Isotope Analysis for Understanding the Tar Formation in the Integrated Process of Coal Pyrolysis with CO2 Reforming of Methane

Abstract

In our previous studies, a higher tar yield can be obtained from a novel integrated process of coal pyrolysis with CO2 reforming of methane (CRMP) than the traditional coal pyrolysis process. However, the tar formation mechanism in the CRMP process was not yet clear. In this work, deuterated methane (CD4) was used to investigate the formation mechanism of coal tar in the integrated process through analyzing the chemical compounds of coal tar with gas chromatography and mass spectrometry (GC/MS) analysis. The results showed that deuterium was detected in the main compounds of tar with the existing form of [•D] and [•CD3]. Deuterium in CD4 took part in the formation of coal tar compounds, indicating that the atmosphere took an important role in the formation of coal tar. When the formation process of certain compounds was analyzed, it can be deduced that the higher coal tar yield in the CRMP process can be attributed to the interaction of free radicals formed from the CO2 reforming of methane and from the cracking of the coal chemical structure in pyrolysis.