Dynamic scaling for Eley‐Rideal reactions over rough surface

Eley‐Rideal reaction mechanism is studied over rough surface of random deposition model. Two types of rough surface are considered: (1) different rough surface with same surface density and (2) different rough surface with different surface density. Dynamic scaling theory, which is generally applied to the growing surface, is applied for this reaction mechanism to obtain the temporal and spatial scaling parameters α and β. The scaling parameters are found to be negative in contrast to the positive scaling parameters in surface growth model. The values of β are the same for both types of surface whereas the values of α are different. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 286–292, 2004     

Direct Hydrogenation of Dinitrogen and Dioxygen via Eley–Rideal Reactions

Most Eley–Rideal abstraction reactions involve an energetic gas‐phase atom reacting directly with a surface adsorbate to form a molecular product. Molecular projectiles are generally less reactive, may dissociate upon collision with the surface, and thus more difficult to prove that they can participate intact in abstraction reactions. Here we provide experimental evidence for direct reactions occurring between molecular N₂⁺ and O₂⁺ projectiles and surface‐adsorbed D atoms in two steps: first, the two atoms of the diatomic molecule undergo consecutive collisions with a metal surface atom without bond rupture; and second, the rebounding molecule abstracts a surface D atom to form N₂D and O₂D intermediates, respectively, detected as ions. The kinematics of the collisional interaction confirms product formation by an Eley–Rideal reaction mechanism and accounts for inelastic energy losses commensurate with surface re‐ionization. Such energetic hydrogenation of dinitrogen may provide facile activation of its triple bond as a first step towards bond cleavage.     

Bent Carbon Surface Moieties as Active Sites on Carbon Catalysts for Phosgene Synthesis

Active sites in carbon‐catalyzed phosgene synthesis from gaseous CO and Cl₂ have been identified using C₆₀ fullerene as a model catalyst. The carbon atoms distorted from sp² coordination in non‐planar carbon units are concluded to generate active Cl₂. Experiments and density functional theory calculations indicate the formation of a surface‐bound [C₆₀???Cl₂] chlorine species with radical character as key intermediate during phosgene formation. It reacts rapidly with physisorbed CO in a two‐step Eley–Rideal‐type mechanism.     

Nitrogen‐doped C60 as a robust catalyst for CO oxidation

The O₂ activation and CO oxidation on nitrogen‐doped C₅₉N fullerene are investigated using first‐principles calculations. The calculations indicate that the C₅₉N fullerene is able to activate O₂ molecules resulting in the formation of superoxide species ( ) both kinetically and thermodynamically. The active superoxide can further react with CO to form CO₂ via the Eley–Rideal mechanism by passing a stepwise reaction barrier of only 0.20 eV. Ab initio molecular dynamics (AIMD) simulation is carried out to evidence the feasibility of the Eley–Rideal mechanism. In addition, the second CO oxidation takes place with the remaining atomic O without any activation energy barrier. The full catalytic reaction cycles can occur energetically favorable and suggest a two‐step Eley–Rideal mechanism for CO oxidation with O₂ catalyzed by the C₅₉N fullerene. The catalytic properties of high percentage nitrogen‐doped fullerene (C₄₈N₁₂) is also examined. This work contributes to designing higher effective carbon‐based materials catalysts by a dependable theoretical insight into the catalytic properties of the nitrogen‐doped fullerene. © 2017 Wiley Periodicals, Inc.     

A DFT study on the possibility of using a single Cu atom incorporated nitrogen-doped graphene as a promising and highly active catalyst for oxidation of CO

Using dispersion-corrected density functional theory (DFT) calculations, a single Cu adatom incorporated nitrogen-doped graphene (CuN₃-Gr) is proposed as a new and highly active noble-metal-free catalyst for carbon monoxide (CO) oxidation reaction. According to our results, the Cu adatom can be stably anchored onto the monovavancy site of the nitrogen-doped graphene, and the resulting large diffusion barrier suggests that the metal clustering is avoided in CuN₃-Gr. Three possible reaction mechanisms for CO oxidation (ie, Eley–Rideal, Langmuir–Hinshelwood, and termolecular Eley–Rideal) are systematically studied. It is found that the activation energy for the rate-determining step of the termolecular Eley–Rideal mechanism is only 0.13 eV, which is much smaller than those of others. The results of this study may provide a useful guideline for the design of highly active and promising single-metal catalysts for the CO oxidation reaction based on graphene.     

Energy Transfer Dynamics of Formate Decomposition on Cu(110)

Energy transfer dynamics of formate (HCOO_a) decomposition on a Cu(110) surface has been studied by measuring the angle‐resolved intensity and translational energy distributions of CO₂ emitted from the surface in a steady‐state reaction of HCOOH and O₂. The angular distribution of CO₂ shows a sharp collimation with the direction perpendicular to the surface, as represented by cosⁿ θ (n= 6). The mean translational energy of CO₂ is measured to be as low as 100 meV and is independent of the surface temperature (T _s). These results clearly indicate that the decomposition of formate is a thermal non‐equilibrium process in which a large amount of energy released by the decomposition reaction of formate is transformed into the internal energies of CO₂ molecules. The thermal non‐equilibrium features observed in the dynamics of formate decomposition support the proposed Eley–Rideal (ER)‐type mechanism for formate synthesis on copper catalysts.     

Ordered Porous Nitrogen‐Doped Carbon Matrix with Atomically Dispersed Cobalt Sites as an Efficient Catalyst for Dehydrogenation and Transfer Hydrogenation of N‐Heterocycles

Single‐atom catalysts (SACs) have been explored widely as potential substitutes for homogeneous catalysts. Isolated cobalt single‐atom sites were stabilized on an ordered porous nitrogen‐doped carbon matrix (ISAS‐Co/OPNC). ISAS‐Co/OPNC is a highly efficient catalyst for acceptorless dehydrogenation of N‐heterocycles to release H₂. ISAS‐Co/OPNC also exhibits excellent catalytic activity for the reverse transfer hydrogenation (or hydrogenation) of N‐heterocycles to store H₂, using formic acid or external hydrogen as a hydrogen source. The catalytic performance of ISAS‐Co/OPNC in both reactions surpasses previously reported homogeneous and heterogeneous precious‐metal catalysts. The reaction mechanisms are systematically investigated using first‐principles calculations and it is suggested that the Eley–Rideal mechanism is dominant.     

A Theoretical Study of the Interaction of Hydrogen and Oxygen with Palladium or Gold Adsorbed on Pyridine‐Like Nitrogen‐Doped Graphene

The interaction of H₂ and O₂ molecules in the presence of nitrogen‐doped graphene decorated with either a palladium or gold atom was investigated by using density functional theory. It was found that two hydrogen molecules were adsorbed on the palladium atom. The interaction of these adsorbed hydrogen molecules with two oxygen molecules generates two hydrogen peroxide molecules first through a Eley–Rideal mechanism and then through a Langmuir–Hinshelwood mechanism. The barrier energies for this reaction were small; therefore, we expect that this process may occur spontaneously at room temperature. In the case of gold, a single hydrogen molecule is adsorbed and dissociated on the metal atom. The interaction of the dissociated hydrogen molecule on the surface with one oxygen molecule generates a water molecule. The competitive adsorption between oxygen and hydrogen molecules slightly favors oxygen adsorption.     

Modeling formation of molecules in the interstellar medium by radical reactions with polycyclic aromatic hydrocarbons

Adsorptions of CH°₂, CH°₃, NH°₂, and OH° radicals and molecule formation on a partially hydrogenated surface of a polycyclic aromatic hydrocarbon (PAH) (C₂₄H₂₇⁺) were modeled. It was found that radical adsorptions are feasible with important modifications of surface bond strengths and bond distances. Adsorbed hydrogen may diffuse due to adsorbate‐surface interactions. Formations of CH₄, NH₃, H₂O, CH₃NH₂, and CH₃OH were studied by Eley‐Rideal (ER) and Langmuir‐Hishelwood (LH) mechanisms. Potential energetic surfaces were performed for both mechanisms and the ER presents lower reaction energy barriers than the LH one, in all cases. Parametric quantum program (CATIVIC) was employed and comparisons with DFT results were performed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2560–2572, 2010     

Three-membered ring formation reaction—III : Mechanism of the reaction of α-halogenoacrylic ester with organozinc compounds

The stereochemistry of ring formation in the reaction of α-halogenoacrylic ester with organozinc compounds was studied using β-deuterated α-halogenoacrylic ester. A quantitative study was made on the steric course of every step of the reactions involved in the synthesis of methyl β-deuterio-α-bromoacrylate-cis-d₁ starting from methyl propiolate. The mode of the CC double bond opening of methyl β-deuterio-α-bromoacrylate-cis-_d1 to form dimethyl 1 -bromo-2-propyl-cis-1,2- cyclopropanedicarboxylate-d₂ was confirmed to be cis and trans in a 50 to 50 ratio. Asymmetric syntheses for the cyclopropanedicarboxylic ester were possible, especially under the influence of chiral organozinc alkoxide system. A stepwise mechanism was postulated for the ring formation reaction.     

Elucidation of Pathways for NO Electroreduction on Pt(111) from First Principles

The mechanism of nitric oxide electroreduction on Pt(111) is investigated using a combination of first principles calculations and electrokinetic rate theories. Barriers for chemical cleavage of N? O bonds on Pt(111) are found to be inaccessibly high at room temperature, implying that explicit electrochemical steps, along with the aqueous environment, play important roles in the experimentally observed formation of ammonia. Use of explicit water models, and associated determination of potential‐dependent barriers based on Bulter–Volmer kinetics, demonstrate that ammonia is produced through a series of water‐assisted protonation and bond dissociation steps at modest voltages (<0.3 V). In addition, the analysis sheds light on the poorly understood formation mechanism of nitrous oxide (N₂O) at higher potentials, which suggests that N₂O is not produced through a Langmuir–Hinshelwood mechanism; rather, its formation is facilitated through an Eley–Rideal‐type process.     

Pt/ZrO2:An Efficient Catalyst for Aerobic Oxidation of Toluene in Aqueous Solution

The heterogeneous oxidation of toluene in aqueous medium has been investigated. Artificially contaminated water with aromatic compound (toluene) was exposed to a simple platinized zirconia (1% Pt/ZrO₂) catalyst in the presence of molecular oxygen. This selective oxidation of toluene to benzyl alcohol, benzaldehyde and benzoic acid provides a step for removing toluene from wastewater or converting it into less harmful substances. Different parameters, e.g. the reaction time, temperature, pressure, the amount of catalyst and agitation, etc influenced the toluene conversion and selectivity. Typical batch reactor kinetic data were obtained and fitted to the classical Langmuir‐Hinshelwood model, Mars‐van Krevelen model as well as to the Eley‐Rideal model of heterogeneously catalyzed reactions. The Eley‐Rideal model was found to give a better fit. 1% Pt/ZrO₂ was observed to be the most active for oxidation of toluene at 333 K in oxygenated atmosphere [p(O₂) ca. 101 kPa] with a nominal stirring speed ≧900 r/min. It was found that catalytic oxidation may be an effective method for the removal of volatile organic compounds from aqueous solutions and comparable to other advanced oxidation processes.     

Esterification reaction kinetics of acetic acid and n-pentanol catalyzed by sulfated zirconia

This study reports experimental data and kinetic modeling of acetic acid esterification with n-pentanol using sulfated zirconia as a catalyst. Reactions were carried out in an isothermal well-mixed batch reactor at different temperatures (50-80°C), n-pentanol to acid molar ratios (1:1-3:1), and catalyst loadings (5-10 wt% in relation to the total amount of acetic acid). The reaction mechanism regarding the heterogeneous catalysis was evaluated considering pseudo-homogeneous, Eley–Rideal, and Langmuir–Hinshelwood model approaches. The reaction mixture was considered a nonideal solution and the UNIQUAC thermodynamic model was used to take into account the nonidealities in the liquid phase. The results obtained indicated that increases in the temperature and catalyst loading increased the product formation, while changes in the n-pentanol to acetic acid molar ratio showed no significant effect. The estimated enthalpy of the reaction was −8.49 kJ mol⁻¹, suggesting a slightly exothermic reaction. The Eley–Rideal model, with acetic acid adsorbed on the catalyst as the limiting step, was found to be the most significant reaction mechanism.     

Nucleosides and nucleotides. Part 7. Four dithymidine monophosphates with different anomeric configurations, their synthesis and behaviour towards phosphodiesterases

The four isomeric dithymidine monophosphates βT_d-βT_d ( 1 ), αT_d-βT_d (2), βT_d-αT_d ( 3 ) and αT_d-αT_d ( 4 ), differing only by the anomeric configurations of the nucleoside units, were prepared from the suitably protected nucleosides and nucleotides. The four dinucleoside monophosphates were tested as substrates of snake venom phosphodiesterase and spleen phosphodiesterase. Both enzymes accept all four compounds as substrates, however, the rate of the hydrolysis is considerably smaller if the enzymic attack takes place at the α-nucleoside moiety of the dinucleoside monophosphate.     

A Comparative Study of CO Oxidation on Nitrogen‐ and Phosphorus‐Doped Graphene

The geometry, electronic structure, and catalytic properties of nitrogen‐ and phosphorus‐doped graphene (N‐/P‐graphene) are investigated by density functional theory calculations. The reaction between adsorbed O₂ and CO molecules on N‐ and P‐graphene is comparably studied via Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) mechanisms. The results indicate that a two‐step process can occur, namely, CO+O₂→CO₂+O_ads and CO+O_ads→CO₂. The calculated energy barriers of the first step are 15.8 and 12.4 kcal mol^?1 for N‐ and P‐graphene, respectively. The second step of the oxidation reaction on N‐graphene proceeds with an energy barrier of about 4 kcal mol^?1. It is noteworthy that this reaction step was not observed on P‐graphene because of the strong binding of O_ads species on the P atoms. Thus, it can be concluded that low‐cost N‐graphene can be used as a promising green catalyst for low‐temperature CO oxidation.     

Spillover in monomer–monomer reactions on supported catalysts: dynamic mean-field study

The kinetics of a $A_1+A_2\rightarrow A_1A_2$ reaction on supported catalysts is investigated numerically using a phenomenological model which includes: the bulk diffusion of reactants from a bounded vessel towards the adsorbent and the product bulk one into the same vessel, adsorption and desorption of reactants molecules, and surface diffusion of adsorbed particles. The model is based on the Langmuir–Hinshelwood surface reaction mechanism coupled with the Eley–Rideal step. The model based only on the Langmuir–Hinshelwood mechanism is also studied. Simulations were performed using the finite difference technique. Three cases of reactants adsorption are considered: each reactant can adsorb on the active in reaction catalyst surface and inactive support, one of reactants adsorbs on the catalyst surface while the other one adsorbs on the support, both reactants adsorb only on the support. The surface diffusion and catalytic surface size influence on the catalytic reactivity of a supported catalyst is studied.     

Theoretical study of the CO catalytic oxidation on Au/SAPO‐11 zeolite

Quantum chemistry calculations were carried out, using ONIOM2 methodology, to investigate the CO adsorption and oxidation on gold supported on Silicoaluminophospates (SAPO) molecular sieves Au/SAPO‐11 catalysts. Two models were studied, one containing one Au atom per site (Au? SAPO‐11), and the other with two Au atoms per site (Au₂? SAPO‐11). The results reveal that the CO adsorption and oxidation are exothermic on Au/SAPO11 with an ΔE of ?41.0 kcal/mol and ΔE = ?52.0 kcal/mol, for the adsorption and oxidation, respectively. On the Au₂? SAPO‐11 model, the CO adsorption and oxidation reaction occur, with a ΔE of ?29.7 kcal/mol and ?52 kcal/mol, respectively. According to our results, the oxidation reaction exhibits an Eley‐Rideal type mechanism with adsorbed CO. The theoretical calculations reveal that this type of material could be interesting to disperse Au and consequently to strengthen its catalytic use for different reactions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2573–2582, 2010     

Catalytic Activity of WO<Subscript>3</Subscript> and MoO<Subscript>3</Subscript> with Pt and Pd Additives in Oxidation of Hydrogen

We have shown that WO₃ and MoO₃ with Pt or Pd additives exhibit high catalytic activity in the reaction of H₂ oxidation. In the temperature range 313 K to 353 K, we have studied the kinetic behavior of the reaction on 0.1 mass % Pt(Pd)/WO₃ and Pt(Pd)/MoO₃ samples. We have established that the kinetics of H₂ oxidation on these catalysts correspond to an Eley - Rideal mechanism. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 313–316, September–October, 2005.     

Thermodynamic scaling of α-relaxation time and viscosity stems from the Johari-Goldstein β-relaxation or the primitive relaxation of the coupling model

By now it is well established that the structural α-relaxation time, τ(α), of non-associated small molecular and polymeric glass-formers obey thermodynamic scaling. In other words, τ(α) is a function Φ of the product variable, ρ(γ)/T, where ρ is the density and T the temperature. The constant γ as well as the function, τ(α) = Φ(ρ(γ)/T), is material dependent. Actually this dependence of τ(α) on ρ(γ)/T originates from the dependence on the same product variable of the Johari-Goldstein β-relaxation time, τ(β), or the primitive relaxation time, τ(0), of the coupling model. To support this assertion, we give evidences from various sources itemized as follows. (1) The invariance of the relation between τ(α) and τ(β) or τ(0) to widely different combinations of pressure and temperature. (2) Experimental dielectric and viscosity data of glass-forming van der Waals liquids and polymer. (3) Molecular dynamics simulations of binary Lennard-Jones (LJ) models, the Lewis-Wahnstr?m model of ortho-terphenyl, 1,4 polybutadiene, a room temperature ionic liquid, 1-ethyl-3-methylimidazolium nitrate, and a molten salt 2Ca(NO(3))(2)·3KNO(3) (CKN). (4) Both diffusivity and structural relaxation time, as well as the breakdown of Stokes-Einstein relation in CKN obey thermodynamic scaling by ρ(γ)/T with the same γ. (5) In polymers, the chain normal mode relaxation time, τ(N), is another function of ρ(γ)/T with the same γ as segmental relaxation time τ(α). (6) While the data of τ(α) from simulations for the full LJ binary mixture obey very well the thermodynamic scaling, it is strongly violated when the LJ interaction potential is truncated beyond typical inter-particle distance, although in both cases the repulsive pair potentials coincide for some distances.     

An investigation of the catalytic performance of Fe–Mn/Al2O3 nanocatalyst for light olefins production using RSM method and kinetic study

The Fe–Mn/Al₂O₃ nanocatalysts were manufactured via the sol-gel procedure and were evaluated for Fischer–Tropsch synthesis. The impact of different operational parameters of T, P, and H₂/CO ratio on the catalytic performance for light olefins production has been studied using response surface methodology (RSM). Furthermore, the optimization and modeling of selected responses were also carried out via RSM and historical data design type of DOE; and the best process conditions were found to be T = 365°C, H₂/CO = 1.50, and P = 1.50 bar. The mechanism of CO hydrogenation reaction over the Fe–Mn/Al₂O₃ nanocatalysts was also investigated using the non-linear regression method. It was found that the mechanism of the CO hydrogenation reaction is based on the Eley–Rideal type and the best-fitted equation for this mechanism was found to be −r_CO = KP_COP_H2/1+αP_CO. The obtained value of activation energy (85.20 kJ mol⁻¹) affirmed the absence of internal mass transfer limitations. The physico-chemical properties of the samples were investigated by various techniques of XRD, BET, TPR, TGA, and DSC.