Catalytic oxidation of 1,2-dichlorobenzene over ABO3-type perovskites

Several ABO(3)-type perovskite oxides (A = La, Y, Nd or Gd; B = Fe, Mn, Cr or Co) have been investigated as catalysts for the oxidation of 1,2-dichlorobenzene (o-DCB), a model compound for the highly toxic polychlorinated dibenzodioxins. Initial transient and steady state activity measurements were conducted with all catalysts in the absence and presence of water. Perovskites containing Cr in the B-site were more active than perovskites containing other transition metals, with YCrO3 being the mast active catalyst among the different systems studied. Furthermore, YCrO3 did not show any loss of its initial activity after several hours on stream. Other perovskites lost 10-20% of their initial activity within the first 5-10 h on stream. This loss was associated with a corresponding loss in BET surface area. With the exception of LaCoO3, all perovskites retained their crystalline structure upon exposure to o-DCB under reaction conditions. LaCoO3 was converted to LaOCl and Co3O4. The presence of water appeared to enhance the catalytic activity of some perovskites. This effect can be attributed to a faster removal of Cl- ions from the catalyst surface via their reaction with water. (C) 2000 Elsevier Science B.V. All rights reserved.