scholarly journals The Catalysis Effect of Na and Point Defect on NO Heterogeneous Adsorption on Carbon during High-Sodium Zhundong Coal Reburning: Structures, Interactions and Thermodynamic Characteristics

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1046
Author(s):  
Xuesen Kou ◽  
Jing Jin ◽  
Yongzhen Wang ◽  
Yanhui Li ◽  
Fengxiao Hou
Keyword(s):  
Density Functional ◽  
Heterogeneous Reaction ◽  
Exothermic Reaction ◽  
Thermodynamic Characteristics ◽  
Interaction Force ◽  
Pristine Graphene ◽  
Covalent Bonds ◽  
Graphene Surface ◽  
High Sodium ◽  
Zhundong Coal

The reburning process in a furnace, a key way to reduce NOx emissions, is a heterogeneous reaction during coal combustion, in which the heterogeneous adsorption is dominant. Zhundong coal with a high content of alkali metal can enhance the reburning process. In this paper, the influence of sodium and a defect on NO heterogeneous adsorption was studied by the density functional theory, and the thermodynamic characteristic was also analyzed. The results indicate that the binding energy for NO adsorption on the pristine graphene surface (graphene-NO), Na-decorated pristine graphene surface (graphene-Na-NO), defect graphene surface (gsv-NO) and Na-decorated defect graphene (gsv-Na-NO) is −5.86, −137.12, −48.94 and −74.85 kJ/mol, respectively, and that the heterogeneous adsorption is an exothermic reaction. Furthermore, except for covalent bonds of C and N, C and O for gsv-NO, other interactions are a closed-shell one, based on the analysis of AIM, ELF and IGM. The area of electron localization for NO is graphene-Na-NO > gsv-Na-NO > gsv-NO > graphene-NO. The dispersion interaction is the main interaction force between NO and the pristine graphene surface. The δg index for the atom pairs about N–C and O–C on the pristine graphene surface is also the smallest. The density of spikes at graphene-Na-NO is bigger than that at gsv-Na-NO. Moreover, the thermodynamics characteristic showed that the reaction equilibrium constant of graphene-NO is less than those on the other surfaces under the same temperature. Thus, NO on the pristine graphene surface is the most difficult to adsorb, but the presence of sodium and a defect structure can promote its adsorption.

Density functional theory prediction for diffusion of lithium on boron-doped graphene surface

2011 ◽  
Vol 257 (17) ◽  
pp. 7443-7446 ◽  
Author(s):  
Shuanghong Gao ◽  
Zhaoyu Ren ◽  
Lijuan Wan ◽  
Jiming Zheng ◽  
Ping Guo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Functional Theory ◽  
Graphene Surface ◽  
Boron Doped ◽  
Doped Graphene

Structure, Elastic Constants and XRD Spectra of Extended Solids under High Pressure

MRS Advances ◽  
2018 ◽  
Vol 3 (8-9) ◽  
pp. 499-504 ◽  
Author(s):  
I.G. Batyrev ◽  
S.P. Coleman ◽  
J.A. Ciezak-Jenkins ◽  
E. Stavrou ◽  
J.M. Zaug
Keyword(s):  
Elastic Constants ◽  
Energetic Materials ◽  
Density Functional ◽  
Three Dimensional ◽  
Peak Position ◽  
X Ray Diffraction ◽  
Covalent Bonds ◽  
X Ray ◽  
Extended Solids ◽  
Xrd Patterns

ABSTRACTWe present results of evolutionary simulations based on density functional calculations of a potentially new type of energetic materials called extended solids: P-N and N-H. High-density structures with covalent bonds generated using variable and fixed concentration methods were analysed in terms of thermo-dynamical stability and agreement with experimental X-ray diffraction (XRD) spectra. X-ray diffraction spectra were calculated using a virtual diffraction algorithm that computes kinematic diffraction intensity in three-dimensional reciprocal space before being reduced to a two-theta line profile. Calculated XRD patterns were used to search for the structure of extended solids present at experimental pressures by optimizing data according to experimental XRD peak position, peak intensity and theoretically calculated enthalpy. Elastic constants has been calculated for thermodynamically stable structures of P-N system.

First-Principles Study of Ag3Sn, AgZn3 and Ag5Zn8 Intermetallic Compounds

2021 ◽  
Vol 871 ◽  
pp. 254-263
Author(s):  
Zhan Cheng ◽  
Guan Xing Zhang ◽  
Wei Min Long ◽  
Svitlana Maksymova ◽  
Jian Xiu Liu
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Constant Density ◽  
Mulliken Population ◽  
Covalent Bonds ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Anisotropy Index ◽  
Ionic Bonds

The first-principles calculations by CASTEP program based on the density functional theory is applied to calculate the cohesive energy, enthalpy of formation, elastic constant, density of states and Mulliken population of Ag3Sn、AgZn3 and Ag5Zn8. Furthermore, the elastic properties, bonding characteristics, and intrinsic connections of different phases are investigated. The results show that Ag3Sn、AgZn3 and Ag5Zn8 have stability structural, plasticity characteristics and different degrees of elastic anisotropy; Ag3Sn is the most stable structural, has the strongest alloying ability and the best plasticity. AgZn3 is the most unstable structure, has the worst plasticity; The strength of Ag5Zn8 is strongest, AgZn3 has the weakest strength, the largest shear resistance, and the highest hardness. Ag5Zn8 has the maximum Anisotropy index and Ag3Sn has the minimum Anisotropy index. Ag3Sn、AgZn3 and Ag5Zn8 are all have covalent bonds and ionic bonds, the ionic bonds decrease in the order Ag3Sn>Ag5Zn8>AgZn3 and covalent bonds decreases in the order Ag5Zn8>Ag3Sn>AgZn3.

Structure and electron density of oxysulfide Sm2Ti2S2O4.9, a visible-light-responsive photocatalyst

2008 ◽  
Vol 64 (3) ◽  
pp. 291-298 ◽  
Author(s):  
Masatomo Yashima ◽  
Kiyonori Ogisu ◽  
Kazunari Domen
Keyword(s):  
Dft Calculations ◽  
Visible Light ◽  
Valence Band ◽  
Electron Density ◽  
Diffraction Data ◽  
Density Functional ◽  
Oxygen Deficiency ◽  
Covalent Bonds ◽  
Synchrotron Powder Diffraction ◽  
Visible Wavelengths

We report the crystal structure and electron density of samarium titanium oxysulfide, Sm2Ti2S2O4.9, photocatalyst obtained through the Rietveld analysis, maximum-entropy method (MEM) and MEM-based pattern fitting of the high-resolution synchrotron powder diffraction data taken at 298.7 K. The Sm2Ti2S2O4.9 has a tetragonal structure with the space group I4/mmm. Refined occupancy factors at the `equatorial' O1 and `apical' O2 sites were 0.994 (3) and 0.944 (12), respectively, which strongly suggest oxygen deficiency at the O2 site. Electron-density analyses based on the synchrotron diffraction data of Sm2Ti2S2O4.9 in combination with density-functional theory (DFT) calculations of stoichiometric Sm2Ti2S2O5 reveal covalent bonds between Ti and O atoms, while the Sm and S atoms are more ionic. The presence of S 3p and O 2p orbitals results in increased dispersion of the valence band, raising the top of the valence band and making the material active at visible wavelengths. The present DFT calculations of stoichiometric Sm2Ti2S2O5 indicate the possibility of overall splitting of water, although Sm2Ti2S2O4.9 works as a visible-light-responsive photocatalyst in aqueous solutions only in the presence of sacrificial electron donors or acceptors. The oxygen deficiency and cocatalyst seem to be factors affecting the catalytic activity.

Theoretical study on the electronic structure, mechanical property, and thermal expansion of yttrium oxysulfide

2015 ◽  
Vol 04 (01) ◽  
pp. 1550004
Author(s):  
Ruipeng Gao ◽  
Yefei Li
Keyword(s):  
Mechanical Property ◽  
Thermal Expansion ◽  
Electronic Structure ◽  
Bulk Modulus ◽  
Density Functional ◽  
Theoretical Study ◽  
Spherical Shape ◽  
Weak Anisotropy ◽  
Covalent Bonds ◽  
Very High

The electronic structure, mechanical property and thermal expansion of yttrium oxysulfide are calculated from first-principles using the theory of density functional. The calculated cohesive energy indicates its thermodynamic stable nature. From bond structure, the calculated bandgap is obtained as 2.7 eV; and strong covalent bonds exist between Y and O atoms intra 2D [ Y – O ] layer in material, while relatively weak covalent bonds also exist inter 2D [ Y – O ] layer and S atoms. From simulation, it is found that the bulk modulus is about 119.4 GPa for the elastic constants, and the bulk modulus shows weak anisotropy because the surface contours of them are close to a spherical shape. The calculated B/G clearly implies its ductile nature, and the Y 2 O 2 S phase can also be compressed easily. The temperature dependence of thermal expansions is mainly caused by the restoration of thermal energy due to lattice excitations at low temperature. When the temperature is very high, the thermal expansion coefficient increases linearly with temperature increasing. Meanwhile, the heat capacities are also calculated and discussed by thermal expansion and elasticity.

N2 and CO Desorption from Interaction between NO and Nitrogen-Containing Char

2013 ◽  
Vol 860-863 ◽  
pp. 985-988
Author(s):  
Xiu Xia Zhang ◽  
Zhi Jun Zhou ◽  
Jun Hu Zhou ◽  
Ke Fa Cen
Keyword(s):  
Density Functional Theory ◽  
Simulation Study ◽  
Reaction Mechanisms ◽  
Density Functional ◽  
Heterogeneous Reaction ◽  
Reaction Pathways ◽  
Functional Theory ◽  
Exothermic Process ◽  
Axis Parallel ◽  
No Chemisorption

A comprehensive molecular simulation study on heterogeneous reaction mechanisms of NO with nitrogen-containing char is carried out using density functional theory. NO chemisorption and subsequent possible reaction pathways are proposed. Geometries of reactants, products, stable intermediates and transition states are optimized at B3LYP/6-31G(d) level. It is found that NO molecule chemisorption with its bond axis parallel to the edge line of nitrogen-containing char is a weakly exothermic process. The N-O bond in NO molecule tends to dissociate after chemisorption. N2 and CO are desorbed when NO molecules are chemisorbed with the formation of N-N bond. N2 desorption is exothermic, while CO desorption is endothermic. So we conclude that N2 is the dominant product from interaction between NO and nitrogen-containing char.

scholarly journals The characteristics of mineralogy, morphology and sintering during co-combustion of Zhundong coal and oil shale

RSC Advances ◽  
2017 ◽  
Vol 7 (81) ◽  
pp. 51036-51045 ◽  
Author(s):  
Yang Lu ◽  
Ying Wang ◽  
Yuqiong Zhao ◽  
Zheng Wei ◽  
Yuan Li ◽  
...  
Keyword(s):  
Oil Shale ◽  
High Sodium ◽  
Zhundong Coal

The high-sodium coal from the Zhundong region induces severe ash-related problems during combustion.

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