HYDROGEN CHEMISORPTION ON NICKEL–MAGNESIA CATALYSTS

1963 ◽  
Vol 41 (1) ◽  
pp. 68-73 ◽  
Author(s):  
N. Ramasubramanian ◽  
L. M. Yeddanapalli
Keyword(s):  
Kinetic Data ◽  
Pressure Range ◽  
Hydrogen Adsorption ◽  
Catalyst Surface ◽  
Hydrogen Chemisorption ◽  
Oxygen Contamination ◽  
Different Types ◽  
Elovich Equation ◽  
Temperature And Pressure ◽  
Oxygen Addition

The hydrogen adsorption activities, per gram of nickel, of two nickel–magnesia catalysts are compared and explained on the basis of different types of nickel being present. The application of the Elovich equation to interpret the kinetic data shows the possibility of the presence of three kinetic stages in the temperature and pressure range studied. A study of the effect, on the hydrogen adsorption, of deliberate oxygen addition to and re-reduction of the catalyst surface shows that the nature of the oxygen contamination in the catalyst is different from that of the added oxygen.

scholarly journals Non-Faradaic Promotion of Ethylene Hydrogenation Under Oscillating Potentials

2020 ◽  
Author(s):  
Chia Wei Lim ◽  
Max J. Huelsey ◽  
Ning Yan
Keyword(s):  
Kinetic Data ◽  
Hydrogen Adsorption ◽  
Catalyst Surface ◽  
Ethylene Hydrogenation ◽  
Promotion Effect ◽  
Ethylene Adsorption ◽  
Electric Potentials ◽  
Dynamic Enhancement ◽  
Optimized Conditions ◽  
Present Experimental Evidence

The acceleration of Faradaic reactions by oscillating electric potentials has emerged as a viable tool to enhance electrocatalysis, but the non-Faradaic dynamic promotion of thermal catalytic processes remains to be proven. Here, we present experimental evidence showing that oscillating potentials are capable of enhancing the rate of ethylene hydrogenation despite no promotion effect was observed under static potentials. The non-Faradaic dynamic enhancement reaches up to 553% on a Pd/C electrode when cycling between –0.25 VNHE and 0.55 VNHE under optimized conditions with a frequency of around 0.1 Hz and a duty cycle of 99%. Under those conditions, no stoichiometric electron transfer to ethylene can be observed, confirming the non-Faradaic nature of the process. Experiments in different electrolytes reveal a good correlation between the catalytic enhancement and the doublelayer capacitance – a measure for the interfacial electric field strength. Preliminary kinetic data suggests that cycling to a low potential increases the hydrogen adsorption on the catalyst surface while at higher potential, the ethylene adsorption and hydrogenation becomes relatively more favorable<br>

scholarly journals Non-Faradaic Promotion of Ethylene Hydrogenation Under Oscillating Potentials

2020 ◽  
Author(s):  
Chia Wei Lim ◽  
Max J. Huelsey ◽  
Ning Yan
Keyword(s):  
Kinetic Data ◽  
Hydrogen Adsorption ◽  
Catalyst Surface ◽  
Ethylene Hydrogenation ◽  
Promotion Effect ◽  
Ethylene Adsorption ◽  
Electric Potentials ◽  
Dynamic Enhancement ◽  
Optimized Conditions ◽  
Present Experimental Evidence

The acceleration of Faradaic reactions by oscillating electric potentials has emerged as a viable tool to enhance electrocatalysis, but the non-Faradaic dynamic promotion of thermal catalytic processes remains to be proven. Here, we present experimental evidence showing that oscillating potentials are capable of enhancing the rate of ethylene hydrogenation despite no promotion effect was observed under static potentials. The non-Faradaic dynamic enhancement reaches up to 553% on a Pd/C electrode when cycling between –0.25 VNHE and 0.55 VNHE under optimized conditions with a frequency of around 0.1 Hz and a duty cycle of 99%. Under those conditions, no stoichiometric electron transfer to ethylene can be observed, confirming the non-Faradaic nature of the process. Experiments in different electrolytes reveal a good correlation between the catalytic enhancement and the doublelayer capacitance – a measure for the interfacial electric field strength. Preliminary kinetic data suggests that cycling to a low potential increases the hydrogen adsorption on the catalyst surface while at higher potential, the ethylene adsorption and hydrogenation becomes relatively more favorable<br>

Competing Channels in the Propene + OH Reaction: Experiment and Validated Modeling over a Broad Temperature and Pressure Range

2011 ◽  
Vol 225 (11-12) ◽  
pp. 1271-1291 ◽  
Author(s):  
Claudia Kappler ◽  
Judit Zádor ◽  
Oliver Welz ◽  
Ravi X. Fernandez ◽  
Matthias Olzmann ◽  
...  
Keyword(s):  
Pressure Range ◽  
Temperature And Pressure

Surface Properties and Gas Adsorption

2003 ◽  
Author(s):  
Toshiaki Enoki ◽  
Morinobu Endo ◽  
Masatsugu Suzuki
Keyword(s):  
Alkali Metal ◽  
Activated Charcoal ◽  
Low Temperatures ◽  
Gas Adsorption ◽  
Hydrogen Adsorption ◽  
Hydrogen Chemisorption ◽  
Guest Molecules ◽  
Hydrogen Molecules ◽  
General Aspects ◽  
Stage 1

It is well known that alkali metal binary GICs adsorb gaseous species (H2, N2, Ar, CH4, etc.) physisorptively at low temperatures, where physisorbed gaseous molecules are accommodated in the interstitials of the alkali metal lattice within the graphitic galleries (Lagrange and Hérold, 1975; Lagrange et al., 1972, 1976; Watanabe et al., 1971, 1972, 1973). The capacity for hydrogen adsorption, which is estimated at 144 cm3/g in KC24, for example, is large and comparable to the capacity in other adsorbers such as zeolite or activated charcoal. Interestingly, the physisorption phenomenon in alkali metal GICs has different features from that in conventional adsorbents such as zeolite or activated charcoal; that is, guest molecules in alkali metal GICs are not simply bonded to the adsorbents through weak van der Waals forces without any change in the electronic structures. Here we discuss the gas physisorption phenomenon in alkali metal GICs from general aspects, in relation to their specific features. Then in subsequent sections, we will give details of actual cases. Hydrogen is a typical gaseous molecule adsorbed in alkali metal GICs. Hydrogen physisorption takes place at low temperatures below about 200 K, where hydrogen molecules are accommodated in the graphitic galleries and are not dissociated into atomic hydrogen species. When the temperature is increased to over 200 K, the alkali metal GICs work as catalysts to hydrogen, resulting in the occurrence of hydrogen chemisorption. Hydrogen physisorption will be discussed in Section 8.1.2, hydrogen chemisorption and related issues have been discussed partly in Sections 2.2.1 and 5.4.1 from the viewpoints of structure and electronic properties, and will be discussed again in Section 8.1.2. Figure 8.1 represents the composition dependence of the amount of physisorption of hydrogen molecules in KCm at 77 K (Lagrange and Hérold, 1975). The composition of 1/m = 1/8 corresponds to the stage-1 compound and the composition 1/m = 1/24 to the stage-2 compound; intermediate compositions between 1/8 and 1/24 are considered to have a mixed structure of stage-1 and stage-2 compounds. The stage-1 compound does not adsorb hydrogen at all.

scholarly journals Effect of Size on Hydrogen Adsorption on the Surface of Deposited Gold Nanoparticles

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 344 ◽  
Author(s):  
Andrey Gatin ◽  
Maxim Grishin ◽  
Nadezhda Dokhlikova ◽  
Sergey Ozerin ◽  
Sergey Sarvadii ◽  
...  
Keyword(s):  
Experimental Study ◽  
Gold Nanoparticles ◽  
Scanning Tunneling Microscopy ◽  
Molecular Hydrogen ◽  
Hydrogen Adsorption ◽  
Pyrolytic Graphite ◽  
Scanning Tunneling ◽  
Hydrogen Chemisorption ◽  
Tunneling Microscopy ◽  
Average Size

An experimental study of molecular hydrogen adsorption on single gold nanoparticles of various sizes deposited on the surface of highly oriented pyrolytic graphite (HOPG) was carried out by means of scanning tunneling microscopy and spectroscopy. The effect of size on the HOPG/Au system was established. Hydrogen was dissociatively chemisorbed on the surface of gold nanoparticles with an average size of 5–6 nanometers. An increase in the size of nanoparticles to 10 nm or more led to hydrogen chemisorption being inhibited and unable to be detected.

Equilibrium model for the interpretation of the conduction properties of metal–ammonia solutions

1977 ◽  
Vol 55 (11) ◽  
pp. 2211-2216 ◽  
Author(s):  
S. Hahne ◽  
P. Krebs ◽  
U. Schindewolf
Keyword(s):  
Electrical Conductivity ◽  
Pressure Range ◽  
High Mobility ◽  
Solvation Number ◽  
Free Electrons ◽  
Solvated Electrons ◽  
Entire Concentration Range ◽  
Pressure Coefficients ◽  
Temperature And Pressure ◽  
Conduction Properties

The electrical conductivity of metal–ammonia solutions can be described by an equilibrium of solvated electrons of low mobility and of free electrons of high mobility. With proper choice of the equilibrium constant and its temperature and pressure dependence and of the solvation number of the solvated species the experimental conductivities can be matched in the temperature and pressure range from 240 to 420 K and up to 1000 bar over the entire concentration range from 0.1 mol/ℓ to saturation, also fitting the extrema of the temperature and pressure coefficients of the conductivity around 1 mol/ℓ.

scholarly journals Thermodynamic modeling of solid solubility in supercritical carbon dioxide: Comparison between mixing rules

2013 ◽  
Vol 19 (3) ◽  
pp. 389-398 ◽  
Author(s):  
Hadi Baseri ◽  
Ali Haghighi-Asl ◽  
Nader Lotfollahi
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Thermodynamic Modeling ◽  
Pressure Range ◽  
The Other ◽  
Mixing Rules ◽  
Calculation Results ◽  
Temperature And Pressure ◽  
Robinson Equation ◽  
Supercritical Carbon

In this paper, Peng Robinson equation of state is used for thermodynamic modeling of the solubility of various solid components in the supercritical carbon dioxide. Moreover, the effects of three mixing rules of Van der Waals mixing rules, Panagiotopoulos and Reid mixing rules and modified Kwak and Mansoori mixing rules on the accuracy of calculation results were studied. Good correlations between calculated and experimental data were obtained in the wide temperature and pressure range. A comparison between used models shows that modified Kwak and Mansoori mixing rules give better correlations in comparison with the other mixing rules.

The reactions of O(3P) with the butanols

1983 ◽  
Vol 61 (12) ◽  
pp. 2716-2720 ◽  
Author(s):  
John M. Roscoe
Keyword(s):  
Free Energy ◽  
Gas Phase ◽  
Rate Constants ◽  
Substrate Concentration ◽  
Kinetic Data ◽  
Absolute Rate ◽  
Gas Phase Reactions ◽  
Linear Free Energy ◽  
Different Types ◽  
Energy Relations

The reactions of O(3P) with the butanols were studied kinetically as a function of temperature and substrate concentration. The absolute rate constants for the gas phase reactions, in the units M−1 s−1, obey the following relations.[Formula: see text]The results suggest that although the α-CH bond in these alcohols is the most reactive one, reaction of O(3P) with other CH bonds in the alcohols is also appreciable. The kinetic data for these and other alcohols are separated into contributions from the different types of CH bonds and the results are discussed in terms of linear free energy relations.

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