Microwave-assisted synthesis of ethyl laurate using immobilized lipase: Optimization,mechanism and thermodynamic studies

Microwave-assisted synthesis of ethyl laurate using lauric acid and ethanol catalyzed by Fermase CALB has been investigated. The effect of operating parameters like molar ratio (lauric acid: ethanol), enzyme loading, temperature, and molecular sieves was systematically studied. A maximum conversion of 98.2% was obtained in 10 ​min compared to the conventional method, where the reaction required 4 ​h to achieve 92.4% conversion. The optimum parameters for the microwave-assisted synthesis were 1:2 ​M ratio of lauric acid to ethanol, 45 ​°C temperature, 1.8% (w/w) enzyme amount, 1.5% (w/w) molecular sieves. The enzyme lipase was reused for up to seven successive cycles under microwave irradiation. The thermodynamic study was carried out to determine various thermodynamic parameters for the reaction. The esterification mechanism was proposed, and the impact of microwave irradiation on the immobilized enzyme after several reuse was studied by scanning electron microscopy.     

Process intensification for synthesis of triglycerides of capric acid using green approaches

The present research focuses on intensified synthesis of tricaprin by esterification reaction between capric acid and glycerol catalysed by dry amberlyst-15 using ultrasonication approach. Effect of several reaction conditions like molar ratio, reaction temperature, and amberlyst-15 loading on the rate of conversion has been studied. Effect of ultrasonic conditions like duty cycle and irradiation time on the intensified synthesis is investigated. Recyclability of amberlyst-15 is studied to make process more economical. It is investigated that the optimum reaction conditions which gave maximum conversion of 95% were molar ratio of capric acid: glycerol as 3:5, reaction temperature 90 ​°C, 4% amberlyst −15 loading. It was further investigated that ultrasonic conditions which gave intensified synthesis were 70% duty cycle and irradiation time of 120 ​min. The ultrasonic assisted process was compared with conventional synthesis. Conventional synthesis gave 30% yield in 120 ​min and 82% in 18 ​h. Amberlyst-15 was successfully reused for 13 cycle without any change in the conversion (%) of reaction.     

Kinetics of Enzymatic Synthesis of Cinnamyl Butyrate by Immobilized Lipase

This work illustrates the enzymatic synthesis of cinnamyl butyrate by esterification of butyric acid and cinnamyl alcohol. Experiments were performed to study the various operating parameters such as molar ratio, enzyme concentration, temperature, and speed of agitation. Also, the suitable kinetic model for esterification reaction was predicted and the various kinetic parameters were determined. It has been observed that the experimental results agree well with the simulated results obtained by following the ping-pong bi-bi mechanism with dead-end inhibition by both the substrate acid and alcohol. The highest 90% conversion of butyric acid was observed after 12 h at the following reaction conditions: substrate molar ratio 1:2 (butyric acid/cinnamyl alcohol), temperature 50 °C, enzyme loading 2% (with respect to the weight of the substrates), and agitation speed 250 rpm. Diffusional mass transfer limitations between substrate and enzyme surface do not show significant effect on reaction kinetics. Enzyme reusability study reveals that it retains 85% of its catalytic activity after five consecutive cycles.     

Kinetics,mass transfer,and thermodynamic and statistical modeling study for esterification of valeric acid with n‐butanol: Homogeneous and heterogeneous catalysis

The esterification of valeric acid with n‐butanol was studied with homogeneous and heterogeneous catalysts. The activity and performance of homogeneous p‐toluenesulfonic acid and heterogeneous cation exchange resin catalysts Amberlyst 36, Indion 190, and Amberlite IRC‐50 were evaluated. The pseudo‐homogeneous kinetic model was used to investigate the kinetic parameters of homogeneous‐ and heterogeneous‐catalyzed esterification. The UNIFAC (universal functional activity coefficient) approach was used to study the nonideality of the esterification reaction. The reaction was statistically modeled and optimized by the application of response surface methodology. The effects of independent variables such as reaction temperature, initial molar ratio, and catalyst loading on the conversion of valeric acid were investigated. The optimized conditions for the esterification reaction catalyzed by Amberlyst‐36 were found as temperature 360.4 K, initial molar ratio 3.8, and catalyst loading 6.7 wt%. The predicted conversion (89%) at these optimized conditions is in good agreement with the experimental conversion (87.3 ± 1.6%).     

Enzymatic synthesis of medium chain monoglycerides in a solvent-free system

The synthesis of monocaprin, monolaurin, and monomyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase with the organic reactants (glycerol and fatty acids) in a 20-mL batch reactor with constant stirring. The effects of temperature, fatty acid/glycerol molar ratio, and enzyme concentration on the reaction conversion were determined. The addition of molecular sieves in the assays of monomyristin synthesis was also evaluated. The reactions were carried out for 5 to 6 h and the nonpolar phase was analyzed by gas chromatography. The best results in terms of selectivity and conversion (defined as the percentage of fatty acid consumed) were achieved when the stoichiometric amount of reagents (molar ratio=1) and 9% (w/w) commercial enzyme were used and the reaction was performed at 60°C. The addition of molecular sieves did not improve the synthesis of monomyristin. Conversions as high as 80%, with monoglycerides being the major products, were attained. After 5 h of reaction, the concentration of monoglyceride was about twice that of diglyceride, and only trace amounts of triglyceride were found. The results illustrate the technical possibility of producing medium chain monoglycerides in a solvent-free medium using a simple batch reactor.     

Enzymatic synthesis of sorbitan methacrylate according to acyl donors

Recently, sugar polymers have been considered for use as biomaterials in medical applications. These biomaterials are already used extensively in burn dressings, artificial membranes, and contact lenses. In this study, we investigated the optimum conditions under which the enzymatic synthesis of sorbitan methacrylate can be affected using Novozym 435 in t-butanol from sorbitan and several acyl donors (ethyl methacrylate, methyl methacrylate, and vinyl methacrylate). The enzymatic synthesis of sorbitan methacrylate, catalyzed by Novozym 435 in t-butanol, reached an approx 68% conversion yield at 50 g/L of 1,4-sorbitan, 5% (w/v) of enzyme content, and a 1∶5 molar ratio of sorbitan to ethyl methacrylate, with a reaction time of 36 h. Using methyl methacrylate as the acyl donor, we achieved a conversion yield of approx 78% at 50 g/L of 1,4-sorbitan, 7% (w/v) of enzyme content, at a 1∶5 molar ratio, with a reaction time of 36 h. Sorbitan methacrylate synthesis using vinyl methacrylate as the acyl donor was expected to result in a superior conversion yield at 3% (w/v) of enzyme content, and at a molar ratio greater than 1∶2.5. Higher molar ratios of acyl donor resulted in more rapid conversion rates. Vinyl methacrylate can be applied to obtain higher yields than are realized when using ethyl methacrylate or methyl methacrylate as acyl donors in esterification reactions catalyzed by Novozym 435 in organic solvents. Enzyme recycling resulted in a drastic reduction in conversion yields.     

Partitioning of lactate dehydrogenase from bovine heart crude extract by polyethylene glycol-citrate aqueous two-phase systems

Aqueous two-phase systems (ATPS) composed of polyethylene glycol (PEG)-citrate have been used for enzyme partitioning studies. The behavior of lactate dehydrogenase (LDH) from bovine heart crude extract was analyzed using a two-level factorial design in which the PEG molar mass and concentration, the citrate concentration were selected as independent variables, while the purification factor, the partition coefficient (K) and the activity yield were selected as responses. The statistical analysis revealed the effect of PEG molar mass on K. LDH exhibited a better partitioning toward PEG-rich phase and the highest K value (1079.81) was obtained with 42% (w/w) PEG 400 and 7.5% (w/w) citrate concentration. PEG molar mass also influenced the purification factor of the enzyme in the top phase. Possibly these ATPS remove inhibitors present in the extract affording higher enzyme yield.     

Enzymatic synthesis of medium-chain triglycerides in a solvent-free system

The synthesis of tricaprylin, tricaprin, trilaurin, and trimyristin in a solvent-freesystem was conducted by mixing a commercial immobilized lipase (Lipozyme IM 20, Novo Nordisk, Bagsvaerd, Denmark) with the organic reactants (glycerol and fatty acids) in a 20-mL batch reactor with constant stirring. In a first set of experiments, the effect of water concentration (0–6%) on the reaction conversion was shown to be negligible. In a second set of experiments, the effects of temperature (70–90°C), fatty acid/glycerol molar ratio (1–5), and enzyme concentration (1–9%[w/w]) on the reaction conversion were determined by the application of a 3×3 experimental design. The reactions were carried out for 26 h and the nonpolar phase was analyzed by gas chromatography (GC). Appreciable levels of medium-chain triglycerides were achieved, except for tricaprylin. For the triglyceride production, higher selectivity was attained under the following conditions: molar ratio of 5, enzyme concentration of 5 or 9% (w/w) and temperatures of 70°C (Tricaprin), 80°C (trilaurin), and 90°C (trimyristin). Statistical analysis indicated that the fatty acid/glycerol molar ratio was the most significant variable affecting the synthesis of triglycerides.     

Ultrasound-assisted synthesis of ethyl hexanoate using heterogeneous catalyst: Optimization using Box-Behnken design

Ultrasound-assisted synthesis of ethyl hexanoate was studied in a solvent-free system using Amberlyst-15 as a heterogeneous catalyst. The effect of reaction parameters was evaluated by employing Box Behnken Design. Maximum conversion was obtained as 83.9% experimentally with operating temperature 60 °C, ethanol to hexanoic acid molar ratio as 3, 60% duty cycle, 11% catalyst loading, 10% molecular sieves, and 80 W input power which were optimized through one parameter at a time. The optimal conditions for maximum 86.66% conversion obtained by Box Behnken Design operated in Response Surface Methodology were 62.8 °C temperature, 3.31 ethanol to hexanoic acid molar ratio, and 51.58% duty cycle. The absence of external mass transfer resistances was proved by evaluating Mear's criterion. Thiele modulus and effectiveness factor were determined to study the influence of internal mass transfer resistance qualitatively. The kinetics of the heterogeneous reaction was modeled using Langmuir-Hinshelwood model. The activation energy was calculated as 24.61 kJ/mol.     

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.     

二乙二醇丙酸甲酯的合成与结构表征

采用二乙二醇和丙酸甲酯为主要原料,以钾为催化剂,在通N_2气保护的条件下合成二乙二醇丙酸甲酯,用离子排阻高效液相色谱法对合成的二乙二醇丙酸甲酯进行定量分析。最佳合成条件:二乙二醇与丙酸甲酯的物质的量比为1∶2,催化剂的质量为反应物二乙二醇质量的1.5%,于25℃条件下反应24 h,产物经硅胶柱分离、乙酸乙酯梯度洗脱,然后干燥,制得二乙二醇丙酸甲酯成品,收率为61.5%,纯度达99.5%。用FT-IR,~1H–NMR,GC–MS法对二乙二醇丙酸甲酯的分子结构进行了确证。     

Study on the Synthetic Technology of Polyethylene Glycol's Gemini Surfactant and Its Suspension Properties

Sodium α‐sulfonated polyethylene glycol (400) stearate was synthesized by the reaction of stearic acid with polyethylene glycol using phosphoric acid and p‐Toluene sulfonic acid as catalysts, following by sulfonation with chlorosulfonic acid and neutralization. Effects of single factors such as temperature, time, material ratio on the esterification ratios were investigated. On this basis, employing the orthogonal design, the optimum synthetic conditions were studied. Experiment results: Stearic acid and polyethylene glycol reacted for 4 hours at 140–150°C with the mole ratio 2.5:1.0 with 2.0% catalyst to give the product in 83% yield. Chlorosulfonic acid and Stearate reacted for 1 hour at 60–70°C with mole ratio 2.4:1.0 to give the product in 96% yield. Total yield was 79.7%. Gemini surfactants demonstrated good suspension ability and cooperative effect of mixed system. Compared to conventional surfactants, Gemini surfactants have prior performance attributed to few change in suspension ratios at high temperature and in rate of viscosity change in impact experiments.     

Fatty acid methyl ester production from acid oil using silica sulfuric acid: Process optimization and reaction kinetics

Conversion of high free fatty acids (FFA) containing acid oil (AO) to fatty acid methyl esters (FAME) using silica sulfuric acid (SSA) as a solid acid catalyst was investigated. Process parameters such as reaction temperature, reaction time, catalyst loading, and methanol to oil molar ratio were optimized using the Taguchi orthogonal array method. Maximum FFA conversion (97.16 %) was achieved under the optimal set of parameter values viz. 70°C, 4 mass % catalyst loading, and 1: 15 oil to methanol molar ratio after 90 min. SSA was reused three times successfully without a significant loss in activity. Biodiesel produced from AO met the international biodiesel standards. Determination of kinetic parameters proved that the experimental results fit the pseudo first order kinetic law.     

离子液体中聚乙二醇维生素E琥珀酸酯的合成

以离子液体为催化剂,由维生素E经两步酯化反应合成了聚乙二醇1000(PEG1000)维生素E琥珀酸酯。以离子液体1-(N',N'-二甲胺乙基)-3-甲基咪唑四氟硼酸盐为催化剂、1,2-二氯乙烷为助溶剂、维生素E与琥珀酸酐摩尔比为1:1.2,在80 ℃条件下反应4 h,维生素E琥珀酸酯(TAS)的产率为90%。以1-丙磺酸基-3-甲基咪唑硫酸氢盐/甲苯为反应体系,TAS与PEG1000摩尔比为1:2,在100 ℃下反应5 h,PEG1000维生素E琥珀酸酯(TPGS)收率为91%。     

Enhanced Enzymatic Synthesis of a Cephalosporin,Cefadroclor, in the Presence of Organic Co-solvents

In this study, we investigated the enzymatic synthesis of a semi-synthetic cephalosporin, cefadroclor, from 7-aminodesacetoxymethyl-3-chlorocephalosporanic acid (7-ACCA) and p-OH-phenylglycine methyl ester (D-HPGM) using immobilized penicillin G acylase (IPA) in organic co-solvents. Ethylene glycol (EG) was employed as a component of the reaction mixture to improve the yield of cefadroclor. EG was found to increase the yield of cefadroclor by 15–45%. An investigation of altered reaction parameters including type and concentration of organic solvents, pH of reaction media, reaction temperature, molar ratio of substrates, enzyme loading, and IPA recycling was carried out in the buffer mixture. The best result was a 76.5% conversion of 7-ACCA, which was obtained from the reaction containing 20% EG (v/v), D-HPGM to 7-ACCA molar ratio of 4:1 and pH 6.2, catalyzed by 16 IU mL^?1 IPA at 20 °C for 10 h. Under the optimum conditions, no significant loss of IPA activity was found after seven repeated reaction cycles. In addition, cefadroclor exhibited strong inhibitory activity against yeast, Bacillus subtilis NX-2, and Escherichia coli and weaker activity against Staphylococcus aureus and Pseudomonas aeruginosa. Cefadroclor is a potential antibiotic with activity against common pathogenic microorganisms.     

Process development for production of medium chain triglycerides using immobilized lipase in a solvent-free system

The synthesis of tricaprylin, tricaprin, trilaurin, and trimyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase with the organic reagents (glycerol and fatty acid) in a 20-mL batch reactor with constant stirring. The effects of temperature, fatty acid/glycerol molar ratio, and enzyme concentration on the reaction conversion were determined. The reactions were carried out for 26 h and the nonpolar phase was analyzed by gas chromatography. Appreciable levels of medium chain triglycerides were achieved, except for tricaprylin. The higher selectivity values for the production of triglycerides were attained under the following conditions: a fatty acid/glycerol molar ratio of 5; enzyme concentration of 5 or 9% (w/w); and temperatures of 70°C (tricaprin), 80°C (trilaurin), and 90°C (trimyristin). After completion of the esterification reaction under these conditions, the recovery of the triglyceride and fatty acids, and the reusability of the enzyme were studied. The unreacted fatty acid and the produced triglyceride were satisfactorily recovered. The commercial immobilized lipase was used in 10 consecutive batch reactions at 80°C, with 100% selectivity in the trilaurin and trimyristin synthesis. The possibility of enzyme reuse and the recovery of residual fatty acid are relevant results that contribute to increasing the viability of the process.     

PVP-PdCl2-CuCl2/SiO2-PEG600催化芳氯化物水相脱氯研究

PVP(聚乙烯吡咯烷酮)负载双金属催化剂催化芳香氯化物脱氯已有报道[1～3];利用双金属的协同作用,可以大大提高催化剂的脱氯活性和选择性[4]. 但是,这些研究多是在有机相中进行的,催化剂在水相中则会降低甚至失去活性,且难以回收和重复利用. 然而,难溶于水的有毒芳香氯化物,常存在于工业或生活排放的废水中. 由于治理环境的需要,研究芳香氯化物催化水相脱氯,则是极具挑战性的课题. 本文把起相转移作用的聚乙二醇(PEG)键合到硅胶上作为固相载体,制成双负载双金属水相脱氯催化剂PVP-PdCl2-CuCl2/SiO2-PEG600,成功地用于难溶于水的芳香氯化物的水相脱氯. 研究结果表明,这种催化剂对于芳香氯化物有良好的催化脱氯性能,使用中便于分离并能重复利用. 同时,用IR,TEM和XPS等手段对催化剂进行了表征,探讨了催化剂中各组分在催化脱氯中的作用.     

Kinetics of ultrasound‐assisted esterification of maleic acid and butanol using heterogeneous catalyst

The present research investigates the kinetics of ultrasound‐assisted synthesis of dibutyl maleate using a heterogeneous catalyst (Amberlyst‐15) in solvent‐free system. Reaction parameters were optimized based on conversion by varying the various parameters such as n‐butanol to maleic acid mole ratio, temperature, molecular sieves, catalyst loading, power, and duty cycle. Optimization of parameters resulted in 56.2% yield at 343 K, alcohol to acid mole ratio as 4:1, catalyst loading of 4%, molecular sieves of 4% with an ultrasound power input of 100 W with 60% duty cycle and 22 kHz frequency. In the presence of ultrasound, the reaction time reduced to 120 min in comparison with 240 min of the conventional process. The experimental kinetic data were correlated using Pseudo‐Homogeneous model as well as heterogeneous models like Eley‐Rideal model and Langmuir‐Hinshelwood‐Hougen‐Watson (LHHW) model based on single as well as dual‐site mechanisms. LHHW (reactants and products) model was found to be the best fit. The results proved that the reaction follows second‐order kinetics. The activation energy of the reaction was calculated as 14.64 kJ/mol.     

Polymer-Supported Poly(Ethylene Glycol) as a Phase-Transfer Catalyst for Cross-Aldol Condensation of Isobutyroaldehyde and Formaldehyde

Immobilized poly(ethylene glycol) (PEG 600-PS) was used as an effective phase-transfer catalyst for the synthesis of hydroxypivaldehyde from isobutyraldehyde (IBA) and formaldehyde in the presence of an inorganic base. Studies on the influence of the parameters on the course of the reaction in a batch reactor showed that the use of the PEG 600-PS catalyst allowed one to obtain HPA with high efficiency (IBA conversion >96%, selectivity >98%) in a relatively short time and under mild conditions (2 h, 40 °C). The developed method enables easy separation of the post-reaction mixture by simple phase separation, and the immobilized catalyst can be separated by filtration and then used five times without a loss in its activity. The high activity and stability of the catalyst was also confirmed in a test carried out in a flow reactor.     

Enzyme immobilization to ultra‐fine cellulose fibers via amphiphilic polyethylene glycol spacers

Ultra‐high specific surface cellulose fibers with an average diameter of 500 nm were generated from electrospinning and alkaline hydrolysis of cellulose acetate and used as porous supports for enzyme immobilization. The cellulose fiber surfaces were reacted with polyethylene glycol (PEG) diacylchloride to simultaneously add amphiphilic spacers and reactive end groups for coupling with a lipase enzyme. The quantity of reactive carboxylic acid on the fiber surfaces could be readily controlled by COCl/OH molar ratios and PEG lengths. The highest free acid (COOH) content of 1.0 mmol per gram of cellulose was obtained at 10 COCl/OH ratio with the 600‐Da PEG diacylchloride. Enzyme coupling on such PEG‐attached cellulose was optimal in the presence of a water‐soluble carbodiimide [1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC)] at a very low EDC/COOH molar ratio of 0.2 under acidic condition and at ambient temperature. Whereas the free lipase retained only 25% of its original activity, the fiber‐bound lipase possessed much superior retention of catalytic activity after exposure to cyclohexane (81%) and toluene (62%) and hexane (34%). The fiber‐bound lipase also exhibited significantly higher catalytic activity at elevated temperatures than the free form, that is, 10 times at 70 °C. The ultra‐fine, fibrous, and porous structures were retained throughout alkaline hydrolysis, activation, coupling, and activity assays. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4289–4299, 2004