Total oxidation of toluene – over Pd/mesoporous materials catalysts
Palladium was supported on mesoporous SBA-15 and mesoporous Aluminium silicate (MAS) materials for total oxidation of toluene. Mesostructured aluminium silicate MAS has been synthesized in strong acidic media by assembly of preformed MFI precursors with triblock copolymer.
Various techniques including XRD, N2 adsorption, FT-IR spectroscopy and 27Al MAS NMR were employed for the materials characterization. Characterization results indicate that the calcined MAS material is pure mesoporous phase without bulky zeolite crystals and that the mesoporous walls contain the MFI structure building units.
0.5wt % of palladium was introduced on SBA-15 or MAS via incipient wetness technique using palladium nitrate as the Pd source.
The 0.5wt% Pd/SBA-15 and o.5wt% Pd/MAS catalysts resulted in highly active catalysts for deep oxidation of toluene: they are active at low temperature and are totally selective for CO2 and H2O. The Pd/SBA-15 catalyst resulted to be more active than the Pd/MAS catalyst.
Volatile Organic Compounds (VOCs) emitted in air during industrial processes are recognized as major contributors to air pollution and are considered to be dangerous to human health (1). Catalytic oxidation is one of the most important processes for VOCs destruction, since VOCs oxidation over a catalyst takes place at temperature much lower than those required for thermal destruction (2). Catalytic oxidation of VOCs has been performed either with noble-metal catalysts or with non-noble metal catalysts, where the noble-metal catalysts generally exhibited better catalytic performance (3).
The design and synthesis of metal-containing mesoporous materials having pore sizes greater than 2 nm are the main areas of research in the last decade, because their high surface area and pore size help to overcome the limitations of the conventional small pore zeolite catalysts. However, although the heteroatoms are introduced into mesoporous materials, they do not show as high catalytic activity as they do in zeolites, which can be attributed to the amorphous nature of the pore walls.
Several synthesis pathways have been explored in the la ...