Hydrodesulphurization of thiophene over zirconia and alumina supported Co-Mo catalysts

1989 ◽  
Vol 54 (8) ◽  
pp. 2064-2068 ◽  
Author(s):  
Jiří Sedláček ◽  
Zdeněk Vít
Keyword(s):  
Total Pressure ◽  
Supported Catalysts ◽  
Atomic Concentration ◽  
Commercial Sample ◽  
Sulphur Oxidation ◽  
Como Catalysts ◽  
Zirconia Support ◽  
Como Catalyst ◽  
Concentration Ratios

The zirconia supported CoMo catalysts and the commercial sample CoMo/Al2O3 were characterized by XPS measurements and by testing of activity in the HDS of thiophene at 280 °C and 1 MPa of total pressure. The XPS measurements revealed the better reducibility of molybdenum, higher sulphidability of cobalt and the absence of surface sulphur oxidation in the presence of zirconia support. The surface atomic concentration ratios S/Mo were 1.2 and 2.2 for zirconia and alumina supported catalysts, respectively. The activity of the zirconia supported CoMo catalyst normalized to the overal amounts of active metals was lower than that of the commercial CoMo/Al2O3 catalyst.

Atom-Probe Tomographic Analyses of Hydrogen Interstitial Atoms in Ultrahigh Purity Niobium

2015 ◽  
Vol 21 (3) ◽  
pp. 535-543 ◽  
Author(s):  
Yoon-Jun Kim ◽  
David N. Seidman
Keyword(s):  
Laser Pulse ◽  
Thermal Energy ◽  
Pulse Energy ◽  
Laser Pulse Energy ◽  
Atom Probe ◽  
Atomic Scale ◽  
Hydrogen Atoms ◽  
Atomic Concentration ◽  
Pulse Energies ◽  
Concentration Ratios

AbstractAtomic-scale characterization of hydrogen and formation of niobium hydrides, using ultraviolet (wavelength=355 nm) picosecond laser-assisted local-electrode atom-probe tomography, was performed for ultrahigh purity niobium utilizing different laser pulse energies, 10 or 50 pJ/pulse or voltage pulsing. At 50 pJ/pulse, hydrogen atoms migrate onto the 110 and 111 poles as a result of stimulated surface diffusion, whereas they are immobile for <10 pJ/pulse or for voltage pulsing. Accordingly, the highest concentrations of H and NbH were obtained at 50 pJ/pulse. This is attributed to the thermal energy of the laser pulses being transferred to pure niobium specimens. Therefore, we examined the effects of the laser pulse energy being increased systematically from 1 to 20 pJ/pulse and then decreasing it from 20 to 1 pJ/pulse. The concentrations of H, H2, and NbH and the atomic concentration ratios H2/H, NbH/Nb, and Nb3+/Nb2+ were calculated with respect to the systematically changing laser pulse energies. The atomic concentration ratios H2/H and NbH/Nb are greater when decreasing the laser pulse energy than when increasing it, because the higher residual thermal energy after decreasing the laser pulse energy increases the mobility of H atoms by supplying sufficient thermal energy to form H2 or NbH.

Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM

1993 ◽  
Vol 51 ◽  
pp. 1058-1059
Author(s):  
J. Liu ◽  
M. Pan ◽  
G. E. Spinnler
Keyword(s):  
Supported Catalysts ◽  
Imaging Techniques ◽  
Nano Particles ◽  
Metal Particles ◽  
Shape Structure ◽  
Dynamical Simulations ◽  
Small Metal Particles ◽  
Extract Information

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.

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.

Photoelectrochemical experiments under various solar light concentration ratios

1999 ◽  
Vol 09 (PR3) ◽  
pp. Pr3-301-Pr3-306
Author(s):  
O. Enea ◽  
J. Blanco ◽  
S. Malato ◽  
M. I. Maldonado
Keyword(s):  
Solar Light ◽  
Light Concentration ◽  
Concentration Ratios

Assessing the Impact of the Inlet Total Pressure Distortion on the Turbofan Thrust

2018 ◽  
pp. 19-30
Author(s):  
Yu. A. Ezrokhi ◽  
E. A. Khoreva
Keyword(s):  
Total Pressure ◽  
External Compression ◽  
Average Value ◽  
Inlet Distortion ◽  
Air Inlet ◽  
Engine Thrust ◽  
Relative Value ◽  
Main Effect ◽  
Pressure Recovery Factor ◽  
The Impact

The paper considers techniques to develop a mathematical model using a method of «parallel compressors». The model is intended to estimate the impact of the air inlet distortion on the primary parameters of the aero-engine.  The paper presents rated estimation results in the context of twin spool turbofan design for two typical cruiser modes of flight of the supersonic passenger jet. In estimation the base values σbase and the average values of the inlet ram recovery σave remained invariable. Thus, parametrical calculations were performed for each chosen relative value of the area of low-pressure region.The paper shows that an impact degree of the inlet distortion on the engine thrust for two modes under consideration is essentially different. In other words, if in the subsonic mode the impact assessment can be confined only to taking into account the influence of decreasing average values of the inlet total pressure, the use of such an assumption in the supersonic cruiser mode may result in considerable errors.With invariable values of the pressure recovery factor at the engine intake, which correspond to the speed of flight for a typical air inlet of external compression σbase, and average value σave, a parameter Δσuneven  has the main effect on the engine thrust, and degree of this effect essentially depends on a difference between σave and σbase values.

Rise of total pressure near the stagnation point on a sphere

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 576-579
Author(s):  
J. C. Williams III
Keyword(s):  
Stagnation Point ◽  
Total Pressure

METAL SUPPORTED CATALYSTS FOR NOX DECOMPOSITION

2006 ◽  
Vol 5 (1) ◽  
pp. 29-35
Author(s):  
Nechita Mircea Teodor ◽  
Apostolescu Nicolae ◽  
Apostolescu Gabriela ◽  
Adrian Cailean
Keyword(s):  
Supported Catalysts
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