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Metal-containing vanadium oxide bronzes (M x V 2 O 5 ; M = Cu, Ag and Ca) have been prepared, characterized (before and after reaction) by various physicochemical techniques, and tested in the partial oxidation of H 2 S. The catalysts were prepared hydrothermally at 175 °C (from gels containing M /V molar ratios of 0.17 or 0.33) and heat-treated at 500 °C/2 h in N 2. The most effective catalysts, showing a sulfur selectivity greater than 95 % for a H 2 S conversion beyond 90 %, were those presenting vanadium oxide bronze (β-Cu 0.261 V 2 O 5 or Ag 0.333 V 2 O 5) as the main crystalline phase. Cu- and Ag-containing vanadium oxide bronzes were stable under reaction conditions. For calcium containing materials (mainly presenting the Ca 0.17 V 2 O 5 bronze phase), the formation of CaSO 4 has been observed during the reaction, which resulted in a negative effect on both activity and selectivity. The nature of active and selective sites in this type of catalysts, as well as the role of promoters, are also discussed. [Display omitted] • β- M x V 2 O 5 bronzes (M=Cu, Ag or Ca) have been successfully synthesized. • β- M x V 2 O 5 bronzes as active and selective catalysts in H 2 S partial oxidation. • Selectivity to sulfur directly related to Me-dopant and/or Me/V ratio. • V4+-O-V5+ pairs present in β- M xV 2 O 5 structure prevent the oveoxidation of S to SO 2. • Surface deposition of SO 4 2- species lead to catalyst's deactivation. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction (SCR) of NO with NH 3 in the presence of O 2 and H 2 O over a series of Fe and/or Cu-containing ZSM-5 catalysts prepared by solid state ion exchange (SSIE) was investigated. A wide number of experimental techniques (ICP-AES, XRD, HRTEM, 27 Al MAS NMR, NH 3 -TPD, DRS UV-vis, H 2 -TPR and EPR) have been applied to understand the metal exchange order effect on the composition, texture, structure, acidity and speciation of bimetallic materials. DRS UV-vis, H 2 -TPR, EPR and HRTEM experiments conducted on Cu-Fe-ZSM-5 and Fe-Cu-ZSM-5 allowed the identification of both isolated and clustered metal species differing in their amount, environment and degree of aggregation leading to a different catalytic behaviour of both catalysts. [ABSTRACT FROM AUTHOR]

V- and/or Co-containing aluminophosphates with AEI structure (CoAPO-18, VAPO-18 and VCoAPO-18) have been prepared by hydrothermal synthesis, characterized by several physicochemical techniques (SBET, thermogravimetric analysis, XRD, solid state MAS NMR, UV–vis, EPR, TPD), and tested in the oxidative dehydrogenation of ethane. The results obtained by the spectroscopic techniques employed here suggest that V (V5+ and VO2+) and Co2+ atoms are isomorphically incorporated into the aluminophosphate framework, although some vanadium is involved in an extraframework oxide, especially at high contents. Upon calcination in air of the V, Co-containing samples with the AEI structure, most vanadium and cobalt oxidate to V5+ and Co3+ and present redox activity, while only Co-containing materials posses acid properties. Comparison with Co-containing AlPO-5 evidences that the strength of acid sites depends on the framework structure. VCoAPO-18 catalysts are active and selective in the oxidative dehydrogenation of ethane with selectivities to ethylene higher than the corresponding VAPO-18 or CoAPO-18. The catalytic results give evidence of the incorporation of V and Co into the AlPO-18 structure, and the segregation of an oxide phase in V-rich samples. The V- and/or Co-containing AlPO-18 are more selective in the ODH of ethane than the corresponding materials with AFI structure (i.e. VCoAPO-5, VAPO-5 or CoAPO-5). [Copyright &y& Elsevier]