Conditions Of Methanolysis Research Articles

Isolation and determination of phenolic acids in rowanberry fruits (Sorbus L.) by gas chromatography

Species of the genus Sorbus L. (rowan) are woody plants growing in the Northern Hemisphere; they are of interest as decorative, food and medicinal plants. Rowan fruits contain a unique complex of macro- and microelements, as well as biologically active substances, including phenolic compounds. Complexity of the composition of plant samples requires the development of highly selective and sensitive methods for determining the content of organic components of different classes. A method for determining phenolic acids in rowan fruits is proposed. The method is based on two-stage chemical modification of the acids, and involves preparing methyl esters under acidic methanolysis conditions, liquid extraction with toluene, intermediate re-extraction into an aqueous alkaline solution, subsequent silylation with N, O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and gas chromatographic determination of the obtained derivatives using a flame ionization or mass spectrometric detector. Conditions for extraction of phenolic acids from rowan fruits were studied according to the following parameters: type of extractant, sample to the extractant mass ratio, and duration of extraction (mechanical stirring). The stage of gas chromatographic determination of obtained phenolic acid derivatives was optimized, and their chromatographic characteristics established. The possibility of achieving practically complete separation of aliphatic acids and other accompanying components of a non-acidic nature from phenolic compounds in the course of sample preparation was demonstrated; which significantly increased both the selectivity and sensitivity of the determination of analytes. The range of determined content of phenolic acids (4-hydroxybenzoic acid, 2-hydroxybenzoic acid, 4-hydroxy-3-methoxy-benzoic acid, 4-hydroxycinnamic acid, 4-hydroxy-3-methoxy-cinnamic acid) in rowan fruits was 0.005–0.5 mg/g, the limit of detection was 0.001–0.002 mg/g, the relative error was 10–15%, the sample weight was 0.5 g, the total duration of the analysis was 4 hours.

Concentration of n-3 polyunsaturated fatty acid glycerides by Candida antarctica lipase A-catalyzed selective methanolysis

n-3 polyunsaturated fatty acids (n-3 PUFA) have biologically important functions in human beings, but their contents in natural oils are usually low. This study investigated the concentration of n-3 PUFA-enriched glycerides by Candida antarctica lipase A (CAL-A)-catalyzed selective methanolysis of algal oil. First, lipases and acyl acceptors were screened. Subsequently, the methanolysis conditions including methanol concentration in aqueous solution, molar ratio of methanol to oil, reaction temperature, lipase loading and reaction time, were optimized. The results indicated that CAL-A could effectively identify n-3 PUFA during methanolysis. Saturated fatty acids and monounsaturated fatty acids were released from algal oil by CAL-A-catalyzed methanolysis, causing the production of n-3 PUFA-enriched glycerides. Under optimal conditions (3:1 of molar ratio of methanol to algal oil, 20% methanol aqueous solution, 6% CAL-A dosage, 25 °C, 18 h), the n-3 PUFA content increased from the initial 45.96% to 73.96%, with an n-3 PUFA yield of 81.76%. The reusability of CAL-A demonstrated that under optimal conditions the lipase could be used for 8 times. Therefore, this enzymatic process is efficient for synthesis of n-3 PUFA-enriched glycerides.

Cutin extraction and composition determined under differing depolymerisation conditions in cork oak leaves

Cutin is a biopolyester involved in waterproofing aerial plant organs, including leaves. Cutin quantification and compositional profiling require depolymerisation, namely by methanolysis, but specific protocols are not available. Investigate how different methanolysis conditions regarding catalyst concentration effect cutin depolymerisation and monomer release, to better define protocols for cutin content determination and composition profiling. Cork oak (Quercus suber) dewaxed leaves were reacted with five sodium methoxide (NaOMe) concentrations. Extracts were analysed: glycerol by high-performance liquid chromatography (HPLC) and long-chain lipids by gas chromatography-mass spectrometry (GC-MS). Cutin was completely removed by 3% NaOMe (8.4% of dewaxed leaves), while mild 0.1% and 0.01% NaOMe methanolysis only depolymerised 14% of total cutin. Reactivity of cutin ester bonds is not homogeneous and glyceridic ester bonds are more easily cleaved, releasing the existing glycerol already under the mildest conditions (0.53% with 0.01% NaOMe and 0.41% with 3% NaOMe). The composition of cutin extracts varies with depolymerisation extent, with easier release of alkanoic acids and alkanols, respectively, 34.9% and 8.8% of total monomers at 0.1% NaOMe, while ω-hydroxyacids (49.3% of total monomers) and α,ω-diacids (9.0% of the monomers) are solubilised under more intensive reactive conditions. Cutin of Quercus suber leaves is confirmed as a glyceridic polyester of ω-hydroxyacids and alkanoic acids, with minor content of α,ω-diacids, and including coumarate moieties. The protocol for the determination of cutin content and compositional profiling was established regarding catalyst concentration. The molar composition of cutin suggests a macromolecular assembly based on glycerol linked to lipid oligomeric chains with moderate cross-linking.

Structures of alkaline earth metal oxides supported on MCF and the enhanced catalytic performance for methanolysis of polycarbonate

Mesoporous solid bases catalysts were prepared by impregnation of a certain amount of alkaline-earth metals species on the synthesized MCF support and used in the methanolysis of PC. Compared with the synthesized SBA-15 solid base catalysts, CaO/MCF catalysts with larger pore size, pore volume and higher active species dispersion exhibited higher catalytic activity. The influences of supported catalyst physicochemical properties and methanolysis conditions were also investigated. The results indicated that methanolysis rate of PC was closed to 100%, and yield of BPA was over 95% under the proper reaction conditions with the excellent performance of 12%CaO/MCF catalyst. The catalyst stability study showed that 12%CaO/MCF had good catalytic activity after five circles. At the same time, the possible methanolysis mechanism of PC was proposed.

Separation and characterization of products from acidic methanolysis of plasmalogenic lipids by two-dimensional gas chromatography with online reduction

The complexity of determining the composition of animal tissue lipids is greatly increased by the presence of plasmalogens in which the alkyl chain is linked to glycerol by an enol ether bond instead of being esterified. Acidic methanolysis of animal tissue lipids provides the simultaneous scission of acyl and alkenyl ether moieties, but the complexity of the products of reaction poses a great challenge in their gas chromatographic analysis. Two-dimensional gas chromatography with online reduction (GC-OR × GC) provided the resolution of all components contained in acid methanolyzed animal lipids, taking advantage of the selective hydrogenation of alkenyl ether methanolysis products prior to the second-dimension separation (2D). In this study, we also studied the chemical transformations occurring during the acidic methanolysis of animal lipids and the subsequent gas chromatographic analysis. In particular, we observed that using methanolysis reagents contaminated with water resulted in the undesired formation of fatty aldehydes, and we made recommendations on how to avoid these side reactions using proper methanolysis conditions. Products of acidic methanolysis were studied by GC-OR × GC, GC-MS, NMR spectroscopy, and GC with flame ionization detection (GC-FID). We defined the GC-FID elution order of animal lipid acidic methanolysis products using 100 m × 0.25 mm 100% bis(cyanopropyl)siloxane columns and two different set of elution conditions: isothermal elution at 180°C, and a temperature program optimized for dairy fats. A simple procedure for isolating dimethyl acetals (DMA) prior to GC analysis is also described.

Optimization of the comparative continuous process of ethyl and methyl ester productions using a static mixer reactor: a response surface methodology approach

ABSTRACT Static mixer was used as the continuous reactor in the biodiesel production. This study reports methyl ester and ethyl ester production from refined palm oil (RPO) using a 10 m long static mixer reactor. Alcohol content (vol.%), KOH (g.L−1), and static mixer length (m) were optimized to determine the ester purities with response surface methodology. As a result, 96.5 wt.% ester purity was substituted into the predicted models of FAME and FAEE. The appropriate conditions for methanolysis of 44.7 vol.% of methanol, 11.2 g.L−1 of KOH, and 4.8 m of static mixer length was obtained. The appropriate condition for ethanolysis were 45.3 vol.% of ethanol, 12.5 g.L−1 of KOH, and 5.1 m of static mixer length. From all statistical analysis data, KOH has a less significant effect when compared with other parameters, whereas alcohol content and static mixer length are first- and second-key, respectively. Alcohol consumption and reaction time for ethanolysis are more than for methanolysis. Regarding glycerol–ethyl ester separation, the glycerol phase of ethyl ester is more difficult than methyl ester.

Amygdalus Scoparia as a New Feedstock for Biodiesel Production

Biodiesel is an attractive alternative fuel because of its nontoxicity and biodegradability which can be produced from vegeTable oils and animal fats. Finding a proper feedstock has an important role on the biodiesel characteristics and the price. Therefore in this research, amygdalus Scoparia oil was used as a cheap potential feedstock for biodiesel production which is widespread in arid regions in Iran. This native plant contains 58-60% oil which is consist of 62.81% oleic acid and 23.54% linoleic acid. Biodiesel was produced from transesterification of extracted oil in reaction with methanol in the presence of potassium hydroxide as a catalyst. The reaction variables used were methanol/oil molar ratio (4:1-7:1), catalyst concentration (0.25-1.5%), and reaction time (1-7 h). Optimal conditions for methanolysis were 1% KOH concentration, MeOH/oil of molar ratio 6:1 for a period of 7 h. The yield of biodiesel produced under optimal conditions were 97.32. Overall, amygdalus Scoparia kernel is a promising feedstock for biodiesel production and large cultivation will help to reduce the product cost.

Synthesis of Ferric–Manganese Doped Tungstated Zirconia Nanoparticles as Heterogeneous Solid Superacid Catalyst for Biodiesel Production From Waste Cooking Oil

The solid superacid catalyst ferric-manganese doped tungstated zirconia (FMWZ) nanoparticles was prepared by impregnation reaction followed by calcination at 600°C for 3 hr and had been characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), X-ray fluorescence (XRF), transmission electron microscopy (TEM), and Brunner-Emmett-Teller (BET) surface area measurement. The transesterification reaction was used to determine the optimum conditions of methanolysis of waste cooking oil with FMWZ nanoparticles as heterogeneous solid superacid catalyst. The reactions variables such as reaction temperatures, catalyst loading, molar ratio of methanol/oil and reusability were also assessed which effects the waste cooking oil methyl esters (WCOME’s) production yield. The catalyst was reused ten times without any loss in activity and maximum yield of 96% was achieved at the optimized conditions of reaction temperature of 200°C; stirring speed of 600 rpm, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The fuel properties of the WCOME’s were discussed in light of ASTM D6751 biodiesel standard.

Biodiesel synthesis using K2CO3/Al-O-Si aerogel catalysts

In this study, catalysts for fatty acid methyl esters (FAME or biodiesel) synthesis with K2CO3 as the active component on an alumina/silica support were synthesized using the sol-gel method, which was followed by drying the ?dense? wet gels with supercritical carbon dioxide to obtain the aerogels. The prepared catalysts were characterized by XRD analysis, FTIR spectroscopy and N2 physisorption at 77 K, and tested in the methanolysis of sunflower oil. The effects of reaction variables, such as reaction time, temperature and methanol to oil molar ratio, on the yield of FAME were investigated. The aerogel catalysts with K2CO3 as the active component on an alumina/silica support exhibited good activity in the methanolysis of sunflower oil. The leaching of potassium when the catalyst was in contact with pure methanol under the working conditions of methanolysis was also tested in this study, indicating that it occurred only at higher temperatures, while at lower ones, it was negligible.

Optimization of Biodiesel Production Catalyzed by Fungus Cells Immobilized in Fibrous Supports

A circulating packed-bed bioreactor system using fibrous nonwoven fabric as the immobilization matrix was suitable for simultaneous cell growth and immobilization of Rhizopus oryzae fungus cells, which could be used for lipase-mediated production of biodiesel by methanolysis of soybean oil. Response surface methodology and 5-level-5-factor central composite rotatable design was proved to be a powerful tool for the optimization of methanolysis conditions catalyzed by immobilized R. oryzae whole cell biocatalyst. A quadratic polynomial regression model was used to analyze the relationship between the yield and the significant reaction parameters. The analysis confirmed that water content, molar ratio of methanol to oil, cell weight, and reaction time were the significant factors affecting the yield at a 95% confidence level (p < 0.05). Under the optimum condition at 10.97% (w/w) water content, 0.64 molar ratio of methanol to oil, 2.25% (w/w) cell weight, and 23.3 h reaction time, the predicted value of yield was 72.6%. Validation experiments with yields of 70.77 +/- 2.46% verified the availability and the accuracy of the model.

Ionic liquids as a reaction medium for lipase-catalyzed methanolysis of sunflower oil

Ionic liquids, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIm][PF(6)]) and 1-ethyl-3-methyl imidazolium hexafluorophosphate ([EMIm][PF(6)]), were used for the methanolysis of sunflower oil using Candida antarctica lipase (Novozyme 435) and gave yields of fatty acid methyl esters at 98-99% within 10 h. The optimum conditions of methanolysis in hydrophobic ionic liquids are 2% (w/w) lipase, 1:1 (w/w) oil/ionic liquid and 1:8 (mol/mol) oil/methanol at 58-60 degrees C. Methanolysis using hydrophilic ionic liquids, 3-methyl imidazolium tetrafluoroborate ([HMIm][BF(4)]) and 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIm][BF(4)]), gave very poor yields. A hydrophobic ionic liquid thus protects the lipase from methanol. Recovered ionic liquids and lipase were used for four successive reaction cycles without any significant loss of activity.

The chemistry of nitrogen coordinated tertiary carboxamides: a spectroscopic study on bis(picolyl)amidecopper(ii) complexes

Metal coordination of the electrically neutral nitrogen atom of a tertiary carboxamide reduces the barrier to C-N-bond rotation and activates the amide towards methanolysis. X-Ray crystallographic studies indicate that this reactivity is correlated to a lifting of the amide resonance structure and concurrent pyramidalization at nitrogen. However, mechanistic data in solution have not been obtained. It became evident that structural mobility is characteristic of the complexes and the crystallographic data do not fully account for relevant reactive species. In this report we summarize IR, UV-vis, and EPR spectra of amide nitrogen coordinated bis(picolyl)amide complexes with copper(II) triflate and copper(II) chloride. A comparison between spectra sampled in the aprotic solvents dichloromethane and acetonitrile, as well as under methanolysis conditions reveals the nature of several species formed in solution. The key reactions are (I) ligand exchange involving either CH3CN or CH3OH, or, in IR experiments, bromide ions from KBr, (II) coordination-dissociation equilibria involving the urethane protecting groups of amino acid substituted ligands Boc-Xaa-bpa (Boc = tert-butoxycarbonyl, Xaa = glycine, alanine, and leucine, respectively, bpa = bis(picolyl)amine), (III) dissociation of a chloro ligand from LCuCl2 complexes and formation of square-pyramidal complex cations [LCuCl]+, and finally (IV) complete dissociation of the polydentate tertiary amide ligand to produce free copper ions in solution. Taken together, the results provide a fairly detailed qualitative picture of the processes which accompany the amide bond methanolysis.

Methanolysis investigation of commercially available polyurethane foam

Methanolysis investigation of a model polyurethane (PUR), poly[ethylene=methylene bis(4-phenylcarbamate)], and the commercially available PUR foam, Sofran ® is reported. The methanolysis conditions were in the temperature range from 160 to 300 °C and at pressures up to 15 MPa, partly in the supercritical state of methanol. For both the PURs the decomposition percentages are over 90% at temperatures above 200 °C. Methyl carbamate was formed in the reaction mixtures by the decomposition at all temperatures studied. With the GC measurement of the carbamate, it is revealed to be decomposed into methanol and 4,4′-methylenediphenyl diisocyanate (MDI). The decomposition temperature of the carbamate was determined to be 250 °C by TG–DTA measurement. The chemical recycling process flow on PUR compounds is proposed.

Lipase-catalyzed production of biodiesel fuel from vegetable oils contained in waste activated bleaching earth

Waste bleaching earths from crude vegetable oil refining process contain approximately 40% of its weight as oil. Low valued oils are potential substrates for biodiesel fuel production. Vegetable oils from waste bleaching earth samples were organic-solvent extracted and identified as soybean, palm and rapeseed oil. Methanolysis was efficiently catalyzed by Rhizopus oryzae lipase in the presence of high water content, and by a single addition of methanol. R. oryzae lipase was not inactivated by methanol in concentrations lower than 4 milli-equivalents and 75% water content. Optimum conditions for methanolysis of extracted oils were 75% water content (by weight of substrate), an oil/methanol molar ratio of 1:4, and 67 IU/g of substrate with shaking of 175 rpm for 96 h at 35 °C. The highest conversion yield reached 55% (w/w) with palm oil after 96 h of reaction. Adverse viscosity conditions might have influenced methanolysis of extracted soybean and rapeseed oil in spite of high water or methanol concentrations.

Lipase catalyzed methanolysis of vegetable oils in aqueous medium by Cryptococcus spp. S-2

A number of factors affecting the methanolysis of vegetable oils in aqueous medium by Cryptococcus spp. S-2 lipase were investigated. The crude lipase from the yeast efficiently catalyzed the methanolysis of vegetable oils (oil/methanol molar ratio of 1:1) in the presence of 40 wt.% water. The methyl ester content was high with rice bran oil at 30 °C for 96 h and further optimization studies were carried out with varying amount of enzyme, water or methanol. The enzyme was not inactivated by shaking in a mixture containing 4 Meq of methanol against the oil and 100 wt.% water by weight of the substrate and the methyl ester contents increased with increasing molar equivalents of methanol and water contents from 60 to 100 wt.%. The optimal methanolysis conditions were an oil/methanol molar ratio of 1:4, a water content of 80 wt.% by weight of the substrate containing 2000 U of crude lipase with shaking at 160 rpm for 120 h at 30 °C. Thus, the reaction was conducted in a single step to avoid the stepwise addition of methanol and the methyl ester contents reached 80.2 wt.% at 120 h. These same conditions were applied for alcoholysis of rice bran oil and primary alcohols to their respective alkyl ester derivatives which are excellent substitutes for diesel fuel.

Quantitative Cleavage of theN-Glycosidic Bond under the Normal Conditions of Methanolysis Used for the Analysis of Glycoprotein Monosaccharides

The most common method used for the liberation of monosaccharides from glycoproteinN-glycans involves anhydrous methanolysis because it liberates almost quantitatively monosaccharides asO-methylglycosides, which are resistant to further degradation. However, it is generally assumed that this method does not cleave quantitatively theN-glycosidic bonds. This paper demonstrates that classical methanolysis conditions quantitatively cleave theN-glycosidic bond (96%), liberating glucosamine (and not itsO-methylglycosides) and other minor reaction products which were identified. Because otherN-acetyl-d-glucosamine (GlcNAc) residues are quantitatively liberated as theO-methylglycosides of glucosamine, the GlcNAc residue involved in theN-glycosidic bond is separated from the others using gas chromatography of heptafluorobutyrate derivatives.

Possible fatty acyl pheromone precursors in Spodoptera littoralis. Search for 11- and 12-hydroxytetradecanoic acids in the pheromone gland.

Lipid extracts of Spodoptera littoralis pheromone glands submitted to acid methanolysis using: (i) sulfuric acid/methanol/benzene (0.1:4:2, by vol) at 90 degrees C for 1 h; (ii) 12 N HCI/methanol (1:2, vol/vol) at 90 degrees C for 1 h, or (iii) 14% BF3-MeOH at 90 degrees C for 1 h did not reveal the presence of either 11- or 12-hydroxytetradecanoic acid in the extracts, as concluded from the gas chromatography-mass spectrometry analyses. Under the above methanolysis conditions, a synthetic sample of methyl (14, 14, 14-2H3) 12-hydroxytetradecanoate remained unaltered. These results may indicate that formation of (E)-11-tetradecenoic acid from tetradecanoic acid does not occur in the pheromone gland by dehydration of an intermediate hydroxyacid. Acid methanolysis of a lipidic extract using BF3-MeOH led to the formation of a mixture of methoxy fatty acid methyl esters, identified by gas chromatography-mass spectrometry. These methoxy derivatives should arise from BF3-catalyzed addition of methanol to the double bond of the natural monounsaturated fatty acyl derivatives present in the gland. Thus, under the same conditions, a synthetic sample of methyl (Z)-11-tetradecenoate was partially transformed into methyl 11-methoxytetradecanoate and methyl 12-methoxytetradecanoate. This reaction might be a useful alternative procedure to obtain methoxy derivatives of olefins, which are very helpful for the structural characterization of the parent alkenes.

Assessment of methanolysis for the determination of composite sugars of gelling carrageenans and agarose by HPLC

The characterization of the main composite sugars of commercial gelling red algae galactans (agarose, iota and kappa carrageenans) by methanolysis and separation of the methyl glycosides produced by high performance liquid chromatography is described. The methanolysis (methanolic hydrochloric acid strength, temperature, and reaction time) was optimized in order to release monosaccharides in near quantitative yield. The results were compared to those obtained by (1) gas chromatography of the alditol acetates of the neutral sugars released by acid hydrolysis and (2) specific colorimetric determination of the acid-labile 3,6-anhydrogalactosyl residue. Conditions such as methanolic 0.125 M HCl for 1 h at 85°C were sufficient to release all of the galactosidic and 3,6-anhydrogalactosidic bonds for iota carrageenan without apparent degradation of the anhydrogalactosyl unit. However, with the same conditions, the yields of 3,6-anhydrogalactosyl residues were 80 and 70% for kappa carrageenan and agarose, respectively. These yields were not improved by stronger conditions. At the opposite extreme, under very mild methanolysis conditions such as methanolic 0.01 M HCl at 100°C for 1 h, agars and gelling carrageenans were well differentiated by the respective determination of agarobiose- and carrabiose-dimethyl acetal which are well-separated on octadecyl reversed phase HPLC columns with water as eluent.

Synthesis and Cycloaromatization of a Neocarzinostatin Chromophore Analogue Equipped with an Intramolecular Nucleophile

A new 10 membered ring analogue of neocarzinostatin chromophore 4 [12-(2-acetylthioethyl)-7,7-dimethyl-5-oxobicyclo-[8.3.0]trideca-1(2),10(11)-diene-3,8-diyne] equipped with the acetylthioethane group undergoes intramolecular conjugate addition of the corresponding thiolate under weakly basic methanolysis conditions leading to reductive cycloaromatization to give the benz[5,6]indeno[1,2-b]thiophene ring system. The intermediacy of the phenyl radical 19 has been supported by the abstraction of carbon-bound deuterium.

Uronic acid analysis by high-performance liquid chromatography after methanolysis of glycosaminoglycans

Two high-performance liquid chromatographic applications for the study of glucuronic and iduronic acid in glycosaminoglycans are presented. In the simplest form these uronic acids are separated on a reversed-phase column as their l- methylglycoside-6-methyl esters, i.e., the form in which they are recovered after methanolysis. The sensitivity for glucuronic acid is somewhat increased if the polysaccharide is deaminated prior to methanolysis, the subsequent separation being performed on a weak ion-exchange column. To allow this separation, however, an extra preparative step is necessary, consisting of alkaline hydrolysis of the ester bonds. Using these separations, the conditions for methanolysis were studied. Optimal release of uronic acids was achieved after 30–50 h of methanolysis using 1 M dry HCl in methanol at 100°C.