scholarly journals Modeling phase formation on catalyst surfaces: Coke formation and suppression in hydrocarbon environments

AIChE Journal ◽  
2021 ◽  
Author(s):  
Peng Wang ◽  
Thomas P. Senftle
Keyword(s):  
Phase Formation ◽  
Coke Formation ◽  
Catalyst Surfaces

scholarly journals Modeling phase formation on catalyst surfaces: Coke formation and suppression in hydrocarbon environments

2021 ◽  
Author(s):  
Peng Wang ◽  
Thomas Senftle
Keyword(s):  
Density Functional ◽  
Coke Formation ◽  
Al Alloys ◽  
Grand Canonical Monte Carlo ◽  
Functional Theory ◽  
Carbon Networks ◽  
Adsorbed Carbon ◽  
Fe Sites ◽  
Grand Canonical ◽  
Catalyst Surfaces

We develop a simulation toolset employing density functional theory (DFT) in conjunction with grand canonical Monte Carlo (GCMC) to study coke formation on Fe-based catalysts during propane dehydrogenation (PDH). As expected, pure Fe surfaces develop stable graphitic coke structures and rapidly deactivate. We find that coke formation is markedly less favorable on FeC and FeS surfaces. Fe-Al alloys display varying degrees of coke resistance, depending on their composition, suggesting that they can be optimized for coke resistance under PDH conditions. Electronic structure analyses show that both electron-withdrawing effects (on FeC and FeS) and electron-donating effects (on Fe-Al alloys) destabilize adsorbed carbon. On the alloy surfaces, a geometric effect also isolates Fe sites and disrupts the formation of graphitic carbon networks. This work demonstrates the utility of GCMC for studying the formation of disordered phases on catalyst surfaces and provides insights for improving the coke resistance of Fe-based PDH catalysts.

Characterization of reactive phase formation in sputter-deposited Ni/Al multilayer thin films using TEM

1996 ◽  
Vol 54 ◽  
pp. 1000-1001
Author(s):  
G. Lucadamo ◽  
K. Barmak ◽  
C. Michaelsen
Keyword(s):  
Thin Films ◽  
Phase Formation ◽  
Dark Field ◽  
Nickel Layer ◽  
Multilayer Thin Films ◽  
Cross Sectional ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Sputter Deposited ◽  
Constant Heating

The subject of reactive phase formation in multilayer thin films of varying periodicity has stimulated much research over the past few years. Recent studies have sought to understand the reactions that occur during the annealing of Ni/Al multilayers. Dark field imaging from transmission electron microscopy (TEM) studies in conjunction with in situ x-ray diffraction measurements, and calorimetry experiments (isothermal and constant heating rate), have yielded new insights into the sequence of phases that occur during annealing and the evolution of their microstructure.In this paper we report on reactive phase formation in sputter-deposited lNi:3Al multilayer thin films with a periodicity A (the combined thickness of an aluminum and nickel layer) from 2.5 to 320 nm. A cross-sectional TEM micrograph of an as-deposited film with a periodicity of 10 nm is shown in figure 1. This image shows diffraction contrast from the Ni grains and occasionally from the Al grains in their respective layers.

An analytical microscopic study of metals in fluidized catalytic cracking catalyst

1986 ◽  
Vol 44 ◽  
pp. 854-855
Author(s):  
Clifford S. Rainey
Keyword(s):  
Electron Microscopy ◽  
Spatial Distribution ◽  
Catalytic Cracking ◽  
Catalyst Deactivation ◽  
Coke Formation ◽  
Acid Sites ◽  
Y Zeolite ◽  
Fcc Catalyst ◽  
Fluidized Catalytic Cracking ◽  
High Regeneration

The spatial distribution of V and Ni deposited within fluidized catalytic cracking (FCC) catalyst is studied because these metals contribute to catalyst deactivation. Y zeolite in FCC microspheres are high SiO2 aluminosilicates with molecular-sized channels that contain a mixture of lanthanoids. They must withstand high regeneration temperatures and retain acid sites needed for cracking of hydrocarbons, a process essential for efficient gasoline production. Zeolite in combination with V to form vanadates, or less diffusion in the channels due to coke formation, may deactivate catalyst. Other factors such as metal "skins", microsphere sintering, and attrition may also be involved. SEM of FCC fracture surfaces, AEM of Y zeolite, and electron microscopy of this work are developed to better understand and minimize catalyst deactivation.

Elemental Distribution in Pt-Re:Al2O3 Naphtha Reforming Catalysts

1980 ◽  
Vol 38 ◽  
pp. 200-201
Author(s):  
R. L. Freed ◽  
M. J. Kelley
Keyword(s):  
Bimetallic Catalyst ◽  
Supported Catalysts ◽  
Coke Formation ◽  
Materials Characterization ◽  
Metal Catalyst ◽  
Elemental Distribution ◽  
Exact Nature ◽  
Naphtha Reforming ◽  
Reforming Catalysts ◽  
Commercial Introduction

The commercial introduction of Pt-Re supported catalysts to replace Pt alone on Al2O3 has brought improvements to naphtha reforming. The bimetallic catalyst can be operated continuously under conditions which lead to deactivation of the single metal catalyst by coke formation. Much disagreement still exists as to the exact nature of the bimetallic catalyst at a microscopic level and how it functions in the process so successfully. The overall purpose of this study was to develop the materials characterization tools necessary to study supported catalysts. Specifically with the Pt-Re:Al2O3 catalyst, we sought to elucidate the elemental distribution on the catalyst.

Coke formation on HFAU and HEMT zeolites. Influence of the reaction temperature and propene pressure

1999 ◽  
Vol 96 (2) ◽  
pp. 303-318 ◽  
Author(s):  
G. A. Doka Nassionou ◽  
P. Magnoux ◽  
M. Guisnet
Keyword(s):  
Reaction Temperature ◽  
Coke Formation

On the trustability of semi-empirical methods to the calculation of gas phase formation enthalpies of inorganic compounds containing heavy metals: tin borates

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Heavy Metals ◽  
Gas Phase ◽  
Phase Formation ◽  
Inorganic Compounds ◽  
Formation Enthalpy ◽  
Computational Time ◽  
Gas Formation ◽  
Formation Enthalpies ◽  
Knudsen Effusion Mass Spectrometry ◽  
Semi Empirical

<p>In the present work, are calculated the gas formation enthalpies (SE; PM3 and PM6) for tin borates: SnB<sub>2</sub>O<sub>4</sub><sup> </sup>and Sn<sub>2</sub>B<sub>2</sub>O<sub>5</sub>. The calculated values are compared with experimental ones, obtained by Knudsen effusion mass spectrometry [3]. It is shown that SE methods, besides their lower computational time consuming can, indeed, provide reliable gas phase formation enthalpy values for inorganic compounds containing heavy metals.</p>

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