Effect of metal salts on the decomposition characteristics of Mengdong lignite.

In this study, the apparent activation energy of coal samples during pyrolysis with NiCl2, FeCl3, Ni(NO3)2 and Fe(NO3)3 in-situ loaded on was calculated. The results show that metal salts promote the devolatilization process with the activation energy decreased by 24.28%, 13.27%, 38.61%, and 41.53%, corresponding to NiCl2, FeCl3, Ni(NO3)2 and Fe(NO3)3 respectively. And the catalytic effect on the evolution of H2 and CH4 was also studied via TG-MS test. Except Fe(NO3)3, the adding of other metal salts made activation energy of CH4 and H2 descend. NiCl2-coal sample has the least activation energy of CH4, which indicates a closer interaction with coal matrix compared with Ni(NO3)2. However, the activation energy of H2 for NiCl2-coal sample and Ni(NO3)2-coal sample varies little. To further investigate the catalytic effect during pyrolysis, hydrogen distribution in solid residues was analyzed according to the FTIR spectrums. The relatively abundant hydrogen content in aromatic structure when ferric salts were added indicates the hydrogen transfer to aromatic rings under the effect of Fe element. And FeCl3 has a superior effect compared with Fe(NO3)3. The difference in the catalytic effect between metal nitrates and metal chlorides could be ascribed to the different behaviors during the decomposition process. [ABSTRACT FROM AUTHOR]