Zirconium Oxides

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform

Pierre Gallezot - One of the best experts on this subject based on the ideXlab platform.

  • degradation of olive oil mill effluents by catalytic wet air oxidation 2 oxidation of p hydroxyphenylacetic and p hydroxybenzoic acids over pt and ru supported catalysts
    Applied Catalysis B-environmental, 2007
    Co-Authors: Pham D Minh, Pierre Gallezot, G Aubert, Michele Besson
    Abstract:

    Abstract Catalytic wet air oxidation of p -hydroxyphenylacetic acid and p -hydroxybenzoic acid, two important pollutants present in the olive oil mill wastewaters, was studied in a batch reactor using platinum and ruthenium catalysts supported on titanium and Zirconium Oxides at 140 °C and 50 bar of total air pressure. Reaction pathways for the oxidation of these two substrates were proposed, with formation of different aromatic compounds and short-chain organic acids through hydroxylation and decarboxylation reactions. It was observed that the conversion and the mineralization of these two substrates were markedly affected by the nature of the ruthenium precursor (RuCl 3 or Ru(NO)(NO 3 ) 3 ), with the non-chlorine containing salt giving the best performances. Calcination of the catalyst precursor before reduction was detrimental. The nature of the metallic precursor (H 2 PtCl 6 or Pt(NH 3 ) 4 (NO 3 ) 2 ) had little influence on the catalytic properties of platinum catalysts, whereas the textural properties of the support were an important factor.

  • Platinum and ruthenium catalysts on mesoporous titanium and Zirconium Oxides for the catalytic wet air oxidation of model compounds
    Applied Catalysis B: Environmental, 2005
    Co-Authors: N. Perkas, Pierre Gallezot, Doan Pham Minh, A. Gedanken, M. Besson
    Abstract:

    Pt and Ru catalysts on mesoporous (MSP) TiO2 and ZrO2 were developed using sonochemical irradiation. The catalysts were characterized by XRD, TEM, HR TEM, EDX, and BET methods. The high homogeneity of the active metal phase was confirmed by electron microscopy. The catalysts were examined for the removal of organic pollutants from model wastewaters using the wet air oxidation (WAO) process of acetic, succinic and p-coumaric acids in an autoclave reactor at 140 and 190 °C and 50 bar total air pressure. The high activity and stability of Pt supported on a TiO2 (MSP) catalyst in the removal of succinic and p-coumaric acids, and intermediates of their oxidation was demonstrated. The catalytic performances of Ru/TiO2 (MSP) were similar to those of the catalysts prepared by incipient-wetness impregnation of commercial TiO2 supports.

  • catalytic wet air oxidation of kraft bleaching plant effluents in the presence of titania and zirconia supported ruthenium
    Applied Catalysis B-environmental, 2001
    Co-Authors: Albin Pintar, Michele Besson, Pierre Gallezot
    Abstract:

    Abstract The wet air oxidation (WAO) of two acidic and alkaline Kraft bleaching plant effluents (total organic carbon (TOC) content 665 and 1380 mg l −1 , respectively) has been investigated in a batch slurry reactor in the presence of titanium or Zirconium Oxides, or ruthenium catalysts supported on these Oxides. At 463 K and 5.5 MPa total air pressure, a drastic extent of TOC removal was observed with addition of the Oxides (up to 88 and 79%, respectively). The rate of TOC decrease was not influenced by the nature and structure of the Oxides nor by the acidic/basic character of the surface, but it was found to increase with the specific surface area of the Oxides. The rate of TOC removal was further enhanced by deposition of metallic ruthenium on the Oxides. In that case, the treatment produced decolorised liquid effluents, with very low TOC values (TOC removal >99.7%), constituted of traces of acetic acid. No leaching of Ru, Ti or Zr was detected by ICP–AES analysis to the detection limits of 0.2, 0.1 and 0.1 mg l −1 , respectively. The quality of water obtained may allow its recycling in the process.

Kenichiro Ota - One of the best experts on this subject based on the ideXlab platform.

  • influence of sputtering power on oxygen reduction reaction activity of Zirconium Oxides prepared by radio frequency reactive sputtering
    Electrochimica Acta, 2010
    Co-Authors: Yan Liu, Akimitsu Ishihara, Shigenori Mitsushima, Kenichiro Ota
    Abstract:

    Abstract Zirconium Oxides (ZrO 2− x ) have been investigated as new cathodes for direct methanol fuel cells without platinum. ZrO 2− x films were prepared using a radio frequency (RF) magnetron sputtering at RF powers from 75 to 175 W. The influence of the RF power on the catalytic activity for the oxygen reduction reaction (ORR) and properties of the ZrO 2− x films were examined. The ORR activity of the ZrO 2− x catalyst increased with the RF power in the range we studied. The onset potential for ORR over ZrO 2− x deposited at 175 W was 0.88 V vs RHE. In addition, the relationship between the ORR activity and the composition, crystallinity, electric conductivity, as well as the ionization potential has been investigated. The Zirconium oxide with an oxygen defected state and the higher electric conductivity showed the higher ORR activity, and the electrocatalytic activity for ORR increased with the decreasing in the ionization potential of the ZrO 2− x catalyst.

  • transition metal Oxides as dmfc cathodes without platinum
    Journal of The Electrochemical Society, 2007
    Co-Authors: Yan Liu, Akimitsu Ishihara, Shigenori Mitsushima, Nobuyuki Kamiya, Kenichiro Ota
    Abstract:

    Transition metal Oxides (ZrO 2 , TiO 2 , SnO 2 , Nb 2 O 5 , and Co 3 O 4 ) made by sputtering methods were investigated as new electrocatalysts for the cathode of a direct methanol fuel cell (DMFC) without platinum. The catalytic activity for the oxygen reduction of these transition metal Oxides was evaluated in sulfuric acid with and without 0.1 M methanol. The sputtered metal Oxides had stable states in acid medium at least in the potential range of the oxygen reduction. The metal Oxides were not active for the methanol oxidation. The oxygen reduction activity of the metal Oxides decreased in the following order: ZrO 2-x > Co 3 O 4-x > TiO 2-x ≈ SnO 2-x > Nb 2 O 5-x in the presence of methanol. Zirconium Oxides showed the best activity for the oxygen reduction among these transition metal Oxides. Moreover, in comparison with the sputtered Pt, the potential at i O2-N2 = -5 μA cm -2 of ZrO 2-x was 60 mV larger than that of the sputtered Pt. This is due to the high selectivity of the metal Oxides for the oxygen reduction. The mixed potential as found on the Pt electrode was not observed on the metal oxide catalysts. Zirconium Oxides could be a good cathode substituting the platinum cathode for DMFCs.

Yan Liu - One of the best experts on this subject based on the ideXlab platform.

  • influence of sputtering power on oxygen reduction reaction activity of Zirconium Oxides prepared by radio frequency reactive sputtering
    Electrochimica Acta, 2010
    Co-Authors: Yan Liu, Akimitsu Ishihara, Shigenori Mitsushima, Kenichiro Ota
    Abstract:

    Abstract Zirconium Oxides (ZrO 2− x ) have been investigated as new cathodes for direct methanol fuel cells without platinum. ZrO 2− x films were prepared using a radio frequency (RF) magnetron sputtering at RF powers from 75 to 175 W. The influence of the RF power on the catalytic activity for the oxygen reduction reaction (ORR) and properties of the ZrO 2− x films were examined. The ORR activity of the ZrO 2− x catalyst increased with the RF power in the range we studied. The onset potential for ORR over ZrO 2− x deposited at 175 W was 0.88 V vs RHE. In addition, the relationship between the ORR activity and the composition, crystallinity, electric conductivity, as well as the ionization potential has been investigated. The Zirconium oxide with an oxygen defected state and the higher electric conductivity showed the higher ORR activity, and the electrocatalytic activity for ORR increased with the decreasing in the ionization potential of the ZrO 2− x catalyst.

  • transition metal Oxides as dmfc cathodes without platinum
    Journal of The Electrochemical Society, 2007
    Co-Authors: Yan Liu, Akimitsu Ishihara, Shigenori Mitsushima, Nobuyuki Kamiya, Kenichiro Ota
    Abstract:

    Transition metal Oxides (ZrO 2 , TiO 2 , SnO 2 , Nb 2 O 5 , and Co 3 O 4 ) made by sputtering methods were investigated as new electrocatalysts for the cathode of a direct methanol fuel cell (DMFC) without platinum. The catalytic activity for the oxygen reduction of these transition metal Oxides was evaluated in sulfuric acid with and without 0.1 M methanol. The sputtered metal Oxides had stable states in acid medium at least in the potential range of the oxygen reduction. The metal Oxides were not active for the methanol oxidation. The oxygen reduction activity of the metal Oxides decreased in the following order: ZrO 2-x > Co 3 O 4-x > TiO 2-x ≈ SnO 2-x > Nb 2 O 5-x in the presence of methanol. Zirconium Oxides showed the best activity for the oxygen reduction among these transition metal Oxides. Moreover, in comparison with the sputtered Pt, the potential at i O2-N2 = -5 μA cm -2 of ZrO 2-x was 60 mV larger than that of the sputtered Pt. This is due to the high selectivity of the metal Oxides for the oxygen reduction. The mixed potential as found on the Pt electrode was not observed on the metal oxide catalysts. Zirconium Oxides could be a good cathode substituting the platinum cathode for DMFCs.

Kazushi Arata - One of the best experts on this subject based on the ideXlab platform.

  • biodiesel fuel production with solid superacid catalysis in fixed bed reactor under atmospheric pressure
    Catalysis Communications, 2004
    Co-Authors: Satoshi Furuta, Hiromi Matsuhashi, Kazushi Arata
    Abstract:

    Abstract Solid superacid catalysts of sulfated tin and Zirconium Oxides and tungstated zirconia are prepared and evaluated in the trans-esterification of soybean oil with methanol at 200–300 °C and the esterification of n -octanoic acid with methanol at 175–200 °C. Tungstated zirconia–alumina is a promising solid acid catalyst for the production of biodiesel fuels from soybean oil because of its high performance in the conversions over 90% for both of the esterifications.

  • catalytic action of sulfated tin oxide for etherification and esterification in comparison with sulfated zirconia
    Applied Catalysis A-general, 2004
    Co-Authors: Satoshi Furuta, Hiromi Matsuhashi, Kazushi Arata
    Abstract:

    Abstract Two highly active solid superacids of sulfated tin oxide were prepared, and their catalytic action was compared with that of sulfated zirconia. One was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl 4 and washed with aqueous ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcination. The other was prepared from meta -stannic acid following the above procedures. The latter material was higher than the former in catalytic activities for the etherification of methanol and esterification of n -octanoic acid with methanol, and both showed activities higher than those of sulfated zirconia for the reactions. TPD measurements using ammonia and pyridine as probes showed that most of the acid sites on the surface of sulfated tin oxide have high strength of acidity with a narrow distribution, indicating the steady adsorption of both probes up to 673 K. On the other hand, the acidity on sulfated zirconia was shown to be heterogeneous, covering a wide range of strength, the temperature range of desorption of the probes being 473–823 K. The acid strength was estimated by the heat of Ar adsorption to be 29.7–31.0 and 24.3 kJ mol −1 for the sulfated tin and Zirconium Oxides, respectively. Differences in activities between the two Sn materials were explained on the basis of their IR spectra.

Jeroen A Van Bokhoven - One of the best experts on this subject based on the ideXlab platform.

  • mesoporous cerium Zirconium Oxides modified with gold and copper synthesis characterization and performance in selective oxidation of glycerol
    RSC Advances, 2017
    Co-Authors: Piotr Kaminski, Maria Ziolek, Jeroen A Van Bokhoven
    Abstract:

    The main goal of this work was the synthesis of mesoporous ceria, zirconia and cerium–Zirconium Oxides, the application of these supports for the preparation of monometallic (copper or gold) and bimetallic (copper and gold) catalysts and characterisation of their performance in the oxidation of glycerol in basic aqueous solution in the presence of oxygen. The methods applied for the study included: adsorption/desorption of nitrogen, XRD, ICP-OES, XPS, UV-vis, STEM-EDXS, H2-TPR. The presence of the following species Au0, Auδ+, negatively charged gold Au− or Au0 in bimetallic particles, Cu+, Cu2+, Ce3+ and Ce4+, Zr4+ was confirmed and their content was found to depend on the catalyst composition. The interaction between gold and copper species in bimetallic samples caused the formation of the negative charge on gold and the increase of the amount of Cu+ cations on the catalyst surface. This feature and the higher gold dispersion gave rise to a significant increase in the catalytic activity in glycerol oxidation of bimetallic catalysts with respect to that of monometallic samples. The high selectivity to glyceric acid (GLA) is an important advantage of the bimetallic catalysts (copper–gold), especially those loaded on mixed cerium–Zirconium Oxides. The bimetallic catalysts were stable and in the second run of the reaction they almost did not change glycerol conversion and increased the selectivity to GLA. The texture parameters of the catalysts had also impact on the selectivity of the reaction: the lower the microporosity the higher the selectivity to GLA. The role of the support is the interaction with copper and gold active species and enhancement of the reagents' chemisorption and electron transfers.