Temperature-Programmed Elimination of Tritium in Coal Labeled by Tritiated Gaseous Hydrogen

Abstract

The hydrogen exchange of an Argonne Pocahontas #3 (POC) coal with tritiated gaseous hydrogen in the presence of a Pt/Al 2 O 3 catalyst was carried out using a fixed-bed reactor at a temperature range of 200-250 °C. Then, the tritiated coal sample was re-exchanged with hydrogen in a gaseous hydrogen atmosphere at different raising temperature rates. The changes in radioactivity of tritium releasing from the tritium-labeled coal sample in the temperature-programmed elimination (TPE) of tritium was monitored by a radioanalyzer in situ. The release profile of tritium was fit using three Gaussian distribution functions in TPE. On the basis of the waveform analysis, the amounts and activation energies of the hydrogen exchange for every type of exchangeable hydrogen were estimated. The values of exchange activation energies are 8.8 ( 0.5, 10.7 ( 0.5, and 16.3 ( 0.5 kcal/ mol for three types of exchangeable hydrogen, respectively. The amount of type-I hydrogen was independent of the exchange reaction temperature. In contrast to this, the amount of types II and III of exchangeable hydrogen increased with an increasing exchange temperature, suggesting that the amount of types II and III of hydrogen in the coal is dependent upon the exchange temperature.

Comprehensive Study of Isobutane Selective Oxidation Over Group I and II Phosphomolybdates: Structural and Kinetic Factors

“…Effective ionic radii data obtained from previous work by Shannon [35] unique kinetic parameters. Previous researchers have simulated temperature-programmed desorption using Gaussian curves and used these to determine thermodynamic parameters [39][40][41][42]. The mass spectral intensities in this work, I P , are a function of temperature, T. I P is simulated by the following Gaussian expression [23,43]:…”

Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

“…It is assumed that the convoluted nature of the category 2 product formation is due to the concurrent desorption of product from different distinct active sites within the phosphomolybdate, with each site exhibiting unique kinetic parameters. Previous researchers have simulated temperature-programmed desorption using Gaussian curves and used these to determine thermodynamic parameters [66][67][68][69]. The mass spectral intensities in this work, I P , are a function of temperature, T. I P is simulated by the following Gaussian expression [51,70]: …”

A Study of the Hydrogen Exchange Reactions Occurring during Loy Yang Lignite Pyrolysis Using Deuterium-Labeled Water and Gas Chromatography–Mass Spectrometry Analysis

“…The work in this area prior to 2004 has been reviewed in a detailed monograph, 5 with a more recent paper continuing the tritiated hydrogen work with a pulsed addition technique being used to monitor the uptake of the gas by the coal. 6 The effect of mineral matter on this process has also been studied, 7 while earlier research used tritiated water to study the hydrogen exchange characteristics of a coal. 8 The exchange reactions of deuterium-labeled tetralin and naphthalene with a coal have been studied using a variety of techniques, 9 while a recent study used deuterated methane to study coal pyrolysis with CO 2 reforming of methane.…”

“…Typically, isotopically labeled molecules such as water, hydrogen, or hydrogen-donor molecules have been used, with tritiated species being detected by liquid scintillation and deuterium-containing species by nuclear magnetic resonance (NMR). The work in this area prior to 2004 has been reviewed in a detailed monograph, with a more recent paper continuing the tritiated hydrogen work with a pulsed addition technique being used to monitor the uptake of the gas by the coal . The effect of mineral matter on this process has also been studied, while earlier research used tritiated water to study the hydrogen exchange characteristics of a coal .…”