Equilibrium Constant Of Reaction Research Articles

Development of a consistent geochemical model of the Mg(OH)2–MgCl2–H2O system from 25°C to 120°C

The formation of magnesium chloride-hydroxide salts (magnesium hydroxychlorides) has implications for many geochemical processes and technical applications. For this reason, a thermodynamic database for evaluating the Mg(OH)2–MgCl2–H2O ternary system from 0 °C–120 °C has been developed based on extensive experimental solubility data. Internally consistent sets of standard thermodynamic parameters (ΔGf°, ΔHf°, S°, and CP) were derived for several solid phases: 3 Mg(OH)2:MgCl2:8H2O, 9 Mg(OH)2:MgCl2:4H2O, 2 Mg(OH)2:MgCl2:4H2O, 2 Mg(OH)2:MgCl2: 2H2O(s), brucite (Mg(OH)2), bischofite (MgCl2:6H2O), and MgCl2:4H2O. First, estimated values for the thermodynamic parameters were derived using a component addition method. These parameters were combined with standard thermodynamic data for Mg2+(aq) consistent with CODATA (Cox et al., 1989) to generate temperature-dependent Gibbs energies for the dissolution reactions of the solid phases. These data, in combination with values for MgOH+(aq) updated to be consistent with Mg2+-CODATA, were used to compute equilibrium constants and incorporated into a Pitzer thermodynamic database for concentrated electrolyte solutions. Phase solubility diagrams were constructed as a function of temperature and magnesium chloride concentration for comparisons with available experimental data. To improve the fits to the experimental data, reaction equilibrium constants for the Mg-bearing mineral phases, the binary Pitzer parameters for the MgOH+ — Cl− interaction, and the temperature-dependent coefficients for those Pitzer parameters were constrained by experimental phase boundaries and to match phase solubilities. These parameter adjustments resulted in an updated set of standard thermodynamic data and associated temperature-dependent functions. The resulting database has direct applications to investigations of magnesia cement formation and leaching, chemical barrier interactions related to disposition of heat-generating nuclear waste, and evaluation of magnesium-rich salt and brine stabilities at elevated temperatures.

Absorption characteristics and molecular mechanism of a low viscosity iron-based ionic liquid for removing H2S

Aiming at the problem of by-product salt and volatile solvent component in industrial liquid redox process of H2S removal. A new absorbent, a 1-butyl-3-methylpyridine iron-based ionic liquid (rFeCl3/[BMP]Cl) with three iron-pyridine ratios (r=0.6, 0.8, and 1.0), was synthesized. The physicochemical properties and H2S solubility of rFeCl3/[BMP]Cl were measured and modeled. The molecular mechanism of chemical absorption of H2S by iron-based ionic liquids was explained from the interaction energy, reduced density gradient (RDG) and atoms in molecules (AIM) topology analysis, and standard reaction equilibrium constant by quantum chemical calculation. It was found that rFeCl3/[BMP]Cl have low viscosity, high solubility, and good thermal stability. Its Bronsted acidity avoids by-product salts produced in the absorption of H2S. The hydrophobicity makes the ionic liquid not diluted by the generated water during the absorption. The results of quantum chemical calculations show that rFeCl3/[BMP]Cl-H2S has moderate intermolecular interaction and large reactivity, which is consistent with the experimental results of the Henry's coefficient and reaction equilibrium constant.

Investigation of effective CO2 capture by ternary deep eutectic solvents based on superbase

The absorption and separation of CO2 is one of the main strategies to reduce carbon emissions and mitigate global climate change. In this context, a series of ternary superbase/betaine-based deep eutectic solvents (DESs) were synthesized to capture CO2, and their density, viscosity and thermal stability were investigated. The effects of temperature, pressure, different hydrogen bond donors (HBDs) and alkalinity of the superbase on their CO2 affinity were evaluated by the isovolumetric saturation method. The uptake of CO2 by the DES synthesized from betaine, 1,2-propanediol and 1,8-diazabicyclo(5.4.0)undec-7-ene reached a maximum of 1.5071 mol·kg−1 at 303.15 K and a pressure of 0.187 MPa. The simultaneous chemical and physical adsorption of CO2 by the ternary DESs was verified by FTIR spectroscopy, and the absorption mechanism was also proposed. The reaction equilibrium thermodynamic model (RETM) was improved to obtain the “Active DES” model, which was correlated with the experimentally determined CO2 solubility. The reaction equilibrium constants and Henry's law constants were obtained for each ternary system. The ternary superbase/betaine DESs proposed in this paper are green, economical and high-performance absorbers for capturing CO2.

Glycerol 3-Phosphate Dehydrogenase: Role of the Protein Conformational Change in Activation of a Readily Reversible Enzyme-Catalyzed Hydride Transfer Reaction.

Kinetic parameters are reported for glycerol 3-phosphate dehydrogenase (GPDH)-catalyzed hydride transfer from the whole substrate glycerol 3-phosphate (G3P) or truncated substrate ethylene glycol (EtG) to NAD, and for activation of the hydride transfer reaction of EtG by phosphite dianion. These kinetic parameters were combined with parameters for enzyme-catalyzed hydride transfer in the microscopic reverse direction to give the reaction equilibrium constants Keq. Hydride transfer from G3P is favored in comparison to EtG because the carbonyl product of the former reaction is stabilized by hyperconjugative electron donation from the -CH2R keto substituent. The kinetic data show that the phosphite dianion provides the same 7.6 ± 0.1 kcal/mol stabilization of the transition states for enzyme-catalyzed reactions in the forward [reduction of NAD by EtG] and reverse [oxidation of NADH by glycolaldehyde] directions. The experimental evidence that supports a role for phosphite dianion in stabilizing the active closed form of the GPDH (EC) relative to the ca. 6 kcal/mol more unstable open form (EO) is summarized.

Scaling towards the critical point in the combined reaction/Gibbs ensemble

We explore the impact of force field parameters and reaction equilibrium on the scaling behavior towards the critical point in reactive binary systems, focusing on NO2/N2O4. This system can be considered as a special single-component system since NO2 and N2O4 are in chemical equilibrium via the chemical reaction 2NO2⇌N2O4. We simplify the system by representing both components as single LJ particles, achieving excellent agreement with densities computed using molecular simulations in which all-atom force fields were used. We investigate the effect of force field parameters (ɛ and σ) on phase behavior and show that the critical exponent β remains constant, which means that intermolecular interactions do not affect the scaling to the critical point when the chemical reaction takes place. We also investigate the sensitivity of the reaction equilibrium constant and show that even small changes in isolated molecule partition functions lead to large differences in chemical equilibria. We show that the critical exponent β is different for systems with different reaction equilibrium constants, so a careful parameterization of β is needed for an accurate computation of critical temperatures of reactive mixtures. We perform a screening of reactive binary mixtures for a wide range of ideal gas reaction equilibrium constants, revealing key insights into the thermodynamic behavior and critical properties. Thereby we facilitate the efficient screening of reactive binary mixtures for various applications. Our results emphasize the importance of accurately parameterizing β and provide valuable insights into the critical scaling behavior of complex reactive systems.

Analytical Form of the Fluorescence Correlation Spectroscopy Autocorrelation Function in Chemically Reactive Systems.

Fluorescence correlation spectroscopy (FCS) applied to chemically reactive systems provides information about chemical reaction equilibrium constants and diffusion coefficients of reactants. These physical quantities are determined from the FCS-measured autocorrelation function, G(t), as a function of time, t. In most of the studied cases, the analytical form of G(t) is well-known for reactions that are much faster than the diffusion time of reactants across the focal volume probed by FCS or when they are much slower than the diffusion time. Here, we develop an analytical form of G(t) for reactions occurring at an intermediate time scale comparable to the diffusion time. G(t) depends on the reaction rates in such reactions. We focus on reversibly binding a fluorescently labeled small molecule to a macromolecule in a diluted solution in thermodynamic equilibrium. Our approach allows the analysis of FCS data over a wide range of diffusion coefficients, reaction rate constants, and brightness levels of fluorescent labels. Our G(t) is valid even when the fluorescent label changes its brightness upon binding. The easy-to-implement analytical form of the autocorrelation function greatly helps experimentalists study chemical reactions, determining the equilibrium constants of reactions and the reaction rates.

Moment Analysis Method for Measurement of Reaction Equilibrium and Rate Constants by Using High-Performance Liquid Chromatography.

The moment analysis method was developed for the determination of association equilibrium constant (KA) and association (ka) and dissociation (kd) rate constants of intermolecular interactions between solute and ligand molecules. They are accurately determined by using moment equations from elution peak profiles because they are measured by using high-performance liquid chromatography (HPLC) under preferable conditions that neither immobilization nor chemical modification (i.e., fluorescence labeling) of solute and ligand molecules is required. To demonstrate the effectiveness of the method, it was applied to the inclusion complex formation system between dibenzo-18-crown-6 (DB18C6) and alkaline earth metal cations, i.e., Mg2+, Ca2+, and Sr2+, as a concrete example. Because the diameter of the three metal cations is smaller than that of the inner cavity of DB18C6, the values of KA, ka, and kd were analytically determined by assuming the stoichiometry of 1:1 between DB18C6 and the metal cation. They reflected the influence of the difference in the size between the inner cavity of DB18C6 and the metal cations on the inclusion complex formation. It seems that the moment analysis method based on HPLC separation is effective for the multifaceted analysis of chemical reactions because some characteristics of the method are different from those of other conventional methods. It must contribute to the dissemination of an opportunity for the study of chemical reactions to many researchers because of the versatility of HPLC.

Reversible O-H Bond Activation by Tripodal tris(Nitroxide) Aluminum and Gallium Complexes.

Herein, we report the preparation and characterization of the Group 13 metal complexes of a tripodal tris(nitroxide)-based ligand, designated (TriNOx3-)M (M = Al (1), Ga (2), In (3)). Complexes 1 and 2 both activate the O-H bond of a range of alcohols spanning a ∼10 pKa unit range via an element-ligand cooperative pathway to afford the zwitterionic complexes (HTriNOx2-)M-OR. Structures of these alcohol adduct products are discussed. We demonstrate that the thermodynamic and kinetic aspects of the reactions are both influenced by the identity of the metal, with 1 having higher reaction equilibrium constants and proceeding at a faster rate relative to 2 for any given alcohol. These parameters are also influenced by the pKa of the alcohol, with more acidic alcohols reacting both to more completion and faster than their less acidic counterparts. Possible mechanistic pathways for the O-H activation are discussed.

Electron transport and thermoelectric properties in (Pb,Ho)-modified Ca0.5Sr0.5MnO3−δ manganites with perovskite-type structure

Doped calcium manganite perovskites CaMnO3−δ which constitute some of the most promising materials for all-oxide thermoelectric generators for conversion of heat to electricity operating in air over a wide temperature range have been modified by Sr–Pb–Ho co-doping. The Ca0.5Sr0.45−xPb0.05HoxMnO3−δ samples (x = 0.05, 0.10, 0.15 and 0.20) synthesized by the citrate-nitrate method of precursor preparation are shown to have an orthorhombic crystal structure (space group Pbnm) at room temperature. The relationship between temperature, concentration of donor ions, Jahn-Teller distortions and energy parameters of carrier formation and mobility that affect the thermoelectric properties of electron-doped manganites has been studied. The temperature-activated nature of the electrical conductivity (σ) was revealed to be consistent with the adiabatic mechanism of small-radius polaron transport. The increase in the absolute values of the Seebeck coefficient (S) with rising temperature and the decrease in σ above 500 K are attributed to the decrease in the concentration of Mn3+ ions due to their disproportionation into Mn2+ and Mn4+ ions. The equilibrium constants of the disproportionation reaction, carrier concentration and mobility have been derived from the temperature dependencies of S(T) and σ(T) in the conditions when δ ≈ 0. The best values of power factor (S2σ) and dimensionless thermoelectric figure-of-merit (ZT = S2σT/κ) have been found at the substitution level x = 0.15.

Chemical stability of Pb[(UO2)2O2(OH)2](H2O) and Pb2[(UO2)5O6(OH)2](H2O)2 compounds in aqueous solutions

The chemical stability of Pb[(UO2)2O2(OH)2](H2O) and Pb2[(UO2)5O6(OH)2](H2O)2 compounds in aqueous solutions was studied. The acid-base boundaries of the existence of these compounds in aqueous solutions were established, the hydrolysis products were identified, and the solubility was determined. Based on the data obtained, the equilibrium constants of dissolution reactions, the Gibbs functions of the formation and dissolution of Pb[(UO2)2O2(OH)2](H2O) and Pb2[(UO2)5O6(OH)2](H2O)2, were calculated, the solubility curves of the compounds under study, and the phase diagrams of U(VI) and Pb(II) in saturated aqueous solutions and in equilibrium solid phases were calculated.

The oxidation state of titanium in silicate melts

Titanium occurs as Ti3+, in addition to the more usual Ti4+, in extraterrestrial materials such as Lunar basalts and chondritic meteorites. The proportion of Ti as Ti3+ was investigated by Ti K-edge X-ray absorption near edge structure (XANES) spectroscopy for five silicate glass compositions quenched from melts equilibrated at 1400 °C, atmospheric pressure, and oxygen fugacities (fO2) in log units relative to the fayalite-magnetite-quartz (FMQ) buffer from FMQ+3.3 to FMQ-10.2 (+6.6 to −6.9 log units relative to the iron-wüstite, IW, buffer). All spectra could be well fit using a linear combination of the spectra recorded from the most oxidised and reduced samples of the same composition, indicating that the samples only contain two Ti species. Ti3+/ΣTi (where ΣTi = Ti3+ + Ti4+) = 0 for the most oxidised samples but is unknown for the most reduced. Thus, the linear combination fit results were used in a regression model in which Ti3+/ΣTi of the reduced end-member was varied to give Ti3+/ΣTi values of the other samples that best fit the thermodynamically expected dependence of Ti3+/ΣTi on fO2. The most reduced samples were found to have Ti3+/ΣTi ∼ 0.6. The resulting modified equilibrium constants of the Ti oxidation reaction, logK', are linearly correlated with the optical basicity (Λ) parameterisation of melt composition, such that as Λ increases, Ti3+/ΣTi decreases, at constant fO2. This correlation allows Ti3+/ΣTi to be predicted for other compositions and, assuming that the temperature dependence of Ti3+/Ti4+ is parallel to FMQ, a general equation relating Ti3+/Ti4+ to fO2 was obtained: log(Ti3+/Ti4+) = −0.25ΔFMQ − 0.32(19) − 3.44(32)Λ. This equation was used to predict Ti3+/ΣTi as a function of fO2 for high-Ti Mare basalt, chondrule (CV and CM), and calcium aluminium inclusion (CAI; Type A and B) compositions. For melts of these compositions Ti3+ = Ti4+ at ∼ FMQ-10.8, −9.5, −9.3, −10.6, and −10.2 (∼IW-7.5, −6.2, −6.0, −7.3, and −6.9), respectively, independent of temperature.

Solvent extraction and recovery of beryllium from hydrochloric acid solution with naphthenic acid

Beryllium is an essential metal for strategic purposes but remains an under-explored element. The separation of beryllium and aluminium and the purification of beryllium hydroxide from a multi-component solution has always been a challenging task in the beryllium industry and offers great research potential in academic fields. In this research, a solvent extraction method was used to purify and recover beryllium from trace impurities. A systematic investigation of the extraction process revealed that under optimal conditions, 98.66% of the beryllium was extracted in a three-stage countercurrent extraction using naphthenic acid (NA) as the extractant. The aluminium, iron and other trace impurities in the organic phase can be scrubbed with 1 mol/L HCl, then 99.27% of the beryllium was stripped with 5 mol/L NaOH by two-stage stripping. Be(OH)2 with a purity of 99.67% was recovered from the stripped beryllium solution by hydrolysis precipitation method. Furthermore, FT-IR analysis and slope analysis demonstrate the mechanism of beryllium extraction with naphthenic acid accompanied by cation exchange. The influence of temperature on the beryllium extraction was investigated and the thermodynamic parameters and the equilibrium constant of the extraction reaction were calculated. Accordingly, a process flowsheet for the separation of beryllium from multiple impurities using naphthenic acid was developed. This process is believed to offer the advantages of high efficiency, recyclability, and a favorable beryllium-aluminium separation effect; presenting a promising new approach to beryllium recovery.

Electrodeposition of Fe-Ni Alloy Films having Invar Compositions with Fe3+ as the Sole Iron Source

Fe-Ni alloy films with invar alloy compositions were electrodeposited from a stable citrate bath containing trivalent iron ions (Fe3+) as the sole iron source. This bath was prepared based on determining the equilibrium constants for acid dissociation, complex formation and precipitation reactions. Electrodeposition was conducted under galvanostatic conditions at 25 °C without agitation and an investigation was carried out into the effects of pH and current density on the composition and microstructure of the films. The results showed that ferric hydroxide (Fe(OH)3), which is normally poorly soluble, did not precipitate after electrodeposition. Fe-Ni alloy films containing 31‒42 mass% Ni (including Fe-36 mass% Ni) were formed with a current efficiency of approximately 70%. The films were smooth and were made up of grains with sub-micron sizes, although some cracks were observed. Fe and Ni were distributed homogeneously throughout the films and the Fe-Ni solid solutions exhibited both face-centered cubic and body-centered cubic structures.

Kinetics, equilibrium, and computational study on the monomerization reaction of {CH3ReVO(pdt)}2 dimer with monodentate ligands

The monomerization reaction of {MeReO(pdt)}2 dimer (the pdt is 1,3-propanedithiolate) with monodentate ligand has been studied experimentally:{MeReO(pdt)} + 2 L ⇌ 2 MeReO(pdt)L and L is a monodentate ligand presented in Figure 1. No monomerization reaction have been observed with the indazole and diphenyl sulfides, and 2-methylpyridne. For the 2-methylpyridne case, the no reaction was observed because of the steric effect of the methyl group at the ortho position prevent the nitrogen from coordination. But the phosphines and pyridines derivatives monomerize the dimer. The rate law is given by ν = (ka[L] + kb [L]2) {MeReO(pdt)2} for ligands 1 to 4 in Table 1 and the rate law is ν = kb [L]2 {MeReO(pdt)2} for ligands 6 to 8 in Table 1. The equilibrium constant of the same reaction has been also evaluated. The rate constant (k) and the equilibrium constant (Keq) values correlate well with the basicity of the ligand. The reaction constant (ρ) is -4.9 and -1.3 for pyridine and phosphine, respectively, obtained from Hammett correlation with σ. The computational study on I1 and I2 intermediates (Scheme 3) shows that these intermediates are not plausible intermediates as previously proposed1, 2. These results are attributed to the high angle strain on the bridging sulfur that prevent the formation of the I1 and I2 intermediates and the reaction proceed through different intermediates (I3 and Ia Scheme 4). Therefore, the proposed mechanism is modified to accommodate the computational results.

Fundamental Determinants of the Accuracy of Equilibrium Constants for Affinity Complexes.

The equilibrium constant of a chemical reaction is arguably the key thermodynamic parameter in chemistry; we naturally expect that equilibrium constants are determined accurately. The majority of equilibrium constants determined today are those of binding reactions that form affinity complexes, such as protein-protein, protein-DNA, and protein-small molecule. There is growing awareness that the determination of equilibrium constants for highly stable affinity complexes may be very inaccurate. However, fundamental (i.e., method-independent) determinants of accuracy are poorly understood. Here, we present a study that explicitly shows what the accuracy of equilibrium constants of affinity complexes depends on. This study reveals the critical importance of the choice of concentration of interacting components and creates a theoretical foundation for improving the accuracy of the equilibrium constants. The predicted influence of concentrations on accuracy was confirmed experimentally. The results of this fundamental study provide instructive guidance for experimentalists independently on the method they use.

Virtual undergraduate chemical engineering labs based on density functional theory calculations

Abstract Offering virtual laboratories to chemical engineering students is likely to extend beyond the COVID-19 era. Thus, there is a need to develop more simulation-based tasks in a wide blend of subjects, spanning thermodynamics, chemical reactions, and unit operations. Molecular and material modeling based on density functional theory (DFT) calculations provides limitless opportunities to train students on how to obtain thermokinetic values that are typically measured experimentally. Through a series of illustrative cases, this contribution provides detailed procedures pertinent to calculating reaction rate constants, standard enthalpies of reactions, redox potentials, equilibrium reaction constants, and surface-assisted mechanisms. We hope that DFT-operated virtual labs will assist students in attaining learning outcomes and promote their self-learning in the above-mentioned subjects. From a broader prospective, the presented case studies are expected to encourage students to appreciate the practical applications of DFT, not only in the academic but also in the industrial domains.

Catalytic effect of high thermal conductive SiC on the kinetics and thermodynamics of vulcanization reaction of SBR/BR-filled nano-SiC

Nano-silicon carbide (SiC) as a high thermal conductive material with an intrinsic thermal conductivity of ~ 490 W/m K was used to improve the cure characteristics, kinetics, and thermodynamics of curing reaction of styrene-butadiene rubber/butadiene rubber (SBR/BR) compounds. The considerations were carried out by non-isothermal differential scanning calorimetry (DSC). Results revealed that the presence of SiC shifted the peak and end temperatures of the curing peak to lower temperatures. The calculated activation energy of the curing reaction based on the Kissinger approach showed a descent from 409.8 to 93.8 kJ/mol by adding SiC from 0 to 7.5 phr (part per hundred rubber). Moreover, the obtained Gibbs free energy variation and equilibrium constant of the curing reaction proved that the reaction was absolutely forced and irreversible, which can be increasingly characterized as a one-way process. According to the results, SiC accelerated the curing reaction because of the increment of heat transfer into the compound. This phenomenon caused the increment of enthalpy variation of the vulcanization reaction, particularly at the SiC content of 5 phr. The achieved kinetic parameters via fitting an autocatalytic model based on the Sestàk–Berggren model by the Màlek method to describe the kinetics of the curing reaction indicated that the SiC filler had a catalytic effect on the curing reaction of SBR/BR-SiC, particularly after 2.5 phr of the filler.

Understanding fluoride adsorption from groundwater by alumina modified with alum using PHREEQC surface complexation model

Fluoride is recognized as a vital ion for human and animal growth because of the critical role it plays in preventing skeletal and dental problems. However, when it is ingested at a higher concentration it can cause demineralization of teeth and bones resulting in fluorosis, therefore, the production of high-adsorptive capacity material which is also cost-effective is necessary for the treatment of fluorides. In this study, aluminium foil is valorised into alumina nanoparticles. The as-prepared alumina was modified with alum in two different ratios of 1:0.5 and 1:1 (alumina to alum w/w%) and later used as adsorbents for the removal of fluoride from groundwater. The adsorbents were characterized by Fourier transform infrared spectroscopy, point of zero charge and X-ray diffraction. Different factors that influence the removal efficiency of fluorides such as pH, initial concentrations, contact time and adsorbent dosage were studied and optimized using a simulated fluoride solution. The optimum conditions obtained were used to test real groundwater. The static experiment conditions were used to calibrate a PHREEQC geochemical model which was later used to simulate the fluoride sorption onto the modified alumina at different conditions. PHREEQC was also coupled with parameter estimation software to determine equilibrium constants for the surface reactions between the fluoride species and the adsorbent in a way that the simulations accurately reflect the outcomes of laboratory experiments. Isotherm studies were carried out on the adsorbents. Both Langmuir and Freundlich's non-linear models fitted well for the equilibrium data. However, with a higher coefficient of regression and low chi-square test values, the adsorption process was more of chemisorption on a monolayer surface. Kinetic studies were also carried out by using the non-linear equations from the pseudo-first-order and pseudo-second-order models. The pseudo-second-order model fitted well for the equilibrium data. The mechanism for the fluoride ion adsorption was also studied by the intraparticle (IP) diffusion model and was found that IP was not the rate-determining factor, and therefore the most plausible mechanism for the sorption process was ion exchange or attraction of fluoride ions to the sorbent surface. The findings obtained from this research show that readily available aluminium waste could be valorised into a useful product that could be employed in the removal of fluoride from water samples, including groundwater, that may contain too much fluoride and pose a risk to the general public's health.

Comprehensive analysis of thermodynamic models for CO2 absorption into a blended N,N‐diethylethanolamine‐1,6‐hexamethyl diamine (DEEA‐HMDA) amine

AbstractIn this work, CO2 equilibrium solubility of 1M N,N‐diethylethanolamine (DEEA):2M 1,6‐hexamethyl diamine (HMDA), 1.5M DEEA:1.5M HMDA and 2M DEEA:1M HMDA was studied with a temperature range of 298–333 K and CO2 partial pressure range of 8–100 kPa. Seven thermodynamic models including Empirical model, Kent and Eisenberg (KE) model, Hu–Chakma model, Austgen model, Helei Liu model, Liu et al. model, and Li–Shen model were developed by correlating reaction equilibrium constants with observed equilibrium solubility of CO2 in mixed amine solvents. The evaluation of those models was conducted in terms of the average absolute relative deviation (AARD). The results indicated that Liu et al. model considering T, [Amine], Ptotal and [CO2(aq)] can better represent this complex system with an AARD of 8.06%. Meanwhile, comprehensive comparison and analysis were also performed to identify the contribution of parameters to develop models, which could provide a guideline for the development of accurate thermodynamic models for representation of thermodynamic behaviors.

REACTION KINETICS OF ACETIC ACID WITH ETHANOL TO ETHYL ACETATE WITH SULFURIC ACID CATALYST

Ethyl acetate is an ester of ethanol and acetic acid. This compound is a colorless liquid with a characteristic odor. Ethyl acetate is widely used as a solvent because of its high solubility. The manufacture of ethyl acetate (ethyl ester) is referred to as the esterification process. This esterification reaction is an exothermic reaction, is reversible and generally runs very slowly so it requires a catalyst to obtain maximum ester. Domestic demand for ethyl acetate is increasing, while production in Indonesia is still lacking. Reactor design requires a reaction mechanism and kinetic data in the form of reaction rate equations and reaction rate constants. This study aims to determine the kinetics of the etherification of acetic acid presented in the form of the reaction rate equation, the value of the reaction rate constant, and the reaction equilibrium constant. In addition, this research also studied how the influence of sulfuric acid catalyst on the reaction rate constant and the reaction balance. The esterification reaction was carried out in a batch reactor. 99% acetic acid and H2SO4 catalyst whose concentrations are varied, are mixed in a reactor equipped with a magnetic stirrer which is operated at 400 rpm, then 96% ethanol is poured with a volume ratio of 1:1 to acetic acid, 5 mL of sample is taken to analyze the remaining acid after The reaction takes place, every certain time interval a sample is taken to be analyzed until an equilibrium point is obtained. From the results of this study it can be concluded that the esterification reaction of acetic acid with ethanol to produce ethyl acetate is a second order reaction with the reaction rate equation (-rA) = k1CACB – k2CCCD. By using a reaction temperature of 34oC and a stirring speed of 400 rpm, the best conditions were obtained using a catalyst of 5.3% by volume, with the reaction rate constant to the right (k1) being 0.014 L/(gmol min), the value of the equilibrium constant (K=k1/k2) is 5.51 and the balance conversion is 77%.