Catalytic oxidation of chlorobenzene over Pd/perovskites

The catalytic performances of pre-reduced palladium catalysts supported on lanthanum based perovskites LaBO3 (B=Co, Mn, Fe, Ni) were investigated for the total oxidation of chlorobenzene (PhCl; 1000ppmv) in air. The catalysts were prepared using a wet impregnation technique and Pd-nitrate was used as a palladium precursor. The catalytic performances were compared to those of a reference palladium catalyst supported on a conventional support, namely γ-Al2O3. Easiness of chlorobenzene destruction was found to follow the sequence based on the T50 values (temperature at which 50% of chlorobenzene was converted into products): Pd/LaMnO3+δ (243°C)>Pd/LaFeO3 (270°C)>Pd/Al2O3 (348°C)>Pd/LaCoO3 (360°C)>Pd/LaNiO3 (408°C). Complete conversion of chlorobenzene is reached at ca. 320–500°C, but at those temperatures substantial amounts of polychlorinated benzenes are formed. Quasi in situ XPS studies were monitored on Pd/LaCoO3 and Pd/LaFeO3 after each stage of the global process, namely after calcination, reduction and exposure to the flowing reactive mixture (1000ppmv PhCl in air) from room temperature to 230 and 310°C (Pd/LaFeO3) and to 280°C (Pd/LaCoO3). It was shown that the calcination treatment leads to a palladium which a BE higher than that of PdO and to a (B/La)XPS