Esterification Of Citric Acid Research Articles

Study of Citric Acid-Locust Bean Gum as a Glidant to Fillers of Cellulose Derivatives

Citric acid-locust bean gum (CA-LBG) was introduced as an excipient in tablet preparations. CA-LBG is a compound derived from the esterification of citric acid (CA) with locust bean gum (LBG). The experiment aimed to determine the potential and effect of CA-LBG as a glidant on microcrystalline cellulose (MCC). The CA-LBG concentrations in the experiments were 0.5%, 1.0%, 2.0%, and 4.0%. Talc and magnesium stearate (MgS) as a comparison. The mixtures were evaluated for flow rate and angle of repose. The mixture was compressed into tablets weighing 700 mg. Tablets were evaluated for weight, hardness, and friability. The flow rate of the mixture containing CA-LBG 0.5%-4.0% was 12.77 g.sec-1-15.96 g.sec-1. The angle of repose of the mixture containing CA-LBG 0.5%-4.0% is 32.62○-35.52○. The weight of tablets containing CA-LBG 0.5%-4.0% is 700.0 mg-701.2 mg. The hardness of tablets containing CA-LBG 0.5%-4.0% is 6.30 kp-6.90 kp. The friability of tablets containing CA-LBG 0.5%-4.0% is 0.17%-0.36%. The CA-LBG has the potential as a glidant in MCC fillers. Increasing CA-LBG concentration causes the flow rate to increase, the angle of repose to decrease, and the hardness to increase. CA-LBG concentrations of 0.5% and 4.0% reduced tablet friability.

Effective and eco-friendly safe self-antimildew strategy to simultaneously improve the water resistance and bonding strength of starch-based adhesive

Starch adhesive, as a sustainable biomass-based adhesive, could be used to solve environmental problems from petroleum-derived adhesive. But its application is hindered by poor water resistance, mildew resistance, and storage stability. Here, a fully bio-based citric acid-starch adhesive (CASt) with high properties was successfully introduced by a simple method. Liquid chromatography/mass spectrometry (LC-MS), and Fourier Transform Infrared spectroscopy (FT-IR) determined that esterification of citric acid (CA) and starch (St) occurred to form a stable three-dimensional crosslinking structure, which strengthened water resistance and bonding strength of the starch adhesive. Compared with native starch (100 %), the soluble content of cured CASt was 1–16 %. CASt adhesive has well storage stability and high mildew resistance. Even after being stored for 5 months, the CASt-1 adhesive (mass ratio of CA/St = 1:1, and reaction time = 1 h) still have good liquidity. And its hot water strength (1.05 ± 0.22 MPa) also satisfied the standard requirements (≥0.7 MPa). The exhibited CASt adhesive is eco-friendly with components from plant resources, which performed as a bright alternative that can substitute petroleum-based adhesives in the artificial board industry.

Incorporation of Resveratrol in Polymeric Nanogel for Improvement of Its Protective Effects on Cellular and Microsomal Oxidative Stress Models.

Nanogels are attractive drug delivery systems that provide high loading capacity for drug molecules, improve their stability, and increase cellular uptake. Natural antioxidants, especially polyphenols such as resveratrol, are distinguished by low aqueous solubility, which hinders therapeutic activity. Thus, in the present study, resveratrol was incorporated into nanogel particles, aiming to improve its protective effects in vitro. The nanogel was prepared from natural substances via esterification of citric acid and pentane-1,2,5-triol. High encapsulation efficiency (94.5%) was achieved by applying the solvent evaporation method. Dynamic light scattering, atomic force microscopy, and transmission electron microscopy revealed that the resveratrol-loaded nanogel particles were spherical in shape with nanoscopic dimensions (220 nm). In vitro release tests showed that a complete release of resveratrol was achieved for 24 h, whereas at the same time the non-encapsulated drug was poorly dissolved. The protective effect of the encapsulated resveratrol against oxidative stress in fibroblast and neuroblastoma cells was significantly stronger compared to the non-encapsulated drug. Similarly, the protection in a model of iron/ascorbic acid-induced lipid peroxidation on rat liver and brain microsomes was higher with the encapsulated resveratrol. In conclusion, embedding resveratrol in this newly developed nanogel improved its biopharmaceutical properties and protective effects in oxidative stress models.

Features of triamyl citrate synthesis

Objectives. To find an effective way for obtaining triamyl citrate, an environmentally friendly, biodegradable citric acid ester used as a plasticizer for PVC-based polymer compositions.Methods. The possibilities of heterogeneous catalysis were analyzed using the case study of three commercial samples of macroporous sulfocationites (Amberlyst™ 15, Amberlyst™ 70, and TULSION® 66). Homogeneous catalysis was studied using the example of orthophosphoric acid (H3PO4), while self-catalysis was investigated during esterification of citric acid with amyl alcohol (ROH). The syntheses were carried out under identical conditions: T = 110 °C, the ratio of CA:ROH = 1:5 (mol) amount of catalyst 1 wt % on the reaction mass in a thermostatically controlled reactor of ideal mixing with continuous distillation of the resulting water.Results. It was found that in all variants (even under self-catalysis conditions), the conversion of citric acid in 180 min reached 94–99%. Triamyl citrate was formed after 9 h with a yield of 90% only when using a homogeneous catalyst (H3PO4) and in the presence of a heterogeneous catalyst sample (Amberlyst ™ 15).Conclusions. The revealed differences in the reactivity of the studied sulfocationites (Amberlyst™ 15, Amberlyst ™ 70, and TULSION® 66) confirm the well-known theoretical positions, according to which the kinetic pseudo-homogeneous model of the esterification process of hydroxy acids in excess of aliphatic alcohols is based on the law of acting masses and depends on the specific surface area of the catalyst, which for Amberlyst ™ 15 is of the greatest importance as compared to Amberlyst ™ 70 and TULSION® 66 (m2/g): 53:36:35, respectively.

Improved Esterification of Citric Acid and n-Butanol Using a Dense and Acid-Resistant Beta Zeolite Membrane.

In this work, a dense and acid-resistant beta zeolite membrane was applied to improve the esterification of citric acid and n-butanol, for the first time. Through the continuous removal of the by-product water via pervaporation (PV), the conversion of citric acid was significantly enhanced from 71.7% to 99.2% using p-Toluenesulfonic acid (PTSA) as catalyst. PTSA was a well-known strong acid, and the membrane kept almost no change after PV-esterification, indicating the superior acid resistance of beta zeolite membrane. Compared to the use of acid-resistant MOR zeolite membrane by PV-esterification, a consistently higher conversion of citric acid was obtained using a high-flux beta zeolite membrane. The results showed that high water permeation on the beta zeolite membrane, with good acid resistance, had a strong promoting effect on esterification, leading to an improved conversion. In addition, the citric acid conversion of 97.7% could still be achieved by PV-esterification at a low reaction temperature of 388 K.

Evaluation of Enhanced UV Protection Property of Dyed Cotton Fabrics Based on Inclusion Complex of β-cyclodextrin with Natural Coumarin Extracted from Cortex fraxini

Inclusion complex formed between β-cyclodextrin (β-CD) and natural coumarins extracted from Cortex fraxini were utilized to dye and enhancing the UV protection properties of cotton fabric. Natural coumarins were extracted from Cortex fraxini and the total amount of natural coumarins was evaluated. The inclusion complex of natural coumarins with β-CD were formed and analyzed by ultraviolet-visible spectrum, fluorescence spectroscopy, FTIR and TGA. The obtained results showed that a stoichiometry of 1:1 inclusion complex was formed and the fluorescence intensities and ultraviolet absorption of the natural coumarins were both enhanced by incorporating into β-CD. β-CD was grafted onto cotton fabric based on esterification of citric acid with cellulose and cyclodextrin in the presence of sodium hypophosphite. The grafted cotton fabric was then dyed with natural coumarins extraction of Cortex fraxini as natural ultraviolet absorbent to form stable inclusion complex. UV protection factor (UPF), UVA transmittance (TUVA) and UVB transmittance (TUVB), wrinkle recovery and tensile strength of dyed fabrics were evaluated and demonstrated that graft modification of fabrics with β-CD resulted enhancement in UV protection property and durability accompanied with increasing in wrinkle recovery properties and decreasing in tensile strength. Furthermore, apparent morphology, FTIR and TGA analysis of inclusion complexes loaded cotton fabrics and the relationship between structure and properties were investigated.

A Theoretical and Experimental Study on Esterification of Citric Acid with the Primary Alcohols and the Hydroxyl Groups of Cellulose Chain (n = 1-2) in Parched Condition

Esterification of citric acid (CA) with the primary alcohols and the hydroxyl groups of cellulose chain (n = 1-2) in parched condition were investigated by using density functional theory (DFT) method and a two-layer ONIOM approach. Geometry and energy of reactants, products, and transition state (TS) structures were optimized at B3LYP/6-311g (d, p) level and ONIOM (B3LYP/6-311g (d, p):PM3MM) level. The computational results show that the esterification occurs in the two main steps: the first step is the dehydration reaction of CA to form anhydrides of 5-membered ring and 6-membered ring and the second step is the ring opening reaction with the hydroxyl –OH groups to form the ester products. The energy barrier of dehydration reaction step is much higher than that of ring opening reaction step. Effect of substituent R in primary alcohol R-CH2OH (R: CH=CH2, CH2NHCH3, CH2OCH3, CH2Cl) and cellulose chain (1G, 2G) on the reactivity, which has negative inductive effect –I, is significant. The combination of calculation data and experiment data were applied to make findings more rigorous. The activation energy of CA was determined by using differential scanning calorimetry (DSC) and thermal gravimetric (TG) analysis to beEaexp = 47.8 kcal/mol; the experimental data favoured the dehydration reaction step of CA.

Homogeneous and Heterogeneous Catalytic Kinetics in the Production of Triethyl Citrate

This work deals with the determination of kinetic models for the esterification of citric acid with ethanol for the synthesis of triethyl citrate. Methanesulfonic acid (MSA) and an ion-exchange res...

Tributyl Citrate Production via Reactive Distillation—Conceptual Design and Pilot-Scale Validation

This work describes the conceptual design and a pilot scale validation of a reactive distillation column for tributyl citrate (TBC) production by esterification of citric acid (CA) with n-Butanol B...

IDENTIFICATION AND QUANTITATIVE DETERMINATION OF ESTERS OF CITRIC ACID

The necessity and possibility of creating a domestic technology for the production of citric acid esters - trialkyl citrates - effective and environmentally friendly plasticizing compositions based on renewable raw materials are substantiated. Trialkylcitrates a purity of 98-99% are obtained by azeotropic esterification of citric acid with aliphatic alcohols C4-C5 under conditions of homogeneous acid catalysis. Using the synthesis of triamyl citrate as an example, the esterification of a polybasic hydroxy acid has been considered. It was established that during the synthesis a complex mixture is formed consisting of unreacted citric acid, incomplete mono-, diesters and triamyl citrate. The influence of synthesis conditions (temperature, reagent ratio, catalyst amount and reaction time) on the composition of the reaction mass is shown. A method of gas chromatographic analysis of citric acid esters has been developed. Taking into account the structural features of citric acid and its partial esters containing polar carboxyl groups, the reaction mass was pre-methylated with synthesized diazomethane. The resulting mixture consists of six esters of citric acid: trimethylcitrate; 2-hydroxy-1,3-dicarboxymethyl-2-carboxyamylpropane; 2-hydroxy-1,2-dicarboxymethyl-3-carboxyamil propane; 2-hydroxy-1-carboxymethyl-2,3-dicarboxysamyl propane; 2-hydroxy-2-carboxymethyl-1,3-dicarboxyamyl propane; triamylcitrate. The analysis was performed on a chromatographic complex "Crystal-2000M" on a capillary column with a grafted non-polar phase OV-101, length 100 m. The analysis time ranged from 22 to 49.5 min. Empirical equations were obtained using the internal standard method (the standard is dicyclohexyl adipate) to determine the calibration coefficients of the starting (trimethyl citrate т citric acid) and final (triamyl citrate) products in a wide concentration range. The results of identification of structures of six esters of citric acid for which there is no information in existing databases are presented. The study was carried out by method of chromato-mass spectrometry on the instrument SHIMADZU GCMS – QP2010 with ionization by electron impact at ionization energy of 130 eV. The analysis of the obtained spectra made it possible to determine the most probable ways of fragmentation of organic molecules and the intensity of the peaks of the ions formed.

Modeling, analysis and multi-objective optimization of an industrial batch process for the production of tributyl citrate

This work describes the modeling and optimization of a trybutil citrate (TBC) production process at the industrial scale. The process comprises a batch reactive distillation for the esterification of citric acid with butanol. The dynamic model of the process was constructed based upon validated kinetic and thermodynamic models, implemented in gPROMSⓇ software, verified with industrial scale experiments, and used for further optimization to minimize batch time and energy consumption. Manipulated process variables were the molar ratio of butanol to citric acid, the alcohol loading policy, and the heat supply profile, and a Pareto front of optimal solutions was obtained. Depending on the main goal, the optimization process allowed to obtain energy savings up to 28%, and the corresponding processing times were reduced by 36%. Finally, multi-attribute utility theory (MAUT) approach was used as decision-making aid tool to select the preferred operating conditions for TBC production at the industrial scale.

Esterification of citric acid with locust bean gum

Esterification of citric acid (CA) with locust bean gum (LBG) was prepared by hydrochloric acid (HCl) as a catalyst and UV irradiation (254 nm) as esterification energy. This study aims to determine the best conditions of esterification. Other than that, it is to know the effect of amount HCl and UV irradiation time for the esterification process of CA with LBG. The amounts of HCl are 0.18 and 0.30 M, while the variations of UV irradiation time are 75 and 100 minutes. Polyester (CA-LBG) were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), esterification degree, and viscosity. Parameters for determining the best conditions for esterification are esterification degree and viscosity. The best conditions of esterification were obtained by using 0.30 M mL HCl and 100 minutes of UV irradiation time resulted in CA-LBG having a value of esterification degree 9.69 % and viscosity 7.46 cPs. HCl accelerates protonation on the O atoms and the formation of positive C atoms of carbonyl groups of citric acid. The time of UV irradiation gives the longer energy for the bond formation between the positive C atoms of the carbonyl group and the O atoms of the hydroxyl group at C-6 atoms of mannose and galactose.

Inversion dimers dominate the crystal packing in the structure of trimethyl citrate (trimethyl 2-hy-droxy-propane-1,2,3-tri-carboxyl-ate).

Trimethyl citrate, C9H14O7 (systematic name: trimethyl 2-hy-droxy-propane-1,2,3-tri-carboxyl-ate), 2, was prepared by the esterification of citric acid and methanol in the presence of thionyl chloride at 273 K. The bond lengths and angles in 2 compare closely with those observed in citric acid. The C-C bonds adjacent to the terminal carboxyl groups are significantly shorter than those around the central C atom. The central carboxyl-ate group and the hy-droxy group occur in the normal planar arrangement with an r.m.s. deviation of 0.0171 Å from the mean plane involving all six atoms in the central unit. The crystal structure is almost completely dominated by the formation of inversion dimers through an O-H⋯O hydrogen bond, together with an extensive array of weaker C-H⋯O contacts. These generate a three-dimensional network structure with mol-ecules stacked along the c-axis direction.

Phase Equilibrium Behavior in Mixtures Containing Tributyl Citrate, Citric Acid, Butan-1-ol, and Water

This work focused on the development of the phase equilibria models required to describe the behavior of mixtures involved in the synthesis of tributyl citrate (TBC) via esterification of citric acid (CA) and butan-1-ol (BuOH). Vapor–liquid equilibrium (VLE) for the mixture TBC–BuOH, liquid–liquid equilibrium (LLE) for the ternary mixture TBC–H2O–BuOH, and solubility data for the mixture CA–BuOH–TBC were measured at different temperatures. The thermodynamic consistency was verified with the Wisniak test for VLE data, and the LLE data exhibited linear behavior in an Othmer and Tobias plot. Anhydrous citric acid was characterized by differential scanning calorimetry exhibiting a melting point of 424.9 K, an enthalpy of fusion of 59.2 kJ/mol, an average heat capacity of 255.48 J/mol·K in the evaluated temperature range (320–375 K), and a change of heat capacity from solid to liquid of 236 J/mol·K. Together with reported equilibrium data from the open literature, and the evaluated physicochemical properties, the measured equilibrium data were regressed with the UNIQUAC equation to fit the binary interaction parameters of the components in the mixture. The obtained model agrees well with the whole set of experimental data and can be used for further process design.

Synthesis and Characterization of Diethyl Citrate and Phase Equilibria in Mixtures with Ethanol and Water

In this work, diethyl citrate (DEC) was synthesized and isolated for further physicochemical characterization and phase equilibria study. The synthesis was performed via partial esterification of citric acid with ethanol, and the final product was separated from the resulting mixture using a pH-controlled solvent extraction method. Characterization using 1H NMR and 13C NMR spectroscopy confirmed the presence of both DEC isomers with few impurities. Results indicate that a 6:5 molar ratio of the symmetric to the nonsymmetric ester structures was attained during synthesis. Thermogravimetric analysis and differential scanning calorimetry allowed us to measure, for the first time, glass transition temperature (228 K) and decomposition temperature (493 K) of diethyl citrate. Additionally, P–x data for the vapor–liquid equilibrium of the binary mixtures diethyl citrate + ethanol and diethyl citrate + water were collected at 308 K using an accurate dynamic device. Data were regressed to generate binary interacti...

Dibutyl Citrate Synthesis, Physicochemical Characterization, and Px Data in Mixtures with Butanol

Dibutyl citrate (DBC) was synthesized via partial esterification of citric acid (CA) with n-butanol (BuOH) and characterized for the first time. Then, the monoacid diester was isolated from the reactive mixture by using a pH-controlled solvent extraction procedure. The identity of the obtained product was verified by NMR spectroscopy, finding that it corresponds to a mixture of asymmetric and symmetric isomers. The obtained product was characterized by thermogravimetric and differential scanning calorimetry analysis and by density and viscosity measurements. As per the calorimetric analysis, DBC exhibited a crystallization point below 213 K, a decomposition temperature of 541 K, and an average heat capacity of 2.461 kJ/kg K in the evaluated temperature range (320–375 K). The average liquid density and viscosity in the studied temperature interval (298–313 K) were 1.122 g/cm3 and 2.03 Pa·s, respectively. Additionally, isothermal vapor–liquid equilibrium data (P–x) in mixtures containing the obtained DBC an...

Design of thermally coupled reactive distillation schemes for triethyl citrate production using economic and controllability criteria

This work describes a systematic process design for triethyl citrate production by direct esterification of citric acid with ethanol via simultaneous reaction-separation technologies. The design methodology includes simultaneous optimization of controllability and profitability criteria. With a novel approach, the conceptual feasibility analysis of the intensified processes was carried out by extending the reactive residue curve maps (RRCM) to mixtures with six components by implementing a substitution degree parameter. The RRCM have been also extended to the conceptual design of dividing wall columns. The configuration of both, traditional and dividing wall reactive distillation columns, were obtained from the conceptual analysis. The processes were simulated using experimentally validated models, and further optimized using a nature inspired multi-objective algorithm. A triethyl citrate production capacity of 10kTon/yr was used as process specification. Final designs evidenced citric acid conversions above 99.9%, energy consumption from 3-5MJ/kg, and a TEC production costs of c.a 1.5USD/kg. Controllability assessment was performed by evaluating the condition number of the proposed operating schemes. Pareto diagrams indicate that the minimization of total annual costs and controllability are conflicting goals in both production schemes. Nevertheless, both alternatives withstand large perturbations over the main process variables. The reactive dividing wall column scheme results in large energy and cost savings over a traditional reactive distillation process.

ESTERIFICATION OF CITRIC ACID WITH ALIPHATIC ALCOHOLS С<sub>2</sub>-С<sub>5</sub>

There is an ever increasing interest in the production and use of bio-based chemical substances for the preparation of polymeric materials designed to obtain children's toys, medical equipment and materials that are in contact with food. Trifunctional esters of citric acid - trialkyl citrates - obtained by esterification of citric acid with aliphatic alcohols C 2 -C 5 are of hazard class 4, good plasticizing ability, compatibility with the polymer, a high flash temperature. Citric acid (global production of 0.85-1 mtpa) is a readily available raw material obtained from the waste of sugar production. The purpose of the study is to develop a model of citric acid esterification with linear alcohols C 2 -C 5 in the presence of homogeneous acidic catalysts for the creation of a domestic technology for the synthesis of plasticizing compositions based on renewable raw materials. The selected catalyst is sulfuric acid. The correlation of reactivity of the aliphatic alcohols C 2 -C 5 with their structure in the esterification of citric acid was studied. Some kinetic parameters (lnk0, Ea) were estimated. Synthesis modes were proposed. The reaction time of the preparation of trialkyl citrates at 96% conversion of citric acid (t = 90 °C) was calculated. Laboratory samples were obtained and tested. Some operational characteristics were determined.

KINETIC OF ESTERIFICATION OF CITRIC ACID IN PRODUCTION OF TRIALKYL CITRATES

Polyvinyl chloride (PVC) is a body of a great many of composite materials and takes one of the leading places in thermoplastic polymers production capacity. Annual intake of PVC in the world (data of 2014 years) achieves to 35 mtpa. and has a consistent trend to further increase. PVC recycling is impossible without using of plasticizers. Nowdays scopes of use and plasticizers market used in the polymer materials production intended for contact with alimentary products, for medical equipment and children's toys production, are upon essential impact of policy statements of health, safety, security, environment. Plasticizers with citric acid – trialkyl citrates have needed properties: hazard class 4, high plasticize ability, full miscibility with polymer, high boiling and flash points, low volatility. The citric acid is available renewable raw produced from saccharified residues; world production volume is 1.6 mtpa. There are no local plasticizers production technologies with citric acid. Development of plasticizers production technologies with renewable raw material is relevant objective. Purpose of research is to create method of producing of trialkyl citrate, study of esterification regularities of citric acid with low molecular alcohol over different catalysts. In this research, the kinetic of performances of citric acid esterification by pentanol was estimated over different catalysts. Reaction orders were defined using three catalysts: sulphuric acid, orthophosphoric acid and p-toluene sulphonic acid. The rate constants and activation energies of esterification were found. Kinetic formulas were obtained. The time of esterification was defined to achieve 95 % conversion of citric acid. The time varies from 1.5 to 5 h depending on used catalyst. For citation:Sushkova S.V., Levanova S.V., Glazko I.L., Pavlova K.V. Kinetic of esterification of citric acid in production of trialkyl citrates. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N2. P. 74-78.

Sustainable Catalytic Process for Synthesis of Triethyl Citrate Plasticizer over Phosphonated USY Zeolite

Fruits wastage is harmful to health and environment concerning spreading diseases and soil pollution, respectively. To avoid this issue, use of citrus fruit waste for the production of citric acid (CA) is one of viable mean to obtain value added chemicals. Moreover, synthesis of triethyl citrate (TEC), a non-toxic plasticizer by esterification of CA with ethanol over heterogeneous catalyst would be renewable and sustainable catalytic process. In this context, parent Ultrastable Y (USY) and different percentage phosphonated USY (P-USY) zeolites were used for the synthesis of TEC in a closed batch reactor, for the first time. The synthesized catalysts were characterized by N2-adsorption desorption isotherm, powder X-ray diffraction (XRD) and NH3 temperature programmed desorption (TPD. Effect of reaction conditions, such as the molar ratio of ethanol to CA (5:1 - 20:1), the catalyst to CA ratio (0.05 - 0.25) and reaction temperature (363-403 K), were studied in view to maximizing CA conversion and TEC yield. Phosphonated USY catalysts were found to be superior in activity (CA conversion and TEC yield) than parent USY, which is attributed to the increased in total acidity with phosphonation. Among the studied catalysts, the P2USY (2% phosphorous loaded on USY) was found to be an optimum catalyst with 99% CA conversion and 82% TEC yield, which is higher than the reported values. This study opens new avenues of research demonstrating principles of green chemistry such as easy separable and reusable catalyst, non-toxic product, bio-renewable synthetic route, milder operating parameters and waste minimization.