02228nas a2200241   4500008004100000022001400041245017300055210006900228260007300297300001200370490000800382520125300390653003301643653002201676653002201698653002801720653002101748653002201769100002601791700001801817700002201835856012901857       2007                        eng d  a0926-860X00aGeneration of hydrogen peroxide via the selective reduction of oxygen by hydrazine sulfate over Br-promoted Pd/Al2O3 catalyst in an aqueous medium at ambient conditions0 aGeneration of hydrogen peroxide via the selective reduction of o  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAPR  a202-2090 v3233 a<p>The in situ generation of H2O2 via the selective reduction of OZ by hydrazine sulfate (in an aqueous medium) has been thoroughly investigated over the Br-promoted Pd(or PdO)/Al2O3 catalyst. The influence of the following factors have been addressed in this study: (a) Br concentration (in the reaction medium or incorporated in the catalyst); (b) reaction conditions (viz. reaction time, temperature); (c) concentrations of reducing agent and phosphoric acid in the reaction medium. Decomposition of N2H4 (from NH4-H2SO4) and its reaction with H2O2 under similar reaction conditions (in the absence of O-2) have also been studied. H2O2, which is an intermediate product of the O-2 reduction, is involved in further consecutive reactions. It can be converted to water via its decomposition and/or reaction with the unconverted NZH(4). In the presence of Br promoter, the later (reaction with unconverted N2H4) is more dominant. Both the consecutive reactions are drastically retarded in the presence of protons and Br promoter. A plausible reaction mechanism has been proposed for illustrating the role of the protons and Br promoter in the selective formation of H2O2 in the O-2 reduction process. (C) 2007 Elsevier B.V. All rights reserved.</p>10abrominated Pd/Al2O3 catalyst10ahydrazine sulfate10aHydrogen peroxide10ain situ H2O2 generation10aoxygen reduction10aPd/Al2O3 catalyst1 aChoudhary, Vasant, R.1 aJana, Prabhas1 aSamanta, Chanchal  uhttp://library.ncl.res.in/content/generation-hydrogen-peroxide-selective-reduction-oxygen-hydrazine-sulfate-over-br-promoted02257nas a2200229   4500008004100000022001400041245016000055210006900215260007300284300001100357490000800368520134900376653002101725653002201746653001801768653002901786653002201815653002101837100002601858700001801884856012501902       2008                        eng d  a0926-860X00aFactors influencing the in situ generation of hydrogen peroxide from the reduction of oxygen by hydroxylamine from hydroxylammonium sulfate over Pd/alumina0 aFactors influencing the in situ generation of hydrogen peroxide   aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcFEB  a95-1020 v3353 a<p>Influence of the concentration of bromide (KBr) promoter, reaction period, temperature, catalyst loading and initial concentration of hydroxylammonium sulfate on the formation of H2O2 due to the reaction between hydroxylamine from the hydroxylammonium salt and molecular oxygen over Pd (1 wt%)/Al2O3 catalyst in a neutral aqueous medium at close to the ambient conditions has been investigated. Effect of pH and temperature on the destruction of H2O2, Occurring in the consecutive reactions, over the catalyst in the presence or absence of bromide promoter and hydroxylamine has also been studied. In the absence of O-2, the conversion of hydroxylamine by its decomposition over the catalyst increases sharply with increasing the pH, particularly above the pH of 7.0; at or below the pH of 7.0, it is quite small. The H2O2 destruction increases markedly with increasing the pH of medium and reaction temperature but it is found to decrease in the presence of hydroxylamine. For the highest net H2O2 formation, not only the optimum pH (7.0) of reaction medium but also the optimum other reaction conditions (viz. bromide promoter concentration, reaction period, temperature or catalyst loading) are necessary. The reaction path and mechanism for the generation of H2O2 have also been suggested. (C) 2007 Elsevier B.V. All rights reserved.</p>10aH2O2 destruction10aHydrogen peroxide10ahydroxylamine10aHydroxylammonium sulfate10aPd/Al2O3 catalyst10areduction of O-21 aChoudhary, Vasant, R.1 aJana, Prabhas  uhttp://library.ncl.res.in/content/factors-influencing-situ-generation-hydrogen-peroxide-reduction-oxygen-hydroxylamine-0