Identification and Quantitation of Reaction Intermediates and Residuals in Lipase-Catalyzed Transesterified Oils by HPLC

A high-performance liquid chromatography (HPLC) unit equipped with size exclusion column and a refractive index detector was used for simultaneous monitoring, identification, and quantitation of the reaction components from lipase-catalyzed transesterification of three oils. The procedure simultaneously separated and detected the unreacted triacylglycerols (TAG), diacyl-, and monoacyl-glycerol (DAG and MAG) co-products, residual alcohol as well as free fatty acid (FFA) based on retention times. The chromatograms showed well separated and resolved peaks. The elution of the components from the transesterification reaction in increasing order was: TAG < DAG < FFA < MAG. Generally, higher alcohol ratios decreased the conversion of TAG in all the oils studied with between 14% and 94% of TAG remaining at all the treatment combinations. Higher amount of salmon skin oil (SSO) TAG was generally converted to DAG than Rothsay composite (RC) and olive oil (OO) TAG. Relatively higher amount of OO DAG was converted to MAG than SSO and RC with only 5–14% DAG remaining in OO. RC and OO generally accumulated less MAG, and this was reflected as lower MAG levels in RC (<6%) and OO (<14%) compared with SSO (<27%). For the various treatment combinations and the three oils used in this study, the least amount of FFA was recorded in transesterified OO with a maximum of approximately 4%. This HPLC method can be used as a simple and fast technique to analyze the reaction components and products of transesterification reactions without the need for additional derivatization steps.     

Esterification of caprylic acid with alcohol over nano-crystalline sulfated zirconia

The catalytic activity of nano-crystalline sulfated zirconia catalyst, prepared by sol–gel method and characterized by various analytical tools, was evaluated for the esterification of caprylic acid with different short chain alcohols. The lower concentration of catalyst (0.5 wt%) exhibited 96–98% conversion of caprylic acid with methanol and 100% selectivity for methyl caprylate at 60 °C. The conversion was decreased with increasing carbon chain of alcohols namely with ethanol, n-propanol and n-butanol at 60 °C but increased significantly (91–98%) at higher reaction temperature. The selectivity for respective alkyl caprylate was observed to be 100% irrespective of the alcohol used. The activity of the catalyst was slightly decreased with successive five reaction cycles due to the water formed during the reaction.     

Catalytic Transfer Hydrogenation and Acid Reactions of Furfural and 5-(Hydroxymethyl)furfural over Hf-TUD-1 Type Catalysts

Heterogeneous catalysis, which has served well the petrochemical industry, may valuably contribute towards a bio-based economy by sustainably enabling selective reactions to renewable chemicals. Carbohydrate-containing matter may be obtained from various widespread sources and selectively converted to furanic platform chemicals: furfural (Fur) and 5-(hydroxymethyl)furfural (Hmf). Valuable bioproducts may be obtained from these aldehydes via catalytic transfer hydrogenation (CTH) using alcohols as H-donors under relatively moderate reaction conditions. Hafnium-containing TUD-1 type catalysts were the first of ordered mesoporous silicates explored for the conversion of Fur and Hmf via CTH/alcohol strategies. The materials promoted CTH and acid reactions leading to the furanic ethers. The bioproducts spectrum was broader for the reaction of Fur than of Hmf. A Fur reaction mechanism based on literature data was discussed and supported by kinetic modelling. The influence of the Hf loading and reaction conditions (catalyst load, type of alcohol H-donor, temperature, initial substrate concentration) on the reaction kinetics was studied. The reaction conditions were optimized to maximize the yields of 2-(alkoxymethyl)furan ethers formed from Fur; up to 63% yield was reached at 88% Fur conversion, 4 h/150 °C, using Hf-TUD-1(75), which was a stable catalyst. The Hf-TUD-1(x) catalysts promoted the selective conversion of Hmf to bis(2-alkoxymethyl)furan; e.g., 96% selectivity at 98% Hmf conversion, 3 h/170 °C for Hf-TUD-1(50).     

Preparation and electrochemical properties of palladium(0) complexes coordinated by quinones and 1,5-cyclooctadiene

The complexes Pd(quinone)(COD) (COD = 1,5-cyclooctadiene) are prepared by a ligand substitution reaction of Pd₂(DBA)₃ (DBA = dibenzylideneacetone) in the presence of both quinone and COD. Palladium(0) complexes coordinated by quinones only are formed in the reaction in the absence of COD. The cyclic voltammetric behavior of Pd(quinone)(COD) has been studied. The reduction potentials for quinones shifted toward negative values on coordination to palladium(0). The oxidation potentials for the central palladium(0) in Pd(quinone)(COD) depend on the electron-withdrawing ability of the free quinones, and are in the following series: quinone = p-benzoquinone < 5,8-dihydro-1,4-naphthoquinone ～ 1,4-naphthoquinone < duroquinone. The shift of oxidation potentials for Pd(quinone)(COD) on changing the quinones as ligands is in contrast to that of Pd(quinone)(triphenylphosphine)₂.     

Studies on the process variables of the condensation reaction of cardanol and formaldehyde by response surface methodology

Different types of cardanol-based novolac-type phenolic resins are produced under a wide range of operating conditions for the application in the resin producing industries. Different operating conditions employed for the production of such resins result in different extent of conversion. In order to understand the system behavior, mathematical relationship between the process variables and the extent of conversion was established by employing the ‘Response surface methodology’. Geometrical representation of the mathematical models in three-dimensional surface plots served as a good aid in understanding the behaviour of reaction under different operating conditions. The maximum extent of conversion of the condensation reaction of cardanol and formaldehyde was found to be 93.0 percent at optimum sets of condition of reaction temperature, time, catalyst concentration and pH of the reaction mixture. All the predicted values for optimum process conditions were in good agreement with experimental data.     

Synthesis of isoamyl laurate and isoamyl stearate in supercritical carbon dioxide

The synthesis of isoamyl laurate and isoamyl stearate was studied in supercritical carbon dioxide with three lipases, Novozym 435, Lipolase 100T, and Candida rugosa. The maximum conversion of 37% and 53%, respectively for isoamyl laurate and isoamyl stearate was obtained when Novozym 435 was used. The effect of various parameters such as molar ratio of alcohol to acid, presence of water, time and temperature was investigated. An optimum temperature of 40–45°C was observed for all reactions. The kinetics of reactions was fast and equilibrium was achieved in 2–3 h. Although the presence of excess alcohol did not reduce conversion, excess water reduced conversion significantly.     

Physicochemical properties and kinetics of transferase activity of invertase

The transferase activity of yeast invertase is found as a function of pH and reaction temperature. The degree of conversion into alkylfructosides depends on the substrate (alcohol) and enzyme concentrations and on the incubation time of the reaction mixture. The effect of ethanol concentration on transferase activity of the enzyme is determined. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 781–784, November–December, 1999.     

Graft copolymerization. II. Grafting of benzyloxyethyl methacrylate on poly(vinyl alcohol)

New graft copolymers were produced by grafting benzyloxyethyl methacrylate, the benzyl ether of HEMA, on high-molecular-weight poly(vinyl alcohol) in dimethyl sulfoxide solution with Ce⁴⁺ as initiator. The effects of the concentration of the initiator, the concentration of the monomer, the total concentration of the reactants, the temperature, and the duration of reaction on the percentages of grafting and conversion were investigated. Further, also the relationships between the initiator concentration and the percentages of grafting and of conversion in the reaction with poly(vinyl alcohol)s of lower molecular weight and of different degrees of hydrolysis were studied.     

Model filled polymers. XI. Synthesis of monodisperse crosslinked polymethacrylonitrile beads

Monodisperse polymethacrylonitrile beads of varied size and crosslink density are prepared by emulsion copolymerization of methacrylonitrile and allylmethacrylate in the absence of emulsifier. The particle size is very sensitive to polymerization temperature and initiator concentration. Because of a nitrile group effect, the maximum conversion varies with reaction conditions. The highest conversion obtained was 82%. © 1992 John Wiley & Sons, Inc.     

The influence of temperature and photoinitiator concentration on photoinitiated polymerization of diacrylate monomer

The behavior of p-methoxybenzoyldiphenylphosphine oxide, previously synthesized, as a photoinitiator for the polymerization of diacrylate monomer, in the presence of 3% (w/w) tertiary amine (triethyl amine) as synergist additive, was studied. The influence of temperature in the range 30–90°C at 3% (w/w) photoinitiator concentration and the influence of the photoinitiator concentration in the range 0.5–3.5% (w/w) at 30°C was investigated by differential scanning photocalorimetry (photo-DSC). In all experiments the photopolymerization was performed at constant light intensity (3 mW cm⁻²). The maximum conversion was obtained at temperature of 90°C at 3% (w/w) photoinitiator concentration and 3% (w/w) triethyl amine. The optimal concentration of photoinitiator to obtain maximum conversion was 3% (w/w), at 30°C. No thermal polymerization occurred at higher temperature.     

MoO3/SiO2催化甘油脱水氢转移还原制备烯丙醇

采用浸渍法制备了MoO3/SiO2催化剂,采用粉末X射线衍射、扫描电子显微镜、氮气吸附-脱附、NH3程序升温脱附及吸附吡啶傅里叶变换红外光谱等手段对催化剂进行了表征,并在固定床反应器中考察了催化剂负载量、反应温度、甘油浓度、空速等条件对MoO3/SiO2催化甘油制备烯丙醇反应性能的影响.结果表明,在MoO3的负载量(质量分数)为1%,330℃、常压、40%(质量分数)甘油水溶液和空速为200 h-1的反应条件下,甘油转化率、烯丙醇选择性及时空收率分别可达92.1%,34.8%和6.0 mmol.g-1.h-1.     

Formation and Conversion of Surface Compounds upon Interaction of Ethanol with Cu/CeO<Subscript>2</Subscript> Catalyst According to in situ IR Spectroscopy

In the conditions of ethanol conversion on the surface of a 5%Cu/CeO₂ catalyst, the method of in situ IR spectroscopy reveals ethoxy groups, acetate and formiate complexes, and consolidation products. Acetaldehyde, acetone, croton aldehyde, butadiene, hydrogen, CO, and CO₂ are observed in the reaction products. As the temperature of the experiment increases, the concentration of acetaldehyde passes through a maximum at T = 250°C. This product is formed due to the interaction of ethoxy and hydroxyl surface groups. The concentration of acetone, croton aldehyde, and butadiene also passes through a maximum in the 350–400°C range. These products are associated with the decomposition of the consolidation products. The concentration of hydrogen, CO and CO₂ steadily increases with temperature and only these reaction products are left at T > 400°C. A mechanism of hydrogen formation based on the conversion of the highest temperature formiate surface complex is discussed.     

THE CHLOROPHYLL-SENSITIZED REACTION BETWEEN BENZOQUINONE AND ETHANOL*

The electron-transfer reaction between triplet excited chlorophyll and quinones has been extensively studied as a model of the primary reaction in photosystem II. There has also been reported a minor reaction in which the chlorophyll cation radical ostensibly oxidizes the alcohol solvent or even water, leading to a gradual net reduction of quinone, but the exact mechanism and even the existence of this reaction has been uncertain. We have examined the consequences of prolonged irradation of ethyl chlorophyllide and benzoquinone in acidulated ethanol, and find a chlorophyllide-sensitized reaction which is not analogous to the better-known autosensitized reduction of quinones in blue or UV light. In the chlorophyllide-sensitized reaction, benzoquinone is apparently converted to ethoxy-substituted quinones and quinols, and polymeric material. Ethyl chlorophyllide (or chlorophyll) is simultaneously oxidized to more polar products which themselves continue to photosensitize the reaction of quinones. The production of acetaldehyde could not be demonstrated in the sensitized reaction. Chlorophyllide-sensitized reaction of (l-hydroxyethyl)benzoquinone, ethoxybenzoquinone and 2.5-diethoxybenzo-quinone were examined for additional information. A reaction sequence, tentatively proposed to accommodate the known facts, starts with oxidative attack by quinone on an oxidized chlorophyllide radical formed by loss of a hydroxyl proton from alcohol bound as a ligand to Mg²⁺. It is not likely that this reaction is closely related to events at the oxidizing side of photosystem II.     

Observation of magnetic field effect on polymer yield in photoinduced dispersion polymerization of styrene

Photoinduced dispersion polymerization of styrene in the presence of dibenzyl ketone as a photoinitiator, with or without magnetic field, has been followed with time. The experiments were carried out at low degrees of conversion of monomer. Since the conditions of the polymerization reaction (viscosity of the medium, reagents concentration, etc.) were approximately unchanged, the results were explained on the basis of a simplified model of dispersion polymerization. The normal growth of the polymerization rates with temperature was registered, and the activation energy of the polymerization was estimated to be about 12 kJ/mol in the temperature range from 20 to 60 °C. The magnetic field effect was best seen at low temperature. The maximum yield of the polymerization product increases by 20% when the magnetic field of 1000 G was applied at the temperature of 20 °C.     

Biocatalytic oxidation of benzyl alcohol to benzaldehyde via hydrogen transfer

Various types of biocatalysts like oxidases, alcohol dehydrogenases, and microbial cells were tested for the oxidation of benzyl alcohol. Oxidases in combination with molecular oxygen led to low conversion. Alcohol dehydrogenases and microbial cells were tested in a hydrogen transfer reaction employing acetaldehyde, chloroacetone, and acetone as hydrogen acceptor. Excellent conversion (95%) could be achieved employing lyophilised cells of Janibacter terrae DSM 13953 at a substrate concentration of 97 mM.     

Synthesis of dypnone by solvent free self condensation of acetophenone over nano-crystalline sulfated zirconia catalyst

Nano-crystalline sulfated zirconia catalyst, prepared by two-step sol–gel method, has been studied for the solvent free self condensation of acetophenone to dypnone. The influence of calcination temperature on the structural, textural and catalytic activity of sulfated zirconia has been analyzed. The surface acidity along with the structural and textural features of the catalyst influenced its activity. The conversion of acetophenone was found to be effected by the variation in the reaction and calcination temperature, however, the dypnone selectivity was not affected much. The catalyst calcined at 650 °C, showed maximum dypnone selectivity of 92% with 68.2% acetophenone conversion at 170 °C after 7 h. The catalyst was reused up to five cycles with marginal decrease in acetophenone conversion, however, without losing its selectivity for dypnone.     

Optimization of alkaline transesterification of soybean oil and castor oil for biodiesel production

This article reports experimental data on the production of fatty acid ethyl esters from refined and degummed soybean oil and castor oil using NaOH as catalyst. The variables investigated were temperature (30–70°C), reaction time (1–3 h), catalyst concentration (0.5–1.5 w/wt%), and oil-to-ethanol molar ratio (1:3–1:9). The effects of process variables on the reaction conversion as well as the optimum experimental conditions are presented. The results show that conversions >95% were achieved for all systems investigated. In general, an increase in reaction temperature, reaction time, and in oil-to-ethanol molar ratio led to an enhancement in reaction conversion, whereas an opposite trend was verified with respect to catalyst concentration.     

Optimization of enzymatic production of biodiesel from castor oil in organic solvent medium

We studied the production of fatty acid ethyl esters from castor oil using n-hexane as solvent and two commercial lipases, Novozym 435 and Lipozyme IM, as catalysts. For this purpose, a Taguchi experimental design was adopted considering the following variables: temperature (35–65°C), water (0–10 wt/wt%), and enzyme (5–20 wt/wt%) concentrations and oil-to-ethanol molar ratio (1∶3 to 1∶10). An empirical model was then built so as to assess the main and cross-variable effects on the reaction conversion and also to maximize biodiesel production for each enzyme. For the system containing Novozym 435 as tatalyst the maximum conversion obtained was 81.4% at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶10. When the catalyst was Lipozyme IM, a conversion as high as 98% was obtained at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶3.     

Optimization of the process variables for the synthesis of cardanol-based novolac-type phenolic resin using response surface methodology

Models capable of predicting the maximum extent of conversion (p) of cardanol-based novolac-type phenolic resin, have been developed using response surface methodology to determine the optimum reaction conditions. Three-dimensional response surface and their contour plot were drawn. The maximum extent of conversion (98.93%) was predicted when the cardanol was condensed with formaldehyde (molar ratio 1:0.652) at 119.84 °C for a time period of 3 h with the catalyst (e.g., citric acid) concentration of 1.988% of total volume of cardanol and formaldehyde. The pH of the reaction mixture was maintained at 3.0. These predicted values for optimum process conditions were in good agreement with experimental data.     

Acceleration of the cationic polymerization of an epoxy with hexanediol

Thin films of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexane carboxylate were UV irradiated (1.1 J cm^-2) under isothermal conditions ranging from 0 to 50°C. Under these conditions the polymerization advanced quickly but only to a conversion level of less than 10% before the reaction rate slowed by more than an order of magnitude. This drop off in rate was not caused by the glass transition temperature, T _g, reaching or exceeding the reaction temperature, T _rxn, since the epoxide's T _g remained at least 40°C below T _rxn. Raising the sample temperature above 60°C caused a sharp increase in the conversion level. At 100°C conversion exceeds 80% and the ultimate T _g approaches 190°C. The addition of 10 mass% 1,6-hexanediol, HD, to the epoxy caused the conversion at room temperature to quintuple over the level obtained without the alcohol present. The heat liberated from this alcohol epoxy blend during cure on a UV conveyor belt system caused the sample's temperature to increase by about 100°C above ambient whereas the epoxy alone under these conditions only experienced a modest temperature rise of about 26°C. If the amount of HD in the blend is increased above 10% the heat of reaction at 23°C decreases due to HD being trapped in a nonreactive crystalline phase. Boosting reaction temperatures above 50°C melts the HD crystals and yields significantly improved conversion ratios. As the level of alcohol blended with the epoxy is raised its ultimate T _g is lowered and when the concentration of alcohol in the blend nears 30 mass%T _g drops below room temperature. This revised version was published online in July 2006 with corrections to the Cover Date.