The atmospheric residue (AR) was pyrolyzed at multiple temperatures (400 to 700 °C) for 90 minutes at a 10 °C/min heating rate to produce an upgraded liquid fuel and coke. The liquid fuel produced at 400 °C had the highest API gravity. Thus, its chemical composition was determined by 1HNMR spectroscopy and GC-MS technique. The produced coke was converted into active carbon (AC) via the KOH-activation route by optimizing the impact of the carbonization period and temperature, besides the KOH impregnation ratio, on the yield and the iodine number of AC. The ideal AC sample was produced at 750 °C for 1 h and a 2:1 KOH: coke impregnation ratio. This AC was analyzed for its BET surface area, pore volume, XRD, FE-SEM, EDX, and FTIR. The BET surface area of the best AC was 742.20 m2/g, while its mean pore diameter was 1.95 nm, suggesting its microporosity. The AC was tested to eliminate dibenzothiophene (DBT) from model fuel and gasoline. The ultimate removal of DBT was achieved by employing 0.35 g of AC at 40 °C for 30 minutes. In conclusion, the experimental outcomes suggest that this AC can successfully eliminate DBT from fuels.