Remarkable promotion effect of 2,3-Dimethyl-2,3-diphenylbutane on the oxidation stabilization of coal tar pitch

Oxidation stabilization is an extremely important step for maintaining microstructure as well as boosting performance of pitch-based carbon fibers, carbon/carbon composites, etc. However, the low reactivity of pitch molecules with oxygen and the sluggish diffusion kinetics of oxygen seriously hinder the oxidation process, leading to tremendous consumption on energy and time thereby. To overcome the problem, a novel free-radical-induced oxidation strategy is proposed through the modification of raw pitch with 2,3-Dimethyl-2,3-diphenylbutane (DMDPB). The strategy allows oxidation stabilization of pitch not relying solely on oxygen diffusion and self-reactivity of pitch molecules, but also on the substantial free radicals generated from thermolabile covalent bonds of DMDPB. Particularly, the free radical concentration of the modified pitch with 10 wt.% DMDPB reaches almost 2.2 times than that of raw pitch. Consequently, the crosslinking reactions between pitch molecules are homogeneously promoted and their average molecular weight, softening point, and carbon yields are also elevated significantly. The induced reaction mechanism of DMDPB and its synergistic reaction mechanism with oxygen have also been investigated explicitly. The rapid homogeneous stabilization approach has been applied in the preparation of carbon fiber (with a diameter of ~ 18 μm) and spherical activated carbon (with a diameter of ~ 600 μm), offering an attractive perspective on low-cost preparation of pitch-based carbon materials.