Gold nanoparticles supported on magnesium oxide for CO oxidation

Au was loaded (1 wt%) on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH)2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved). The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts

Preparation method and structure of active sites of FeOx/SiO2 catalysts in methane to formaldehyde selective oxidation

The effects of preparation method on surface structures and catalytic properties in the selective oxidation of CH4 to HCHO With O-2 (MPO) of low-loaded (0.09-0.43 wt.% Fe) FeOx/SiO2 catalysts have been addressed. The DR-UV-Vis patterns prove that the preparation route, based on "adsorption-precipitation" of Fe-II precursors on silica under anaerobic conditions (ADS/PRC), enhances the dispersion of the active phase in comparison to the conventional "incipient-wetness" route. FTIR of adsorbed NO data signal the presence on silica of several "isolated" Fe moieties with a different surface coordination. A higher FeOx dispersion confers a superior performance to ADS/PRC FeOx/SiO2 catalysts in terms of specific rate of CH4 conversion (sigma(CH4)) and HCHO formation (epsilon(HCHO)) of Fe atoms which result in quite larger HCHO productivity values (STYHCHO

Hydrogen production by methanol steam reforming carried out in membrane reactor on Cu/Zn/Mg-based catalyst

The methanol steam reforming (MSR) reaction was studied by using both a dense Pd-Ag membrane reactor (MR) and a fixed bed reactor (FBR). Both the FBR and the MR were packed with a new catalyst based on CuOAl2O3ZnOMgO, having an upper temperature limit of around 350 °C. A constant sweep gas flow rate in counter-current mode was used in MR and the experiments were carried out by varying the water/methanol feed molar ratio in the range 3/1-9/1 and the reaction temperature in the range 250-300 °C. The catalyst shows high activity and selectivity towards the CO2 and the H2 formation in the temperature range investigated. Under the same operative conditions, the MR shows higher conversions than FBR and, in particular, at 300 °C and H2O/CH3OH molar ratio higher than 5/1 the MR shows complete methanol conversion. © 2008 Elsevier B.V. All rights reserved. 10.1016/j.cattod.2008.03.01