• Journal of Microbiology and Biotechnology
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• v.8 no.2
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• pp.165-170
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• 1998

Lipase-catalyzed esterification of n-butyl oleate was carried out in n-hexane as a model reaction. The optimal activity of Candida rugosa lipase was shown in a water activity ($a_w$) range of 0.52 to 0.65 at $30^{\circ}C$. The water produced from the esterification was removed by a tubular type pervaporation system. The rate of ester formed from the enzymatic esterification was allowed to be the same as the rate of water removal by maintaining an optimal $a_w$ of the reaction system using an on-off dewatering control device. The reaction rate and yield with a$a_w$ control were increased two folds higher than the respective values for the uncontrolled reaction.

• Journal of Life Science
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• v.5 no.4
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• pp.155-161
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• 1995

The effects of substrate concentration, enzyme concentration, reaction temperature, and water content were investigated in intramolecular esterification. This study used cyclohexane as organic solvent, power lipase as enzyme, and benzyl alcohol and octanoic acid as substrate. The initial reaction rate was found to be proportional to enzyme concentration; followed Michaelis-Menten equation for octanoic acid; and was inhibited by benzyl alcohol . The observed initial reaction rate first increased, then decreased with increasing reaction temperature, giving rise to the maximum rate at 20$\circ$. The drop in the reaction rate at higher temperature was to partition equilibrium change of substrate between organic solvent and hydration layer of enzyme molecule in addition to the deactivation by enzyme denaturation. Water layer surrounding enzyme molecule seemed to activate in organic solvent and the realistic reaction was done in the water layer. In the enzymatic reaction in organic solvent, the initial reaction rate was influenced by partition quilibrium of substrate, so the optimum condition of substrate concentration, enzyme concentration, reaction temperature, and water content would give a good design tool.

• Journal of the Korean Applied Science and Technology
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• v.27 no.1
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• pp.6-13
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• 2010

Esterification reaction between succinic acid and 1,4-butanediol was kinetically investigated in the presence of nontoxic organometallic compound catalyst(ESCAT-100E) at $150-190^{\circ}C$. The reaction rates measured by the amount of distilled water from the reaction vessel. The Esterification reaction was carried out under the first order conditions respect to the concentration of reactants, respectively. The overall reaction order was 2nd. The linear relationship was shown between apparent reaction rate constant and reciprocal absolute temperature. By the Arrhenius plot the activation energy have been calculated as 376.13 kJ/mol under nontoxic organometallic compound catalyst and also apparent reaction rate constant, k' was found to obey first kinetics with respect to the concentration of catalyst.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.362-369
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• 2009

Esterification reaction between succinic acid and 1,4-butanediol was kinetically investigated in the presence of monobutyl tinoxide catalysts at $150{\sim}190^{\circ}C$. The reaction rates measured by the amount of distilled water from the reaction vessel. The esterification reaction was carried out under the first order conditions with respect to the concentration of reactants, respectively. The overall reaction order was 2nd. The linear relationship was shown between apparent reaction rate constant and reciprocal absolute temperature. By the Arrhenius plot the activation energy have been calculated as 87.567 kJ/mol under monobutyl tinoxide catalyst and also apparent reaction rate constant, k' was found to obey first kinetics with respect to the concentration of catalyst.

• Journal of Environmental Science International
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• v.13 no.1
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• pp.79-87
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• 2004

Esterification of soybean oil with methanol was investigated. First of all, liquid-liquid equilibriums for systems of soybean oil and methanol were measured at temperatures ranging from 40 to 65$^{\circ}C$. Profiles of conversion of soybean oil with time were determined from the glycerine content in reaction mixtures for the different kinds of catalysts, such as NaOH, CaO, Ca(OH)$_2$, MgO, Mg(OH)$_2$, and Ba(OH)$_2$. The effects of dose of catalyst, cosolvent and reaction temperature on final conversion were examined. Esterification of waste vegetable oil with methanol was investigated and compared to the case of soybean oil. Solubility of methanol in soybean oil was substantially greater than that of soybean oil in methanol. When the esterification reaction of soybean oil was catalyzed by solid catalyst, final conversion was strongly dependent on the alkalinity of the solid catalyst, and increased with the alkalinity of the metal. Hydroxides from the alkali metals were more effective than oxides. When Ca(OH)$_2$ was used for the esterification catalyst, maximum value of final conversion was measured at dose of 4％. When CHCl$_3$ as a cosolvent, was added into the reaction mixture of soybean oil which catalyzed by Ba(OH)$_2$, maximum value of final conversion was appeared at dose of 3％. When waste vegetable oil was catalyzed by NaOH and solid catalysts, high final conversion, over 90％, and fast reaction rate were obtained.

• KSBB Journal
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• v.17 no.6
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• pp.543-548
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• 2002

The enantioselective esterification of racemic ibuprofen catalyzed by a Candida rugosa lipase was studied according to reaction conditions such as a lipase concentration, reaction temperature, alcohol chain length and alcohol concentration. The S-(+)-ibuprofen alkyl esters prepared were converted to S-(+)-ibuprofen by hydrolysis with sulfuric acid as a catalyst. High conversions in the esterifications were obtained at 60$^{\circ}C$ and an equimolar ratio of octanol to ibuprofen. The initial reaction rate of the esterification decreased with increasing octanol concentration. Conversion and initial reaction rate increased with increasing alcohol chain length. Values of enantiomeric excess(ee) according to esterification reaction conditions did not change below 60$^{\circ}C$. On the other hand, values of conversion and ee for the chemical hydrolysis of S-(+)-ibuprofen alkyl esters were independent of alcohol alkyl chain length. Optical resolution of racemic ibuprofen was achieved by lipase catalyzed esterification and chemical hydrolysis. The separation method provided a high yield and enantioselectivity for the production of S-(+)-ibuprofen from racemic ibuprofen.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.6
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• pp.550-557
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• 2005

The multivariate statistical analysis methods, using both multiple linear regression(MLR) and partial least square(PLS), have been applied to predict the reactor properties and the product quality of a direct esterification reactor for polyethylene terephthalate(PET) synthesis. On the basis of the set of data including the flow rate of water vapor, the flow rate of EG vapor, the concentration of acid end groups of a product and other operating conditions such as temperature, pressure, reaction times and feed monomer mole ratio, two multi-variable analysis methods have been applied. Their regression and prediction abilities also have been compared. The prediction results are critically compared with the actual plant data and the other mathematical model based results in reliability. This paper shows that PLS method approach can be used for the reasonably accurate prediction of a product quality of a direct esterification reactor in PET synthesis process.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.72-76
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• 2013

In this study, the boric acid which is a by-product in the esterification process to obtain norbornene diester derivatives was recovered, and then its reusability for esterification of norbornene was investigated. Four types of trialkyl borate (tributyl borate, tripentyl borate, and triisopentyl borate, trihexyl borate) were synthesized through the esterification with boric acid and four types of alcohol. Then, diester derivatives were synthesized by esterification with the synthesized trialkyl borate and norbornene dicarboxylic acid. The conversion of norbornene dicarboxylic acid is 89.50~99.31%. The boric acid which is a by-product in the esterification were recovered with NaCl salt and used for synthesizing trialkyl borate. The recovery rate was 92.43~99.35 %. When the recovered trialkyl borate was used in esterification, there are little losses of the yield. Since boric acid which is a major by-product is able to be recovered, the process is expected to be a clean technology to prevent an environmental pollution by the emission of chemical compounds.

• Elastomers and Composites
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• v.49 no.2
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• pp.110-116
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• 2014

We investigated the effect of the concentration of stannous 2-ethylhexanoate catalyst on the esterification rate between adipic acid (AA) and each of two PEG oligomers, diethylene glycol (DEG) and polyethylene glycol (PEG600). The concentration of the catalyst was varied from 0.15 to 2.0 wt.%. To attach hydroxy group to each end of the poly(oxyethylene-co-adipate) synthesized from AA and the PEGs, the esterification was performed with excessive PEG oligomers ([PEG]/[AA]=2) at $170^{\circ}C$. The degree of polymerization of the poly(oxyethylene-co-adipate)diol products were three. The apparent rate constant ($k_{app}$) of the esterification between AA and DEG shows the first order dependency on the catalyst concentration ($k_{app}=0.88[C_{cat}]$), whereas the $k_{app}$ of the esterification between AA and PEG600 has a relation of $k_{app}=0.123[C_{cat}]^{0.55}$ with the catalyst concentration. It is expected that the rate of esterification between AA and DEG has a non-linear dependency on the catalyst concentration as the catalyst concentration approaches to 0.22M.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.2
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• pp.76-84
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• 2002

On-line conversion estimation of enzymatic esterification reactions in solvent-free media was investigated. In principle, conversion to ester can be determined from the amount of water produced by the reaction, because water is formed as a by-product in a stoichiometric manner. In this study, we estimated the water production rate only from some measurements of relative humidity and water balances without using any analytical methods. In order to test the performance of the on-line conversion estimation, the lipase-catalyzed esterification of n-capric acid and n-decal alcohol in solvent-free media was performed whilst controlling water activity at various values. The reaction conversions estimated on-line were similar to those determined by offline gas chromatographic analysis. However, when the water activity was controlled at higher values, discrepancies between the estimated conversion values and the measured values became significant. The deviation was found to be due to the inaccurate measurement of the water content in the reaction medium during the initial stages of the reaction. Using a digital filter, we were able to improve the accuracy of the on-line conversion estimation method considerably. Despite the simplicity of this method, the on-line estimated conversions were in good agreement with the off-line measured values.