Esterification Reaction Rate Research Articles

Effect of recycle and feeding method on batch reactive recovery system of lactic acid

Reactive batch distillation coupling esterification and hydrolysis was studied for the recovery of lactic acid. The analysis of the dynamic behavior of the system showed drastic change of esterification reaction rate in the reboiler due to the difference of volatility and component boilup rate of each species. Methanol recycle and feeding method were investigated as the factors which could control the compoent boilup rate of each species and rate of esterification reaction. The flow rate and composistion of methanol recycle stream was controlled by the temperature of the partial condenser. A temperature slightly higher than the methanol boiling point is optimum as the temperature of the partial condenser. When the temperature of the partial condenser was increased in the initial part of whole batch time and decreased in the latter part, the performance of the system was enhanced, compared with when the partial condenser temperature remained constant. Semibatch operation was compared with batch operation. Continuous feeding of methanol enhanced the recovery system performance while continuous feeding of lactic acid aqueous solution deteriorated, compared with batch operation.

Unprecedented Acceleration Effects of Water on Acid-Catalyzed Reactions Over Molybdena-Zirconia Catalysts

Effects of water on various acid-catalyzed reactions have been studied mainly using MoO3/ZrO2. While the reaction rate of gas-phase esterification of acetic acid with ethanol and the dehydration of 2-butanol over SiO2-Al2O3 decreased significantly by the addition of water vapor in the feed gas, these reactions over MoO3/ZrO2 were found to be greatly enhanced by the presence of water. The enhancement by water was reversible and was remarkable when MoO3/ZrO2 was calcined at a temperature range of 773-1073 K. IR spectroscopy of H2O adsorbed on MoO3/ZrO2 suggests that the acceleration effect of water would be due to the generation of acidic sites from water coordinated to Mo species on the surface of MoO3/ZrO2.

STUDY OF FACTORS INFLUENCING PROTEIN ESTERIFICATION USING ?-LACTOGLOBULIN AS A MODEL

β-Lactoglobulin was esterified with different alcohols (methanol, ethanol, n-propanol and iso-propanol) over various conditions of acidity, protein concentration, water content, time and temperature. The resulting products were simply recovered by centrifugation of the reaction mixture at the end of the reaction. Yield of esterification was markedly dependent on the concentration of the acid, of the protein, the water content and the type of alcohol used. Using ethanol and propanol required 5 and 10% water, respectively to reach a maximum esterification degree. Concentrations of acid and protein were the crucial parameters. Protein concentration (4 or 5%) together with an adequate H + /COOH molar ratio, not only enhance the yield of esterification with ethanol but also increase the rate of this reaction. The results may be applicable to choosing the reaction conditions for the preparation of other esterified proteins. The conditions described in this study increase esterification reaction rate compared to that under conditions used traditionally.

Protein extraction using sugar ester reverse micelles

In protein extraction, using the nonionic surfactant sugar ester DK-F-110, the critical micelle concentration (CMC) of a DK-F-110/isopropyl alcohol(IPA)/hexane system was found to be at a DK-F-110 concentration of 0.5 g dm -3 , indicating that the sugar ester reverse micelles could be formed in hexane. At concentrations higher than the CMC, cytochrome c was extracted into the DK-F-110 reverse micelles as judged from UV spectra of the DK-F-110/IPA/hexane solution after it was contacted with the aqueous protein solution. In extraction of cytochrome c using this system, forward extraction was found to be pH-dependent, with high extraction percentage being obtained at pH 8. The forward extraction percentage was reduced by an increase in the buffer concentration, and at a buffer concentration of 0.5 mol dm -3 was ca 25% as high as that of sodium bis(2-ethylhexyl) sulfosuccinate(AOT) systems. An optimal DK-F-110 concentration was found to give the maximum forward extraction percentage. Addition of alcohol, especially IPA, to the micellar organic phase enabled the highly backward extraction of cytochrome c to be achieved without the formation of insoluble aggregates. The esterification reaction rate by Rhizopus delemar lipase in the DK-F-110 reverse micellar system had a higher maximum value than that of AOT and lecithin systems.

Phase and reaction equilibria of the acetic acid-isopropanol-isopropyl acetate-water system at 760 mmHg

An energy-saving process, the so-called reactive distillation process, is attracting more and more attention in the chemical industry. This process is based on the simultaneous implementation of chemical reaction and phase equilibria in a process unit. The esterification of acetic acid and isopropyl alcohol is one of the processes that use this technology. In order to understand the thermodynamic behavior of this mixture and its reaction products, isopropyl acetate and water, the vapor-liquid equilibrium (VLE) was measured directly with the chemical reaction considered. The esterification reaction rate of acetic acid and isopropanol mixture is very slow. In this study, para-toluenesulfonic acid was selected as the catalyst to accelerate the chemical reaction. This results in the reaction reaching equilibrium before phase equilibrium so that this complicated problem can be simplified and readily solved. The equilibrium compositions of this mixture at different temperatures were measured. The reaction equilibrium constants were calculated with the collected experimental data and the equations of reaction and phase equilibria. It was found that the reaction equilibrium constant was slightly dependent on temperature. The measured VLE data were correlated by the activity coefficient models of UNIQUAC and Wilson with consideration of the association of acetic acid in the vapor phase. The calculated results show that the correlation was successful as compared with experimental data.

Effect of Different Supports on the Reaction Rate of Rhizomucor Miehei Lipase in Organic Media

Five different aluminas, a silica and a zirconia support were used to adsorb lipase (E.C. 3.1.1.3) from Rhizomucor miehei. The activity of the immobilised lipase was measured by esterification of dodecanol and decanoic acid in hexane. The immobilised lipase and the organic phase were pre-equilibrated separately to known water activities before mixing them to commence the reactions. The aluminas, which varied in pore sizes and surface areas, adsorbed similar amounts of enzyme. However, the esterification activities varied about 10-fold, increasing with increasing surface area. The silica and zirconia supports adsorbed about half as much lipase as the aluminas. The esterification reaction rates per unit quantity of enzyme adsorbed were compared with those for aluminas with similar surface areas; this specific rate was about 2 times higher for the zirconia, but the difference with silica was only small. There was no clear correlation between the esterification rates at fixed water activity and the amount of ...

Studies on kinetics and preparation of C36 dimer acid esters

AbstractC36 Dimer acids were esterified with various short‐chain alcohols, namely 2‐propanol, n‐butanol, n‐hexanol, n‐octanol, 2‐octanol and 2‐ethyl‐1‐hexanol by using sulfuric acid as catalyst and benzene as an azeotropic solvent. Various reaction parameters were standardized. In case of isopropyl esters, acid‐to‐alcohol mole ratio of 1:5 and sulfuric acid concentration of 2% based on the weight of dimer acids were found to be optimum. In case of straight‐chain primary alcohols, namely n‐butanol, n‐hexanol and n‐octanol, 1:2.5 mole ratio of acid to alcohol and 1% by weight of sulfuric acid were found satisfactory. Esterification reaction rates were determined from the fall in acid value of the product. The reaction followed pseudo first order kinetics. The reaction rates increased with the increase in chainlength of straight‐chain primary alcohols from n‐butanol to n‐octanol. The rate of reaction decreased from n‐octanol to 2‐ethyl‐1‐hexanol to 2‐octanol due to the branching of the chain in 2‐ethyl‐1‐hexanol and secondary nature of the −OH group in 2‐octanol.

The control of lipase‐catalysed transesterification and esterification reaction rates

The reaction rate of two lipase-catalysed reactions, esterification and transesterification, were studied in a liquid/solid two-phase system in order to investigate the effect of water partition between the enzyme preparation and the liquid phase composed of only the reactants, i.e. without the conventional solvents. Lipase from Candida cylindracea was used for these studies. The enzyme was inactive in dehydrated systems. In the case of monoester synthesis, the reaction rate increased with increasing water activity. The reaction rates of the non-specific C. cylindracea lipase-catalysed reactions were very sensitive to the nature of the substrates in this unusual system. For instance, the transesterification reaction rate of ethyl propionate was 48 times higher with nonanol than heptanol in the case of dehydrated substrates, but only 2.2 times higher in the case of water-saturated substrates. The results presented here demonstrate the absolute necessity to consider the polarity of every substrate, because of its ability to modify the water partition between the solid phase (enzyme preparation) and the liquid phase (substrate and product), which results in drastic changes in enzyme activity. Contrary to esterification, which is known to be activated by the water produced, the rate of transesterification remained constant at the beginning of the reaction. However, when transesterification and esterification were carried out in the same liquid phase, the transesterification reaction rate was controlled by the water produced by the concomitant esterification. Activation effects of the water molecules produced during the enzymatic reaction were of exactly the same order of magnitude for both reactions.

Catalysis by Polymers. V. Some Kinetic Aspects on the Polymer Catalyzed Reactions of Oxiranes

AbstractThe esterification of epichlorohydrin with acrylic acid in the presence of various macro‐ and micromolecular catalysts has been investigated. The influence of concatenation of the catalytic functional groups on the reaction rate had been studied too.The previous studies1–4 in the field of polymer catalyzed reactions of oxiranes with organic acids have shown some interesting aspects related to the behaviour of catalytic functional groups which are attached to the polymer backbone. The aim of this paper was to study the concatenation effect of the catalytic functional groups both in the homopolymers and copolymers on the reaction rate of esterification; for the same purpose the small‐molecule analogues were used as references.

Study of alkylating reactions catalysed by cation-exchange resins

Summary The possibilities of industrial uses of various cation-exchange resins have been studied in acetic acid esterification reactions. Catalytic activities and life-times of resins have been studied and compared. The oleophilic sulphonated styrene-vinyl benzene polymer has been proven to be the best, its activity being similar to that of sulphuric acid and can be used in 50 esterification cycles without regeneration. It has been observed that stirring increases the rate of esterification reaction, but decreases the lifetime of the resin. The reactions studied have been catalysed by the ion-exchange resin, independently of the structure of alcoholic components. It is advantageous to perform esterification at the boiling point of the mixture in order to evaporate the water produced. To avoid boiling temperatures exceeding 160°C, the addition of certain solvents might be necessary. Applying strong cation-exchange resins, alcohols can be used for aromatic C-alkylation of phenols, but the alkyl group will be isomerised, and an olefin compound beside an aliphatic ether are produced in simultaneous reaction.

Ultrasonic Study of Esterification Equilibria

Ultrasonic absorption has been measured in quaternary systems of ethyl alcohol-acetic acid-ethyl acetate and water mixtures at various compositions, taken to represent different stages of the reaction \begin{aligned} \text{CH$_{3}$COOH}+\text{C$_{2}$H$_{5}$OH}{\rightleftharpoons}\text{CH$_{3}$COOC$_{2}$H$_{5}$}+\text{H$_{2}$O}, \end{aligned} including the ideal post equilibrium stage assuming a complete esterification. Similar studies have been made in methyl alcohol-acetic acid-methyl acetate-water system and ethyl alcohol-butyric acid-ethyl butyrate-water system. It is observed in each case that the absorption coefficient is minimum at the equilibrium composition. Using the absorption coefficient data so obtained the rate of esterification reaction has been computed and it is shown that the equilibrium constant of the reaction can be thus determined.

Effect of Diethylstilbestrol and Cholesterol on the Fatty Acid Metabolism of Cockerels

IN THE chicken, either exogenous cholestrol or diethylstilbestrol administration leads to a significant increase in blood lipids (Lindsay et al., 1946). Diethylstilbestrol, besides, produced a marked fattening action especially in the abdominal adipose tissue (Lorenz, 1945; Herbert and Brunson, 1957). The liver and plasma cholesterol levels increased greatly with an increased cholesterol intake (Raiford and Wong, 1962) and with diethylstilbestrol administration (Entenman et al., 1940). The overall reaction rate of cholesterol esterification in the intestinal mucosa is dependent on the composition of the fatty acid mixture available for esterification (Roels and Hashim, 1962). Furthermore, a large increase in oleic acid content occurred in cockerels made hyperlipemic either by the addition of cholesterol or diethylstilbestrol implantation (Blomstrand and Christensen, 1963). The combined effect of cholesterol and diethylstilbestrol with different types of dietary fats has been little explored.Results from our previous work have shown that the cholesterol content in the hen …