Reaction Conditions For Esterification Research Articles

Cold plasma-activated Ni-Co tandem catalysts with CN vacancies for enhancing CH4 electrocatalytic to methyl formate

The direct electrooxidation of methane (CH4OR) into high value-added liquid products has been considered an effective method to efficient and clean utilization of methane. However, this process is mainly limited by CH4 activation and subsequent intermediate regulation. Here, we report the first successful achieve methyl formate from CH4OR on Ni-Co tandem catalysts with CN vacancies prepared by H2 cold plasma. The faradaic efficiency of CH4OR into methyl formate reaches 56.7 % at 2.0 V vs. RHE with remained stability for 160 h. In situ ATR-SEIRAS and DFT calculations suggest that the CN vacancies can shift the d-band center of the active Ni sites upwards to enhance the chemisorption of CH4 over Ni atom near CN vacancy, generating the key intermediates of *CH3 and *CH2. *CH2 further overflows onto the Co atom around the same CN vacancy, providing favorable conditions for esterification reaction to obtain methyl formate. This work opens a new avenue for the development of efficient electrocatalytic systems for the clean utilization of methane and the electrosynthesis of methyl formate under ambient conditions.

Efficient production of biodiesel from palm fatty acid distillate using a novel hydrochar-based solid acid catalyst derived from palm leaf waste

To combat fuel shortages, pollution, and the exhaustion of natural oil resources, an environmentally friendly alternative to fossil fuels, such as biodiesel, is essential for meeting global transportation demands. A novel heterogeneous acid catalyst for production of biodiesel from low-cost, high free fatty acid feedstocks was synthesized in this study by activating and impregnating hydrochar from palm leaf (PL) waste with H3PO4 and H2SO4. Subsequently, the sulfonated catalyst was utilized for the esterification of palm fatty acid distillate (PFAD). FT-IR, XRD, FESEM, EDX, BET, TGA, and surface acidity methods were employed to characterize the acid catalyst. Using the one-variable-at-a-time (OVAT) technique, the optimized reaction conditions for esterification of PFAD using the hydrochar-based catalyst were 4 wt% catalyst loading, 353.15 K reaction temperature, 4 h reaction time, and 18:1 methanol: PFAD molar ratio. At these conditions, a maximum biodiesel yield of 93.56% was achieved. The catalyst exhibited excellent reusability and stability throughout five reaction cycles, maintaining biodiesel yields above 80% after each cycle. Analysis of the fuel properties revealed that the biodiesel derived from PFAD met the physiochemical criteria outlined in ASTM D6751, the American biodiesel standard. The kinetic study revealed that the esterification reaction followed pseudo-first-order kinetics with an activation energy (Ea) of 23.70 kJ/mol. Furthermore, the thermodynamic enthalpy (∆H*) and Gibbs' free energy (∆G*) of esterification were 20.9 and 33.41 kJ/mol, respectively, indicating that the reaction was an endothermic and non-spontaneous process.

Effect of methanol purity on biodiesel production from lauric acid using esterification reaction

Indonesia is a leading country in agriculture, thus opening up great opportunities for the development of biodiesel. However, the main challenge is ensuring the sustainable acquisition of feedstock, including using methanol as a reactant to manufacture biodiesel. Making biodiesel using lower-purity methanol is possible. This study aims to compare the effect of methanol purity on biodiesel manufacturing. This research uses esterification reactions to manufacture biodiesel from lauric acid and methanol. The catalyst used is an amberlyst catalyst. A design was applied using catalyst amounts of 5% to 20% and variations in the purity of methanol from 95% to 99%. The best esterification reaction conditions are obtained at 99% methanol purity and 20% catalyst amount, which is 98.9%. In contrast, there is no significant difference in results for the flash point obtained, and the results obtained have met the standards of the American Society for Testing and Materials (ASTM).

Direct esterification of amides by the dimethylsulfate-mediated activation of amide C–N bonds

Amides are important intermediates in organic chemistry and the pharmaceutical industry, but their low reactivity requires catalysts and/or severe reaction conditions for esterification. Here, a novel approach was devised to convert amides into esters without the use of transition metals. The method effectively overcomes the inherent low reactivity of amides by employing dimethylsulfate-mediated reaction to activate the C-N bonds. To confirm the proposed reaction mechanism, control experiments and density functional theory (DFT) calculations were conducted. The method demonstrates a wide array of substrates, including amides with typical H/alkyl/aryl substitutions, N,N-disubstituted amides, amides derived from alkyl, aryl, or vinyl carboxylic acids, and even amino acid substrates with stereocentres. Furthermore, we have shown the effectiveness of dimethylsulfate in removing acyl protective groups in amino derivatives. This study presents a method that offers efficiency and cost-effectiveness in broadening the esterification capabilities of amides, thereby facilitating their increased utilization as synthetic compounds in diverse transformations.

Photocatalyzed Oxidative Tandem Reaction Mediated by Bipyridinium for Multifunctional Derivatization of Alcohols.

The multifunctional derivatization of alcohols has been achieved by the bipyridinium-based conjugated small molecule photocatalysts with redox center and Lewis acid site. Besides exhibiting high activity in the selective generation of aldehydes/ketones, acids from alcohols through solvent modulation, this system renders the first selective synthesis of esters via an attractive cross-coupling pattern, whose reaction route is significantly different from the traditional condensation of alcohols and acids or esterification from hemiacetals. Following the oxidization of alcohol to aldehyde via bipyridinium-mediated electron and energy transfer, the Lewis acid site of bipyridinium then activates the aldehyde and methanol to obtain the acetal, which further reacts with methanol to generate ester. This method not only demonstrates a clear advantage of bipyridinium in diverse catalytic activities, but also paves the way for designing efficient multifunctional small molecule photocatalysts. This metal- and additive-free photocatalytic esterification reaction marks a significant advancement towards a more environmentally friendly, cost-effective and green sustainable approach, attributed to the utilization of renewable substrate alcohol and the abundant, low-cost air as the oxidant. The mildness of this esterification reaction condition provides a more suitable alternative for large-scale industrial production of esters.

Esterification of tall oil fatty acid catalyzed by Zr4+-CER in fixed bed membrane reactor

In this study, Zr4+-CER was used as a solid acid catalyst to catalyze the esterification reaction. The esterification of tall oil fatty acids (TOFA) with ethanol dehydration was studied by fixed-bed coupled pervaporation (PV). The Zr4+-CER catalyst was characterized in detail by Py-IR, NH3-TPD, BET, IEC, ICP-OES, SEM, and FTIR. The effects of ethanol/oil molar ratio, catalytic bed height, reaction temperature and feed rate on TOFA conversion were investigated. The esterification reaction conditions were optimized by orthogonal test, and the optimal conditions were ethanol/oil molar ratio 15:1, catalytic bed height 120 mm, reaction temperature 80 °C, and feed rate 0.3 ml/min. The TOFA conversion rate was 99.51 %. After six esterification cycles, the TOFA conversion of the catalyst reached 90.03 %, indicating that the catalyst had high stability. The esterification process using Zr4+-CER as the catalyst follows the second-order kinetic model, with an activation energy of 39.54 kJ/mol. Furthermore, the economic analysis of biodiesel production indicates that the Zr4+-CER catalyst has the potential to decrease production expenses, presenting an encouraging prospect for future biodiesel industrialization.

Investigation of free fatty acid reduction from mixed crude palm oil using 3D-printed rotor–stator hydrodynamic cavitation: An experimental study of geometric characteristics of the inner hole

A continuous esterification process is employed to decrease the free fatty acid (FFA) concentration of FFA-rich mixed crude palm oil. Both optimal and recommended conditions are determined for the esterification reaction conditions and the geometry of the 3D-printed rotor design in the rotor–stator hydrodynamic cavitation reactor. This study is primarily concerned with the effect of the cavitation device configuration, especially the rotor design, on FFA reduction. Instead of conventional spherical or cylindrical drilled holes, a point angle cone-shaped hole is used to create cavities over the rotor surface. These point angles are adjusted to clarify their effect on FFA reduction. The response surface methodology is applied to determine the optimal concentrations of methanol and sulfuric acid, rotor speed, hole diameter and depth, and cone point angle. The recommended conditions are 20.8 wt% methanol, 2.6 wt% sulfuric acid, 3000 rpm, 5 mm hole diameter, 5 mm hole depth, and 110°, respectively. Under this configuration, the FFA content is reduced from 12.014 wt% to around 1 wt%. A maximum yield of 97.34 vol% esterified oil is obtained through a completed phase separation step, and 93.31 vol% pure oil is collected after the cleansing step. The recommended conditions result in reduced chemical usage, cheaper FFA reduction, and lower environmental impact. This creative rotor design effectively improves our understanding of the geometry of the cavitation device, thus enhancing the cavitation effect in industrial operations.

Example of Outcome-based Investigational Experiment and the Development of Innovation Capabilities: Primary Study on the Ultrasound-Assisted Fischer Esterification Reaction Conditions

Example of Outcome-based Investigational Experiment and the Development of Innovation Capabilities: Primary Study on the Ultrasound-Assisted Fischer Esterification Reaction Conditions

Click amidations, esterifications and one–pot reactions catalyzed by Cu salts and multimetal–organic frameworks (M–MOFs)

Amides and esters are prevalent chemicals in Nature, industry and academic laboratories. Thus, it is not surprising that a plethora of synthetic methods for these compounds has been developed along the years. However, these methods are not 100% atom economical and generally require harsh reagents or reaction conditions. Here we show a “spring–loaded”, 100% atom–efficient amidation and esterification protocol which consists in the ring opening of cyclopropenones with amines or alcohols. Some alkyl amines react spontaneously at room temperature in a variety of solvents and reaction conditions, including water at different pHs, while other alkyl amines, aromatic amines and alcohols react in the presence of catalytic amounts of simple Cu2+ salts or solids. A modular reactivity pattern (alkyl amines >> alkyl alcohols >> phenols >> aromatic amines) enables to design orthogonal and one–pot reactions on well–defined catalytic Multimetal–Organic Frameworks (M–MOFs, M= Cu, Ni, Pd), to easily functionalize the resulting cinnamides and cinnamic esters to more complex molecules. The strong resemblance of the amidation and esterification reaction conditions here reported with the copper–catalyzed azide–alkyne cycloaddition (CuAAC) allows to define this fast, clean and flexible protocol as a click reaction.

Biodiesel Synthesis from High Free-Fatty-Acid Chicken Fat using a Scrap-Tire Derived Solid Acid Catalyst and KOH.

A heterogeneous solid acid catalyst was synthesized using tire polymer waste (TPW) for the esterification of waste chicken fat (CF) enriched with fatty acids. The TPW was carbonized and functionalized with concentrated sulfuric acid under various sulfonation conditions to obtain a sulfonated tire polymer char (TPC-SO3H) catalyst. The TPC-SO3H catalyst was further characterized via acid-base titration (to ascertain the total concentration of acid), X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), and Brunauer–Emmett–Teller (BET) analysis. The esterification reaction conditions of extracted chicken fat with methanol and the viability of catalyst reuse were also investigated. The composition of the free fatty acid (FFA) decreased to below 1% under optimum reaction conditions of 5% TPC-SO3H catalyst, the methanol-to-CF molar-ratio of 15:1, and a reaction time of 120 min at 70 °C. The catalyst preserved its conversion efficiency above 90%, even after three cycles. The results demonstrate that the catalyst is applicable and efficient in the esterification of raw materials containing various fatty acid compositions since different carbonized materials have distinct abilities to combine acid groups. Furthermore, after de-acidification of CF-FFA by the as-prepared TPC-SO3H catalyst, the neutral CF was transesterified completely to biodiesel and characterized via Fourier Transform Infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy and physicochemical analysis. This work unveils a promising technique for utilizing tire waste generated in large quantities for the development of a novel heterogeneous acid catalyst for biodiesel production.

Artificial neural network method modeling of microwave-assisted esterification of PFAD over mesoporous TiO2‒ZnO catalyst

An artificial neural network (ANN) was employed to predict biodiesel yield through microwave-assisted esterification of palm fatty acid distillate (PFAD) oil over TiO2‒ZnO mesostructured catalyst. The experimental data of biodiesel content (%) was carried out via changing three input factors (i.e. methanol:PFAD molar ratio, catalyst concentration, and reaction time). The results indicated that ANN is an appropriate approach for modeling and optimizing fatty acid methyl ester (FAME) yield performed over the microwave-assisted esterification process. The network was trained by five different algorithms (i.e. batch backpropagation (BBP), incremental backpropagation (IBP), Levenberg‒Marquardt (LM), genetic algorithm (GA), and quick propagation (QP)). The evaluation disclosed that the QP algorithm gave the least root mean squared error (RMSE), absolute average deviation (AAD), and the highest determination coefficient (R2) for both training and testing data groups. The confirmation test results of the ANN-based on QP-3-10-1 revealed that the RMSE, AAD, and the highest R2 were 0.741, 0.776, and 0.997, correspondingly. All in all, QP‒3‒10‒1 model offered the best possible mathematical qualities amongst all algorithms. Over this method, the FAME yield was determined at 97.45% (relating to the actual FAME yield of 97.33%) which was attained over 3 wt% mesoporous TiO2‒ZnO catalyst, methanol:PFAD molar ratio of 9:1 within 25 min of operating time. The esterification reaction conditions predicted by ANN showed to be potential for modeling and predicting FAME yield with an extremely well precision of 97.06%.

Optimization of Esterification Reaction Conditions Through the Analysis of the Main Significant Variables

Biodiesel production from residual sources is gaining considerable attention nowadays. Consequently, many different studies with in-depth analysis concerning the influence of the transesterification reaction conditions are available in the literature. However, further evaluation of the esterification of fatty acids in the biodiesel industry is still needed. In this study, different parameters influencing the esterification reaction behavior using ethanol as the alcohol and lauric acid as the FFA are analyzed through factorial design and ANOVA methodologies to verify which ones are significant in the reaction. In total, four parameters were evaluated: temperature, catalyst concentration, ethanol/FFA ratio, and ethanol/water ratio. The temperature and ethanol/water ratio had a major influence on the reaction, as increasing these parameters greatly improved reaction conversion. It was also verified that using hydrous ethanol in the esterification reaction is possible in some conditions.

Two-Stage Biodiesel Synthesis from Used Cooking Oil with a High Acid Value via an Ultrasound-Assisted Method

In this study, ultrasound was used to accelerate two-stage (esterification–transesterification) catalytic synthesis of biodiesel from used cooking oil, which originally had a high acid value (4.35 mg KOH/g). In the first stage, acid-catalyzed esterification reaction conditions were developed with a 9:1 methanol/oil molar ratio, sulfuric acid dosage at 2 wt %, and a reaction temperature of 60 °C. Under ultrasound irradiation for 40 min, the acid value was effectively decreased from 4.35 to 1.67 mg KOH/g, which was decreased to a sufficient level (<2 mg KOH/g) to avoid the saponification problem for the subsequent transesterification reaction. In the following stage, base-catalyzed transesterification reactions were carried out with a 12:1 methanol/oil molar ratio, a sodium hydroxide dosage of 1 wt %, and a reaction temperature of 65 °C. Under ultrasound-assisted transesterification for 40 min, the conversion rate of biodiesel reached 97.05%, which met the requirement of EN 14214 standard, i.e., 96.5% minimum. In order to evaluate and explore the improvement of the ultrasound-assisted two-stage (esterification–transesterification) process in shortening the reaction time, additional two-stage biodiesel synthesis experiments using the traditional mechanical stirring method under the optimal conditions were further carried out in this study. It was found that, under the same optimal conditions, using the ultrasound-assisted two-stage process, the total reaction time was significantly reduced to only 80 min, which was much shorter than the total time required by the conventional method of 140 min. It is worth noting that compared with the traditional method without ultrasound, the intensification of the ultrasound-assisted two-stage process significantly shortened the total time from 140 min to 80 min, which is a reduction of 42.9%. It was concluded that the ultrasound-assisted two-stage (esterification–transesterification) catalytic process is an effective and time-saving method for synthesizing biodiesel from used cooking oil with a high acid value.

Simulation, optimization, and economic analysis of process to obtain esters from fatty acids

AbstractWaste oils are a very promising raw material in the biodiesel industry, which is why great efforts have focused on the removal of the free fatty acids (FFAs) present in this source, mainly through the esterification reaction. Many studies have evaluated the influence of different variables on the reaction conversion, such as temperature, catalyst concentration, and alcohol/oil ratio. However, it is still necessary to verify how the esterification is affected by higher water concentration. In this study, different acid‐catalyzed esterification reaction conditions with distinct water concentrations were tested experimentally, and a new rate expression was proposed. This newly obtained reaction kinetics was then used to undertake a complete analysis of the biodiesel production process from waste oil, evaluating the influence of higher water concentrations in the esterification, and including different optimizations and an economic evaluation. Concerning some of the process modifications, it was verified that the inclusion of three energy‐saving heat exchangers reduced utility costs by 40%. In contrast, the inclusion of an ethanol‐recycling distillation column reduced raw material costs by 40%. Different settings were also tested, varying the feed composition and the esterification reaction time and conditions, resulting in a payback period of less than 3 years in any evaluated scenario. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Enzymatic Synthesis of β-Sitosterol Laurate by Candida rugosa Lipase AY30 in the Water/AOT/Isooctane Reverse Micelle.

Phytosterols are regarded as compounds able to reduce total and low-density lipoprotein cholesterol in the blood, and their esterified derivatives could help to improve the effectiveness of this function. In the present study, the water/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/isooctane reverse micelle (RM) system was set up as a reaction medium for Candida rugosa lipase AY30 (CRL AY30) to synthesize β-sitosterol laurate (β-SLE). The product was identified by TLC, FT-IR, and HPLC-APCI-QqQ-MS/MS and quantified by HPLC. Through stepwise optimization, it was found that CRL AY30 had the highest activity in the water/AOT/isooctane RM system where 50mM PBS with a pH of 7.5 was adopted as water core to carry CRL AY30, and the proportion of [CRL AY30] (mg/mL), [water] (mM), and [AOT] (mM) was set in 3:375:25, respectively, in isooctane. After screened with single-factor experiments, the esterification reaction conditions in the CRL AY30-water/AOT/isooctane RM system were further optimized by the response surface method as follows: the mole ratio of β-sitosterol to lauric acid of 1:3.5 (25mM β-sitosterol), the enzyme load of 18% (w/w total reactants), the reaction temperature of 47°C, and the reaction time of 48h. As a result, the maximum esterification rate was up to 88.12 ± 0.79%.

Esterification of free fatty acids using ammonium ferric sulphate-calcium silicate as a heterogeneous catalyst

In view of the fast depletion of fossil fuels, biodiesel seems to be a possible new alternative to counter the fuel crisis. In order to avoid excessive exploitation of agricultural land for the production of food crop feedstock, the main focus has been on the usage of waste cooking oils meant for disposal to be used in biodiesel production. However, the high free fatty acid (FFA) content in waste oils has been an issue and it is envisaged that heterogeneous acid catalysts can be utilised as they would have a higher tolerance of FFAs and water. In this study, we report the synthesis and the utilisation of an inexpensive heterogeneous acid catalyst, namely ammonium ferric sulphate-calcium silicate (AFS-CS) synthesised via the impregnation method in 2:1 mass ratio in biodiesel production. The reaction conditions for esterification of lauric acid (LA) was optimised by using both standard and statistical analysis method which gave maximum methyl esters conversion of 100% within 2 h reaction time, 4 wt% of AFS-CS catalyst amount and 15:1 molar ratio of methanol to LA at 65 °C. Palm fatty acid distillate (PFAD) was esterified by using the same optimised conditions, which gave 72.6% of methyl esters conversion.

Semi-continuous Production of 2-Ethyl Hexyl Ester in a Packed Bed Reactor: Optimization and Economic Evaluation.

The aim of this work was to investigate the technical as well as the economic feasibility of producing 2-ethyl hexyl oleate (2-EHO), a non-phthalate plasticizer in a solvent free medium. The esterification reaction between oleic acid and 2-ethyl hexyl alcohol was carried out in a packed bed reactor (PBR) using Candida antarctica lipase B (Novozym 435; Novozymes; Copenhagen-Denmark) as biocatalyst. RSM was employed to optimize the esterification reaction conditions. The optimum reaction conditions were found to be flow rate of 1.5 mL/min, No. of cycles of 12 and molar ratio of 4:1 2-ethyl hexanol to oleic acid. The maximum experimental and predicated conversions were found to be 95.8% and 95.61% respectively. Formation of 2-EHO was approved by FTIR, 1HNMR and 13CNMR. From the economic prospective, PBR was capable of producing 2-EHO with a purity of more than 94% over 480 h without remarkable reduction of enzyme activity. This revealed an economic production of 2-EHO at a yield of 2 tons kg-1 lipase. The manufacturing cost was found to be $ 1.88 /kg 2-EHO, this contributed to a profit of about 30% compared to the commercial price of 2-EHO. Such results approve the technical and economic feasibility for this sustainable method in esters production.

Immobilizing Ni (II)-Exchanged Heteropolyacids on Silica as Catalysts for Acid-Catalyzed Esterification Reactions

Biodiesel was synthesized from oleic acid using Ni (II)-exchanged heteropolyacids immobilized on silica (Ni0.5H3SiW / SiO2 ) as a solid acid catalyst. Based on detailed analyses of FT-IR, XRD, TG and SEM, the structural, surface and thermal stability of Ni0.5H3SiW / SiO2 were investigated. Obtained results demonstrated that the Keggin structure was well in the immobilization process and possess a high thermal stability. Various esterification reaction conditions and reusability of catalyst were studied. High oleic acid conversion of 81.4 % was observed at a 1:22 mole ratio (oleic acid: methanol), 3 wt. % catalyst at 70 °C for 4 h. The Ni0.5H3SiW / SiO2 catalyst was reused for several times and presented relatively stable. More interestingly, the kinetic studies revealed the esterification process was compatible with the first order model, and a lower activation energy was obtained in this catalytic system.

Tin-Empty Palm Bunch Ash Impregnated Zeolite as Suitable Catalyst for Simultaneous Transesterification-Esterification Reaction of Palm Oil

A single-step method was developed for methyl ester production from palm oil using tin-empty palm bunch ash impregnated zeolite (Sn-PBA-Zeolite) as heterogeneous catalyst. The weight ratios between Sn solution and zeolite 1:4, while the weight of the PBA was varied from 5, 10, 15, 20, 25, and 30 g in 60 mL of distilled water. Effects of reaction time, molar ratio of reactants, and catalyst concentration on the yield of methyl ester were studied. Characteristics of methyl ester produced were also investigated. The optimal conditions for transesterification reaction carried out by using a Sn-PBA-Zeolite of 1:4:25 weight ratio were a palm oil/methanol molar ratio 1:6, catalyst concentration (3% wt/wt), and 3 hours reaction time, whereas the maximum yield of methyl ester reached 76.21% wt/wt. The optimal conditions for esterification reaction carried out by using a Sn-PBA-Zeolite of 1:4:5 weight ratio were a palm oil/methanol molar ratio 1:12, catalyst concentration (3% wt/wt), and 3 hours reaction time, and the maximum yield of methyl ester reached 94.76% wt/wt. The methyl ester resulted has a density of 0.89 g/mL, viscosity of 7.82 cSt, and dominated by a methyl oleate, methyl palmitate, and methyl stearate.

Optimization of Tunisian Olive Pomace Oil Esterification Using Response Surface Methodology

Several countries around the world are interested in the valorization of agricultural waste. Olive pomace oil is claimed to be a promising feedstock for biodiesel production. Alkaline transesterification is the most used method for biodiesel production, but the high amount of free fatty acids in feedstock prevents its occurrence. A pretreatment step, which is an acid esterification reaction, is necessary for the reduction of free fatty acids. The main purpose of this work is to optimize experimentally the olive pomace oil esterification using Response Surface Methodology (RSM) combined with the Central Composite Design (CCD). RSM was employed to study the relationships of reaction time, reaction temperature, methanol to oil molar ratio and catalyst concentration on olive pomace oil acidity. RSM predicted optimal conditions for esterification reaction. The oil acidity was reduced from 15 to 0.8 mg KOH g−1 with methanol to oil molar ratio 10.5:1, sulfuric acid 2.5%, reaction temperature 70 °C and reaction time 90 min. The quadratic term of temperature and catalyst concentration were the most significant effects while reaction time was not significant.