Effect of Fe₂O₃ on the pyrolysis of two demineralized coal using in-situ pyrolysis photoionization time-of-flight mass spectrometry

Influence of Fe₂O₃ on the pyrolysis products distribution of demineralized Hongshaquan (HSQ) and Daliuta (DLT) coal was investigated by a novel in-situ pyrolysis vacuum ultraviolet single photon ionization time-of-flight mass spectrometry. The experiment samples were obtained by mechanical mixing of Fe₂O₃ and demineralized coal from acid elution with the mass ratio of 10∶1, 5∶1 and 2∶1. Due to the characteristics of in-situ sampling, soft ionization and high vacuum environment, the initial pyrolysis volatiles including alkenes, aromatic hydrocarbons, phenols, bi-phenols and a small amount of sulfur and nitrogen-containing substances can be detected. The results show that Fe₂O₃ has similar influence on the products distribution of two demineralized coal, and it is relatively stronger on DLT coal than that on HSQ. With the increase of Fe₂O₃ content, the light fraction content is promoted such as alkenes and aromatic hydrocarbons, but bi-phenols are obviously inhibited. Correspondingly, the heavy products are also decreased, and the evolution peak temperatures of the product increase. Fe₂O₃ is successively reduced to FeO and Fe while transforming heavy components into light components. The increase of aliphatic carbon (or aromatic hydrocarbon substituted carbon) during coal pyrolysis process is mainly responsible for the decrease pyrolysis peak temperature.