X-Ray Photoelectron Spectroscopy Investigation of Nitrogen Transformation in Chinese Oil Shales During Pyrolysis

Abstract

X-ray photoelectron spectroscopy (XPS) was used to investigate changes in nitrogen functionalities present in Chinese Huadian (HD), Maoming (MM) and Yaojie (YJ) oil shales during pyrolysis. Throughout the process (T ≤ 600 °C), most of the nitrogen contained in raw oil shale samples was retained in their semi-cokes. Five peaks of nitrogen functionalities (N 1s) appeared in the XPS spectra of raw HD, MM and YJ oil shale samples and their semi-cokes: N-6 (pyridine), N-A (amino), N-5 (pyridone), N-Q (quaternary nitrogen) and N-X1 (pyridine N-oxide). To obtain an acceptable fit, an additional peak at 404 (±0.5) eV (N-X2) was required in the N 1s spectra of the samples. N-5 could either represent pyridone or a mixture of pyridone and pyrrolic nitrogen forms, the most abundant ones in all samples. At a relatively low temperature (300 °C) the desorption reaction occurred and the amount of chemisorbed oxygen associated nitrogen (N-X2) decreased significantly. As the pyrolysis temperature increased from 300 to 500 °C, pyridine N-oxide was converted to pyridone, and, simultaneously, the latter was converted to pyridine and pyridine structures associated with oxygenquaternary nitrogen. In the semi-cokes of Huadian and Maoming oil shale samples at 600 °C, most of the pyridone was converted into pyridine and quaternary nitrogen. At this temperature, especially the condensation reaction of pyridine into quaternary nitrogen occurred in the semi-coke of Yaojie oil shale sample, while quaternary nitrogen represented the nitrogen atoms in the interior of precursors of the graphene layers.

A carbon dot‐based time‐dependent color‐changing room temperature phosphorescent material with facile synthesis

“…This is because a lot of O‐C=O is converted to C=O by fracture in the heat‐induced engineering, while at the same time, a large number of C‐O fractures have also occurred. Figure 5c,g shows the high‐resolution XPS maps of the N1s of both, which can be divided into two peaks around 398.18 and 399.92 eV by deconvolution, which correspond to the C‐N=C and C‐NH 2 [38, 39]. By comparison, it can be found that the peak intensities corresponding to C‐N=C of N‐CDs@CA 240°C decreased dramatically compared with those of N‐CDs@CA 200°C.…”

“…A comparison shows that the peak ratios corresponding to O-C=O and C=O for N-CDs@CA 240 C are greatly reduced compared with those for N-CDs@CA 200 C. This is because a lot of O-C=O is converted to C=O by fracture in the heat-induced engineering, while at the same time, a large number of C-O fractures have also occurred. Figure 5c,g shows the high-resolution XPS maps of the N1s of both, which can be divided into two peaks around 398.18 and 399.92 eV by deconvolution, which correspond to the C-N=C and C-NH 2 [38,39]. By comparison, it can be found that the peak intensities corresponding to C-N=C of N-CDs@CA 240 C decreased dramatically compared with those of N-CDs@CA 200 C. Further integral calculations were performed to compare the C-N=C and C-NH 2 peaks of the two, respectively.…”

A Review on the Application of Microwave Absorbents in Oil Shale

“…Crude oil production recovered to 11.3 million barrels/day and to about 85% of pre-epidemic levels. 106 Therefore, how to reduce the production cost of shale oil will become a key issue in the future. In view of this problem, we summarize it into two aspects.…”