Formation mechanism of solid product produced from co-pyrolysis of Pingdingshan lean coal with organic matter in Huadian oil shale

Abstract

A mixture of Pingdingshan lean coal and acid-treated Huadian oil shale was co-pyrolyzed in a drop-tube fixed-bed reactor in the temperature range of 300 °C–450 °C. To reveal the formation mechanism of the solid co-pyrolysis product, changes in some physicochemical properties were investigated, using analysis by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, pore analysis, thermogravimetry, and electron spin resonance. X-ray diffraction showed that the lattice plane spacing for the co-pyrolyzed mixture decreased from 0.357 nm to 0.346 nm and the average stacking height increased from 1.509 nm to 1.980 nm in the temperature range of 300 °C–450 °C, suggesting that pyrolysis treatment increased its degree of metamorphism. The amount of oxygen-containing functional groups and pore volume decreased with increasing temperature. Thermogravimetry and electron spin resonance results showed that synergistic effects occurred during the co-pyrolysis process. A formation mechanism for the solid product was proposed. Hydrogen-rich radicals generated from the pyrolysis of the oil shale were trapped by hydrogen-poor macromolecular radicals of the intermediate metaplast produced from coal pyrolysis, thereby increasing the yield of solid product.

Graphical abstract

Keywords

co-pyrolysis / coal / oil shale / electron spin resonance / mechanism

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Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant No. 21776002), the Natural Science Foundation of Anhui Provincial Education Department (Grant Nos. KJ2016A097, KJ2017A056, and KJ2019A0076), the Innovation Project of Overseas People of Anhui Province, the Science and Technology Major Projects of Anhui Province (Grant Nos. 17030901086), and the Natural Science Foundation of Anhui Province (Grant Nos. 1708085QB33 and 2008085QB87).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-020-1944-7 and is accessible for authorized users.

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