Acid-catalyzed Esterification Research Articles

A new isopropyl esterification method for quantitative profiling of short-chain fatty acids in human and cow milk by gas chromatograph-mass spectrometer

Short-chain fatty acids (SCFAs) content in milk may have been underestimated due to the neglect of the esterified SCFAs content and the lack of an accurate detection method, especially for C1:0, C2:0, and C3:0 SCFAs. In this study, an accurate gas chromatography-mass spectrometry profiling method was established for 10 SCFAs. A 2-step esterification, including alkaline saponification (60°C for 30 min) and acid-catalyzed esterification (80°C for 150 min) in water/isopropyl/hexane (1:2:1, volume ratio), was found to be the most suitable for the quantification of esterified and nonesterified SCFAs analysis. The validation results demonstrate satisfactory linearity, sensitivity, matrix effects, precision, and accuracy. The recoveries of nonesterified and esterified SCFAs ranged from 82.78% to 112.49%, respectively. Human milk is distinguished from cow milk by its higher C1:0 and C2:0 content and lower C4:0 and C6:0 content. This method successfully accomplished qualitative and quantitative estimation of all 10 SCFAs in milk, including both nonesterified and esterified SCFAs. Furthermore, whether our method is applicable for the determination of SCFAs in serum, rumen fluid, and feces remains to be explored.

Visible Light-Promoted Oxidative Cross-Coupling of Alcohols to Esters

Ester is one of the most significant functional groups in organic chemistry and is enclosed in several valued molecules. Usually, esters are prepared through the acid-catalyzed esterification reaction of carboxylic acids with alcohols, transesterification of esters with alcohols, or via activation of carboxylic acids followed by the addition of alcohols. However, these procedures typically imply the excess use of reactants and harsh reaction conditions. Visible light-mediated photoreactions have been disclosed to display a safe, sustainable, and accessible alternative to traditional methods, and to lead new reactivity modes in organic procedures. In this context, we propose a transition metal-based and organic-based photocatalyst-free synthesis of esters from alcohols induced by visible light. The methodology can be carried out using sunlight or artificial visible light as a solar simulator or a blue LED source.

Heteropoly acid supported on hierarchical Y zeolite decorated SiC foam as the structured catalytic packing for reactive distillation synthesis of ethyl lactate

Rational design of catalytic packing is crucial in developing reactive distillation (RD) processes as efficient in-situ coupling of reaction and separation is required. Structured catalytic packings are advantageous than the conventional packings (e.g., inert packing + catalyst ‘tea bags’), due to the integration of the catalysis and separation function in one unit, mitigating mass/heat transfer limits. Herein, we present one of the latest developments in the field of structured catalytic packings, which was applied to a pilot-scale RD process of ethyl lactate (EL) synthesis via acid-catalyzed esterification and showed the advantages. The tungstophosphoric acid and hierarchical Y zeolite were uniformly decorated on corrugated silicon carbide (SiC) foam sheets via new preparation method (of ultrasound-assisted impregnation and microwave-assisted drying). The activity of the resulting materials was first assessed in a batch reactor, then the best candidate was employed by the pilot process. Findings from the pilot-scale RD experiments show that the developed structured SiC foam catalytic packing (SSFCP) exhibited an excellent performance (with the normalized conversion of 0.155 mol/gcatalyst), outperforming the conventional seepage catalytic packing internal (0.002 mol/gcatalyst). The influence of various variables (including molar feed ratio, feed position and reflux ratio) on the process performance of the pilot RD rig was also investigated and optimized, achieving a lactic acid conversion of 46.9 % and EL purity of 44.9 % (bottom). The good performance was attributed to the improved mass transfer thanks to SiC foam corrugated sheet (which encourage the vortex formation), thereby enabling more efficient coupling with the reaction. The SSFCP demonstrated reasonable stability, making it a promising candidate for relevant practical RD applications.

Carbon-Based Solid Acid Catalyzed Esterification of Soybean Saponin-Acidified Oil with Methanol Vapor for Biodiesel Synthesis

In this study, carbon-based solid acids were used to catalyze the esterification of soybean saponin-acidified oil (SSAO) with methanol vapor for the synthesis of biodiesel. The esterification conversion under different conditions was determined, and the catalyst components were determined using acid-base titration, elemental analysis, and inductively coupled plasma spectroscopy. The results showed that the conversion of SSAO under the optimal esterification conditions (i.e., catalyst loading of 6 wt%, methanol/oil molar ratio of 50:1, reaction temperature of 76 °C, and reaction time of 4 h) was 98.9%. The conversion was still higher than 80% after the catalyst was reused for four batches. The methanol vapor esterification (MVE) effectively mitigated the leaching of sulfonic acid groups and the production of sulfonate esters, while the activated white clay adsorption can significantly reduce the metal ion content in SSAO, which weakens its ion exchange with sulfonic acid groups. MVE for biodiesel synthesis is less costly compared to liquid methanol esterification because of the high recovery of methanol and the improved catalyst stability. Therefore, the addition of methanol in the form of vapor in the carbon-based solid acid-catalyzed esterification system is an effective way to maintain the catalyst activity and reduce the production cost of biodiesel.

A facile route for concurrent fabrication and surface selective functionalization of cellulose nanofibers by lactic acid mediated catalysis

Celulose nanofibers are lightweight, recycable, biodegradable, and renewable. Hence, there is a great interest of using them instead of fossil-based components in new materials and biocomposites. In this study, we disclose an environmentally benign (green) one-step reaction approach to fabricate lactic acid ester functionalized cellulose nanofibrils from wood-derived pulp fibers in high yields. This was accomplished by converting wood-derived pulp fibers to nanofibrillated “cellulose lactate” under mild conditions using lactic acid as both the reaction media and catalyst. Thus, in parallel to the cellulose nanofibril production, concurrent lactic acid-catalyzed esterification of lactic acid to the cellulose nanofibers surface occured. The direct lactic acid esterification, which is a surface selective functionalization and reversible (de-attaching the ester groups by cleavage of the ester bonds), of the cellulose nanofibrils was confirmed by low numbers of degree of substitution, and FT-IR analyses. Thus, autocatalytic esterification and cellulose hydrolysis occurred without the need of metal based or a harsh mineral acid catalysts, which has disadvantages such as acid corrosiveness and high recovery cost of acid. Moreover, adding a mineral acid as a co-catalyst significantly decreased the yield of the nanocellulose. The lactic acid media is successfully recycled in multiple reaction cycles producing the corresponding nanocellulose fibers in high yields. The disclosed green cellulose nanofibril production route is industrial relevant and gives direct access to nanocellulose for use in variety of applications such as sustainable filaments, composites, packaging and strengthening of recycled fibers.

Process Optimization of Biodiesel from Used Cooking Oil in a Microwave Reactor: A Case of Machine Learning and Box–Behnken Design

In the present investigation, response surface methodology (RSM) and machine learning (ML) are applied to the biodiesel production process via acid-catalyzed transesterification and esterification of triglyceride (TG). In order to optimize the production of biodiesel from used cooking oil (UCO) in a microwave reactor, these models are also compared. During the process, Box–Behnken design (BBD) and an artificial neural network (ANN) were used to evaluate the effect of the catalyst content (3.0–7.0 wt.%), methanol/UCO mole ratio (12:1–18:1), and irradiation time (5.0–9.0 min). The process conditions were adjusted and developed to predict the highest biodiesel yield using BBD with the RSM approach and an ANN model. With optimal process parameters of 4.94 wt.% catalyst content, 16.76:1 methanol/UCO mole ratio, and 8.13 min of irradiation time, a yield of approximately 98.62% was discovered. The coefficient of determination (R2) for the BBD model was found to be 0.9988, and the correlation coefficient (R) for the ANN model was found to be 0.9994. According to the findings, applying RSM and ANN models is advantageous when optimizing the biodiesel manufacturing process as well as making predictions about it. This renewable and environmentally friendly process has the potential to provide a sustainable route for the synthesis of high-quality biodiesel from waste oil with a low cost and high acid value.

Intensification and Optimization of FAME Synthesis via Acid-Catalyzed Esterification Using Central Composite Design (CCD).

The acid-catalyzed pre-treatment esterification process is required for low-cost feedstock with high free fatty acids (FFAs) to avoid the saponification that occurs during alkali-catalyzed transesterification for the production of fatty acid alkyl esters (FAAE). Reverse hydrolysis in acid-catalyzed esterification causes a decrease in fatty acid methyl ester (FAME) yield. Therefore, the esterification process must be intensified. This study aims to develop and optimize a low-temperature intensification process to enhance biodiesel yield and reduce energy consumption. Three intensification systems were studied: co-solvent technique, co-solvent coupled with adsorption of water using molecular sieves, and entrainer-based continuous removal of water. The process variables of esterification reaction in co-solvents without the adsorption system were optimized by using central composite design (CCD). The study showed that the co-solvent without the adsorption system was effective in intensifying the FFA conversion (XFFA) at low temperatures, compared to the other two systems, due to the dilution effect at high co-solvent/entrainer amount required for sufficient vapors in the adsorption system. Optimized process variables have achieved 95% XFFA within 75 min at 55 °C, 20 mL/100 g of oil DEE, 9 MR, 3 wt % H2SO4, and 320-350 RPM in a co-solvent without the adsorption system.

Chemically vs Enzymatically Synthesized Polyglycerol-Based Esters: A Comparison between Their Surfactancy.

Polyglycerol fatty acid esters (PGFAEs) are gaining interest in several industrial sectors due to their excellent surfactant properties and their wide range of hydrophilic-lipophilic balance (HLB) values. Moreover, they can be prepared from renewable resources, i.e., fatty acids and glycerol. In this study, polyglycerol-2 stearic acid esters (PG2SAEs) were synthesized by the enzymatic esterification of polyglycerol-2 (PG2) and stearic acid (SA) using the immobilized lipase Novozym 435 as a biocatalyst in a solvent-free system. Reaction conditions, i.e., temperature (80 °C), reactant ratio (1:1.8), and enzyme loading (2.7% w/w), were finely optimized; furthermore, biocatalyst recycling was studied by assessing the residual activity of the lipase after each reaction cycle, up to 20 times. The composition of the enzymatically synthesized products (E) was roughly evaluated by chromatographic methods and mass spectrometry and compared with that of the esters obtained by acid-catalyzed esterification (C). Then, the surfactant properties of the prepared polyglycerol-based surfactants were investigated by interfacial tension studies. Specifically, the emulsifying capacity and stability and the rheological behavior of O/W emulsions prepared in the presence of E were deeply investigated in comparison with those of the chemically synthesized and commercially available product C.

Box-Behnken Design for Optimization on Esterification of Free Fatty Acids in Waste Cooking Oil Using Modified Smectite Clay Catalyst

A potential alternative fuel option is biodiesel, which is produced mostly from natural resources due to the limited availability of petroleum supplies and environmental issues. Waste cooking oil (WCO) containing a high concentration of free fatty acid (FFA) can be transformed into biodiesel, which substantially benefits the environment and for reducing the fuel . The use of smectite clay as a catalyst in the esterification reaction of WCO with methanol was studied. Smectite was chemically activated by sulfuric acid (H2SO4) to obtain the acid-modified smectite. The utilization of an acid-catalyzed esterification procedure as a pre-treatment for WCO for biodiesel synthesis has been studied in some detail. However, there aren't many effective ways to optimize this operation. The process variables used in this study's esterification of FFAs in WCO were optimized using a Box-Behnken design (BBD). At atmospheric pressure, the catalyst amount of 5.03 wt%, the methanol to WCO molar ratio of 22.38, and the reaction time of 3.01 h are the optimal running parameters for accomplishing 97.96% FFA conversion. The catalyst was employed five times in a row without noticeably lowering its catalytic effectiveness. The results showed that smectite clay is an essential, low-cost, and recyclable catalyst for the esterification of FFA in WCO.

Production of Alkyl Levulinates from Carbohydrate-Derived Chemical Intermediates Using Phosphotungstic Acid Supported on Humin-Derived Activated Carbon (PTA/HAC) as a Recyclable Heterogeneous Acid Catalyst

This work reports a straightforward and high-yielding synthesis of alkyl levulinates (ALs), a class of promising biofuel, renewable solvent, and chemical feedstock of renewable origin. ALs were prepared by the acid-catalyzed esterification of levulinic acid (LA) and by the alcoholysis of carbohydrate-derived chemical platforms, such as furfuryl alcohol (FAL) and α-angelica lactone (α-AGL). Phosphotungstic acid (PTA) was chosen as the solid acid catalyst for the transformation, which was heterogenized on humin-derived activated carbon (HAC) for superior recyclability. Using HAC as catalyst support expands the scope of valorizing humin, a complex furanic resin produced inevitably as a side product (often considered waste) during the acid-catalyzed hydrolysis/dehydration of sugars and polymeric carbohydrates. Under optimized conditions (150 °C, 7 h, 25 wt.% of 20%PTA/HAC-600 catalyst), ethyl levulinate (EL) was obtained in an 85% isolated yield starting from FAL. Using the general synthetic protocol, EL was isolated in 88% and 84% yields from LA and α-AGL, respectively. The 20%PTA/HAC-600 catalyst was successfully recovered from the reaction mixture and recycled for five cycles. A marginal loss in the yield of ALs was observed in consecutive catalytic cycles due to partial leaching of PTA from the HAC support.

Analysis of the Antioxidant Activity, Lipid Profile, and Minerals of the Skin and Seed of Hazelnuts (Corylus avellana L.), Pistachios (Pistacia vera) and Almonds (Prunus dulcis)—A Comparative Analysis

Nuts are dry, single-seeded fruits with a combination of beneficial compounds that aid in disease prevention and treatment. The aims of this research are to evaluate the total antioxidant activity (AI) by ferric reducing antioxidant power (FRAP) assay, fatty acids by acid-catalyzed esterification method, and minerals by inductively coupled plasma optical emission (ICP-OE) spectrometer in hazelnuts, pistachios, and almond seeds and skins. Considering total AI, the results demonstrated that the highest activity was found in hazelnut and pistachio skin. The results considering minerals demonstrated that manganese, zinc, and iron levels are high in almond and hazelnut skins, copper is dominant in pistachio skin and hazelnut seed, and selenium is high in pistachio and almond skins and seed. Finally, the results showed palmitic acid is present in almond skin and pistachio seed, palmitoleic acid is high in almond and pistachio skins, and stearic acid is present in almond and hazelnut skins. Oleic acid was found in hazelnut seeds and their skin, linoleic acid in almond skin and pistachio seeds, and α-linolenic acid in almond and pistachio skins. In conclusion, hazelnut, pistachio, and almond skins are a great source of antioxidants, minerals, and healthy fatty acids, making them useful for nutraceutical development.

A novel approach to methoxy polyethylene glycol-grafted sulfonated poly(maleic anhydride-alt-styrene) as superplasticizers in cement pastes

In this research, a novel method was developed to synthesize methoxy polyethylene glycol-grafted sulfonated poly(maleic anhydride-alt-styrene) (SPMS-g-mPEG) as cement superplasticizers. The method includes three main steps: 1) self-stabilized precipitation polymerization (2SP) of styrene and maleic anhydride for PMS microspheres; 2) gas-solid heterogeneous sulfonation reaction (GSR) of gaseous SO3 with PMS microspheres; 3) intramolecular sulfonic acid-catalyzed esterification reaction of mPEG with sulfonated PMS (SPMS). GSR can achieve uniform sulfonation of PMS microspheres, while overcoming the inherent drawbacks of the traditional homogeneous solution sulfonation process. SPMS and SPMS-g-mPEG with different structural parameters and uniform structure were successfully prepared and their effects on the fluidity and fluidity retention of cement pastes were systematically compared. For the samples demonstrating the best dispersing ability, the hydration heat and setting time of cement pastes, adsorption kinetics and compressive strength of mortar samples were determined further. Our work provides an innovative and effective approach to superplasticizers with outstanding properties and its uniform structure facilitates the investigation on the relationship between structure and properties.

Sulphonic-acid functionalized novel Limonia acidissima carbonaceous catalyst for biodiesel synthesis from Millettia pinnata oil: Optimization, kinetics, thermodynamics and cost analysis

In order to overcome the current fuel crisis affecting transportation, expanding environmental pollution challenges, and depletion of natural oil resources, a sustainable alternative to petroleum fuels must be developed. Biodiesel has been accepted as a promising substitute for petro-fuels in many countries because it can fulfill the requirements of the transportation industry. The present research introduces biodiesel production from Millettia pinnata (Karanja) oil utilizing waste wood apple (Limonia acidissima) shell in deriving carbonaceous catalysts in view of waste valorization for green energy generation towards alleviation of its ever-growing demand. The feedstock had a high free fatty acid (FFA) concentration based on proximate analysis, which indicated that an acid catalyst was required for fuel production. Analysis of the prepared catalyst was done by SEM, EDAX, FTIR, XRD, and BET. The optimization of esterification was performed with the RSM central composite design (CCD) experimental matrix, while the reaction time was 1.5 h at 55°C with 4 wt. % catalyst under 650 rpm and 50% w/w alcohol concentration. The actual yield was reported to be 98.95% under ideal conditions. The fuel characterization revealed that KOME (Karanja oil methyl ester) possesses physico-chemical characteristics suitable for biodiesel as per ASTM standards. Kinetic studies showed that the esterification follows pseudo-first-order kinetics with an activation energy of 62.61 kJ mol −1. The thermodynamic study confirmed that the acid-catalyzed esterification reaction is endothermic and non-spontaneous. The production cost of catalyst per kg of biodiesel was estimated to be $0.1649.

Biodiesel production from high free fatty acid byproduct of bioethanol production process

Biodiesel is a reliable and promising replacement of fossil diesel. It is stable, less toxic and can be produced from sustainable resources, including a variety of raw materials. Currently, the most widely used are vegetable oils (edible and nonedible), due to their availability. The present paper considers the potential of obtaining fatty acid ethyl esters (FAEE) from corn oil, which is a byproduct of bioethanol production process. The ultimate outcome would definitely increase the profitability of the initial bioethanol production process. The biodiesel production process was implemented in two steps, due to the high content of free fatty acids of the obtained corn oil. The first step includes an acid-catalyzed esterification process and the second step comprises an alkali-catalyzed transesterification process to receive FAEE. Two different catalysts (sulfuric acid and p-toluene sulfonic acid) were utilized and compared each other in the esterification process, in order to cope with high acid number of the raw material. A comprehensive qualitative and quantitative analysis of both feedstock and biodiesel was performed using gas chromatography-mass spectrometry method. The obtained biodiesel was characterized by a significantly lower cloud point compared to the feedstock and high acid number.

Kinetics Study of Acid-Catalyzed Sulfate Esterification Reactions for Atmospherically Relevant Polyols

Extensive laboratory and field studies have identified organosulfates as important constituents of secondary organic aerosol (SOA). However, the mechanisms by which these organosulfates form in the atmosphere remain uncertain. The rate constants for the acid-catalyzed sulfate esterification reactions of a series of polyols were measured via bulk kinetics experiments using nuclear magnetic resonance (NMR) spectroscopy. The NMR data indicated that while reactions that occurred at a terminal hydroxyl site were somewhat faster than reactions at internal hydroxyl sites, there were no other significant structure–reactivity trends among the series of polyols. These results suggest that neighboring hydroxyl groups do not significantly modify the sulfate esterification rates from those previously determined for monoalcohols. Extrapolation of the kinetics data to typical atmospheric SOA acidities suggests that sulfate esterification reactions of polyols are unlikely to be a significant source of organosulfates. This conclusion is consistent with a previous study of monoalcohols which made similar conclusions about the kinetic infeasibility of this reaction type.

Activity-Based Models to Predict Kinetics of Levulinic Acid Esterification.

The solvent is of prime importance in biomass conversion as it influences dissolution, reaction kinetics, catalyst activity and thermodynamic equilibrium of the reaction system. So far, activity-based models were developed to predict kinetics and equilibria, but the influence of the catalyst on kinetics has not been succesfully predicted by thermodynamic models. In this work, the thermodynamic model ePC-SAFT advanced was used to predict the activities of the reactants and of the catalyst at various conditions (temperature, reactant concentrations, γ-valerolactone GVL cosolvent addition, catalyst concentration) for the homogeneously acid-catalyzed esterification of levulinic acid (LA) with ethanol. Different kinetic models were applied, and it was found that the catalyst influence on kinetics could be predicted correctly by simultaneously solving the dissociation equilibrium of H2 SO4 catalyst along the reaction coordinate and by relating reaction kinetics to proton activity. ePC-SAFT advanced model parameters were only fitted to reaction-independent phase equilibrium data. The key reaction properties were determined by applying ePC-SAFT advanced to one experimental kinetic curve for a set of temperatures, yielding the reaction enthalpy at standard state , activation energy and the intrinsic reaction rate constant k=0.011 s-1 at 323 K, which is independent of catalyst concentration. The new procedure allowed an a-priori identification of the effects of catalyst, solvent and reactant concentration on LA esterification.

Integrated LC-MS/MS and transcriptome sequencing analysis to evaluate the feasibility of green and red prickly ash as biodiesel crops

Fatty acids are expected to replace fossil fuels for bioenergy and are also important raw materials in industrial production. Prickly ash fruits are rich in fatty acids and can be used as plant raw materials for industrial oil extraction and development. Here, we performed qualitative and quantitative analyses of fatty acids in green and red prickly ash fruits using transcriptome and LC–MS/MS. Myristic acid, vaccenic acid, linoleic acid, γ-linolenic acid, and α-linolenic acid were the main fatty acids detected. The carbon chain lengths of the main components of diesel are C15–C19, and the main components of prickly ash fruit oil are C16 and C18 fatty acids, which can be used to prepare biodiesel by acid-catalyzed esterification. In addition, the fatty acid biosynthetic pathway and RDA showed that KASII plays a key role in fatty acid synthesis.

Core-shell assembly of ZrO2 nanoparticles with ionic liquid: a novel and highly efficient heterogeneous catalysts for Biginelli and esterification reactions.

Imidazolium sulfonic acid chloride grafted ZrO2 nanoparticles (ZrO2-IL) were synthesized through facile post-treatment of the nanoparticles with the imidazolium-sulfonic acid chloride ionic liquid. The immobilization of the ionic liquid over the ZrO2 nanoparticles was evident from the XRD, SEM, TEM, Raman, BET, and XPS analysis. The results obtained from the XRD analysis clearly show that the catalyst has an orthorhombic structure and from the BET analysis it is evident that the surface is mesoporous with uniform pore sizes and pore distribution. Further evidence of immobilization of ionic liquid over the ZrO2 NPs was obtained from the SEM, TEM, XPS, and Raman analysis. Under mild conditions, the synthesized heterostructure was used in the acid-catalyzed esterification of different acids. The ZrO2-IL catalyst converts 99% of the acid to ester with a 98.9% yield in 1h. The material was also shown to be highly efficient as catalyst for the Biginelli reaction under solvent-free conditions, with the catalyst for dihydropyrimidin-2(1H)-one (DHPMs) in 1h with 99.2% conversion and 99% yield. The synergy between the ionic liquid catalyst and the substrates increased the catalytic efficiency and resulted in high-yield product conversion. The mechanism of both transformation reactions was investigated, as well as the synergy between ionic liquid and ZrO2 nanoparticles for better catalytic efficiency was established.

Protonic ionic liquids as efficient phase-separation catalysts for esterification of trimethylolpropane and acrylic acid

The H 2 SO 4 -based imidazole ionic liquids performed as phase-separation catalysts for the esterification of trimethylolpropane and acrylic acids, exhibiting the best trimethylolpropane conversion (100%) and trimethylolpropane acrylate selectivity (86.4%). • H 2 SO 4 -based ionic liquids were applied as catalysts for esterification of trimethylolpropane and acrylic acid. • A novel phase-separation catalytic process was observed during the reaction. • 100% of trimethylolpropane conversion and 86.4% of trimethylolpropane acrylate selectivity were achieved. • The phase-separated ionic liquids can be steadily reused. Trimethylolpropane acrylate (TMPTA) is becoming an important organic chemistry intermediate, but it’s synthesis through the acid-catalyzed esterification of trimethylolpropane and acrylic acid is a challenge due to the poor activity and catalyst separation problems. In this work, a series of 1,3-propanesultone (PS)-functionalized imidazole ionic liquids (ILs) are prepared and evaluated as the acid catalysts for this reaction, including the catalytic performance comparison, optimization of reaction conditions, and the catalytic reusability. The obtained H 2 SO 4 -based IL ([IMPSH]HSO 4 ) caused a phase-separation catalytic process (reacted as a homogeneous catalyst, but precipitated at the end of reaction like a heterogeneous catalyst), presenting the best trimethylolpropane conversion (100%) and TMPTA selectivity (86.4%). Such catalytic performance is even better than that of homogeneous H 2 SO 4 . Moreover, the catalyst can be steadily reused at least four times without obvious change in activity and its structure. The highly efficient and environmentally benign performance of [IMPSH]HSO 4 -catalyzed esterification of trimethylolpropane and acrylic acid make it possible to achieve industrial applications.

Solvent effect investigation on the acid-catalyzed esterification of levulinic acid by ethanol aided by a Linear Solvation Energy Relationship

When processing lignocellulosic biomass materials to obtain platform molecules such as levulinic acid (LA), alkyl levulinates or γ-valerolactone (GVL), the choice of solvent is of prime importance for kinetics. The knowledge of relationships between reaction kinetics and solvent serves as a decision tool for process design. To determine such relationships, esterification reactions was chosen because such reaction steps are present in several biomass conversion processes. In this work, kinetic models of LA esterification by ethanol over sulfuric acid in polar aprotic solvent (GVL) and polar protic solvents (water or ethanol) were developed and evaluated by Bayesian statistics. The apparent dissociation constants in solvents were estimated by ePC-SAFT approach to distinguish the proton concentration from the rate constants. The developed models can fit the experimental concentrations of ethyl levulinate and predict the proton concentration. Using the Kalmet-Abboud-Taft equation, linear relationships between estimated rate constants and solvent properties were established at different temperatures. We observed that solvents with low polarizability and high hydrogen-bond acceptor capacity should be favored for this reaction. Hence, the reaction of esterification is faster in ethanol solvent than in GVL solvent than in water solvent.