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Showing 1 to 20 of 21 for “"Structure sensitivity"”.
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Structure Sensitivity of Ethylene Adsorption on Platinum (Dehydrogenation)
… work is conducted to investigate the structure sensitivity of ethylene adsorption on platinum surfaces. Temperature Programmed Desorption (TPD), Electron Energy Loss Spectroscopy (EELS), Low-Energy Electron Diffraction (LEED) and Auger spectroscopy are applied to study the adsorption …
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Structure Sensitivity of Alkane Hydrogenolysis on Ir/MgAl₂O₄ Catalysts
… of the metals, and this phenomena is called structure sensitivity. Generally, the structure sensitivity effect is considered being led by a combination of geometric property change and electronic property change of the surface metals. The particle size variation is an effective way to change …
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Structure sensitivity of H2/D2 Isotopic Exchange on Pt/Al2O3 catalysts
Pt-supported catalysts are widely used industrially for hydrogenation reactions. However, the kinetics of hydrogen activation, a critical step for any hydrogenation reaction, is still not well understood on supported Pt surfaces. Recent studies had shown that activity and selectivity vary with Pt …
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Structure Sensitivity of Alkanes Hydrogenolysis and Alkynes Hydrogenation on Supported Ir Catalysts
… catalysts would be affected by the metal surface structure, and this phenomenon is called structure sensitivity. Generally, structure sensitivity is led by the change of geometric and electronic properties of the metal on the surface. The variation of metal nuclearity and metal-support …
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Structure Sensitivity in the Subnanometer Regime on Pt and Pd Supported Catalysts
… techniques including x-ray absorption fine structure (XAFS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS), diffuse reflectance infrared spectroscopy (DRIFTS), calorimetry and high-resolution scanning transmission electron microscopy (STEM) to investigate the structure of …
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Ethanol and Fluorinated Ethanol Decomposition on Single Crystal Platinum Surfaces: Structure Sensitivity and Electronic Effects
To study the surface work function effect on the surface reaction mechanism, ethanol and fluorinated ethanol decomposition have also been studied on clean and oxygen precovered (2 x 1)Pt(110) surface. The reaction mechanism is very similar on clean (2 x 1)Pt(110) as on Pt(331), except the ethanol …
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Structure-Sensitivity of CO Oxidation Over Supported Pt Catalysts in the Subnanometer Regime and Its Origin
Metal-oxide-supported Pt-group metal catalysts are regularly used in many industrially relevant reactions, including CO oxidation for automotive emission control. Being able to activate O2, these catalysts are also promising candidates for oxidative decomposition of chemical warfare agents and …
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Geometric and Electronic Structure Sensitivity of Methyl and Methylene Reactions on α-Cr₂O₃ and α-Fe₂O₃ surfaces
… (CH₂=CH₂). The different surface geometric structures of α-Cr₂O₃(101̅2) and (0001) lead to an increase in the activation barrier for methylene surface migration, a critical step in the coupling reaction, of 5.9 kcal/mol over the (0001) surface. For methyl dehydrogenation, differences in the …
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The partial oxidation of propene to acrolein over single-crystal Cu₂O
… during propene oxidation is reversible. The structure sensitivity of the propene oxidation reaction is demonstrated by the lack of acrolein production from the Cu-terminated, Cu₂0(100) surface following 1 atm. propene exposures. The origin of the structure sensitivity is related to the …
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SYNTHESIS, CHARACTERIZATION, AND KINETIC EVALUATION OF PLANAR AND SUPPORTED HETEROGENEOUS CATALYSTS
… material deposition technique, 2-the study of structure sensitivity for formic acid decomposition on planar Pt catalysts, and 3-characterization of bimetallic Pt-M (M = Re, Mo) catalysts using surface sensitive techniques and theory.
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The Effects of Graphic Organizers and Content Familiarity on Second Graders' Comprehension of Cause/Effect Text
… this genre. While it has been found that text structure-based graphic organizers (GOs) may assist older students in comprehending expository text, it is uncertain whether this type of scaffold is effective for primary-grade students. The aim of this study was to investigate the effects of …
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Effect of Pt Particle Size and Electronic Properties on the Hydrogenation of Ethylene
… This reaction was historically regarded as structure-insensitive, until recent studies revealed that minor variations in the metal cluster size can affect both the geometric and electronic properties, which in turn affects the catalytic activity. Platinum (Pt) based catalysts on reducible …
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Finite element modeling of contaminant transport through confined disposal facilities
… from the dredge material contained within this structure. Sensitivity analyses were also performed to evaluate the effect of soil properties, boundary conditions, etc. on contaminant transport through CDFs. The results indicated that some soil properties such as unit weight, molecular diffusion, …
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Management of Complex Sociotechnical Systems
… the influence of contextual factors and their sensitivity to sample size. The results are organized in a structured taxonomy of their fundamental assumptions, limitations, mathematical structure, sensitivity to sample size, and their practical usefulness. To summarize, this dissertation …
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Novel, High Activity Hydroprocessing Catalysts: Iron Group Phosphides
… to be 18 wt.%. Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES) measurements were employed to determine the structures of the supported samples. The main phase before and after reaction was found to be Ni₂P, but some sulfur was found to be …
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Reconstruction of Rhodium Clusters During CO Oxidation and Consequences on The Reaction Mechanism
… and isolated (single) atoms. Understanding structure sensitivity and identifying the active site or sites are crucially essential for designing efficient catalysts. To determine the active sites of a catalyst for a particular chemical reaction, in-situ/operando spectroscopy, such as diffuse …
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Development of sustainable Pd-based catalysts for removal of persistent contaminants from drinking water
… neither sensitive to Pd location on CNFs nor Pd structure. However selectivity to dinitrogen is more favorable on larger Pd nanoparticles. Therefore, an optimum Pd nanoparticle size on CNFs balances high reduction kinetics and selectivity to dinitrogen. CNF Pd catalysts perform better than …
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Preparation, Characterization and Evaluation of Bimetallic Catalysts Prepared by Electroless Deposition Methods
… Au on Pd surface was kinetically evaluated for structure insensitive propylene hydrogenation probe reaction. As the fractional coverage of Au on Pd (θ<sub>Au</sub> ≥ 0.60) increases, the Pd activity i.e., turnover frequency was increased 10-15 times showing structure sensitivity. The enhanced …
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Catalysis over molybdenum containing nitride materials
… effect on the reaction and the influence of structure sensitivity is thought to be limited in this case. What was apparent, was that the highly specific temperature programmed reaction synthesis required to prepare γMo2Nproduced an ammonia synthesis catalyst with no catalytic advantage over …
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Effects of Crystallite size and water partial pressure on the activity and selectivity of low temperature iron-based fischer-tropsch catalysts
… overall activities. However the subject of size sensitivity remains an issue as research has shown that nano-meter sized crystallites below a certain point (ie. 6 nm) can behave differently to larger crystallites in terms of activity and selectivity in Fischer-Tropsch synthesis. It has been …
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