Biodiesel fuel from Jatropha oil via non-catalytic supercritical methanol transesterification

Transesterification of Jatropha oil using supercritical methanol and in absence of a catalyst has been studied under different conditions of temperature (from 512 to 613 K), pressure (from 5.7 to 8.6 MPa) and molar ratio of alcohol to oil (from 10 to 43 mol alcohol per mol oil). The reaction products were analyzed for their content of residual triglycerides, glycerol, monoglycerides, diglycerides, esters and free acids by high performance liquid chromatography (HPLC), thin layer chromatography (TLC) and titration against KOH.The results have revealed that 100% yield of esters can be obtained using super critical methanol within four min only, at a temperature of 593 K and under a pressure of 8.4 MPa pressure. The molar ratio of methanol to oil was 43:1.     

Biodiesel synthesis from vegetable oils with supercritical methanol

Transesterification reactions of sunflower, rapeseed, cottonseed and cameline oils in supercritical methanol were studied in a flow reactor under equal conditions. It was found that the oil type produced insignificant effect on the product composition (fatty acid esters) and oil conversion value.     

Biodiesel production from highly unsaturated feedstock via simultaneous transesterification and partial hydrogenation in supercritical methanol

In this study, a supercritical one-pot process combining transesterification and partial hydrogenation was proposed to test its technical feasibility. Simultaneous transesterification of soybean oil and partial hydrogenation of polyunsaturated compounds over Cu catalyst in supercritical methanol was performed at 320 °C and 20 MPa. Hydrogenation proceeded simultaneously during the transesterification of soybean oil in supercritical methanol, and hydrogenation occurred during the reaction despite the absence of hydrogen gas. The polyunsaturated methyl esters obtained in the biodiesel were mainly converted to monounsaturated methyl esters by partial hydrogenation. Key properties of the partially hydrogenated methyl esters were improved and complied with standard specifications for biodiesel.     

Biodiesel from fried vegetable oils via transesterification by heterogeneous catalysis

Three solid catalysts have been tested in the transesterification of fried oils: CaO, SrO, K₃PO₄. For CaO and SrO the different efficiency, between their use as powder or granules, has been examined. Another investigated aspect has been the catalytic activity at different catalyst loadings and recycles. At the end granules have been employed in a catalytic bed reactor, comparing results with batch systems. Results have shown that using catalyst as granule does not affect the yields after 3 h of reaction. The use of the catalytic bed reactor has given the possibility to perform the transesterification maintaining the catalyst separated from the reactants, without loss of efficiency; in fact the comparison between trials in batch reactor and in catalytic bed system has not shown differences in yields. After 3 h of reaction, at 65 °C, 5 wt% of catalyst, we have had the following FAME yields: 92% for CaO, 86% for SrO, 78% for K₃PO₄. The transesterification reaction has shown a sensitive influence respect to K₃PO₄ granules amount used; in fact the yield has reached the 85% using 10 wt% of catalyst. The reutilization of the catalyst, without regeneration, has shown a loss of efficiency of about 10-20% in decreasing yield.     

废弃油脂超临界法制备生物柴油研究

以废弃油脂为原料,利用超临界法制备生物柴油.通过单因素实验及正交实验研究了醇油摩尔比、反应压力、催化剂用量、反应时间、反应温度等因素对生物柴油产率的影响.结果表明,在实验范围内各影响因素对生物柴油产率作用的大小依次为:反应温度>反应压力>催化剂用量>反应时间>醇油摩尔比.废弃油脂超临界法制备生物柴油的最佳工艺条件为:反应温度240℃,反应压力10MPa,反应时间6min,催化剂用量0.06%,醇油摩尔比40/1.在此条件下,生物柴油产率达到99.37%.     

An experimental investigation of biodiesel synthesis from waste canola oil using supercritical methanol

Synthesis of biodiesel from waste canola oil using supercritical methanol is investigated under relatively moderate reaction conditions (240–270 °C/10 MPa) with residence time of 15–45 min and methanol to oil weight ratio of 1:1, 1.5:1 or 2:1. The effects of reaction conditions on the biodiesel yield were studied using design of experiments (DOE). The results showed that reaction time, temperature, and their interaction were the most significant factors on the yield. The highest biodiesel yield of 102% was achieved at 270 °C, 10 MPa, and methanol/oil weight ratio of 2 for 45 min reaction time. The GC–MS analysis of the reaction products showed that the by-product, glycerol, further reacted with methanol, generating methyl ethers of glycerol. Further confirmation of this side reaction was obtained by reacting glycerol and methanol at 270 °C/10 MPa for 15, 30, and 45 min. The experimental results showed these reactions could positively affect the overall biodiesel yield by providing oxygenated compounds such as 3-methoxy-1,2-propanediol, dimethoxymethane, and 2,2-dimethoxypropane as well as methyl palmitate and methyl oleate.     

Biodiesel synthesis via homogeneous Lewis acid-catalyzed transesterification

Lewis acids (AlCl₃ or ZnCl₂) were used to catalyze the transesterification of canola oil with methanol in the presence of terahydrofuran (THF) as co-solvent. The conversion of canola oil into fatty acid methyl esters was monitored by ¹H NMR. NMR analysis demonstrated that AlCl₃ catalyzes both the esterification of long chain fatty acid and the transesterification of vegetable oil with methanol suggesting that the catalyst is suitable for the preparation of biodiesel from vegetable oil containing high amounts of free fatty acids. Optimization by statistical analysis showed that the conversion of triglycerides into fatty acid methyl esters using AlCl₃ as catalyst was affected by reaction time, methanol to oil molar ratio, temperature and the presence of THF as co-solvent. The optimum conditions with AlCl₃ that achieved 98% conversion were 24:1 molar ratio at 110 °C and 18 h reaction time with THF as co-solvent. The presence of THF minimized the mass transfer problem normally encountered in heterogeneous systems. ZnCl₂ was far less effective as a catalyst compared to AlCl₃, which was attributed to its lesser acidity. Nevertheless, statistical analysis showed that the conversion with the use of ZnCl₂ differs only with reaction time but not with molar ratio.     

Biodiesel production from waste frying oil in sub- and supercritical methanol on a zeolite Y solid acid catalyst

Waste frying oil (WFO) is a very important feedstock for obtaining biodiesel at low cost and using WFO in transesterification reactions to produce biodiesel helps eliminate local environmental problems. In this study biodiesel was produced from WFO in sub- and super-critical methanol on a zeolite Y solid acid catalyst. The procedure was optimized using a design of experiments by varying the methanol to WFO molar ratio, the reaction temperature, and the amount of catalyst. Typical biodiesel yields varied from 83 to nearly 100% with methyl esters content ranging from 1.41–1.66 mol·L^-1 and typical dynamic viscosities of 22.1-8.2 cP. Gas chromatography was used to determine the molecular composition of the biodiesel. The reaction products contained over 82 wt-% methyl esters, 4.2 wt-% free acids, 13.5 wt-% monoglycerides, and 0.3 wt-% diglycerides. The transesterification of WFO with methanol around its critical temperature combined with a zeolite Y as an acid catalyst is an efficient approach for the production of biodiesel with acceptable yields.     

猪板油直接萃取制备生物柴油的研究

研究了猪油原位萃取-酶法转化制生物柴油。考察了溶剂用量、萃取时间、萃取温度等对油脂得率的影响,探讨了以Novozyme 435酶为催化剂直接转化猪油生物柴油。结果表明,萃取猪油的较优参数为:乙酸甲酯为萃取剂,乙酸甲酯用量(mL)与猪板油质量(g)比为8∶1,萃取时间3 h,萃取温度50℃;以Novozyme 435脂肪酶转化猪油制备生物柴油,得率为95.12%,当Novozyme 435酶和Lipozyme TLIM酶混合比为1∶1时,生物柴油转化率最高,达97.12%。     

Biodiesel from an alkaline transesterification reaction of soybean oil using ultrasonic mixing

The feasibility of using ultrasonic mixing to obtain biodiesel from soybean oil was established. The alkaline transesterification reaction was studied at three levels of temperature and four alcohol-to-oil ratios. Excellent yields were obtained for all conditions. For example, at 40°C with ultrasonic agitation and a molar ratio of 6∶1 methanol/oil, the conversion to FAME was greater than 99.4% after about 15 min. For a 6∶1 methanol/oil ratio and a 25 to 60°C temperature range, a pseudo second-order kinetic model was confirmed for the hydrolysis of DG and TG. Reaction rate constants were three to five times higher than those reported in the literature for, mechanical agitation. We suspect that the observed mass transfer and kinetic rate enhancements were due to the increase in interfacial area and activity of the microscopic and macroscopic bubbles formed when ultrasonic waves of 20 kHz were applied to a two-phase reaction system.     

Continuous production of biodiesel fuel from vegetable oil using supercritical methanol process

A system for continuous transesterification of vegetable oil using supercritical methanol was developed using a tube reactor. Increasing the proportion of methanol, reaction pressure and reaction temperature can enhance the production yield effectively. However, side reactions of unsaturated fatty acid methyl esters (FAME) occur when the reaction temperature is over 300 °C, which lead to much loss of material. There is also a critical value of residence time at high reaction temperature, and the production yield will decrease if the residence time surpasses this value. The optimal reaction condition under constant reaction temperature process is: 40:1 of the molar ratio of alcohol to oil, 25 min of residence time, 35 MPa and 310 °C. However, the maximum production yield can only be 77% in the optimal reaction condition of constant reaction temperature process because of the loss caused by the side reactions of unsaturated FAME at high reaction temperature. To solve this problem, we proposed a new technology: gradual heating that can effectively reduce the loss caused by the side reactions of unsaturated FAME at high reaction temperature. With the new reaction technology, the methyl esters yield can be more than 96%.     

Palm oil transesterification in sub- and supercritical methanol with heterogeneous base catalyst

An environmentally benign process for the production of methyl ester using γ-alumina supported heterogeneous base catalyst in sub- and supercritical methanol has been developed. The production of methyl ester in refluxed methanol conventionally utilized double promoted γ-alumina heterogeneous base catalyst (CaO/KI/γ-alumina); however, this process requires a large amount of catalyst and a long reaction time to produce a high yield of methyl ester. This study carries out methyl ester production in sub- and supercritical methanol with the introduction of an optimized catalyst used in the previous work for the purpose of improving the process and enhancing efficiency. CaO/KI/γ-Al₂O₃ catalyst was prepared by precipitation and impregnation methods. The effects of catalyst amount, reaction temperature, reaction time, and the ratio of oil to methanol on the yield of biodiesel ester were studied. The reaction was carried out in a batch reactor (8.8 ml capacity, stainless steel, AKICO, Japan). Results show that the use of CaO/KI/γ-Al₂O₃ catalyst effectively reduces both reaction time and required catalyst amount. The optimum process conditions were at a temperature of 290 °C, ratio of oil to methanol of 1:24, and a catalyst amount of 3% over 60 min of reaction time. The highest yield of biodiesel obtained under these optimum conditions was almost 95%.     

Process simulation and economic analysis of biodiesel production processes using fresh and waste vegetable oil and supercritical methanol

Three continuous biodiesel processes with production capacity of 40,000 tonne/yr, including a conventional alkali-catalyzed process using both fresh and waste vegetable oil and a supercritical methanol process using waste vegetable oil as the raw material, were simulated in HYSYS. In order to improve the simulation accuracy, the properties of triolein, a model compound of vegetable oil, were re-evaluated. The normal boiling point of triolein was experimentally determined by thermogravimetric analysis and further incorporated in HYSYS simulation, which resulted in improvements in the values of specific heat capacity, mass density, and viscosity. Process economics were analyzed using Aspen In-Plant Cost Estimator. The alkali-catalyzed process using fresh vegetable oil had the lowest total capital investment, but the supercritical process was the most economically feasible overall, providing a lower manufacturing cost and higher net present value and a discounted cash flow rate of return. Sensitivity analyses of net present value were conducted using four parameters including oil feedstock costs, glycerol credit, biodiesel selling prices, and interest rates. Based on the analyses, prediction equations of net present value were developed.     

Biodiesel production using supercritical alcohols with a non-edible vegetable oil in a batch reactor

In the present work, the transesterification of non-edible oil with methanol and ethanol is studied. The reactor phase transitions are directly observed in a double windowed cylindrical reactor and the conversion to fatty esters is measured. The optimization of the process conditions was carried out based on a statistical design of experiments where the key process variables were studied over different ranges to obtain a reliable model for the efficiency of the reaction as a function of reaction time, temperature, pressure and alcohol to oil molar ratio. From direct observations and the modeling of the phase behavior, a better understanding of the supercritical alcohol transesterification process is obtained as well as the confirmation of the phase equilibrium predictions based on the GCA-EOS model.     

大豆油与甲醇酯交换反应体系的相平衡研究

生物柴油是一类清洁的可再生液体燃料,精炼植物油与甲醇酯交换是制备生物柴油的重要反应。针对目前难以准确获得酯交换反应体系的多组分相平衡组成等方面存在的问题,研究了间歇反应和连续逆流分离甘油等不同反应方式下大豆油与甲醇酯交换反应体系的多组分相平衡行为,并以三油酸甘油酯与甲醇酯交换为模型反应,采用UNIFAC和Modified UNIFAC模型进行了模拟计算。结果表明,在常压、60^oC反应条件下,在总组成偏离甲醇-甲酯二元组成的区域,UNIFAC和Modified UNIFAC模型准确计算了生物柴油酯交换反应体系的三元和四元相平衡组成。在甘油含量大于2.2%(质量)或转化率小于90%(质量)的酯交换反应中,计算值与实验值的平均偏差约为2%。酯交换反应相平衡的实验值和模型计算值表明,采用连续逆流方式分离甘油可以提高酯相中的甲醇含量,有利于传质和酯交换反应。这些结果为生物柴油工艺过程模拟、设备优化以及新技术开发提供了理论参考。     

Simplification of separation of the reaction mixture after transesterification of vegetable oil

A heterogeneous reaction mixture is formed by transesterification of vegetable oils. The reaction mixture contains mainly methyl esters of higher fatty acids and glycerol. From this mixture, biodiesel is gained by spontaneous sedimentation in the gravitational field. The sedimentation can be considerably accelerated by controlled addition of water. It was found that addition of small amounts of water to the crude reaction mixture significantly affected the mixture, and substantial changes in the speed of the separation took place. Considerable differences in the composition and quality of the ester and glycerol phases occurred. The optical properties (transmittance and refractive indices) of the heterogeneous reaction mixture are changed after addition of water; this change can be observed spectrophotometrically. This method is applicable to all types of vegetable oils including waste frying oils.     

Catalytic transesterification of crude rapeseed oil by liquid organic amine and co-catalyst in supercritical methanol

Liquid organic amines, Ethylenediamine (EDA), Diethylamine (DEA) or Triethylamine (TEA), could speed up the production of methyl ester from crude rapeseed oil in supercritical methanol. The order of the catalytic activity was EDA > DEA > TEA. Acyl amine appeared in the products when EDA or DEA was used as the catalyst; however, this phenomenon didn’t occur when TEA was used. With Propylene oxide as the co-catalyst, the catalytic activity of TEA was greatly improved. In 10 min, the yield of methyl ester could reach 89.5%, which was seven times faster than that without the co-catalyst. Optimum molar ratio of methanol to crude rapeseed oil should not be lower than 24:1.     

Biodiesel production from waste cooking oil via alkali catalyst and its engine test

Waste cooking oils (WCO), which contain large amounts of free fatty acids produced in restaurants, are collected by the environmental protection agency in the main cities of China and should be disposed in a suitable way. Biodiesel production from WCO was studied in this paper through experimental investigation of reaction conditions such as methanol/oil molar ratio, alkaline catalyst amount, reaction time and reaction temperature which are deemed to have main impact on reaction conversion efficiency. Experiments have been performed to determine the optimum conditions for this transesterification process by orthogonal analysis of parameters in a four-factor and three-level test. The optimum experimental conditions, which were obtained from the orthogonal test, were methanol/oil molar ratio 9:1, with 1.0 wt.% sodium hydroxide, temperature of 50 °C and 90 min. Verified experiments showed methanol/oil molar ratio 6:1 was more suitable in the process, and under that condition WCO conversion efficiency led to 89.8% and the physical and chemical properties of biodiesel sample satisfied the requirement of relevant international standards. After the analysis main characteristics of biodiese sample, the impact of biodiesel/diesel blend fuels on an YC6M220G turbo-charge diesel engine exhaust emissions was evaluated compared with 0# diesel. The testing results show without any modification to diesel engine, under all conditions dynamical performance kept normal, and the B20, B50 blend fuels (include 20%, 50% crude biodiesel respectively) led to unsatisfactory emissions whilst the B′20 blend fuel (include 20% refined biodiesel) reduced significantly particles, HC and CO etc. emissions. For example CO, HC and particles were reduced by 18.6%, 26.7% and 20.58%, respectively.     

Biodiesel from minor vegetable oils like karanja oil and nahor oil

The present study investigated the scope of two minor vegetable oils, i.e. karanja (Pongamia glabra) oil and nahor (Mesua ferrea L., Guttiferae) oil, as raw material for biodiesel fuel. The distilled fatty acid methyl esters obtained from karanja oil and nahor oil have the following characteristics: cetane indices 56.2, 54.6; heat of combustion (kcal/mol) 8.26, 8.39; flash points (°C) 134, 142; cloud points (°C) 8.3, 6.1, respectively. All these properties of the distilled methyl esters reveal that karanja oil and nahor oil can be suitably used as cheap raw material for the synthesis of biodiesel.     

Synthesis of biodiesel from edible,non-edible and waste cooking oils via supercritical methyl acetate transesterification

The use of methyl acetate instead of methanol for supercritical synthesis of glycerol-free biodiesel from vegetable oils is a new process and its study is very limited in the literature. In this work, it has been tested for the first time on three edible and non-edible oils with different fatty acid composition. The process was also applied to waste oil with higher free fatty acid (FFA) content. The results demonstrate that the oil composition does not significantly influence the biodiesel yield.The influence of temperature, pressure and molar ratio of reactants was studied. All the oils achieved complete conversion after 50 min at 345 °C, 20 MPa with methyl acetate:oil molar ratio equal to 42:1. The obtained data also allowed calculating the apparent rate coefficients and activation energies.Eventually, some new information on the process was obtained. Thermal degradation of triacetin, which substitutes glycerol as the by-product of the transesterification reaction, was observed. Some indicative experiments were performed to understand the role of the acetic acid produced by FFA esterification.