[7] Qin Z H, Chen H, Yan Y J, et al. Fuel Processing Technology, 2015, 133: 14.

[8] Zhang X D, Zhang S, Li P P, et al. Fuel Processing Technology, 2018, 174: 123.

[9] Chen Yanyan, Mastalerz M, Schimmelmann A. International Journal of Coal Geology, 2012, 104: 22.

[10] Machnikowska H, Krzton A, Machnikowski J. Fuel, 2002, 81(2): 245.

[12] Wang S Q, Tang Y G, Schobert H H, et al. Energy Fuels, 2011, 25: 5672.