Effects of initial crystal structure of Fe2O3 and Mn promoter on effective active phase for syngas to light olefins

A new solvatomorph of [Au3(1-Methylimidazolate)3] (Au3(MeIm)3)—the simplest congener of imidazolate-based Au(I) cyclic trinuclear complexes (CTCs)—has been identified and structurally characterized. Single-crystal X-ray diffraction revealed a dichloromethane solvate exhibiting remarkably short intermolecular Au⋯Au distances (3.2190(7) Å). This goes along with a dimer formation in the solid state, which is not observed in a previously reported solvent-free crystal structure. Hirshfeld analysis, in combination with density functional theory (DFT) calculations, indicates that the dimerization is generally driven by attractive aurophilic interactions, which are commonly associated with the luminescence properties of CTCs. Since Au3(MeIm)3 has previously been reported to be emissive in the solid-state, we conducted a thorough photophysical study combined with phase analysis by means of powder X-ray diffraction (PXRD), to correctly attribute the photophysically active phase of the bulk material. Interestingly, all investigated powder samples accessed via different preparation methods can be assigned to the pristine solvent-free crystal structure, showing no aurophilic interactions. Finally, the observed strong thermochromism of the solid-state material was investigated by means of variable-temperature PXRD, ruling out a significant phase transition being responsible for the drastic change of the emission properties (hypsochromic shift from 710 nm to 510 nm) when lowering the temperature down to 77 K.

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The symmetry origin of the austenite-cementite orientation relationships in steels

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2018-2108 ◽

2019 ◽

Vol 234 (4) ◽

pp. 237-245 ◽

Cited By ~ 1

Author(s):

Valentin Kraposhin ◽

Alexander Talis ◽

Nenad Simich-Lafitskiy

Keyword(s):

Crystal Structure ◽

Orientation Relationship ◽

Formation Mechanism ◽

Mutual Orientation ◽

Crystallographic Group ◽

Mutual Transformation ◽

Orientation Relationships ◽

Nucleus Formation ◽

Crystallographic Symmetry ◽

Initial Crystal

Abstract The connection between austenite/cementite orientation relationships and crystal structure of both phases has been established. The nucleus formation mechanism at the mutual transformation of austenite and cementite structures has been proposed. Mechanism is based on the interpretation of the considered structures as crystallographic tiling onto triangulated polyhedra, and the said tiling can be transformed by diagonal flipping in a rhombus consisting of two adjacent triangular faces. The sequence of diagonal flipping in the fragment of the initial crystal determines the orientation of the fragment of the final crystal relative to the initial crystal. In case of the mutual austenite/cementite transformation the mutual orientation of the initial and final fragments is coinciding to the experimentally observed in steels Thomson-Howell orientation relationships: ${\left\{ {\bar 103} \right\}_{\rm{C}}}||{\left\{ {111} \right\}_{\rm{A}}};{\rm{}} < {\kern 1pt} 010{\kern 1pt} { > _{\rm{C}}}{\rm{||}} < {\kern 1pt} 10\bar 1{\kern 1pt} { > _{\rm{A}}};\; < {\kern 1pt} 30\bar 1{\kern 1pt} { > _{\rm{C}}}\;||\,\, < {\kern 1pt} \bar 12\bar 1{\kern 1pt} { > _{\rm{A}}}{\rm{}}$ The observed orientation relationship between FCC austenite and cementite is determined by crystallographic group-subgroup relationship between transformation participants, and non-crystallographic symmetry which is determining the transformation of triangulated clusters of transformation participants.

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Influence of initial crystal structure and electrical pulsing on densification of nanocrystalline alumina powder

Journal of Materials Research ◽

10.1557/jmr.1998.0013 ◽

1998 ◽

Vol 13 (1) ◽

pp. 86-89 ◽

Cited By ~ 46

Author(s):

R. S. Mishra ◽

S. H. Risbud ◽

A. K. Mukherjee

Keyword(s):

Crystal Structure ◽

High Density ◽

Theoretical Density ◽

Alumina Powder ◽

Temperature Range ◽

Initial Crystal ◽

Nanocrystalline Alumina

The effect of the crystal structure of starting alumina powder and electric pulsing on the initial stages of densification has been studied in the temperature range of 1200– 1500 °C. Multiple electric pulsing cycles enhance the densification significantly. The α-alumina powders consolidate more readily in comparison to γ-alumina powders. A high density α-alumina specimen (>98% of theoretical density) was obtained at 1300 °C in less than 10 min.

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Catalysts for the Conversion of CO2 to Low Molecular Weight Olefins—A Review

Materials ◽

10.3390/ma14226952 ◽

2021 ◽

Vol 14 (22) ◽

pp. 6952

Author(s):

Barbara Pawelec ◽

Rut Guil-López ◽

Noelia Mota ◽

Jose Fierro ◽

Rufino Navarro Yerga

Keyword(s):

Value Added ◽

Active Phase ◽

Catalyst Design ◽

Light Olefins ◽

Petroleum Processing ◽

Hydrogenation Of Co2 ◽

Advantages And Disadvantages ◽

Olefin Production ◽

Synthesis Of Nanomaterials ◽

Reaction Routes

There is a large worldwide demand for light olefins (C2=–C4=), which are needed for the production of high value-added chemicals and plastics. Light olefins can be produced by petroleum processing, direct/indirect conversion of synthesis gas (CO + H2) and hydrogenation of CO2. Among these methods, catalytic hydrogenation of CO2 is the most recently studied because it could contribute to alleviating CO2 emissions into the atmosphere. However, due to thermodynamic reasons, the design of catalysts for the selective production of light olefins from CO2 presents different challenges. In this regard, the recent progress in the synthesis of nanomaterials with well-controlled morphologies and active phase dispersion has opened new perspectives for the production of light olefins. In this review, recent advances in catalyst design are presented, with emphasis on catalysts operating through the modified Fischer–Tropsch pathway. The advantages and disadvantages of olefin production from CO2 via CO or methanol-mediated reaction routes were analyzed, as well as the prospects for the design of a single catalyst for direct olefin production. Conclusions were drawn on the prospect of a new catalyst design for the production of light olefins from CO2.

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Catalytic Pyrolysis of Naphtha on SHS Catalysts

Eurasian Chemico-Technological Journal ◽

10.18321/ectj21 ◽

2009 ◽

Vol 12 (1) ◽

pp. 17 ◽

Cited By ~ 4

Author(s):

G. Xanthopoulou ◽

G. Vekinis

Keyword(s):

Conversion Efficiency ◽

Strong Interaction ◽

Catalytic Pyrolysis ◽

Catalyst Surface ◽

Active Phase ◽

Light Olefins ◽

High Yield ◽

Partial Substitution ◽

Process Conditions ◽

Thermal Pyrolysis

High yield of light olefins by catalytic pyrolysis of naphtha on spinel-based catalysts is reported. The yields of ethylene and propylene reach over 50% and are at least 10% and 5% higher respectively than the yield using thermal Pyrolysis, under the same process conditions. The partial substitution of Mg by Co in MgAl2O4 and the incorporation of Al2O3, SiO2, MgO, H3BO3 in the spinel and SHS synthesis of KVO3 all increase the catalytic conversion efficiency while at the same time they suppress substantially the formation of coke. It was found that SHS-KVO3 catalytically accelerates the gasification of coke deposited on the catalyst surface and its optimum values were found to be more than 10 wt.%. The addition of B2O3 into the KVO3-based catalyst causes a strong interaction between KVO3 and SHS support, which decreases the loss by evaporation of the active phase

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Manganese-Modified Fe3O4 Microsphere Catalyst with Effective Active Phase of Forming Light Olefins from Syngas

ACS Catalysis ◽

10.1021/acscatal.5b00492 ◽

2015 ◽

Vol 5 (6) ◽

pp. 3905-3909 ◽

Cited By ~ 94

Author(s):

Yi Liu ◽

Jian-Feng Chen ◽

Jun Bao ◽

Yi Zhang

Keyword(s):

Active Phase ◽

Light Olefins

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SELECTION OF BEST CRYSTAL STRUCTURE FOR INITIATING DOCKING-BASED VIRTUAL SCREENING STUDIES OF CDK2 INHIBITORS: A CROSS-DOCKING AND DUD SET VALIDATION APPROACH

INDIAN DRUGS ◽

10.53879/id.56.06.11592 ◽

2019 ◽

Vol 56 (06) ◽

pp. 77-85

Author(s):

A. Joshi ◽

◽

H Bhojwani ◽

U Joshi

Keyword(s):

Crystal Structure ◽

Virtual Screening ◽

Crystal Structures ◽

Active Site ◽

Docking Studies ◽

Cross Docking ◽

Screening Protocol ◽

Initial Crystal ◽

Docking Accuracy ◽

Selection Of

A total of 95 crystal structures of CDK2 were selected after considering criteria such as resolution and absence of missing residues in the active site; and subjected to cross-docking. 14 out of 95 crystal structures exhibited docking accuracy for greater than 70% of ligands at RMSD cut off 2Å in the cross- docking studies. These 14 crystal structures were selected for the second part of the study, which included validation using DUD sets and enrichment calculations. 8 out of 14 crystal structures possessed the enrichment factor of >10 at 1% of the ranked database. ROC-AUC, AUAC, RIE, and BEDROC were calculated for these 8 crystal structures. 2WXV produced maximum BEDROC (0.768, at α=8) and RIE (11.22). 2WXV as a single initial crystal structure in the virtual screening protocol is likely to produce more accurate results than any other single crystal structure.

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Phase Behaviors of Ionic Liquids Heating from Different Crystal Polymorphs toward the Same Smectic-A Ionic Liquid Crystal by Molecular Dynamics Simulation

Crystals ◽

10.3390/cryst9010026 ◽

2019 ◽

Vol 9 (1) ◽

pp. 26 ◽

Cited By ~ 3

Author(s):

Wudi Cao ◽

Yanting Wang

Keyword(s):

Crystal Structure ◽

Experimental Data ◽

Molecular Dynamics ◽

Ionic Liquid ◽

Liquid Crystal ◽

Dynamics Simulation ◽

Smectic A ◽

Dynamics Simulations ◽

Phase Behaviors ◽

Initial Crystal

Five distinct crystal structures, based on experimental data or constructed manually, of ionic liquid [C14Mim][NO3] were heated in NPT molecular dynamics simulations under the same pressure such that they melted into the liquid crystal (LC) phase and then into the liquid phase. It was found that the more entropy-favored structure had a higher solid-LC transition temperature: Before the transition into the LC, all systems had to go through a metastable state with the side chains almost perpendicular to the polar layers. All those crystals finally melted into the same smectic-A LC structure irrelevant of the initial crystal structure.

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THE EFFECT OF THE EXTERNAL MEDIUM ON THE STRUCTURAL-PHASE TRANSFORMATIONS OF QUARTZITE UPON HIGH-ENERGY ELECTRON IRRADIATION

10.46813/2019-123-030 ◽

2019 ◽

pp. 30-34

Author(s):

E.P. Bereznyak ◽

I.V. Kolodiy ◽

Yu.S. Khodyreva

Keyword(s):

Crystal Structure ◽

Electron Irradiation ◽

Structural Phase ◽

High Energy ◽

Water Medium ◽

X Ray Diffraction ◽

Water Stream ◽

Radiation Annealing ◽

Initial Crystal ◽

Structural Phase Transformations

The structural transformations of the natural quartzite under the electron irradiation in doses range of 107…108 Gy in various medium were studied using IR-spectroscopy, X-ray diffraction, and crystal-optical analyzes. It was established that under the irradiation, both in air and in a water stream, intense crystallization of the amorphous component occurs, which is siliceous cement. The initial crystal structure of quartzite is also improved as a result of radiation annealing of defects and impurities present in the initial quartz. It was found that the water medium significantly accelerates these processes, however, in the studied doses range for both types of irradiation, degradation of the quartzite crystal structure is not observed.

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