Showing papers on "Transesterification published in 2005"

Synthesis of Biodiesel via Acid Catalysis

Abstract: Biodiesel is synthesized via the transesterification of lipid feedstocks with low molecular weight alcohols. Currently, alkaline bases are used to catalyze the reaction. These catalysts require anhydrous conditions and feedstocks with low levels of free fatty acids (FFAs). Inexpensive feedstocks containing high levels of FFAs cannot be directly used with the base catalysts currently employed. Strong liquid acid catalysts are less sensitive to FFAs and can simultaneously conduct esterification and transesterification. However, they are slower and necessitate higher reaction temperatures. Nonetheless, acid-catalyzed processes could produce biodiesel from low-cost feedstocks, lowering production costs. Better yet, if solid acid catalysts could replace liquid acids, the corrosion and environmental problems associated with them could be avoided and product purification protocols reduced, significantly simplifying biodiesel production and reducing cost. This article reviews some of the research related to biodi...

Transesterification of triacetin with methanol on solid acid and base catalysts

Abstract: Biodiesel is a particularly attractive renewable fuel as it can be used in existing engines, is environmentally friendly, and is readily synthesized from animal fats and vegetable oils. Heterogeneous catalysts offer exciting possibilities for improving the economics of biodiesel synthesis; however, few published investigations have addressed the use of such catalysts to date. The purpose of this research was to investigate the kinetics and selectivities of different solid catalysts for the transesterification of triacetin (a model compound for larger triglycerides as found in vegetable oils and fats) with methanol. Reaction was carried out at 60 °C in a batch reactor with a variety of solid and liquid, acid and base catalysts. The homogeneous phase (i.e., liquid) catalysts (NaOH and H2SO4) were studied for comparison. Amberlyst-15, Nafion NR50, sulfated zirconia, and ETS-10 (Na, K) showed reasonable activities, suggesting that they could be suitable alternatives to liquid catalysts. While on a wt.% basis (of reaction mixture) the homogeneous phase catalysts gave higher rates of reaction, on a rate-per-site basis the solid acids were similar to H2SO4. Sulfated zirconia and tungstated zirconia had comparable turnover frequencies as H2SO4. The deactivation characteristics of some of these catalysts were also studied.

Structure-reactivity correlations in MgAl hydrotalcite catalysts for biodiesel synthesis

Abstract: A series of [Mg(1−x)Alx(OH)2]x+(CO3)x/n2− hydrotalcite materials with compositions over the range x = 0.25–0.55 have been synthesised using an alkali-free coprecipitation route. All materials exhibit XRD patterns characteristic of the hydrotalcite phase with a steady lattice expansion observed with increasing Mg content. XPS measurements reveal a decrease in both the Al and Mg photoelectron binding energies with Mg incorporation which correlates with the increased intra-layer electron density. All materials are effective catalysts for the liquid phase transesterification of glyceryl tributyrate with methanol for biodiesel production. The rate increases steadily with Mg content, with the Mg rich Mg2.93Al catalyst an order of magnitude more active than MgO, with pure Al2O3 being completely inert. The rate of reaction also correlates with intralayer electron density which can be associated with increased basicity.

Mahua oil (Madhuca Indica seed oil) methyl ester as biodiesel-preparation and emission characterstics

Abstract: There is an increasing interest in many countries to search for suitable alternative fuels that are environment friendly. Although straight vegetable oils can be used in diesel engines, their high viscosities, low volatilities and poor cold flow properties have led to the investigation of various derivatives. Biodiesel is a fatty acid alkyl ester, which can be derived from any vegetable oil by transesterification. Biodiesel is a renewable, biodegradable and non-toxic fuel. In this study, Mahua oil (Madhuca indica seed oil) was transesterified with methanol using sodium hydroxide as catalyst to obtain mahua oil methyl ester. This biodiesel was tested in a single cylinder, four stroke, direct injection, constant speed, compression ignition diesel engine (Kirloskar) to evaluate the performance and emissions.

Synthesis of biodiesel via homogeneous Lewis acid catalyst

Abstract: Nowadays, most biodiesel (fatty acids methyl esters, FAME) is produced by the transesterification of triglycerides (TG) of refined/edible type oils using methanol and an homogeneous alkaline catalyst However, production costs are still rather high compared with the ones of petroleum-based diesel fuel To lower costs and make biodiesel competitive less-expensive feedstocks such as waste fats or non-edible type oils could be used The use of homogeneous alkaline catalysts in the transesterification of such types of fats and oils poses great difficulties due to the presence of large amounts of free fatty acids (FFA) This paper studies the use of carboxylic salts as a possible alternative, because these catalysts are active also in the presence of high FFA concentrations The most active catalyst (Cd, Mn, Pb, Zn carboxylic salts) have been individuated and a correlation of the activities with the cation acidity has been found

Heterogeneously MgO-catalyzed transesterification for fine-chemical and biodiesel industrial production

Abstract: Abstract A heterogeneous magnesium oxide catalyst is a good alternative for homogeneous catalysts for the transesterification of alkyl esters for the production of fine-chemicals as well as for the production of biodiesel. The transesterification of ethyl acetate with methanol was used as a model reaction to simulate fine-chemical production in a batch slurry reactor at industrial conditions. The transesterification of triolein with methanol to methyl oleate was chosen to simulate continuous production of biodiesel from rapeseed oil. A kinetic model based on a three-step ‘Eley–Rideal’ type of mechanism in the liquid phase was used in both process simulations. The transesterification reaction occurs between methanol adsorbed on a magnesium oxide free basic site and ethyl acetate or the glyceride from the liquid phase. Methanol adsorption is assumed to be rate-determining in both processes. Activity coefficients were required to account for the significant non-ideality of the reaction mixture in the simulations of both processes. The simulations indicate that a production of 500 tonnes methyl acetate per year can be reached at ambient temperature in a batch reactor of 10 m 3 containing 5 kg of MgO catalyst, and that a continuous production of 100,000 tonnes of biodiesel per year can be achieved at 323 K in a continuous stirred reactor of 25 m 3 containing 5700 kg of MgO catalyst. Although various assumptions and simplifications were made in these explorative simulations the assumptions concerning the reaction kinetics used, the results indicate that for both processes a heterogeneous magnesium oxide catalyst shows promising potential as a viable industrial scale alternative.

Biodiesel from an alkaline transesterification reaction of soybean oil using ultrasonic mixing

Abstract: The feasibility of using ultrasonic mixing to obtain biodiesel from soybean oil was established. The alkaline transesterification reaction was studied at three levels of temperature and four alcohol-to-oil ratios. Excellent yields were obtained for all conditions. For example, at 40°C with ultrasonic agitation and a molar ratio of 6∶1 methanol/oil, the conversion to FAME was greater than 99.4% after about 15 min. For a 6∶1 methanol/oil ratio and a 25 to 60°C temperature range, a pseudo second-order kinetic model was confirmed for the hydrolysis of DG and TG. Reaction rate constants were three to five times higher than those reported in the literature for, mechanical agitation. We suspect that the observed mass transfer and kinetic rate enhancements were due to the increase in interfacial area and activity of the microscopic and macroscopic bubbles formed when ultrasonic waves of 20 kHz were applied to a two-phase reaction system.

Selective transesterification of triolein with methanol to methyl oleate and glycerol using alumina loaded with alkali metal salt as a solid-base catalyst

Abstract: Selective transesterification of triolein (trioleoyl glycerol) with methanol to methyl oleate and glycerol could be achieved at around 333 K using alumina loaded with alkali metal salt as a solid-base catalyst. The catalytic activities are shown to be relatively insensitive to the presence of water. A K 2 CO 3 -loaded alumina catalyst prepared by evacuation at 823 K gives methyl oleate and glycerol in the highest yields of 94 and 89%, respectively, at 333 K in 1 h. This catalyst also effectively catalyzes the glycerolysis of triolein with glycerol to give dioleoyl glycerol in 71% yield at 453 K in 5 h.

Lipase-catalyzed production of biodiesel from rice bran oil

Abstract: Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the raw material. Use of an inexpensive raw material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (<68%). A two-step lipase-catalyzed methanolysis of rice bran oil was developed for the efficient conversion of both free fatty acid and acylglycerides into fatty acid methyl ester. More than 98% conversion can be obtained in 4–6 h depending on the relative proportion of free fatty acid and acylglycerides in the rice bran oil. Inactivation of lipase by phospholipids and other minor components was observed during the methanolysis of crude rice bran oil. Simultaneous dewaxing/degumming proved to be efficient in removing phospholipids and other minor components that inhibit lipase activity from crude rice bran oil. Copyright © 2005 Society of Chemical Industry

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

Abstract: 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.

Oxidative stability of biodiesel from soybean oil fatty acid ethyl esters

Abstract: Biodiesel consists of long-chain fatty acid esters, derived from renewable sources such as vegetable oils, and its utilization is associated to the substitution of the diesel oil in engines. Depending on the raw material, biodiesel can contain more or less unsaturated fatty acids in its composition, which are susceptible to oxidation reactions accelerated by exposition to oxygen and high temperatures, being able to change into polymerized compounds. The objective of this work was to determine the oxidative stability of biodiesel produced by ethanolysis of neutralized, refined, soybean frying oil waste, and partially hydrogenated soybean frying oil waste. The evaluation was conducted by means of the Rancimat® equipment, at temperatures of 100 and 105oC, with an air flow of 20 L h-1. The fatty acid composition was determined by GC and the iodine value was calculated. It was observed that even though the neutralized, refined and waste frying soybean oils presented close comparable iodine values, biodiesel presented different oxidative stabilities. The biodiesel from neutralized soybean oil presented greater stability, followed by the refined and the frying waste. Due to the natural antioxidants in its composition, the neutralized soybean oil promoted a larger oxidative stability of the produced biodiesel. During the deodorization process, the vegetable oils lose part of these antioxidants, therefore the biodiesel from refined soybean oil presented a reduced stability. The thermal process degrades the antioxidants, thus the biodiesel from frying waste oil resulted in lower stability, the same occuring with the biodiesel from partially hydrogenated waste oil, even though having lower iodine values than the other.

Methods for producing biodiesel

Abstract: Transesterification, esterification, and esterification-transesterification (both one-step and two-step) for producing biofuels The process may be enhanced by one or more of the following: 1) applying microwave or RF energy; 2) passing reactants over a heterogeneous catalyst at sufficiently high velocity to achieve high shear conditions; 3) emulsifying reactants with a homogeneous catalyst; or 4) maintaining the reaction at a pressure at or above autogeneous pressure Enhanced processes using one or more of these steps can result in higher process rates, higher conversion levels, or both

New multi-phase catalytic systems based on tin compounds active for vegetable oil transesterificaton reaction

Abstract: It is reported here about some attempts in order to develop a multi-phase catalytic system active for vegetable oil alcoholysis based upon tin compounds. The immobilization of Sn(3-hydroxy-2-methyl-4-pyrone) 2 (H 2 O) 2 by dissolving it in the 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and supporting it in an ion-exchange resin, as well as the catalytic behavior of tin oxide was studied. By anchoring the tin complex in the ionic liquid, it was observed that its catalytic activity was maintained but it was not possible to reuse the catalytic system due to leaching of the catalyst from the ionic phase during each reaction. On the other hand, it was found that the tin complex lost its catalytic activity when supported in the organic resin. It was also shown that tin oxide was active for soybean oil methanolysis (conversion yields up to 93% in 3 h were achieved) and was also possible to recycle it without any loss in its catalytic activity.

Interaction mechanisms of natural ester dielectric fluid and Kraft paper

Abstract: Sealed tube accelerated aging studies demonstrate a slower aging rate for cellulose insulation in natural (vegetable oil) ester dielectric fluid compared to the rate in conventional transformer oil. The interactions of natural ester fluid and cellulose insulation resulting in increased paper life are described by two interrelated chemical reaction mechanisms. Compared to the conventional transformer oil/Kraft paper system, the natural ester fluid's greater affinity for water shifts more water from the paper into the fluid in order to maintain equilibrium. The natural ester fluid reacts via the primary mechanism of hydrolysis to consume dissolved water in the fluid, shifting further the paper/fluid equilibrium to further dry the paper and produce free fatty acids. These fatty acids serve as reactants in the secondary mechanism of transesterification to modify the cellulose structure. The change in cellulose structure is verified using infrared analysis.

Production of biodiesel by lipase-catalyzed transesterification of vegetable oils: a kinetics study.

Abstract: Kinetics of production of biodiesel by enzymatic methanolysis of vegetable oils using lipase has been investigated. A mathematical model taking into account the mechanism of the methanolysis reaction starting from the vegetable oil as substrate, rather than the free fatty acids, has been developed. The kinetic parameters were estimated by fitting the experimental data of the enzymatic reaction of sunflower oil by two types of lipases, namely, Rhizomucor miehei lipase (RM) immobilized on ion-exchange resins and Thermomyces lanuginosa lipase (TL) immobilized on silica gel. There was a good agreement between the experimental results of the initial rate of reaction and those predicted by the proposed model equations, for both enzymes. From the proposed model equations, the regions where the effect of alcohol inhibition fades, at different substrate concentrations, were identified. The proposed model equation can be used to predict the rate of methanolysis of vegetable oils in a batch or a continuous reactor and to determine the optimal conditions for biodiesel production.

Biodiesel production from vegetable oils by supercritical methanol

Abstract: Transesterification of vegetable oils in supercritical methanol are carried out without using any catalyst. Methyl esters of vegetable oils or biodiesels have several outstanding advantages among other new-renewable and clean engine fuel alternatives and can be used in any diesel engine without modification. The most important variables affecting the methyl ester yield during the transesterification reaction are molar ratio of alcohol to vegetable oil and reaction temperature. Compared to no. 2 Diesel fuel, all vegetable oils are more viscous, while the methyl esters of vegetable oils are slightly more viscous. Biodiesel has become more attractive because of its environmental benefits. The cost of biodiesel, however, is the main obstacle to commercialization. With cooking oils as raw material, viability of a continuous transesterification process and recovery of high quality glycerol as a biodiesel by-product are primary options to be considered to lower the cost of biodiesel. Supercritical methanol has a high potential for both transesterification of triglycerides and methyl esterification of free fatty acids to methyl esters for diesel fuel substitute. In supercritical methanol transesterification method, yield of conversion rises 95% in 10 min. Viscosity of vegetable oils (27.2-53.6 mm 2 /s) get reduced in vegetable oil methyl esters (3.59-4.63 mm 2 /s). The flash point values of vegetable oil methyl esters are highly lower than those of vegetable oils. An increase in density from 860 to 885 kg/m 3 for vegetable oil methyl esters increases the viscosity from 3.59 to 4.63 mm 2 /s.