Effect of calcination temperature on properties of waste alkaline battery-based catalysts for deep oxidation of toluene and o-xylene

To evaluate waste alkaline battery (WB) as a catalyst for deep oxidation of toluene and o-xylene, we investigated how calcination temperature influenced the catalytic activity of WB-based catalyst for catalyst preparation. Physicochemical properties of WB-based catalysts were characterized by BET (Brunauer Emmett Teller) analysis, XRD (X-ray diffraction), SEM/EDX (scanning electron microscope/energy dispersive X-ray), TGA/DTA (thermo gravimetric analysis/differential thermal analysis), and H₂-TPR (hydrogen temperature programmed reduction). Major elements of WB-based catalysts were carbon, manganese, zinc, and iron. The catalytic activity of WB-based catalyst was significantly influenced by calcination temperatures ranging from 300 °C–600°C. An increase calcination temperature resulted in a significant decrease in the BET surface area and concentrations of surface carbon and chlorine of the WB-based catalyst, while levels of other components increased. The average pore diameter of the WB-based catalyst calcined at 400 °C (WB (400) catalyst) was the smallest. The concentrations of manganese and iron in WB (400) catalyst were the highest, while those of manganese and iron in the WB-based catalyst calcined at 300 °C (WB (300) catalyst) were the lowest. Therefore, a good performance of WB (400) catalyst was likely due to its higher concentrations of manganese and iron and smaller pore size. When GHSV (gas hourly space velocity) was 40,000 h⁻¹, toluene and o-xylene were completely oxidized on WB (400) catalyst at 430 °C and 440 °C, respectively.