Authors:D. Skala, S. Korica, D. Vitorović, and H. Neumann
The rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using DSC
analysis. Recently performed thermogravimetric studies (TG and DTG) with the same samples of KC indicated that the activation
energy of the pyrolysis of specific KCs increases with increasing paraffinic structure in the KC. An opposite effect, i.e.
a decrease of the activation energy with an increase of paraffinic structure was determined in the case of KC oxidation. In
this study, using the standard ASTM E-698 method based on the determined temperature at which the maximum heat effect could
be observed (exo in the case of oxidation and endo in the case of pyrolysis), an activation energy for the pyrolysis, as well
as for the oxidation process was determined and also successfully correlated with the content of paraffinic structure of KC.
Thus, the higher content of paraffinic structure in KCs indicates that higher values of the activation energy could be determined
either in the case of pyrolysis or oxidation followed by DSC analysis.
Authors:S. Cebulak, A. Karczewska, A. Mazurek, and A. Langier-Kużniarowa
The study presents examples of the application of oxyreactive thermal analysis to the geological prospecting of bitumen deposits. Thermal analysis performed under properly chosen analytical conditions allows determination of characteristic features of organic matter and, at the same time, estimation of the thermal history of rocks. Thermal oxyreactivity curves document whether rocks were heated before or not. The results of the oxyreactive thermal analysis correlate well with the results of routine chemical analyses of organic matter (e.g. the composition of kerogen and bituminous fraction, Rock-Eval analysis and others). Our study clearly demonstrates that the composition of organic matter in facially, lithostratigraphically, and biogenetically identical rocks depends on their thermal history.
Authors:S. Cebulak, A. Langier-Kuüniarowa, and I. Grotek
Oxyreactive thermal analysis (OTA) carried out in the conditions of full access of oxygen to each reacting particle of the sample investigated is a suitable method for the determination of important properties of the organic matter dispersed in the rocks. Its results may be easily evaluated to the form of values to be used in a clear diversification and classification system of organic matter/kerogen, as well as to the evaluation of its transformation process in a rockmass. The OTA also enables the distinguishing of the transformation stages and the investigation of the results of the gaseous products liberation from organic matter and kerogen. The OTA method may be applied as a complementary one for the Rock Eval analysis and be used for the organic geochemical and bituminological studies for geological bitumen prospecting.
from kerogen extracted from two Moroccan oil shales (from Timahdit and Tarfaya)
were oxidized in air. The oxidations were studied by isothermal thermogravimetry.
Several kinetic models for mechanisms of the reactions were tested to fit
the experimental data. Oxidation of the residual carbon derived from Timahdit
oil shale followed a two-third order reaction with an activation energy of
58.5 kJ mol–1, whilst that from Tarfaya oil
shale was a half order reaction with activation energy of 64.1 kJ mol–1.
The gasification with carbon dioxide of residual carbons prepared from Timahdit and Tarfaya oil shale kerogens has been studied
by thermal analysis techniques (TG and DTA) under heating rates varying from 5 to 48C min-1. The reactions obey first order kinetics. Activation energies have been calculated by several methods, such as Kissinger,
Chen-Nuttall and Coats-Redfern methods, and are broadly comparable with literature data for similar carbons.
Authors:S. Cebulak, A. Gawęda, and A. Langier-Kużniarowa
This paper presents the results of oxyreactive thermal analyses of organic matter in rocks, heated naturally during diagenetic
to metamorphic processes. During the experiments we traced the reactions in the temperature range up to 900C, it means from
the very beginning of diagenetic transformations to the highest real temperatures acting in the Earth's crust as a solid phase.
The results showed that TA could be a tool for the reconstruction of thermal regime in natural coal-bearing systems.
Authors:István Vető, Katalin Báldi, Stjepan Ćorić, Magdolna Hetényi, Attila Demény, and István Futó
foraminifera. Organic carbon isotopic composition (δ 13 C org ) and Rock-Eval indices are used as proxies to estimate the relative contribution of planktonic, benthic, and land plant components to kerogen.
Authors:D. Skala, S. Korica, D. Vitorovic, and H. J. Neumann
In this study, the rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using TG/DTG technique. The rate of pyrolysis after preoxidation step performed at low temperature (below 230°C), was also studied. The determined pyrolysis activation energy increases with increasing paraffinic structure in the KC: an opposite effect was determined in the case of oxidation. Comparison of the reaction rate constants of the pyrolysis as well as the oxidation of untreated and pre-oxidized KC samples indicated the basis of the proposed thermal method for kerogen type determination.
Kerogen separates which consist predominantly of single maceral types at maturity levels lower than 0.7% vitrinite reflectance
(R0) were pyrolysed in a single step and stepwise between 50 and 600°C. The total hydrocarbon yield and the yield of hydrocarbon
gases (C1−C4) were determined along with the detailed composition of the gaseous fraction (C1−C4 alkanes and alkenes) and the C5+-fraction. The distribution of hydrocarbons, particularly in the C1−C3 range and the alkene/alkane ratio are useful as specific indicators for the various maceral types. The residue was analysed
by reflected white light and fluorescence microscopy. The different types of reactive macerals i.e. algae, altered algae,
particulate liptinites, amorphous liptinites and amorphous humic matter are transformed into particular types of inertinite.
The reconstruction of the original maceral composition from its residue after katagenesis in a natural assemblage seems however
difficult, due to the small amount of residue of the reactive macerals and the presence of original inertinite. Qualitative
and quantitative data derived from these pyrolysis experiments may be useful on a comparative basis for the prediction of
hydrocarbon generation by these maceral groups during katagenesis.