scholarly journals Mechanism of Guaiacol Hydrodeoxygenation on Cu (111): Insights from Density Functional Theory Studies

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 523
Author(s):  
Destiny Konadu ◽  
Caroline Rosemyya Kwawu ◽  
Richard Tia ◽  
Evans Adei ◽  
Nora Henriette de Leeuw
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Reaction Path ◽  
Binding Energies ◽  
Functional Theory ◽  
Thermodynamics And Kinetics ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
The Density Functional Theory ◽  
Rate Limiting

Understanding the mechanism of the catalytic upgrade of bio-oils via the process of hydrodeoxygenation (HDO) is desirable to produce targeted oxygen-deficient bio-fuels. We have used calculations based on the density functional theory to investigate the reaction mechanism of HDO of guaiacol over Cu (111) surface in the presence of H2, leading to the formation of catechol and anisole. Our analysis of the thermodynamics and kinetics involved in the reaction process shows that catechol is produced via direct demethylation, followed by dehydrogenation of –OH and re-hydrogenation of catecholate in a concerted fashion. The de-methylation step is found to be the rate-limiting step for catechol production with a barrier of 1.97 eV. Formation of anisole will also proceed via the direct dehydroxylation of guaiacol followed by hydrogenation. Here, the rate-limiting step is the dehydroxylation step with an energy barrier of 2.07 eV. Thermodynamically, catechol formation is favored while anisole formation is not favored due to the weaker interaction seen between anisole and the Cu (111) surface, where the binding energies of guaiacol, catechol, and anisole are -1.90 eV, −2.18 eV, and −0.72 eV, respectively. The stepwise barriers also show that the Cu (111) surface favors catechol formation over anisole as the rate-limiting barrier is higher for anisole production. For catechol, the overall reaction is downhill, implying that this reaction path is thermodynamically and kinetically preferred and that anisole, if formed, will more easily transform.

scholarly journals Density functional theory calculations on the CO catalytic oxidation on Al-embedded graphene

RSC Advances ◽  
2014 ◽  
Vol 4 (39) ◽  
pp. 20290-20296 ◽  
Author(s):  
Q. G. Jiang ◽  
Z. M. Ao ◽  
S. Li ◽  
Z. Wen
Keyword(s):  
Density Functional Theory ◽  
Co Oxidation ◽  
Energy Barrier ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Co Catalytic Oxidation ◽  
Rate Limiting

The energy barrier of the CO oxidation for the rate limiting step on Al-embedded graphene is only 0.32 eV.

Mechanisms of Diffusion and Dissociation of E-Centers in Silicon

2005 ◽  
Vol 237-240 ◽  
pp. 1129-1134
Author(s):  
Mariya G. Ganchenkova ◽  
V.A. Borodin ◽  
Risto M. Nieminen
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Density Functional ◽  
Kinetic Monte Carlo ◽  
Binding Energies ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Charge States

In this paper we discuss possible mechanisms of PV annealing in Si. Our approach includes a combination of density functional theory and lattice kinetic Monte-Carlo (LKMC) simulations. The density functional theory is used to find the binding energies and jump barriers for P-V pair at different separations (from one to three interatomic bonds between complex constituents) and in different charge states. The mobility of the complex is simulated by LKMC with event probabilities calculated based on the energies from ab-initio calculations. .

DECOMPOSITION OF SiH4 ON THE SA TYPE STEPPED Si(100) SURFACE

2002 ◽  
Vol 09 (03n04) ◽  
pp. 1401-1407 ◽  
Author(s):  
ŞENAY KATIRCIOĞlu ◽  
ŞAKIR ERKOÇ
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Density Functional ◽  
Reaction Path ◽  
Density Functional Theory Method ◽  
Dissociative Adsorption ◽  
Theory Method ◽  
Functional Theory ◽  
Initial Stage ◽  
The Density Functional Theory

The density functional theory method is used to explore the mechanism of dissociative adsorption of silane (SiH4) on the SA type stepped Si(100) surface. Two reaction paths are described that produce silyl (SiH3) and hydrogen atom fragments adsorbed on the dimer bonds present on each terrace. It has been found that the initial stage of the dissociation of SiH4 on the SA type stepped Si(100) surface shows similarity to the dissociation of SiH4 on the flat Si(100) surface; SiH3 and hydrogen fragments bond to the Si dimer atoms by following the first reaction path.

Density functional theory study on CO adsorption on the PdnAl (n = 1–5) clusters

2018 ◽  
Vol 32 (15) ◽  
pp. 1850187 ◽  
Author(s):  
Zhi Li ◽  
Zhonghao Zhou ◽  
Zhen Zhao ◽  
Qi Wang
Keyword(s):  
Density Functional Theory ◽  
Ground State ◽  
Density Functional ◽  
Co Adsorption ◽  
Binding Energies ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Energy Configurations ◽  
Homo Lumo

The configurations, stability, electronic properties and CO adsorption of the ground state Pd[Formula: see text]Al (n = 1–5) clusters are calculated by the density functional theory (DFT). The results reveal that the lowest-energy configurations of Pd[Formula: see text]Al clusters inherit the geometries of the host Pd[Formula: see text] clusters to a larger extent. The C atom in CO molecule prefers to approach more Pd atoms rather than Al atoms in small Pd[Formula: see text]Al clusters. Pd[Formula: see text]AlCO clusters have higher average binding energies than the corresponding small Pd[Formula: see text]CO clusters except for PdCO. AlCO and Pd3AlCO clusters possess better kinetic stability than their neighbors by the HOMO–LUMO gaps. Except for Pd6 clusters, CO molecule prefers to adsorb on small Pd[Formula: see text] clusters rather than Pd[Formula: see text]Al clusters. Both the Al–Pd bonding in Pd[Formula: see text]Al clusters and C–Pd bonding in Pd[Formula: see text]AlCO clusters have certain covalent characters.

THEORETICAL INVESTIGATION ON THE ACTIVATION OF ETHANE VIA NICKEL ATOM CATALYSIS

2007 ◽  
Vol 06 (02) ◽  
pp. 323-330 ◽  
Author(s):  
LAI-CAI LI ◽  
JUN-LING LIU ◽  
JING SHANG ◽  
XIN WANG ◽  
NING-BEW WONG
Keyword(s):  
Density Functional ◽  
Bond Activation ◽  
Theoretical Work ◽  
Nickel Atom ◽  
Functional Theory ◽  
Activation Pathway ◽  
Rate Determining Step ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

The reaction mechanism of the activation of ethane by nickel atom has been investigated by density functional theory (DFT). The geometries and vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311 + +G(d, p) level. Two main pathways, C – C bond activation and C – H bond activation, are identified. In former channel, the rate-limiting step is found to be hydrogen-transferring step with a high barrier of 227 kJ · mol-1. In the C – H bond activation pathway, the second hydrogen-transferring step is the rate-determining step of the whole reaction. The barrier of the step is 71 kJ · mol-1. Our results show that the studied reaction would undergo along C – H bond activation pathway to form the products H 2 molecule and Ni ⋯ethene complex. The present theoretical work indicates that Ni atom is more active than Ni + cation in activating ethane.

Boron Diffusion Mechanism in Silicon Oxide Using AB Initio Methods

2000 ◽  
Vol 610 ◽  
Author(s):  
V. Zubkov ◽  
J. P. Senosiain ◽  
S. Aronowitz ◽  
V. Sukharev ◽  
C. B. Musgrave
Keyword(s):  
Density Functional ◽  
Silicon Oxide ◽  
Diffusion Mechanism ◽  
Activation Energies ◽  
Boron Diffusion ◽  
Functional Theory ◽  
Model Cluster ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

AbstractDensity functional theory was employed to explore the diffusion mechanism of boron in amorphous silicon oxide. The oxide was modeled with clusters of various sizes, and both neutral boron atoms and cations were considered. Three stable structures were found where B (or B+) was inserted into oxide: one in which B (or B+) is divalent and two in which B (or B+) is trivalent. Boron diffusion through silicon oxide proceeds as a sequence of B hops from one inserted position to another. For neutral boron the rate limiting step is B hop from one of trivalent structures to a divalent one with activation energies (Ea) in the range of 2.0-3.1 eV, depending on the model cluster. In the case of a cation the rate-limiting step is the B+ hop over the O atom in a divalent structure Si-B+-O-Si with calculated Ea of 2.4-2.8 eV. Experimental activation energies for B diffusion in silicon oxide are in the 2.3 - 4.2 eV range. Our results suggest that both neutral and cation boron can participate in B diffusion in oxide.

QUANTUM MECHANICAL MODELING OF THE COBALT MONOLAYER BEHAVIOR ON A TIC SURFACE

2020 ◽  
Author(s):  
Антон Александрович Гниденко
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Cobalt Atom ◽  
Binding Energies ◽  
Pseudopotential Method ◽  
Quantum Mechanical ◽  
Mechanical Modeling ◽  
Functional Theory ◽  
The Density Functional Theory

Методами теории функционала плотности и псевдопотенциала исследована адгезия монослоя кобальта с поверхностью TiC(001). Показана необходимость поворота монослоя кобальта относительно подложки для получения достоверных результатов. Рассмотрены две стабильные атомные конфигурации для системы 4TiC/5Co, рассчитаны энергии связи, приходящиеся на один атом кобальта. The adhesion of a cobalt monolayer on the TiC (001) surface is studied using the density functional theory and pseudopotential method. The necessity of cobalt monolayer rotation relative to the substrate to obtain reliable results is shown. Two stable atomic configurations for the 4TiC/5Co system are considered, and the binding energies per cobalt atom are calculated.

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