Can Ultrasound or pH Influence Pd Distribution on the Surface of HAP to Improve Its Catalytic Properties in the Dry Reforming of Methane?

The influence of ultrasound and different pH pre-treatments during the metal doping/modification of a hydroxyapatite (HAP) support is investigated. HAP is first synthesised via a hard-template synthetic route using carbon nanorods followed by their full physiochemical characterisation. The HAP was found to be crystalline and comprised a mesoporous structure as observed via XRD and nitrogen adsorption with a BET surface area of 97.57 (±1.16) m2 g−1. Ultrasound-assisted ion exchange (IE) and incipient wetness impregnation (IW) methodologies were employed to decorate the surface of HAP with Pd0 and are compared to previous procedures. The influence of pH upon the distribution of Pd0 throughout the samples during the doping process is also studied. All the prepared samples were evaluated for their catalytic activity towards dry reforming of methane (DRM) and the reaction was monitored via a thermal conductivity detector, coupled with gas chromatography (GC-TCD). It was found that ultrasound-assisted IE significantly accelerated the process from 3 days to 3 h and with the Pd0 metal remaining highly distributed upon the HAP with minor changes in catalytic conversions. Moreover, the ultrasound-assisted IW method successfully improved the Pd0 distribution and catalytic performance. On the other hand, the dispersion of the metal was unaffected after pH treatments in IE with no catalytic improvements observed, in contrast to IW, where considerable increase in metal distribution and subsequently catalytic performance was observed

Water-soluble analogs of [RuCl3(NO)(PPh3)(2)] and their catalytic activity in the hydrogenation of carbon dioxide and bicarbonate in aqueous solution

The new water-soluble ruthenium-nitrosyl complexes [RuCl3(NO)(TPPMS)(2)] and [RuCl3(NO)(TPPTS)(2)] were synthetized and characterized by IR, H-1 and P-31 NMR spectroscopies. The NO stretching frequencies, nu(NO) = 1870 cm(-1) (TPPMS) and 1883 cm(-1) (TPPTS) suggest a linear Ru-N-O arrangements. Reactions with OH- yield the corresponding [RuCl3 (NO2)(P)(2)] derivatives, furthermore, [RuH(NO)(P)(3)] is formed with TPPMS or TPPTS, respectively, under 100 bar H-2 pressure. The new complexes are suitable precatalysts for the hydrogenation of carbon dioxide and/or bicarbonate in aqueous solutions up to a turnover frequency of 400 h(-1) under relatively mild conditions (30 bar H-2, 70 degreesC). (C) 2003 Elsevier Science B.V. All rights reserved

Selective Aerobic Oxidation of 5-Hydroxymethylfurfural in Water Over Solid Ruthenium Hydroxide Catalysts with Magnesium-Based Supports

Solid catalyst systems comprised of ruthenium hydroxide supported on magnesium-based carrier materials (spinel, magnesium oxide and hydrotalcite) were investigated for the selective, aqueous aerobic oxidation of the biomass-derived chemical 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid (FDA), a possible plastics precursor. The novel catalyst systems were characterized by nitrogen physisorption, XRPD, TEM and EDS analysis, and applied for the oxidation with no added base at moderate to high pressures of dioxygen and elevated temperatures. The effects of support, temperature and oxidant pressure were studied and optimized to allow a quantitative yield of FDA to be obtained