Experimental analysis of the evolution of soot structure during CO₂ gasification

The morphology and nanostructure evolution during gasification was examined for a coal-derived soot and, to permit comparisons to other research, two carbon black samples. The investigation examined four different conversion extents at 1273 and 1473 K. The primary particle diameter decreased significantly during the initial stage and then changed slowly. The gasification behavior varied with the initial nanostructure and treatment temperature. At 1273 K the consumption behavior followed a hybrid mode comprised of shrinking core and homogeneous reaction models. However, at 1473 K, a previously unobserved gasification behavior occurred with the soot forming concentric spheres. Here the gasification progressed by initially forming micropores, followed by insufficient permeation of oxidant with the subsequent consumption of the core, ultimately forming hollow particles. Raman spectra and X-ray diffraction patterns indicated there was a transformation from initially ordered to less well-ordered structure. Partial gasification induced disordering to different extents, accompanied by a slight maturing associated with thermal annealing. The crystallites were preferentially consumed along the graphitic edges for coal-derived soot. At the start of gasification, the density of the soot increased but subsequently declined. Abundant micropores with multimodal distributions were newly generated and continually developed during gasification.