Reaction Mechanisms of H2 Reduction and N2O Decomposition on Fe/ZSM-5 Zeolite: A Density Functional Theoretical Study

2009 ◽  
Vol 113 (42) ◽  
pp. 18184-18190 ◽  
Author(s):  
Gang Yang ◽  
Lijun Zhou ◽  
Xianchun Liu ◽  
Xiuwen Han ◽  
Xinhe Bao
Keyword(s):  
Reaction Mechanisms ◽  
Density Functional ◽  
Theoretical Study ◽  
N2o Decomposition ◽  
Zeolite A

Formation of β-O-4 Lignin Models -A Theoretical Study

Holzforschung ◽  
2003 ◽  
Vol 57 (5) ◽  
pp. 466-478 ◽  
Author(s):  
B. Durbeej ◽  
L. A. Eriksson
Keyword(s):  
Reaction Mechanisms ◽  
Density Functional Calculations ◽  
Energy Barrier ◽  
Density Functional ◽  
Theoretical Study ◽  
Coniferyl Alcohol ◽  
Quinone Methide ◽  
Reaction Energy ◽  
Alcohol Radical

Summary The formation of two different β-O-4 lignin models is investigated by means of density functional calculations. It is found that the coupling of two coniferyl alcohol radicals forming a quinone methide proceeds by an energy barrier of ~2–5 kcal/mol, and that the associated reaction energy is negative by more than 20 kcal/mol. On the basis of the corresponding results obtained for the coupling of a coniferyl alcohol radical to a coniferyl alcohol, it is argued that the resulting radical, albeit being formed in an energetically less favourable process, might play an important role in lignin polymerisation. Finally, two different reaction mechanisms for the conversion of a quinone methide into a guaiacylglycerol-β-coniferyl ether dilignol through the addition of water are explored.

Conversion of Cyclic Xylose into Xylitol on the Ru, Pt, Pd, Ni, and Rh Catalysts: A Density Functional Theory Study

2021 ◽  
Author(s):  
Shedrack G. Akpe ◽  
Sun Hee Choi ◽  
Hyung Chul Ham
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanisms ◽  
Density Functional ◽  
Theoretical Study ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Proper Understanding

There is currently no theoretical study on the hydrogenation of xylose to xylitol on a catalyst's surface, limiting proper understanding of the reaction mechanisms and the design of effective catalysts....

Identifying the effective phosphorous species over modified P-ZSM-5 zeolite: a theoretical study

2018 ◽  
Vol 20 (17) ◽  
pp. 11702-11712 ◽  
Author(s):  
Yueying Chu ◽  
Xiuzhi Gao ◽  
Xin Zhang ◽  
Guangtong Xu ◽  
Guangchao Li ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Dft Study ◽  
Coke Deposition ◽  
Zeolite A ◽  
Functional Theory ◽  
Zeolite P

In this work, a density functional theory (DFT) study was carried out to address the fundamental description of the effective phosphorous species that could improve the framework stability and reduce the coke deposition formation on the P-ZSM-5 zeolite.

scholarly journals Theoretical Study of Zirconium Isomorphous Substitution into Zeolite Frameworks

Molecules ◽  
2019 ◽  
Vol 24 (24) ◽  
pp. 4466
Author(s):  
Duichun Li ◽  
Bin Xing ◽  
Baojun Wang ◽  
Ruifeng Li
Keyword(s):  
Acid Site ◽  
Density Functional ◽  
Theoretical Study ◽  
Atomic Radius ◽  
Acid Sites ◽  
Isomorphous Substitution ◽  
Dispersion Correction ◽  
Brønsted Acidity ◽  
Functional Theory ◽  
Brönsted Acidity

Systematic periodic density functional theory computations including dispersion correction (DFT-D) were carried out to determine the preferred location site of Zr atoms in sodalite (SOD) and CHA-type topology frameworks, including alumino-phosphate-34 (AlPO-34) and silico-alumino-phosphate-34 (SAPO-34), and to determine the relative stability and Brönsted acidity of Zr-substituted forms of SOD, AlPO-34, and SAPO-34. Mono and multiple Zr atom substitutions were considered. The Zr substitution causes obvious structural distortion because of the larger atomic radius of Zr than that of Si, however, Zr-substituted forms of zeolites are found to be more stable than pristine zeolites. Our results demonstrate that in the most stable configurations, the preferred favorable substitutions of Zr in substituted SOD have Zr located at the neighboring sites of the Al-substituted site. However, in the AlPO-34 and SAPO-34 frameworks, the Zr atoms are more easily distributed in a dispersed form, rather than being centralized. Brönsted acidity of substituted zeolites strongly depends on Zr content. For SOD, substitution of Zr atoms reduces Brönsted acidity. However, for Zr-substituted forms of AlPO-34 and SAPO-34, Brönsted acidity of the Zr-O(H)-Al acid sites are, at first, reduced and, then, the presence of Zr atoms substantially increased Brönsted acidity of the Zr-O(H)-Al acid site. The results in the SAPO-34-Zr indicate that more Zr atoms substantially increase Brönsted acidity of the Si-O(H)-Al acid site. It is suggested that substituted heteroatoms play an important role in regulating and controlling structural stability and Brönsted acidity of zeolites.

Reactivity and reaction mechanisms of sulfate radicals with lindane: An experimental and theoretical study

2021 ◽  
pp. 111523
Author(s):  
Lei He ◽  
Lingjun Bu ◽  
Richard Spinney ◽  
Dionysios D. Dionysiou ◽  
Ruiyang Xiao
Keyword(s):  
Reaction Mechanisms ◽  
Theoretical Study ◽  
Sulfate Radicals

Substituent effect on N–H bond dissociation enthalpies of carbamates: a theoretical study

2015 ◽  
Vol 93 (3) ◽  
pp. 279-288 ◽  
Author(s):  
Rupinder preet Kaur ◽  
Damanjit Kaur ◽  
Ritika Sharma
Keyword(s):  
Substituent Effect ◽  
Density Functional ◽  
Theoretical Study ◽  
Natural Bond Orbital ◽  
Stabilization Energy ◽  
Isodesmic Reactions ◽  
Bond Dissociation ◽  
Density Functional Methods ◽  
Functional Methods ◽  
Orbital Analysis

The present investigation deals with the study of the N–H bond dissociation enthalpies (BDEs) of the Y-substituted (NH2-C(=X)Y-R) and N-substituted ((R)(H)NC(=X)YH) carbamates (X, Y = O, S, Se; R = H, CH3, F, Cl, NH2), which have been evaluated using ab initio and density functional methods. The variations in N−H BDEs of these Y-substituted and N-substituted carbamates as the effect of substituent have been understood in terms of molecule stabilization energy (ME) and radical stabilization energy (RE), which have been calculated using the isodesmic reactions. The natural bond orbital analysis indicated that the electrodelocalization of the lone pairs of heteroatoms in the molecules and radicals affect the ME and RE values depending upon the type and site of substitution (whether N- or Y-). The variations in N−H BDEs depend upon the combined effect of molecule stabilization and radical stabilization by the various substituents.

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