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 production through transesterification over natural calciums

Transesterification of palm kernel oil (PKO) with methanol over various natural calciums, including limestone calcite, cuttlebone, dolomite, hydroxyapatite, and dicalcium phosphate, has been investigated at 60 °C and 1 atm. The study showed that dolomite, mainly consisting of CaCO₃ and MgCO₃, is the most active catalyst. The calcination temperature largely affected the physicochemical properties, as evidenced by N₂ adsorption-desorption measurement, TGA, SEM and XRD, and the transesterification performance of the resultant catalysts. It was found that the calcination of dolomite at 800 °C resulted in a highly active mixed oxide. CaO was suggested to be the catalytically active site responsible for the methyl ester formation. Under the suitable reaction conditions, the amount of dolomite calcined at 800 °C = 6 wt.% based on the weight of oil, the methanol/oil molar ratio = 30, and the reaction time = 3 h, the methyl ester content of 98.0% can be achieved. The calcined dolomite can be reused many times. The analyses of some important fuel properties indicated that the biodiesel produced had the properties that meet the standard of biodiesel and diesel fuel issued by the Department of Energy Business, Ministry of Energy, Thailand.     

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.     

Acid-Catalyzed Homogeneous Esterification Reaction for Biodiesel Production from Palm Fatty Acids

This work deals with esterification of palm fatty acids to produce biodiesel in a batch reactor, using homogeneous acid catalysts, evaluating the effect of the alcohol used, presence of water, type and concentration of catalysts. Methanesulfonic and sulfuric acid were the best catalysts. Reaction with methanol showed greater yields. It was showed very clearly that the presence of water in the reaction medium showed a negative effect in the reaction velocity. Kinetic parameters were estimated and molecular modeling was performed. Protonation of the carboxylic moiety of the fatty acid were defined as rate determinant step for the reaction.     

Feasibility of Palm Oil as the Feedstock for Biodiesel Production via Heterogeneous Transesterification

The production of biodiesel has become popular recently as a result of increasing demand for a clean, safe and renewable energy. Biodiesel is made from natural renewable sources such as vegetable oils and animal fats. The conventional method of producing biodiesel is by reacting vegetable oil with alcohol in the presence of a homogenous catalyst (NaOH). However, this conventional method has some limitations such as the formation of soap, usage of significant quantities of wash water and complicated separation processes. Heterogeneous processes using solid catalysts have significant advantages over homogenous methods. Currently, more than 90 % of world biodiesel is produced using rapeseed oil. The production of biodiesel from rapeseed oil is considered uneconomical, considering the fact that palm oil is currently the world's cheapest vegetable oil. Therefore, the focus of this study is to show the feasibility of producing biodiesel from palm oil using montmorillonite KSF as a heterogeneous catalyst. The heterogeneous transesterification process was studied using design of experiment (DOE), specifically response surface methodology (RSM) based on a four‐variable central composite design (CCD) with α = 2. The transesterification process variables were reaction temperature, x₁ (50–190 °C), reaction period, x₂ (60–300 min), methanol/oil ratio, x₃ (4–12 mol mol^–1) and the amount of catalyst, x₄ (1–5 wt %). It was found that the conversion of palm oil to biodiesel can reach up to 78.7 % using the following reaction conditions: reaction temperature of 155 °C, reaction period of 120 min, ratio of methanol/oil at 10:1 mol mol^–1 and amount of catalyst at 4 wt %. From this study, it was shown that montmorillonite KSF catalyst can be used as a solid catalyst for biodiesel production from palm oil.     

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.     

Biodiesel production in a jet flow stirred reactor

The rate of biodiesel formation was assessed in a transesterification reactor stirred with a dual jet flow close loop. A blend of 85% of soybean and 15% of sunflower oil, methanol and NaOH were used to study the rate of conversion from vegetable oil to methyl esters. A 9 l cylindrical reactor with conical bottom discharge connected to two centrifugal pumps for fluid recirculation through dual opposite radial jet flows in its upper part was developed for the experiment. The system did not require a heating supply due that the frictional effect inside the recirculation hoses and nozzles produced self heating of the inlet fluid to the reactor. Four different diameters of ejector corresponding to initial Reynolds Number (Re) ranging between 1300 and 6470 were tested to assess the reactor heating profile along with the kinetics of biodiesel formation. Clear performance differences among ejector diameters and Reynolds Number values were observed showing that higher Re result in low relative conversion times along with higher final temperature in the reactor. For 98% of relative conversion to biodiesel, the ejector with Re = 6470 showed 88% reduction in transesterification time with respect to an ejector delivering a Re = 1300 and without requiring any external heat source.     

ZS／HY-SBA-15负载型固体酸催化合成生物柴油

以四水硫酸锆改性HY-SBA-15（ZS／HVSBA-15）为催化剂,催化大豆油和甲醇制备生物柴油,考察最佳制备条件。实验结果表明,四水硫酸锆负载量为30％,n（甲醇）：n（大豆油）-12：1,m（催化剂）：m（大豆油）=3％,m（溶剂）：m（大豆油）：30％,120℃下反应6h,生物柴油的收率可达96．78％。对合成出的生物柴油性能指标进行检测,结果表明其主要性能指标与我国0^#柴油相接近。     

Soybean oil transesterification over zinc oxide modified with alkali earth metals

Fatty acid methyl esters, derived from vegetable oils or animal fats and better known as biodiesel, have received considerable attention because of their environmental benefits and the limited resources of fossil fuels. Most biodiesel is usually produced by the transesterification of vegetable oils with methanol in the presence of a catalyst. This study reports on the preliminary results of using alkaline earth metal-doped zinc oxide as a heterogeneous catalyst for transesterification of soybean oil. The highest catalytic activity was obtained with ZnO loaded with 2.5 mmol Sr(NO₃)₂/g, followed by calcination at 873 K for 5 h. When the transesterification reaction was carried out at reflux of methanol (338 K), with a 12:1 molar ratio of methanol to soybean oil and a catalyst amount of 5 wt.%, the conversion of soybean oil was 94.7%. Besides, tetrahydrofuran (THF), when used as a co-solvent, could increase the conversion up to 96.8%. However, the recovered catalyst exhibited the lower catalytic activity with a conversion of soybean oil of 15.4%. Furthermore, DTA-TG, IR and the Hammett indicator method were employed for the catalyst characterizations.     

生物柴油应用研究进展

简要综述了生物柴油应用研究进展,着重介绍了高酸值原料生产工艺,讨论认为原料应充分利用废食用油或工业油脂,固体酸、碱催化法工艺是当前最佳发展点,长期趋势为微生物油脂固体催化剂工艺或酶催化的联合工艺。     

Economic and ecological aspects of biodiesel production over homogeneous and heterogeneous catalysts

The objective of this paper is to highlight the economic and ecological differences of biodiesel production over homogeneous and heterogeneous catalysts in large-scale industrial plants. Comparative economic assessment of the two processes revealed the advantage of the heterogeneous process in terms of higher yield of biodiesel and higher purity of glycerine, lower cost of catalyst and maintenance, with an estimated cumulative impact on the reduction of the operating cost of US$59 per tonne of biodiesel, relative to the homogeneous process. The biggest challenge for its economic competitiveness is its higher energy consumption. The analysis showed that if the energy costs are below US$85 per tonne of biodiesel, the heterogeneous process can be economically viable. The environmental benefits of the heterogeneous process include absence of strong acids and of energy intensive and waste generating glycerine purification step. However, its application would contribute to depletion of fossil energy resources and higher emission of greenhouse gases due to higher energy and methanol consumption.     

Optimization of the transesterification reaction in biodiesel production

In this paper response surface methodology (RSM) was used to study the transesterification reaction of rapeseed oil for biodiesel production. The three main factors that drive the conversion of triglycerides into fatty acid methyl esters (FAME) were studied according to a full factorial design at two levels. These factors were catalyst concentration (KOH), temperature and reaction time. The range investigated for each factor was selected taking into account the process of Fox Petroli S.p.A. Analysis of variance (ANOVA) was used to determine the significance of the factors and their interactions which primarily affect the first of the two transesterification stages. This analysis evidenced the best operating conditions of the first transesterification reaction performed at Fox’s plant: KOH concentration 0.6% w/w, temperature 50 °C and reaction time 90 min with a CH₃OH to KOH ratio equal to 60. Three empirical models were derived to correlate the experimental results, suitable to predict the behavior of triglyceride, diglyceride and monoglyceride concentration. These models showed a good agreement with the experimental results, demonstrating that this methodology may be useful for industrial process optimization.     

Theoretical study of the transesterification of triglycerides to biodiesel fuel

The transesterification of various triglycerides was considered in terms of the activation energy obtained from quantum computational chemistry. According to these values, the effect upon the reactivity of the structure of the triglyceride is not particularly large. Moreover, the transesterification reaction is completed via a transition state, in which ring formation consisting of the carbon of the carboxyl and alkoxy groups appears, even if a long-chain alcohol is used as a reactant. Finally, an ideal reaction pathway, in which the ester bond at the center of the triglyceride is transesterified before peripheral ester bonds, was shown by an activation energy analysis and electrostatic potential (ESP) distribution.     

Potassium leaching during triglyceride transesterification using K/γ-Al2O3 catalysts

A K/γ-Al₂O₃ catalyst was prepared using the wet impregnation method with K₂CO₃ as a precursor salt. During the activation process, a clear interaction between potassium carbonate-derived species and the support took place resulting in the formation of K aluminate-like species, as observed by evolved gas analysis by mass spectrometry (EGA-MS) and infrared spectroscopy (FTIR). This catalyst was tested in the transesterification of sunflower oil with methanol, achieving a methyl ester yield close to 100% after 1 h. However, when it was used in successive runs the catalyst showed a strong decrease in its catalytic performance. It is established experimentally that the performance in the first run was mainly due to a homogeneous contribution from active basic species dissolved in methanol. The leaching of potassium species in the reaction media was not avoided although a clear interaction between active phase and support was observed. The present work stresses the obligation of the reutilization and of the verification of the leaching of active species in analogous catalytic systems based on alkaline and alkaline-earth metal oxides when used in the transesterification reaction with methanol.     

Advances on the development of novel heterogeneous catalysts for transesterification of triglycerides in biodiesel

This paper describes experimental work done towards the search for more profitable and sustainable alternatives regarding biodiesel production, using heterogeneous catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction. This experimental work is a first stage on the development and optimization of new solid catalysts, able to produce biodiesel from vegetable oils. The heterogeneous catalytic process has many differences from the currently used in industry homogeneous process. The main advantage is that, it requires lower investment costs, since no need for separation steps of methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This work resulted in the selection of CaO and CaO modified with Li catalysts, which showed very good catalytic performances with high activity and stability. In fact FAME yields higher than 92% were observed in two consecutive reaction batches without expensive intermediate reactivation procedures. Therefore, those catalysts appear to be suitable for biodiesel production.     

Regioselective synthesis of pentacyclic heterocycles by the thermal and Lewis acid catalyzed Claisen rearrangement

[6,6]- and [6,5]-fused hithero unreported pentacyclic heterocycles have been regioselectively synthesized from 4-(4′-aryloxybut-2′-ynylthio)thiocoumarin in good yields by the application of thermal as well as catalytic Claisen rearrangement.     

Biodiesel production using supercritical methanol/carbon dioxide mixtures in a continuous reactor

Fatty acid methyl esters (biodiesel) were produced by the transesterification of triglycerides with compressed methanol (critical point at 240 °C and 81 bar) in the presence of solid acids as heterogeneous catalyst (SAC-13). Addition of a co-solvent, supercritical carbon dioxide (critical point at 31 °C and 73 bar), increased the rate of the supercritical alcohols transesterification, making it possible to obtain high biodiesel yields at mild temperature conditions. Experiments were carried out in a fixed bed reactor, and reactions were studied at 150-205 °C, mass flow rate 6-24 ml/min at a pressure of 250 bar. The molar ratio of methanol to oil, and catalyst amount were kept constant (9 g). The reaction temperature and space time were investigated to determine the best way for producing biodiesel. The results obtained show that the observed reaction rate is 20 time faster than conventional biodiesel production processes. The temperature of 200 °C with a reaction time of 2 min were found to be optimal for the maximum (88%) conversion to methyl ester and the free glycerol content was found below the specification limits.     

Application of Amphiphilic Catalysts,Ultrasonication, and Nanoemulsions for Biodiesel Production Process

This paper studies tuning heterogeneous transesterification catalysis and process for easy catalyst separation and enhanced reaction rate. Multibond metal alkoxides and ultrasonic pretreatment are employed to produce nanoemulsions with large interfacial area, which have the potential to be easily separated. With aluminum isopropoxide or titanium isopropoxide as the catalyst and surfactant, transparent alcohol/oil emulsions can be formed in less than four minutes and can significantly enhance the transesterification reaction rate. The micelle size was observed to be as low as 5.1 nm. Partially polymerized titanium isopropoxide also showed good catalytic activity and considerable amphiphilic properties in forming nanoemulsions. Viscosity and apparent vapor pressure reduction were also observed. The alcohol/soybean oil molar ratio was a main factor for apparent vapor pressure reduction.     

Solvent assisted decomposition of the tetrahedral intermediate of the transesterification reaction to biodiesel production. A density functional study

B3LYP/6-31 + G(d) calculations were employed to investigate the mechanism of the transesterification reaction between a model monoglyceride and the methoxide and ethoxide anions. The gas-phase results reveal that both reactions have essentially the same activation energy (5.9 kcal mol⁻¹) for decomposition of the key tetrahedral intermediate. Solvent effects were included by means of both microsolvation and the polarizable continuum solvation model CPCM. Both solvent approaches reduce the activation energy, however, only the microsolvation model is able to introduce some differentiation between methanol and ethanol, yielding a lower activation energy for decomposition of the tetrahedral intermediate in the reaction with methanol (1.1 kcal mol⁻¹) than for the corresponding reaction with ethanol (2.8 kcal mol⁻¹), in line with experimental evidences. Analysis of the individual energy components within the CPCM approach reveals that electrostatic interactions are the main contribution to stabilization of the transition state.     

Heterogenization of the biodiesel synthesis catalysis: CaO and novel calcium compounds as transesterification catalysts

Although CaO is one of the most studied basic heterogeneous catalysts for the synthesis of biodiesel, there are important issues that have been addressed by only a few research groups and that deserve further investigation. This is the case of the difficulties introduced by the poisoning of CaO upon exposure to ambient air and the role played by CaO-glycerol complexes on the catalytic performance. The purpose of this work is to provide new information on these issues in order to contribute to a better understanding of the underlying phenomena. Four commercial CaO samples have been considered to investigate their activation and stability under reaction conditions. In addition, calcium glyceroxide, and, for the first time, calcium glycerolate, have been synthesized and compared with the materials obtained from the commercial samples. The solids have been characterized with special emphasis on the assessment of their basic properties. The catalytic tests revealed big differences between the performance of the commercial solids that were substantially reduced after calcination and, specially, Ca-glyceroxide formation during reaction. Ca-glycerolate was the most resistant catalyst to ambient air although it was characterized by a low initial activity. Ca-glyceroxide could be reutilized for at least 5 reaction cycles without activity loss.