Optimization of process conditions using response surface methodology for the microwave-assisted transesterification of Jatropha oil with KOH impregnated CaO as catalyst

A transesterification reaction of Jatropha curcas oil with methanol in the presence of KOH impregnated CaO catalyst was performed in a simple continuous process. The process variables such as methanol/oil molar ratio (X₁), amount of catalyst (X₂) and total reaction time (X₃) were optimized through response surface methodology, using the Box–Behnken model. Within the range of the selected operating conditions, the optimal ratio of methanol to oil, amount of catalyst and total reaction time were found to be 8.42, 3.17% and 67.9 min, respectively. The results showed that the amount of catalyst and total reaction time have significant effects on the transesterification reaction. For the product to be accepted as a biodiesel fuel, its purity must be above 96.5% of alkyl esters. Based on the optimum condition, the predicted biodiesel conversion was 97.6% while the actual experimental value was 97.1%. The above mentioned results demonstrated that the response surface methodology (RSM) based on Box–Behnken model can well predict the optimum condition for the biodiesel production.     

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.     

Conversion of waste cooking oil to biodiesel using ferric sulfate and supercritical methanol processes

In this comparative study, conversion of waste cooking oil to methyl esters was carried out using the ferric sulfate and the supercritical methanol processes. A two-step transesterification process was used to remove the high free fatty acid contents in the waste cooking oil (WCO). This process resulted in a feedstock to biodiesel conversion yield of about 85-96% using a ferric sulfate catalyst. In the supercritical methanol transesterification method, the yield of biodiesel was about 50-65% in only 15 min of reaction time. The test results revealed that supercritical process method is probably a promising alternative method to the traditional two-step transesterification process using a ferric sulfate catalyst for waste cooking oil conversion. The important variables affecting the methyl ester yield during the transesterification reaction are the molar ratio of alcohol to oil, the catalyst amount and the reaction temperature. The analysis of oil properties, fuel properties and process parameter optimization for the waste cooking oil conversion are also presented.     

An ideal feedstock, kusum (Schleichera triguga) for preparation of biodiesel: Optimization of parameters

Kusum (Schleichera triguga), a non-edible oil bearing plant has been used as an ideal feedstock for biodiesel development in the present study. Various physical and chemical parameters of the raw oil and the fatty acid methyl esters derived have been tested to confirm its suitability as a biodiesel fuel. The fatty acid component of the oil was tested by gas chromatography. The acid value of the oil was determined by titration and was found to 21.30 mg KOH/g which required two step transesterification. Acid value was brought down by esterification using sulfuric acid (H₂SO₄) as a catalyst. Thereafter, alkaline transesterification was carried out using potassium hydroxide (KOH) as catalyst for conversion of kusum oil to its methyl esters. Various parameters such as molar ratio, amount of catalyst and reaction time were optimized and a high yield (95%) of biodiesel was achieved. The high conversion of the feedstock into esters was confirmed by analysis of the product on gas chromatograph-mass spectrometer (GC-MS). Viscosity and acid value of the product biodiesel were determined and found to be within the limits of ASTM D 6751 specifications. Elemental analysis of biodiesel showed presence of carbon, hydrogen, oxygen and absence of nitrogen and sulfur after purification. Molar ratio of methanol to oil was optimized and found to be 10:1 for acid esterification, and 8:1 for alkaline transesterification. The amounts of H₂SO₄ and KOH, 1% (v/v) and 0.7% (w/w), respectively, were found to be optimum for the reactions. The time duration of 1 h for acid esterification followed by another 1 h for alkaline transesterification at 50 ± 0.5 °C was optimum for synthesis of biodiesel.     

Process optimization for biodiesel production from Jatropha, Karanja and Polanga oils

Petroleum sourced fuels is now widely known as non-renewable due to fossil fuel depletion and environmental degradation. Renewable, carbon neutral, transport fuels are necessary for environmental and economic sustainability. Biodiesel derived from oil crops is a potential renewable and carbon neutral alternative to petroleum fuels. Chemically, biodiesel is monoalkyl esters of long chain fatty acids derived from renewable feed stock like vegetable oils and animal fats. It is produced by transesterification in which, oil or fat is reacted with a monohydric alcohol in presence of a catalyst. The process of transesterification is affected by the mode of reaction condition, molar ratio of alcohol to oil, type of alcohol, type and amount of catalysts, reaction time and temperature and purity of reactants. In the present paper various methods of preparation of biodiesel from non-edible filtered Jatropha (Jatropha curcas), Karanja (Pongamia pinnata) and Polanga (Calophyllum inophyllum) oil have been described. Mono esters (biodiesel) produced and blended with diesel were evaluated. The technical tools and processes for monitoring the transesterification reactions like TLC, GC and HPLC have also been used.     

The Optimization of the Production of Methyl Esters from Corn Oil Using Barium Hydroxide as a Heterogeneous Catalyst

In recent years, vegetable oils, as renewable raw materials, became a promising feedstock for chemicals and biodiesel production. The main products derived from oils are esters of fatty acids, especially methyl esters, obtained by their transesterification with methanol, in presence of acid or alkaline catalysts. The use of such catalysts implies the need for washing operations, which leads to environmental pollution. In the present paper, the response surface methodology based on a central composite design, has been developed to optimize the process of transesterification of corn oil. Ba(OH)₂ in presence of diethyl ether was used as catalyst. A quadratic polynomial equation was obtained. It correlates the reaction parameters [methanol/oil molar ratio (x _r), reaction time (x _t) and catalyst concentration (x _c)] with methyl esters yield. Analysis of variance analysis showed that only methanol/oil molar ratio and catalyst concentration have had the most significant influences on the conversion. The maximum methyl esters yield was obtained using the following optimum parameters: methanol/corn oil ratio of 11.32, reaction time of 118 min and catalyst concentration of 3.6 wt%.     

Rape oil transesterification over heterogeneous catalysts

This work studies the application of KNO₃/CaO catalyst in the transesterification reaction of triglycerides with methanol. The objective of the work was characterizing the methyl esters for its use as biodiesel in compression ignition motors. The variables affecting the methyl ester yield during the transesterification reaction, such as, amount of KNO₃ impregnated in CaO, the total catalyst content, reaction temperature, agitation rate, and the methanol/oil molar ratio, were investigated to optimize the reaction conditions.The evolution of the process was followed by gas chromatography, determining the concentration of the methyl esters at different reaction times. The biodiesel was characterized by its density, viscosity, cetane index, saponification value, iodine value, acidity index, CFPP (cold filter plugging point), flash point and combustion point, according to ISO norms. The results showed that calcium oxide, impregnated with KNO₃, have a strong basicity and high catalytic activity as a heterogeneous solid base catalyst.The biodiesel with the best properties was obtained using an amount of KNO₃ of 10% impregnated in CaO, a methanol/oil molar ratio of 6:1, a reaction temperature of 65 °C, a reaction time of 3.0 h, and a catalyst total content of 1.0%. In these conditions, the oil conversion was 98% and the final product obtained had very similar characteristics to a no. 2 diesel, and therefore, these methyl esters might be used as an alternative to fossil fuels.     

Alkali catalyzed transesterification of safflower seed oil assisted by microwave irradiation

The safflower (Carthamus tinctorius L.) oil was extracted from the seeds of the safflower that grows in Diyarbakir, SE Anatolia of Turkey. Biodiesel has been prepared from safflower seed by transesterification of the crude oil under microwave irradiation, with methanol to oil molar ratio of 10:1, in the presence of 1.0% NaOH as catalyst. The conversion of C. tinctorius oil to methyl ester was over 98.4% at 6 min. The important fuel properties of safflower oil and its methyl ester (biodiesel) such as density, kinematic viscosity, flash point, iodine number, neutralization number, pour point, cloud point, cetane number are found out and compared to those of no. 2 petroleum diesel, ASTM and EN biodiesel standards. Compared with conventional heating methods, the process using microwaves irradiation proved to be a faster method for alcoholysis of triglycerides with methanol, leading to high yields of biodiesel.     

Transesterification of the crude Jatropha curcas L. oil catalyzed by micro‐NaOH in supercritical and subcritical methanol

Transesterification of the crude Jatropha curcas L. oil catalyzed by micro‐NaOH in supercritical/subcritical methanol was studied. The effects of various reaction variables such as the catalyst content, reaction temperature, reaction pressure and the molar ratio of methanol to oil on the conversion of crude Jatropha curcas L. oil to biodiesel were investigated. The results showed that even micro‐NaOH could noticeably improve this reaction. When NaOH was added from 0.2 to 0.5 to 0.8 wt‐‰ of triacylglycerols, the transesterification rate increased sharply; when the catalyst content was further increased, the reaction rate was just poorly improved. It was observed that increasing the reaction temperature had a favorable influence on the methyl ester yield. For the molar ratio ranging from 18 to 36, the higher the molar ratio of methanol to oil was charged, the faster the transesterification rate seemed. At the fixed stirring rate of 400 rpm, when the catalyst content, reaction temperature, reaction pressure and the molar ratio of methanol to oil were developed at 0.8 wt‐‰ NaOH, 523 K, 7.0 MPa and 24 : 1, respectively, the methyl ester yield could reach 90.5% within 28 min. Further, the kinetics of this reaction was involved and the results showed that it was a pseudo‐first‐order reaction whose apparent activation energy was 84.1 kJ/mol, and the pre‐exponential factor was 2.21×10⁵.     

In situ transesterification of coconut oil using mixtures of methanol and tetrahydrofuran

The conventional biodiesel production method requires oil extraction followed by transesterification with methanol. The solubility of vegetable oils in methanol is low which decreases the overall rate of reaction. To eliminate the oil extraction step and improve the overall reaction rate, simultaneous extraction, esterification and transesterification were conducted by directly mixing methanol and tetrahydrofuran (THF) co-solvent and sulfuric acid catalyst with ground, desiccated coconut meat (copra) in a batch process and continuing the reaction until the system reached steady state. After separation of the mixture, yield was obtained by measuring the content of triglycerides, diglycerides and monoglycerides in the biodiesel phase. The yield increases with THF:methanol ratio, methanol:oil molar ratio and temperature. Within the range of conditions tested, the highest yield achieved was 96.7% at 60 °C, THF:methanol volume ratio of 0.4 and methanol:oil molar ratio of 60:1. The methanol:oil molar ratio is necessarily high in order to completely wet the copra mass, but is still lower than in previous studies by other researchers on in situ transesterification. Product assays show that the resulting biodiesel product is similar to conventionally produced coconut biodiesel. The results indicate that the in situ transesterification of copra using methanol/THF mixtures merits further study.     

Biodiesel production using tetramethyl- and benzyltrimethyl ammonium hydroxides as strong base catalysts

In recent years, the acceptance of fatty acid methyl esters (biodiesel) as an alternative fuel has rapidly grown in EU. The most common method for biodiesel production is based on triglyceride transesterification to methyl esters with dissolved sodium hydroxide in methanol as catalyst. In this study, cottonseed oil and used frying oil were subjected to the transesterification reaction with tetramethyl ammonium hydroxide and benzyltrimethyl ammonium hydroxide as strong base catalysts. This work investigates the optimum conditions for biodiesel production using amine-based liquid catalysts. Biodiesel ester content was strongly related with the type of feedstock and the reaction variables, such as those of the catalyst concentration, methanol to oil molar ratio, and reaction time. The overall results suggested that the transesterification of cottonseed oil achieved high conversion rates with both catalysts, while the use of waste oil resulted in lower yields of methyl esters due to the possible formation of amides.     

Optimization of biodiesel production from edible and non-edible vegetable oils

The non-edible vegetable oils such as Jatropha curcas and Pongamia glabra (karanja) and edible oils such as corn and canola were found to be good viable sources for producing biodiesel. Biodiesel production from different edible and non-edible vegetable oils was compared in order to optimize the biodiesel production process. The analysis of different oil properties, fuel properties and process parameter optimization of non-edible and edible vegetable oils were investigated in detail. A two-step and single-step transesterification process was used to produce biodiesel from high free fatty acid (FFA) non-edible oils and edible vegetable oils, respectively. This process gives yields of about 90-95% for J. curcas, 80-85% for P. glabra, 80-95% for canola, and 85-96% for corn using potassium hydroxide (KOH) as a catalyst. The fuel properties of biodiesel produced were compared with ASTM standards for biodiesel.     

Biodiesel production from vegetable oil using heterogenous acid and alkali catalyst

Zanthoxylum bungeanum seed oil (ZSO) with high free fatty acids (FFA) can be used for biodiesel production by ferric sulfate-catalyzed esterification followed by transesterification using calcium oxide (CaO) as an alkaline catalyst. Acid value of ZSO with high FFA can be reduced to less than 2 mg KOH/g by one-step esterification with methanol-to-FFA molar ratio 40.91:1, ferric sulfate 9.75% (based on the weight of FFA), reaction temperature 95 °C and reaction time 2 h, which satisfies transesterification using an alkaline catalyst. The response surface methodology (RSM) was used to optimize the conditions for ZSO biodiesel production using CaO as a catalyst. A quadratic polynomial equation was obtained for biodiesel conversion by multiple regression analysis and verification experiments confirmed the validity of the predicted model. The optimum combination for transesterification was methanol-to-oil molar ratio 11.69:1, catalyst amount 2.52%, and reaction time 2.45 h. At this optimum condition, the conversion to biodiesel reached above 96%. This study provided a practical method to biodiesel production from raw feedstocks with high FFA with high reaction rate, less corrosion, less toxicity, and less environmental problems.     

Process optimization design for jatropha-based biodiesel production using response surface methodology

Biodiesel of non food vegetal oil origin is gaining attention as a replacement for current fossil fuels as its non-food chain interfering manufacturing processes shall prevent food source competition which is expected to happen with current biodiesel production processes. As a result, non edible Jatropha curcas plant oil is claimed to be a highly potential feedstock for non-food origin biodiesel. CaO–MgO mixed oxide catalyst was employed in transesterification of non-edible J. curcas plant oil in biodiesel production. Response surface methodology (RSM) in conjunction with the central composite design (CCD) was employed to statistically evaluate and optimize the biodiesel production process. It was found that the production of biodiesel achieved an optimum level of 93.55% biodiesel yield at the following reaction conditions: 1) Methanol/oil molar ratio: 38.67, 2) Reaction time: 3.44 h, 3) Catalyst amount: 3.70 wt.%, and 4) Reaction temperature: 115.87 °C. In economic point of view, transesterification of J. curcas plant oil using CaO–MgO mixed oxide catalyst requires less energy which contributed to high production cost in biodiesel production. The incredibly high biodiesel yield of 93.55% was proved to be the synergetic effect of basicity between the active components of CaO–MgO shown in the physicochemical analysis.     

Application of response surface methodology for optimization of biodiesel production by transesterification of soybean oil with ethanol

In this paper, the transesterification of soybean oil with ethanol is studied. The transesterification process can be affected by differing parameters. The biodiesel production process was optimized by the application of factorial design 2⁴ and response surface methodology. The combined effects of temperature, catalyst concentration, reaction time and molar ratio of alcohol in relation to oil were investigated and optimized using response surface methodology. Optimum conditions for the production of ethyl esters were the following: mild temperature at 56.7 °C, reaction time in 80 min, molar ratio at 9:1 and catalyst concentration of 1.3 M.     

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.     

Transesterification of rapeseed oil in subcritical methanol conditions

In this study, transesterification of rapeseed oil using subcritical methanol conditions was studied. The objective of the work was characterizing the methyl esters for its use as biodiesel in compression ignition motors. The variables affecting the methyl ester yield during the transesterification reaction, such as, the catalyst type and content, reaction temperature and pressure, the presence of hexane as co-solvent, the methanol oil molar ratio and the methanol hexane molar ratio were investigated to optimize the reaction conditions. The evolution of the process was followed by gas chromatography, determining the concentration of the methyl esters at different reaction times. The biodiesel was characterized by its density, viscosity, saponification value, iodine value, acidity index and water content, according to ISO norms. High methyl ester yield and fast reaction rate could be obtained even if the reaction pressure was relatively low, which is quite favorable to the production of biodiesel in industry.     

Optimization of biodiesel production process in a continuous microchannel using response surface methodology

We assessed the biodiesel production process in a continuous microchannel through preparation of a heterogeneous catalyst (CaO/MgO) from demineralized water plant sediment. This mixed oxide catalyst was used for transesterification of rapeseed oil as feedstock by methanol to produce biodiesel fuel at various conditions. A microchannel, utilized as a novel reactor, was applied to convert rapeseed oil into biodiesel in multiple steps. The effects of the process variables, such as catalyst concentration, methanol to oil volume ratio, n-hexane to oil volume ratio, and reaction temperature on the purity of biodiesel, were carefully investigated. Box-Behnken experimental design was employed to obtain the maximum purity of biodiesel response surface methodology. The optimum condition for the production of biodiesel was the following: catalyst concentration of 7.875 wt%, methanol to oil volume ratio of 1.75: 3, n-hexane to oil volume ratio of 0.575: 1, and reaction temperature of 70 °C.     

Conversion of biomass to fuel: Transesterification of vegetable oil to biodiesel using KF loaded nano-γ-Al2O3 as catalyst

KF-impregnated nanoparticles of γ-Al₂O₃ were calcinated and used as heterogeneous catalysts for the transesterification of vegetable oil with methanol for the synthesis of biodiesel (fatty acid methyl esters, FAME). The ratio of KF to nano-γ-Al₂O₃, calcination temperature, molar ratio of methanol/oil, transesterification reaction temperature and time, and the concentration of the catalyst were used as the parameters of the study. A methyl ester yield of 97.7 ± 2.14% was obtained under the catalyst preparation and transesterification conditions of KF loading of 15 wt%, calcination temperature of 773 K, 8 h of reaction time at 338 K, and using 3 wt% catalysts and molar ratio of methanol/oil of 15:1. This relatively high conversion of vegetable oil to biodiesel is considered to be associated with the achieved relatively high basicity of the catalyst surface (1.68 mmol/g) and the high surface to volume ratio of the nanoparticles of γ-Al₂O₃.     

Production of biodiesel from palm oil using liquid core lipase encapsulated in κ-carrageenan

This work deals with the enzymatic transesterification of palm oil with methanol in a solvent-free system. Among the five lipases tested in the initial screening, lipase PS from Burkholderia cepacia resulted in the highest triglyceride conversion. Lipase PS was further investigated in a novel immobilized form by encapsulating within a biopolymer, κ-carrageenan. Using the immobilized lipase the production parameters of biodiesel from palm oil were optimized. The optimal conditions for processing 10 g of palm oil was: 30 °C, 1:7 oil/methanol molar ratio, 1 g water, 5.25 g immobilized lipase, 72 h reaction time and 23.7g relative centrifugal force. At the optimal conditions, triglyceride conversion of up to 100% could be obtained. The immobilized lipase was stable and retained 82% relative transesterification activity after five cycles. Liquid core lipase encapsulated in κ-carrageenan could be a potential immobilized catalyst for eco-friendly production of biodiesel.