Effect of Al2O3 doping on the structure and performance of an Al2O3/Fe2O3 catalyst for mercury oxidation

Abstract In this study, the thermal stability of a Fe2O3 catalyst for mercury oxidation was significantly improved by doping with Al2O3. After 1 hr, the catalyst doped with 10 wt.% Al2O3 still exhibited a mercury conversion efficiency of 70.9%, while the undoped sample even lost its catalytic activity. Doping with Al2O3 retarded the collapse of the catalyst mesoporous structure during high-temperature calcination, and the doped samples maintained a higher specific surface area, smaller pore size, and narrower pore size distribution. Transmission electron microscope images revealed that after calcination at 350°C, the average size of the catalyst grains in Fe2O3 was 23.4 nm; however, the corresponding values for 1%Al2O3/Fe2O3, 3%Al2O3/Fe2O3, and 10%Al2O3/Fe2O3 were only 13.3, 7.1, and 4.7 nm, respectively. Results obtained from X-ray diffraction and thermogravimetry coupled with differential scanning calorimetry confirmed that doping with Al2O3 also retards the crystallization of the catalysts at high temperature, constraining catalyst grains to a smaller size.