Quantitative contribution of defective benzene on brominated high-sulfur petroleum coke to remove gaseous mercury: Experimental and density functional theory study

The contributions of defective benzene on high-sulfur petroleum coke (HSPC) during mechanochemistry to Hg⁰ removal have not been quantified. In this study, mercury removal performance, identification of defective benzene, defective model construction, and mercury oxidation pathway were performed by experiment and density functional theory (DFT). The results illustrate that thiophene edge (TE) reduced the energy requirement of defect generation. Bromine was favorable to bind on the light or moderate defective configurations, further improving the reactivity of the core atoms. Defective brominated edges led to the spatial adsorption of Hg⁰. While TE and oxygen edge (OE) cannot work as pure carbon edge (PCE), the main contributor to improving mercury removal efficiency was the brominated defective pure carbon edge, where the released Hg⁰ adsorption energy of −180 kJ/mol was significantly higher than oxidation energy of 57.94 kJ/mol. Besides adsorbent of Hg⁰, the defective HSPC could play a catalytic-like role. Both experiment and calculation results are well consistent. This study can provide a theoretical understanding of mechanochemical modification process of modified carbon-based precursors for Hg⁰ removal.