Study of the Oxidation of Oil Shale and Kerogen by Fourier Transform Infrared Emission Spectroscopy

Abstract

Infrared emission spectroscopy has been used to monitor the chemical modifications taking place during the oxidation of bitumen-free Kerosene Creek shale, the bitumen-carbonate-free shale, and the bitumen-carbonate-silicate-free shale (kerogen). The samples were heated, in air, at temperatures in the range 50-700 °C at intervals of 50 °C. Oxidation of the samples at increasing temperatures showed a steady decrease in the signals due to aliphatic hydrocarbons (3000 cm -1 to 2700, 1460, and 1375 cm -1 ) as well as in the carbonyl/carboxyl signals (∼1710 cm -1 ) and the carbonyl signal at 1740 cm -1 , along with an increase in the anhydride signals at 1775 cm -1 and at ∼1850 cm -1 . Constant temperature (300 °C) oxidation produced a steady increase in the anhydride peaks at ∼1775 cm -1 and at ∼1850 cm -1 while the 1710 and 1740 cm -1 peaks slowly decreased. Of the mineral bands, those characteristic of carbonates totally disappeared at 700 °C while the other bands remained. The rate of decomposition of organic functionalities is generally fastest for the bitumen-carbonate-free sample. Analysis of the kinetic data clearly showed that the presence of carbonates and silicates lowered the activation energy for the oxidation of aliphatic C-H groups.

Kerogen Chemistry 4. Thermal Decarboxylation of Kerogens

“…Low-temperature thermal formation of anhydrides in Zap North Dakota lignite and in Nagoorin kerogen was observed using hot stage FTIR microscopy . Anhydrides were also reported in a paper that used IR emission from kerogens during oxidation to follow the oxidation .…”

Analysis on the Governing Reactions in Coal Oxidation at Temperatures up to 400°C

“…The major absorption peaks and their corresponding species (organic functional groups) were identified and labeled. The observed species usually contain O-H, C-H, C=C, C-O, and C=O bonds [15] [16]. Changes in the functional groups on the sample surfaces were further examined by subtracting FTIR spectra collected at various temperatures (Figure 4).…”

“…Similar to curve b in Figure 4, the negative bands assigned to νC-H (3100 cm , corresponding to aldehydes and carboxylic acids. At higher temperatures, more anhydrides and esters are formed as a result of the oxidation of alkyls and the decomposition (or condensation) reactions of carboxylic acids [15] [17]. In addition, the decomposition and condensation reactions among the existing complexes containing C=O bonds may cause a loss of certain C=O bonds [4] [18].…”

Binding of heavy metals by oxidised kerogen in (palaeo)weathered black shales

“…This pattern has been observed elsewhere and interpreted as the activity of iron-and sulphide-oxidising bacteria present in the deepest, oxygen-deficient portions of the weathering profile (Petsch et al, 2005). Opposite to sulphides, kerogen requires a high level of oxygen activity and either long exposure or high temperature to trigger oxidation ( 1999; Rose et al, 1998). As sulphide oxidation in the studied section preceded the formation of oxygen functional groups in kerogen at the progressing weathering front (as measured by the S3 parameter on Fig.…”