New insights into the influence of SO2 as an activator on the physicochemical properties of carbon materials and the influence of S-doping on SO2 adsorption: Experimental and density functional theory study

Flue gas dry desulfurization using activated coke (AC) as an adsorbent is considered the most promising environmentally friendly technology in adsorbent circulation and sulfur resource recovery. This work studied the effect of SO2 as an activator on the physicochemical properties of carbon materials and discusses the influence of S doping on SO2 adsorption. The results indicate that elemental S is the main product of SO2 carbothermal reduction within the temperature range of 700-900 degrees C, with a yield ranging from 72% to 88.5%. Simultaneously, the pore structure of the AC was significantly developed, with a maximum specific surface area of 347.26 m2/g that was mainly composed of micropores. During the carbothermal reaction between SO2 and C, a large amount of S doping and the formation of thiophene and sulfur oxide functional groups were induced, which proved beneficial for the removal of SO2 through dynamic adsorption testing. Density functional theory calculations showed that the incorporation of S-containing functional groups changed the charge-distribution characteristics of the carbon surface, thereby strengthening the physisorption of SO2 and enhancing the chemisorption of unsaturated carbon. This study provides a new concept for AC desulfurization technology and describes process design and operation.