生物柴油的应用研究进展

综述了国内外生物柴油的应用和生产现状,介绍了生物柴油的主要特性以及直接混合、微乳液、高温热裂解、化学酯交换、生物酶催化和超临界甲醇法等生产生物柴油的方法,阐述了我国发展生物柴油的重要意义,并提出了我国发展生物柴油技术的建议。     

脂肪酶催化合成生物柴油的研究

生物柴油是用动植物油脂或长链脂肪酸与甲醇等低碳醇合成的脂肪酸甲酯,是一种替代能源。这里探讨了生物法制备生物柴油的过程,采用脂肪酶酯化和酯交换两条工艺路线进行催化合成。深入研究制备过程中,不同脂肪酶、酶的用量和纯度、有机溶剂、低碳醇的抑制作用、吸水剂的作用、反应时间和进程、底物的特异性和底物摩尔比等参数对酯化过程的影响。试验结果表明,采用最佳酯化反应参数和分批加入甲醇并用硅胶作脱水剂的工艺过程,酯化率可以达到92％,经分离纯化后的产品GC分析的纯度可达98％以上,固定化酶的使用半衰期可达到360h。同时对酯交换制备生物柴油过程中,甲醇的用量和甲醇的加入方式对脂肪酶催化过程的影响作了初步研究,优化后的酯交换率可达到83％。     

脂肪酶催化合成生物柴油的瓶颈问题及其对策研究进展

生物柴油,一种新型的清洁能源燃料,具有可再生、可生物降解、环境友好等优良的品性,可部分或全部替代石化柴油。碱催化法、脂肪酶催化法及超临界法是合成生物柴油的主要工艺,其中脂肪酶催化法是一种节能型、环保型工艺,在节能和环保方面,有着碱催化法无可比拟的优越性,具有良好的工业应用前景。但目前在实现产业化的进程中仍存在如酶成本高、稳定性较差、甲醇对酶的失活效应及反应时间长等瓶颈问题。通过固定化技术和全细胞催化剂的采用、甲醇流加方式的改进、溶剂工程的改善及酰基受体和耐醇酶的开发等技术手段,结合固定床生物反应器,较好地解决了这些瓶颈问题,从而推进了酶催化法合成生物柴油的工业化进程。本文主要对酶法合成生物柴油工艺存在的主要问题及相应对策研究进展进行概括介绍,并对其工业化发展前景进行讨论。     

超临界流体技术制备生物柴油进展及前景

超临界流体技术制备生物柴油不使用催化剂,生产过程清洁环保,是极具发展潜力的绿色可再生能源生产技术。本文首先简述超临界流体的特点及其用于生物柴油制备的物理、化学基础;其次详细分析超临界流体技术制备生物柴油的过程中反应温度、反应压力、醇油摩尔比、低碳醇种类、水、脂肪酸、反应器及反应形式等工艺控制条件对反应的影响和原因,并介绍超临界流体制备生物柴油中的过程强化方法和技术经济性。尽管超临界流体制备生物柴油具有原料适应性好、投资和运行成本低、生产过程清洁等优点,但存在反应条件苛刻、甲醇用量高等问题,从工业化角度指出使用廉价废弃油脂原料降成本、调节原料酸值降低反应苛刻度、连续化和大型化是超临界流体制备生物柴油技术的重点提升方向。     

荧光假单胞菌脂肪酶固定化及催化制备生物柴油的工艺研究

研究了不同因素对制备固定化荧光假单胞菌脂肪酶的影响及固定化酶的酶学性质,并初步探讨了利用该固定化酶制备生物柴油的工艺。以海藻酸钠明胶为复合载体,采用包埋法制备固定化荧光假单胞菌脂肪酶,考察了载酶量、颗粒直径等因子对固定化效果的影响,并用制备的固定化酶进行了酶促酯交换合成生物柴油的工艺研究,考察了反应条件如酶量、反应温度、甲醇流加方式、醇油比等因素对甲酯得率的影响。试验结果表明,制备固定化荧光假单胞菌脂肪酶的最优条件为:每克载体给酶量为300 IU,选用6号注射器针头(内径为0.5 mm);通过酯交换,催化大豆油合成生物柴油的最佳反应工艺参数为:固定化酶25%,醇油比4:1,含水量6%,反应温度40℃;此条件下反应35 h后,甲酯的最高得率可达82%。     

几种离子液体的微波法合成及其对脂肪酶催化效果的影响

采用微波法合成9种目标离子液体,对中间体[Bmim]Br的合成条件及其离子液体对全细胞催化剂催化效果的影响进行考察.直接将产脂肪酶真菌粗状假丝酵母(Candida valida) T2细胞固定在聚氨酯颗粒中,制备固定化细胞催化剂,将其应用于合成离子液体介质中催化甲醇与大豆油酯交换反应制备生物柴油.结果表明:微波功率200 W下间隙照射100 s,中间体[Bmim]Br的收率达95.16%,有效地提高了离子液合成产率;在[Bmim]PF6离子液中固定化细胞酶催化转酯化反应30 h,大豆油的转化率达42%,反应效果较其他8种合成离子液体好;固定化细胞颗粒和[Bmim]PF6重复使用4次,其油脂转化率和酶活保持率分别达到29%和69%,表现出较好的催化反应稳定性.     

固定化脂肪酶催化制备生物柴油条件优化

本文探讨了以固定化脂肪酶为催化剂催化制备生物柴油中醇油比、水含量、游离脂肪酸酸值和催化剂使用寿命对菜子油酯交换反应的影响,并与以NaOH、固体碱纳米水滑石为催化剂生物柴油的制备条件相比较.研究表明:固定化脂肪酶为催化剂所需最佳醇油比最低,仅为4:1,游离脂肪酸含量对酯交换反应影响甚微,且有较强的抗水性,固定化脂肪酶催化剂可可重复使用6次;NaOH为催化剂酯交换反应抗水性最强,随游离脂肪酸的增加,酯交换转化率显著降低;纳米水滑石为催化剂可重复使用5次,酯交换产物易分离,所得产品完全符合德国生物柴油标准.     

微水相超声波协同固定化脂肪酶催化酯交换过程优化

超声波协同固定化脂肪酶催化制备生物柴油的最佳工艺条件为：超声波功率70W、叔丁醇为反应介质、叔丁醇用量3％（v／v）、醇油比3：1且甲醇分三批加入、反应温度40℃、水含量为2％（v／v）。副产物甘油对固定化脂肪酶使用寿命影响最大,使用后的固定化脂肪酶用丙酮洗去表面的甘油,进行酯交换反应,酶的稳定性大为提高,可连续使用16批次。     

最新专利文摘

CN101108975:耦合制备蓖麻油生物柴油的方法本发明公开了一种“浸出+反应”耦合法制备蓖麻油生物柴油的方法。以蓖麻籽为原料,在超声条件下或无物理场作用条件下,蓖麻油浸出与酯交换反应耦合制备生物柴油。浸出与酯交换反应一步完成,极大地简化工艺流程,节约生产成本;甲醇既为浸出溶剂又为酯交换剂,有利于循环和节约原料,也有利于后期物料的分离。解决了现有的生物柴油制备方法对油脂的质量要求较高,工艺路线较长,各种原料、试剂及设备消耗较大,试剂污染也比较严重,生产成本比较高的问题。CN101108976:一种生物柴油及其制备方法本发明涉及一种生物柴油及其制备方法。生物柴油在制备过程中,将原料油和预处理剂按一定比例在预处理装置中,加热搅拌反应后,过滤,进入预脂化装置中再添加酸性催化剂和粗甘油,加热、搅拌,循环后进入脂化装置中,加甲醇和碱性催化剂或酸性催化剂,加热,加速循环反应后,回收甲醇,放出甘油和分离出皂化物,得到的生物柴油水洗后蒸馏即可完成。所得的生物柴油产品满足现行德国、美国和我国新实行的《GB/T20802~2007》标准。不仅节约了能源,且甲醇、催化剂等消耗量少,能耗低,适用于各种原料油,经济性价比高,工艺简单...     

微生物途径发展生物柴油产业

生物柴油实际上就是生物油脂与甲醇或乙醇在酸、碱催化剂的作用下进行脂交换反应而制造的脂肪酸甲酯或乙酯;也可以在常温下由微生物脂酶催化进行酯化反应,其产品是一种可再生燃料,能替代石油柴油。这些生物柴油主要来自植物油或其它生物油脂,也有用废弃食用油为原料通过甲醇的酯交换反应来制造生物柴油的。研发这些生物柴油也可以说是节能的一项重要措施。在我国,对石油的需求量越来越大,石油进口量也随之猛增,显示出我国的能源形势日益严峻。面对这种情况,发展可再生能源或替代能源是个必然趋势,生物柴油便是其中之一。目前我国生物柴油的…     

Dimethyl carbonate as potential reactant in non-catalytic biodiesel production by supercritical method

In this study, the non-catalytic supercritical method has been studied in utilizing dimethyl carbonate. It was demonstrated that, the supercritical dimethyl carbonate process without any catalysts applied, converted triglycerides to fatty acid methyl esters with glycerol carbonate and citramalic acid as by-products, while free fatty acids were converted to fatty acid methyl esters with glyoxal. After 12 min of reaction at 350 degrees C/20 MPa, rapeseed oil treated with supercritical dimethyl carbonate reached 94% (w/w) yield of fatty acid methyl ester. The by-products from this process which are glycerol carbonate and citramalic acid are much higher in value than glycerol produced by the conventional process. In addition, the yield of the fatty acid methyl esters as biodiesel was almost at par with supercritical methanol method. Therefore, supercritical dimethyl carbonate process can be a good candidate as an alternative biodiesel production process.     

Biodiesel production by supercritical process with crude bio-methanol prepared by wood gasification

In order to prepare a genuine biodiesel, it is essential to use methanol prepared from biomass but not natural gas for biodiesel production. Thus, we have proposed to use crude bio-methanol produced by wood gasification for biodiesel production. Since such a bio-methanol contains some impurities, an effect of its impurities was studied on the biodiesel production by supercritical method. In general, impurities in crude bio-methanol are reported to include methyl formate, ethanol, 1-butanol, diisopropyl ether, water, etc. Triglycerides and oleic acids were, thus, treated with these impurities under supercritical conditions. As a result, it was found that methyl formate, ethanol and 1-butanol could convert them to fatty acid alkyl esters (BDF), whereas no conversion was achieved with diisopropyl ether. Thus, crude bio-methanol can be used for BDF production as a substitute for methanol from fossil resources. However, due to more efficient reaction, crude bio-methanol can be more applicable to the two-step supercritical methanol process, consisting of hydrolysis of triglycerides and subsequent esterification of fatty acids, compared with the one-step supercritical methanol process, where transesterification of triglycerides is a major reaction.     

Enzymatic reaction kinetic: comparison in an organic solvent and in supercritical carbon dioxide

Myristic acid esterification has been performed by an immobilized lipase from Mucor Miehei both in n-hexane and in supercritical carbon dioxide (SCCO(2)). The enzyme is stable in SCCO(2) at 15 MPa and 323 K. The reaction rate is influenced by the concentration of water and by the reaction medium composition. A reaction mechanism is proposed, and kinetic parameters are determined at 12.5 MPa and 313 K. Maxium velocity appears 1.5-fold higher in SCCO(2) than in n-hexane; however, as solubility of myristic acid is greater in n-hexane, it is not yet definitively clear that the supercritical medium is more favorable than the classical organic solvent for this type of enzyme reaction.     

Determination of food constituents based on SFE: applications to vitamins A and E in meat and milk

A method has been developed for the determination of vitamins A and E in food using supercritical fluid extraction (SFE), applying liquid or solid trapping, with an accuracy equal to conventional solvent extraction methods. Under optimal conditions, using methanol modified carbon dioxide as a supercritical fluid, Hydromatrix as a water adsorbent, and with a small amount of ascorbic acid and methanol added to the sample, the extraction time is reduced to 80 min. This time is considerably shorter than in conventional methods. Other advantages are the reduction of manual manipulations leading to lower labour costs and reduced consumption of organic solvents in the sample preparation step.     

超临界水处理生物质制氢技术

简要论述了工业制氢的常用方法及各自的优缺点。基于目前国际上的最新研究动向,重点就超临界水催化汽化生物质制氢技术的研究现状进行了归纳和综述。认为超临界水催化生物质制氢技术具有环境友好、资源可再生以及效率高等技术优势,具有良好开发前景,应该予以重视。重点讨论了目前研究工作所取得的成果、面临的主要技术问题和可能的解决途径,指出了未来的重点研究方向。     

Sonication-assisted production of biodiesel using soybean oil and supercritical methanol

High temperature and pressure are generally required to produce biodiesel using supercritical methanol. We reduced the harsh reaction conditions by means of sonicating the reaction mixture prior to transesterification using supercritical methanol. Soybean oil was selected as the raw material for transesterification. As soybean oil contains more unsaturated fatty acid triglycerides, the biodiesel degraded more at high temperature. The reactants were sonicated for 60 min at 35 °C prior to transesterification to avoid degradation of the product and to enhance biodiesel yield at temperatures <300 °C. The process parameters were optimized using central composite design. The variables selected for optimization were temperature, time, and the oil to methanol molar ratio. The temperature and oil to methanol molar ratios were varied from 250 to 280 °C and 1:40–1:50, respectively. The reaction time was tested between 4 and 12 min. The biodiesel was analyzed for any possible degradation by gas chromatography–mass spectroscopy and for the wt% of fatty acid methyl esters (FAME) obtained. The maximum FAME yield (84.2 wt%) was obtained at a temperature of 265.7 °C, an oil to alcohol molar ratio of 1:44.7, and a time of 8.8 min. The optimum yield was obtained at a pressure of 1,500 psi. The pressure and optimum temperature used to obtain the maximum yield were the lowest reported so far without the use of a co-solvent. Thus, the severity of the supercritical reactions was reduced by adding sonication prior to the reaction.     

Lipase Catalysed Esterification at High Pressure

From the comparation of esterification between oleic acid and oleyl alcohol, catalyzed by the Mucor miehei immobilized lipase in a batch stirred tank reactor, in a solvent free system and system where the solvent was supercritical carbon dioxide it is obvious that reaction rates are higher at supercritical conditions than in the solvent free system. To obtain the data on the solubility of substrates and product (oleyl oleate) in supercritical carbon dioxide, fluid phase equilibria measurements in the static equilibrium cell have been done. The results showed that the temperature change between 30 d`C and 50 d`C doesn't affect the solubility of the substances in SC CO₂ very much, but with higher pressure (between 100 and 300 bar) the solubilities of oleic acid, oleyl alcohol and oleyl oleate slightly increase. From the data it is obvious that oleic acid and oleyl alcohol have better solubility in supercritical CO₂ than oleyl oleate and therefore the separation of both substrates from oleyl oleate with supercritical CO₂ is possible-Key words: esterification, supercritical fluids, lipase.     

Supercritical carbon dioxide extraction of colchicine and related alkaloids from seeds of Colchicum autumnale L

A method for the extraction of the alkaloids colchicine, 3-demethylcolchicine and colchicoside from seeds of Colchicum autumnale by supercritical carbon dioxide has been established. Several parameters such as pressure, temperature, percentage of modifier and extraction time have been examined. Two extraction steps with constant carbon dioxide density (0.90 g/mL) and flux (1.5 mL/min) were required to extract the alkaloids in 110 min using 3% methanol as modifier. The quantitative determination of the alkaloids was performed by HPLC; the percentages of recovery were higher than 98% for the three alkaloids. This extraction procedure was compared with a conventional method involving maceration and sonication, and the same levels of alkaloids were obtained in each case. The supercritical carbon dioxide method is, however, very efficient, more rapid and more environmentally friendly than conventional methods.     

Reactivity of triglycerides and fatty acids of rapeseed oil in supercritical alcohols

A catalyst-free biodiesel production method with supercritical methanol has been developed that allows a simple process and high yield because of simultaneous transesterification of triglycerides and methyl esterification of fatty acids. From these lines of evidence, we expected that similar results would be attained with the use of various alcohols by the supercritical treatment. However, it still remains unclear which type of reaction, transesterification or alkyl esterification, is faster. This parameter would be important in designing the optimum reaction conditions of the supercritical alcohol method. Therefore, we studied the effect of transesterification of triglycerides and esterification of fatty acids in rapeseed oil. Reaction temperature was set at 300 degrees C, and methanol, ethanol, 1-propanol, 1-butanol or 1-octanol was used as the reactant. The results showed that transesterification of triglycerides (rapeseed oil) was slower in reaction rates than alkyl esterification of fatty acids for any of the alcohols employed. Furthermore, saturated fatty acids such as palmitic and stearic acids had slightly lower reactivity than that of the unsaturated fatty acids; oleic, linoleic and linolenic.     

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10^-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.