacity. Using seawater as a natural culture medium can save agricultural resources. The oil yield per unit area is dozens of times higher than that of terrestrial plants. The diesel produced does not pollute the environment. Therefore, the development of oil-rich microalgae or "engineered microalgae" is a major trend in the production of biodiesel. 3.3 A new process in the development of the catalytic reverse ester method is a process verified on the German Leer 80kt/a unit that can reduce the chemical and energy consumption costs of conventional diesel production processes. It uses alkali catalyzed reverse esterification (specific reverse methylation) and uses a co-solvent to form an oil-rich single-phase system, so the reaction can be carried out at room temperature. The reaction can be 95% completed within 10 minutes, while the existing traditional process takes several hours. The second 100kt/a device was also put into operation in Hamburg, Germany. Another innovative process is the use of continuous reverse esterification reactor (CTER), which can reduce investment costs. The 35kt/a biodiesel plant built by Amadeus Company in Western Australia will use CTER technology. Another advanced process is the enhanced mixed esterification of oil and methanol in a continuous flow reactor. In 2002, a 100kt/a biodiesel unit using this technology was built in Marl, Germany and is now in operation. 12kt/a high-grade glycerol can be recovered from this process. This technology is also used in the 100kt/a device of Southern Power Company in Riverdale, California, USA. In the continuous Esterfip-H process, the reverse esterification reaction uses excess methanol at a slightly higher temperature than the homogeneous process. The excess methanol is removed by flash cooking and recycled to the process to be mixed with fresh methanol. This chemical conversion is achieved using two fixed-bed reaction stages in series, separating the glycerol to change the equilibrium. Excess methanol is flashed off, and esters and glycerol are separated in the settler. After the final recovery of methanol, biodiesel is recovered by boiling under reduced pressure, and then purified to remove glycerol. The purity of methyl ester exceeds 99%, and the yield is nearly 100%. 3.4 Ion exchange resin catalytic technology The biodiesel process developed by Japan's Yonemoto can avoid the problems caused by alkali as a catalyst. The process operates under mild conditions (50°C, 0.1MPa). The new process fills a mixture of vegetable oil, animal fat and alcohol (methanol, ethanol) into a fluidized bed reactor filled with cation exchange resin. The product is pumped to the second fluidized bed reactor filled with anion exchange resin, which catalyzes the reverse esterification of triglyceride. The esterification reaction is carried out in one of the two reactors, and the other reactor is used as the catalyst regeneration volume. The catalyst contaminated by glycerol is first eluted with an organic acid solution and then an alkali solution for regeneration. In laboratory tests, the total conversion rate of low esters by this process was nearly 100%, and the by-product glycerol can be removed from the product through simple phase separation or simple distillation. Research is now underway to improve the process and improve the life of the ion exchange resin catalyst, and the process will soon be industrialized. Japan's TohoKu University Engineering Department Research Institute and Mitsubishi Chemical Company have successfully studied a biodiesel production process using ion exchange resin as a solid catalyst. This process is not affected by free fatty acids in the raw materials, so there is no worry about reducing the yield of biodiesel. At the same time, the by-product glycerin is not mixed with the catalyst, so it can be a process that can be directly used in industry. 4 Practical application of new process technology (1) Kansai Chemical Engineering Company of Japan has launched a simple and low-cost process that uses whole-cell organisms as catalysts for the reverse esterification of waste vegetable oil. The new technology immobilizes RhizopasOryze cells on biomass-supported multiparticulates (BSP) made of polyurethane foam to culture lipase. Glutaraldehyde 0.1% solution was added to stabilize Rhizopas Oryze cells and improve lipase activity. Vegetable oil was added to the aqueous culture medium with BSP-fixed cells, and methanol was added step by step. The reaction was carried out at 30°C. The methyl ester yield reached 90%. The lipase activity remained active after 6 batches of cycles. The new process does not produce a large amount of wastewater like the alkali catalyst route, does not require a complicated purification process, has no free acid and no catalyst residue, and produces fatty methyl esters and glycerol of good quality. The process will soon be commercialized. (2) The introduction of immobilization technology into biodiesel industrial production can * * Improve enzyme stability and reusability, and reduce costs. Japan uses immobilized Candida lipase produced by Danish Novozymes to react at 30°C for 48 hours, and the conversion rate can reach 97.3%. In the presence of fatty acids, lipase can also effectively catalyze the alcoholysis of soybean oil. In a system with very low water content, Candida antarctica lipase can effectively catalyze the generation of plant methyl esters; at a starting water content of 4% to 30% In the reaction system, the extracellular lipase of rice root enzyme can catalyze the transesterification reaction, and the enzyme is almost inactive in the absence of water. When waste oil is used as a substrate, the enzyme is indeed a very useful and effective enzyme, because waste oil contains a certain amount of moisture. (3) Fatty acid methyl ester (FAME) is a typical biodiesel that has been studied more in recent years. However, the European standard EN590 does not allow the use of blended diesel oil with more than 5% FAME. Reducing NOx is very important for diesel fuel, but when burning higher-concentration biodiesel blended oil, NOx emissions increase. The current production of FAME in Europe exceeds 200kt/a, and about 1/2 of the production capacity is in Germany. The second generation diesel technology emerged as the times require. This technology is based on the hydrogenation pathway in refineries. After processing animal and vegetable oils, synthetic diesel can be obtained by hydrogenation through the BTL-diesel process. BTL-diesel (synthetic diesel) has now been introduced into Europe as a new method of biofuel. It is a high-quality diesel used in the overall composition of ULSO - a biofuel component. The 170,000 t/a BTL diesel unit built by Finnish Nast Petroleum Company in Parvo Refinery will be put into production in 2007. In addition, Total Nast is building its second BTL diesel unit. (4) ShiroSaka et al. use a tubular reactor to produce diesel, that is, mix rapeseed oil and methanol in a tubular reactor at a certain molar ratio, and quickly put the reactor into a preheated tin bath (oil bath) to allow the rapeseed oil to react with methanol in a supercritical state, and then move the reactor into water to complete the reaction. The entire process is determined by monitoring the temperature and pressure in the reactor to determine whether it has reached the supercritical state. After the reaction is completed, the liquid is taken out of the reactor and left to stand for 30 minutes for stratification. The upper and lower layers were distilled at 90°C to recover methanol. Ayhan Demirbas is produced using an autoclave with a capacity of 100mL and can withstand 850K and 100MPa. The internal temperature and pressure can be monitored at any time. Inject certain raw materials (20-30g rapeseed oil, 30-50g methanol) from the hole of the autoclave. After sealing, the autoclave is heated from the outside, preheated for 15min, and the temperature is controlled at +5/-5℃. After the reaction is completed, the gas is discharged and the liquid product is collected. (5) Zhou Yong, Yang Zhengyu, et al. used the original chemical structural characteristics of carbohydrates and lignin in straw, and under the action of catalysts, selectively controlled the cleavage of ether bonds, phenol ether bonds, dialkyl ether bonds and the carbon-carbon chains between connecting units, controlled the reaction conditions, formed highly active free radicals, achieved targeted tailoring and recombination of polymers in the straw, and prepared steam and diesel fractions. Its liquid phase contains 40% diesel, 20% gasoline, and the rest are organic compounds such as benzene and phenol. This method opens up broad prospects for obtaining petroleum and fine chemical raw materials. (6)Diester Company built a 160kt/a fatty acid methyl ester (FAM) plant in Sète, France E) The new device is the first industrial device using Axens' Esterfip-H process. The main component of biodiesel, FAME, is produced from vegetable oils such as rapeseed oil, soybean oil, and sunflower oil. The Esterfip-H process was developed by the French Petroleum Institute (IFP) and commercialized by Axens. A homogeneous catalyst is used. The new device uses a heterogeneous catalyst, that is, two non-metallic spinel mixed oxides. It avoids some problems caused by homogeneous catalysts, such as several neutralization and washing steps of the NaOH or sodium methoxide process, and does not produce waste streams. The purity of its by-product glycerol can reach 98%, while the purity of the homogeneous route is only 80%. 5 Overview of Domestic R&D 5.1 Rich sources of raw materials my country is very rich in biodiesel raw materials. Agricultural raw material oils include soybean oil, rapeseed oil, corn oil, cottonseed oil, peanut oil, sunflower oil, palm oil and coconut oil. There are also Pistacia chinensis, Pistacia sorbifolia, Jatropha curcas, etc. Recycled animal oil can also be used. my country is rich in oil-bearing plants, with a total of 1553 species in 151 families. Among them, there are 154 species of plants with seed oil content of more than 40%. There are about 30 species of trees and shrubs that can establish oil raw material bases for large-scale biolipid fuel. The total amount of agricultural and forestry biomass resources in my country is huge. The yield of plant straw alone reaches 700 million t/a. If microbial conversion technology is used, 100 million t of biodiesel can be produced. If the cultivation of energy plants (switchgrass, miscanthus, etc.) and microbial oil fermentation form an integrated industrial chain, land biodiesel production capacity can * * improve. Taking some high-sugar plants that can be grown extensively, such as sweet potatoes, cassava and Jerusalem artichokes, for example, the current tuber yield per mu can reach 1.2 tons, and the dry weight of stems and leaves is more than 1.3 tons, exceeding the yield levels of corn and wheat. The development of the biodiesel industry requires unconventional oil production technology. While continuing to strengthen the development of plant base resources that save cultivated land, we should vigorously strengthen the development and utilization of microbial oil fermentation technology. my country's close neighbors are Indonesia, Malaysia, etc. * * Tens of millions of tons of palm oil are produced every year, which is also the raw material for the preparation of biodiesel introduced into our country. There are dozens of companies in my country that use oil crops/catering industry as raw materials to produce biodiesel, with an output of more than 100,000 t/a. 5.2 Industrialization research is emerging. China's first industrial-scale biodiesel manufacturer uses "acidified oil residue" obtained by acid treatment of solid residues produced by alkali refining in vegetable oil pressing plants as raw materials. The latter, as waste from processing plants, is sold for 1,100 to 2,300 yuan/t, and the biodiesel obtained is 3,000 to 3,500 yuan/t, including tax exemptions, and can compete with conventional diesel. At present, there are three biodiesel synthesis technology routes in my country, namely the chemical method of the University of Petroleum, the lipase process of Beijing University of Chemical Technology, and the supercritical reaction process of Sinopec Institute of Petroleum and Chemical Engineering. In recent years, a number of companies have also invested in production and application. The raw materials used are mainly gutter oil and vegetable waste oil, such as Hainan Zhenghe Company, Fujian Zhuoyue Energy Company, Sichuan Gushan Oil Company, etc. The route of preparing biodiesel from biomass with microbial oil fermentation as the core technology proposed by Dalian Biotechnology has achieved initial results. There are dozens of companies in my country that use oil crops/waste oil from the catering industry as raw materials to produce biodiesel, with an output of more than 100,000 t/a. according to * * It is planned that by 2010, my country's biodiesel production capacity will reach 2 million tons, and by 2020 it will reach 15 million tons. A biodiesel base with a production scale of 20kt/a has been built in Longyan City, Fujian Province. This project marks the first industrialization of biodiesel production in my country. The construction meets the performance requirements of 0# diesel internal combustion engine fuel. It has been included in the key innovative technology projects of Fujian Province in 2002 and is expected to be included in the list. * * Key technical projects. Beijing University of Chemical Technology has developed a new process for enzymatic synthesis of biodiesel with my country's independent intellectual property rights, developed lipase, and built the first 200t/a pilot plant for enzymatic biodiesel production at home and abroad. It has the industrialization conditions for building a 10,000-ton enzymatic biodiesel plant. The technical advantages are: ① Special Candida lipase for enzymatic method, the enzymatic rate can reach more than 95%. The fermentation level is 8000U/mL, and the cost of enzymes in biodiesel products is only 0.12 yuan/L; ② The developed enzyme immobilization method and membrane reactor, the identification conclusion is that the overall technical level has reached the international advanced level; ③ The biodiesel enzyme reaction separation coupling process also passed the identification in 2005. The lipase developed in Henan, my country, has been successful in converting ebony seed oil ester into diesel. The device has an investment of 196 million yuan and is expected to be completed in 2010. Bio-enzyme production of biodiesel with independent intellectual property rights has a lifespan of up to 160 batches and a conversion rate of 85%. Jiangsu Wuxi Huahong Company currently has two sets of units officially put into production with capacities of 10,000 t/a and 20,000 t/a respectively. In addition, 100,000 t/a biodiesel production is being planned. The 600,000 t/a biodiesel plant built by Anhui Guofeng Group with an investment of 500 million yuan is the second bioenergy diesel project in the province. The first biodiesel project with a production capacity of 200,000 tons was originally planned to be put into operation in August 2006. Southeast University in my country has made new progress in biodiesel research. This process uses a supported solid base as a catalyst to carry out catalytic reactions in a fixed bed. The conversion rate of biodiesel reaches 95%, and it is easy to achieve continuous and large-scale production and automatic control of the production process. The process has now completed the laboratory research stage, and it is estimated that a set of 1,000t/a biodiesel pilot plant will require an investment of 5 million yuan. In recent years, the University of Science and Technology of China, China University of Petroleum, East China University of Science and Technology, Liaoning Energy Institute, etc. have carried out research and development work respectively. Tsinghua University has successfully developed a new process for bioenzymatic conversion of renewable oil raw materials to prepare biodiesel, breaking through the bottleneck of traditional enzymatic processes and achieving a product yield of more than 90%. The Chinese Academy of Agricultural Sciences uses azeotropic distillation glycerol esterification-methyl esterification technology to produce diesel from waste oil, achieving efficient reactions of free fatty acid esterification of waste oil and oil transesterification, and opening up a new way to convert waste oil into biodiesel. my country has made major breakthroughs in the industrialization of biodiesel. Companies such as Hainan Zhenghe, Sichuan Gushan and Fujian Zhuoyue have successively built production plants with more than 10,000 tons/a. The products have reached the quality standards of similar foreign products, and various performances are equivalent to 0# light diesel oil, marking the birth of the biodiesel industry in my country. 6 Market Prospects At present, my country's diesel consumption is about 90 million tons/a, and it relies heavily (1/3) on imports. It is expected that my country's diesel demand will exceed 100 million tons in 2010. Its sales price is about 4,600 yuan/t. If the mixing ratio of diesel and biodiesel is 80:20 (i.e. B20 standard), then the annual consumer market demand for biodiesel in my country is 18 million tons, and the total potential market is 82.8 billion yuan. At present, my country's production capacity and actual output have not exceeded 1 million t/a. According to * * It is planned that by 2010, my country's biodiesel production capacity will reach 2 million tons, and by 2020 it will reach 15 million tons. The production cost of biodiesel obtained using one-step production technology is only 3,700 to 3,900 yuan/t, so manufacturers are still profitable. At present, China’s diesel vehicles account for only 23.7% of the total car ownership, while sedans account for only 0.2%, which is far lower than that of developed countries. * * index. After experiencing explosive development during the "Tenth Five-Year Plan" period, my country's automobile industry will still maintain rapid development during the "Eleventh Five-Year Plan" period. Experts predict that by 2010, my country's automobile production will increase from 5.7 million in 2005 to 9 million, and the number of automobiles will increase from 35 million in 2005 to 60 million. By 2020, the number of cars in China will reach 150 million. In 2005, my country's crude oil production was 181.5 million tons; net imports of crude oil were 118.75 million tons, net imports of refined oil were 17.42 million tons, net oil imports for the year were 136.17 million tons, and national apparent oil consumption was 317.67 million tons. my country's oil dependence on foreign countries was 20% in 2000 and 30% in 2003. By 2005, it reached 42.9%, increasing year by year. Vehicle fuel accounts for 40% of total fuel consumption in my country. In recent years, 9 million t/a of biodiesel has been consumed to meet basic needs. The market potential is huge, and the development of biodiesel is imperative. 7 Outlook and Conclusion Recent U.S. * * A report from the Renewable Energy Laboratory (NREL) pointed out that microbial oil fermentation may be an important research direction for bioindustry and bioeconomy. Studies have shown that some oleaginous yeasts can efficiently convert five- and six-carbon sugars obtained by hydrolysis of biomass, and the oil content in the bacteria reaches more than 70% of the dry weight of the cells. New utilization of glycerol and glycerin derivatives (monoglycerides and triglycerides) produced by the esterification process: such as the production of epichlorohydrin, ethylene glycol, etc. For example, Solvay has developed the Epicerol process to produce epichlorohydrin more directly. This process uses glycerol as raw material to produce epichlorohydrin with the help of a special catalyst. Glycerin is also a raw material for many chemical products such as alkyd resins, detergents, surfactants, cosmetics and synthetic rubber. The use of microbial oil fermentation is a sustainable supply technology of oil resources with great potential and suitable for my country's national conditions. This route is a new biodiesel route that does not rely on cultivated land and oil plants. It uses biomass such as lignin fiber hydrolyzate as raw material, hydrolyzes it to obtain a cheap carbon source, uses cellulose to ferment it to obtain microbial oil, and then esterifies it to prepare biodiesel. It is necessary to accelerate technological research on oil-producing microorganisms and fermentation processes; another area that deserves great attention is the application of whole-cell biocatalysts. The development and utilization of microbial oil fermentation technology should be vigorously strengthened to ensure the sustainable development of the biodiesel industry.