Catalytic effect of metal chlorides on coal pyrolysis and gasification part I. Combined TG-FTIR study for coal pyrolysis

The catalytic effects of three metal chlorides, including KCl, ZnCl2, and MnCl2, on the pyrolysis of lignite were investigated by thermogravimetry (TG) coupled with Fourier transform infrared (TG-FTIR) analysis from 105 °C to 1000 °C at a heating rate of 10 °C/min. The procedure of acid washing and the addition of metal chlorides had little effect on the structure of coal. The catalytic effect of inherent mineral became obvious only when the temperature was higher than 660 °C. The addition of metal chlorides promoted the pyrolysis process when the temperature was lower than 400 °C and higher than the critical temperature. DTG curve was fitted into six sub-curves to further analyze the pyrolysis process especially the breakage of chemical bonds. All three metal chlorides had a good catalytic effect on the quantity of CH4 production but the opposite effect on CO production. MnCl2 was the most favorable metal chloride for the production of CH4. The catalytic mechanism of KCl was different from that of MnCl2 and ZnCl2 on coal pyrolysis.