Efficient removal of toluene over palladium supported on hierarchical alumina microspheres catalyst

Abstract Catalyst support is crucial to modulating and immobilizing the active metal phases and the catalytic performance can be optimized by the rational design of support. Herein, the hierarchical alumina microspheres with abundant coordinatively unsaturated pentacoordinated Al3+ (Al3+penta) sites were constructed by a facile solvothermal method and then employed as the support materials to anchor Pd species. XPS and NMR results revealed that Pd species were prone to the adsorption, dispersion and stabilization over Al3+penta sites by strong interaction in the form of Pd4+ species. During the catalytic oxidation process, the crystal structure and morphology of Pd/Al2O3 catalysts remained stable, but the surficial lattice oxygen and cationic Pd4+ species presented a distinct increase. In comparison with the fresh catalyst, the catalytic performance of the used Pd/Al2O3 catalysts exhibited a significant improvement and still kept unchanged even after the multiple consecutive catalytic process. The used Pd/Al2O3 catalyst also possessed the excellent water tolerance and almost 1000 ppm toluene at a weight hourly space velocity of 60 000 mL gcat−1 h−1 could be converted into nontoxic CO2 and H2O over the catalyst surface.