Production of biodiesel and lactic acid from rapeseed oil using sodium silicate as catalyst

Biodiesel and lactic acid from rapeseed oil was produced using sodium silicate as catalyst. The transesterification in the presence of the catalyst proceeded with a maximum yield of 99.6% under optimized conditions [3% (w/w) sodium silicate, methanol/oil molar ratio 9/1, reaction time 60 min, reaction temperature 60 °C, and stirring rate 250 rpm]. After six consecutive transesterification reactions, the catalyst was collected and used for catalysis of the conversion of glycerol to lactic acid. A maximum yield of 80.5% was achieved when the reaction was carried out at a temperature of 300 °C for 90 min. Thus, sodium silicate is an effective catalyst for transesterification and lactic acid production from the biodiesel by-product, glycerol.     

Transesterification of palm oil to methyl ester on activated carbon supported calcium oxide catalyst

In this study, methyl ester (ME) was produced by transesterification of palm oil (CPO) (cooking grade) using activated carbon supported calcium oxide as a solid base catalyst (CaO/AC). Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the effect of reaction time, molar ratio of methanol to oil, reaction temperature and catalyst amount on the transesterification process. The optimum condition for CPO transesterification to methyl ester was obtained at 5.5 wt.% catalyst amount, 190 °C temperature, 15:1 methanol to oil molar ratio and 1 h 21 min reaction time. At the optimum condition, the ME content was 80.98%, which is well within the predicted value of the model. Catalyst regeneration studies indicate that the catalyst performance is sustained after two cycles.     

Biodiesel production from rubber seed oil using poly (sodium acrylate) supporting NaOH as a water-resistant catalyst

Poly (sodium acrylate) supporting NaOH (NaOH/NaPAA) was prepared by in situ polymerization of aqueous solution of acrylic acid with an over-neutralization by adding excess of NaOH. NaOH/NaPAA presented a promising selectivity for water absorbency and good water retention with negligible swelling capacity in the organic solvents of methanol, glycerol, rubber seed oil methyl esters, and rubber seed oil. NaOH/NaPAA catalysts showed a basic strength of 15.0 < H_ < 18.4 and their basicity increased with the increase of the NaOH loading amount. NaOH/NaPAA catalysts exhibited almost the same catalytic activity in the transesterification of rubber seed oil with methanol under the optimized reaction conditions compared to conventional homogeneous NaOH catalyst. Furthermore, the functional absorbent/catalyst system presented a good water resistance in the transesterification which retained high catalytic activity when a water concentration in the reaction system was less than 2 wt.%.     

Bio-diesel production directly from the microalgae biomass of Nannochloropsis by microwave and ultrasound radiation

This work offers an optimized method for the direct conversion of harvested Nannochloropsis algae into bio-diesel using two novel techniques. The first is a unique bio-technology-based environmental system utilizing flue gas from coal burning power stations for microalgae cultivation. This method reduces considerably the cost of algae production. The second technique is the direct transesterification (a one-stage method) of the Nannochloropsis biomass to bio-diesel production using microwave and ultrasound radiation with the aid of a SrO catalyst. These two techniques were tested and compared to identify the most effective bio-diesel production method. Based on our results, it is concluded that the microwave oven method appears to be the most simple and efficient method for the one-stage direct transesterification of the as-harvested Nannochloropsis algae.     

Preparation,application, and optimization of Zn/Al complex oxides for biodiesel production under sub-critical conditions

Biodiesel produced by transesterification is a promising green fuel in the future. A new heterogeneous catalyst, Zn/Al complex oxide, was prepared for biodiesel production. The results showed that the catalyst derived from a hydrotalcite-like precursor with a zinc/aluminum atom ratio of 3.74:1 and calcined at 450 °C gave the highest conversion of 84.25%. Analysis of XRD, XPS, FI-IF, TG-DTA, BET and alkalinity tests demonstrated that it is the unique structure of hydrotalcite-like compound precursor that gave the catalyst a high alkalinity greater than 11.1. The optimal reaction condition for Zn/Al complex oxide was under methanol sub-critical condition: 200 °C, 2.5 MPa, 1.4% (wt) catalyst dosage, and 24:1 methanol to oil ratio. Under these conditions, the conversion reached 84.25% after 90 min, which was better than Mg/Al complex oxides. The excellent tolerance to water and free fatty acid was exhibited when the oil feed had fewer than 6% FFA or 10% water content with a conversion greater than 80%.     

Direct Transesterification of Castor and Jatropha Seeds for FAME Production by Microwave and Ultrasound Radiation Using a SrO Catalyst

In the present study, we report on an optimized method for fatty acid methyl esters (FAME) production from castor and jatropha seeds. In order to identify the most effective biodiesel production method, we have compared three two-stage methods, each consisting of oil extraction (the first step) and FAME production by transesterification (the second step), with the same three techniques each conducted in one stage, i.e., direct transesterification. The three techniques are conventional heating, sonochemistry, and microwave radiation. The FAME product was analyzed by ¹H NMR spectroscopy and GC-MS. The SrO catalyst was reused successfully, together with seeds containing oil residues, for 10 cycles. The highest yield of FAME, 57.2?% of the total weight of the castor seeds, and a conversion of castor oil to FAME of 99.95?% were achieved in a one-stage method lasting 5?min using microwave radiation as a heat source. Using jatropha seeds leads to a yield of 41.1?% and a 99.7?% conversion of triglyceride to FAME under microwave irradiation in a one-stage method. The direct transesterification by sonication resulted in yields of 48.2?% and 32.9?%, and a 93.6?% conversion from castor and jatropha seeds, respectively.     

Characterisation of a thermo-alkali-stable lipase from oil-contaminated soil using a metagenomic approach

Lipases are widely used for a variety of biotechnological applications. Screening these industrial enzymes directly from environmental microorganisms is a more efficient and practical approach than conventional cultivation-dependent methods. Combined with activity-based functional screening, six clones with lipase activity were detected and a gene (termed lipZ01) isolated from a target clone with the highest lipase activity was cloned from an oil-contaminated soil-derived metagenomic library and then sequenced. Gene lipZ01 was expressed in Pichia pastoris GS115 and the molecular weight of the recombinant lipase LipZ01 was estimated by electrophoresis analysis to be approximately 50 kDa. The maximum activity of the purified lipase was 42 U/mL, and the optimum reaction temperature and pH value were 45 °C and 8.0, respectively. The enzyme was highly stable in the temperature range 35–60 °C and under alkaline conditions (pH 7–10). The presence of Ca²⁺ and Mn²⁺ ions could significantly enhance the activity of the lipase. The purified lipase preferentially hydrolysed triacylglycerols with acyl chain lengths ≥8 carbon atoms, and the conversion degree of biodiesel production was nearly 92% in a transesterification reaction using olive oil and methanol. Some attractive properties suggested that the recombinant lipase may be valuable in industrial applications.     

Enzymatic conversion of sunflower oil to biodiesel in a solvent-free system: Process optimization and the immobilized system stability

The feasibility of using the commercial immobilized lipase from Candida antarctica (Novozyme 435) to synthesize biodiesel from sunflower oil in a solvent-free system has been proved. Using methanol as an acyl acceptor and the response surface methodology as an optimization technique, the optimal conditions for the transesterification has been found to be: 45 ^oC, 3% of enzyme based on oil weight, 3:1 methanol to oil molar ratio and with no added water in the system. Under these conditions, >99% of oil conversion to fatty acid methyl ester (FAME) has been achieved after 50 h of reaction, but the activity of the immobilized lipase decreased markedly over the course of repeated runs. In order to improve the enzyme stability, several alternative acyl acceptors have been tested for biodiesel production under solvent-free conditions. The use of methyl acetate seems to be of great interest, resulting in high FAME yield (95.65%) and increasing the half-life of the immobilized lipase by about 20.1 times as compared to methanol. The reaction has also been verified in the industrially feasible reaction system including both a batch stirred tank reactor and a packed bed reactor. Although satisfactory performance in the batch stirred tank reactor has been achieved, the kinetics in a packed bed reactor system seems to have a slightly better profile (93.6 ± 3.75% FAME yield after 8–10 h), corresponding to the volumetric productivity of 48.5 g/(dm³ h). The packed bed reactor has operated for up to 72 h with almost no loss in productivity, implying that the proposed process and the immobilized system could provide a promising solution for the biodiesel synthesis at the industrial scale.     

Microwave assisted alkali-catalyzed transesterification of Pongamia pinnata seed oil for biodiesel production

In this study, microwave assisted transesterification of Pongamia pinnata seed oil was carried out for the production of biodiesel. The experiments were carried out using methanol and two alkali catalysts i.e., sodium hydroxide (NaOH) and potassium hydroxide (KOH). The experiments were carried out at 6:1 alcohol/oil molar ratio and 60 °C reaction temperature. The effect of catalyst concentration and reaction time on the yield and quality of biodiesel was studied. The result of the study suggested that 0.5% sodium hydroxide and 1.0% potassium hydroxide catalyst concentration were optimum for biodiesel production from P. pinnata oil under microwave heating. There was a significant reduction in reaction time for microwave induced transesterification as compared to conventional heating.     

Esterification of acidified oil with methanol by SPES/PES catalytic membrane

A sulfonated polyethersulfone (SPES)/polyethersulfone (PES) blend catalytic membrane was prepared and used as a heterogeneous catalyst in the esterification of the acidified oil (acid value 153 mg KOH/g) with methanol for producing biodiesel. The results showed that the free fatty acids conversion reached 97.6% using SPES/PES catalytic membrane under the optimal esterification conditions. Meanwhile, the SPES/PES membrane with 20.3% degree of sulfonation showed a good catalytic stability. A pseudo-homogeneous kinetic model was established. The results indicated that the reaction rate constant increased with increasing methanol/acidified oil molar ratio, the loading of catalytic membrane and reaction temperature. The reaction order was 2 and the activation energy decreased from 74.65 to 21.07 kJ/mol with increasing catalytic membrane loading from 0 to 0.135 meq/g(oil). It implies that the esterification is not diffusively controlled but kinetically controlled. The predicted results were in good agreement with the experimental data.     

Production of biodiesel from mixed waste vegetable oil using an aluminium hydrogen sulphate as a heterogeneous acid catalyst

Al(HSO₄)₃ heterogeneous acid catalyst was prepared by the sulfonation of anhydrous AlCl₃. This catalyst was employed to catalyze transesterification reaction to synthesis methyl ester when a mixed waste vegetable oil was used as feedstock. The physical and chemical properties of aluminum hydrogen sulphate catalyst were characterized by scanning electron microscopy (SEM) measurements, energy dispersive X-ray (EDAX) analysis and titration method. The maximum conversion of triglyceride was achieved as 81 wt.% with 50 min reaction time at 220 °C, 16:1 molar ratio of methanol to oil and 0.5 wt.% of catalyst. The high catalytic activity and stability of this catalyst was related to its high acid site density (-OH, Brönsted acid sites), hydrophobicity that prevented the hydration of -OH group, hydrophilic functional groups (-SO₃H) that gave improved accessibility of methanol to the triglyceride. The fuel properties of methyl ester were analyzed. The fuel properties were found to be observed within the limits of ASTM D6751.     

Optimization Studies and Chemical Kinetics of Silica Sulfuric Acid-Catalyzed Biodiesel Synthesis from Waste Cooking Oil

In the present study conversion of waste cooking oil to biodiesel has been carried out via simultaneous esterification and transesterification reaction over silica sulfuric acid as a solid acid catalyst. The process variables that influence the fatty acid methyl ester (FAME) conversion, such as reaction temperature, reaction time, catalyst concentration and methanol to oil molar ratio were investigated and optimized using Taguchi method. Highest FAME production obtained under the optimized condition was 98.66 %. Analysis of variance revealed that temperature was the most significant factor effecting the FAME production among four factors studied. From the kinetic study, the reaction was found to follow pseudo first-order kinetics and rate constant of the reaction under optimum condition was 0.00852 min^?1.     

A packed bed membrane reactor for production of biodiesel using activated carbon supported catalyst

In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO₂/Al₂O₃ membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70 °C employing 157.04 g catalyst per unit volume of the reactor and 0.21 cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor.     

Fractions composition study of the pyrolysis oil obtained from sewage sludge treatment plant

In this work the parameters of Low Temperature Conversion - LTC were applied in a centrifuged sludge from a sewage treatment plant located in Rio de Janeiro, Brazil. Before the conversion, the sludge was dried and analyzed by TGA to observe its behavior with increasing temperature. The chemical composition of the crude pyrolysis oil was analyzed by FTIR, ¹H NMR and GC-MS. The results showed that the oil is a mixture of hydrocarbons, oxygenated and nitrogenated compounds. Using a catalytic treatment it was possible to fractionate the oil where the predominant constituents were hydrocarbons showing that the cracking was effective. An important result was the difference between the calorific value of dry sludge (10 MJ kg⁻¹), the pyrolysis oil (36 MJ kg⁻¹) and one of the fractions separated by catalytic cracking (40 MJ kg⁻¹) when compared with commercial diesel (45 MJ kg⁻¹).     

Enzymatic transesterification of olive oil and its precursors

The effect of different solvents and three different acyl acceptors on the transesterification of triolein (as a model compound) was investigated. The yield of biodiesel (methyl or ethyl ester) was monitored as a function of time. The yield of the product was also determined in a solvent-free system for two different modes of stirring. The results indicate that the highest yield is obtained in a solvent-free system with mechanical stirring. Methyl acetate is also effective as a solvent and acyl acceptor. Biodiesel was also produced by transesterification of triglycerides (triolein) present in olive oil with methanol and Novozym® 435. The effect of the molar ratio of methanol to triolein, mode of methanol addition, enzyme activity and reaction temperature on overall conversion and yield was determined. The final conversion and yield of biodiesel after a reaction time of 24 h were unaffected by changes in these parameters over the range studied. Preliminary findings indicate that the results obtained from small scale reactors and fresh oil can be extended to larger reactors and used oil.     

Enzymatic transesterification of olive oil and its precursors

The effect of different solvents and three different acyl acceptors on the transesterification of triolein (as a model compound) was investigated. The yield of biodiesel (methyl or ethyl ester) was monitored as a function of time. The yield of the product was also determined in a solvent-free system for two different modes of stirring. The results indicate that the highest yield is obtained in a solvent-free system with mechanical stirring. Methyl acetate is also effective as a solvent and acyl acceptor. Biodiesel was also produced by transesterification of triglycerides (triolein) present in olive oil with methanol and Novozym® 435. The effect of the molar ratio of methanol to triolein, mode of methanol addition, enzyme activity and reaction temperature on overall conversion and yield was determined. The final conversion and yield of biodiesel after a reaction time of 24 h were unaffected by changes in these parameters over the range studied. Preliminary findings indicate that the results obtained from small scale reactors and fresh oil can be extended to larger reactors and used oil.     

Synthesis and properties of fatty acid starch esters

Being completely bio-based, fatty acid starch esters (FASEs) are attractive materials that represent an alternative to crude oil-based plastics. In this study, two synthesis methods were compared in terms of their efficiency, toxicity and, especially, product solubility with starch laurate (C₁₂) as model compound. Laurates (DS > 2) were obtained through transesterification of fatty acid vinylesters in DMSO or reaction with fatty acid chlorides in pyridine. The latter lead to higher DS-values in a shorter reaction time. But due to the much better solubility of the products compared to lauroyl chloride esterified ones, vinylester-transesterification was preferred to optimize reaction parameters, where reaction time could be shortened to 2 h. FASEs C₆–C₁₈ were also successfully prepared via transesterification. To determine the DS of the resulting starch laurates, the efficient ATR-IR method was compared with common methods (elementary analysis, ¹H NMR). Molar masses (M_w) of the highly soluble starch laurates were analyzed using SEC-MALLS (THF). High recovery rates (>80%) attest to the outstanding solubility of products obtained through transesterification, caused by a slight disintegration during synthesis. Particle size distributions (DLS) demonstrated stable dissolutions in CHCl₃ of vinyl laurate esterified – contrary to lauroyl chloride esterified starch. For all highly soluble FASEs (C₆–C₁₈), formation of concentrated solutions (10 wt%) is feasible.     

Catalytic Packed-Bed Reactor Configuration for Biodiesel Production Using Waste Oil as Feedstock

Pumice, a natural porous silica material, exchanged with potassium is an efficient heterogeneous particulate catalytic material for triglycerides and free fatty acids transesterification reaction from sunflower oil and waste frying oil at low temperature. In this work, a packed-bed catalytic configuration reactor using this catalytic material was developed for biodiesel fuel production from sunflower oil and frying oil feedstock. Reactor operation variables as methanol/oil molar ratio, catalyst amount, reaction time, and reaction temperature were studied. Results were compared with those obtained from the same transesterification reaction proceeding in a slurry batch reactor. The packed-bed catalytic reactor configuration can be useful in order to minimize catalyst mechanical damage occurring in the slurry reactor due to continuous stirring. The possibility of using a packed-bed reactor shows some advantages because the catalyst stays confined in the reactor bed and the reaction products can be easily separated, besides the mechanical stability of the catalyst particles is achieved.     

A critical comparison of methyl and ethyl esters production from soybean and rice bran oil in the presence of microwaves

Transesterification of vegetable oils (from soybeans and rice bran) into methyl and ethyl esters using a batch microwave system was investigated in this study. A critical comparison between the two alcohols was performed in terms of yields, quality, and reaction kinetics. Parameters tested were temperature (60, 70 and 80 °C) and time (5, 10, 15 and 20 min). At all tested conditions, more than 96% conversion rates were obtained for both ethanol and methanol. Use of microwave technology to assist the transesterification process resulted in faster reaction times and reduced catalyst requirement (about ten-fold decrease). Methanol required lower alcohol:oil ratios than normally used in conventional heating, whereas ethanol required higher molar ratios. All esters produced using this method met ASTM biodiesel quality specifications. Methanol performed better in terms of performance and costs, while ethanol may have some environmental and safety benefits.     

Enzyme catalyzed transesterification of waste cooking oil with dimethyl carbonate

The detrimental effects of waste cooking oil on sewer system attracted attention toward its proper management and reusing this waste oil for making biodiesel provides commercial and environmental advantage. In the present study, biodiesel has been successfully produced from waste cooking oil and dimethyl carbonate by transesterification, instead of the conventional alcohol. In this optimization study, the effect of various reaction conditions such as solvent, time and temperature, molar ratio of DMC to oil, enzyme loading and reusability, on the yield of fatty acid methyl ester (FAME) has been studied. The Maximum conversion of FAMEs achieved was 77.87% under optimum conditions (solvent free system, reaction time of 24 h, 60 °C, molar ratio of DMC to oil 6:1, catalyst amount 10% Novozym 435 (based on the oil weight)). Moreover, there was no obvious loss in the conversion after lipases were reused for 6 batches under optimized conditions.