Kinetic analysis of Li|Li+ interphase in an ionic liquid electrolyte

Kinetic analysis of the Li|Li⁺ interphase in an electrolyte based on N-metyl-N-propylpyrrolidinium bis(trifluoromethanesulfon)imide ionic liquid (MPPyrrTFSI) and lithium bis(trifluoromethanesulfon)imide salt (LiTFSI) was performed. Li|electrolyte|Li and LiC₆|electrolyte|Li cells were galvanostatically charged/discharged in order to form solid electrolyte interphase (SEI) protecting layer. SEM images showed that the surface of both Li and LiC₆ anodes was covered with small particles. The fitting procedure of electrochemical impedance data taken at different temperatures gave three resistances (R _el, R _SEI, R _ct) and hence, three lnR = f(T ^?1) straight lines of different slopes. Specific conductivity and activation energy of the conduction process of the liquid electrolyte, were ca. σ = 2.5 mS cm^?1 (at T = 25.0 °C) and $ E_{\text{el}}^{\# } $  = 15 kJ mol^?1. Activation energy for the conduction process in the SEI layer was ca. 56 kJ mol^?1 in the case of the metallic lithium and 62 kJ mol^?1 for the graphite anode. Activation energy of the charge transfer process, $ E_{\text{ct}}^{\# } $ , for Li and LiC₆ anodes was 71 and 65 kJ mol^?1, respectively. Analysis of literature data for different electrolytes suggests that the $ E_{\text{ct}}^{\# } $ value for Li⁺ reduction may be approximated by 57 ± 5 kJ mol^?1. Activation energy for the diffusion processes in the graphite electrode, detected from the Warburg coefficient, was ca 74 kJ mol^?1.     

Leaching Kinetics of Fe2Al5 and Skeletal Iron Formation

Caustic leaching of fine particles of Fe₂Al₅ alloy to produce skeletal Fe catalysts was studied using a 2⁴ factorial experimental design, in which alloy particle size, aqueous NaOH concentration, temperature and stirrer speed were varied. Analysis of the results from the design showed that the BET surface area of the skeletal iron increased with decreases in temperature, caustic concentration and particle size according to S_BET = 222.7 ? 0.461 · T ? 2.35 · c_NaOH ? 0.0245 · D _p. An Avrami–Erofeev model ?ln(1 ? α) = kt with an activation energy of 55 ± 5 kJ mol^?1 and a shrinking core model for volume contraction 1 ? (1 ? α)^1/3 = kt and an activation energy of 56 ± 5 kJ mol^?1 provided the best fit to the kinetic data for leaching.     

Study on adsorption performance of 2-amino-4-methylbenzothiazole onto chemical modification adsorption resins

A series of functional hyper-cross-linked resins were successfully synthesized by incorporating anhydride, sulfoacid and menthanone groups into post-cross-linked polymer. They were evaluated for adsorption of 2-amino-4-methylbenzothiazole (2A4MBT) from aqueous solution. The five resins were efficient for adsorption of 2A4MBT from aqueous solution. The adsorption process includes both physical adsorption and irreversible chemical adsorption. The absolute value of adsorption enthalpy had an order of PRLMR (3.24 kJ mol^?1) < IDLMR (7.96 kJ mol^?1) < TMAMR (9.72 kJ mol^?1) < PAMR (?13.1 kJ mol^?1) < SAMR (21.8 kJ mol^?1). Phthalic anhydride-modified resin could be regenerated by 10% HCl/methanol solution after adsorption equilibrium.     

Curing Characterization of the Bis-salicylaldehyde-triethylenetetramine Nickel (II)/Epoxy System

The curing reaction of epoxy resin and bis-salicylaldehyde-triethylenetetramine nickel (II) (Ni(sal)₂trien) was investigated using differential scanning calorimetry (DSC), UV-vis spectrometer and FT-IR. DSC measurement showed two distinct exothermic peaks on the curing curves, indicating that the reaction consisted of two reactive species. The first peak at low temperature corresponded to the amine-epoxy reaction with the activation energy of 46.85 kJ · mol^?1 and the second peak corresponded to the hydroxyl-epoxy reaction with the activation energy of 74.23 kJ · mol^?1. As the concentration of Ni(sal)₂trien increased, the amine–epoxy reaction was favored, and the temperature of the hydroxyl-epoxy reaction decreased at the same time.     

Detailed Kinetics of the Fischer�CTropsch Synthesis on Cobalt Catalysts Based on H-Assisted CO Activation

A complete mechanistic kinetic model of the Fischer?CTropsch synthesis (FTS) over a Co/Al₂O₃ state-of-the-art catalyst is developed here under conditions relevant to industrial operation. On the basis of the most recent findings on the reaction mechanism, here described according to the H-assisted CO dissociation theory and the alkyl chain growth mechanism, and on the basis of the latest indications available on the rate determining step involved in the CO activation process, rate expressions for all the steps leading to CO and H₂ consumption and n-paraffins, ??-olefins and H₂O formation are derived. Such expressions are functions of the molar fraction of CO, H₂ and olefins in the liquid phase surrounding the catalyst pellets, that in turn are related to the gas-phase pressure and composition, and of the surface coverage of the adsorbed species. Thermodynamic and kinetic parameters involved in the model are estimated by non-linear multi-response regression on a complete set of FTS experimental data collected in a lab-scale tubular reactor at steady-state conditions (P = 8?C25 bar, T = 210?C235 °C, H₂/CO feed ratio = 1.8?C2.7 mol mol^?1, GHSV = 2,000?C7,000 cm³(STP) h^?1 g _cat ^?1 ). Both the experimental CO conversion and the hydrocarbon distribution (up to N = 50) in FTS are well predicted by the model with 13 adaptive parameters, without the need of introducing any empirical parameter. Analysis of the model offers insight in the rates of the elementary steps associated with the reaction mechanism and in the surface coverages of the adsorbed species. Such information explains the peculiar reactivity observed over cobalt-based Fischer?CTropsch catalysts, and can provide guidelines for the design of more active and selective catalytic materials.     

KINETIC MODELS FOR LIQUID-PHASE CATALYTIC OXIDATION OF TOLUENE TO BENZOIC ACID WITH PURE OXYGEN

The liquid phase oxidation of toluene to benzoic acid by pure oxygen has been performed in a bubble reactor by using cobalt acetate tetrahydrate as catalyst. The influence of the oxygen partial pressures on the reaction kinetics were first investigated, and the results showed that the influence was neglectable in the high oxygen pressure range (>0.5 MPa) under 155°C. Thereby, the reaction rates in the oxidation using pure oxygen are independent of the oxygen partial pressure and expressed as the first order to liquid reactants. Based on a kinetic scheme that involves both benzyl alcohol and benzaldehyde, the kinetic models can well describe the reaction process. Furthermore, the results indicated that the production of benzyl alcohol is much slower than its consumption to form benzaldehyde and the scheme can be further simplified to a kinetic equation, which involves only benzaldehyde as intermediate. The simplified reaction scheme also well describes the reaction, and, thus, the derived kinetic models agree well with the experimental data. The reaction constants follow the Arrhenius law. The estimated activation energies are in the range from 92.63 kJ·mol^?1 to 67.81 kJ·mol^?1.     

Carbon Monoxide Oxidation over Au/Ce1−x Zr x O2 Catalysts: Effects of Moisture Content in the Reactant Gas and Catalyst Pretreatment

The Au/Ce_1?x Zr _x O₂ (x = 0, 0.25, 1) catalysts were synthesized, characterized by BET, XRD, TPR-H₂, HRTEM, AAS and tested in CO oxidation. The effect of moisture in the reactant gas on CO conversion has been studied in a wide range of concentrations (~0.7–6000 ppm). Moisture generates a positive effect on catalytic activity and wet conditions gave higher CO conversions. The optimum concentration of moisture for CO oxidation over Au/CeO₂ and Au/Ce_0.75Zr_0.25O₂ is 200–1000 ppm, while further increase in the moisture content suppresses CO conversion. The activity of the studied Au catalysts depends on the amount of moisture adsorbed on the catalyst rather than on its content in the feed stream, which suggests that the reaction involves water-derived species on the catalysts surface. The effect of the catalysts pretreatment in air, dry He, H₂ stream as well as H₂ + H₂O gas mixture on their catalytic performance in CO oxidation has been also investigated. The model of the active sites for CO oxidation over the studied catalysts was proposed.     

Differences in catalytic liquefaction kinetics of corn stalk fractions

Biomass-based polyol obtained by chemical liquefaction technology is a potential substitute for polyether or polyester polyol in preparation of degradable polymers. To obtain the favorable biomass-based polyol products, one important emphasis is to reveal the liquefaction kinetics. The liquefaction kinetics of different corn stalk (CS) fractions, i.e. whole CS, ear husk and leaf blade, were investigated in this work. The liquefactions were catalyzed with sulfuric acid at 120–180 °C for 15–90 min. The results indicated that the apparent reaction rate constant (k), apparent activation energy (E), ΔG′, and ΔH′ of liquefaction reactions differed remarkably with different CS fractions. The highest k of 1.8 × 10^?4 s^?1 was obtained from ear husk liquefaction at 120 °C, which was twofold and 2.7-fold higher than those of whole CS and leaf blade, respectively. However, k is not correlated with the stalk heterogeneity at temperature over 120 °C. The calculated E _{ear husk}, E _{whole CS} and E _{leaf blade} were 65.88, 81.64 and 85.23 kJ mol^?1, respectively. ΔG′ and ΔH′ values of ear husk liquefaction reactions were lower than those of the other two fractions. This work was the first comparison of kinetics with different biomass fractions, casting light on the effect of heterogeneity on liquefaction, and suggesting that CS fractions should be given themselves optimum applications in future.     

Two Gold Surfaces and a Cluster with Remarkable Reactivity for CO Oxidation, a Density Functional Theory Study

We calculate the energetics of CO oxidation on extended surfaces of particular structures chosen to maximize their reactivity towards either O₂ dissociation, after which CO + O to CO₂ is a facile reaction, or to CO₂ from molecular O₂ and CO. We identified two configurations of Au atoms for which the energetics of these reactions are feasible. A site consisting of four Au atoms in a square geometry appears well suited for dissociating oxygen. A Au₃₈ cluster exposing this site provides the most favourable energetics for the CO oxidation.     

Development of a Green Process for the Preparation of Antioxidant and Pigment-Enriched Extracts from Winery Solid Wastes Using Response Surface Methodology and Kinetics

Red grape pomace (RGP), an abundant wine industry solid waste, was used for the recovery of polyphenols and anthocyanin pigments, using ultrasound-assisted extraction and water/glycerol mixtures as the solvent. Glycerol concentration (C_gl) and liquid-to-solid ratio (R_L/S) were first optimized by implementing Box?Behnken experimental design and the process was further studied through kinetics. The optimal conditions were found to be C_gl = 90% (w/v) and R_L/S = 90 mL g^?1, and under these conditions the extraction of total polyphenols (TP) and total pigments (TPm) obeyed first-order kinetics. Maximum diffusivity (D_e) values were 4.22 × 10^?12 and 12.59 × 10^?12 m² s^?1, for TP and TPm, respectively, and the corresponding activation energies were (E_a) 13.94 and 8.22 kJ mol^?1.     

Synthesis and Physicochemical Study of High-Performance Ether-Sulfonate Copolymer

Ether-sulfonate copolymer of 1,1′-bis(4-hydroxyphenyl) cyclohexane, bisphenol-A and 4,4′-disulfonyl chloride diphenyl ether [PESAC] has been synthesized and characterized by IR, ¹H NMR, viscosity ([η] = 0.23–0.25 gdl^?1), density (1.3172 g/cm³), tensile strength (11.8 MPa), electric strength (64 kV/mm), volume resistivity (4.24 × 10¹⁴ Ω cm) and dielectric constant (1.0). PESAC possesses excellent solubility, good hydrolytic stability against water, acids, alkalis and salt, high T_g (170°C) and high thermal stability (290°C). The associated kinetic parameters namely energy of activation E (386.6 kJ mol^?1), order of the reaction n (3.1), frequency factor A (1.53 × 10³¹ s^?1) and entropy change ΔS* (346.1 kJ mol^?1) have been determined and discussed.     

Study on Isothermal Formation Dynamics of Calcium Barium Sulphoaluminate Mineral

The formation dynamics of calcium barium sulphoaluminate mineral with the composition of 2.75CaO·1.25BaO·3Al₂O₃·SO₃ (C_2.75B_1.25A₃ $\overline{\text{S}}$ S ¯ ) was studied. The results suggest that, under the preparative conditions, the formation of C_2.75B_1.25A₃ $\overline{\text{S}}$ S ¯ mineral is controlled by a diffusion mechanism from 1,100 to 1,380 °C; and, the formation dynamics fits nicely with D ₄ = 1 ? 2α/3 ? (1 ? α)^2/3 = Kt. From 1,100 to 1,300 °C, the apparent activation energy is 227.45 kJ mol^?1. From 1,300 to 1,380 °C, the apparent activation energy decreases to 175.94 kJ mol^?1, making the formation of C_2.75B_1.25A₃ $\overline{\text{S}}$ S ¯ mineral faster and easier.     

Characterization of Pt/SiO2 Model Catalysts at UHV and Near Atmospheric Pressures

Pt/SiO₂ model catalyst samples, prepared under UHV conditions in a contiguous high pressure reactor cell surface analysis chamber, have been characterized via CO oxidation reaction kinetics under elevated pressure conditions (approaching 1 atm). Reaction kinetics are studied as a function of Pt coverage (θ _Pt = 1–10 mL), along with measurements on a Pt(110) single crystal for direct comparison. CO desorption measurements and STM measurements on Pt/SiO₂ films at T = 300 K have been obtained at various θ _Pt. Kinetic results show agreement between observations on single crystal and catalyst samples, and general agreement and correlation is obtained for site calculations across the various methods. Results demonstrate the utility of well characterized model catalyst samples in obtaining qualitative and quantitative reactivity data at elevated pressures.     

Low Temperature Catalytic Oxidation of Binary Mixture of Toluene and Acetone in the Presence of Ozone

This work reports on gas phase catalytic ozonation of a binary mixture of toluene and acetone and compares it with catalytic ozonation of single component acetone and toluene. Catalytic ozonation was conducted at 25–90 °C on MnO_x/γ-Al₂O₃ catalyst. XANES and EXAFS were used to identify formal oxidation state of Mn and local structure of manganese oxide in the catalyst. Absorption energy of Mn K-edge of the catalyst was determined to be 6553.86 eV indicating that the majority of manganese in the catalyst was in 3+ oxidation state. Catalytic ozonation in the mixture was favourable for removal of toluene, and repressive for removal of acetone. This was due to (a) lower apparent activation energy of catalytic ozonation of toluene (E_{a, Toluene}?=?31 kJ mol^?1?<?E_{a, Acetone}?=?40 kJ mol^?1) that led to higher reactivity of toluene with active oxygen species, and (b) inhibitory effect of accumulated carbonaceous byproducts on the acetone removal. Increase of reaction temperature enhanced conversion of both compounds, decreased the gap between toluene and acetone conversions, and improved CO_x yield. Overall degradation pathway of toluene and acetone in the mixture was determined by identifying the reaction intermediates and carbonaceous deposits on the catalyst. The observed mixture effects helped to understand potentials and limitations of catalytic ozonation in treating mixture of VOCs, which will aid in developing commercial air treatment systems.

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Polymerization of ethylene dichloride and sodium tetrasulfide: synthesis and kinetic studies

In this work, the kinetics of the condensation polymerization of ethylene dichloride and sodium tetrasulfide is studied. The resulting polymer is characterized by FT-IR, thermogravimetric analysis (TGA), differential thermal analysis (DTA), elemental analyses (CHN), and differential scanning calorimetry (DSC) analysis. The activation energy of the condensation polymerization obtained from an Arrhenius plot is 97.2 kJ mol^?1, and the pre-exponential frequency factor is A = 24.2 min^?1 at a temperature range of 50–70 °C.     

Decomposition of Ethanol Over Ru(0001): A DFT Study

We studied decomposition pathways of ethanol on Ru(0001) with periodic slab-model calculations using a DFT-GGA approach. We calculated the adsorption modes of ethanol and several of its dehydrogenation products and we evaluated reaction energies as well as activation barriers of pertinent dehydrogenation, C–C, and C–O cleavage steps. The calculated barrier heights of C–C and C–O scission steps can be related to the number of hydrogen atoms bound to the C1–C2 and C1–O moieties of the intermediates, respectively. Two counteracting effects are at work, increasing with each dehydrogenation: (i) higher order of the pertinent bond of the adsorbate, and (ii) stronger substrate-surface interaction and thus better stabilization of the transition state. For most intermediates we determined C–O cleavage to be both kinetically and thermodynamically favored over C–C scission, except for the highly dehydrogenated species CH _k CO (k = 1, 2). Based on the calculated energetics, the most likely decomposition pathway, with a rate-determining barrier at 77 kJ·mol^?1, leads to the formation of ketene CH₂CO and subsequent C–C cleavage yielding methylene and CO.     

High temperature oxidation behavior of porous MoAlB ceramic from 800 °C to 1100 °C in air

MoAlB possesses the characteristics of both metals and ceramic materials, which has attracted extensive attention due to its excellent high-temperature oxidation resistance. For this reason, porous MoAlB is considered applicable to the practice of filtration under harsh environment. In this study, the high-temperature oxidation behavior of porous MoAlB ceramics is systematically studied at the temperatures ranging from 800 to 1100 °C. According to the results, the porous MoAlB exhibits good oxidation resistance at a maximum temperature of 1000 °C. The oxidation kinetics of porous MoAlB can be divided into three stages, and the estimated activation energies of the three stages are 253.83 kJ·mol⁻¹, 367.48 kJ·mol⁻¹ and 317.84 kJ·mol⁻¹, respectively. In the stable stage at 1000 °C, the quadratic mass gain per unit area shows linearity over time, and the oxidation rate of porous MoAlB reaches 37.31 mg²·cm⁻⁴·h⁻¹. As revealed by the analysis of the composition and microstructure of oxide layers, the main components of the oxide layer include MoO₃, MoO₂, Al₂O₃, B₂O₃. With the extension of oxidation time, the content of Al₂O₃ in the oxide films increases. The average pore size, permeability and open pore porosity of porous MoAlB show a trend of first decreasing and then tending to be stable. In addition, a discussion is conducted on the high-temperature oxidation mechanism of porous MoAlB.     

Electrocopolymerization of a Binary Mixture of 2-chloroaniline and 2-amino-4-(4-methoxyphenyl) thiazole

Electropolymerization of a binary mixture of 2-chloroaniline and 2-amino-4-(4-methoxyphenyl) thiazole on platinum electrode in acid medium was carried out under varying reaction conditions as temperature, current density, hydrochloric acid, and monomer concentrations with duration time. The initial rate of the electrocopolymerization reaction was small and the rate law was R_P = K₂[D]^0.92[HCl]^0.98[M]^1.93. The apparent activation energy (E_a) was found to be 57.34 kJ mol^?1. The obtained copolymer films were characterized by ¹HNMR, elemental analysis, GPC, IR, UV-visible, and cyclic voltammetry compared with those of the two homopolymers. The mechanism of the electrocopolymerization reaction had been also discussed. The monomer reactivity ratio (r₁ and r₂) was calculated. The thermogravimetric analysis (TGA) was used to confirm the proposed structure and determination of the number of water molecules in the copolymeric chain unit. X-ray and scanning electron microscopic analysis were used to investigate the surface morphology.     

Kinetics of Solvent Extraction of Iron(III) from Sulfate Medium by Purified Cyanex 272 using a Lewis Cell

Abstract

The kinetics of the forward and backward extraction of the title process have been investigated using a Lewis cell operated at 3 Hz and flux or (F) – method of data treatment. The dependences of (F) in the forward extraction on [Fe³⁺], [H₂A₂]_(o), pH, and [HSO₄ ^?] are 1, 0.5, 1, and ?1, respectively. The value of the forward extraction rate constant (k _f ) has been estimated to be 10^?7.37 kmol^3/2 m^?7/2 s^?1. The analysis of the experimentally found flux equation gives the following simple equation: F _f =10^0.13 [FeHSO₄ ²⁺] [A^?], on considering the monomeric model of BTMPPA and the stability constants of Fe(III)‐HSO₄ ^? complexes. This indicates the following elementary reaction occurring in the aqueous film of the interface as rate determining: [FeHSO₄]²⁺+A^?→[FeHSO₄.A]⁺. The very high activation energy of 91 kJ mol^?1 supports this chemical reaction step as rate-determining. The negative value of the entropy change of activation (?94 J mol^?1 K^?1) indicates that the slow chemical reaction step occurs via the S_N2 mechanism.

The backward extraction rate can be expressed by the equation: F _b =10^?5.13 [[FeHSO₄A₂]]_(o) [H⁺] [H₂A₂]_(o) ^?0.5. An analysis of this equation leads to the following chemical reaction step as rate-determining: [FeHSO₄A₂]_(int)→[FeHSO₄A]+A_(i) ^?. However, the activation energy of 24 kJ mol^?1 suggests that the backward extraction process is intermediate controlled with greater contribution of the diffusion of one or the other species as a slow process. The equilibrium constant obtained from the rate study matches well with that obtained from the equilibrium study.     

Electrochemical activity towards ORR of mechanically alloyed PdCo supported on Vulcan carbon and carbon nanospheres

A PdCo catalyst with an atomic ratio of 2:1 was synthesized from elemental powders by mechanical alloying. The structural characterization and composition of the catalyst were determined by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Both the electrocatalytic activity of the catalyst for oxygen reduction in acidic media, as well as attempts to support it on Vulcan XC-72 carbon powder and carbon nanospheres were evaluated by cyclic voltammetry, rotating disc electrode and rotating ring-disk electrode techniques. The X-ray diffraction studies indicated that an intermetallic PdCo compound with an average crystallite size of 25 nm was obtained. According to kinetic and thermodynamic parameters, the electrocatalytic activity of the catalyst toward oxygen reduction was determined as PdCo/CNS > PdCo/C with first-order kinetics, a four-electron multielectronic transference pathway, and a negligible amount of hydrogen peroxide produced. Activation energy values of 40 ± 1 kJ mol^?1 and 68 ± 1 kJ mol^?1 were determined for reactions with PdCo/CNS and PdCo/C, respectively.