Temperature-dependent structural evolution of petroleum coke under FTIR spectroscopy-aromaticity changes toward low-carbon development

Abstract

Petroleum coke, a gray-black aromatic solid generated during petroleum refining, poses significant challenges and opportunities for achieving carbon peaking and neutrality goals. This study employs Fourier Transform Infrared Spectroscopy (FTIR) combined with peak fitting analysis to systematically investigate the temperature-dependent structural evolution of petroleum coke. Key parameters, including aromaticity index (Iar), branching ratio (CH3/CH2), functional group evolution (C=O, C-O, C=C), and aromatic substitution patterns, were quantitatively characterized at varying pyrolysis temperatures. Results reveal a dual-phase structural transformation mechanism: moderate heating enhances naphthene dehydrogenation, increasing aromatic nucleus C=C bonds and overall aromaticity via ring-condensation. However, excessive temperatures induce structural degradation through enhanced oxidation and bond cleavage, reducing aromatic C=C content. Notably, high-temperature polymerization promotes aromatic ring expansion and intermolecular hydrogen bonding, leading to self-associated supramolecular aggregates. These findings elucidate the temperature-sensitive aromatic reorganization in petroleum coke, providing critical insights for optimizing its thermal utilization in low-carbon energy systems.