Rubber seed oil as a potential source for biodiesel production in Bangladesh

In the present paper, rubber seed oil (RSO) has been investigated as a potential source for biodiesel production in Bangladesh. Rubber seed oil has been extracted from the rubber seeds collected from the local garden. Different methods have been applied for the oil extraction, such as mechanical press with and without solvent and cold percolation. Maximum oil content of 49% has been found by mechanical press with periodic addition of solvent. The physico-chemical properties of the oil have been investigated. Effect of seed storage time on free fatty acid (FFA) content of the oil is studied an it is found that the FFA content increases from 2 wt.% (fresh seed) to 45 wt.% after 2 months of storage at room temperature. Biodiesel has been prepared using a three-step method comprises with saponification of oil, acidification of the soap and esterification of FFA. Overall yield of FFA from RSO is found to be around 86%. The final step is esterification that produces fatty acid methyl ester (FAME). The effect of methanol to oil ratio and catalyst content has been investigated for esterification reaction. ¹H NMR spectrum of the RSO and biodiesel samples are analyzed which confirms the conversion of RSO to biodiesel. The biodiesel properties have been investigated and are found to be comparable with diesel.     

Application of UNIQUAC and SVM to ultrafiltration for modeling ternary mixtures of oil, FAME and methanol

To describe a membrane separator for ternary mixtures of oil-FAME-MeOH, two models of UNIQUAC and support vector machine (SVM) are developed for the permeate composition and permeate flux, respectively. The UNIQUAC model is used to represent the liquid-liquid phase equilibrium of oil-FAME-MeOH. Its prediction results are consistent with the experimental data measured at the temperatures of 293, 313 and 333 K, respectively. For this two-phase system, experimental results show that the oil-rich phase can be rejected by the ceramic membrane while the methanol-rich phase permeates through the membrane. The permeate composition is mainly determined by the feed bulk concentration, and therefore is consistent with the concentration of the methanol-rich phase predicted by the UNIQUAC model. On the other hand, the permeate flux under various operating conditions, such as feed concentrations, temperatures, inlet flow rates and transmembrane pressures, is modeled by the SVM algorithm. Unlike the general data-based neural network model, SVM is especially valuable in the present crossflow filtration problem of small sample sizes. By combining UNIQUAC and SVM with the experimental ultrafiltration of biodiesel mixtures, the predicted membrane separator performance shows no significant lack of fit, and continuous production of biodiesel with both high purity and maximal productivity is also discussed.     

A kinetic study of the esterification of free fatty acids (FFA) in sunflower oil

The kinetics of the esterification of free fatty acids (FFA) in sunflower oil with methanol in the presence of sulphuric acid at concentrations of 5 and 10 wt% relative to free acids as catalyst and methanol/oleic acid mole ratios from 10:1 to 80:1 was studied. The experimental results were found to fit a first-order kinetic law for the forward reaction and a second-order one for the reverse reaction.The influence of temperature on the kinetic constants was determined by fitting the results to the Arrhenius equation. The energy of activation for the forward reaction decreased with increasing catalyst concentration from 50 745 to 44 559 J/mol.Based on the experimental results, a methanol/oleic acid mole ratio of 60:1, a catalyst (sulphuric acid) concentration of 5 wt% and a temperature of 60 °C provided a final acid value for the oil lower than 1 mg KOH/g oil within 120 min. This is a widely endorsed limit for efficient separation of glycerin and biodiesel during production of the latter.     

FTIR assessment of the oxidation process of castor oil FAME submitted to PetroOXY and Rancimat methods

This short communication reports an assessment of the oxidation process of castor oil fatty methyl ester samples submitted to Rancimat (EN 14112) and PetroOXY (ASTM-D7545) oxidation methods. Fourier Transformed Infrared Spectroscopy (FTIR) was used to evaluate the FAME degradation products resulting from the accelerated oxidation, following the area of the carbonyl band (~ 1740 cm⁻¹) of the samples at different oxidation times. Our results indicate that the level of oxidation of castor oil FAME, using the Rancimat method, follows a similar pattern of the oxidized samples using the PetroOXY method.     

Solid superacid catalyzed glycerol esterification of free fatty acids in waste cooking oil for biodiesel production

The free fatty acids (FFAs) of waste cooking oil (WCO) are readily esterified with crude glycerol in the presence of the solid superacid SO/ZrO₂–Al₂O₃. This reaction lowers the acidity of WCO before biodiesel production. The solid superacid SO/ZrO₂–Al₂O₃ catalyzes both FFA esterification and TAG glycerolysis during the reaction. The conversion of FFA in the WCO with an acid value of 88.4 ± 0.5 mg KOH/g to acylglycerols was 98.4% under optimal conditions (mole ratio of glycerol to FFA = 1.4:1; reaction time = 4 h; reaction temperature = 200°C; catalyst loading = 0.3 wt%) obtained through an orthogonal experiment. The final FAME product with a FAME content of 96.9 ± 0.3 wt% yield was 94.8 wt%, after transesterification of the esterified WCO with methanol, catalyzed by potassium hydroxide. The FAME composition of the products produced by transesterification were identified and quantified by GC–MS. The results suggest that this new glycerol esterification process, using a solid superacid catalyst, affords a promising method to convert oils with high FFA levels, like WCO, to biodiesel. The process has the inherent advantage of easy separation steps for removing excess alcohol and significant savings in energy, when compared to acid catalyzed reactions with methanol to lower acidity. Practical applications : In this work, WCO with a high acid value was esterified with crude glycerol catalyzed by solid super acid, whose formula was expressed as SO/ZrO₂–Al₂O₃. There are distinct advantages to this new esterification process, which include easy separation of the excess crude glycerol by sedimentation or centrifugation, the use of the low cost reactant crude glycerol direct from the byproducts of transesterification, the potential to achieve a very low content of FFAs by post‐refining to improve the yield of the final product, and time and energy saving are found as compared to the traditional methanol esterification process. This new technology provides a promising alternative method for processing feedstocks of high acid value, such as WCO, for the production of biodiesel.     

Kinetic studies on the esterification of free fatty acids in jatropha oil

Kinetic studies have been carried out on the esterification of free fatty acids (FFAs) in jatropha oil with methanol in the presence of sulphuric acid catalyst at 5 and 10 wt% concentrations relative to free fatty acids (0.4–0.8 wt% relative to oil) and methanol–FFA mole ratios ranging from 20:1 to 80:1. It has been found that a 60:1 methanol–FFA mole ratio and 5 wt% catalyst at 60°C and 500 rpm or above provided a final acid value lower than 1 mg KOH/g oil within 60 min. A kinetic model has been proposed with second‐order kinetics for both the forward and backward reactions. The effect of temperature on the reaction rate constants and equilibrium constant has been determined using Arrhenius and von't Hoff equations, respectively. The heat of reaction was found to be ?11.102 kJ/mol.     

A rapid method for evaluation of the oxidation stability of castor oil FAME: influence of antioxidant type and concentration

The oxidation stability of castor oil fatty methyl ester (FAME), doped with four different phenolic antioxidants, was evaluated using a rapid method of thermal and air-contact degradation. The methodology is based on the induction times observed when the samples are contacted with pure oxygen at elevated pressures and temperatures. The results indicate different performances of the antioxidants as well as synergisms between antioxidants and biodiesel. In general, the addition of antioxidants increased from 6-15 times the stability of castor oil FAME., with BHA (butylated hydroxyanisol) showing the best results for improving antioxidation in castor oil biodiesel.     

Transesterification of heated rapeseed oil for extending diesel fuel

Fatty acid methyl esters are well established as an alternative fuel called “biodiesel.” For economic reasons, used frying oil is an interesting alternative feedstock for biodiesel production. The chemical changes that occur during heating of rapeseed oil, especially the formation of polymers, were investigated. Heated rapeseed oil samples were transesterified with methanol and analyzed by size-exclusion chromatography. During heating, the amount of polymers in the starting oil increased up to 15 wt%, but only up to 5 wt% in the transesterified samples. So during transesterification, dimeric and trimeric triglycerides in the starting oil were mainly converted into monomeric and dimeric fatty acid methyl esters. The amount of polymeric fatty acid methyl esters had a negative influence on fuel characteristics. After 6 h of heating, the amount of Conradson carbon residue and after 16 h the viscosity exceeded that of the existing specifications for biodiesel. Therefore, the amount of polymers in waste oil is a good indicator for the suitability for biodiesel production. Presented in part at the 89th Annual Meeting, American Oil Chemists’ Society, Chicago, IL, May 1998.     

Metal oxides as heterogeneous catalysts for esterification of fatty acids obtained from soybean oil

The growing demand for renewable energy sources stimulates the development of new technologies for biofuel production. Biodiesel synthesis by esterification of fatty acids is a favorable route, because, differently from transesterification, it does not produce glycerin and uses cheaper raw materials. In this work the study of metal oxides and their performance as Lewis acid catalysts in the esterification of fatty acids obtained from soybean oil presented promising results in heterogeneous catalysis, with reaction yields as high as 89%. The influence of variables such as temperature, reaction time and the amount of catalyst in the reaction yield was also evaluated. The possibility of recycling tin oxide was also studied, showing that it was possible to reuse the catalyst up to ten times without significant losses in its catalytic activity.     

Reactive extraction and in situ esterification of Jatropha curcas L. seeds for the production of biodiesel

Jatropha curcas L. has recently been hailed as the promising feedstock for biodiesel production as it does not compete with food sources. Conventional production of biodiesel from J. curcas L. seeds involve two main processing steps; extraction of oil and subsequent esterification/transesterification to fatty acid methyl esters (FAME). In this study, the feasibility of in situ extraction, esterification and transesterification of J. curcas L. seeds to biodiesel was investigated. It was found that the size of the seed and reaction period effect the yield of FAME and amount of oil extracted significantly. Using seed with size less than 0.355 mm and n-hexane as co-solvent with the following reaction conditions; reaction temperature of 60 °C, reaction period of 24 h, methanol to seed ratio of 7.5 ml/g and 15 wt% of H₂SO₄, the oil extraction efficiency and FAME yield can reached 91.2% and 99.8%, respectively. This single step of reactive extraction process therefore can be a potential route for biodiesel production that reduces processing steps and cost.     

Ultrasonic-assisted biodiesel production process from palm oil using alkaline earth metal oxides as the heterogeneous catalysts

The ultrasonic-assisted transesterification of palm oil in the presence of alkaline earth metal oxide catalysts (CaO, SrO and BaO) was investigated. Batch process assisted by 20 kHz ultrasonic cavitation was carried out to study the effect of reaction time (10-60 min), alcohol to palm oil molar ratio (3:1-15:1), catalysts loading (0.5-3%) and varying of ultrasonic amplitudes (25-100%). The activities of the catalysts were mainly related to their basic strength. The catalytic activity was in the sequence of CaO < SrO < BaO. At optimum conditions, 60 min was required to achieve 95% yield compared to 2-4 h with conventional stirring. Also, the yields achieved in 60 min increased from 5.5% to 77.3% (CaO), 48.2% to 95.2% (SrO), and 67.3% to 95.2 (BaO). Fifty percentage amplitude of ultrasonic irradiation was deemed the most suitable value and physical changes on the catalysts after the ultrasonic-assisted reaction were successfully elucidated. BaO catalyst underwent relatively more severe activity drop in the catalyst reusability test. Catalysts dissolution was found to be mainly responsible for activity drop of the reused catalysts, especially with BaO catalyst.     

Separation of reaction mixture after ethanolysis of rapeseed oil

Various effects on the separation of a raw reaction mixture after the ethanolysis of rapeseed oil were investigated. Water addition, initial temperature of separation, centrifugation, ionic compound addition and time effects affecting the concentrations of potassium and free glycerol and the yield of the ester phase were revealed. Centrifugation has the most positive effect. Finally, a correlation between the concentrations of potassium and free glycerol was found.     

Kinetics of palm oil transesterification in a batch reactor

Methyl esters were produced by transesterification of palm oil with methanol in the presence of a catalyst (KOH). The rate of transesterification in a batch reactor increased with temperature up to 60°C. Higher temperatures did not reduce the time to reach maximal conversion. The conversion of triglycerides (TG), diglycerides (DG), and monoglycerides (MG) appeared to be second order up to 30 min of reaction time. Reaction rate constants for TG, DG, and MG hydrolysis reactions were 0.018–0.191 (wt%·min)⁻¹, and were higher at higher temperatures and higher for the MG reaction than for TG hydrolysis. Activation energies were 14.7, 14.2, and 6.4 kcal/mol for the TG, DG, and MG hydrolysis reactions, respectively. The optimal catalyst concentration was 1% KOH.     

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.     

Factors affecting the separation of the reaction mixture after transesterification of rapeseed oil

The most used method of biodiesel production is the transesterification of vegetable oils by a basic homogeneous catalyst. A heterogeneous reaction mixture is formed by this process which contains two phases: an ester phase and a glycerol phase. From this mixture, biodiesel is gained by sedimentation. The quality and quantity of both phases are affected by the conditions of the sedimentation process. It was studied how the conditions (independent variables: temperature of separation, amount of added water, time of sedimentation, etc.) affect the quantity and the quality of both phases (dependent variables). The Plackett–Burman statistic system was used for experiment planning. The relationship between independent and dependent variables was found and described by multidimensional linear regression. The created model allows the calculation of the optimum conditions of biodiesel production so that the quality of the biodiesel fulfills the EN 14214.     

Reduction of high content of free fatty acid in sludge palm oil via acid catalyst for biodiesel production

In this study, sulphuric acid (H₂SO₄) was used in the pretreatment of sludge palm oil for biodiesel production by an esterification process, followed by the basic catalyzed transesterification process. The purpose of the pretreatment process was to reduce the free fatty acids (FFA) content from high content FFA (> 23%) of sludge palm oil (SPO) to a minimum level for biodiesel production (> 2%). An acid catalyzed esterification process was carried out to evaluate the low content of FFA in the treated SPO with the effects of other parameters such as molar ratio of methanol to SPO (6:1-14:1), temperature (40-80 °C), reaction time (30-120 min) and stirrer speed (200-800 rpm). The results showed that the FFA of SPO was reduced from 23.2% to less than 2% FFA using 0.75% wt/wt of sulphuric acid with the molar ratio of methanol to oil of 8:1 for 60 min reaction time at 60 °C. The results on the transesterification with esterified SPO showed that the yield (ester) of biodiesel was 83.72% with the process conditions of molar ratio of methanol to SPO 10:1, reaction temperature 60 °C, reaction time 60 min, stirrer speed 400 rpm and KOH 1% (wt/wt). The biodiesel produced from the SPO was favorable as compared to the EN 14214 and ASTM D 6751 standard.     

Technical and Economic Analysis of Conventional and Supercritical Transesterification for Biofuel Production

The transesterification process with potassium hydroxide (KOH) catalyst and the methanol supercritical process were evaluated by Aspen HYSYS software. Castor oil and methanol were used as feed and alcohol. In order to accomplish verification, the simulation results were compared to a laboratory research. For economic analysis, these results were transferred to Aspen Economic Analyzer software. Piping and process equipment cost were calculated for the two processes. Additionally, direct and indirect costs of these processes were estimated.     

Ethanolysis of castor and cottonseed oil: A systematic study using classical catalysts

Several classical catalytic systems for the transesterification reaction have been used to produce FA ethyl esters (FAEE) from castor and cottonseed oils The effects of the amount and nature of the catalyst, and of the reaction temperature, on the yields of FAEE were determined. The most efficient transesterification of castor oil was achieved in the presence of methoxide and acid catalysts, whereas for cottonseed oil, which has a composition that is much more similar to most vegetable oils than is castor oil, the highest yields of FAEE were obtained following base-catalysed ethanolysis.