Subsequent Transesterification Research Articles

Comparative Study of the Physicochemical Characterization of Some Oils as Potential Feedstock for Biodiesel Production

Physicochemical properties of Cucurbita pepo, Brachystegia eurycoma, Cucumis melo, Luffa cylindrica, and Arachis hypogaea oils were studied to determine their potential as viable feedstock for biodiesel production. The nonedible oils were extracted by solvent extraction using n-hexane while the oil of Arachis hypogaea was procured. All the oils were characterized for specific gravity, pH, ash content, iodine value, acid value, saponification value, peroxide value, free fatty acid, flash point, kinematic viscosity, and refractive indices using standard methods. Cucurbita pepo seeds had very high oil content when compared to the others. Specific gravity and flash point of the oils were satisfactory. However, moisture content of some of the oils exceeded the stipulated ASTM standard for biodiesel production. Again, acid values of the nonedible oils were very high and exceeded the ASTM standard. They also exceeded the acid value of Arachis hypogaea oil except for Luffa cylindrica oil. Results indicate that the oils are potential biodiesel feedstocks. However, overall results indicate that the nonedible oils are not suitable for single-stage transesterification process to biodiesel but would be better suited for the two stage esterification and subsequent transesterification in order to obtain reasonable yields of the methyl esters.

Isolation and optimisation of the oleaginous yeast Sporobolomyces roseus for biosynthesis of 13C isotopically labelled 18-carbon unsaturated fatty acids and trans 18:1 and 18:2 derivatives through synthesis

An oleaginous and psychrotrophic strain (F38-3) of Sporobolomyces roseus Kluyver & van Niel was isolated from a salt marsh environment in Nova Scotia, Canada following a screening program to select for high producers of 18-carbon unsaturated fatty acids. Fatty acid production was characterised as a function of temperature at 20 g glucose L(-1), and optimal yields were obtained at 14°C, achieving 5.7 g dw biomass and 39.2% total fatty acids by dry weight, with 18:1, 18:2 and 18:3 all-cis fatty acids accounting for 49.4%, 14.3% and 6.7% of total fatty acids (TFA), respectively--the highest reported for this species. Production of 18:3 was inversely correlated to growth temperature, rising from 2% of TFA at 30°C to 8.9% at 6°C. Cultivation of isolate F38-3 on universally (13)C (U-(13)C) labelled glucose and subsequent transesterification and isolation of the fatty acid methyl esters (FAMEs) by preparative chromatography yielded pure, highly (13)C-enriched (>90%) 18:1, 18:2 and 18:3 all-cis FAMEs. The U-(13)C 18:1 FAME was catalytically converted to U-(13)C 18:1 trans-9 and purified to >99.5% purity. The U-(13)C 18:2 was converted by alkaline isomerisation into a 50/50 mixture of 18:2 cis-9, trans-11 and 18:2 trans-10, cis-12 isomers and purified to >95.0% purity. Overall, 10%, by weight, of labelled glucose fed to isolate F38-3 was recovered as fatty acid methyl esters and 7.5% as 18-carbon unsaturated fats, and the final isomerisation reactions resulted in yields of 80% or greater. The ultimate goal of the work is to develop methodologies to produce (13)C-labelled metabolic tracers as tools to study the metabolism of trans fats.

Highly efficient conversion of carbon dioxide catalyzed by polyethylene glycol-functionalized basic ionic liquids

A series of polyethylene glycol (PEG)-functionalized basic ionic liquids (ILs) were developed for efficient CO2 conversion into organic carbonates under mild conditions. In particular, BrTBDPEG150TBDBr was proven to be a highly efficient and recyclable catalyst for the synthesis of cyclic carbonates without utilization of any organic solvents or additives. This is presumably due to the activation of epoxide assisted by hydrogen bonding and activation of CO2 by the ether linkage in the PEG backbone or through the formation of carbamate species with the secondary amino group in the IL cation on the basis of in situ FT-IR study under CO2 pressure. In addition, the subsequent transesterification of cyclic carbonate e.g. ethylene carbonate (EC) with methanol to dimethyl carbonate (DMC) can also be effectively catalyzed by BrTBDPEG150TBDBr, thanks to the activation of methanol by the secondary and tertiary nitrogen in the IL to easily form CH3O−, realizing a so-called “one-pot two-stage” access to DMC from CO2 without separation of cyclic carbonate by using one kind of single component catalyst. Therefore, this protocol represents a highly efficient and environmentally friendly example for catalytic conversion of CO2 into value-added chemicals such as DMC by employing PEG-functionalized basic ILs as catalysts.

DFT study of gas phase acid-catalyzed ethanolysis of butyric acid triglyceride

The reaction mechanism of the acid-catalyzed transesterification reaction of butyric acid triglyceride was studied employing the Density Functional Theory (DFT). Three different pathways were considered for the three steps of the transesterification. Each step of the reaction proceeds through a concerted mechanism with one single transition state and without the formation of a tetrahedral intermediate. For transition states at each step of the reaction, bond formation was observed between the carbonyl carbon and the oxygen of the incoming nucleophilic and bond breaking between this carbon and the oxygen of the leaving group. This occurs concomitantly with proton transfer from the nucleophilic oxygen to the oxygen of the leaving group. Bond order analysis revealed the degree of bond breaking and formation in transition states which are stabilized through interactions with both attacking and leaving groups. DFT results show that the transesterification of the center ester bond followed by the subsequent transesterification of the outside ester bonds is most probably the pathway through which the reaction proceeds.

Biodiesel production from crude canola oil by two-step enzymatic processes

Crude canola oil (CCO) contains about 100–300 ppm of phospholipids, which have shown negative effects on biodiesel/buffer solution phase separation, resulting in low biodiesel production yield. Therefore, phospholipids should be removed before transesterification by a degumming process for efficient production of biodiesel. In this study, two-step enzymatic processes (degumming and transesterification) were carried out for the production of biodiesel from CCO. Degumming of CCO was performed using phospholipase A2 as a degumming reagent. The initial phospholipid content was reduced to less than 5 ppm by enzymatic degumming. The effects of three formulations of enzyme catalyst on the efficiency of transesterification were investigated. As a result, conversion rates of degummed CCO to fatty acid methyl esters (FAME) were 68.56%, 70.15%, and 84.25%, respectively. Lipase formulation composed of a 1:1 (vol:vol) enzyme mixture of Rhizopus oryzae and Candida rugosa showed the best performance among those tested. In order to recover and reuse the lipase catalyst efficiently, a 1:1 enzyme mixture of R. oryzae and C. rugosa was immobilized on silica gel. The immobilized lipase was used in subsequent transesterification optimization experiments. Optimization of transesterification was performed by response surface methodology (RSM). A total of 20 experiments based on RSM were carried out, and the optimal reaction conditions appeared to be 24.4% (w/w) immobilized catalyst, 13.5% (w/w) buffer solution, and 15.8% (w/w) methanol based on oil mass. Conversion rate of degummed CCO to FAME was determined to be 88.9% under optimal conditions.

Effects of solid pre-treatment towards optimizing supercritical methanol extraction and transesterification of Jatropha curcas L. seeds for the production of biodiesel

Experimental studies for in situ extraction and transesterification of oil seeds had been carried out recently for the process intensification of biodiesel production. As opposed to the conventional method, the solid oil seeds would be in direct contact with the transesterification reagent. Both the oil extraction and subsequent transesterification process to biodiesel will occur simultaneously. Consequently, solid pre-treatments would play a critical role to ensure that the oil seeds are in a state for optimal oil extraction. Apart from obtaining a higher yield, this could also ensure that the oil extraction phase would not bottleneck the entire in situ extraction and transesterification process. However, solid pre-treatments could be both cost and energy intensive and therefore should be carefully selected for optimum advantages. In this experimental work, ground Jatropha curcas L. seeds were subjected to pre-treatments processes including de-shelling, sieving, drying and heat treatment at five different temperatures (45–105 °C) and two different durations (12 and 24 h) before undergoing single-step supercritical methanol extraction and transesterification. Conventional two-step extraction and transesterification was also performed as comparison to the single-step process. The effects of each pre-treatment were analyzed and optimized towards two responses (extraction and FAME yield). The highest extraction and FAME yield for the two-step and single-step processes were 66.82% w/w, 114.87% w/w and 68.50% w/w, 128.78% w/w respectively. Single-step supercritical methanol extraction and transesterification was found to be able to provide a higher extraction and FAME yield for the production of biodiesel with less pre-treatment stages and intensity as compared to the conventional two-step process. Therefore, this is a highly promising approach to reduce the high biodiesel production cost which is currently impairing the industry.

Kinetics of methyl ester production from mixed crude palm oil by using acid-alkali catalyst

The production of biodiesel from high free fatty acid mixed crude palm oil using a two-stage process was investigated. The kinetics of the reactions was determined in a batch reactor at various reaction temperatures. It was found that the optimum conditions for reducing high free fatty acid (FFA) in MCPO (8–12 wt.%/wt oil) using esterification was a 10:1 molar ratio of methanol to FFA and using 10 wt.%/wt of sulfuric acid (based on FFA) as catalyst. The subsequent transesterification reaction to convert triglycerides to the methyl ester was found to be optimal using 6:1 molar ratio of methanol to the triglyceride (TG) in MCPO and using 0.6 wt.%/vol TG sodium hydroxide as catalyst. Both reactions were carried out in a stirred batch reactor over a period of 20 min at 55, 60 and 65 °C. The concentration of compounds in each sample was analyzed by Thin Layer Chromatography/Flame Ionization Detector (TLC/FID), Karl Fischer, and titration techniques. The results were used for calculating the rate coefficients by using the curve-fitting tool of MATLAB. Optimal reaction rate coefficients for the forward and reverse esterification reactions of FFA were 1.340 and 0.682 l mol −1 min −1, respectively. The corresponding optimal transesterification, rate coefficients for the forward reactions of TG, diglyceride (DG), and monoglyceride (MG) of transesterification were 2.600, 1.186, and 2.303 l mol −1 min −1, and for the reverse reactions were 0.248, 0.227, and 0.022 l mol −1 min −1, respectively.

Synthesis of 3-cyclohexylpropyl caffeate from 5-caffeoylquinic acid with consecutive enzymatic conversions in ionic liquid

We developed a convenient one-pot procedure for conversion of 5-caffeoylquinic acid to 3-cyclohexylpropyl caffeate, which exhibits an antiproliferative effect toward various human tumor cells. The procedure was comprised of two consecutive reactions by chlorogenate hydrolase (EC 3.1.1.42) from Aspergillus japonicus and Candida antarctica lipase B, and was performed using an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as the reaction solvent. When various caffeoylquinic acids from coffee beans, namely, 3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, 3,5-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic acid were used, the first alcoholysis reaction with methanol using chlorogenate hydrolase produced methyl caffeate with conversion yields of 60.0%, 61.3%, 86.0%, 92.7%, and 114.0%, respectively, to each individual substrate. Two caffeoyl groups of dicaffeoylquinic acids would be used for the synthesis of methyl caffeate. In the subsequent transesterification reaction by C. antarctica lipase B with 3-cyclohexyl-1-propanol, the methyl caffeate produced was converted to 3-cyclohexylpropyl caffeate under reduced pressure to remove the by-product methanol. In the one-pot synthesis, the methyl caffeate was transesterified efficiently to 3-cyclohexylpropyl caffeate by C. antarctica lipase B with deactivation of chlorogenate hydrolase by taking advantage of the difference between the optimum temperatures for the two enzymes. This system provided 12.8 mM 3-cyclohexylpropyl caffeate from 15 mM 5-caffeoylquinic acid with conversion yield of 85.3%.

Study of esterification and transesterification in biodiesel production from used frying oils in a closed system

Used frying oils are a good alternative for biodiesel production but their treatment is more complex than fresh vegetable oils. Used frying oils contain a large amount of free fatty acids, so an esterification step is necessary before transesterification. This reaction is usually carried out in batch reactors with pressure and temperature conditions (ambient pressure and 60 °C) where the esterification reaction acts as the limiting step of the production. The aim of this work was to investigate the acidity removal and the subsequent transesterification at different temperatures and mole ratios in a batch reactor in order to improve the biodiesel production from used frying oils. The influence of temperature was studied in order to know the kinetics of esterification. The reaction rate increased when the temperature was increased. The experimental results were found to fit a first-order kinetic law for the forward reaction and a second-order for the reverse reaction. The influence of temperature was found to be insignificant on the transesterification reaction. Nevertheless, methanol/oil mole ratio influenced up to 6.0:1. The influence of upper mole ratios was insignificant on the FAME content evolution. Based on the experimental results, biodiesel from used frying oil did not fulfil all the specifications from EN 14214 Standard due to the chemical modifications in the oil during cooking (presence of polar compounds). Therefore, biodiesel was proposed for use in combustion processes or in blends with biodiesel from other vegetable oils or even animal fats, which had not undergone chemical modifications.

A study on the carboxylation of glycerol to glycerol carbonate with carbon dioxide: The role of the catalyst, solvent and reaction conditions

Glycerol was reacted with CO 2 (5 MPa) at 450 K in presence of Sn-catalysts ( n-Bu 2Sn(OMe) 2 1, n-Bu 2SnO 2 or Sn(OMe) 2 3), using either glycerol or tetraethylene glycol dimethyl ether (tedmg) as reaction medium. 1 was much more active than 2. 1 was demonstrated to convert into n-Bu 2Sn(glycerol-2H) 4 upon reaction with glycerol and elimination of MeOH. Monomeric 4 is proposed to be the active species in catalysis. It converted into a polymeric material with time with consequent reduction of its catalytic activity. Also, after the first catalytic cycle 4 was converted into an oligomeric material that did not contain glycerol. This also caused the reduction of the catalytic activity. 3 was able to uptake CO 2 but was not able to promote the carboxylation of glycerol. 1 and 2 also promoted the trans-esterification of dimethylcarbonate (DMC) with glycerol to afford glycerol carbonate, but at a lower rate than the direct carboxylation of glycerol. This fact seems to rule out that the carboxylation of glycerol may proceed through the preliminary formation of DMC and its subsequent trans-esterification.

Biodiesel from extracted fat out of meat and bone meal

Nine non-halogenated solvents for the extraction of fat from meat and bone meal (MBM) were evaluated by the accelerated solvent method. Yields of about 15% were obtained with all solvents, but n-hexane was found to be the most suitable extraction solvent, because it is relatively cheap and has a low boiling point. Fat was also extracted from MBM on preparative scale (600 g) by immersion, and the extracted material was analysed for impurities that could affect the subsequent transesterification. The extracted material was converted into fatty acid methyl esters (FAME) via a two-step process. For further purification, the raw FAME were distilled under reduced pressure. The final product was analysed according to the European specification for biodiesel (EN 14214). Almost all of the values were within the specifications, except the cold-temperature behaviour and the oxidation stability. All in all, extracted fat from MBM is a potential feedstock for the production of biodiesel.

Cantharidin analogues: synthesis and evaluation of growth inhibition in a panel of selected tumour cell lines

Diels–Alder addition of furans (furan, furfuryl alcohol, and 3-bromofuran) to maelic anhydride yields three distinct 5,6-dehydronorcantharidins. Hydrogenation of (4,10-dioxatricyclo[5.2.1.0]decane-3,5-dione) ( 4a), in dry ethanol affords the monoester (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic aid monoethyl ester) ( 6). Subsequent transesterification affords a series of monoesters (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid monomethyl ester ( 7)), 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid monopropyl ester ( 8), (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid monohexyl ester ( 9)) and differentially substituted diesters (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid 2-ethyl ester 3-isopropyl ester) ( 10), and (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid 2-ethyl ester 3-phenyl ester) ( 11). Analogues were firstly screened for their ability to inhibit protein phosphatases 1 (PP1) and 2A (PP2A) as the lead compounds cantharidin ( 1) and norcantharidin ( 2) are known PP1 and PP2A inhibitors. Only analogues 4a, 6– 8 displayed good PP1 and PP2A inhibition (PP1 IC 50’s=2.0, 2.96, 4.71, and 4.82 μM, respectively; PP2A IC 50’s=0.2, 0.45, 0.41, and 0.47 μM, respectively). All analogues were also screened for their anti-cancer potential against a panel of tumour cell lines, HL60, L1210, SW480, WiDr, HT29, HCT116, A2780, ADDP, and 143B, producing GI 50 values ranging from 6 μM to >1000 μM. Analogues possessing good PP1 and/or PP2A inhibition also returned moderate to good anti-cancer activity. Analogues with substituents directly attached to the intact bicyclo[2.2.1]heptane skeleton were poor to moderate anti-cancer agents. This correlates well with their lack of PP1 or PP2A activity. Analogues capable of undergoing a facile ring opening of the anhydride or with a single carboxylate were good PP1 and PP2A inhibitors, largely correlating to the observed anti-cancer activity in all cases, except 11. Analogue 11, whist neither a PP1 nor a PP2A inhibitor shows anti-cancer activity comparable to 1 and 2. We believe that intracellular esterases generate the corresponding dicarboxylate, which is a potent PP1 and PP2A inhibitor, and that it is this species which is responsible for the observed anti-cancer activity.

ChemInform Abstract: Highly Selective One‐Pot Conversion of THP and MOM Ethers to Acetates by Indium Triiodide‐Catalyzed Deprotection and Subsequent Transesterification by Ethyl Acetate.

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Highly selective one-pot conversion of THP and MOM ethers to acetates by indium triiodide-catalysed deprotection and subsequent transesterification by ethyl acetate

A simple and efficient method is developed for the chemoselective one-pot conversion of tetrahydropyranyl (THP) and methoxymethyl (MOM) ethers of primary alcohols to the corresponding acetates by indium triiodide-catalysed deprotection and subsequent acetylation by ethyl acetate through a transesterification process.

Isolation of cholesterol oxidation products from animal fat using aminopropyl solid-phase extraction

Cholesterol oxidation products were separated from triglycerides and cholesterol in a single step on an aminopropyl solid-phase extraction column. The products were purified by subsequent transesterification and saponication, derivatized to trimethylsilyl ethers and analyzed by gas chromatography. Heated cholesterol-containing fat samples were autoxidized by bubbling air through them. When the flow-rate of air was set at 100 ml/min, the concentration of cholesterol oxidation products in the fat increased to a maximum after 1–2 h and then decreased to almost a zero level after 8 h. The concentration of cholesterol oxidation products in the fat increased over a similar time period, without reaching a maximum, when the flow-rate of air was decreased to 5 ml/min.

An RNA-dependent ATPase associated with U2/U6 snRNAs in pre-mRNA splicing.

The hydrolysis of ATP by a group of RNA-dependent ATPases (DEAD/H proteins) is required for spliceosome assembly, but not for the subsequent transesterification reactions. Little is known about the function of these ATPases in relation to the RNA conformational changes that occur in formation of active structures, in which U2/U6 small nuclear RNA (snRNA) interactions are essential for splicing to take place. Using a synthetic lethal genetic screen, we have isolated four yeast splicing factors involved in U2/U6 snRNA interactions (D.X. et al., manuscript in preparation). The RNA-dependent ATPase activity associated with one such factor, the Slt22 protein, is stimulated preferentially by annealed U2/U6 snRNAs. Both mutant slt22-1 and U2 snRNA cause a reduction in stimulation. The slt22-1 mutation blocks splicing at or before the first step, resulting in the accumulation of an unusual complex which lacks U5 snRNA. Our results indicate that the U2/U6 snRNA interactions facilitated by Slt22 are also involved in the interaction of U5 snRNA with the spliceosome.

Formation of 1,3-Dihydroxy-N-methylacridone from N-Methylanthraniloyl-CoA and Malonyl-CoA by Cell-Free Extracts of Ruta graveolens

N-Methylanthraniloyl-CoA was synthesized via N-succinimidyl N-methylanthranilate and subsequent transesterification with CoA-SH . This compound was characterized by LSIMS and NMR data. An enzyme preparation from cell suspension cultures of Ruta graveolens catalyzed the formation of 1,3-dihydroxy-N-methylacridone from N-methylanthraniloyl-CoA and malonyl-CoA with a pH optimum of 7.5.

Reactions de wittig-horner et de transesterification en une operation par activation anionique de liaisons C-H et O-H en milieu heterogene carbonate de potassium/alcool

The Wittig-Horner reaction carried out in various alcohols is accompanied by transesterification of the alkyl radical of the α, β-ethylenic ester formed. The occurrence of these two reactions in the same reaction medium is affected by the behavior of: i) the alcohol (solvent and reagent), ii) potassium carbonate (reagent and catalyst). The propensity for the two reactions to occur was found to depend on the polarity of the alcohol. Protic alcohols speeded both the Wittig-Horner and the subsequent transesterification reaction. Both reactions were quantitative despite the use of non-stoichiometric amounts of potassium carbonate. Regeneration in situ of the solid base observed in aprotic medium was markedly enhanced under these reaction conditions. The mechanism proposed for these two reactions incorporates this regeneration process.

Synthesis of Piperoyl Coenzyme A Thioester

Piperoyl-CoA, a potential intermediate in the biosynthesis of piperine. the pungent principle of pepper, was synthesized via N-succinimidyl piperate and subsequent transesterification with CoA- SH. UV-spectrophotometry of the HPLC-purified compound revealed, besides a maximum at 260 nm, a pronounced second absorption maximum at 368 nm due to the thioester linkage for which, as determined via the Fe3+-complex of piperoyl hydroxamate and with [14C]piperoyl-CoA, a molar extinction coefficient of 30.8 × 106 [cn2mol-1] was calculated.

Use of S-t-butyl acetothioacetate in the preparation of milbemycin seco-analogues

The preparation of milbemycin seco-analogues are described in which the key step involves alkylation of the γ-carbon atom by acrylaldehyde, or methacrylaldehyde of dianions generated from S-t-butyl acetothioacetate (6). Subsequent protection and transesterification of the products of these reactions with a model spiro acetal unit (1) gave acetoacetate derivatives. These compounds upon reaction with sodium borohydride and deprotection afforded the seco-species.