Evolution of char structure during mengdong coal pyrolysis: Influence of temperature and K2CO3

Abstract

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°C during pyrolysis. Free OH groups reacted before OH-πand self-associated n-mers hydrogen bond. The demethylenation reaction sequence was aliphatic R3-CH groups and asymmetric aliphatic R-CH3>symmetric aliphatic R2-CH2>asymmetric aliphatic R2-CH2. CO2 releasing mainly resulted from the crack of CO in aryl ethers groups, CO 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 R3-CH, symmetric R2-CH2 and asymmetric R2-CH2 insignificantly, but could significantly change the correlation of CO, CO, CHCH3, and aromatic CC bond.