Effect of CO2 on the characteristics of soot derived from coal rapid pyrolysis

The present work aims to investigate the effects of a CO2-rich atmosphere on the characteristics of coal-derived soot. The rapid pyrolysis of Shenfu bituminous coal was conducted in a Drop tube furnace (DTF) in N2 and CO2 atmospheres with a wall temperature of 1073-1473 K and residence time below 700 ms. The yields and microstructure characteristics of N2-soot and CO2-soot were analysed by using a series of techniques (elemental analysis, HRTEM, Raman, XRD, FT-IR and thermogravimetry techniques). CO2 enhanced the soot formation and proceeded the dehydrogenation. CO2 improved the order of internal carbon lattices, enhanced the lateral extension of carbon nanostructures, decreased the interplanar spacing of the graphene layers and also promoted the stack of polyaromatic layers. The variations of the SOLO, DUO, TRIO and QUARTO structures were also analysed, and the contribution of CO2 was found to reduce the defects of the basic structure units (BSU). The defects of soot were an important indication of the initial gasification reactivity. Overall, CO2-soot was more mature and low active than N2-soot.