Process optimization for biodiesel production from mahua (Madhuca indica) oil using response surface methodology

A central composite rotatable design was used to study the effect of methanol quantity, acid concentration and reaction time on the reduction of free fatty acids content of mahua oil during its pretreatment for making biodiesel. All the three variables significantly affected the acid value of the product, methanol being the most effective followed by reaction time and acid catalyst concentration. Using response surface methodology, a quadratic polynomial equation was obtained for acid value by multiple regression analysis. Verification experiments confirmed the validity of the predicted model. The optimum combinations for reducing the acid level of mahua oil to less than 1% after pretreatment was 0.32 v/v methanol-to-oil ratio, 1.24% v/v H2SO4 catalyst and 1.26 h reaction time at 60 degrees C. After the pretreatment of mahua oil, transesterification reaction was carried out with 0.25 v/v methanol-to-oil ratio (6:1 molar ratio) and 0.7% w/v KOH as an alkaline catalyst to produce biodiesel. The fuel properties of mahua biodiesel so obtained complied the requirements of both the American and European standards for biodiesel.     

Acid-catalyzed esterification of Zanthoxylum bungeanum seed oil with high free fatty acids for biodiesel production

A technique to produce biodiesel from crude Zanthoxylum bungeanum seed oil (ZSO) with high free fatty acids (FFA) was developed. The acid value of ZSO was reduced to 1.16mg KOH/g from 45.51mg KOH/g by only one-step acid-catalyzed esterification with methanol-to-oil molar ratio 24:1, H(2)SO(4) 2%, temperature 60 degrees C and reaction time 80min, which was selected as optimum for the acid-catalyzed esterification. During the acid-catalyzed esterification, FFA was converted into fatty acid methyl esters, which was confirmed by (1)H NMR spectrum. Compared with the other two-step pretreatment procedure, this one-step pretreatment can reduce the production cost of ZSO biodiesel. Alkaline-catalyzed transesterification converted the pretreated ZSO into ZSO biodiesel. The yield of ZSO biodiesel was above 98% determined by (1)H NMR spectrum. This study supports the use of crude ZSO as a viable and valuable raw feedstock for biodiesel production.     

Optimization of a Novel Two-step Process Comprising Re-esterification and Transesterification in a Single Reactor for Biodiesel Production Using Waste Cooking Oil

Waste cooking oil (WCO) has attracted attention as a non-edible feedstock for biodiesel. Although an alkali catalyst has several advantages over an acid catalyst in biodiesel production, biodiesel conversion from WCO is only 5.2% when using an alkali catalyst (NaOH), owing to its high free fatty acid (FFA) content of 4.2%. In this study, a novel two-step process in a single reactor, comprised of re-esterification of the FFAs with crude glycerol, using a Tin (II) chloride (SnCl₂) catalyst, and subsequent transesterification with methanol, using an alkali catalyst, was adopted, and each step was optimized. This study revealed that the FFA content after re-esterification should be approximately 1.5%, not only to save glycerol and the catalyst involved in the re-esterification, but also to achieve high biodiesel conversion during the transesterification. An alkaline catalyst was successfully used to produce biodiesel in the second step, and a 92.8% conversion to biodiesel was achieved under the optimized conditions (0.6% catalyst relative to WCO, 0.2mL-methanol/WCO, 70ºC, 3 h). Overall, this novel two-step process achieved highly enhanced biodiesel conversion (4.0% to 92.8%) with significantly reduced reaction time (12 h to 4 h) and methanol requirements (15 mL/g-WCO to 0.2 mL/g-WCO).     

A two-step acid-catalyzed process for the production of biodiesel from rice bran oil

A study was undertaken to examine the effect of temperature, moisture and storage time on the accumulation of free fatty acid in the rice bran. Rice bran stored at room temperature showed that most triacylglyceride was hydrolyzed and free fatty acid (FFA) content was raised up to 76% in six months. A two-step acid-catalyzed methanolysis process was employed for the efficient conversion of rice bran oil into fatty acid methyl ester (FAME). The first step was carried out at 60 degrees C. Depending on the initial FFA content of oil, 55-90% FAME content in the reaction product was obtained. More than 98% FFA and less than 35% of TG were reacted in 2 h. The organic phase of the first step reaction product was used as the substrate for a second acid-catalyzed methanolysis at 100 degrees C. By this two-step methanolysis reaction, more than 98% FAME in the product can be obtained in less than 8 h. Distillation of reaction product gave 99.8% FAME (biodiesel) with recovery of more than 96%. The residue contains enriched nutraceuticals such as gamma-oryzanol (16-18%), mixture of phytosterol, tocol and steryl ester (19-21%).     

Transesterification of soybean oil using combusted oyster shell waste as a catalyst

Transesterification of soybean oil catalyzed by combusted oyster shell, which is waste material from shellfish farms, was examined. Powdered oyster shell combusted at a temperature above 700 degrees C, at which point the calcium carbonate of oyster shell transformed to calcium oxide, acted as a catalyst in the transesterification of soybean oil. On the basis of factorial design, the reaction conditions of catalyst concentration and reaction time were optimized in terms of the fatty acid methyl ester concentration expressed as biodiesel purity. Under the optimized reaction conditions of a catalyst concentration and reaction time of 25wt.%. and 5h, respectively, the biodiesel yield, expressed relative to the amount of soybean oil poured into the reaction vial, was more than 70% with high biodiesel purity. These results indicate oyster shell waste combusted at high temperature can be reused in biodiesel production as a catalyst.     

Enzymatic production of biodiesel from cotton seed oil using t-butanol as a solvent

The enzymatic production of biodiesel by methanolysis of cottonseed oil was studied using immobilized Candida antarctica lipase as catalyst in t-butanol solvent. Methyl ester production and triacylglycerol disappearance were followed by HPLC chromatography. It was found, using a batch system, that enzyme inhibition caused by undissolved methanol was eliminated by adding t-butanol to the reaction medium, which also gave a noticeable increase of reaction rate and ester yield. The effect of t-butanol, methanol concentration and temperature on this system was determined. A methanolysis yield of 97% was observed after 24h at 50 degrees C with a reaction mixture containing 32.5% t-butanol, 13.5% methanol, 54% oil and 0.017 g enzyme (g oil)(-1). With the same mixture, a 95% ester yield was obtained using a one step fixed bed continuous reactor with a flow rate of 9.6 mlh(-1) (g enzyme)(-1). Experiments with the continuous reactor over 500 h did not show any appreciable decrease in ester yields.     

Application of a Burkholderia cepacia lipase-immobilized silica monolith to batch and continuous biodiesel production with a stoichiometric mixture of methanol and crude Jatropha oil

Background

The enzymatic production of biodiesel through alcoholysis of triglycerides has become more attractive because it shows potential in overcoming the drawbacks of chemical processes. In this study, we investigate the production of biodiesel from crude, non-edible Jatropha oil and methanol to characterize Burkholderia cepacia lipase immobilized in an n-butyl-substituted hydrophobic silica monolith. We also evaluate the performance of a lipase-immobilized silica monolith bioreactor in the continuous production of biodiesel.

Results

The Jatropha oil used contained 18% free fatty acids, which is problematic in a base-catalyzed process. In the lipase-catalyzed reaction, the presence of free fatty acids made the reaction mixture homogeneous and allowed bioconversion to proceed to 90% biodiesel yield after a 12 hour reaction time. The optimal molar ratio of methanol to oil was 3.3 to 3.5 parts methanol to one part oil, with water content of 0.6% (w/w). Further experiments revealed that B. cepacia lipase immobilized in hydrophobic silicates was sufficiently tolerant to methanol, and glycerol adsorbed on the support disturbed the reaction to some extent in the present reaction system. The continuous production of biodiesel was performed at steady state using a lipase-immobilized silica monolith bioreactor loaded with 1.67 g of lipase. The yield of 95% was reached at a flow rate of 0.6 mL/h, although the performance of the continuous bioreactor was somewhat below that predicted from the batch reactor. The bioreactor was operated successfully for almost 50 days with 80% retention of the initial yield.

Conclusions

The presence of free fatty acids originally contained in Jatropha oil improved the reaction efficiency of the biodiesel production. A combination of B. cepacia lipase and its immobilization support, n-butyl-substituted silica monolith, was effective in the production of biodiesel. This procedure is easily applicable to the design of a continuous flow-through bioreactor system.     

Production of structured triacylglycerols (STAG) rich in docosahexaenoic acid (DHA) in position 2 by acidolysis of tuna oil catalyzed by lipases

This work deals with the production of structured triacylglycerols (STAG) with caprylic acid (CA) located in positions 1 and 3 of the molecule of glycerol and docosahexaenoic acid (DHA) in position 2, by acidolysis of tuna oil and CA, catalyzed by several lipases. To this end several lipases and immobilization supports were tested with the aim of avoiding the acyl-migration observed in previous works. The determination of the best catalyst (i.e. the lipase and the immobilization support as a whole) was carried out by experiments of acidolysis of cod liver oil and CA in a bath reactor. The best results were obtained with the lipases from Rhizopus oryzae (Lipase D) and Rhizopus delemar (Lipase Rd), immobilized on Accurel MP1000 (a microporous polypropylene) with a lipase/support ratio 1:1.5 (w/w). The activity of these immobilized lipases was stable for a minimum of 5 days in the operational conditions (up to 40 °C).Lipase Rd was selected for the next step in which it was immobilized on Acurrel MP1000 to obtain STAG enriched in DHA by acidolysis of tuna oil (20% DHA) with CA. The experiments were carried out by recirculating the reaction mixture through an immobilized lipase packed bed reactor at different substrate/hexane ratios, as well as in absence of solvent. In the latter case, STAG with 51% CA and 13% DHA were obtained at 73 h. This result indicates that with this catalyst an acceptable reaction rate was attained in absence of solvent. A structural analysis by the pancreatic lipase method carried out to STAG with 45% CA and 16% DHA indicated that 91% of the CA incorporated is located in positions 1 and 3, and that 51% of the DHA is located in position 2 (MLM structure). This position is also rich in palmitic, eicosapentaenoic and oleic acids.After the acidolysis reaction a mixture of STAG and free fatty acids was obtained. The recovery of STAG from this reaction mixture is difficult because of the high content of free fatty acids. A separation method based on the neutralization of the free fatty acids with a KOH hydroalcoholic solution has been developed. By this procedure pure (100%) STAG were obtained with a recovery yield of 80%.     

Dimethyl carbonate as potential reactant in non-catalytic biodiesel production by supercritical method

In this study, the non-catalytic supercritical method has been studied in utilizing dimethyl carbonate. It was demonstrated that, the supercritical dimethyl carbonate process without any catalysts applied, converted triglycerides to fatty acid methyl esters with glycerol carbonate and citramalic acid as by-products, while free fatty acids were converted to fatty acid methyl esters with glyoxal. After 12 min of reaction at 350 degrees C/20 MPa, rapeseed oil treated with supercritical dimethyl carbonate reached 94% (w/w) yield of fatty acid methyl ester. The by-products from this process which are glycerol carbonate and citramalic acid are much higher in value than glycerol produced by the conventional process. In addition, the yield of the fatty acid methyl esters as biodiesel was almost at par with supercritical methanol method. Therefore, supercritical dimethyl carbonate process can be a good candidate as an alternative biodiesel production process.     

A newly isolated fungal strain used as whole‐cell biocatalyst for biodiesel production from palm oil

A strain of Aspergillus niger isolated from atmospherically exposed bread and Jatropha curcas seed was utilized as a whole‐cell biocatalyst for palm oil methanolysis to produce fatty acid methyl esters (FAME), or biodiesel. The A. niger strain had a lipase activity of 212.58 mU mL^?1 after 144 h incubation at 25 °C with an initial pH value of 6.5, using 7% polypeptone (w/w on basal medium) as the nitrogen source and 3% olive oil (w/w on basal medium) as a carbon source. The A. niger cells spontaneously immobilized within polyurethane biomass support particles (BSPs) during submerged fermentation. Thereafter, the methanolysis of palm oil was achieved via a three‐step addition of methanol in the presence of BSPs‐immobilized with A. niger cells. The influence of water content, reaction temperature and enzyme concentration on reaction rate was investigated. An 8% water content and a temperature of 40 °C in the presence of 30 immobilized BSPs, resulted in an 87% FAME yield after 72 h.     

A continuous process for biodiesel production in a fixed bed reactor packed with cation-exchange resin as heterogeneous catalyst

Continuous esterification of free fatty acids (FFA) from acidified oil with methanol was carried out with NKC-9 cation-exchange resin in a fixed bed reactor with an internal diameter of 25 mm and a height of 450 mm to produce biodiesel. The results showed that the FFA conversion increased with increases in methanol/oil mass ratio, reaction temperature and catalyst bed height, whereas decreased with increases in initial water content in feedstock and feed flow rate. The FFA conversion kept over 98.0% during 500 h of continuous esterification processes under 2.8:1 methanol to oleic acid mass ratio, 44.0 cm catalyst bed height, 0.62 ml/min feed flow rate and 65°C reaction temperature, showing a much high conversion and operational stability. Furthermore, the loss of sulfonic acid groups from NKC-9 resin into the production was not found during continuous esterification. In sum, NKC-9 resin shows the potential commercial applications to esterification of FFA.     

Biodiesel production from high acid value waste frying oil catalyzed by superacid heteropolyacid

Transesterification of waste cooking oil with high acid value and high water contents using heteropolyacid H3PW12O40 x 6H2O (PW12) as catalyst was investigated. The hexahydrate form of PW(12) was found to be the most promising catalyst which exhibited highest ester yield 87% for transesterification of waste cooking oil and ester yield 97% for esterification of long-chain palmitic acid, respectively. The PW12 acid catalyst shows higher activity under the optimized reaction conditions compared with conventional homogeneous catalyst sulfuric acid, and can easily be separated from the products by distillation of the excess methanol and can be reused more times. The most important feature of this catalyst is that the catalytic activity is not affected by the content of free fatty acids (FFAs) and the content of water in the waste cooking oil and the transesterification can occur at a lower temperature (65 degrees C), a lower methanol oil ratio (70:1) and be finished within a shorter time. The results illustrate that PW12 acid is an excellent water-tolerant and environmentally benign acid catalyst for production of biodiesel from waste cooking oil.     

Lipase-catalyzed biodiesel production from waste activated bleaching earth as raw material in a pilot plant

The production of fatty acid methyl esters (FAMEs) from waste activated bleaching earth (ABE) discarded by the crude oil refining industry using lipase from Candida cylindracea was investigated in a 50-L pilot plant. Diesel oil or kerosene was used as an organic solvent for the transesterification of triglycerides embedded in the waste ABE. When 1% (w/w) lipase was added to waste ABE, the FAME content reached 97% (w/w) after reaction for 12 h at 25 degrees C with an agitation rate of 30 rpm. The FAME production rate was strongly dependent upon the amount of enzyme added. Mixtures of FAME and diesel oil at ratios of 45:55 (BDF-45) and 35:65 (BDF-35) were assessed and compared with the European specifications for biodiesel as automotive diesel fuel, as defined by pr EN 14214. The biodiesel quality of BDF-45 met the EN 14214 standard. BDF-45 was used as generator fuel, and the exhaust emissions were compared with those of diesel oil. The CO and SO2 contents were reduced, but nitrogen oxide emission increased by 10%. This is the first report of a pilot plant study of lipase-catalyzed FAME production using waste ABE as a raw material. This result demonstrates a promising reutilization method for the production of FAME from industrial waste resources containing vegetable oils for use as a biodiesel fuel.     

Direct preparation of biodiesel from rapeseed oil leached by two-phase solvent extraction

A new method which coupled the two-phase solvent extraction (TSE) with the synthesis of biodiesel was studied. Investigations were carried out on transesterification of methanol with oil-hexane solution coming from TSE process in the presence of sodium hydroxide as the catalyst. Biodiesel (fatty acid methyl esters) were the products of transesterification. The influential factors of transesterification, such as reaction time, catalyst concentration, mole ratio of methanol to oil and reaction temperature were optimized. The results showed that the optimal reaction parameters were sodium hydroxide concentration 1.1% by weight of rapeseed oil, mole ratio of methanol to oil 9:1, reaction time 120 min, and reaction temperature 55-60 degrees C. Under these conditions, the TG conversion would rise up to 98.2%. Based on the new method, biodiesel production process could be simplified and the biodiesel cost could be reduced.     

Immobilization of steapsin lipase on macroporous immobead-350 for biodiesel production in solvent free system

Commercially available steapsin lipase was immobilized on macroporous polymer beads (IB-350) and further investigated for biodiesel production under solvent free conditions. The fatty acid methyl ester (biodiesel) synthesis was carried out by the methanolysis of fresh and used cooking sunflower oil. The enzymatic reaction for biodiesel synthesis was optimized with various reaction parameters and the obtained reaction conditions were 1: 6 molar ratio (oil: methanol), 50 mg biocatalyst and 20% water content at 45°C for 48 h under solvent free conditions. It was observed that 94% of biodiesel was produced under the optimized reaction conditions. The four step addition of methanol at the interval of 12 h was found to be more effective. Moreover the biocatalyst was effectively reused for four consecutive recycles and was appreciably stable for 90 days. The results obtained highlight potential of immobilized steapsin lipase for biodiesel production.     

Statistical analysis and optimization of biodiesel production from waste coffee grounds by a two-step process

Biodiesel was produced using waste coffee grounds (WCGs) via a two-step process comprising lipid extraction and subsequent transesterification steps. Each step was statistically analyzed, and optimum conditions for each step were suggested. WCGs were found to have 16.4% lipid content with 1.9% free fatty acid (FFA) content. The liquid-solid ratio (LSR) significantly influenced lipid extraction from WCGs, while extraction time and temperature did not; 92.7% of lipid extraction efficiency was achieved at 13.7 mL-hexane/g-WCGs, 30 min of extraction time, and 25°C. Owing to the relatively low FFA content, an alkaline catalyst (NaOH) reaction was used that requires less amount of catalyst, methanol, and shorter reaction time compared to an acid catalyst reaction. Reaction time and temperature were the major factors affecting biodiesel conversion, and 94.0% of biodiesel conversion was obtained at optimum conditions for transesterification: 0.5% catalyst, 1.5 mL-methanol/g-lipid, 45°C, and 9 h of reaction time. With the use of statistical analysis tools, high lipid extraction efficiency and biodiesel conversion were achieved at relatively mild conditions, which would reduce biodiesel production cost substantially.     

Biodiesel production using a membrane reactor

The immiscibility of canola oil in methanol provides a mass-transfer challenge in the early stages of the transesterification of canola oil in the production of fatty acid methyl esters (FAME or biodiesel). To overcome or rather, exploit this situation, a two-phase membrane reactor was developed to produce FAME from canola oil and methanol. The transesterification of canola oil was performed via both acid- or base-catalysis. Runs were performed in the membrane reactor in semi-batch mode at 60, 65 and 70 degrees C and at different catalyst concentrations and feed flow rates. Increases in temperature, catalyst concentration and feedstock (methanol/oil) flow rate significantly increased the conversion of oil to biodiesel. The novel reactor enabled the separation of reaction products (FAME/glycerol in methanol) from the original canola oil feed. The two-phase membrane reactor was particularly useful in removing unreacted canola oil from the FAME product yielding high purity biodiesel and shifting the reaction equilibrium to the product side.     

Synthesis of structured lipid with balanced omega-3: Omega-6 ratio by lipase-catalyzed acidolysis reaction: Optimization of reaction using response surface methodology

The present study deals with the production of structured lipid containing omega-3 and omega-6 fatty acids in the ratio of 1:1 by incorporating omega-3 fatty acids (α-linolenic acid) from linseed oil into groundnut oil using lipase (Lipozyme IM from Rhizomucor miehei) catalyzed acidolysis reaction in hexane. The reaction conditions were optimized by response surface methodology with a four-variable five-level central composite rotatable experimental design. The influence of four independent parameters, namely ratio of fatty acid concentrate from linseed to groundnut oil (0.66–1.98, w/w), reaction temperature (30–60 °C), enzyme concentration (1–5%) and reaction time (2–54 h) on omega-3 fatty acids incorporation into groundnut oil were optimized. Optimal conditions for the structured lipid containing omega-3 to omega-6 fatty acids in the ratio of 1:1 were determined to be; enzyme concentration 3.75% (w/w), temperature 37.5 °C, incubation time 30.81 h and ratio of free fatty acid concentrate from linseed oil to groundnut oil 1.16 (w/w).     

Lipase-catalysed production of biodiesel fuel from some Nigerian lauric oils

Fatty acids esters were produced from two Nigerian lauric oils, palm kernel oil and coconut oil, by transesterification of the oils with different alcohols using PS30 lipase as a catalyst. In the conversion of palm kernel oil to alkyl esters (biodiesel), ethanol gave the highest conversion of 72%, t-butanol 62%, 1-butanol 42%, n-propanol 42% and iso-propanol 24%, while only 15% methyl ester was observed with methanol. With coconut oil, 1-butanol and iso-butanol achieved 40% conversion, 1-propanol 16% and ethanol 35%, while only traces of methyl esters were observed using methanol. Studies on some fuel properties of palm kernel oil and its biodiesel showed that palm kernel oil had a viscosity of 32.40 mm2/s, a cloud point of 28 degrees C and a pour point of 22 degrees C, while its biodiesel fuel had a viscosity of 9.33 mm2/s, a cloud point of 12 degrees C and a pour point of 8 degrees C. Coconut oil had a viscosity of 28.58 mm(2)/s, a cloud point of 27 degrees C and a pour point of 20 degrees C, while its biodiesel fuel had a viscosity of 7.34 mm2/s, a cloud point of 5 degrees C and a pour point of -8 degrees C. Some of the fuel properties compared favourably with international biodiesel specifications.     

Conversion of acid oil by-produced in vegetable oil refining to biodiesel fuel by immobilized Candida antarctica lipase

Acid oil, which is a by-product in vegetable oil refining, mainly contains free fatty acids (FFAs) and acylglycerols, and is a candidate of materials for production of biodiesel fuel. A mixture (acid oil model) of refined FFAs and vegetable oil was recently reported to be converted to fatty acid methyl esters (FAMEs) at >98% conversion by a two-step reaction system comprising methyl esterification of FFAs and methanolysis of acylglycerols using immobilized Candida antarctica lipase. The two-step system was thus applied to conversion of acid oil by-produced in vegetable oil refining to biodiesel fuel. Under similar conditions that were determined by using acid oil model, however, the lipase was unstable and was not durable for repeated use. The inactivation of the lipase was successfully avoided by addition of excess amounts of methanol (MeOH) in the first-step reaction, and by addition of vegetable oil and glycerol in the second-step reaction. Hence, the first-step reaction was conducted by shaking a mixture of 66 wt% acid oil (77.9 wt% FFAs, 10.8 wt% acylglycerols) and 34 wt% MeOH with 1 wt% immobilized lipase, to convert FFAs to their methyl esters. The second-step reaction was performed by shaking a mixture of 52.3 wt% dehydrated first-step product (79.7 wt% FAMEs, 9.7 wt% acylglycerols), 42.2 wt% rapeseed oil, and 5.5 wt% MeOH using 6 wt% immobilized lipase in the presence of additional 10 wt% glycerol, to convert acylglycerols to FAMEs. The resulting product was composed of 91.1 wt% FAMEs, 0.6 wt% FFAs, 0.8 wt% triacylglycerols, 2.3 wt% diacylglycerols, and 5.2 wt% other compounds. Even though each step of reaction was repeated every 24 h by transferring the immobilized lipase to the fresh substrate mixture, the composition was maintained for >100 cycles.