Biodiesel Synthesis from Palm Fatty Acid Distillate Using Tungstophosphoric Acid Supported on Cesium-Containing Niobia

Tungstophosphoric acid supported on cesium-containing niobia (TPA/Cs _x /Nb₂O₅, x = 1.0–2.5) catalysts were prepared by a two-step impregnation method, and their physico-chemical properties were investigated. The initial studies on the esterification of oleic acid with methanol revealed that TPA/Cs ratio affected the acidity as well as the activity of the catalysts. Among the catalysts tested, TPA/Cs_1.0/Nb₂O₅ exhibited the best performance. In addition, the efficiency of TPA/Cs_1.0/Nb₂O₅ for biodiesel synthesis from palm fatty acid distillate (PFAD), a by-product from palm oil industry, was demonstrated, and the reaction parameters were also evaluated. Over 90% yield of FAME was achieved, and the properties of the biodiesel obtained from PFAD met the standard requirements for biodiesel fuel. However, deactivation of the catalysts was observed, possibly due to structural transformation or organic residues blocking the active sites.     

Esterification of Fatty Acids in Greases to Fatty Acid Methyl Esters with Highly Active Diphenylamine Salts

Diphenylamine sulfate (DPAS) and diphenylamine hydrochloride (DPACl) salts were found to be highly active catalysts for esterification and substantial transesterification of inexpensive greases to fatty acid methyl esters (FAME). In the presence of catalytic amounts of DPAS or DPACl and excess methanol, the free fatty acids as well as the acylglycerols in waste greases were converted to FAME at 125 °C within 1 h. Although the DPAS and DPACl catalysts were found to have similar catalytic activities to their parent liquid acids (i.e., sulfuric and hydrochloric acids) the diphenylammonium salts are much easier to work with than concentrated liquid acids.     

Lipase-Catalyzed Production of Biodiesel by Hydrolysis of Waste Cooking Oil Followed by Esterification of Free Fatty Acids

Biodiesel is conventionally produced by alkaline‐catalyzed transesterification, which requires high‐purity oils. However, low‐quality oils can be used as feedstocks for the production of biodiesel by enzyme‐catalyzed reactions. The use of enzymes has several advantages, such as the absence of saponification side reactions, production of high‐purity glycerol co‐product, and low‐cost downstream processing. In this work, biodiesel was produced from lipase‐catalyzed hydrolysis of waste cooking oil (WCO) followed by esterification of the hydrolyzed WCO (HWCO). The hydrolysis of acylglycerols was carried out at 30 °C in salt‐free water (WCO/water ratio of 1:4, v/v) and the esterification of HWCO was carried out at 40 °C with ethanol in a solvent‐free medium (HWCO/ethanol molar ratio of 1:7). The hydrolysis and esterification steps were carried out using immobilized Thermomyces lanuginosus lipase (TLL/WCO ratio of 1:5.6, w/w) and immobilized Candida antarctica lipase B (10 wt%, CALB/HWCO) as biocatalysts, respectively. The hydrolysis of acylglycerols was almost complete after 12 h (ca. 94 %), and in the esterification step, the conversion was around 90 % after 6 h. The purified biodiesel had 91.8 wt% of fatty acid ethyl esters, 0.53 wt% of acylglycerols, 0.003 wt% of free glycerol, viscosity of 4.59 cP, and acid value of 10.88 mg KOH/g. Reuse hydrolysis and esterification assays showed that the immobilized enzymes could be recycled five times in 10‐h batches, under the conditions described above. TLL was greatly inactivated under the assay conditions, whereas CALB remained fully active. The results showed that WCO is a promising feedstock for use in the production of biodiesel.     

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.     

假丝酵母99-125脂肪酶促酯化合成生物柴油的研究

1 INTRODUCTION Biodiesel, that is long-chain fatty acid short-chain alcohol esters (methyl, ethyl, propyl and butyl ester), is produced by esterification of fatty acids or inter- esterification of oils and fats. These fatty acid alcohol esters are not only used as important industrial addi- tives and surfactants, but also used for biofuel. The biodiesel is a biodegradable, environmental friendly, renewable substitute of diesel fuel[1]. The traditional production of biodiesel is by chem- i…     

棕榈酸化油制备生物柴油的工艺优化研究

试验研究了以棕榈酸化油与甲醇为原料,在催化剂(浓硫酸)的作用下,通过酯化反应制备生物柴油。采用单因素试验和正交优化试验,考察反应温度、搅拌速率、醇油摩尔比和催化剂用量(与原料油质量比)对酯化反应收率的影响。确定最佳反应条件为反应温度为55℃,搅拌速率为200 r/min,醇油摩尔比为7:1,催化剂用量为2.0%,且在该条件下酯化效率为93.9%。     

An Empirical Equation for Estimation of Kinematic Viscosity of Fatty Acid Methyl Esters and Biodiesel

Kinematic viscosity (µ) is an important physical property of fatty acid methyl esters (FAME) and biodiesel. In this work, the Martin's rule of free energy additivity is extended to cover the kinematic viscosity of saturated and unsaturated FAME commonly found in nature. The proposed model can also be extended to estimate kinematic viscosity of biodiesel. The kinematic viscosity of a FAME or a biodiesel can be easily estimated from its carbon number (z), number of double bonds (n_d) at different temperatures (T) without a prior knowledge of the viscosity of individual FAME. Both z_ave and n_d(ave) can be derived from its fatty acid composition. Thus, kinematic viscosity of biodiesel at temperatures between 20 and 100 °C and at atmospheric pressure can be estimated. The average absolute deviation (AAD) estimated at 20–100 °C for saturated, unsaturated FAME, biodiesels and biodiesel blends are 4.15, 3.25, 6.95 and 2.79 %, respectively. The biodiesels collected in this study (191 data points) have the z_ave and n_d(ave) between 14.10 and 17.96 and 0.21–1.54, respectively. The standard deviation was 0.249. The proposed model would be good for estimation of viscosity of biodiesel containing normal fatty acids, generally found in biodiesel feed stocks.     

A Predictive Correlation for Dynamic Viscosity of Fatty Acid Methyl Esters and Biodiesel

The viscosity of biodiesel, which is a mixture of fatty acid methyl esters (FAME), is an important physical property in the injection and efficient combustion. In this study, a simple correlation, with only one adjustable parameter, is proposed for predicting the viscosity of FAME and their mixtures (biodiesel) as a function of temperature. First, the adjustable parameter of the correlation is calculated for various FAME. The average absolute relative deviation (AARD) is obtained to be 0.97% for 226 data points. Second, the adjustable parameter of FAME is connected to the number of carbon atoms and the number of double bonds to build a predictive correlation for the calculation of viscosity. The AARD for 226 data points is obtained to be 2.28%. Third, the proposed model is employed to predict the viscosity of biodiesel without introducing any new adjustable parameter. To predict the viscosity of biodiesel, the average of the adjustable parameter is applied to the correlation. The AARD of 2.96% is obtained for 185 data points comprised of 23 different biodiesels. To better understand the ability of the correlation in the estimation of the viscosity of biodiesel and FAME, a comparison is made between the present correlation and a number of correlations available in the literature.     

Intrinsic Kinetics of Esterification of Fatty Acids Catalyzed by Supported Ionic Liquid Catalysts

Esterification of palm fatty acid distillate with methanol was investigated for intrinsic kinetics and regarding the effect of catalyst loading, temperature, and methanol to feed molar ratio using ionic liquid acidic catalysts covalently attached to a polystyrene support. The kinetic parameters of the Langmuir‐Hinshelwood‐Hougan‐Watson model of the reaction are determined for comparison with those using p‐toluenesulfonic acid and methanesulfonic acid as homogeneous catalysts considering the phase split of the reaction mixture into two liquid phases during the reaction. The intrinsic parameters could predict the dynamic behavior of the system under various operating conditions.     

Esterification of Palm Fatty Acid Distillate Using a Sulfonated Mesoporous CuO‐ZnO Mixed Metal Oxide Catalyst

A nanocrystalline mesoporous CuO‐ZnO hollow sphere was successfully fabricated by the hydrothermal method. The nanocomposite was formed in the presence of polyethylene glycol as a dispersant and D‐glucose as a template. The mesoporous CuO‐ZnO catalyst was further functionalized with benzenesulfonic acid to catalyze the esterification of palm fatty acid distillate (PFAD). The physicochemical, textural, structural, and thermal properties of the mesoporous CuO‐ZnO mixed‐oxide catalysts were evaluated. The modified mesoporous catalyst possessed unique textural properties. With a Cu/Zn atomic ratio of 1.0 the best catalytic activity through PFAD esterification was achieved. The optimum reaction conditions in terms of methanol/PFAD molar ratio, catalyst concentration, reaction temperature, and reaction time were determined.     

Biodiesel Production from Rubber Seed Oil by Transesterification Using a Co‐solvent of Fatty Acid Methyl Esters

Rubber seed oil (RSO) is a high‐potential feedstock for the production of biodiesel fuel (BDF) in Asia. Transesterification using fatty acid methyl esters (FAMEs) as co‐solvents was developed for BDF production from RSO with high content of free fatty acids (FFAs). The homogeneous system (FAMEs/triglyceride/methanol) was attained when the FAME content was more than 30 wt %. After esterification of RSO, the crude RSO obtained was transesterified with FAMEs as a co‐solvent. The quality of BDF with high FAME content satisfied the criteria of the EN 14214/JIS K2390 standards. These results suggest that FAMEs converted from FFAs can be applied as a co‐solvent and, thus, reused for BDF production.     

A Comprehensive Evaluation of the Density of Neat Fatty Acids and Esters

Density is one of the most important physical properties of a chemical compound, affecting numerous applications. An application in the case of fatty acid esters (biodiesel) is that density is specified in some biodiesel standards. In the present work, the density of fatty acid methyl, ethyl, propyl, and butyl esters as well as triacylglycerols in the C₈–C₂₄ range was determined in the range of 15–40 °C with a densitometer utilizing the oscillating U-tube technique. Literature data on density are compiled and compared, showing that data for these compounds are incomplete with discrepancies existing in some cases. Besides known effects such as density decreasing with increasing chain length and increasing saturation, it is shown that trans fatty compounds exhibit lower density than cis fatty compounds. Density data for several saturated odd-numbered, C₁₈, as well as C₂₀ and C₂₂ polyunsaturated fatty esters are reported for the first time. The density contribution of compounds with high melting points is predicted. An equation is given for the calculation of the density of mixtures.     

Reactor Comparison for the Esterification of Fatty Acids from Waste Cooking Oil

Esterification of the fatty acids contained in waste cooking oil with glycerol, a reaction involving immiscible and viscous reactants, was achieved in two pilot‐scale continuous pulsed reactors: the oscillatory baffled reactor and the helix reactor. In both reactors, with or without baffles, the reaction reaches its thermodynamic equilibrium at lower temperatures, shorter residence times and with higher selectivities than those reported in the literature. This equilibrium is then shifted by an increase in the excess of glycerol, or by removing water from the reactive media by an intermediary decantation or by the use of dodecylbenzene sulfonic acid, a surfactant catalyst. Further investigations would be required to increase the conversions without decreasing the selectivities, by increasing the initial amount of free fatty acids.     

Comparison of Fatty Acid Methyl and Ethyl Esters as Biodiesel Base Stock: a Review on Processing and Production Requirements

Fatty acid methyl esters (FAME) were the first fatty acid esters to be introduced for use as biodiesel. However, there is a growing interest in the use of fatty acid ethyl esters (FAEE) in biodiesel. Both FAME and FAEE have their own unique advantages and disadvantages. These differences are ultimately attributable to the structural differences imparted by the alcohols used in their production. Sources of reactants as well as their safety issues, are a focus of this review. Also reviewed are the comparative characteristics and properties of both biodiesel types in terms of physicochemical features and performance. Processing requirements, reaction times and molar ratios of alcohol to oil, together with problems and drawbacks, are discussed. Recent developments on improving the yield of biodiesel, include mixing methanol and ethanol in the same reaction with ethanol acting as a co-solvent, and enzymatic methanolysis and ethanolysis are also highlighted.     

Response Surface Optimization of Biodiesel Production via Catalytic Transesterification of Fatty Acids

Oil from Jatropha seeds was extracted by supercritical CO₂. A catalytic transesterification reactor was employed for biodiesel production from extracted oil in which fatty acids like palmitic, stearic, oleic, and linoleic acid were converted to fatty acid methyl esters (FAMEs) with sodium methoxide as the catalyst. Gas chromatography‐flame ionization detector (GC‐FID) analysis identified and quantitatively determined the amount of FAMEs. Response surface methodology (RSM) was applied to find the optimal operating conditions in order to maximize the biodiesel yield. Under the RSM‐predicted optimum conditions, the maximum yields of four individual FAMEs and their combination as biodiesel were determined. The RSM model demonstrated that the linear and square terms of four variables and the interaction of flow rate and dynamic time significantly influence the biodiesel yield.     

Producing Fatty Acid Methyl Esters from Free Fatty Acids with Ionic Liquids as Catalyst

Three Brønsted acidic imidazole dicationic ionic liquids (ILs) with different length of alkyl chains, [C_n(Mim)₂][HSO₄]₂ (n = 3, 6, 12), were prepared and used as catalyst for the esterification reaction of free fatty acids and methanol. Taking oleic acid as model acid, the catalytic performances of the synthesized ILs for the esterification were evaluated. The main physicochemical properties of the ILs, thermal stability, acidity, solubility in common solvents, and causticity on Austenitic stainless steel 316, were examined. [C₃(Mim)₂][HSO₄]₂ demonstrated the highest catalytic activity and enabled to assess the preliminary optimum esterification condition of oleic acid and methanol. Under optimized reaction conditions, the yield of oleic acid methyl ester was up to 95 %. The ILs have great potential as catalysts for producing fatty acid methyl esters from long‐chain free fatty acids.     

Free Lipase-Catalyzed Esterification of Oleic Acid for Fatty Acid Ethyl Ester Preparation with Response Surface Optimization

Free lipase-mediated alcoholysis for biodiesel production has drawn increasing attention in recent years due to its advantages of lower cost and faster reaction rate compared to immobilized lipase. Ethanol, derived from renewable biomass, has a great potential for biodiesel production. A previous study showed that free lipase NS81006 could effectively catalyze the ethanolysis of triglycerides for biodiesel preparation. Since most crude plant oils always contain an amount of free fatty acids, oleic acid was used as the model substrate for this study on lipase-mediated esterification for biodiesel production. The central composite design of the response surface methodology was adopted for process optimization. A biodiesel yield of over 90 % was achieved under optimal reaction conditions and the repeated use of the free lipase was easily realized through phase separation either by natural gravity force or centrifugation.     

Esterification of palm fatty acid distillate (PFAD) in supercritical methanol: Effect of hydrolysis on reaction reactivity

This study demonstrated the potential use of local palm fatty acid distillate (PFAD) as alternative feedstock for fatty acid methyl esters (FAMEs) production and the possibility to replace the conventional acid-catalyzed esterification process (with H₂SO₄), which was industrially proven to suffer by several corrosion and environmental problems, with non-catalytic process in supercritical methanol. At 300 °C with the PFAD to methanol molar ratio of 1:6 and the reaction time of 30 min, the esterification of PFAD in supercritical methanol gave FAMEs production yield of 95%. Compared with transesterification of purified palm oil (PPO) in supercritical methanol, the production of FAMEs reached the maximum yield of only 80% at 300 °C with higher requirement for methanol (1:45 PPO to methanol molar ratio). Compared with the conventional acid-catalyzed esterification of PFAD, only 75% FAMEs yield was obtained in 5 h. The presence of water in the feed (between 0 and 30% v/v) was found to lower the yield of FAMEs production from PFAD significantly. This negative effect was proven to be due to the further hydrolysis of FAMEs, which nevertheless can be minimized when high content of methanol was used.     

A Density Functional Theory Study on the Acid-Catalyzed Transesterification Mechanism for Biodiesel Production from Waste Cooking Oils

The acid-catalyzed transesterification reaction has been one of the most effective methods to produce biodiesel, especially from waste cooking oils (WCO) with high contents of water and free fatty acids (FFA). However, in the acid-catalyzed processes, the H⁺ action mechanism and the controlling step of the reaction rate have been ambiguous. To clearly understand the reaction process, the DMol3 module based on the density functional theory (DFT) was employed to investigate the acid (H⁺-)-catalyzed transesterification mechanism of methanol and oleic acid monoacylglycerol (OAM). The one step transesterification without a catalyst and the feasible paths of SN2 (substitution nucleophilic bimolecular) and SN1 (substitution nucleophilic unimolecular) reaction mechanisms with H⁺-based catalysts were built as Path 1, Path 2, and Path 3, respectively. The calculated structures, thermodynamic, and kinetic data revealed that the H⁺-based catalysts could effectively reduce the activation energy for the transesterification reaction, and the Path 2 based on the SN2 reaction mechanism was the optimal reaction path. A tetrahedral intermediate (IM2-2) could be generated with the highest active energy of 15.383 kcal mol⁻¹, implying that there was the most stable structure of IM2-2 as the key species in the transesterification process. Hence, the increasing decomposition rate of IM2-2 accelerated the forward reaction in H⁺-based biodiesel processes. The calculated active energy of 15.383 kcal mol⁻¹ was in good agreement with the kinetic data for the monoacylglycerol transesterification of 15.067 kcal mol⁻¹. Our calculations should provide basic and reliable theoretical data for further understanding the mechanism of transesterification of WCO to biodiesel products in the future work.     

Heterogeneous Acid-Catalyzed Biodiesel Production from Crude Tall Oil: A Low-Grade and Less Expensive Feedstock

The present study indicates that solid acid catalysis of crude tall oil (CTO) over a WO₃/ZrO₂ catalyst is effective in converting the CTO fatty acids components into biodiesel in high yield. Preparation of the catalyst by an impregnation method was selected and WO₃ activity was best at a loading mass fraction of 5% to ZrO₂ support and activation at 500°C for five hours under air at atmospheric pressure. Optimal reaction conditions were reaction temperature at 250°C; methanol to CTO molar ratio at 10; reaction time four hours, catalyst mass fraction of 3%; and stirring intensity at 625 rpm. The conversion at optimal reaction conditions was 70%. The catalyst was highly active at temperatures higher than 200°C. The biodiesel produced met some, but not all, the diesel quality parameters stipulated by standard specifications such as ASTM D6751 and EN14214.