Oxidative dehydrogenation of propane over V2O5 and K2O-V2O5 impregnated MgAl2O4 catalysts

V2O5 and K2O-V2O5 impregnated MgAl2O4 catalysts were prepared and tested for the oxidative dehydrogenation of propane. The as-synthesized catalysts were characterized by using the XRD, BET, NH3-TPD, TPR, and XPS methods. The catalytic tests were performed in a fixed bed tubular quartz reactor system between 450 and 550 degrees C. It was observed that the conversion of propane increased but hydrocarbon selectivity decreased with increasing temperature over the V2O5/MgAl2O4 catalysts. The BET surface area values and surface acidities decreased upon potassium addition for the K-V2O5/MgAl2O4 catalysts, which resulted in a drastic drop in the conversion values obtained. The propylene and total hydrocarbon selectivities increased with increasing temperature

A comparative study for removal of different dyes over M/TiO2 (M = Cu, Ni, Co, Fe, Mn and Cr) photocatalysts under visible light irradiation

The purpose of this work is to design and develop a series of stable and effective TiO2 photocatalysts prepared by a modified precipitation method. In order to improve the photo response of the TiO2 to the visible region, the effect of addition of six successive transition metal elements of fourth period, namely chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) was studied. Two different types of dyes, methyl orange (MO, azo dye) and methylene blue (MB, thiazine dye group), were used to investigate the influence of structure of dyes on the photocatalytic degradation rates. The results showed that loading titania with 0.3 wt.% of different transition metal elements was found to have significant influences on the crystallographic structure, physical properties and optical absorption properties of titania based catalysts, as well as catalytic activity during dye degradation reactions. The optical reflection edge was obviously shifted to the visible light range with the transition metal additives. The band gap energies of the doped TiO2 samples were considerably narrower than that of plain TiO2. The different activity levels of the catalysts for both dyes clearly show that the photocatalytic activity of samples strongly depended on the metal dopant used. Among all the catalysts, Cu/TiO2 sample exhibited the highest photocatalytic activity under visible light for both of the dyes owing to the low band gap energy and delayed electron-hole recombination. (C) 2015 Elsevier B.V. All rights reserved