02262nas a2200253 4500008004100000022001400041245011900055210006900174260007300243300001200316490000800328520135700336653001801693653002101711653000901732653002001741653002001761653001701781653001301798100002601811700001601837700002601853856012901879 2006 eng d a0926-860X00aDirect oxidation of H-2 to H2O2 over Pd-based catalysts: influence of oxidation state, support and metal additives0 aDirect oxidation of H2 to H2O2 over Pdbased catalysts influence  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUL a128-1330 v3083 a

The influence of oxidation state (reduced and oxidized), support (ZrO2, Ga2O3, CeO2, SiO2, H-beta, ThO2, CeO2-ZrO2, BPO4 and Pd/Al2O3) and precious metal additives (Au, Pt, Rh and Ru) on the direct H2O2 synthesis has been investigated over Pd-based catalysts. For all the supports investigated herein, the oxidized Pd catalysts showed significantly superior H2O2 yields as compared to their reduced counterparts. The effect of the Pd oxidation state was found to be more important for determining the H2O2 yields than the particle size and surface area properties of the catalyst system. An excellent correlation was observed between the H2O2 selectivity and H2O2 decomposition activity of the oxidized Pd catalysts. The oxidized Pd catalysts showed almost an order of magnitude lower H2O2 decomposition activity than the reduced catalysts. The H2O2 yield in the H-2 to H2O2 oxidation passed through a maximum with increase in the An concentration. Although a similar effect was also observed in case of Pt, Au was found to be a superior promoter for the direct H2O2 synthesis process. Addition of Rh and Ru was found to be detrimental for the H2O2 yields; these results can be explained in terms of increased H2O2 decomposition activity and/or enhanced H-2 to H2O reaction activity in their presence. (c) 2006 Elsevier B.V. All rights reserved.

10adecomposition10adirect synthesis10aH2O210ametal additives10aoxidation state10aPd catalysts10asupports1 aChoudhary, Vasant, R.1 aSamanta, C.1 aChoudhary, Tushar, V. uhttps://library.ncl.res.in/content/direct-oxidation-h-2-h2o2-over-pd-based-catalysts-influence-oxidation-state-support-and-002597nas a2200229 4500008004100000022001400041245017300055210006900228260007300297300001000370490000800380520164400388653002602032653005202058653002202110653002602132653001302158100002602171700002202197700001802219856013002237 2007 eng d a0926-860X00aDecomposition and/or hydrogenation of hydrogen peroxide over Pd/Al2O3 catalyst in aqueous medium: factors affecting the rate of H2O2 destruction in presence of hydrogen0 aDecomposition andor hydrogenation of hydrogen peroxide over PdAl aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcNOV a70-780 v3323 a

Hydrogen peroxide destruction by its decomposition and/or hydrogenation to water in the presence of H-2 over Pd(5 wt.%)/Al2O3 catalyst in an aqueous reaction medium, similar to that used in the H-2-to-H2O2 oxidation, has been thoroughly investigated at different reaction conditions. The H2O2 destruction is strongly influenced by the oxidation state of Pd in the catalyst and also by the presence of different halide anions (viz. F-, Cl-, Br- and I-) in the acidic aqueous medium or in the catalyst, depending upon the concentration of halide anions. The cations associated with halide anions have, however, a little or no influence on the H2O2 destruction. The iodide anions strongly poisoned the catalyst, even at their very low concentration. The fluoride anions have only a small effect on the H2O2 destruction. The chloride or bromide anions drastically inhibit the rapid H2O2 decomposition, but promote the slower H2O2 hydrogenation. The H2O2 destruction reactions are strongly influenced by the halide anion and acid concentrations. The presence of acid (protons) plays a very important role in drastically reducing the H2O2 destruction, particularly in the presence of chloride anions. Both in the presence and absence of Cl- or Br- anions, the H2O2 destruction activity of the catalyst is markedly reduced because of the oxidation of Pd but it is drastically increased due to the presence of H-2. A plausible reaction mechanism for the rapid H2O2 decomposition and slower H2O2 hydrogenation reactions, prevailing under the different reaction conditions, has also been discussed. (C) 2007 Elsevier B.V. All rights reserved.

10adecomposition of H2O210ahalide anions as catalyst promoter or indicator10aHydrogen peroxide10ahydrogenation of H2O210aPd/Al2O31 aChoudhary, Vasant, R.1 aSamanta, Chanchal1 aJana, Prabhas uhttps://library.ncl.res.in/content/decomposition-andor-hydrogenation-hydrogen-peroxide-over-pdal2o3-catalyst-aqueous-medium-002189nas a2200205 4500008004100000022001400041245016800055210006900223260007300292300001400365490000600379520132800385653002601713653002601739653002301765653002101788100002201809700002601831856012601857 2007 eng d a1566-736700aDirect formation of H2O2 from H-2 and O-2 and decomposition/hydrogenation of H2O2 in aqueous acidic reaction medium over halide-containing Pd/SiO2 catalytic system0 aDirect formation of H2O2 from H2 and O2 and decompositionhydroge aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcDEC a2222-22280 v83 a

Formation of H2O2 from H-2 and O-2 and decomposition/hydrogenation of H2O2 have been studied in aqueous acidic medium over Pd/SiO2 catalyst in presence of different halide ions (viz. F-, Cl- and Br-). The halide ions were introduced in the catalytic system via incorporating them in the catalyst or by adding into the reaction medium. The nature of the halide ions present in the catalytic system showed profound influence on the H2O2 formation selectivity in the H-2 to H2O2 oxidation over the catalyst. The H2O2 destruction via catalytic decomposition and by hydrogenation (in presence of hydrogen) was also found to be strongly dependent upon the nature of the halide ions present in the catalytic system. Among the different halides, Br- was found to selectivity promote the conversion of H-2 to H2O2 by significantly reducing the H2O2 decomposition and hydrogenation over the catalyst. The other halides, on the other hand, showed a negative influence on the H2O2 formation by promoting the H-2 combustion to water and/or by increasing the rate of decomposition/hydrogenation of H2O2 over the catalyst. An optimum concentration of Br- ions in the reaction medium or in the catalyst was found to be crucial for obtaining the higher H2O2, yield in the direct synthesis. (c) 2007 Elsevier B.V. All rights reserved.

10aBr- catalyst promoter10adirect H2O2 formation10aH2O2 decomposition10aPd/SiO2 catalyst1 aSamanta, Chanchal1 aChoudhary, Vasant, R. uhttps://library.ncl.res.in/content/direct-formation-h2o2-h-2-and-o-2-and-decompositionhydrogenation-h2o2-aqueous-acidic-002462nas a2200205 4500008004100000022001400041245025900055210006900314260007300383300001000456490000800466520149200474653003101966653002201997653002902019653003402048100002602082700001802108856013002126 2007 eng d a0926-860X00aDirect oxidation of H-2 to H2O2 over Br and F-promoted Pd/Al2O3 in aqueous acidic medium: influence of the concentration of Br and F and the method of incorporation of the two halogens in the catalyst on their beneficial synergetic effect on the net H2O20 aDirect oxidation of H2 to H2O2 over Br and Fpromoted PdAl2O3 in  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcOCT a79-850 v3293 a

Influence of the addition of F (0-1.1 mmol/g) in the pre-brominated Pd/Al2O3 (Br loading = 0.13 mmol/g) and also that of Br (0.13 mmol/g) in the pre-fluorinated Pd/Al2O3 (F loading = 0.53 mmol/g) on the net H2O2 formation in the H-2-to-H2O2 oxidation (with H-2/O-2 mole ratio of 1.0) over the halogenated catalysts in aqueous acidic (0.1 M H3PO4) medium have been investigated. In both the cases, the highest synergetic effect (resulting in the highest net H2O2 formation) produced by the addition of other halogen is observed at its optimum concentration (viz. 0.13 mmol Br/g in the fluorinated Pd/Al2O3 and 0.13 mmol F/g in the pre-brominated Pd/Al2O3). The beneficial synergetic effect of the two halogens is also found to be strongly influenced by the way of incorporation of the two halogens in the catalyst. The enhancement in the net rate of H2O2 formation due to the synergetic effect for the different methods of Pd/Al2O3 halogenation is in the following order: simultaneous bromination and fluorination < first fluorination and then bromination < first bromination and then fluorination. The fluorination (at optimum concentration of 0.13 mmol F/g) of the pre-brominated (0.13 mmol Br/g) Pd/Al2O3 led to the best catalyst for the H-2-to-H2O2 oxidation with 100% H-2 conversion and 78% H2O2 yield/selectivity. The destruction of H2O2 by its decomposition and/or hydrogenation over the halogenated catalysts has also been studied. (c) 2007 Published by Elsevier B.V.

10aF and Br-promoted Pd/Al2O310aHydrogen peroxide10aoxidation of H-2-to-H2O210asynergetic effect of F and Br1 aChoudhary, Vasant, R.1 aJana, Prabhas uhttps://library.ncl.res.in/content/direct-oxidation-h-2-h2o2-over-br-and-f-promoted-pdal2o3-aqueous-acidic-medium-influence-002768nas a2200181 4500008004100000022001400041245020800055210006900263260007100332300001400403490000700417520194400424100002602368700002302394700002202417700001802439856012902457 2007 eng d a0888-588500aDirect oxidation of hydrogen to hydrogen peroxide over Pd (or PdO)/Al2O3 in aqueous reaction medium: influence of different acids and halide anions in reaction medium on formation and destruction of H2O20 aDirect oxidation of hydrogen to hydrogen peroxide over Pd or PdO a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC a8566-85730 v463 a

Effects of different mineral acids (viz. H2SO4, H3PO4, HNO3, HCl, HBr, and HI), acid (H3PO4) concentration, different halide anions (viz. F-, Cl-, Br-, and I-), and halide anion concentration in aqueous reaction medium on the H2O2 formation (in H-2-to-H2O2 oxidation) and/or on the H2O2 destruction (by H2O2 decomposition and hydrogenation) activities of Pd (or PdO)/Al2O3 catalyst (at 300 K and atmospheric pressure) have been thoroughly investigated. Among the different halide anions, Br- anions are most effective for promoting the H2O2 formation and inhibiting the H2O2 destruction by both the H2O2 decomposition and/or hydrogenation. The cations associated with the halide anions, however, have only a little or no influence on both the H2O2 formation and destruction. The concentration of the different halide anions has a strong influence on the H-2 conversion and H2O2 formation and destruction activities of the Pd/Al2O3. The H2O2 formation activity in the presence of Br- or Cl- anions is highest at the optimum concentration of halide (about 1.0 mmol/dm(3)). it is also highest at the optimum concentration of phosphoric acid (between 0.1 and 0.3 mol/dm(3)). In general, the H2O2 formation is increased with decreasing the H2O2 destruction activity of the catalyst, indicating a close relationship between the two. Br- anions act as an excellent catalyst promoter for Pd/Al2O3 catalyst, but they show only a small promoting effect for PdO/Al2O3 catalyst. The next choice for halide promoter for Pd/Al2O3 catalyst is Cl- anions. F- and I- anions are, however, catalyst inhibitor and strong poison, respectively, for the H2O2 formation. At the same concentration, Br- anions are more effective than Cl- anions for inhibiting the H2O2 destruction reactions over Pd/Al2O3 Catalyst. For both halide promoters (Cl- and Br-), the net H2O2 formation is controlled by the H2O2 hydrogenation rather than by the H2O2 decomposition.

1 aChoudhary, Vasant, R.1 aIngole, Yugesh, V.1 aSamanta, Chanchal1 aJana, Prabhas uhttps://library.ncl.res.in/content/direct-oxidation-hydrogen-hydrogen-peroxide-over-pd-or-pdoal2o3-aqueous-reaction-medium-002367nas a2200217 4500008004100000022001400041245018500055210006900240260007300309300001000382490000600392520143600398653002601834653003001860653002301890653002301913653003701936100002201973700002601995856012802021 2007 eng d a1566-736700aDirect synthesis of H2O2 from H-2 and O-2 over Pd/H-beta catalyst in an aqueous acidic medium: influence of halide ions present in the catalyst or reaction medium on H2O2 formation0 aDirect synthesis of H2O2 from H2 and O2 over PdHbeta catalyst in aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJAN a73-790 v83 a

The influence of different halide ions present in the catalyst or reaction medium on the performance of Pd/H-beta catalyst in the direct H2O2 synthesis in an aqueous acidic (0.03 M H3PO4) reaction medium at 27 degrees C and atmospheric pressure has been thoroughly investigated. The results showed a strong influence of both the bulk Pd oxidation state in the catalyst and the halide ions added to the reaction medium on the performance of the catalyst in the H-2 to H2O2 oxidation, H2O2 decomposition/hydrogenation reactions. The different ammonium halides impregnated reduced Pd/H-beta catalyst calcined in inert (N-2) and oxidizing (air) gaseous atmospheres also revealed that the bulk Pd oxidation state and nature of the halide ions present in the catalyst together control the overall performance of the catalyst in the H2O2 formation reaction. The presence of halide ions in reaction medium or in the catalyst significantly changes the selectivity for H2O2 formation in the direct H2O2 synthesis. Bromide ions are found to remarkably enhance the H2O2 selectivity in the direct H2O2 synthesis irrespective of the Pd oxidation state in the catalyst. The promoting action of Br- is attributed mainly to the large decrease in the H2O2 decomposition and hydrogenation activities of the catalyst and also inhibition for the non-selective H-2-to-water oxidation over the catalyst. (c) 2006 Elsevier B.V. All rights reserved.

10adirect H2O2 synthesis10aH-P supported Pd catalyst10aH2O2 decomposition10aH2O2 hydrogenation10apromoting action of bromide ions1 aSamanta, Chanchal1 aChoudhary, Vasant, R. uhttps://library.ncl.res.in/content/direct-synthesis-h2o2-h-2-and-o-2-over-pdh-beta-catalyst-aqueous-acidic-medium-influence02755nas a2200217 4500008004100000022001400041245015600055210006900211260007300280300001000353490000800363520186800371653002602239653002302265653002302288653002402311653002302335100002202358700002602380856013102406 2007 eng d a0926-860X00aDirect synthesis of H2O2 from H-2 andO(2) and decomposition/hydrogenation of H2O2 in an aqueous acidic medium over halide-modified Pd/Al(2)O3 catalysts0 aDirect synthesis of H2O2 from H2 andO2 and decompositionhydrogen aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcOCT a23-320 v3303 a

Direct synthesis Of H2O2 from its elements was carried out in an acidic aqueous reaction medium over halide-modified oxidized and reduced Pd/ Al2O3 catalysts under very mild conditions (at 27 degrees C and atmospheric pressure). The halide ions were introduced into the catalyst by incorporating halide ions into supported Pd/gamma-Al2O3 catalyst or via depositing halide ions on the support (gamma-Al2O3) prior to Pd deposition. The H2O2 decomposition and hydrogenation over the corresponding catalysts were also carried out under the reaction conditions similar to those employed for the H2O2 synthesis in order to elucidate the factors strongly affecting the H2O2 yield/selectivity in the direct H2O2 process. The performance of halide-modified Pd/Al2O3 catalysts in the direct H2O2 synthesis revealed that halide insertion in the catalyst system prior to or after Pd deposition on the support had comparable qualitative effect on the H2O2 formation. Both the Pd oxidation state and the nature of the halide ions had strong influences on the H-2 conversion (in direct H2O2 Synthesis process) and H2O2 decomposition and/or hydrogenation reaction. While the effect of Pd oxidation state on the H2O2 formation was significant for the catalytic system containing F- and Cl- ions, the influence of the Pd oxidation state was found less important for the catalyst system containing Br- ions; the H2O2 formation selectivity increased significantly due to the presence of Br- ions, irrespective of the Pd oxidation state. The nature of the H2O2 destruction pathway (i.e. hydrogenation and/or decomposition) in the presence of hydrogen over halide-modified Pd/Al2O3 catalysts was found to be strongly dependent upon the nature of the halide ions incorporated in the catalyst during halide-modification of the catalyst. (C) 2007 Elsevier B.V. All rights reserved.

10adirect H2O2 synthesis10aH2O2 decomposition10aH2O2 hydrogenation10ahalide-modification10aPd oxidation state1 aSamanta, Chanchal1 aChoudhary, Vasant, R. uhttps://library.ncl.res.in/content/direct-synthesis-h2o2-h-2-ando2-and-decompositionhydrogenation-h2o2-aqueous-acidic-medium-001701nas a2200217 4500008004100000022001400041245017100055210006900226260005700295300001200352490000800364520082500372653002201197653003401219653001701253653000901270100002601279700001801305700002801323856013201351 2008 eng d a1011-372X00aDirect H(2)-to-H(2)O(2) oxidation in aqueous acidic medium containing Br promoter over Pd/Al(2)O(3) and Pd/C catalysts thermally pretreated under different conditions0 aDirect H2toH2O2 oxidation in aqueous acidic medium containing Br a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcOCT a296-3010 v1253 a

Influence of thermal pretreatments (under N(2), air or H(2) gas atmosphere at 500 degrees C or 700 degrees C) has been investigated for the Pd/Al(2)O(3) and Pd/Carbon catalysts in terms of its effect on their Pd particle size and performance in the H(2)-to-H(2)O(2) oxidation and H(2)O(2) destruction (by decomposition and/or hydrogenation) reactions in aqueous acidic medium containing Br promoter. The influence on the net H(2)O(2) formation is found to depend strongly upon the catalyst support due to support-Pd cluster interactions. For both the catalysts, the thermal treatments (except in air) caused a large increase in their Pd particle size. The increase in Pd particle size caused an increase in the H(2)O(2) formation activity of Pd/Al(2)O(3) but a decrease in the H(2)O(2) formation activity of Pd/C.

10aHydrogen peroxide10aoxidation of H(2) to H(2)O(2)10aPd/Al(2)O(3)10aPd/C1 aChoudhary, Vasant, R.1 aJana, Prabhas1 aBhargava, Suresh, Kumar uhttps://library.ncl.res.in/content/direct-h2-h2o2-oxidation-aqueous-acidic-medium-containing-br-promoter-over-pdal2o3-and-pdc-002048nas a2200193 4500008004100000022001400041245021600055210006900271260007300340300001400413490000600427520117000433653002201603653002901625653002801654100002601682700001801708856012801726 2008 eng d a1566-736700aDirect oxidation of H-2 to H2O2 over different supported PdO catalysts in aqueous acidic medium: Influence of the reduction, calcination temperature and support of the catalyst on its net H2O2 formation activity0 aDirect oxidation of H2 to H2O2 over different supported PdO cata aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAPR a1624-16290 v93 a

Effects of the catalyst reduction (by hydrazine), calcination temperature (400-800 degrees C) and support (viz. Al2O3, SiO2, CeO2, ZrO2, HP or HM) on the performance of supported PdO (2.5 wt%) catalyst in the H-2-to-H2O2 oxidation (with H-2:O-2 = 1: 1) in an aqueous acidic (0.1 M H3PO4) medium under ambient conditions have been investigated. All the supported PdO catalysts showed lower H2 conversion activity, but higher H2O2 selectivity, as compared to their reduced counter parts. The catalyst performance for the net H2O2 formation is strongly influenced by both the support and calcination temperature of the supported PdO catalysts. The catalysts calcined at 400 degrees C showed better performance. Among the catalysts, PdO/Al2O3 catalyst (calcined at 400 degrees C) showed the best performance (17.0% H2O2 yield) in the H-2-to-H2O2 oxidation. The influence of the calcination temperature of PdO/Al2O3 catalyst on its H2O2 decomposition and hydrogenation activities has also been investigated. Both the H2O2 decomposition and hydrogenation activities increased with increasing the calcination temperature. (C) 2008 Elsevier B.V. All rights reserved.

10aHydrogen peroxide10aoxidation of H-2 to H2O210asupported PdO catalysts1 aChoudhary, Vasant, R.1 aJana, Prabhas uhttps://library.ncl.res.in/content/direct-oxidation-h-2-h2o2-over-different-supported-pdo-catalysts-aqueous-acidic-medium-002138nas a2200217 4500008004100000022001400041245010900055210006900164260006900233300001200302490000800314520131400322653001301636653002601649653002301675653002301698653002101721100002201742700002601764856013001790 2008 eng d a1385-894700aDirect oxidation of H-2 to H2O2 over Pd/CeO2 catalyst under ambient conditions: influence of halide ions0 aDirect oxidation of H2 to H2O2 over PdCeO2 catalyst under ambien aPO BOX 564, 1001 LAUSANNE, SWITZERLANDbELSEVIER SCIENCE SAcMAR a126-1320 v1363 a

Direct oxidation of H-2 by O-2 to H2O2 and decomposition/hydrogenation of H2O2 have been investigated over Pd/CeO2 catalyst in presence of different halide ions. All reactions were carried out in an aqueous acidic (0.03 M H3PO4) medium at room temperature (25 degrees C) and atmospheric pressure. When different halide ions were added directly to the reaction medium or incorporated in the catalyst, the activity/selectivity of Pd/CeO2 catalyst in the H-2 to H2O2 oxidation changed significantly, depending upon the nature of the halide ions. Different ammonium halides impregnated reduced Pd/CeO2 catalyst calcined under inert (flowing nitrogen) and oxidizing (static/flowing air) gaseous atmospheres revealed that bulk oxidation state of Pd and the nature of the halide ions incorporated into the catalyst cooperatively control the activity/selectivity of catalyst in H-2 to H2O2 oxidation. Both H2O2 decomposition and hydrogenation were found to affect strongly depending upon the nature of the halide ions present in the reaction medium or in the catalyst. Among the different halides, bromide was found the most effective promoter for enhancing the H2O2 yield/selectivity in H-2 to H2O2 oxidation, irrespective of the Pd oxidation state in the catalyst. (c) 2007 Elsevier B.V. All rights reserved.

10aBr- ions10aH-2 to H2O2 oxidation10aH2O2 decomposition10aH2O2 hydrogenation10aPd/CeO2 catalyst1 aSamanta, Chanchal1 aChoudhary, Vasant, R. uhttps://library.ncl.res.in/content/direct-oxidation-h-2-h2o2-over-pdceo2-catalyst-under-ambient-conditions-influence-halide-001585nas a2200217 4500008004100000022001400041245021000055210006900265260007300334300001400407490000600421520066000427653003001087653002201117653002901139653001301168653001401181100002601195700001801221856012801239 2008 eng d a1566-736700aDirect oxidation of H-2 to H2O2 over PdO/Al2O3 catalysts in aqueous acidic medium: influence on H2O2 formation of Pd loading, calcination temperature and reduction of catalyst and presence of halide anions0 aDirect oxidation of H2 to H2O2 over PdOAl2O3 catalysts in aqueou aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG a2371-23750 v93 a

Effects of the Pd loading (0.2-10 wt%), calcination temperature (400-900 degrees C) and reduction of PdO/Al2O3 on its performance in the H-2-to-H2O2 oxidation (with H-2/O-2 = 1:1) in an aqueous 0.1 M H3PO4 medium, in the absence and presence of different halide anions, under ambient conditions have been investigated. The effect of calcination temperature on the H2O2 formation varied depending upon the Pd loading. The influence of the different halide anions was found to depend strongly on the nature of halide anion (F-, Cl-, Br- or I-) and the oxidation state of Pd and its loading in the catalyst. (C) 2008 Elsevier B.V. All rights reserved.

10ahalide catalyst promoters10aHydrogen peroxide10aoxidation of H-2 to H2O210aPd/Al2O310aPdO/Al2O31 aChoudhary, Vasant, R.1 aJana, Prabhas uhttps://library.ncl.res.in/content/direct-oxidation-h-2-h2o2-over-pdoal2o3-catalysts-aqueous-acidic-medium-influence-h2o2-002497nas a2200217 4500008004100000022001400041245016500055210006900220260007300289300001000362490000800372520160500380653002701985653002302012653002302035653002302058653002202081100002602103700001802129856013202147 2009 eng d a0926-860X00aDirect H-2-to-H2O2 oxidation over highly active/selective Br-F-Pd/Al2O3 catalyst in aqueous acidic medium: Influence of process conditions on the H2O2 formation0 aDirect H2toH2O2 oxidation over highly activeselective BrFPdAl2O3 aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJAN a35-420 v3523 a

The influence of the O-2/H-2 mote ratio in the gaseous feed and also those of other reaction conditions [viz. concentration of H3PO4 (0-5 mol/dm(3)). temperature (5-50 degrees C, gas (H-2 and O-2) space velocity (5.8-23.4 h(-1)) and reaction time (0.1-8 h)] on the H2O2 formation in the H-2-to-H2O2 oxidation over the Br(1 wt%)-F(1 wt%)-Pd(5 wt%)/Al2O3 catalyst in an aqueous acidic (H3PO4) medium have been thoroughly investigated. The effects of the O-2/H-2 ratio, reaction temperature and acid concentration on the destruction of H2O2 by its decomposition and/or hydrogenation reactions over the catalyst in the acidic reaction medium have also been studied. The net H2O2 formation (H2O2 yield) over the catalyst passed through a maximum with increasing the acid concentration, the temperature or the O-2/H-2 feed ratio. However, it decreased markedly with increasing the gas space velocity or the reaction period. The H2O2 decomposition and hydrogenation activities of the catalyst increased appreciably with increasing the reaction temperature and decreased with increasing the acid concentration. The H2O2 destruction during the H-2-to-H2O2 oxidation increased with increasing the concentration of H-2 (relative to that of O-2) due to the increased H2O2 hydrogenation rate over the catalyst. The net H2O2 formation in the H-2-to-H2O2 oxidation decreased sharply with increasing the initial amount of H2O2 present in the reaction mixture. The presence of H2O2 and the higher H-2/O-2 ratios have detrimental effects on the net formation of H2O2. (C) 2008 Elsevier B.V. All rights reserved.

10aBr-F-Pd/Al2O3 catalyst10aH2O2 decomposition10aH2O2 hydrogenation10ahydrogen oxidation10aHydrogen peroxide1 aChoudhary, Vasant, R.1 aJana, Prabhas uhttps://library.ncl.res.in/content/direct-h-2-h2o2-oxidation-over-highly-activeselective-br-f-pdal2o3-catalyst-aqueous-acidic-0