Weight loss and gas release behavior of mengdong coal (MD) during pyrolysis was investigated using thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TGA-FTIR), and char evolution of coal chars derived at different pyrolysis temperature were analyzed with two dimensional perturbation correlation infrared spectroscopy (2D-PCIS) method to reveal the mechanism of mengdong coal pyrolysis. The MD coal showed a significant weight loss at 300- 600 degrees C during pyrolysis. Free OH groups reacted before OH-nand self associated n-mers hydrogen bond. The demethylenation reaction sequence was aliphatic R-3-CH groups and asymmetric aliphatic R-CH3 > symmetric aliphatic R-2-CH2 > asymmetric aliphatic R-2-CH2. CO2 releasing mainly resulted from the crack of C-O in aryl ethers groups, C-O in alcohols in coal molecular. The effect of K2CO3 on char structure was also studied. The results showed that, inherent mineral of coal presented stronger catalytic effects towards pyrolysis. K2CO3 addition influenced the reaction sequences of R-3-CH, symmetric R-2-CH2 and asymmetric R-2-CH2 insignificantly, but could significantly change the correlation of C-O, C=O, CH-CH3, and aromatic C=C bond. (C) 2017 Elsevier B.V. All rights reserved.