ESTONIAN ACADEMY
PUBLISHERS
eesti teaduste
akadeemia kirjastus
PUBLISHED
SINCE 1984
 
Oil Shale cover
Oil Shale
ISSN 1736-7492 (Electronic)
ISSN 0208-189X (Print)
Impact Factor (2021): 1.442
A TG-FTIR INVESTIGATION AND KINETIC ANALYSIS OF OIL SHALE KEROGEN PYROLYSIS USING THE DISTRIBUTED ACTIVATION ENERGY MODEL; pp. 228–247
PDF | doi: 10.3176/oil.2016.3.03

Authors
MINGSHU CHI, XIANGCHENG XU, DA CUI, Hongxi Zhang, QING WANG
Abstract

In this paper, the Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy (TG-FTIR) technique is used to analyze the pyrolysis behavior of kerogen of two different oil shales at different heating rates. The pyro­lysis reaction mechanism of kerogen and the regularity of change in the composition of its pyrolysis products are discussed. Furthermore, the apparent activation energy (E) and the frequency factor (k0) are determined through the distributed activation energy model (DAEM), and the relation­ships between E and the kerogen chemical structure, conversion rate, frequency factor, and the amount of kerogen pyrolysis products generated are established. The results show that the kerogen structure is similar to that of aliphatic chains, its pyrolysis takes place mostly in the range of 350–520 °C, and the post-pyrolysis semicoke residue accounts for less than 32.5%. In the kerogen pyrolysis process, first the precipitation of free water takes place, followed by depolymerization and decarboxylation, so that the main alkyl side chains are constantly parting and cycling, and the oxygen-containing group gradually breaks up and produces substances such as alkanes, carboxylic acids, alcohols, and aldehydes until a more stable graphite-like structure of kerogen is formed. In the products of kerogen pyrolysis, the concentrations of released lightweight noncondensable volatiles (CH4, CO, CO2) are lower than those of liberated condensable volatiles containing macromolecules (e.g., CHx, C=O groups) that show the Gaussian-like distribution. The apparent activation energy in the two kinds of kerogen varies in the range of 100–495 kJ·mol–1. At the same time, during the entire pyrolysis system, the apparent activation energy and logarithm values of the frequency factor (lnk0) exhibit a good linear relationship. The study reveals the pyrolysis reaction mechanism of oil shale in terms of the relationship between the chemical structure of kerogen macromolecules and the degree of oil shale pyrolysis.

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