Eyring Equation Research Articles

Thermodynamic and spectroscopic analyses of N-Methyl benzylamine-isomeric amyl alcohol binary mixtures: Jouyban-Acree model correlation and experimental validation

ABSTRACT Excess molar volume, excess isentropic compressibility, deviation in viscosity, and excess Gibbs free energy of activation for viscous flow for binary mixtures of N-Methyl benzyl amine (NMBA) with 2-Methyl-2-butanol (2M2B), 2-Methyl-1-butanol (2M1B), and 3-Methyl-1-butanol (3M1B) were determined from measured densities (ρ), viscosities (η) and speeds of sound (u) at 303.15 K to 313.15 K. Influence Structural disparities on excess properties is discussed concerning intermolecular forces. The Prigogine – Flory – Patterson (PFP) theory identifies predominant molecular interactions, and the Jouyban – Acree model correlates density, speed of sound, and viscosity with composition. Thermodynamic activation parameters were calculated using the Eyring equation to study viscous flow thermodynamics. FT-IR and 1H NMR spectra of equimolar binary mixtures were analysed to confirm experimental findings through absorption bands (cm−1) and chemical shifts.

Synthesis and characterization of a nanocatalyst consisting of tungsten (VI) oxide and ruthenium for potential use in the hydrogen generation via hydrolysis of methylamine-borane

The demand for effective and safe chemical storage systems as an alternative energy carrier is unabated. This study reports the analysis of methylamine-borane (MeAB) as a new, efficient, and widely applicable technological storage material for mobile applications. Here, we report the preparation of tungsten (VI) oxide (WO3) supported ruthenium (Ru) nanoparticles (Ru/WO3) by impregnation-reduction method and their use as a nanocatalyst in the hydrolysis of MeAB for hydrogen (H2) production. Ru/WO3 nanocatalyst was characterized by a combination of advanced analytical tools such as XRD, XPS, TEM, TEM-EDX, SEM, and SEM-EDX. Ru/WO3 nanocatalyst, with an average particle size of 2.16 ± 0.23 nm obtained from TEM analysis, produces H2 at 298 K with an initial turnover frequency (TOFinitial) value of 43.57 min−1 in complete conversion in the hydrolysis of MeAB. In addition, the activation energy (Ea#), activation enthalpy (ΔH#) and activation entropy (ΔS#) values of the Ru/WO3 nanocatalyst were calculated as in MeAB hydrolysis are 51.54 kJ/mol, 3.7 kJ/mol and 184.57 J/mol × K, respectively, from the Arrhenius and Eyring-Polanyi equations. It was concluded that both the calculated TOFinitial value and activation parameters were quite valuable compared to previous catalysts used for MeAB hydrolysis.

Comparison of surface adsorption efficacies of eco-sustainable agro/animal biomass-derived activated carbon for the removal of rhodamine B and hexavalent chromium.

Effective management and remediation strategies are crucial to minimize the impacts of both organic and inorganic contaminants on environmental quality and human health. This study investigates a novel approach utilizing cotton shell activated carbon (CSAC), rice husk activated carbon (RHAC), and wasp hive activated carbon (WHAC), produced through alkali treatment and carbonization under N2 atmosphere at 600°C. The adsorption capacities of biomass-derived mesoporous activated carbons (CSAC, RHAC, WHAC) alongside macroporous commercial activated carbons (CAC) were evaluated for removing rhodamine B (Rh B) and hexavalent chromium (Cr6+). The CSAC exhibits remarkable adsorption efficiency (255.4mg.g-1) for Cr(VI) removal, while RHAC demonstrates superior efficacy (174.2mg.g-1) for Rh B adsorption. Investigating various optimal parameters including initial pH (pH 3 for Cr and pH7 for Rh B), catalyst dosage (200mg.L-1), and initial concentration (20mg.L-1), the Redlich-Peterson isotherm model is applied to reveal a hybrid adsorption mechanism encompassing monolayer (chemisorption) and multilayer (van der Waals adsorption) processes. Kinetic analysis highlights the pseudo-second-order and Elovich models as the most suitable, suggesting physiochemisorption mechanisms. Thermodynamic analysis indicates the endothermic nature of the adsorption process, with increased randomness at the solid-solution interface. Isosteric heat investigations using Clausius-Clapeyron, Arrhenius, and Eyring equations reveal a heterogeneous surface nature across all activated carbons. Further confirmation of Rh B and Cr(VI) adsorption onto activated carbons is provided through FTIR, FESEM, and EDAX analysis. This study highlights the innovation and promise of utilizing biomass-derived activated carbons for effective pollutant removal.

Co-Solvent effect and Kinetics of Alkaline Hydrolysis of Butyle Salicylate

The base catalised hydrolysis of buyl salicylate has been carred out in water-DMF binary solvent mixture covering range of 30 to 70% (v/v) of solvent composition at different Temperature (20 to 400 C). The reaction followed second order rate constant which decreases with increase of solvent composition. The salvation and desolvation concept are used to explain the solvent influence on rate and mechanism is the reaction. The relation between changes in dielectric constant due to variation of reaction mixture and change in specific rate constant has been explained on the basis of electrostatic and non-electrostatic contribution of solvent mixture. Calculated value of Iso-composition activation energy is found to be increases with increase of solvent composition. The thermodynamic parameters (ΔG*, ΔH* & ΔS*) has been determined with help of Wynne Jone and Eyring equation which show the great dependency on solvent composition.

Compensación cinética y termodinámica del pardeamiento no enzimático de zumos clarificados de limón

This paper presents a study on kinetic and thermodynamic compensation to evaluate the kinetics of non-enzymatic browning of clarified lemon juices. In a previous work, the kinetic constants of browning were presented using the evolution of the absorbance at 420 nm (A420) and luminosity (L*) for different soluble solids contents (64.6; 50; 35; 20 and 10 ºBrix) and different working temperatures (70, 80, 90 and 95 ºC). The parameters of the Arrhenius equation were obtained by fitting the kinetic constants and temperatures. The variation of lnK0 with Ea follows a linear trend, so there is kinetic compensation, with isokinetic temperature values being 126.6 ºC and 149.7 ºC for A420 and L*, respectively. The transition state equilibrium constants were determined using the Eyring equation for each soluble solids content and each temperature. The equilibrium constants were adjusted to the Van't Hoff equation and the set of pairs of estimated values for the activation enthalpy and the activation entropy also followed a straight line, which causes thermodynamic compensation, with isoequilibrium temperatures of 112.8 ºC and 136.3 ºC for A420 and L*, respectively. It was concluded that the browning mechanism is the same for the ranges of soluble solids content and temperature studied. Since all isokinetic and isoequilibrium temperatures were higher than the working temperature values, it was also concluded that the control was enthalpic for all cases. To avoid the deterioration of these juices, it is advisable to intervene in the working temperature, trying to ensure that the heat treatment is carried out at the lowest possible temperature.

Co(II)-N4 Catalysts for the Coupling of CO2 with Epoxides into Cyclic Carbonates: Catalytic Activity, Computational and Kinetic Studies.

In this study, we synthesized and characterized a series of cobalt(II) complexes bearing linear tetradentate N4 ligands. These Co(II)-N4 complexes proved to be efficient catalysts for the cycloaddition reaction between carbon dioxide and epoxides even at room temperature and 1 bar pressure of carbon dioxide without the need for solvents or cocatalysts. Furthermore, when combined with (triphenylphosphoranylidene)ammonium chloride (PPNCl) as a cocatalyst, the Co-N4 catalysts exhibited an impressive turnover frequency of up to 41,000 h-1 for coupling of epichlorohydrin/CO2. These Co(II)-N4 catalysts were found to have excellent stability and reusability, retaining their catalytic activity after they were recycled seven times. Density functional theory (DFT) calculations provided a comprehensive mechanism for the cycloaddition reaction, indicating that the rate-determining step is the epoxide ring opening, in both the presence and absence of PPNCl. Further kinetic studies allow us to determine the activation parameters (ΔH‡, ΔS‡, and ΔG‡ at 25 °C) of the coupling reaction using the Eyring equation. The Gibbs free activation energy obtained from the kinetic studies was in close agreement with that of the DFT calculations. The substituent effect on the cycloaddition reaction of CO2 with various substituted styrene oxides was also examined for the first time.

Kinetics and thermodynamics in microwave-assisted transesterification of palm oil utilizing sulphonated bio-graphene catalysts for biodiesel production

Enhanced reaction performance is what has piqued interest in using graphene-based catalysts in producing biodiesel. However, in-depth analyses were lacking from a kinetic and thermodynamic standpoint. This means that a well-designed experiment is necessary to determine the effect that the graphene catalysts have on the reaction rates and yields. This work addresses the kinetic and thermodynamic aspects of heterogeneously catalyzed transesterification using sulphonated biomass-derived graphene catalysts, i.e., bGO-SO3H and brGO-SO3H. It was accomplished using the pseudo-first order mechanism and the Eyring-Polanyi equation, with all data fitting satisfactorily in both models at the ideal reaction temperature of 353.15 K, resulting in R2 values of 0.9784 (bGO-SO3H) and 0.9884 (brGO-SO3H). The calculated activation energy (Ea) was determined to be 44.45 and 51.73 kJ mol-1 for bGO- and brGO-SO3H, respectively. Additionally, the Gibbs free energy (ΔG) values were determined at −38.09 and −31.81 kJ mol−1 for bGO- and brGO-SO3H, respectively. Meanwhile, the values for ΔH and ΔS were obtained as 41.69 kJ mol−1 and 225.93 J mol−1 K−1, respectively, and 48.96 kJ mol−1 and 228.72 J mol−1 K−1, respectively. These collective outcomes collectively signify the endothermic nature of the reaction and their spontaneity, particularly under elevated temperature conditions.

Exploring kinetic and thermodynamic insights of graphene related two dimensional materials for carbon dioxide adsorption

Graphene related two dimensional materials (GR2Ms) are promising adsorbents for CO2 capture. However, the CO2 adsorption kinetics and mechanisms on these materials remain insufficiently explored and understudied. Recognizing the pivotal role of adsorption kinetics in assessing the practical applicability, this study comprehensively evaluates the CO2 adsorption kinetics, underlying mechanisms, and thermodynamic properties via gravimetric analysis on three distinct well-characterized graphene materials (few layer graphene-FLG, graphene oxide-GO, reduced graphene oxide-rGO) across temperatures from 25 to 75 °C under atmospheric pressure. Results reveal that Avrami’s fractional model offers the most accurate fit for CO2 adsorption kinetics among the three examined models (pseudo-first, pseudo-second, and Avrami’s fractional order). The interplay between the physico-structural-chemical properties of GR2Ms and the CO2 adsorption kinetics discloses that the morphology, crystallite size, specific surface area and porosity of GR2Ms greatly influence the CO2 adsorption rate as evidenced by the largest rate constant, kA value of rGO at 25 to 75 °C under atmospheric pressure. Analysis of activation parameters including activation energy, enthalpy of activation, entropy of activation, and free energy of activation derived from Eyring, Arrhenius, and Gibbs equations indicates a greater favorability of CO2 adsorption on GR2Ms at lower temperatures. Moreover, investigation into the underlying interaction mechanisms between CO2 molecules and GR2Ms, using rate-limiting kinetic models (Boyd’s film diffusion model, interparticle diffusion model, and intraparticle diffusion model), confirms that both film diffusion resistance and intraparticle diffusion resistance predominantly govern the CO2 adsorption rate.

Real‐time dielectric monitoring of isothermal polymerization of methyl cyanoacetate and diethylene glycol dimethacrylate

AbstractDielectric spectroscopy (DS) was employed to monitor the isothermal polymerization processes of P(MCA‐DEGDMA) formed by the alternating copolymerization of methyl cyanoacetate (MCA) and diethylene glycol dimethacrylate (DEGDMA) at different temperatures in real time. P(MCA‐DEGDMA) is a polyether containing functional groups (O, CN, COOCH3) which can promote the transport of ions Li+, thereby having the potential to apply in polymer electrolytes. It is beneficial to investigate the effect of temperature and time on P(MCA‐DEGDMA) polymerization and choose a suitable synthesis strategy through dielectric monitoring. A time‐ and temperature‐dependent relaxation process induced by orientational polarization of the P(MCA‐DEGDMA) chain was observed over a frequency range from 10 kHz to 4 × 106 Hz. The time to reach polymerization equilibrium (tequ) and the dielectric conversion were determined through the time variations of the conductivity at low frequency (κl). The polymerization process shows the characteristic of “fast followed by slow,” and the tequ can be advanced by raising the polymerization temperature. In addition, by discussing the monitoring time dependence of relaxation time (τ) and permittivity (ε), it was concluded that the extent of polymerization (α) for P(MCA‐DEGDMA) at 40°C is the largest, and the optimal polymerization temperature is between 30 and 50°C. Furthermore, the free activation energy (ΔG), activation enthalpy (ΔH), and activation entropy (ΔS) of the relaxation process caused by the motion of the P(MCA‐DEGDMA) chain in three temperature ranges (10–20°C, 30–40°C, 50–60°C) were calculated by using Eyring's equation, from which the physical image of various structures and conformations of the P(MCA‐DEGDMA) chain during monitoring was proposed. Considering the effect of temperature on the generation and migration of free ions, and on the structure and conformation of the P(MCA‐DEGDMA) chain, some suggestions for the synthesis of P(MCA‐DEGDMA) are given: during the polymerization, the temperature is controlled at 10°C in the early stage and then gradually raised to 40°C, which may be beneficial to improving the extent of polymerization of P(MCA‐DEGDMA). Our work may be helpful to investigate the polymerization process of polyether obeying the same synthesis mechanism with P(MCA‐DEGDMA). It can be proven that DS is useful in detecting the inner information of the system changing over time through our work.

The oxidation of potassium hexacyanoferrate(II)trihydrate by potassium dibromodicyanoaurate(III) in acidic solution: a kinetic study

AbstractThe reduction of the dibromodicyanoaurate(III) ion by hexacyanoferrate(II)trihydrate was studied in an acidic medium. The reaction was first order in both Au(CN)2Br2− and Fe(CN)64− and a second order rate constant of k2 = 255 ± 5 M−1 s−1 at [H+] = 2.041 × 10−4 M, an ionic strength of 0.51 M (NaBr) and 20.0 ± 0.1 °C was found for the reaction. The reaction rate decreases with increasing [H+] in the region 0.0004 ≤ [H+] ≤ 0.065 M. An equilibrium constant of Ka = (3.00 ± 0.01) × 10−3 M (pKa = 2.52) at 20.0 ± 0.1 °C was found for the deprotonation of H2Fe(CN)62−. Activation parameters of ∆H# = 47.8 ± 0.9 kJ mol−1 and ∆S# = −37 ± 3 J K−1 mol−1 have been obtained by a least squares fit of temperature data directly to the Eyring equation. Graphical abstract

Experimental and Computational Kinetic Assessment of Ruthenium (III) Catalyzed Oxidation of Paracetamol by Hexacyanoferrate(III): A Mechanistic Pathway

AbstractThe ruthenium (III) catalyzed redox reaction of paracetamol with hexacyanoferrate (III) in an acidic medium has been investigated. The reaction shows fractional order dependence respecting paracetamol and first‐order dependence respecting the oxidant and ruthenium (III). It is enhanced by medium according to the equation kobs=a+b[H+]. The activation and thermodynamic parameters of the reaction have been estimated using the Arrhenius and Eyring equations. The oxidation product of paracetamol has been identified as quinone oxime through spectral analysis. Furthermore, the reaction has been examined in nine various organic solvents, and the solvents effect has been investigated by Taft's and Swain's multiparametric equations. The rate constants have been found to correlate well with Kamlet‐Taft's solvatochromic parameters (α, β, π*). The reaction constants have been found to be negative, suggesting that the reactivity is influenced mainly by the solute‐solvent interactions. On the basis of kinetic results, a plausible reaction mechanism has been proposed. The proposed mechanism is reinforced by additional evidence from density functional theory (DFT) computations conducted at b3lyp/6‐311*G (d,p) level, which demonstrate that the activation energy barriers align with the reactivity trend observed in the kinetics experiments. Therefore, these computational results provide further support for the proposed mechanism.

Utilization of Sulfonated Natural Zeolite as Catalyst for Glycerolysis Monooleate: Thermodynamic and Kinetic Study

The development and production of alternative fuels such as biodiesel that continues to be carried out further increases glycerol as a by-product of the biodiesel process. The accumulation that continues to occur will cause a decrease in the price of glycerol. To solve this problem, glycerol is reprocessed into its derivative products, one of which is Glycerol Mono Oleate (GMO). In this study, natural zeolite was modified using a sulfonation process. The results of catalyst characterization based on FTIR indicate that the modification in natural zeolite was successful when the catalyst had the expected functional groups. The thermodynamic parameters (ΔH, ΔS, ΔG) are determined for this reaction using the Eyring equation. The reaction fits with the pseudo-2nd order kinetic model. The activation energy of the esterification reaction using sulfonated zeolite is reported as 37.855 kJ/mol. The result shows that the best variable to produce GMO is the reaction at a temperature of 220oC with the conversion value was 95.00%.

Modeling viscoelasticity and cyclic creep of PEEK by parallel rheological framework (PRF)

Although creep is usually regarded as a quasistatic phenomenon, in multiple engineering applications the load is not constant, hence creep under cyclic loading conditions should be considered. The current work presents the theoretical and experimental study on the viscoelasticity and cyclic creep of PEEK (Polyether ether ketone) – the polymer with good chemical and thermal stability. Among other demanding applications, PEEK is used in bearings industry for the fabrication of cages, which main function is to isolate and to guide rolling elements. In this application the polymer cage is subjected to the long-term load alternating in time, meaning that classical creep (under constant load) cannot be presumed. In the current study, the non-linear viscosity is included into the generalized Maxwell model, employing the Eyring equations which postulate that the viscosity coefficient is not constant but is dependent on stress. The model is implemented with the Parallel Rheological Framework (PRF) (the numerical technique recently implemented in the commercial software ABAQUS), used to construct the generalized Maxwell model with hyper-elastic springs and dashpots of non-linear viscosity. Initially, the viscoelastic material parameters are identified from the uniaxial test, and later these parameters are used to simulate the PEEK response under cyclic loading, to predict the time to creep/fatigue failure. Eventually, the numerical predictions are compared to the test results. The comparison indicates that the developed method and its numerical implementation by PRF can be successfully used to model the non-linear viscoelastic behavior of PEEK under uniaxial load. It is also found, that the simulation of cyclic creep can be reasonably performed by using the current material model and PRF.

Determination of modes for safe application of selective micro-pulse individual retinal therapy of the macular zone using the modeling based on the theory of activated complex

Purpose: to make modeling of various modes of laser radiation, to assess the degree of damage to the retinal pigment epithelium and adjacent structures, and to determine modes and safety conditions of selective micro-pulse individual retinal therapy based on the theory of activated complex. Materials and methods. The authors have modeled the degree of damage to the chorioretinal complex and adjacent structures using the activated complex theory with the Eyring equation. The following definitions were used to determine the regime quality and safety conditions: micro-pulse mode is a mode with fixed values of micro-pulse duration, duty cycle and the number of pulses in the packet; power is a variable parameter. Efficiency is the ratio of the amount of denatured protein inside the retinal pigment epithelium layer to the total amount of protein in it. Selectivity is the ratio of the amount of denatured protein inside the retinal pigment epithelium layer to the total amount of denatured protein. Relative harmfulness is the ratio of denatured protein volume outside the retinal pigment epithelium to the volume of protein in it. Results and discussion. The quality of micro-pulse mode was found as depending on the selectivity value with efficiency equal to 90 %. With the efficiency value less than 50 %, the mode is non-selective, with more than 67 % – selective. Safety conditions for selective micro-pulse modes have been established, taking into account safety of the neurosensory retina and choroid in terms of relative harmfulness which should not exceed 1. Parameters at which micro-pulse modes have high values (more than 90 – 99) of efficiency and selectivity at the same time have been determined as well. It requires single pulse mode, micro pulse duration of 25 microseconds and power from 6 to 8 W. To expand the combination of parameters, it is necessary to be able to freely change them in increments of 1 pulse, 5 microseconds, 100 mW, with long interval and short duty cycle. These technical capabilities can be realized and implemented into clinical practice by manufacturers of laser devices. Conclusion. For selective micro-pulse individual retinal therapy of the macular zone with existing lasers, the following recommendation are to be observed: micro-pulse modes with pulse duration no more than 200 microseconds, short duty cycle less than 5 % and number of pulses in an envelope no more than 5; relative harmfulness less than one, radiation power selection, personalized patient’s characteristics.

Diffusion Effect on Octogen Coating-Curing Kinetics with Polyurethane Using Infrared Spectroscopy

The kinetic analysis of octogen coating with a polyurethane base containing hydroxyl-terminated polybutadiene (HTPB) was investigated using infrared spectroscopy. The coating process involved a solvent method, where octogen and liquid polyurethane were mixed, the solvent was evaporated, and curing took place at an elevated temperature. The ratio of HTPB to diisocyanate was equimolar. About 200 g octogen was coated with mixture of 2 mL HTPB, 50 mL ethyl acetate, and 0.2 mL TDI in the glass beaker at 30 °C for 1 h. The filtrated ethyl acetate was then evaporated, and the residue was dried in a vacuum oven for 15 min at 30 °C. The resulting film-coated octogen was cast into a KBr pellet and cured in the oven for 7 days at 40 °C, then infrared-analyzed every hour during the curing process. After curing, the shape of the coated octogen particles was analyzed using SEM Initially, the curing process occurred in the solvent system, followed by further curing in the bulk system. The kinetic analysis was performed using a modified diffusion-autocatalytic model, which includes noncatalytic, autocatalytic, and diffusion components. This model was compared with others during the bulk reaction and proved to be effective in correcting errors, particularly in the gel time region. Thermodynamic parameters were evaluated using the Arrhenius and Eyring equations. The reaction rate was initially controlled by chemical reactivity, but after the gel time, diffusion became the controlling factor. In the HTPB-TDI system, both the noncatalytic and autocatalytic parts decreased with increasing temperature, while diffusivity increased. It is worth noting that diffusivity is temperature-dependent. Different di-isocyanates, namely toluene diisocyanate (TDI), iso-phorone diisocyanate (IPDI), and hexamethylene diisocyanate (HMDI), were studied, revealing that HMDI exhibited higher reactivity than TDI and IPDI. The catalyst effect on reaction rate of the HTPB-TDI system was investigated. The addition of catalysts (0.1%) to the HTPB-TDI system decreased their activation energy in the order DBTL > FeAA > TPB. Catalysts did not change their diffusivity.

Kinetics of the Oxygen Evolution Reaction (OER) on Amorphous and Crystalline Iridium Oxide Surfaces in Acidic Medium.

Amorphous and crystalline IrO2 catalysts are synthesized by the Adams method and characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The oxygen evolution reaction (OER) is investigated on both the catalyst surfaces in 0.5 M H2SO4 electrolyte. The Tafel slope estimated in the temperature range of 293-333 K on the two surfaces indicates a change in the rate-limiting steps. The data are also analyzed in terms of the Eyring equation to estimate the activation enthalpy (ΔH#) and pre-exponential factor (Af) as a function of overpotential and therefore the charge-transfer coefficient (α). The estimated α values suggest strong electrocatalysis on both the surfaces. While the ΔH# plays a decisive role in the electrocatalysis on the amorphous sample, the trend of Af indicates that an increase in the entropy on the crystalline surface is pivotal in reducing the reaction barrier.

A Nuclearity-Dependent Enantiodivergent Epoxide Opening via Enthalpy-Controlled Mononuclear and Entropy-Controlled Dinuclear (Salen)Titanium Catalysis.

A nuclearity-dependent enantiodivergent epoxide opening reaction has been developed, in which both antipodes of chiral alcohol products are selectively accessed by mononuclear (salen)TiIII complex and its self-assembled oxygen-bridged dinuclear counterparts within the same stereogenic ligand scaffold. Kinetic studies based on the Eyring equation revealed an enthalpy-controlled enantio-differentiation mode in mononuclear catalysis, whereas an entropy-controlled one in dinuclear catalysis. DFT calculations outline the origin of the enantiocontrol of the mononuclear catalysis and indicate the actual catalyst species in the dinuclear catalytic system. The mechanistic insights may shed a light on a strategy for stereoswichable asymmetric catalysis utilizing nuclearity-distinct transition-metal complexes.

A Nuclearity‐Dependent Enantiodivergent Epoxide Opening via Enthalpy‐Controlled Mononuclear and Entropy‐Controlled Dinuclear (Salen)Titanium Catalysis

AbstractA nuclearity‐dependent enantiodivergent epoxide opening reaction has been developed, in which both antipodes of chiral alcohol products are selectively accessed by mononuclear (salen)TiIII complex and its self‐assembled oxygen‐bridged dinuclear counterparts within the same stereogenic ligand scaffold. Kinetic studies based on the Eyring equation revealed an enthalpy‐controlled enantio‐differentiation mode in mononuclear catalysis, whereas an entropy‐controlled one in dinuclear catalysis. DFT calculations outline the origin of the enantiocontrol of the mononuclear catalysis and indicate the actual catalyst species in the dinuclear catalytic system. The mechanistic insights may shed a light on a strategy for stereoswichable asymmetric catalysis utilizing nuclearity‐distinct transition‐metal complexes.

Isokinetic and Compensation Temperature in the Analysis of Thermal Dissociation of the Solid Phase under Dynamic Conditions

Sets of Arrhenius parameters, determined according to known different equations for dynamic conditions, in the vast majority form the Kinetic Compensation Effect (KCE). Converting these data to the simplified components of the Eyring equation comes down to Enthalpy–Entropy Compensation (EEC), which is consistent with the second law of thermodynamics. It has been proved that the impact of the generally known Coats−Redfern solution on the equation in differential form results in an isokinetic form of the equations and a very important coordinate T0;α0 (initial temperature and conversion degree), depending on the heating rate. This makes it possible to determine the parameters of Arrhenius’ law for both in silico and experimental data. An analytical method for determining this coordinate has been proposed. These considerations have given rise to an analysis of the relationship between two temperatures: initial and isokinetic. The sense of isokinetic temperature has been verified by the parameters CQF and K. Going further, it was found that the effects of EEC can be transformed into KCE and vice versa, which means that the two temperatures should be identical, i.e., Tiso=Tc. However, the experimental data indicate that the analyzed temperatures form a sequence T0↔Tiso↔Tc≤Teq, where Teq is the equilibrium temperature.

Facile “Green” synthesis of a novel Co–W–B catalyst from Rheum ribes shell extract and its effect on sodium borohydride hydrolysis: Kinetic mechanism

The present investigation aimed to assess the influence of the Co–W–B NPs catalyst on the process of sodium borohydride hydrolysis. The study involved the synthesis of Co–W–B NPs through the utilization of an eco-friendly green synthesis extract derived from the Rheum ribes shell in conjunction with the chemical reduction technique for catalyst production. The investigation of catalysts' structure and surface morphology was conducted through the utilization of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) techniques. The average particle size was determined to be 35 nm in TEM analysis. The presence of Co–W–B nanoparticles and their elemental composition % were determined through EDX analysis, revealing values of 63.9% (Co), 31.89% (C), 1.75% (B), and 2.46% (W) within the nanoparticle. The manufactured Co–W–B catalyst's use for hydrolysis of sodium borohydride was studied under various conditions, including different concentrations of NaOH and NaBH4, different amounts of catalyst, and different temperature parameters. The hydrogen production rate for the Co–W–B NPs catalyst in NaBH4 hydrolysis was determined to be 5367 mLg−1min−1 at 30 °C. The study involved the determination of TOF values for a catalyst composed of Co–W–B NPs, which were subjected to varying temperatures. The activation energies were determined through the utilization of the n-th order and Langmuir-Hinshelwood kinetic models and subsequently calculated using the Arrhenius equation, resulting in values of 35.36 and 31.70 kJ/mol, respectively. The values of enthalpy and entropy, ΔH and ΔS, were determined through the utilization of Eyring's equation, 18.49 kJ/mol and −80.7 J/mol.K, respectively.