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.     

Integrated biodiesel production: a comparison of different homogeneous catalysts systems

The most common catalysts for biodiesel production are homogeneous basic catalysts. In the present paper, a comparison is made of different basic catalysts (sodium methoxide, potassium methoxide, sodium hydroxide and potassium hydroxide) for methanolysis of sunflower oil. All the reactions were carried out under the same experimental conditions in a batch stirred reactor and the subsequent separation and purification stages in a decanter. The analytical methods included gas chromatography and the determination of fat and oil conventional parameters. The biodiesel purity was near 100 wt.% for all catalysts. However, near 100 wt.% biodiesel yields were only obtained with the methoxide catalysts. According to the material balance of the process, yield losses were due to triglyceride saponification and methyl ester dissolution in glycerol. Obtained biodiesel met the measured specifications, except for the iodine value, according to the German and EU draft standards. Although all the transesterification reactions were quite rapid and the biodiesel layers achieved nearly 100% methyl ester concentrations, the reactions using sodium hydroxide turned out the fastest.     

A glycerol-free process to produce biodiesel by supercritical methyl acetate technology: An optimization study via Response Surface Methodology

In this study, fatty acid methyl esters (FAME) have been successfully produced from transesterification reaction between triglycerides and methyl acetate, instead of alcohol. In this non-catalytic supercritical methyl acetate (SCMA) technology, triacetin which is a valuable biodiesel additive is produced as side product rather than glycerol, which has lower commercial value. Besides, the properties of the biodiesel (FAME and triacetin) were found to be superior compared to those produced from conventional catalytic reactions (FAME only). In this study, the effects of various important parameters on the yield of biodiesel were optimized by utilizing Response Surface Methodology (RSM) analysis. The mathematical model developed was found to be adequate and statistically accurate to predict the optimum yield of biodiesel. The optimum conditions were found to be 399 °C for reaction temperature, 30 mol/mol of methyl acetate to oil molar ratio and reaction time of 59 min to achieve 97.6% biodiesel yield.     

高含游离脂肪酸的香果树籽油制备生物柴油的方法

目前生物柴油因其环保和可再生利用资源的特性备受关注。多数生物柴油是通过甲醇和碱催化食用油得到的,而大量非食用油也可以制备生物柴油。本文报道用高含游离酸脂肪油快速高效低成本制备成其单酯的二步法工艺。先用1% H2SO4以少于1.5%量对甲醇和云南特产香果树（Lindera communis）籽的粗原料油以10∶1摩尔比组成的混合液酸催化酯化游离脂肪酸;之后再对醇和得到的油脂产品按摩尔比15∶1的混合液碱催化转化为单甲酯和甘油。本方法是一个直接甲脂化制备生物柴油的工艺简洁、降低成本的新技术。文中还讨论了该工艺影响转化效率的主要因素,如摩尔比,催化量,温度,反应时间和酸度。香果树生物柴油不重蒸,而其生物柴油的主要特性,如粘度、热值、比重、闪点、冷滤点等与生物柴油标准的匹配度,也做了报道,研究结果将为香果树生物柴油以非重蒸油料制备生物柴油产品,作为潜在的柴油燃料替代产品提供技术支撑。     

A novel enzymatic route for biodiesel production from renewable oils in a solvent-free medium

A new enzymatic route for biodiesel production from soybean oil was developed using methyl acetate as a novel acyl acceptor. Novozym 435 (immobilized Candida antarctica lipase) gave the highest methyl ester (ME) yield of 92%. The optimum conditions of the transesterification were 30% enzyme based on oil weight; a molar ratio of methyl acetate/oil of 12:1; temperature 40 °C and reaction time 10 h. Since no glycerol was produced in the process, this method is very convenient for recycling the catalyst and by-product triacetylglycerol showed no negative effect on the fuel property.     

Optimisation of integrated biodiesel production. Part II: a study of the material balance

A study was made of the material balance for the fatty acid methyl ester (biodiesel) synthesis from sunflower oil using potassium hydroxide as the catalyst. A factorial design of experiments and a central composite design have been used to evaluate the influence of operating conditions on the process material balance. The responses chosen were the biodiesel yield and the yield losses due to triglyceride saponification and methyl ester dissolution in glycerol, while the variables studied were temperature, initial catalyst concentration and the methanol:vegetable oil molar ratio. The biodiesel yield increased and therefore the yield losses decreased by decreasing catalyst concentration and temperature. However, the methanol:sunflower oil molar ratio did not affect the material balance variables significantly. Second-order models were obtained to predict the biodiesel yield and both yield losses. Within the experimental range studied, these models largely matched the results from the experiments.     

The effect of the acidity of rapeseed oil on its transesterification

The aim of this work is to study the transesterification of vegetable oil with a high acid number at unchanged reaction conditions. Rapeseed oil was used as the raw material and its acid number was changed by the addition of oleic acid (from 0.89 to 12.25 mg KOH/g). Methanol was used for transesterification (molar ratio of oil to methanol 1:6) and potassium hydroxide was used as a catalyst. After the reaction time, the residue of the catalyst was neutralised by gaseous carbon dioxide and the methanol excess was removed. After the separation of two phases, each of them was analyzed (in the ester phase: yield, content of methyl ester and acid number; in the glycerol phase: yield, density, viscosity, content of glycerol, soaps, methyl ester, potassium carbonate and hydrogen carbonate). The obtained data was compared with theoretical material balances and the effect on the saponification of oil was discussed. The results show that the yield of methyl ester (biodiesel) is significantly affected by a higher acid number, as well as enhanced soap formation. On the other hand, the conversion of the oil and acid number of the ester phase remain at constant values in studied borders.     

A process model to estimate biodiesel production costs

'Biodiesel' is the name given to a renewable diesel fuel that is produced from fats and oils. It consists of the simple alkyl esters of fatty acids, most typically the methyl esters. We have developed a computer model to estimate the capital and operating costs of a moderately-sized industrial biodiesel production facility. The major process operations in the plant were continuous-process vegetable oil transesterification, and ester and glycerol recovery. The model was designed using contemporary process simulation software, and current reagent, equipment and supply costs, following current production practices. Crude, degummed soybean oil was specified as the feedstock. Annual production capacity of the plant was set at 37,854,118 l (10 x 10(6)gal). Facility construction costs were calculated to be US dollar 11.3 million. The largest contributors to the equipment cost, accounting for nearly one third of expenditures, were storage tanks to contain a 25 day capacity of feedstock and product. At a value of US dollar 0.52/kg (dollar 0.236/lb) for feedstock soybean oil, a biodiesel production cost of US dollar 0.53/l (dollar 2.00/gal) was predicted. The single greatest contributor to this value was the cost of the oil feedstock, which accounted for 88% of total estimated production costs. An analysis of the dependence of production costs on the cost of the feedstock indicated a direct linear relationship between the two, with a change of US dollar 0.020/l (dollar 0.075/gal) in product cost per US dollar 0.022/kg (dollar 0.01/lb) change in oil cost. Process economics included the recovery of coproduct glycerol generated during biodiesel production, and its sale into the commercial glycerol market as an 80% w/w aqueous solution, which reduced production costs by approximately 6%. The production cost of biodiesel was found to vary inversely and linearly with variations in the market value of glycerol, increasing by US dollar 0.0022/l (dollar 0.0085/gal) for every US dollar 0.022/kg (dollar 0.01/lb) reduction in glycerol value. The model is flexible in that it can be modified to calculate the effects on capital and production costs of changes in feedstock cost, changes in the type of feedstock employed, changes in the value of the glycerol coproduct, and changes in process chemistry and technology.     

Effect of water on lipase NS81006-catalyzed alcoholysis for biodiesel production

Biodiesel production catalyzed by free lipase has been drawing attention for its lower cost and faster reaction rate compared to immobilized lipase. It has been found that free lipase NS81006 could efficiently catalyze alkyl esters production and a certain amount of water is demonstrated to be necessary for the catalytic process. The effect of water content on liquid lipase NS81006-mediated methanolysis and ethanolysis for biodiesel production was first explored respectively in this paper. It was found that with water content ranging from 3% to 10% (based on oil weight), there was no significant difference in the final alkyl ester yield either in NS81006-mediated methanolysis or ethanolysis process, while the quality of biodiesel varied obviously. The acid value as well as the contents of monoglyceride and diglyceride were much lower in the lower water-containing system. With the water content decreasing from 10% to 3%, the acid value reduced from 8.24 to 4.89 mg KOH/g oil, and the content of MAG and DAG dropped to 0.31 and 0.22, from 0.62 and 0.74, respectively. Lipase could maintain rather good stability with proper alcohol adding strategy and the gradual reduction in biodiesel yield in the repeated uses resulted from the accumulation of by-product glycerol. The continuous running of lipase-mediated methanolysis of waste cooking oil was successfully realized at 30L reactor and a final methyl ester yield of over 90% could be obtained.     

Process engineering and optimization of glycerol separation in a packed-bed reactor for enzymatic biodiesel production

A process model for efficient glycerol separation during methanolysis in an enzymatic packed-bed reactor (PBR) was developed. A theoretical glycerol removal efficiency from the reaction mixture containing over 30% methyl esters was achieved at a high flow rate of 540 ml/h. To facilitate a stable operation of the PBR system, a batch reaction prior to continuous methanolysis was conducted using oils with different acid values and immobilized lipases pretreated with methyl esters. The reaction system successfully attained the methyl ester content of over 30% along with reduced viscosity and water content. Furthermore, to obtain a high methyl ester content above 96% continuously, long-term lipase stability was confirmed by operating a bench-scale PBR system for 550 h, in which the intermediates containing methyl esters and residual glycerides were fed into the enzyme-packed columns connected in series. Therefore, the developed process model is considered useful for industrial biodiesel production.     

Conversion of Soybean Oil to Biodiesel Fuel Using Lipozyme TL IM in a Solvent-free Medium

The conversion of soybean oil to biodiesel fuel was investigated in the presence of a lipase from Thermomyces lanuginosus (commercially called Lipozyme TL IM) in a solvent-free medium. The lipase was inactivated when more than 1.5 molar equivalent of methanol was added to the oil mixture. To fully convert the oil to its corresponding methyl esters, the reaction was performed successfully by a three-step addition of 1 molar equivalent of methanol and under the optimized conditions (40°C, 150 rpm, 10% enzyme quantity based on oil weight), the maximum methyl ester (ME) yield was 98% after 12 h reaction. By-product glycerol had a negative effect on enzymatic activity and iso-propanol was found to be effective for glycerol removal, in the presence of which lipase expressed relatively high activity and more than 94% of the ME yield was maintained after being used repeatedly for 15 batches.     

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.     

Conversion of Soybean Oil to Biodiesel Fuel Using Lipozyme TL IM in a Solvent-free Medium

The conversion of soybean oil to biodiesel fuel was investigated in the presence of a lipase from Thermomyces lanuginosus (commercially called Lipozyme TL IM) in a solvent-free medium. The lipase was inactivated when more than 1.5 molar equivalent of methanol was added to the oil mixture. To fully convert the oil to its corresponding methyl esters, the reaction was performed successfully by a three-step addition of 1 molar equivalent of methanol and under the optimized conditions (40°C, 150 rpm, 10% enzyme quantity based on oil weight), the maximum methyl ester (ME) yield was 98% after 12 h reaction. By-product glycerol had a negative effect on enzymatic activity and iso-propanol was found to be effective for glycerol removal, in the presence of which lipase expressed relatively high activity and more than 94% of the ME yield was maintained after being used repeatedly for 15 batches.     

Utilization of glycerol and crude glycerol for polysaccharide production by an endophytic fungus Chaetomium globosum CGMCC 6882

Abstract

Crude glycerol is becoming a financial and environmental liability due to its surplus production from biodiesel industry, and its utilization as a fermentation feedstock for value-added chemicals production has been widely studied. In present work, the capacity of an endophytic fungus, Chaetomium globosum CGMCC 6882, using glycerol and crude glycerol for polysaccharide production was investigated. Results showed that the polysaccharide titers from glucose and glycerol were 1.85 and 3.8?g/L, respectively. Moreover, spore morphology of C. globosum CGMCC 6882 was favorable for polysaccharide production. Meanwhile, impurities in crude glycerol have no effect on polysaccharide production by C. globosum CGMCC 6882. Finally, characteristic results of polysaccharides produced from glucose, glycerol, and crude glycerol have suggested that metabolic flux might be a determinant factor on polysaccharide structure. Taken together, this research provided an innovative approach of utilizing crude glycerol produced from the biodiesel production process.     

Ultrasonic monitoring of glycerol settling during transesterification of soybean oil

A low-intensity ultrasonic measurement system was used to monitor the products of transesterification of soybean oil in methanol to FAME (biodiesel). The byproducts of the transesterification reaction are methyl esters, glycerol and other products. During the transesterification reaction, the glycerol, having a higher density than the methyl ester, settles at the bottom of the reaction vessel. The aim of this study was to measure the glycerol deposition rate during transesterification and to assess the reaction rate and end time. Soybean oil was converted into biodiesel at four temperature levels. The amount of catalyst (KOH) used in the transesterification reactions was determined by titration. The ultrasonic waveforms captured during the reaction were recorded and analyzed automatically. The ultrasonic system monitored the effects of reaction temperatures on the glycerol settling rate and the reaction end times. The ultrasonic measurement of glycerol settling would be a useful non-destructive method for evaluating the effects of parameters such as catalyst amount, mixing time and temperature on transesterification reactions.     

Lipase-catalyzed biodiesel production with methyl acetate as acyl acceptor

Biodiesel is an alternative diesel fuel made from renewable biological resources. During the process of biodiesel production, lipase-catalyzed transesterification is a crucial step. However, current techniques using methanol as acyl acceptor have lower enzymatic activity; this limits the application of such techniques in large-scale biodiesel production. Furthermore, the lipid feedstock of currently available techniques is limited. In this paper, the technique of lipase-catalyzed transesterification of five different oils for biodiesel production with methyl acetate as acyl acceptor was investigated, and the transesterification reaction conditions were optimized. The operation stability of lipase under the obtained optimal conditions was further examined. The results showed that under optimal transesterification conditions, both plant oils and animal fats led to high yields of methyl ester: cotton-seed oil, 98%; rapeseed oil, 95%; soybean oil, 91%; tea-seed oil, 92%; and lard, 95%. Crude and refined cottonseed oil or lard made no significant difference in yields of methyl ester. No loss of enzymatic activity was detected for lipase after being repeatedly used for 40 cycles (ca. 800 h), which indicates that the operational stability of lipase was fairly good under these conditions. Our results suggest that cotton-seed oil, rape-seed oil and lard might substitute soybean oil as suitable lipid feedstock for biodiesel production. Our results also show that our technique is fit for various lipid feedstocks both from plants and animals, and presents a very promising way for the large-scale biodiesel production.     

Coffee oil as a potential feedstock for biodiesel production

A preliminary evaluation of the feasibility of producing biodiesel using oil extracted from defective coffee beans was conducted as an alternative means of utilizing these beans instead of roasting for consumption of beverage with depreciated quality. Direct transesterifications of triglycerides from refined soybean oil (reference) and from oils extracted from healthy and defective coffee beans were performed. Type of alcohol employed and time were the reaction parameters studied. Sodium methoxide was used as alkaline catalyst. There was optimal phase separation after reactions using both soybean and healthy coffee beans oils when methanol was used. This was not observed when using the oil from defective beans which required further processing to obtain purified alkyl esters. Nevertheless, coffee oil was demonstrated to be a potential feedstock for biodiesel production, both from healthy and defective beans, since the corresponding oils were successfully converted to fatty acid methyl and ethyl esters.     

Enzymatic coproduction of biodiesel and glycerol carbonate from soybean oil and dimethyl carbonate

The enzymatic coproduction of biodiesel and glycerol carbonate by the transesterification of soybean oil was studied using lipase as catalyst in organic solvent. To produce biodiesel and glycerol carbonate simultaneously, experiments were designed sequentially. Enzyme screening, the molar ratio of dimethyl carbonate (DMC) to soybean oil, reaction temperature and solvent effects were investigated. The results of enzyme screening, at 100 g/L Novozym 435 (immobilized Candida antarctica lipase B), biodiesel and glycerol carbonate showed conversions of 58.7% and 50.7%, respectively. The optimal conditions were 60 °C, 100 g/L Novozym 435, 6.0:1 molar ratio with tert-butanol as solvent: 84.9% biodiesel and 92.0% glycerol carbonate production was achieved.     

Consolidating biofuel platforms through the fermentative bioconversion of crude glycerol to butanol

Economic realities for the rising industrial biofuel production have changed substantially during the low oil price period starting in the mid 2010’s. Increased competition requires the sector to increase productivity through the reduction of low-value by-products and full utilization of all value and energy stored in their respective feedstock. Biodiesel is produced commercially from substrates such as animal fat and vegetable oil, generating approximately 10 wt% crude glycerol as its main, currently underutilized, by-product. This crude glycerol is contaminated with catalyst, soap, free fatty acids, glycerides and methyl esters; hence only a small fraction enters the existing glycerol markets, while the purification costs for the majority of crude glycerol are simply too high. However, this presents a unique opportunity to generate additional value. One technical possibility is to use crude glycerol as a carbon source for butanol production, a compound of higher value and energy, a potential additive for gasoline and diesel fuels and bulk chemical commodity. Conversion facilities could be co-located with biodiesel plants, utilizing established infrastructure and adding significant value and productivity to the existing biodiesel industry. This review focuses on the current activities geared towards the bioconversion of crude glycerol to butanol.     

Biodiesel production by two-stage transesterification with ethanol

A two-stage process consisting of two reactions steps with glycerin separation and ethanol/catalyst addition in each of them was optimized for ethyl esters production. The optimal reaction temperature was 55 °C. At an ethanol/oil molar ratio of 4.25:1 (25%v/v alcohol with respect to oil), a 99% conversion value was obtained with low ethanol consumption. In contrast to methoxide catalysts, sodium and potassium hydroxide catalysts severely complicate the purification since no phase separation took place under most conditions. With a total sodium methoxide concentration of 1.06 g catalyst/100 g oil, and adding 50% of the catalyst in each reaction step, biodiesel with a total glycerin content of 0.172% was obtained. The optimal conditions found in this study make it possible to use the same industrial facility to produce either methyl or ethyl esters.