Synthesis of esters: Development of the rate expression for the Dowex 50 Wx8-400 catalyzed esterification of propionic acid with 1-propanol

Synthesis of Isoamyl Fatty Acid Ester, a Flavor Compound, by Immobilized Rhodococcus Cutinase

Isoamyl fatty acid esters (IAFEs) are widely used as fruity flavor compounds in the food industry. In this study, various IAFEs were synthesized from isoamyl alcohol and various fatty acids using a cutinase enzyme (Rcut) derived from Rhodococcus bacteria. Rcut was immobilized on methacrylate divinylbenzene beads and used to synthesize isoamyl acetate, butyrate, hexanoate, octanoate, and decanoate. Among them, Rcut synthesized isoamyl butyrate (IAB) most efficiently. Docking model studies showed that butyric acid was the most suitable substrate in terms of binding energy and distance from the active site serine (Ser114) γ-oxygen. Up to 250 mM of IAB was synthesized by adjusting reaction conditions such as substrate concentration, reaction temperature, and reaction time. When the enzyme reaction was performed by reusing the immobilized enzyme, the enzyme activity was maintained at least six times. These results demonstrate that the immobilized Rcut enzyme can be used in the food industry to synthesize a variety of fruity flavor compounds, including IAB.

Manufacture of n-Propyl Propionate Using Ion Exchange Resins: Reaction Kinetics and Feasibility of Reactive Distillation

Reaction kinetics of esterification of propionic acid with 1-propanol to produce n-propyl propionate using Amberlyst-15 as a catalyst was investigated in this work. Effect of various parameters was studied. Initially, the efficacy of different catalysts was investigated which revealed that Amberlyst-15 can be suitably used for the reaction. This was followed by mass transfer exclusion which included effect of agitation speed, catalyst size and calculation of Weisz-Prater Criterion. Parameters selected for kinetic study were mole ratio of propionic acid to 1-propanol, temperature, catalyst loading and initial water concentration. Catalyst reusability was also verified. Aspen      Custom Modeler (ACM) was used to regress kinetic parameters and a good match was obtained. Reactive Distillation (RD) runs in the batch mode were performed which showed that RD is a better option for process intensification (PI) for this reaction. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Catalytic production and application of bio-renewable butyl butyrate as jet fuel blend- A review

Butyl butyrate (BB) derived from bio-renewable resources is the most promising jet fuel blend. This review highlights essential properties of jet fuel, including calorific value, kinematic viscosity, freezing point, flash point, auto-ignition temperature, and density to compare with different bio-renewable chemicals, which are compatible to be blended with the jet fuel. A detailed discussion follows on the importance of intermediate formation, reaction mechanism, and catalyst properties that are critical towards the production of bio-renewable resource-derived BB. BB is primarily produced via the esterification of butyric acid (BA) in butanol (BuOH) with or without using a catalyst. The corresponding reactions are carried out in both homogeneous and heterogeneous phases, provided it has acidic properties. Thus, a wide range of acidic catalysts such as [HSO₃-pmim] HSO₄ ionic liquids, heteropolyacid, methanesulfonic acid, Dowex 50 Wx8-400 resins, and sulfonated char causes up to 98%, 97.9%, 93.2%, 95.3%, and 90% of BB yield, respectively are critically reviewed. Moreover, reaction mechanism, product, and by-product formation that primarily dictate the BB yield and selectivity have been comprehensively reviewed. In addition, catalytic and mechanistic insights on BB production from other bio-renewable resources such as butyric anhydride, butyraldehyde, dibutyl ether, and methanol have been discussed in this review.

A Glimpse of the World of Volatile Fatty Acids Production and Application: A review

Sustainable provision of chemicals and materials is undoubtedly a defining factor in guaranteeing economic, environmental, and social stability of future societies. Among the most sought-after chemical building blocks are volatile fatty acids (VFAs). VFAs such as acetic, propionic, and butyric acids have numerous industrial applications supporting from food and pharmaceuticals industries to wastewater treatment. The fact that VFAs can be produced synthetically from petrochemical derivatives and also through biological routes, for example, anaerobic digestion of organic mixed waste highlights their provision flexibility and sustainability. In this regard, this review presents a detailed overview of the applications associated with petrochemically and biologically generated VFAs, individually or in mixture, in industrial and laboratory scale, conventional and novel applications.

Esterification of propanoic acid in the presence of a homogeneous catalyst

Esters are organic compounds that are widely used even on an industrial scale, so their production has been extensively investigated. The aim of this work is to carry out the optimization process of esterification of propionic acid with lower monohydric alcohols. The influence of the amount of catalyst (H2SO4), the size and structure of the alcohol, the influence of the a-substituent, the molar acid/alcohol ratio and temperature on the esterification process were investigated. The descending order of reactivity tested alcohol is: 1-butanol> 1-propanol> ethanol> 2-propanol. As the acid/alcohol molar ratio increases, the rate and yield of the esterification reaction increase. The maximum yield of n-propyl propanoate in our experiments was 96.9%, achieved at a molar ratio of propanoic acid/1-propanol/catalyst 1/10/0.20 and a temperature of 65°C for 210 minutes of reaction.

Search for the Microwave Nonthermal Effect in Microwave Chemistry: Synthesis of the Heptyl Butanoate Ester with Microwave Selective Heating of a Sulfonated Activated Carbon Catalyst

The heptyl butanoate ester was synthesized from butanoic acid and heptanol in a heterogeneous medium in the presence of sulfonated activated carbon (AC-SO3H) catalyst particles subjected to microwave irradiation, which led to higher conversion yields (greater product yields) than conventional heating with an oil bath. The advantage of the microwaves appeared only when the moisture content in the butanoic acid batch(es) was high, suggesting that, unlike conventional heating, the reverse reaction caused by the moisture content and/or by the byproduct water was suppressed by the microwaves. This contrasted with the results that were found when carrying out the reaction in a homogeneous medium in the presence of the 2,4,6-trimethylpyridinium-p-toluene sulfonate (TMP-PTS) catalyst, as product yields were not improved by microwave heating relative to conventional heating. The removal of moisture/water content in the reaction solution was more pronounced when the reactor was cooled, as the reaction yields were enhanced via selective heating of the heterogeneous catalyst. A coupled electromagnetic field/heat transfer analysis gave credence to the selective heating of the AC-SO3H catalyst, which was further enhanced by cooling the reactor. It was deduced that unforeseen impurities and local high-temperature fields generated on the surface of small fine catalyst particles may have had an effect on the microwave chemistry such that the associated phenomena could be mistaken as originating from a nonthermal effect of the microwaves. Accordingly, it is highly recommended that impurities and selective heating be taken into consideration when examining and concluding the occurrence of a microwave nonthermal effect.

Marked Difference in the Conformational Transition of DNA Caused by Propanol Isomer

We measured the changes in the higher-order structure of DNA molecules (λ phage DNA, 48 kbp) at different concentrations of 1- and 2-propanol through single-molecular observation. It is known that 2-propanol is usually adapted for the procedure to isolate genomic DNA from living cells/organs in contrast to 1-propanol. In the present study, it was found that with an increasing concentration of 1-propanol, DNA exhibits reentrant conformational transitions from an elongated coil to a folded globule, and then to an unfolded state. On the other hand, with 2-propanol, DNA exhibits monotonous shrinkage into a compact state. Stretching experiments under direct current (DC) electrical potential revealed that single DNA molecules intermediately shrunk by 1- and 2-propanol exhibit intrachain phase segregation, i.e., coexistence of elongated and compact parts. The characteristic effect of 1-propanol causing the reentrant transition is argued in terms of the generation of water-rich nanoclusters.

Structure-Activity Relationships of Cinnamate Ester Analogues as Potent Antiprotozoal Agents

Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model.

Green and Efficient Esterification Method Using Dried Dowex H+/NaI Approach

The usefulness of dried Dowex H+ cation-exchange resin with or without sodium iodide (NaI) as a catalyst system for different kinds of esterifications using carboxylic acids and alcohols as starting materials has been systematically investigated. The Dowex H+/NaI approach is very effective, generally high yielding, energy-efficient, and nontoxic, and the Dowex H+ resin is reusable. Since the whole procedure from start to product isolation is also very simple, these features make the method environmentally friendly. The method is regioselective, and its potential for separation of valuable carboxylic acids like resin acids from mixtures containing other kinds of carboxylic acids has been demonstrated. Examples for green and straightforward esterification of highly important natural amino acids are also presented.

Kinetics Study and Parametric Sensitivity Analysis of Esterification of Butyric Acid with Benzyl Alcohol: A Taguchi Methodology Approach

The liquid phase esterification of butyric acid with benzyl alcohol was studied using homogenous catalyst p-toluenesulfonic acid. The reversible second order rate equation was used to investigate the kinetic parameters of the reaction. The L9 orthogonal array of Taguchi methodology was employed to study the parametric effect independent variables on the responses equilibrium constant (Keq) and conversion (Xeq) of butyric acid. The parameters and their range such as catalyst concentration (0.5–1.5 wt%), temperature (333–363 K) and molar ratio (1–3) was used and considered as independent parameters for parametric sensitivity analysis. Non-ideal behavior of the reaction was studied using UNIFAC group contribution method. The effect of reaction temperature on the overall activity factor was studied. The relative parametric effect on the Keq and Xeq was found. In sensitivity analysis, temperature and molar ratio was the most influencing parameter on the Keq and Xeq. The regression model was developed and validate by performing unknown experiments.

Response Surface Optimization and Kinetics of Isopropyl Palmitate Synthesis using Homogeneous Acid Catalyst

Fatty acid esters (FAE) are widely applied in the field of cosmetics, personal care products and various other allied applications. This work describes the synthesis of isopropyl palmitate (FAE) by esterification of palmitic acid with isopropyl alcohol catalyzed by p-toluene sulfonic acid (p-TSA) in a batch reactor. Response surface methodology (RSM) with Box-Behnken experimental design (BBD) was employed to design the experiments as well as to optimize the conversion of palmitic acid. The effects of various process parameters namely catalyst amount, molar ratio of alcohol to acid and reaction temperature on conversion of palmitic acid were evaluated. The high correlation coefficient (R2=0.973) between model and experimental data indicated that the data fitted well in the model. The optimal process conditions were found to be, catalyst amount of 5 % (wt/wt), molar ratio of alcohol to acid of 7:1 and temperature of 82 °C. Moreover, the kinetic model was developed at these optimized process conditions using second order kinetics and validated with experimental results. The kinetic model and experimental results were found to be in good agreement. The kinetic rate constants and equilibrium constant increased with increase in temperature. The activation energy and pre-exponential factor were found to be 45.21 kJ mol−1 and 1.96×105 L mol−1 h−1 respectively. The optimized process parameters obtained from RSM, equilibrium rate constants and the parameters evaluated from kinetic model may be useful for the simulation of pervaporation reactor and reactive distillation column for the synthesis of isopropyl palmitate.

Experimental and Kinetic Study of Esterification of Acrylic Acid with Ethanol Using Homogeneous Catalyst

Esterification of acrylic acid with ethanol, catalyzed by sulfuric acid has been carried out in stirred batch reactor under atmospheric pressure. Different parameters such as effect of initial molar ratios of the reactants, effect of catalyst concentration, initial water and effect of temperature has been studied in the batch reactor. Different catalyst loading system (1–3 vol%), reaction temperatures (50–70 °C), initial reactants molar ratio (1:1–1:3) and water concentration in feed (0–20 vol%) was used in the reaction system. The temperature dependence is exponential and expressed by Arrhenius type of relationship. Kinetics parameters such as equilibrium constant, rate constants, activation energy and reaction enthalpy and entropy were estimated by experimental data. The rate equation has a remarkable fit to the data and was able to describe the behavior of the system at various reaction temperatures. Hydrochloric acid (HCl) and hydro iodic acid (HI) were also compared with sulphuric acid as catalyst for esterification of acrylic acid with ethanol. Sulphuric acid was found to be more efficient catalyst for esterification as it induces the maximum conversion of acrylic acid.

Kinetics of esterification of acetic acid and methanol using Amberlyst 36 cation-exchange resin solid catalyst

Catalytic esterification of acetic acid with methanol to produce methyl acetate in a stirred batch reactor was investigated in the presence of Amberlyst 16, Indion 180 and Amberlyst 36 catalysts. Amberlyst 36 was found to be an effective solid catalyst for this reaction compared to the other solid catalysts. The reaction was performed in the temperature range of 323.15–353.15 K and the catalyst loading in the range of 0.01–0.05 g cm−3. The initial reactant feed molar ratios of acetic acid to methanol were varied from 1:1 to 1:4. The influence of different parameters like temperature, catalyst loading, magnetic stirrer speed and average catalyst particle sizes on the conversion kinetics of acetic acid has been investigated. The maximum conversion of acetic acid was increased on increasing the feed molar ratio. From the experimental results, it was observed that the reaction is kinetically controlled rather than controlled by internal and external mass transfer. The experimental data were correlated with the pseudo homogeneous (PH), Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) models. The activity coefficients were calculated using UNIQUAC model to account for the non-ideal behaviour of the components. Of the different kinetic models; the LH, surface rate-determining model, fitted best with the experimental data.

Ultrasound assisted synthesis of methyl butyrate using heterogeneous catalyst

Ultrasound assisted esterification of butyric acid with methanol was investigated in an ultrasound irradiated isothermal batch reactor using acid ion-exchange resin (amberlyst-15) as a catalyst. Effect of parameters such as temperature (323-353 K), catalyst loading (0-8.5%w/w), alcohol to acid ratio, M (2-6), ultrasound power (0-145 W), duty cycle (0-85%) and amount of molecular sieves added (0-11%w/w) on the rate of reaction was studied. At optimized parameters, a maximum conversion of 91.64% was obtained in 120 min in presence of ultrasound. Experimental kinetic data were correlated by using Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHH W) models taking into account reverse reaction. Studies showed that single site LHHW with reactants and products both adsorbing on catalyst surface was most suited for the obtained experimental data. Activation energy determined based on heterogeneous kinetics was in the range 49.31-57.54 kJ/mol while it was 18.29 kJ/mol using homogeneous model.

Kinetic study of the removal of dimethyl phthalate from an aqueous solution using an anion exchange resin

Phthalate acid esters are becoming an important class of pollutants in wastewaters. This study addresses the kinetics of removal of dimethyl phthalate (DMP) using the anion exchange resin D201-OH from an aqueous solution. The effects of various factors on the removal rate and efficiency were investigated. An overall initial removal rate (OIRR) law and a pseudo first-order kinetic (PFOK) model were also developed. The internal diffusion of DMP within the resin phase of D201-OH is the rate-controlling step. Optimization of the particle size and pore structure of the resin D201-OH, the DMP concentration, and the reaction temperature can improve the DMP removal rate. The hydrolysis reaction of DMP catalyzed by D201-OH indicates an overall reaction order of 1.76, a value that is between the first order and the second order. The apparent activation energy of the reaction is 34.6 kJ/mol, which is below the homogeneous alkaline hydrolysis activation energy of 44.3 kJ/mol. The OIRR law can quantify the initial removal rate under different conditions. The results also show that the theoretical DMP removal efficiency predicted by the PFOK model agrees well with the experimentally determined values. Our research provides valuable insights into the primary parameters influencing the kinetic process, which enables a focused improvement in the removal or hydrolysis rate for similar processes.