A hybrid feedstock for a very efficient preparation of biodiesel

Biodiesel has been synthesized from karanja, mahua and hybrid {karanja and mahua (50:50 v/v)} feedstocks. A high yield in the range of 95-97% was obtained with all the three feedstocks. Conversion of vegetable oil to fatty acid methyl esters was found to be 98.6%, 95.71% and 94% for karanja, mahua and hybrid feedstocks respectively. The optimized reaction parameters were found to be 6:1 (methanol to oil) molar ratio, H₂SO₄ (1.5% v/v), at 55 ± 0.5 °C for 1 h during acid esterification for the three feedstocks. During alkaline transesterification, a molar ratio of 8:1 (methanol to oil), 0.8 wt.% KOH (wt/wt) at 55 ± 0.5 °C for 1 h was found to be optimum to achieve high yield for karanja oil. For mahua oil and the hybrid feedstock, 6:1 (methanol to oil) molar ratio, 0.75 (w/w) KOH at 55 ± 0.5 °C for 1 h was optimum for alkaline transesterification to obtain a high yield. High yield and conversion from hybrid feedstock during transesterification reaction was an indication that the reaction was not selective for any particular oil. ¹H NMR has been used for the determination of conversion of the feedstock to 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.     

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.     

Producing biodiesel from high free fatty acids waste cooking oil assisted by radio frequency heating

Efficient biodiesel conversion from waste cooking oil with high free fatty acids (FFAs) was achieved via a two-stage procedure (an acid-catalyzed esterification followed by an alkali-catalyzed transesterification) assisted by radio frequency (RF) heating. In the first stage, with only 8-min RF heating the acid number of the waste cooking oil was reduced from 68.2 to 1.64 mg KOH/g by reacting with 3.0% H₂SO₄ (w/w, based on oil) and 0.8:1 methanol (weight ratio to waste oil). Then, in the second stage, the esterification product (primarily consisting of triglycerides and fatty acid methyl esters) reacted with 0.91% NaOH (w/w, based on triglycerides) and 14.2:1 methanol (molar ratio to triglycerides) under RF heating for 5 min, and an overall conversion rate of 98.8 ± 0.1% was achieved. Response surface methodology was employed to evaluate the effects of RF heating time, H₂SO₄ dose and methanol/oil weight ratio on the acid-catalyzed esterification. A significant positive interaction between RF heating time and H₂SO₄ concentration on the esterification was observed.     

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.     

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.     

Lewis acid-catalyzed transesterification and esterification of high free fatty acid oil in subcritical methanol

Lewis acid catalysts are active for both esterification and transesterification, but the reaction is very slow due to mass-transfer limitations between methanol and oil phase. Because oil, FFA and Lewis acid catalysts are all soluble in the subcritical methanol phase, the esterification and transesterification will be enhanced when they are carried out under subcritical conditions. In this work, the esterification and transesterification of high FFA oil to biodiesel via Lewis acid catalysts such as Pb(OOCCH₃)₂, Cd(OOCCH₃)₂ and Zn(OOCCH₃)₂ were carried out in the subcritical methanol phase (2 MPa, 180°C, reaction time 30 min). The results show that the esterification conversion reaches 79.8-96.4% with Palmitic acid as feedstock, and the transesterification conversion reaches 56.8-73.4% with soybean oil as feedstock. With the mixture of Soybean oil and Palmitic acid (FFA content of 20.3 wt%) as feedstock, the content of fatty acid methyl esters (FAME) in products reaches 67.3-83.4%.     

Production of biodiesel through optimized alkaline-catalyzed transesterification of rapeseed oil

Present work reports an optimized protocol for the production of biodiesel through alkaline-catalyzed transesterification of rapeseed oil. The reaction variables used were methanol/oil molar ratio (3:1-21:1), catalyst concentration (0.25-1.50%), temperature (35-65 °C), mixing intensity (180-600 rpm) and catalyst type. The evaluation of the transesterification process was followed by gas chromatographic analysis of the rapeseed oil fatty acid methyl esters (biodiesel) at different reaction times. The biodiesel with best yield and quality was produced at methanol/oil molar ratio, 6:1; potassium hydroxide catalyst concentration, 1.0%; mixing intensity, 600 rpm and reaction temperature 65 °C. The yield of the biodiesel produced under optimal condition was 95-96%. It was noted that greater or lower the concentration of KOH or methanol than the optimal values, the reaction either did not fully occur or lead to soap formation.The quality of the biodiesel produced was evaluated by the determinations of important properties such as density, specific gravity, kinematic viscosity, higher heating value, acid value, flash point, pour point, cloud point, combustion point, cold filter plugging point, cetane index, ash content, sulphur content, water content, copper strip corrosion value, distillation temperature and fatty acid composition. The produced biodiesel was found to exhibit fuel properties within the limits prescribed by the latest American Standards for Testing Material (ASTM) and European EN standards.     

Biodiesel synthesis combining pre-esterification with alkali catalyzed process from rapeseed oil deodorizer distillate

A two-step technique combining pre-esterification catalyzed by cation exchange resin with transesterification catalyzed by base alkali was developed to produce biodiesel from rapeseed oil deodorizer distillate (RDOD). The free fatty acids (FFAs) in the feedstock were converted to methyl esters in the pre-esterification step using a column reactor packed with cation exchange resin. The acid value of oil was reduced from the initial 97.60 mg-KOH g^? 1 oil to 1.12 mg-KOH g^? 1 oil under the conditions of cation exchange resin D002 catalyst packed dosage 18 wt.% (based on oil weight), oil to methanol molar ratio 1:9, reaction temperature 60 °C, and reaction time 4 h. The biodiesel yield by transesterification was 97.4% in 1.5 h using 0.8 wt.% KOH as catalyst and a molar ratio of oil to methanol 1:4 at 60 °C. The properties of RDOD biodiesel production in a packed column reactor followed by KOH catalyzed transesterification were measured up the standards of EN14214 and ASTM6751-03.     

Heterogeneous catalyzed biodiesel production from Moringa oleifera oil

In this study, biodiesel was produced from Moringa oleifera oil using sulfated tin oxide enhanced with SiO₂ (SO₄²⁻/SnO₂-SiO₂) as super acid solid catalyst. The experimental design was done using design of experiment (DoE), specifically, response surface methodology based on three-variable central composite design (CCD) with alpha (α) = 2. The reaction parameters studied were reaction temperature (60 °C to 180 °C), reaction period (1 h to 3 h) and methanol to oil ratio (1:6 to 1:24). It was observed that the yield up to 84 wt.% of Moringa oleifera methyl esters can be obtained with reaction conditions of 150 °C temperature, 150 min reaction time and 1:19.5 methanol to oil ratio, while catalyst concentration and agitation speed are kept at 3 wt.% and 350-360 rpm respectively. Therefore this study presents the possibility of converting a relatively new oil feedstock, Moringa oleifera oil to biodiesel and thus reducing the world's dependency on existing edible oil as biodiesel feedstock.     

In situ production of fatty acid methyl ester from low quality rice bran: An economical route for biodiesel production

Low quality rice bran was used to produce fatty acid methyl ester (FAME) via in situ extraction, esterification and transesterification process. The effects of the acid and alkaline catalysts on the ester yield, esterification and transesterification process were studied. When 75 ml of absolute methanol, 150 ml of petroleum ether, 0.75 g of concentrated sulfuric acid and 0.71 g of sodium hydroxyl were used, 16.69% (w_FAME/w_{rice bran}) of FAME was obtained. The esterification rate and the transesterification rate reached 98.83% and 80.47%. Based on the proposed route, the production process of FAME (biodiesel) could be simplified and the production cost could be reduced.     

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.     

From organic waste to biodiesel: Black soldier fly, Hermetiaillucens, makes it feasible

Biodiesel is a renewable and environmentally friendly liquid fuel. However, the feedstock, predominantly crop oil, is a limited and expensive food resource which prevents large scale application of biodiesel. Development of non-food feedstocks are therefore, needed to fully utilize biodiesel’s potential. In this study, the larvae of a high fat containing insect, black soldier fly (Hermetiaillucens) (BSFL), was evaluated for biodiesel production. Specifically, the BSFL was grown on organic wastes for 10 days and used for crude fat extraction by petroleum ether. The extracted crude fat was then converted into biodiesel by acid-catalyzed (1% H₂SO₄) esterification and alkaline-catalyzed (0.8% NaOH) transesterification, resulting in 35.5 g, 57.8 g and 91.4 g of biodiesel being produced from 1000 BSFL growing on 1 kg of cattle manure, pig manure and chicken manure, respectively. The major ester components of the resulting biodiesel were lauric acid methyl ester (35.5%), oleinic acid methyl ester (23.6%) and palmitic acid methyl ester (14.8%). Fuel properties of the BSFL fat-based biodiesel, such as density (885 kg/m³), viscosity (5.8 mm²/s), ester content (97.2%), flash point (123 °C), and cetane number (53) were comparable to those of rapeseed-oil-based biodiesel. These results demonstrated that the organic waste-grown BSFL could be a feasible non-food feedstock for biodiesel production.     

Production of biodiesel from waste fryer grease using mixed methanol/ethanol system

Transesterification of waste fryer grease (WFG) containing 5–6 wt.% free fatty acid (FFA) was carried out with methanol, ethanol, and mixtures of methanol/ethanol maintaining the oil to alcohol molar ratio of 1:6, and initially with KOH as a catalyst. Mixtures of methanol and ethanol were used for transesterification in order to use the better solvent property of ethanol and rapid equilibrium using methanol. Formation of soap by reaction of FFA present in WFG with KOH instigated difficulty in the separation of glycerol from biodiesel ester. To untangle this problem, two-stage (acid and alkali catalyzed) method was used for biodiesel synthesis. More than 90% ester was obtained when two-stage method was used compared to ∼ 50% ester in single stage alkaline catalyst. In the case of mixed alcohol, a relatively smaller amount of ethyl esters was formed along with methyl esters. Acid value, viscosity, and cetane number of all the esters prepared from WFG were within the range of the ASTM standard. Esters obtained from WFG showed good performance as a lubricity additive.     

Production of ethyl ester from crude palm oil by two-step reaction with a microwave system

The production of ethyl esters of fatty acids from a feed material of crude palm oil (CPO) with a high free fatty acid (FFA) content under microwave assistance has been investigated. Parametric studies have been carried out to investigate the optimum conditions for the esterification process (amount of ethanol, amount of catalyst, reaction time, and microwave power). As a result, a molar ratio of FFA to ethanol of 1:24 with 4% wt./wt. of H₂SO₄/FFA, a microwave power of 70 W, and a reaction time of 60 min have been identified as optimum reaction parameters for the esterification process aided by microwave heating. At the end of the esterification process, the amount of FFA had been reduced from 7.5 wt.% to less than 2 wt.%. Similar results were obtained following conventional heating at 70 °C, but only after a reaction time of 240 min. Transesterification of the esterified palm oil has been accomplished with a molar ratio of CPO to ethanol of 1:4, 1.5 wt.% KOH as a catalyst, a microwave power of 70 W, and a reaction time of 5 min. This two-step esterification and transesterification process provided a yield of 80 wt.% with an ester content of 97.4 wt.%. The final ethyl ester product met with the specifications stipulated by ASTM D6751-02.     

Transesterification of vegetable oil to biodiesel fuel using alkaline catalyst

Biodiesel is gaining more and more importance as an attractive fuel due to the depleting fossil fuel resources. 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 to give the corresponding monoalkyl esters. This article reports experimental data on the production of fatty acid methyl esters from vegetable oils, soybean and cottonseed oils using sodium hydroxide as alkaline catalyst. The variables affecting the yield and characteristics of the biodiesel produced from these vegetable oils were studied. The variables investigated were reaction time (1-3 h), catalyst concentration (0.5-1.5 w/wt%), and oil-to-methanol molar ratio (1:3-1:9). From the obtained results, the best yield percentage was obtained using a methanol/oil molar ratio of 6:1, sodium hydroxide as catalyst (1%) and 60 ± 1 °C temperature for 1 h. The yield of the fatty acid methyl ester (FAME) was determined according to HPLC. The composition of the FAME was determined according to gas chromatography. The biodiesel samples were physicochemically characterized. From the results it was clear that the produced biodiesel fuel was within the recommended standards of biodiesel fuel.     

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.     

Hydrodynamic cavitation as an efficient approach for intensification of synthesis of methyl esters from sustainable feedstock

Investigations related to process intensification of synthesis of methyl esters from sustainable feedstock is gaining importance because of considerable energy requirements and higher reaction time in the conventional approach. The present work illustrates the use of hydrodynamic cavitation for intensification of methyl ester synthesis from the high acid value non-edible oil. Two-step synthesis of acid esterification followed by alkaline transesterification has been employed for obtaining the methyl esters. In first step, acid esterification is used to reduce the acid value of oil from 18.7 to less than 1.5 mg of oil/g of oil beyond which alkaline transesterification can be used without any problems of soap formation. The molar ratio and catalyst concentration have been optimized for the esterification and transesterification stages. The optimized molar ratios were 1:3 and 1:6 for esterification and transesterification respectively. Under optimized conditions, 92% conversion has been obtained in the transesterification stage. It has been established that due to the use of hydrodynamic cavitation, the energy requirement for the synthesis is significantly reduced as compared to the conventional approach. The novel route discussed in the present work provides a viable option and can be explored easily for the industrial scale of operations.     

Synthesis of economically viable biodiesel from waste frying oils (WFO)

In present communication, waste frying oil (WFO) has been used as a feedstock for biodiesel synthesis. WFO, procured from a local Indian restaurant possessed an acid value of 0.84 mg KOH/g, which is low enough for single step transesterification reaction. Biodiesel (fatty acid methyl esters) was washed after transesterification reaction and the yield got lowered substantially (from 96% to 86.36%) after water washing owing to loss of esters. 30:100 vol% (methanol to oil), 0.6 wt% NaOCH₃, 60°C temperature and 600 rpm agitation in 1 h reaction time was found to be optimum for transesterification reaction. ¹H NMR spectrum showed a high conversion (95.19%) of fatty acids in WFO to biodiesel in 2 h reaction time. Almost complete conversion (99.68%) was attained in 2 h reaction time. © 2011 Canadian Society for Chemical Engineering     

Optimization of two step karanja biodiesel synthesis under microwave irradiation

The free fatty acid of crude karanja oil (Pongamia pinnata) was reduced and biodiesel was synthesized from pretreated oil under microwave irradiation. The process variables such as irradiation time, methanol-oil ratio and sulfuric acid concentration for pretreatment step; irradiation time, methanol-oil ratio and KOH concentration were optimized through the Box-Behnken experimental design. The free fatty acid of crude karanja oil was reduced to 1.11 ± 0.07% with an optimal combination of 190 s irradiation time (180 W), 33.83 (w/w)% methanol-oil ratio and 3.73 (w/w)% sulfuric acid concentration. An optimal combination of 150 s irradiation time, 33.4 (w/w)% methanol-oil ratio and 1.33 (w/w)% KOH concentration yielded 89.9 ± 0.3% biodiesel. The model was validated by conducting experiments at optimal design conditions. The present work confirmed that the microwave energy has a significant effect on esterification and transesterification reaction.