Regulation of radicals by hydrogen-donor solvent in direct coal liquefaction

doi:10.1007/s11705-022-2186-7

Front. Chem. Sci. Eng.

2022, Vol. 16

Issue (12) : 1689-1699 https://doi.org/10.1007/s11705-022-2186-7

RESEARCH ARTICLE

Regulation of radicals by hydrogen-donor solvent in direct coal liquefaction

Wang Li, Wen-Ying Li(

), Xing-Bao Wang, Jie Feng

State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology, Taiyuan 030024, China

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Abstract

Radicals are important intermediates in direct coal liquefaction. Certain radicals can cause the cleavage of chemical bonds. At high temperatures, radical fragments can be produced by the splitting of large organic molecules, which can break strong chemical bonds through the induction pyrolysis of radicals. The reaction between the formation and annihilation of coal radical fragments and the effect of hydrogen-donor solvents on the radical fragments are discussed in lignite hydrogenolysis. Using the hydroxyl and ether bonds as indicators, the effects of different radicals on the cleavage of chemical bond were investigated employing density functional theory calculations and lignite hydrogenolysis experiments. Results showed that the adjustment of the coal radical fragments could be made by the addition of hydrogen-donor solvents. Results showed that the transition from coal radical fragment to H radical leads to the variation of product distribution. The synergistic mechanism of hydrogen supply and hydrogenolysis of hydrogen-donor solvent was proposed.

Keywords direct coal liquefaction hydrogen-donor solvent induced pyrolysis radical mechanism density functional theory calculations

Corresponding Author(s): Wen-Ying Li

Online First Date: 06 September 2022 Issue Date: 19 December 2022

Cite this article:

Wang Li,Wen-Ying Li,Xing-Bao Wang, et al. Regulation of radicals by hydrogen-donor solvent in direct coal liquefaction[J]. Front. Chem. Sci. Eng., 2022, 16(12): 1689-1699.

URL:

https://academic.hep.com.cn/fcse/EN/10.1007/s11705-022-2186-7
https://academic.hep.com.cn/fcse/EN/Y2022/V16/I12/1689

Tab.1 Proximate and ultimate analysis of lignite (wt %) [30]

Fig.1 Tetralin radical dehydrogenation (BDE, kJ?mol^?1).

Fig.2 Benzyl radical induced-pyrolysis of benzyl phenyl ether at 450 °C (TS energy barrier, kJ?mol^?1).

Fig.3 Induced pyrolysis initiated by H radicals from the hydrogen-donor source at 450 °C (TS energy barrier, kJ?mol^?1).

Fig.4 H extraction from hydroxyl or tetralin initiated by benzyl radicals at 450 °C (TS energy barrier, kJ?mol^?1).

Fig.5 Induced pyrolysis by CH₃ radicals at 450 °C.

Fig.6 Induced pyrolysis initiated by H radicals at 450 °C (TS energy barrier, kJ?mol^?1).

Fig.7 Scheme of induced pyrolysis by radicals at 450 °C (CR: coal radical fragments; TS energy barrier, kJ?mol^?1).

Fig.8 (a) Variation of phenolic compounds and (b) water yields with different ratios of tetralin to coal at 400 °C and 6 MPa of H₂.

Fig.9 Variation of the ratios of (a)

I C a l ? H / I C a r ? H

and (b) I_C–O–C/

I C a r ? H

with the ratio of tetralin to coal.

Fig.10 EPR spectral analysis of NHI under different conditions: (a) 2, (b) 4, and (c) 6 times tetralin added at 400 and 450 °C, 40 min.

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