Pd0.01Ru0.01Ce0.98O2-delta: A highly active and selective catalyst for the liquid phase hydrogenation of p-chloronitrobenzene under ambient conditions

Nanostructured bimetal ion substituted ceria, Pd0.01Ru0.01Ce0.98O2−ı (PdRuC2), prepared for the first time by a novel solution combustion synthesis and characterized employing XRD, BET, HRTEM and XPS has been shown to be very active and selective than the monometal ion substituted analogue Pd0.02Ce0.98O2−ı (PdC2), whereas Ru0.02Ce0.98O2−ı (RuC2) is inactive towards liquid phase hydrogenation of p-chloronitrobenzene to p-chloroaniline under ambient conditions. Structural studies show metal ion substituted ceria as the predominant phase. The hydrogenation over PdRuC2 is completed beyond 75 min with 100% selectivity. Conversely, PdC2 hydrogenates ∼40% of p-chloronitrobenzene with 82% selectivity. Increase of temperature from 35 ◦C to 80 ◦C showed a little higher activity of PdRuC2 but with a lower selectivity. The as-prepared and aged forms of PdRuC2 showed similar activity, whereas PdRuC2 heat-treated at 500 ◦C increased the conversion and the 800 ◦C heated catalyst reduced it (both ∼2%) indicating high thermal stability. Maximum hydrogenation activity has been observed in ethanol as compared to methanol and butanol. The PdRuC2 catalyst also shows excellent hydrogenation activity towards o-, m-chloronitrobenzene and nitrobenzene. The enhancement of activity and selectivity of Pd in presence of Ru in the PdRu bimetal ionic catalyst for the hydrogenation reaction has been attributed to involvement of remarkable Ru4+-promotion in Pd0.01Ru0.01Ce0.98O2−ı.Postprint (published version

Pd0.01Ru0.01Ce0.98O2-delta: A highly active and selective catalyst for the liquid phase hydrogenation of p-chloronitrobenzene under ambient conditions

Nanostructured bimetal ion substituted ceria, Pd0.01Ru0.01Ce0.98O2−ı (PdRuC2), prepared for the first time by a novel solution combustion synthesis and characterized employing XRD, BET, HRTEM and XPS has been shown to be very active and selective than the monometal ion substituted analogue Pd0.02Ce0.98O2−ı (PdC2), whereas Ru0.02Ce0.98O2−ı (RuC2) is inactive towards liquid phase hydrogenation of p-chloronitrobenzene to p-chloroaniline under ambient conditions. Structural studies show metal ion substituted ceria as the predominant phase. The hydrogenation over PdRuC2 is completed beyond 75 min with 100% selectivity. Conversely, PdC2 hydrogenates ∼40% of p-chloronitrobenzene with 82% selectivity. Increase of temperature from 35 ◦C to 80 ◦C showed a little higher activity of PdRuC2 but with a lower selectivity. The as-prepared and aged forms of PdRuC2 showed similar activity, whereas PdRuC2 heat-treated at 500 ◦C increased the conversion and the 800 ◦C heated catalyst reduced it (both ∼2%) indicating high thermal stability. Maximum hydrogenation activity has been observed in ethanol as compared to methanol and butanol. The PdRuC2 catalyst also shows excellent hydrogenation activity towards o-, m-chloronitrobenzene and nitrobenzene. The enhancement of activity and selectivity of Pd in presence of Ru in the PdRu bimetal ionic catalyst for the hydrogenation reaction has been attributed to involvement of remarkable Ru4+-promotion in Pd0.01Ru0.01Ce0.98O2−ı

Liquid phase selective oxidation of benzene over nanostructured Cu xCe1-xO2-\u3b4 (0.03 64 x 64 0.15)

Liquid phase direct oxidation of benzene to phenol was carried out over copper loaded on oxides such as ceria, alumina, magnesia, ferric oxide, zinc oxide with 30% H2O2 as oxidant under atmospheric pressure. Of all the catalytic formulations prepared via a novel solution combustion synthesis, the ceria based catalysts showed highest activity. Particularly, over the Cu0.10Ce0.90O2_delta catalyst, 43% conversion of benzene with 100% selectivity was observed at 70 degrees C and atmospheric pressure. The activity of this combustion synthesized catalyst is also higher than the corresponding catalyst prepared by incipient wetness impregnation and coprecipitation methods. Powder XRD, TEM and XPS studies show ionically substituted copper over ceria as the predominant phase in the combustion derived catalyst whereas on the impregnated and coprecipitated catalysts copper is present in the dispersed copper oxide form. Influences of temperature and time, H2O2 concentration and solvent have also been investigated. Enhanced activity over the combustion synthesized catalyst wherein Cu2+ ion is present as substitutional ion in ceria has been attributed to Cu-O-Ce ionic interaction. Ionic substitution also brings stability to the active copper ion component in the combustion synthesized catalyst with lower risk of Cu-leaching as compared to the corresponding impregnated and coprecipitated catalysts as evidenced from the recycling experiments. (C) 2014 Elsevier B.V. All rights reserved

Liquid phase selective oxidation of benzene over nanostructured CuxCe1-xO2-delta (0.03 <= x <= 0.15)

Liquid phase direct oxidation of benzene to phenol was carried out over copper loaded on oxides such as ceria, alumina, magnesia, ferric oxide, zinc oxide with 30% H2O2 as oxidant under atmospheric pressure. Of all the catalytic formulations prepared via a novel solution combustion synthesis, the ceria based catalysts showed highest activity. Particularly, over the Cu0.10Ce0.90O2_delta catalyst, 43% conversion of benzene with 100% selectivity was observed at 70 degrees C and atmospheric pressure. The activity of this combustion synthesized catalyst is also higher than the corresponding catalyst prepared by incipient wetness impregnation and coprecipitation methods. Powder XRD, TEM and XPS studies show ionically substituted copper over ceria as the predominant phase in the combustion derived catalyst whereas on the impregnated and coprecipitated catalysts copper is present in the dispersed copper oxide form. Influences of temperature and time, H2O2 concentration and solvent have also been investigated. Enhanced activity over the combustion synthesized catalyst wherein Cu2+ ion is present as substitutional ion in ceria has been attributed to Cu-O-Ce ionic interaction. Ionic substitution also brings stability to the active copper ion component in the combustion synthesized catalyst with lower risk of Cu-leaching as compared to the corresponding impregnated and coprecipitated catalysts as evidenced from the recycling experiments. (C) 2014 Elsevier B.V. All rights reserved

Copper ion substituted hercynite (Cu0.03Fe0.97Al2O4): A highly active catalyst for liquid phase oxidation of cyclohexane

Copper ion substituted MAl2O4 (M = Mg, Mn, Fe, Ni and Zn) spinels, CuxM1-xAl2O4 (x = 0.03 and 0.05), have been synthesized by a single step solution combustion method. Of the various compositions studied the 3 at.% copper ion substituted hercynite, Cu0.03Fe0.97Al2O4, reported here for the first time, is shown to be much more active (similar to 92% conversion with similar to 99% selectivity) than other spinet analogues towards liquid phase oxidation of cyclohexane in acetonitrile with H2O2 as oxidant in air. Powder XRD analyses have revealed formation of pure hercynite phases. The least-square refined lattice parameters obtained from XRD data together with microstructural data by HRTEM have indicated copper ion substitution in the spinel lattice. The oxidation state of copper has been established as +2 from XPS analysis and it seem to be primarily substituted in the Fe-site of hercynite. Incorporation of the copper in the spinel structure of FeAl2O4 leading to an ionic interaction is explained to be responsible for the higher oxidation activity observed over the combustion synthesized catalyst than the corresponding impregnated catalyst which contains finely dispersed CuO crystallites. Effect of recycling (repeated thrice) has shown almost no degradation of activity of the copper ion substituted hercynite. In contrast, the analogous impregnated catalyst has shown appreciable loss of activity in the consecutive cycles due to the presence of dispersed CuO crystallites which can agglomerate with ease and subsequently leach out. (C) 2014 Elsevier B.V. All rights reserved

Selective liquid phase benzyl alcohol oxidation over Cu-loaded LaFeO3 perovskite

Copper loaded LaMO3 (M = Mn, Fe and Co) perovskites have been synthesized by a single-step solution combustion method. These materials have been investigated for liquid phase oxidation of benzyl alcohol using tertiary butyl hydrogen peroxide (TBHP) as oxidant in air at 80 degrees C under ambient pressure. Among these, the 10 at% Cu-loaded LaFeO3 has shown the best activity i.e., similar to 99% conversion with complete benzaldehyde selectivity. The formation of perovskite phase was confirmed from XRD and the presence of Cu2+ was confirmed by XPS analysis. The higher activity of the combustion synthesized catalyst has been ascribed to the presence of a poorly defined surface structure containing an amorphous CuO phase wrapping the LaFeO3 particle, as evidenced from the HRTEM analysis. The catalyst recycling tests have shown a negligible loss of activity in the consecutive cycles.Postprint (author's final draft

Copper ion substituted hercynite (Cu0.03Fe0.97Al2O4): A highly active catalyst for liquid phase oxidation of cyclohexane

Copper ion substituted MAl2O4 (M = Mg, Mn, Fe, Ni and Zn) spinels, CuxM1-xAl2O4 (x = 0.03 and 0.05), have been synthesized by a single step solution combustion method. Of the various compositions studied the 3 at.% copper ion substituted hercynite, Cu0.03Fe0.97Al2O4, reported here for the first time, is shown to be much more active (similar to 92% conversion with similar to 99% selectivity) than other spinet analogues towards liquid phase oxidation of cyclohexane in acetonitrile with H2O2 as oxidant in air. Powder XRD analyses have revealed formation of pure hercynite phases. The least-square refined lattice parameters obtained from XRD data together with microstructural data by HRTEM have indicated copper ion substitution in the spinel lattice. The oxidation state of copper has been established as +2 from XPS analysis and it seem to be primarily substituted in the Fe-site of hercynite. Incorporation of the copper in the spinel structure of FeAl2O4 leading to an ionic interaction is explained to be responsible for the higher oxidation activity observed over the combustion synthesized catalyst than the corresponding impregnated catalyst which contains finely dispersed CuO crystallites. Effect of recycling (repeated thrice) has shown almost no degradation of activity of the copper ion substituted hercynite. In contrast, the analogous impregnated catalyst has shown appreciable loss of activity in the consecutive cycles due to the presence of dispersed CuO crystallites which can agglomerate with ease and subsequently leach out. (C) 2014 Elsevier B.V. All rights reserved

Selective liquid phase benzyl alcohol oxidation over Cu-loaded LaFeO3 perovskite

Copper loaded LaMO3 (M = Mn, Fe and Co) perovskites have been synthesized by a single-step solution combustion method. These materials have been investigated for liquid phase oxidation of benzyl alcohol using tertiary butyl hydrogen peroxide (TBHP) as oxidant in air at 80 degrees C under ambient pressure. Among these, the 10 at% Cu-loaded LaFeO3 has shown the best activity i.e., similar to 99% conversion with complete benzaldehyde selectivity. The formation of perovskite phase was confirmed from XRD and the presence of Cu2+ was confirmed by XPS analysis. The higher activity of the combustion synthesized catalyst has been ascribed to the presence of a poorly defined surface structure containing an amorphous CuO phase wrapping the LaFeO3 particle, as evidenced from the HRTEM analysis. The catalyst recycling tests have shown a negligible loss of activity in the consecutive cycles