scholarly journals Stimulation Calculation of Desulfurization Mechanisms Dominated by Free Radicals Reactions During Pyrolysis of Thiophenes Under Water Vapor Atmosphere

2021 ◽  
Author(s):  
Ya Cheng ◽  
Jianping Chen ◽  
Huiqing Guo ◽  
Yanqiu Lei ◽  
Fenrong Liu
Keyword(s):  
Free Radicals ◽  
Water Vapor ◽  
Density Functional ◽  
Weak Interactions ◽  
Initial Energy ◽  
State Theory ◽  
Energy Barriers ◽  
Elementary Reactions ◽  
Water Vapor Atmosphere ◽  
Higher Temperature

Abstract The desulfurization mechanisms of thiophene and 2-methyl thiophene were investigated by the density functional theory (DFT) during pyrolysis under water vapor atmosphere. All possible reaction pathways of these desulfurization mechanisms were explored at M06-2X/6-311g (d) level. The Multwfn3.0 and VMD1.9.2 programs were used to analyze weak interactions between thiophene compounds and H2O molecule. It can be seen that hydrogen bonds can be formed in the reactions of thiophene sulfurs and H2O. Since H2O molecule can decompose at higher temperature and generate free radicals, such as·H and·OH,, the desulfurization mechanisms of thiophene and 2-methyl thiophene with free radicals need to be further considered. The reaction energy barriers (∆G≠) and reaction energies (∆GP) of thiophene and 2-methyl thiophene with H2O molecule (g) or free radicals (·H and·OH) have been stimulated and calculated in detail. Based on the transition state theory (TST), the rate constants corresponding to these elementary reactions are also calculated, meanwhile the speed and spontaneity of every reaction can be obtained from the aspect of kinetics. Theoretically, it is found that H2O (g) directly attacking C-S bonds of thiophene and 2-methyl thiophene cannot easily generate COS and H2S even at 1200 K in terms of thermodynamics and kinetics. If the desulfurization mechanisms of thiophenes are investigated by free radicals mechanisms under steam atmosphere, their initial energy barriers needing to be overcome significantly reduce. Therefore, desulfurization mechanisms of thiophenes and H2O (g) are the most possibly dominated by radical reactions at higher temperatures and H2S is mainly generated.

THEORETICAL MECHANISMS AND KINETICS FOR THE REACTION OF DIMETHYL SULFIDE AND OZONE IN WATER VAPOR

2005 ◽  
Vol 04 (04) ◽  
pp. 1101-1117 ◽  
Author(s):  
ANGELA SHIH ◽  
CALINA CIOBANU ◽  
FU-MING TAO
Keyword(s):  
Water Vapor ◽  
Transition State ◽  
Rate Constants ◽  
Energy Barrier ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
State Theory ◽  
Second Order ◽  
Water Molecules ◽  
Phase Reaction

The reaction mechanisms and kinetics for DMS + O 3 ⇒ DMSO + O 2 in water vapor are studied using density functional theory. A series of reaction pathways are determined with molecular clusters containing the reacting species and up to three water molecules. The results show that the energy barrier, defined as the energy difference between the reactant complex and the transition state, decreases progressively as each water molecule is added to the reacting system. A decreasing energy barrier is attributed to favorable electrostatic interactions between the reacting species and water at the transition state and at the more polar product. Rate constants for the second-order reactions, involving different combinations of hydrated reactants up to three water molecules, are calculated using transition state theory with Eckart tunneling corrections. Effective rate constants for DMS + O 3 ⇒ DMSO + O 2 are obtained using the calculated second-order rate constants and the concentrations of hydrated reactants present in saturated water vapor. The results show that the rate of reaction for DMS + O 3 ⇒ DMSO + O 2 increases dramatically in the presence of water vapor, by up to seven orders of magnitude for reactions involving three water molecules. The study implies that the gas-phase reaction of DMS with ozone is significant in the troposphere and can greatly influence the global climate.

scholarly journals In-situ NiO nanostructure growth during heating in water vapor atmosphere

2021 ◽  
Vol 27 (S1) ◽  
pp. 2102-2103
Author(s):  
Boyi Qu ◽  
Klaus van Benthem
Keyword(s):  
Water Vapor ◽  
Water Vapor Atmosphere

scholarly journals Oxidation Behavior of Maraging 300 Alloy Exposed to Nitrogen/Water Vapor Atmosphere at 500 °C

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1021
Author(s):  
Mauro Andres Cerra Florez ◽  
Gemma Fargas Ribas ◽  
Jorge Luiz Cardoso ◽  
Antonio Manuel Mateo García ◽  
Joan Josep Roa Rovira ◽  
...  
Keyword(s):  
Water Vapor ◽  
Oxide Layer ◽  
Magnetic Layer ◽  
Adhesive Force ◽  
Point Of View ◽  
Maraging Steels ◽  
Cobalt Spinel ◽  
Water Vapor Atmosphere ◽  
Iron Nickel ◽  
Ferrite Cobalt

Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows to induce a thin magnetic layer in a mixture of iron, nickel, and cobalt spinel ferrites. On the other hand, the oxide layer presents an adhesive force 99 mN value that shows the capability for being used for tribological applications under sliding contact tests.

scholarly journals Weak Interactions in Cocrystals of Isoniazid with Glycolic and Mandelic Acids

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 328
Author(s):  
Raquel Álvarez-Vidaurre ◽  
Alfonso Castiñeiras ◽  
Antonio Frontera ◽  
Isabel García-Santos ◽  
Diego M. Gil ◽  
...  
Keyword(s):  
Density Functional ◽  
Glycolic Acid ◽  
Weak Interactions ◽  
Three Dimensional ◽  
Functional Theory ◽  
Molecular Systems ◽  
X Ray Crystallography ◽  
Hydroxycarboxylic Acids ◽  
Non Covalent Interactions ◽  
Covalent Interactions

This work deals with the preparation of pyridine-3-carbohydrazide (isoniazid, inh) cocrystals with two α-hydroxycarboxylic acids. The interaction of glycolic acid (H2ga) or d,l-mandelic acid (H2ma) resulted in the formation of cocrystals or salts of composition (inh)·(H2ga) (1) and [Hinh]+[Hma]–·(H2ma) (2) when reacted with isoniazid. An N′-(propan-2-ylidene)isonicotinic hydrazide hemihydrate, (pinh)·1/2(H2O) (3), was also prepared by condensation of isoniazid with acetone in the presence of glycolic acid. These prepared compounds were well characterized by elemental analysis, and spectroscopic methods, and their three-dimensional molecular structure was determined by single crystal X-ray crystallography. Hydrogen bonds involving the carboxylic acid occur consistently with the pyridine ring N atom of the isoniazid and its derivatives. The remaining hydrogen-bonding sites on the isoniazid backbone vary based on the steric influences of the derivative group. These are contrasted in each of the molecular systems. Finally, Hirshfeld surface analysis and Density-functional theory (DFT) calculations (including NCIplot and QTAIM analyses) have been performed to further characterize and rationalize the non-covalent interactions.

scholarly journals A New Piano-Stool Ruthenium(II) P-Cymene-Based Complex: Crystallographic, Hirshfeld Surface, DFT, and Luminescent Studies

Crystals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 13
Author(s):  
Mohd. Muddassir ◽  
Abdullah Alarifi ◽  
Mohd. Afzal
Keyword(s):  
Density Functional ◽  
Weak Interactions ◽  
Energy Levels ◽  
Hirshfeld Surface ◽  
Binding Energies ◽  
Orbital Energy ◽  
Aminosalicylic Acid ◽  
Full Characterization

A new complex (Ru(η6-p-cymene)(5-ASA)Cl2) (1) where 5-ASA is 5-aminosalicylic acid has been prepared by reacting the ruthenium arene precursors ((η6-arene)Ru(μ-Cl)Cl)2, with the 5-ASA ligands in a 1:1 ratio. Full characterization of complex 1 was accomplished by elemental analysis, IR, and TGA following the structure obtained from a single-crystal X-ray pattern. The structural analysis revealed that complex 1 shows a “piano-stool” geometry with Ru-C (2.160(5)- 2.208(5)Å), Ru-N (2.159(4) Å) distances, which is similar to equivalents sister complex. Density functional theory (DFT) was used to calculate the significant molecular orbital energy levels, binding energies, bond angles, bond lengths, and spectral data (FTIR, NMR, and UV–VIS) of complex 1, consistent with the experimental results. The IR and UV–VIS spectra of complex 1 were computed using all of the methods and choose the most appropriate way to discuss. Hirshfeld surface analysis was also executed to understand the role of weak interactions such as H⋯H, C⋯H, C-H⋯π, and vdW interactions, which play a significant role in the crystal environment’s stability. Moreover, the luminescence results at room temperature show that complex 1 gives a more intense emission band positioned at 465 nm upon excitation at 330 nm makes it a suitable candidate for the building of photoluminescent material.

Evaluation of Li mass loss from Li2TiO3 with excess Li pebbles in water vapor atmosphere

2018 ◽  
Vol 136 ◽  
pp. 362-366 ◽  
Author(s):  
Kazunari Katayama ◽  
Haruaki Sakagawa ◽  
Tsuyoshi Hoshino ◽  
Satoshi Fukada
Keyword(s):  
Water Vapor ◽  
Mass Loss ◽  
Water Vapor Atmosphere

Evolution of Oxide Film of T91 Steel in Water Vapor Atmosphere at 750 °C

2013 ◽  
Vol 81 (3-4) ◽  
pp. 383-392 ◽  
Author(s):  
Guangming Liu ◽  
Caifu Wang ◽  
Fei Yu ◽  
Jihong Tian
Keyword(s):  
Water Vapor ◽  
Oxide Film ◽  
Water Vapor Atmosphere

Applications of ESR to Carbonaceous Materials

1982 ◽  
Vol 36 (1) ◽  
pp. 52-57 ◽  
Author(s):  
L. S. Singer ◽  
I. C. Lewis
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Low Temperature ◽  
Electron Spin ◽  
Paramagnetic Species ◽  
Carbonaceous Materials ◽  
Conduction Electrons ◽  
Spin Resonance ◽  
Higher Temperature ◽  
Low Temperature Pyrolysis

The applications of electron spin resonance (ESR) to carbonaceous materials are reviewed. The stable paramagnetic species observed in the products of low-temperature pyrolysis are odd-alternate neutral free radicals, whereas the unpaired spins of higher temperature carbons and graphites are primarily conduction electrons. The variety of ESR properties and phenomena requires special attention to techniques of measurement and interpretations of results. The relevance to the carbonization process of the free radicals observed by ESR is also discussed.

scholarly journals Mechanochemical Synthesis of a Mercury(II) Metal-Organic Framework Reveals a Two-Dimensional Polymorph Stabilized by Weak Interactions

2019 ◽  
Author(s):  
Isaiah R. Speight ◽  
Igor Huskić ◽  
Mihails Arhangelskis ◽  
Hatem M. Titi ◽  
Robin Stein ◽  
...  
Keyword(s):  
Density Functional ◽  
Weak Interactions ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Density Functional Theory Calculations ◽  
Dimensional Structure ◽  
Reaction Monitoring ◽  
Two Dimensional ◽  
Functional Theory ◽  
Metal Organic

Solid-state mechanochemistry revealed a novel polymorph of the mercury(II) imidazolate framework, based on square-grid (sql) topology layers. Reaction monitoring and periodic density functional theory calculations show that the sql-structure is of higher stability than the previously reported three-dimensional structure, with the unexpected stabilization of a lower dimensionality structure explained by contributions of weak interactions, which include short C-H···Hg contacts.

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