Catalytic oxidation of 1,2-dichlorobenzene over CaCO3/α-Fe2O3 nanocomposite catalysts

CaCO3/alpha-Fe2O3 nanocomposites were synthesized by one-pot method to develop a low-cost and environmentally friendly technology for the catalytic oxidation of 1,2-dichlorobenzene (o-DCB), a model of chlorinated volatile organic compounds. The nanocomposites were characterized by FAAS, XRD, N-2 adsorption/desorption, TEM and XPS. Activity measurements were conducted in the range of 200-500 degrees C, in both the presence and absence of water. Among the tested catalysts, the nanocomposite with 9.5 mol% Ca showed the highest catalytic activity, which could be attributed to the promoting effect of CaCO3 on alpha-Fe2O3 with smaller crystallite size. Experimental results in the presence of water indicated that, due to the competitive adsorption of water on the active sites, there was a local minimum of catalytic activity at 350 degrees C. In situ FTIR experimental results revealed the presence of phenolate, catecholate, o-benzoquinone, carboxylate and anhydride type species on the surfaces of the catalysts during the oxidation of o-DCB. Spectral evidence discovered that the formate species were more prone to being formed on the surface of nanocomposite with 9.5 mol% Ca and then were further oxidized to CO, which directly lead to high activity of the catalyst. A mechanism involving dissociative adsorption of o-DCB on the surface of catalyst was proposed. (C) 2012 Elsevier B.V. All rights reserved.