Preparation, Characterization, and Catalytic Properties of VAPO-5 for the Oxydehydrogenation of Propane (original) (raw)

1995, Journal of Catalysis

Catalytic wet-air oxidation (CWAO) represents a promising technique for removal of toxic and non-biodegradable organic compounds from industrial wastewaters [1]. In the three-phase CWAO process, the organic pollutants are oxidized by activated O 2 species in the presence of a solid catalyst, usually at temperatures of 130-250 8C and pressures of 10-50 bar, into biodegradable intermediate products (such as low molecular weight carboxylic acids) or mineralized into CO 2 , water and associated inorganic salts. The CWAO of a variety of organic pollutants has been studied over supported noble metal catalysts, metal oxides, mixed metal oxide systems and cerium-based composite oxides [2]. Several studies regarding CWAO of various organics have been performed in the presence of activated carbon or carbon-based catalysts [3,4]. Carbon materials as activated carbon, carbon nanotubes (CNT) and carbon nanofibers (CNF) are used as catalyst carriers [5]. Carbon nanotubes are materials with special carbon nanostructures (i.e. multi-or single-walled), electronic and mechanical properties, which are promising for many technological applications including energy storage, electronics and heterogeneous catalysis [6-13]. The noble metal nanoparticles (including Pd, Pt, Ru and Rh) have been applied on CNT support and examined in selective hydrogenation reactions [11,14,15]. The main advantages of carbon nanofibers compared to activated carbon are the high purity of the material, high mechanical strength, the mesoporous nature (resulting in low internal mass-transfer resistances), which makes them interesting to promote a variety of liquid-phase reactions, such as methanol oxidation, cinnamaldehyde hydrogenation and cyclohexanol dehydrogenation [11]. Furthermore, specific metal-support interactions exist in CNFbased solids that can directly affect the catalytic activity and the selectivity. As the synthesis and consequently surface properties of activated carbons are difficult to control (one should also note diffusional problems due to inappropriate textural properties), CNF could replace their use.