Gibbs Energy Of Activation Research Articles

Excess properties, intermolecular interaction, and CO2 capture performance of diethylene glycol monomethyl ether + ethylenediamine binary mixed solutions

In this work, the density (ρ) and viscosity (η) values of diethylene glycol monomethyl ether (DEGME) (1) + ethylenediamine (EDA) (2) binary mixed solutions were experimentally measured over the temperature span of 298.15–318.15 K and at a constant pressure of 100.5 kPa. To delve into the physicochemical properties of the binary mixed solutions, the excess properties, including excess molar volume, viscosity deviation, and excess molar activation Gibbs free energy, and thermodynamic values, including activation Gibbs free energy, enthalpy change, entropy change, and activation energy, were systemically calculated. Furthermore, the relationship between mole fraction and temperature was modeled using the Jouyban-Acree (J-A) model and a least squares method. Additionally, the three-body McAllister, the four-body McAllister, the Eyring-Margules, and the Heric viscosity models were employed to establish a relationship between viscosity and mole fraction. The relationship between viscosity and temperature was determined utilizing the Arrhenius equation, and the Redlich-Kister (R-K) polynomial was applied to fit the excess molar volume, viscosity deviation, and excess molar activation Gibbs free energy values of the binary mixed solutions. To further validate the intermolecular interactions within the binary mixed solutions, Raman, UV, and 1H NMR spectroscopic analyses, and density-functional theory (DFT) calculations were also conducted. These comprehensive analyses collectively confirmed the presence of significant intermolecular hydrogen bonds (IHBs) between the DEGME and EDA molecules, which are characterized as the –OH⋯NH2– interaction. Ultimately, the CO2 absorption capacity of the binary mixed solutions was examined, revealing that diethylene glycol monomethyl ether (DEGME) (1) + ethylenediamine (EDA) (2) binary mixed solutions owned superior CO2 absorption efficiency, thus offering a promising approach for CO2 capture.

High-Level Calculation for Assessing the Atmospheric Reactivity of Pentachlorophenol with Hydroxyl Radical: Mechanism and Kinetics.

This work aims to investigate the reactivity of the pentachlorophenol (PCP) compound, C6Cl5OH, with a hydroxyl (OH) radical in the gas phase. Geometry optimizations and vibrational frequency calculations were performed using DFT-M06-2X/6-311++G(d,p). Single-point energy calculations were carried out using the single-reference coupled cluster method, specifically CCSD(T), and the multiconfigurational CASPT2 level of theory to characterize the atmospheric degradation processes of PCP with OH radicals and to identify which chemical species resulting from their decomposition could remain in the gas phase. The performance of various families of basis sets was tested. The widely used augmented-correlation-consistent basis set family aug-cc-pVXZ-DK (X = D, T, and Q) was compared to the atomic natural orbital basis sets ANO-RCC-VXZP (X = D, T, and Q). The energy profile at 298 K showed that the Cl- and OH-abstractions are not energetically favorable. H-abstraction and OH-addition/Ck (k = 1-6) are characterized by the lowest Gibbs energies of activation and are strongly exothermic. The canonical transition state theory (TST) with a simple Wigner tunneling correction is used to predict the rate constants over the 220-400 K temperature range for each reaction channel. The overall rate constant at 298 K based on our calculations is about 3.25 × 10-13, 3.10 × 10-15, and 2.21 × 10-15 cm3 molecule-1 s-1 at M06-2X, CASPT2/ANO-RCC-VQZP, and CASPT2/aug-cc-pVQZ-DK levels of theory, respectively. The PCP atmospheric lifetime at 298 K is predicted to be in the range from 1 to 12-16 years at 0 km in the presence of variable OH concentration (9.00 × 105 to 1.50 × 107 molecules cm-3) based on CASPT2 data.

Syntheses, Structures, and Thermal Decomposition Kinetics of Two Silver/Copper‐Based Coordination Compounds with 1,2,4‐Triazole‐Containing Ligand

AbstractIn this work, two silver/copper‐based coordination compounds {[Ag(tty)]⋅NO3}n (1) and {[Cu2Cl2(tty)2(H2O)2]⋅Cl⋅NO3 ⋅ (H2O)2}n (2) (tty=1,2,4,5‐tetra(1H‐1,2,4‐triazol‐1‐yl))benzen), were synthesized using the different metal salts under the hydrothermal condition. Structural analyses show that compound 1 features tilted L‐shaped 1D Ag chains structure and compound 2 presents a 2D layer with free Cl−, NO3− and water molecules. The experimental results reveal that 1 displays considerably high thermal stability with the thermal decomposition temperature above 337 °C compared to compound 2, which further exemplifies that the framework structures may have a crucial effect on the resultant thermal stability. Additionally, the non‐isothermal kinetics parameters were evaluated at different heating rates by Kissinger's and Ozawa‐Doyle's methods. Importantly, the kinetic triplets (the apparent activation energy (Ea), the preexponential factor (logA) and the mechanism function (ƒ(α)) and the related thermodynamic parameters (the Gibbs energy of activation, ▵G≠, the enthalpy of activation, ▵H≠, and the entropy of activation, ▵S≠) of the thermal decomposition processes are discussed and calculated in detail.

The origin of selectivity in the trimerization of 1,3-cyclopentadiene from an activation strain perspective.

Quantum chemical modeling (DFT-PBE0/cc-pVTZ) of the [4 + 2]-cycloaddition reaction of 1,3-cyclopentadiene (CPD) to (exo/endo)-dicyclopentadiene (DCPD) was carried out, resulting in 14 products-CPD trimers. According to calculations, exo-addition of CPD to the norbornene (NB) fragment of DCPD and trans-addition of CPD to the cyclopentene (CP) fragment of DCPD are kinetically preferred. Ring strain energies ERS were calculated for all trimers using the homodesmotic reaction approach. The least strained trimers are formed by exo-addition of CPD to the NB fragment of exo-DCPD, while the most strained ones are formed by endo-addition of CPD to the NB fragment of endo-DCPD. ERS values are in good agreement with thermodynamic stability of trimers. Analysis of activation energy using the activation strain model showed steric effects causing deformation of the DCPD molecule upon reaching the transition state to be the leading factor of the magnitude of the cycloaddition reaction activation barrier. Deformation of the DCPD molecule mostly occurs in two dihedral angles-the angle of escape of H atoms from the plane of the double bond involved in cycloaddition and the angle between the NB and CP fragments. The sum of deviations of these angles in the transition states (or products) structures is in good agreement with Gibbs activation energies of cycloaddition reactions of CPD to DCPD. Quantum chemical calculations were carried out using density functional theory in Gaussian 09 software. Hybrid exchange-correlation PBE0 functional was used with cc-pVTZ basis set.

Computation of rate coefficients in solutions based on transition state theory combined with a heuristically corrected polarizable continuum model: intermolecular Diels-Alder reactions as case studies.

Transition state theory (TST) based on activation parameters computed using quantum mechanics calculations combined with the polarizable continuum model (QM/PCM) is a fundamental tool for investigating reaction rates in the liquid phase. In conventional QM/PCM methods, thermodynamic data and partition functions for a solute are often derived from a quasi-ideal gas treatment (IGT) widely implemented in commercially available computation packages. This approach tends to overestimate entropy because calculations of thermodynamic parameters in the liquid phase ignore hindered translational and rotational modes in real solutions. The present work formulated partition functions for more realistic solutes hindered by surrounding solvent molecules in conjunction with the basic QM/PCM concept. In addition, a configuration partition function for solute molecules at a standard concentration of 1 mol dm-3 was incorporated using a simple lattice model. The canonical partition function and thermodynamic functions were derived based on statistical thermodynamics for localized systems. Expressions for rate coefficients within TST were also derived with a consistent formalism based on the standard state selected in partition function calculations. The performance of the proposed method was assessed by predicting rate coefficients for three different Diels-Alder reactions and comparing these with experimental results. QM/PCM calculations at the G4//ωB97X-D/6-311++G(d,p)/IEF-PCM level of theory with corrections for the dispersion and repulsion energies were performed to obtain the electronic structures of stationary points on potential energy surfaces as a means of finding activation enthalpy, entropy and Gibbs energy values based on revised partition functions as well as predicting rate coefficients. The activation Gibbs energies obtained from our proposed method were lower than those obtained from the IGT method due to reasonable entropy computations. The proposed method overestimated the rate coefficients by one to two orders of magnitude compared to the experimental values, whereas the IGT method underestimated them by the same amount. This discrepancy arises because the proposed method calculates the partition function from the viewpoint of a localized system, whereas the IGT method calculates it from the viewpoint of a non-localized system. Given that actual liquids exist in a state between non-localized and localized systems, it is essential to formulate the partition function in a way that more accurately represents the liquid state.

Density-Gibbs energy correlation models for binary biofuel mixtures

The density of binary biofuel mixtures significantly influences fuel properties, directly affecting internal combustion engine performance. This research aims to develop correlational models to calculate densities in binary biofuel mixtures, leveraging the Gibbs energy mixing rule. Two correlation models are proposed: the ideal Gibbs energy mixing rule and the Gibbs energy quadratic mixing rule. These models aim to enhance the cross-interaction of Gibbs energy of activation (ΔG12) to improve predictive performance. Importantly, the constants of the existing models are directly related to thermodynamic parameters. To assess the accuracy of the models, observed densities were collected from four different binary systems: biodiesel + diesel, pure fatty acid ethyl ester + alcohol, biodiesel + alcohol, and alcohol binary mixtures, amounting to 2242 data points obtained from the literature. Based on mole fractions, both models were compared to earlier approaches. The examination revealed that the equation formulated by the quadratic mixing rule exhibited heightened precision and efficacy. Our data demonstrate that the extended ΔG12 provided the most accurate results.

Experimental and theoretical studies to investigate molecular interactions between ethylene glycol oligomers and 1-butyl-3-methylimidazolium bromide

The thermophysical characteristics of pure liquids and their mixes are substantial in applied as well as theoretical research. This paper presents the measured data on: density (ρ), viscosity (η), refractive index (nD) and consequent calculated parameters: {excess molar volume (VmE), partial molar volume (V¯m), excess partial molar volume (V¯mE), deviation in viscosity (Δη), excess Gibbs energy of activation of viscous flow (ΔG∗E), deviation in refractive index (ΔϕnD) and deviation in molar refraction (ΔxRM)} of binaries containing 1-butyl-3-methylimidazolium bromide ([BMIM]Br) with glycol oligomers (mono/di/tri/tetra-ethylene glycol) at T/K = 298.15–313.15 and pressure p/MPa = 0.1. The Redlich-Kister equation efficiently estimates the standard deviation between the experimental and calculated excess properties. The interactions between constituents were considered while interpreting the obtained results. The values of VmE, V¯mE, Δη, ΔϕnD and ΔxRM exhibited negative trends throughout the range, whereas ΔG∗E values displayed a sigmoidal shift (negative to positive) with increasing [BMIM]Br concentration. The VmE data has been explored in terms of Prigogine-Flory-Patterson (PFP) and Graph theories to elucidate the deviations in thermophysical properties of the mixtures caused by variations in strength and magnitude of interactions. Additionally, the η values were correlated using ten models and their correlation ability has been perceived via the average standard deviation percentage. The pure and binary mixtures were also spectroscopically examined using Fourier Transform InfraRed (FT-IR) and Raman spectroscopy to elucidate the structural variations.

New QSPR molecular descriptors based on low-cost quantum chemistry computations using DFT/COSMO approach

This work presents a simple computational methodology to determine new theoretical molecular descriptor scales convenient for use in QSPR correlations and the analysis of solvation-related properties. On the basis of low-cost quantum chemical computations using DFT/COSMO approach, in particular that implemented in the ADF/COSMO-RS module of the Amsterdam Modeling Studio program package, optimized geometry and local screening charge density of a considered molecule are obtained and related to the proposed descriptors through an a priori simple reasoning. Values of four molecular descriptors, namely volume VCOSMO∗, hydrogen bond/Lewis acidity αCOSMO and basicity βCOSMO, and charge asymmetry of the nonpolar region of the molecule δCOSMO have been calculated and are presented for sets of 128 non-ionic organic molecules and 47 ions composing ionic liquids. Relation of the proposed scales to some others that are widely known or presented recently in the literature has been examined. Although the present methodology is completely independent of any experimental data, the theoretical descriptor scales proposed here have been found to correlate linearly quite well with the respective empirical scales (mostly R2 > 0.8, and for some R2 > 0.9). For non-ionic organics, just the direct proportionality provided adequate fits of the well-established prominent scales such as those of Abraham, Klamt, Kamlet-Taft, Catalan, Gutmann, and Laurence and showed only a few statistically justifiable outliers. For ions composing ILs, the linear fits of seven acidity or basicity scales presented previously with those proposed in this work were of similar quality. Examining the observed outliers, several descriptor values reported in the literature were identified as being in error. Good performance of the new descriptor scales has been demonstrated by employing them for LSER fitting of various solvation-related thermodynamic and kinetic properties such as standard vaporization enthalpy, standard hydration enthalpy, air–water partition coefficient, air-IL partition coefficient, and solvent effects on the activation Gibbs energy or rate constant of SN1 and SNAr reactions. The quality of these correlations appears to be comparable to that of the correlations currently available for these properties, regardless of the role, solute or solvent, the involved molecules played.

Density, Viscosity, Refractive Index, Speed of Sound, Molar Volume, Isobaric Thermal Compressibility, Excess Gibbs Activation for Fluid Flow, and Isentropic Compressibility of Binary Mixtures of Methanol with Anisole and with Toluene at 298.15 K and 0.1 MPa

Density, viscosity, refractive index, and ultrasonic velocity were measured for the pure materials anisole, methanol, and toluene, and for the binary mixtures: methanol—anisole and methanol—toluene. Excess molar volume VE, isobaric thermal compressibility α, excess Gibbs activation energy for fluid flow ΔGE*, and excess isentropic compressibility κSE were calculated from the measured quantities. For both binary mixtures VE and κSE were <0 while Δn > 0 and ΔGE* > 0 over the entire mole fraction composition range. Anisole mixtures exhibited more negative values for VE and κSE while more positive values were displayed for Δn and ΔGE* compared to toluene mixtures. For Δη, negative values were observed at low alcohol concentrations but positive values at high alcohol concentrations for both systems.

Investigating Thermal Decomposition Kinetics and Thermodynamic Parameters of Hydroxyl-Terminated Polybutadiene-based Energetic Composite

Background: Hydroxyl-Terminated Polybutadiene (HTPB)-based energetic compositions have been developed for enhanced blast energetic composite, composite rocket propellant formulations, metal cutting, demolition, welding and explosive reactive armour in civil and military applications. The types and choice of curing agents are crucial in enhancing the mechanical and structural integrity of the binder. To understand the stability and safety of energetic composites for potential applications, it is necessary to understand the thermal decomposition kinetics and thermodynamic parameters clearly. Objective: The main objective is to study the decomposition kinetic and thermodynamic parameters of energetic composites cured by different curing agents. Methods: A series of energetic composites based on HMX (1,3,5,7-tetranitro-1,3,5,7- tetrazocane) and HTPB-based binder system cured with various curing agents were prepared by the cast cured method. The curatives, namely MDI (4,4’-methylene diphenyl diisocyanate), IPDI (isophorone diisocyanate), TDI (toluene dissocyanate) and TMDI (2,2,4-trimethylhexamethylene diisocyanate) were used. The thermal analysis method was employed to investigate the thermal decomposition characteristics, which are closely associated with the thermal stability and safety considerations during handling, processing, and storage. The kinetic parameters for thermal decomposition reactions were studied by employing the Flynn-Wall-Ozawa method. The thermodynamic parameters of the activation enthalpy, activation Gibbs energy free and activation entropy of all energetic composites were also determined by the theory of activated complex. Results: The thermogravimetric results show that the thermal stability is almost similar for all composites cured with the different types of curing agents. The average activation energy of the energetic composites cured with IPDI, MDI, TMDI and TDI was 207.5, 237.3, 243.3 and 187.6 kJ/mol, respectively. The thermodynamic parameters for the thermal decomposition process show that they are generally thermodynamically stable and non-spontaneous. Scanning electron microscope (SEM) micrographs of all the samples clearly indicate that HMX crystals are well embedded in the polymer matrices. result: The thermogravimetric results show that the thermal stability and thermal decomposition behaviour do not change significantly by varying the type of the curing agent in the HTPB-based binder. The SEM micrographs of all the samples clearly indicate that HMX crystals are well embedded in the polymer matrices. The averaged activation energy for the HMX/HTPB/MDI, HMX/HTPB/IPDI, HMX/HTPB/TDI and HMX/HTPB/TMDI samples obtained from FO method was 237.3, 207.5, 187.6 and 243.3 kJ/mol, respectively. The thermodynamic parameters including the activation enthalpy, activation Gibbs free energy and activation entropy for the thermal decomposition process show that they are generally thermodynamically stable and non-spathaceous. Conclusion: The thermal stability of all energetic composites is almost constant. The activation energy of the prepared energetic composites is significantly varied with varying the type of curing agents in the HTPB-based binder system. The thermodynamic parameters indicate that composites possess superior stability and thermal safety. The SEM micrographs indicate that HMX crystals of prepared composites are embedded in the polymer matrix.

Fundamental properties and intermolecular interaction of triethylene glycol + ethylenediamine aqueous solution for CO2 capture

Solvent absorption as a significant method for carbon dioxide capture, exploring the mechanism of CO2 capture and regeneration solvents is essential for industrial applications. In this work, water (H2O) + (ethylenediamine (EDA) + triethylene glycol (TEG)) system with the constant mole ratio (TEG: EDA = 1: 1) was chosen as the liquid absorbent. In order to gain a deeper comprehension of solution properties of H2O + (EDA + TEG) system, the density (ρ) and viscosity (η) of fundamental properties were measured at P = 1005 hPa and T = (298.15 K to 318.15 K) with the temperature step of 5 K. The excess properties, including excess molar volume (VmE), viscosity deviation (Δη), and excess Gibbs energy of activation of viscous flow (ΔG*E) of H2O + (EDA + TEG) system were calculated from the experimental ρ and η values, and fitted well with the Redlich-Kister polynomial equation. The above results combined with the spectra proved the existence of intermolecular interaction in H2O + (EDA + TEG) system, which favorably fixed CO2. Subsequently, the aqueous solution with mass fraction of 15 wt% EDA and molar ratio EDA: TEG = 1: 1 was used for absorbing CO2 (room temperature) and desorbing (378.15 K) for 5-time cycles, and the cycling absorption performance decreased. So as to explore the reason of degradation, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and nuclear magnetic resonance carbon spectroscopy (13C NMR) were used to analyze the circulating absorption mechanism of CO2 in H2O + (EDA + TEG) system, which revealed that alkyl carbonates and partially indecomposable substance 2-imidazolidinones generated in the cyclic process, and provided some implications for the industrial application.

A computational investigation of the thermodynamics and kinetics of multiple single-step electron transfers of various Ni- and chalcogen-containing complexes

Continued increase in green house gas emissions will lead to irreversible and unpredictable damage to the environment and biosphere. CO2 alone contributes to about two-thirds of the energy imbalance causing climate change. The bulk of these CO2 emissions can be traced to fossil fuels, which presently account for 82% of this green house gas. Developing effective renewable–alternative fuel sources is crucial to mitigate the harmful effects of fossil fuels. One such alternative fuel source is molecular hydrogen, which can be produced by the photocatalytic splitting of water using metal-based catalysts. This study investigates the thermodynamics and kinetics associated with single-step protonations and reductions of Ni[(S2C2H2)(N2C2H4)], Ni[(Se2C2H2)(N2C2H4)], and Ni[(Te2C2H2)(N2C2H4)] complexes using density functional theory. Results found diselenolene to be the least endergonic for the formation of the triply reduced, doubly protonated species with a Gibbs protonation energy of 79.6 kJ mol−1. Ditellurolene and dithiolene were slightly more endergonic with Gibbs protonation energies of 87.7 and 91.6 kJ mol−1, respectively. The most thermodynamically favorable pathways were found to be the ECCEE pathway for dithiolene and diselenolene, whereas the CECEE mechanism was found to be most favorable for ditellurolene. Kinetically, it was found that there were two feasible pathways for all three complexes. The first was a CCEEE pathway and the second was a CECEE pathway. All complexes were found to have similar Gibbs activation energies.

Kinetics of 4‑nitrophenol reduction with NaBH<sub>4</sub> over Ag/CuO nanomaterial catalyst

In this paper, Ag/CuO nanomaterials were prepared via hydrothermal method combined with chemical reduction and used as catalysts in the reduction of 4-nitrophenol. Kinetic study of 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) by sodium borohydride revealed a first order reaction. The reaction rate constant k increased with amount of silver crystals introduced into CuO nanosheets, with Ag/CuO catalyst concentrations and with temperature. The thermodynamic activation parameters such as activation energy (Ea), enthalpy of activation (∆H#), entropy (∆S#) and Gibbs energy (∆G#) of activation were determined. The value of Ea, ∆H#, ∆S# and ∆G# were 72,33 kJ/mol, –69,86 kJ/mol, –24,28 J/K.mol and –62,50 kJ/mol (303K), respectivement. Ethanol and isopropanol were able to inhibit the 4-NP reduction with NaBH4 in the presence of Ag/CuO catalyst.

Viscous flow and structural properties in water-ethanol-urea systems

The structural features of water-ethanol, water-urea and water-ethanol-urea systems were studied on the basis of experimental estimates of kinematic viscosity at different temperatures and concentra-tions. For this purpose, the concentration dependences of the Gibbs energy of activation of the viscous flow, the enthalpy of activation of the viscous flow and the entropy of activation of the viscous flow of the studied systems were analyzed. The results show that ethanol has a structuring and then de-structive effect on water up to a concentration of 0.15 molar, and urea has a destructive effect on the structure of water, starting from such small concentrations. The addition of urea to the ethanol-water system does not affect the inversion point.

Built-In Electric Field Boosted Overall Water Electrolysis at Large Current Density for the Heterogeneous Ir/CoMoO4 Nanosheet Arrays.

Advanced bifunctional electrocatalysts are essential for propelling overall water splitting (OWS) progress. Herein, relying on the obvious difference in the work function of Ir (5.44eV) and CoMoO4 (4.03eV) and the constructed built-in electric field (BEF), an Ir/CoMoO4/NF heterogeneous catalyst, with ultrafine Ir nanoclusters (1.8±0.2nm) embedded in CoMoO4 nanosheet arrays on the surface of nickel foam skeleton, is reported. Impressively, the Ir/CoMoO4/NF shows remarkable electrocatalytic bifunctionality toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), especially at large current densities, requiring only 13 and 166mV to deliver 10 and 1000mAcm-2 for HER and 196 and 318mV for OER. Furthermore, the Ir/CoMoO4/NF||Ir/CoMoO4/NF electrolyzer demands only 1.43 and 1.81V to drive 10 and 1000mAcm-2 for OWS. Systematical theoretical calculations and tests show that the formed BEF not only optimizes interfacial charge distribution and the Fermi level of both Ir and CoMoO4, but also reduces the Gibbs free energy (ΔGH*, from 0.25 to 0.03eV) and activation energy (from 13.6 to 8.9kJmol-1) of HER, the energy barrier (from 3.47 to 1.56eV) and activation energy (from 21.1 to 13.9kJmol-1) of OER, thereby contributing to the glorious electrocatalytic bifunctionality.

Density-functional tight-binding molecular dynamics study on fixation reaction of CO2 to styrene oxide catalyzed by Mg-MOF-74 metal-organic framework

Abstract Carbon capture and utilization is a strategy to reduce CO2 emissions by utilizing them to synthesize fine chemicals. Mg-MOF-74 exhibits exceptional CO2 adsorption capacity and functions as a catalyst in styrene carbonate synthesis from CO2 and styrene oxide. We examined the structural properties and energetics of styrene carbonate synthesis in Mg-MOF-74 at the third-order density-functional tight-binding level. A novel reaction mechanism via the formation of a seven-membered ring intermediate was found to exhibit a lower Gibbs activation energy than the previously proposed mechanism.

Hydrobismuthation: Insertion of Unsaturated Hydrocarbons into the Heaviest Main Group Element Bond to Hydrogen.

The bismuth hydride (2,6-Mes2H3C6)2BiH (1, Mes = 2,4,6-trimethylphenyl), which has a Bi-H 1H NMR spectroscopic signal at δ = 19.64 ppm, was reacted with phenylacetylene at 60 °C in toluene to yield [(2,6-Mes2C6H3)2BiC(Ph)=CH2] (2) after 15 min. Compound 2 was characterized by 1H, 13C NMR, and UV-vis spectroscopy, single crystal X-ray crystallography, and calculations employing density functional theory. Compound 2 is the first example of a hydrobismuthation addition product and displays Markovnikov regioselectivity. Computational methods indicated that it forms via a radical mechanism with an associated Gibbs energy of activation of 91 kJ mol-1 and a reaction energy of -90 kJ mol-1.

Elucidation of the mechanism of the esterification of boric acid with aliphatic diols: a computational study to help set the record straight.

We present a theoretical investigation on the esterification process for boron ester synthesis, considering boric acid and 2(R),4(S)-pentanediol as model boron and diol derivatives, respectively. We report an unprecedented mechanistic pathway, able to rationalise, in contrast with the reported ones, the relatively low Gibbs energies of activation and the pH dependence experimentally observed in the formation of boron esters. We believe that these findings will improve the possibility to predict cross-link reaction rates of boron esters as a fundamental tool in the rational design of functional materials based on boron-oxygen linkages.

Porous metakaolin geopolymer as a reactive binder for hydroxyapatite adsorbent granules in dye removal

In this study, porous hydroxyapatite-metakaolin geopolymer (HAP-MK-GP) granules were prepared with a novel method for adsorption of organic pollutants from aqueous solutions, using brilliant green dye as a model compound. The preparation involved combining finely powdered hydroxyapatite, metakaolin, and solid sodium metasilicate in a high-shear granulator. Then, hydrogen peroxide (H2O2) was added at different concentrations (0.0, 5.0, 7.5, or 10.0%) as a combined granulation fluid and blowing agent. In the resulting granules, metakaolin geopolymer bound the powdered hydroxyapatite as granules and contributed to the adsorption capacity. To determine their structural, morphological, and mechanical properties, the granules were characterized with infrared spectroscopy, X-ray fluorescence, scanning electron microscopy, specific surface area and porosity analysis, and compressive strength tests. The granules had a high porosity and promising compressive strength and Young's modulus of 0.8 and 10 MPa, respectively, potentially enabling their use in large-scale adsorption columns. The monolayer adsorption mechanism of brilliant green dye onto HAP-MK-GP granules was confirmed by fitting the obtained batch adsorption data to the Langmuir isotherm model which showed that the adsorption capacity was approximately 41 mg/g. The optimum conditions were: pH of 7, initial dye concentration of 100 mg/L, adsorbent dose of 3 g/L, agitation speed of 250 rpm, contact time of 30 min, and temperature of 298 K. The adsorption kinetic data indicated that the adsorption followed the pseudo-second-order kinetic model. The thermodynamic parameters, including Gibbs free energy, enthalpy, entropy, and activation energy, indicated that adsorption was spontaneous, endothermic, and was based on physisorption. The rate-limiting step was film diffusion. Based on the results, HAP-MK-GP granules could be a feasible adsorbent for the removal of dyes from industrial wastewater. Moreover, the facile granulation method presented here could be applied to other powdered adsorbents as well to prepare adsorbent granules.

Two-stage conversion of CO2 to methanol and dimethyl ether using CuO–ZnO–Al2O3/protonated Y-type zeolite catalysts

The CuO-ZnO-Al2O3/protonated Y-type zeolite (CZA/HYZ) catalysts were prepared via co-precipitation method and employed in a two-stage CO2 conversion process using a dual fixed–bed column at different temperatures and 50 bar. Catalytic components of CZA/HYZ were copper species that have been identified with XPS. Remarkably, the fine structures of CZA/HYZ catalysts metal atoms were confirmed with XANES and EXAFS spectra. Molecular configurations of catalytic species in CZA/HYZ catalyst simulated from the XANES/EXAFS spectra-analyzed fine structural parameters were schematically displayed. The optimal catalytic performances of CZA/HYZ (CH3OH conversion=78.0%, CH3OCH3/HCOOH selectivity=91.7%/8.3%, CH3OCH3/HCOOH yield=71.5%/6.5%) were achieved at 250 ºC. The Arrhenius equation and a pseudo-first-order/second-order model were used to evaluate the activation energies and rate constants of CH3OH and CH3OCH3 formations at various catalytic temperatures. The low activation energies (2.720 and 1.160 kJ mol−1) and Gibbs energies (3.26 and −40.00 kJ mol−1) of CH3OH and CH3OCH3 formations at 250 ºC, demonstrated that their spontaneities were remarkably improved via CZA/HYZ, respectively. The total income from a 10–ton per day (10–TPD) for a petrochemical refinery plant waste gas utility process was USD $43,557d−1, as well a payback of 3.23 years, based on cost evaluation. The proposed process provides a continuous two-step process for manufacturing high–value-added chemicals using industrial CO2 emitted and syngas.