Homogeneous borotungstic acid and heterogeneous micellar borotungstic acid catalysts for biodiesel production by esterification of free fatty acid

A highly negatively charged borotungstic acid H₅BW₁₂O₄₀ had been tested as homogeneous catalyst in esterification. Compared with common used H₃PW₁₂O₄₀, it displayed a higher conversion (98.7%) and excellent efficiency (96.2%) due to its high amount of protons in methanol. In order to overcome the drawbacks of homogeneous heteropolyacid H₅BW₁₂O₄₀, a Brønsted-surfactant-combined (C₁₆TA)H₄BW₁₂O₄₀ (C₁₆TA = cetyltrimethyl ammonium) had been fabricated with strong acidity and nano-size micellar structure resulting in enhanced activity and stability during the reaction, which exhibited consistent activity during recycling in esterification reaction.     

Biodiesel production by esterification of palm fatty acid distillate

Production of fatty acid methyl ester (FAME) from palm fatty acid distillate (PFAD) having high free fatty acids (FFA) was investigated in this work. Batch esterifications of PFAD were carried out to study the influence of: including reaction temperatures of 70–100 °C, molar ratios of methanol to PFAD of 0.4:1–12:1, quantity of catalysts of 0–5.502% (wt of sulfuric acid/wt of PFAD) and reaction times of 15–240 min. The optimum condition for the continuous esterification process (CSTR) was molar ratio of methanol to PFAD at 8:1 with 1.834 wt% of H₂SO₄ at 70 °C under its own pressure with a retention time of 60 min. The amount of FFA was reduced from 93 wt% to less than 2 wt% at the end of the esterification process. The FAME was purified by neutralization with 3 M sodium hydroxide in water solution at a reaction temperature of 80 °C for 15 min followed by transesterification process with 0.396 M sodium hydroxide in methanol solution at a reaction temperature of 65 °C for 15 min. The final FAME product met with the Thai biodiesel quality standard, and ASTM D6751-02.     

Thermodynamic analysis of fatty acid esterification for fatty acid alkyl esters production

The development of renewable energy source alternatives has become a planet need because of the unavoidable fossil fuel scarcity and for that reason biodiesel production has attracted growing interest over the last decade. The reaction yield for obtaining fatty acid alkyl esters varies significantly according to the operating conditions such as temperature and the feed reactants ratio and thus investigation of the thermodynamics involved in such reactional systems may afford important knowledge on the effects of process variables on biodiesel production. The present work reports a thermodynamic analysis of fatty acid esterification reaction at low pressure. For this purpose, Gibbs free energy minimization was employed with UNIFAC and modified Wilson thermodynamic models through a nonlinear programming model implementation. The methodology employed is shown to reproduce the most relevant investigations involving experimental studies and thermodynamic analysis.     

Studies on the performance of tubular flow reactor for esterification of free fatty acid from used cooking oil using highly porous cation exchange resin as catalyst

Semi-batch esterification of free fatty acid (FFA) from used cooking oil with methanol was carried out using RCP160M cation exchange resin in a tubular flow reactor (TFR). The results revealed that the conversion of FFA increased with the increase of catalyst bed height, methanol to oil mass ratio and decreases with increase of feedstock flow rates. However, the FFA conversion was decreased upon further increases of methanol to oil mass ratio from 6:1 to 12:1. This might possibly happen due to several factors such as mass transfer limitation between reactants and catalyst and inhomogeneity of the reactants during the reaction.     

Acid esterification of a high free fatty acid crude palm oil and crude rubber seed oil blend: Optimization and parametric analysis

Free fatty acids content plays an important role in selecting the appropriate route for biodiesel production. Oils with high content of free fatty acids can be treated by acid esterification where an alcohol reacts with the given oil in the presence of acid catalyst. In the current study, an equivolume blend of crude rubber seed oil and crude palm oil is fed to the reaction with methanol as the alcohol of choice and sulfuric acid. Selected reaction parameters were optimized, using Taguchi method for design of experiments, to yield the lowest free fatty acid content in the final product. The investigated parameters include alcohol to oil ratio, temperature and amount of catalyst. The effect and significance of each parameter were then studied based on the fractional factorial design and verified by additional experiments. The optimum conditions for acid esterification which could reduce the free fatty acid content in the feedstock to lower than 0.6% (95% reduction) were 65 °C, 15:1 methanol to oil ratio (by mole) and 0.5 wt% H₂SO₄ after 3 h of reaction time. Temperature had been found to have the most effect on the reduction of free fatty acids followed by reactants ratio while increasing catalyst amount had nominal effect.     

Solid base catalysts for production of fatty acid methyl esters

A solid base catalyst Na₂SiO₃ was prepared by microwave heating. The catalyst was used to catalyze the transesterification reactions for the production of fatty acid methyl esters from cottonseed oil. The optimum conditions of the catalyst preparation and transesterification reactions were investigated by orthogonal experiments. The catalyst with the highest catalytic activity was obtained using microwave power of 640 W, microwave irradiation time of 6 min, catalyst particle size of 60 mesh. The catalyst was characterized with X-ray diffraction (XRD), scanning electron micrographs (SEM), and the results showed the catalyst Na₂SiO₃ has good microstructure. Under the transesterification conditions of methanol/oil molar ratio of 6:1, catalyst dosage of 5%, reaction temperature of 65 °C, reaction time of 100 min and stirring speed of 400 rpm, the yield of methyl esters was 97.6%. The lifetime of the solid base catalysts by different process methods (microwave heating and conventional electric heating) was no significant differences, but microwave heating may be more economical than conventional electric heating.     

Lipase-catalysed transesterification: Viewpoint of the mechanism and influence of free fatty acids

A series of lipase-catalysed transesterification experiments were carried out to study the effect of the presence of free fatty acids on synthesis reaction rate and the stability of the biocatalyst, and also to elucidate the underlying process, which remains a subject of debate. Based on the results, the reaction rate and biocatalyst stability increased with increasing content in free fatty acids of the reaction mixture. Also, tests carried out with a mixture of triolein and linoleic acid revealed that the transesterification is a combination of direct alcoholysis of triacylglycerols and a two-step reaction involving hydrolysis of acylglycerols and further esterification of previously released free fatty acids. The time course of triacylglycerols and diacylglycerols revealed that the enzyme is similarly selective for both types of substrate.     

Production of biodiesel using high free fatty acid feedstocks

The enormous challenges faced in the search for suitable and profitable feedstocks to produce biodiesel cannot be over-emphasis. This paper has provided an overview of different catalysts used in processing different kinds of feedstocks for the production of biodiesel. Although the process of biodiesel production from refined feedstocks is less cumbersome and could provide biodiesel yield of more than 98%, but its product cost is high. Thus, the recent biodiesel production from low-quality feedstocks, though presents challenges but has equally provided biodiesel yield comparable to that obtained from refined feedstocks. Furthermore the physicochemical properties of biodiesel derived from low-quality feedstocks are discussed. Additionally economic evaluation of biodiesel from low-quality feedstocks is examined. The result showed that if less expensive feedstocks are used to produce biodiesel, a 25% reduction in cost production is possible. Thus making biodiesel price reasonably closed to the price of petro-diesel.     

Continuous esterification for biodiesel production from palm fatty acid distillate using economical process

An overflow system for continuous esterification of palm fatty acid distillate (PFAD) using an economical process was developed using a continuous stirred tank reactor (CSTR). Continuous production compared to batch production at the same condition had higher product purity. The optimum condition for the esterification process was a 8.8:1:0.05 molar ratio of methanol to PFAD to sulfuric acid catalyst, 60 min of residence time at 75 °C under its own pressure. The free fatty acid (FFA) content in the PFAD was reduced from 93 to less than 1.5%wt by optimum esterification. The esterified product had to be neutralized with 10.24%wt of 3 M sodium hydroxide in water solution at a reaction temperature of 80 °C for 20 min to reduce the residual FFA and glycerides. The components and properties of fatty acid methyl ester (FAME) could meet the standard requirements for biodiesel fuel. Eventually the production costs were calculated to disclose its commercialization.     

SO_4~(2-)/ZrO_2催化油酸和甘油酯化反应研究

以八水合氧氯化锆(Zr OCl2·8H2O)作为锆源,硫酸铵[(NH4)2SO4]作为硫化剂,通过沉淀浸渍法制得硫酸化氧化锆(SO42-/Zr O2)固体酸催化剂,通过XRD,Py-IR和SEM表征研究了催化剂的晶型,酸性和表面形貌,并测试了催化剂的硫含量及对油酸和甘油酯化反应的催化效果。研究结果表明:焙烧温度对催化剂的晶型有明显影响,并且随焙烧温度的升高,催化剂中SO42-含量流失加剧,500℃焙烧的催化剂催化效果最好;硫酸化氧化锆催化剂既有Br觟nsted酸位,也有Lewis酸位;水存在情况下硫酸化氧化锆催化剂易失活;在酯化反应中,升高反应温度、提高催化剂用量油酸转化率随之升高,回收的催化剂在重复使用前进行焙烧,其活性可得到恢复。     

Synthesis of biodiesel from waste vegetable oil with large amounts of free fatty acids using a carbon-based solid acid catalyst

A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized vegetable oil asphalt. This catalyst was employed to simultaneously catalyze esterification and transesterification to synthesis biodiesel when a waste vegetable oil with large amounts of free fatty acids (FFAs) was used as feedstock. The physical and chemical properties of this catalyst were characterized by a variety of techniques. The maximum conversion of triglyceride and FFA reached 80.5 wt.% and 94.8 wt.% after 4.5 h at 220 °C, when using a 16.8 M ratio of methanol to oil and 0.2 wt.% of catalyst to oil. The high catalytic activity and stability of this catalyst was related to its high acid site density (–OH, Brönsted acid sites), hydrophobicity that prevented the hydration of –OH species, hydrophilic functional groups (–SO₃H) that gave improved accessibility of methanol to the triglyceride and FFAs, and large pores that provided more acid sites for the reactants.     

The influence of free fatty acid intermediate on biodiesel production from soybean oil by whole cell biocatalyst

The whole cell of lipase-producing Rhizopus oryzae was employed as biocatalyst for transesterification of soybean oil containing oleic acid. The free fatty acid (FFA) intermediate, playing an important role in the kinetics of transesterification of soybean oil, was thoroughly investigated and characterized. The conversion was more than 97% at the initial FFA content of 5.5%. A high content of FFA could protect the lipase from denaturation. The 34.6 percent of FFA with the optimal 26-mg mL⁻¹ methanol resulted in a specific reaction rate of 420 mg h⁻¹g-dry cell⁻¹. In addition, the methanol/FFA ratio at 0.83-1.7 provides a good indication of the fatty acid methyl esters conversions for different initial FFA contents. In the transesterification process, more FFA intermediate present would become beneficial to conversion of retrograde feedstock to biodiesel. The immediately generated and original FFA content become the major rate-determining factor in the FFA-mixed transesterification process.     

Oxidation stability of biodiesel derived from high free fatty acid feedstock

At present, with fluctuating feedstock prices, the biodiesel manufacturing industries are facing some downfall. High free fatty acid (FFA) non-edible oil, which is a byproduct of vegetable oil refineries, is available at low price and in considerable quantities at vegetable oil refinery sites. This high FFA oil can be utilized as a potential low cost feedstock for biodiesel production. In the present work, high FFA (51.6%) oil was synthesized into biodiesel by a two-step process. Except oxidation stability, other fuel properties of the produced biodiesel were found to be comparable with that of biodiesel specifications. Oxidation stability was found to be only 2.1 h at 110°C as determined by the Rancimat apparatus.

In order to study and further improve the oxidation stability, the biodiesel (B100) was dosed with a suitable antioxidant (pyrogallol) and stored for 6 months. The acid value, peroxide value, and kinematic viscosity which are closely associated with oxidation behavior were studied. It was found that biodiesel dosed with an antioxidant showed the least increase in the acid value, peroxide value, and kinematic viscosity. Also, induction period was improved and found to be within the American Society for Testing and Materials limit . Thus, the high FFA oil-based biodiesel with a suitable antioxidant can be used as a potential feedstock to resolve the issue of the high cost of biodiesel production.     

Study on preparation and thermal property of binary fatty acid and the binary fatty acids/diatomite composite phase change materials

This study prepared a series of binary phase change materials by mixing decanoic acid, dodecanoic acid, hexadecanoic acid and octadecanoic acid each other. The phase-transition temperature of binary fatty acid and its corresponding mixing proportion are calculated with phase diagram thermodynamic method. The results are verified by the experimental result of the heat absorption curve and the Differential Scanning Calorimetry (DSC) analysis curve. The results show that the calculation method of phase diagram thermodynamic calculation can be taken as a basis for mixing proportion of binary fatty acid phase change materials. In addition, the decanoic–dodecanoic acid/diatomite composite phase change material (PCM) are prepared and its microstructure, thermal property and thermal reliability are characterized. The result shows that the decanoic–dodecanoic acid is uniformly adsorbed into diatomite and the form-stable PCM are formed. The phase-transition temperature and the latent heat of the decanoic–dodecanoic acid/diatomite composite PCMs is 16.74 °C and 66.8114 J/g, respectively.     

Biodiesel production from mixture of mahua and simarouba oils with high free fatty acids

A suitable process comprising acid pretreatment followed by main base transesterification reaction was developed to produce biodiesel from mixture of Mahua (M) and Simarouba (S) oils with high free fatty acids (FFA). The acid pretreatment reduced the high FFAs of the mixture of oils to around 1% which were then transesterified with methanol and KOH as catalyst at a reaction temperature of 60 °C. A genetic algorithm coupled with artificial neural network (ANN-GA) model to obtain the best pretreatment process parameters for bringing down the FFA level of individual vegetable oils to around 1% was modified to include the wide range of oils and validated for mixtures of M and S oils. The quality of biodiesel produced was analyzed by gas chromatography (GC), which indicated above 90% ester conversion. The fuel properties of biodiesel were found to be comparable to diesel and were conforming to the latest biodiesel standards.     

Recent developments on heterogeneous catalysts for biodiesel production by oil esterification and transesterification reactions: A review

Heterogeneous catalysis is widely applied in industry due to important advantages it offers to chemical processes such as improved selectivity and easy catalyst separation from reaction mixture, reducing process stages and wastes. This is the reason why nowadays heterogeneous catalysts are being developed to produce biodiesel. Several catalytic materials have been showed in bibliography: acid solids capable to carry out free fatty acids esterification reaction, base solids which are able to carry out triglycerides transesterification reaction and bifunctional solids (acid–base character) which show ability to simultaneously catalyze esterification and transesterification reaction. This review discusses the latest advances in research and development related with heterogeneous catalysts used to produce biodiesel.     

Effects of water vapour and solid catalysts on the gasification of cellulose at elevated pressures

The gasification of cellulose was examined from 350 to 650°C in helium and helium/water vapour mixtures up to total pressures of 2500 kPa. Particular attention was paid to the effects on the [$\text{(CO}{}_2\text{+ H}{}_2\text{)}\text{CO}$] molar ratio in the product gases of the selected additives—iron(III)oxide, zinc(II)chromite and potassium carbonate. The results are interpreted in terms of catalytic influences on key steps in the reaction sequence. Thus, the most effective additive in realising the highest gaseous fuel potential was potassium carbonate which may act as a catalyst for the carbon/steam reaction. Although the calorific value of the gases produced was not altered much by pressure, it did slightly affect the distribution of the product gases, probably by influencing the secondary reactions of tars. Scanning electron micrographs of the various solid samples are presented.     

Effects of volatile fatty acid concentrations on methane yield and methanogenic bacteria

Volatile fatty acids (VFAs) are important mid-products in the production of methane, and their concentrations affect the efficiency of fermentation. However, their effects on methane yield and methanogenic bacteria growth have been less extensively studied. To address these effects, acetic acid, propionic acid, butyric acid and ethanol were used as substrates and an L₉(3⁴) orthogonal table was adopted to design anaerobic digestion tests. When the highest concentrations of ethanol, acetic acid and butyric acid were 2400, 2400 and 1800 mg L^?1, respectively, there was no significant inhibition of the activity of methanogenic bacteria. However, when the propionic acid concentration was increased to 900 mg L^?1, significant inhibition appeared, the bacteria concentration decreased from 6 × 10⁷ to 0.6–1 × 10⁷ ml^?1 and their activity would not reconvert. These effects resulted in the accumulation of ethanol and VFAs, and the total methane yield consequently became very low (<321 ml). The original propionic acid concentration had a significant inhibitory effect on methanogenic bacteria growth (P < 0.01). An optimization analysis showed that ethanol, acetic acid, propionic acid and butyric acid at concentrations of 1600, 1600, 300 and 1800 mg L^?1, respectively, led to the maximum accumulative methane yield of 1620 ml and the maximum methanogenic bacteria concentration of 7.3 × 10⁸ ml^?1.     

Preparation and application of Ce/ZrO2−TiO2/SO42− as solid catalyst for the esterification of fatty acids

To develop heterogeneous and reusable catalyst for the esterification of fatty acids, in presence of triglycerides, sulfate species has been incorporated over Ce/ZrO₂–TiO₂ support. The catalyst activity was found to be a function of its Bronsted acidic sites which in turn depends on the cerium concentration in catalyst. The esterification of oleic acid with methanol or ethanol in presence of prepared catalyst has followed the first order kinetics and Koros–Nowak test has demonstrated that reaction rates are independent from diffusion limitations. An increase in acid or alcohol alkyl chain length (steric factor) was found to show negative effect on the esterification activity of catalyst. Although, the catalyst was able to catalyze the esterification even in presence of up to 12 wt% moisture (with respect to fatty acids), however, a decrease in turn over frequency (TOF) was observed. The catalyst has shown excellent stability as negligible sulfate leaching was observed and recovered catalyst was reused in five successive runs without significant loss in activity.Even in presence of triglyceride (vegetable oil) the catalyst was able to convert >98% free fatty acids into respective esters. The esterified oils were fruitfully employed, without any pre-neutralization and water washing, in homogeneous alkali catalyzed transesterification to achieve >98% fatty acid methyl ester (FAME) yield.