Ethanesulfonic acid-based esterification of industrial acidic crude palm oil for biodiesel production

An industrial grade acidic crude palm oil (ACPO) pre-treatment process was carried out using ethanesulfonic acid (ESA) as a catalyst in the esterification reaction. ESA was used in different dosages to reduce free fatty acid (FFA) to a minimum level for the second stage of biodiesel production via alkaline transesterification reaction. Different process operating conditions were optimized such as ESA dosage (0.25-3.5% wt/wt), methanol to ACPO molar ratio (1:1-20:1), reaction temperature (40-70 °C), and reaction time (3-150 min). This study revealed the potential use of abundant quantities of ACPO from oil palm mills for biodiesel production. The lab scale results showed the effectiveness of the pre-treatment process using ESA catalyst. Three consecutive catalyst recycling runs were achieved without significant degradation in its performance. Second and third reuse runs needed more reaction time to achieve the target level of FFA content. Esterification and transesterification using ESA and KOH respectively is proposed for biodiesel industrial scale production. The produced biodiesel meets the international standards specifications for biodiesel fuel (EN 14214 and ASTM D6751).     

Simultaneous conversion of free fatty acids and triglycerides to biodiesel by immobilized Aspergillus oryzae expressing Fusarium heterosporum lipase

The presence of high levels of free fatty acids (FFA) in oil is a barrier to one‐step biodiesel production. Undesirable soaps are formed during conventional chemical methods, and enzyme deactivation occurs when enzymatic methods are used. This work investigates an efficient technique to simultaneously convert a mixture of free fatty acids and triglycerides (TAG). A partial soybean hydrolysate containing 73.04% free fatty acids and 24.81% triglycerides was used as a substrate for the enzymatic production of fatty acid methyl ester (FAME). Whole‐cell Candida antarctica lipase B‐expressing Aspergillus oryzae, and Novozym 435 produced only 75.2 and 73.5% FAME, respectively. Fusarium heterosporum lipase‐expressing A. oryzae produced more than 93% FAME in 72 h using three molar equivalents of methanol. FFA and TAG were converted simultaneously in the presence of increasing water content that resulted from esterification. Therefore, F. heterosporum lipase with a noted high level of tolerance of water could be useful in the industrial production of biodiesel from feedstock that has high proportion of free fatty acids.     

Lipase-catalysed synthesis of ester oils from biodiesel by-products

Ester oils obtained from natural long-chain fatty acids and alcohols are versatile substitutes for many petroleum-based products. Their efficient synthesis with the solvent-free esterification of free fatty acids (FFA) from by-products of biodiesel fabrication and 2-ethyl-1-hexanol with immobilised lipase from Thermomyces lanuginosa was investigated. The immobilisation of the biocatalyst in static emulsion yielded a specific esterification activity that was higher by a factor of 4.9-9.4 than the activity of the native enzyme. Favourable properties of the silicone-based immobilisation matrix in terms of stability and immobilisation yield were observed. In biodiesel by-products, the immobilised lipase catalysed the esterification of FFA as well as the transesterification of residual fatty acid methyl esters (FAME) to the desired ester oils. A conversion of 90% FFA and 35% FAME gave a total yield of 60%. The inactivation coefficients during repeated use in a stirred-tank reactor with intermittent pressure reduction were exceptionally low.     

Lipase-catalysed synthesis of ester oils from biodiesel by-products

Ester oils obtained from natural long-chain fatty acids and alcohols are versatile substitutes for many petroleum-based products. Their efficient synthesis with the solvent-free esterification of free fatty acids (FFA) from by-products of biodiesel fabrication and 2-ethyl-1-hexanol with immobilised lipase from Thermomyces lanuginosa was investigated. The immobilisation of the biocatalyst in static emulsion yielded a specific esterification activity that was higher by a factor of 4.9–9.4 than the activity of the native enzyme. Favourable properties of the silicone-based immobilisation matrix in terms of stability and immobilisation yield were observed. In biodiesel by-products, the immobilised lipase catalysed the esterification of FFA as well as the transesterification of residual fatty acid methyl esters (FAME) to the desired ester oils. A conversion of 90% FFA and 35% FAME gave a total yield of 60%. The inactivation coefficients during repeated use in a stirred-tank reactor with intermittent pressure reduction were exceptionally low.     

脂肪酶催化合成生物柴油的研究

生物柴油是用动植物油脂或长链脂肪酸与甲醇等低碳醇合成的脂肪酸甲酯,是一种替代能源。这里探讨了生物法制备生物柴油的过程,采用脂肪酶酯化和酯交换两条工艺路线进行催化合成。深入研究制备过程中,不同脂肪酶、酶的用量和纯度、有机溶剂、低碳醇的抑制作用、吸水剂的作用、反应时间和进程、底物的特异性和底物摩尔比等参数对酯化过程的影响。试验结果表明,采用最佳酯化反应参数和分批加入甲醇并用硅胶作脱水剂的工艺过程,酯化率可以达到92％,经分离纯化后的产品GC分析的纯度可达98％以上,固定化酶的使用半衰期可达到360h。同时对酯交换制备生物柴油过程中,甲醇的用量和甲醇的加入方式对脂肪酶催化过程的影响作了初步研究,优化后的酯交换率可达到83％。     

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.     

Integrated enzymatic production of specific structured lipid and phytosterol ester compositions

Mixtures of specific structured lipids and phytosterol esters, valuable food components, were synthesized by an enzymatic one-pot process in organic-solvent-free medium starting from a mixture of phytosterol, caprylic acid and sunflower oil. Nine biocatalysts, seven commercially available lipases and two air-dried solid state (SSF) fermentation preparations of Aspergillus oryzae NRRL 6270 (AoSSF) and Aspergillus sojae NRRL 6271 (AsSSF), were screened for lipase activity in the transesterification reactions of sunflower oil with caprylic acid and for sterol esterase activity in the direct esterification of phytosterols with free fatty acids. The best process variant using a sequence of sterol esterase (AoSSF)-catalyzed esterification reaction of the free fatty acids and phytosterols, followed by water removal in vacuum and lipase-catalyzed transesterification with immobilized lipase from Rhizomucor miehei (Lipozyme) resulted in 92.1% conversion to phytosterol esters and 44.1% conversion to triacylglycerols containing two caprylic esters.     

Conversion of Solid Organic Wastes into Oil via Boettcherisca peregrine (Diptera: Sarcophagidae) Larvae and Optimization of Parameters for Biodiesel Production

The feedstocks for biodiesel production are predominantly from edible oils and the high cost of the feedstocks prevents its large scale application. In this study, we evaluated the oil extracted from Boettcherisca peregrine larvae (BPL) grown on solid organic wastes for biodiesel production. The oil contents detected in the BPL converted from swine manure, fermentation residue and the degreased food waste, were 21.7%, 19.5% and 31.1%, respectively. The acid value of the oil is 19.02 mg KOH/g requiring a two-step transesterification process. The optimized process of 12∶1 methanol/oil (mol/mol) with 1.5% H₂SO₄ reacted at 70°C for 120 min resulted in a 90.8% conversion rate of free fatty acid (FFA) by esterification, and a 92.3% conversion rate of triglycerides into esters by alkaline transesterification. Properties of the BPL oil-based biodiesel are within the specifications of ASTM D6751, suggesting that the solid organic waste-grown BPL could be a feasible non-food feedstock for biodiesel production.     

Production of algae-based biodiesel using the continuous catalytic Mcgyan® process

This study demonstrates the production of algal biodiesel from Dunaliella tertiolecta, Nannochloropsis oculata, wild freshwater microalgae, and macroalgae lipids using a highly efficient continuous catalytic process. The heterogeneous catalytic process uses supercritical methanol and porous titania microspheres in a fixed bed reactor to catalyze the simultaneous transesterification and esterification of triacylglycerides and free fatty acids, respectively, to fatty acid methyl esters (biodiesel). Triacylglycerides and free fatty acids were converted to alkyl esters with up to 85% efficiency as measured by 300 MHz ¹H NMR spectroscopy. The lipid composition of the different algae was studied gravimetrically and by gas chromatography. The analysis showed that even though total lipids comprised upwards of 19% of algal dry weight the saponifiable lipids, and resulting biodiesel, comprised only 1% of dry weight. Thus highlighting the need to determine the triacylglyceride and free fatty acid content when considering microalgae for biodiesel production.     

Silica-bonded N-propyl sulfamic acid used as a heterogeneous catalyst for transesterification of soybean oil with methanol

The transesterification of soybean oil with methanol was carried out, to produce biodiesel, over silica-bonded N-propyl sulfamic acid in a heterogeneous manner. Results showed that a maximum conversion of 90.5% was achieved using a 1:20 M ratio of soybean oil to methanol and a catalyst amount of 7.5 wt.% at 423 K for 60 h. It was found that the free fatty acid (FFA) and water present in the feedstock had no significant influence on the catalytic activity to the transesterification reaction. Besides, the catalyst also showed activities towards the esterification reaction of FFAs, in terms of the FFA conversion of 95.6% at 423 K for 30 h. Furthermore, the catalyst could be recovered with a better reusability.     

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 preparation from microalgae lipid by two-step lipase catalysis

To overcome the high energy-consuming process of microalgae drying, a two-step lipase catalysis technique for the preparation of biodiesel from microalgae lipid of Chlorella spp. was developed. In the first step, free fatty acids (FAAs) and triacylglycerols (TAGs) are released after cell disruption and extracted, while the TAGs were hydrolysed by free lipase in aqueous phase. In the second step, FAAs were esterified with ethanol in the catalysis of free suspended lipase. The maximum rate of hydrolysis and esterification was 93.6% and 91.3%, respectively. The effects of reaction parameters, such as reaction time, enzyme amount, water content and molar ratio of lipid to ethanol on hydrolysis or esterification, were investigated. The results indicated that two-step reaction process (hydrolyse esterify) for biodiesel production were feasible.     

Mechanism study on NS81006-mediated methanolysis of triglyceride in oil/water biphasic system for biodiesel production

Compared to immobilized lipase, soluble lipase has the merits of lower cost and faster reaction rate, thus much attention has been paid to soluble lipase-mediated methanolysis for biodiesel (fatty acid methyl ester, FAME) production in recent years. Our previous study showed that soluble lipase NS81006 could effectively catalyze the methanolysis of soybean oil (triglyceride, TG) for FAME preparation in oil/water biphasic system. Study on the related mechanism of soluble lipase NS81006-mediated methanolysis of TG was carried out in this paper. Based on the analysis of substances change in the reaction process, mechanism model was hypothesized and the model parameters were simulated by Matlab. The simulated model was validated further. The results showed that in the reaction process of soluble lipase NS81006-mediated methanolysis of TG in oil/water biphasic system, TG proceeded three-step hydrolysis to generate FFA (free fatty acid), and then FFA transformed into FAME by esterification with methanol. During the whole process, FFA is mainly generated through the hydrolysis of TG and intermediate DG (diglyceride), while the hydrolysis of FAME could be ignored.     

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.     

Study on acyl migration in immobilized lipozyme TL-catalyzed transesterification of soybean oil for biodiesel production

During enzymatic transesterification of soybean oils with methanol for biodiesel production, it was supposed that the maximum biodiesel yield was only 66% since lipozyme TL was a typical lipase with a strict 1,3-positional specificity. However, it has been observed that over 90% biodiesel yield could be obtained. It was therefore assumed, and subsequently demonstrated, that acyl migration occurred during the reaction process. Different factors which may influence the acyl migration were explored further and it has been found that the silica gel acting as the immobilized material contributes significantly to the promotion of acyl migration in the transesterification process. The final biodiesel yield was only 66% when 4% lipozyme TL used, while about 90% biodiesel yield could be achieved when combining 6% silica gel with 4% lipozyme TL, almost as high as that of 10% immobilized lipase used for the reaction.     

Study of lipase immobilization on zeolitic support and transesterification reaction in a solvent free-system

In order to understand the role of the acid–base, electrostatic and covalent interactions between enzyme and support, the catalytic behavior of the Rhizomucor miehei lipase (RML) immobilized on zeolite materials has been studied. The highest lipase activities were obtained when this enzyme, immobilized by adsorption, interacts through acid–base binding forces with the support surface, resulting in activation of the enzyme catalytic center. Due to the interest in biodiesel production by mild enzymatic transesterification, this heterogeneous biocatalyst has been used in transesterification of fatty acids contained in olive oil. The results show a high oleic acid conversion for several reaction cycles with a higher total biodiesel productivity compared to that using the free enzyme.     

An effective acid catalyst for biodiesel production from impure raw feedstocks

Biodiesel consists of fatty acids short chain alkyl esters produced through transesterification and esterification of fats and oils. Production of biodiesel is strongly affected by the purity of raw lipids, and catalysts play important role in these processes. Although direct utilization of impure feedstocks is more economical, their use necessitates development of effective catalysts to overcome hindering influences of impurities. In this study, sulfuryl chloride, thionyl chloride, acetyl chloride, p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, dimethylsulfate and sulfuric acid were investigated as catalysts for the production of biodiesel because acids have higher tolerance to water and free fatty acids in oils and can simultaneously catalyze both the esterification and transesterification reactions. Sulfuryl chloride was found to be an effective catalyst for production of biodiesel from soybean oil, its waste oil and microalgal lipids.     

Biocatalytic methanolysis activities of cross-linked protein-coated microcrystalline lipase toward esterification/transesterification of relevant palm products

Biocatalysis by immobilized lipase is an efficient alternative process for conversion of crude vegetable oil with high free fatty acid content to biodiesel, which is the limit of the conventional alkaline-catalyzed reaction. In this study, influences of solid-state organic and inorganic buffer core matrices with different pK_a on catalytic performance of cross-linked protein coated microcrystalline biocatalysts prepared from Thermomyces lanuginosus lipase (CL-PCMC-LIP) toward esterification of palmitic acid (PA), transesterification of refined palm oil (RPO), and co-ester/transesterification of crude palm oil (CPO) to fatty acid methyl ester (FAME) was studied. Glycine, CAPSO (3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid), and TAPS ([(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)amino]-1-propanesulfonic acid) were shown to be potent core matrices for these reactions. The optimal reaction contained 4:1 [methanol]/[fatty acid] molar equivalence ratio with 20% (w/w) CL-PCMC-LIP on glycine in the presence of tert-butanol as a co-solvent. Deactivation effect of glycerol on the biocatalyst reactive surface was shown by FTIR, which could be alleviated by increasing co-solvent content. The maximal FAME yields from PA, RPO, and CPO reached 97.6, 94.9, and 95.5%, respectively on a molar basis under the optimum conditions after incubation at 50 °C for 6 h. The biocatalyst retained >80% activity after recycling in five consecutive batches. The work demonstrates the potential of CL-PCMC-LIP on one-step conversion of inexpensive crude fatty acid-rich feedstock to biodiesel.     

A two steps enzymatic procedure to obtain sterol esters,tocopherols and fatty acid ethyl esters from soybean oil deodorizer distillate

Soybean oil deodorizer distillate (SODD) was enzymatically modified to obtain a product mixture comprised mainly of sterol esters, tocopherols, and fatty acid ethyl esters. Firstly, the original SODD was mixed with oleic acid to reduce its melting point from 65–70 to 30–35 °C and also to produce a reaction mixture with a ratio of free fatty acids (FFA) to sterols close to 2 to improve the progress of sterols esterification. Two enzymatic steps were used in order to separate sterols esterification and ethyl esterification in time and space. The first enzymatic step (in the presence of Candida rugosa lipase) allowed to efficiently transform more than 90% of the original sterols in a short period of time (5 h). The second enzymatic step (in the presence of Novozym 435) converted more than 95% of the FFA in less than 3 h. In addition, the stability of both biocatalysts has been evaluated and both bioprocesses have been scaled-up reutilizing the same batch of lipase up to 8 and 3 times for the first and the second enzymatic step, respectively. The final product obtained is intended to be used as starting material for the purification of sterol esters, tocopherols, and fatty acid ethyl esters via supercritical fluid extraction.     

Homogeneous,heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: A review

In the last few years, biodiesel has emerged as one of the most potential renewable energy to replace current petrol-derived diesel. It is a renewable, biodegradable and non-toxic fuel which can be easily produced through transesterification reaction. However, current commercial usage of refined vegetable oils for biodiesel production is impractical and uneconomical due to high feedstock cost and priority as food resources. Low-grade oil, typically waste cooking oil can be a better alternative; however, the high free fatty acids (FFA) content in waste cooking oil has become the main drawback for this potential feedstock. Therefore, this review paper is aimed to give an overview on the current status of biodiesel production and the potential of waste cooking oil as an alternative feedstock. Advantages and limitations of using homogeneous, heterogeneous and enzymatic transesterification on oil with high FFA (mostly waste cooking oil) are discussed in detail. It was found that using heterogeneous acid catalyst and enzyme are the best option to produce biodiesel from oil with high FFA as compared to the current commercial homogeneous base-catalyzed process. However, these heterogeneous acid and enzyme catalyze system still suffers from serious mass transfer limitation problems and therefore are not favorable for industrial application. Nevertheless, towards the end of this review paper, a few latest technological developments that have the potential to overcome the mass transfer limitation problem such as oscillatory flow reactor (OFR), ultrasonication, microwave reactor and co-solvent are reviewed. With proper research focus and development, waste cooking oil can indeed become the next ideal feedstock for biodiesel.