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Title: Selective Oxidation of Glycerol over Carbon-Supported AuPd Catalysts

Abstract

Carbon-supported AuPd bimetallic nanoparticles were synthesized, characterized, and evaluated as catalysts in the aqueous-phase selective oxidation of glycerol. The bimetallic catalysts were synthesized by two different methods. The first method involved the deposition of Au onto the surface of 3-nm supported Pd particles by catalytic reduction of HAuCl{sub 4} in aqueous solution by H{sub 2}. The second method used the formation of a AuPd sol that was subsequently deposited onto a carbon support. Characterization of the catalysts using analytical transmission electron microscopy, H{sub 2} titration, and X-ray absorption spectroscopy at the Au L{sub III} and Pd K-edges confirmed that the first synthesis method successfully deposited Au onto the Pd particles. Results from the AuPd sol catalyst also revealed that Au was preferentially located on the surface. Measurement of glycerol oxidation rates (0.3 M glycerol, 0.6 M NaOH, 10 atm O{sub 2}, 333 K) in a semibatch reactor gave a turnover frequency (TOF) of 17 s{sup -1} for monometallic Au and 1 s{sup -1} for monometallic Pd, with Pd exhibiting a higher selectivity to glyceric acid. Although the activity of the bimetallic AuPd catalysts depended on the amount of Au present, none of them had a TOF greater than that ofmore » the monometallic Au catalyst. However, the AuPd catalysts had higher selectivity to glyceric acid compared with the monometallic Au. Because a physical mixture of monometallic Au and Pd catalysts also gave higher selectivity to glyceric acid, the Pd is proposed to catalyze the decomposition of the side product H{sub 2}O{sub 2} that is also formed over the Au but is detrimental to the selectivity toward glyceric acid.« less

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929926
Report Number(s):
BNL-80518-2008-JA
Journal ID: ISSN 0021-9517; JCTLA5; TRN: US200822%%937
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Catalysis; Journal Volume: 250; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; GLYCEROL; OXIDATION; CATALYTIC EFFECTS; GOLD; PALLADIUM; CATALYST SUPPORTS; CARBON; CATALYSTS; SYNTHESIS; CHEMICAL REACTION KINETICS; national synchrotron light source

Citation Formats

Ketchie,W., Murayama, M., and Davis, R. Selective Oxidation of Glycerol over Carbon-Supported AuPd Catalysts. United States: N. p., 2007. Web. doi:10.1016/j.jcat.2007.06.011.
Ketchie,W., Murayama, M., & Davis, R. Selective Oxidation of Glycerol over Carbon-Supported AuPd Catalysts. United States. doi:10.1016/j.jcat.2007.06.011.
Ketchie,W., Murayama, M., and Davis, R. Mon . "Selective Oxidation of Glycerol over Carbon-Supported AuPd Catalysts". United States. doi:10.1016/j.jcat.2007.06.011.
@article{osti_929926,
title = {Selective Oxidation of Glycerol over Carbon-Supported AuPd Catalysts},
author = {Ketchie,W. and Murayama, M. and Davis, R.},
abstractNote = {Carbon-supported AuPd bimetallic nanoparticles were synthesized, characterized, and evaluated as catalysts in the aqueous-phase selective oxidation of glycerol. The bimetallic catalysts were synthesized by two different methods. The first method involved the deposition of Au onto the surface of 3-nm supported Pd particles by catalytic reduction of HAuCl{sub 4} in aqueous solution by H{sub 2}. The second method used the formation of a AuPd sol that was subsequently deposited onto a carbon support. Characterization of the catalysts using analytical transmission electron microscopy, H{sub 2} titration, and X-ray absorption spectroscopy at the Au L{sub III} and Pd K-edges confirmed that the first synthesis method successfully deposited Au onto the Pd particles. Results from the AuPd sol catalyst also revealed that Au was preferentially located on the surface. Measurement of glycerol oxidation rates (0.3 M glycerol, 0.6 M NaOH, 10 atm O{sub 2}, 333 K) in a semibatch reactor gave a turnover frequency (TOF) of 17 s{sup -1} for monometallic Au and 1 s{sup -1} for monometallic Pd, with Pd exhibiting a higher selectivity to glyceric acid. Although the activity of the bimetallic AuPd catalysts depended on the amount of Au present, none of them had a TOF greater than that of the monometallic Au catalyst. However, the AuPd catalysts had higher selectivity to glyceric acid compared with the monometallic Au. Because a physical mixture of monometallic Au and Pd catalysts also gave higher selectivity to glyceric acid, the Pd is proposed to catalyze the decomposition of the side product H{sub 2}O{sub 2} that is also formed over the Au but is detrimental to the selectivity toward glyceric acid.},
doi = {10.1016/j.jcat.2007.06.011},
journal = {Journal of Catalysis},
number = 2,
volume = 250,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Gold particles supported on carbon and titania were explored as catalysts for oxidation of CO or glycerol by O{sub 2} at room temperature in liquid-phase water. Although Au/carbon catalysts were not active for vapor phase CO oxidation at room temperature, a turnover frequency of 5 s{sup -1} could be achieved with comparable CO concentration in aqueous solution containing 1 M NaOH. The turnover frequency on Au/carbon was a strong function of pH, decreasing by about a factor of 50 when the pH decreased from 14 to 0.3. Evidently, a catalytic oxidation route that was not available in the vapor phasemore » is enabled by operation in the liquid water at high pH. Since Au/titania is active for vapor phase CO oxidation, the role of water, and therefore hydroxyl concentration, is not as significant as that for Au/carbon. Hydrogen peroxide is also produced during CO oxidation over Au in liquid water and increasing the hydroxyl concentration enhances its formation rate. For glycerol oxidation to glyceric acid (C{sub 3}) and glycolic acid (C{sub 2}) with O{sub 2} (1-10 atm) at 308-333 K over supported Au particles, high pH is required for catalysis to occur. Similar to CO oxidation in liquid water, H{sub 2}O{sub 2} is also produced during glycerol oxidation at high pH. The formation of the C-C cleavage product glycolic acid is attributed to peroxide in the reaction.« less
  • Reaction kinetics measurements were carried out to study the conversion of aqueous solutions of glycerol (30 and 80 wt%) over carbon-supported Pt and Pt-Re catalysts at temperatures from 483 to 523 K. The results of these studies show that the turnover frequencies for production of H2, CO, CO2, and light alkanes (primarily methane) all increase upon the addition of Re to Pt/C catalysts. The molar ratio of H2/CO increases, while the CO/CO2 ratio decreases with Re addition, indicating increased rate of water-gas shift. For glycerol conversion over a Pt-Re/C catalyst with an atomic Pt:Re ratio of 1:1, increasing pressure ormore » decreasing temperature leads to an increase in the production of alkanes and light oxygenated hydrocarbons (ethanol, methanol, propanediols, and acetone) at the expense of CO and CO2. Temperature-programmed desorption studies and microcalorimetric measurements indicate that addition of Re to Pt modifies the interaction of CO with surface sites. X-ray absorption spectroscopy and transmission electron microscopy studies provide evidence indicating that Pt-Re/C catalysts consist primarily of bimetallic nanoparticles with sizes below 2 nm, and Re inhibits the sintering of these nanoparticles during reaction conditions for glycerol conversion. The results of these reaction kinetic studies and characterization studies indicate that the performance of Pt-Re/C catalysts for glycerol conversion is related to the formation of Pt-Re nanoparticles, for which Re promotes the overall rate of glycerol reforming by reducing the binding energy of CO to Pt, thereby leading to less extensive blocking of surface sites by reaction intermediates and/or products. In addition, the presence of Re facilitates water-gas shift and Csingle bondO bond cleavage reactions.« less
  • The selective oxidation of methane to C{sub 1} oxygenates in a single catalytic step on a MoO{sub 3} (< 1.7 wt%) catalyst on an Aerosol support was studied using a fixed-bed atmospheric pressure laboratory reactor with simultaneous CH{sub 4} and O{sub 2} feed in the molar proportion CH{sub 4}/O{sub 2} = 9:1 at 550--650 C. An increase in the reaction temperature increased the CH{sub 4} conversion and lowered the formaldehyde selectivity, but favored the formation of dimerization products. The catalysts were characterized by UV-visible diffuse reflectance spectroscopy (DRS), isothermal reduction with H{sub 2}, and X-ray photoelectron spectroscopy (XPS). The reflectancemore » spectra of the catalysts showed that Mo{sup 6+} ions with O{sub h} and T{sub d} symmetries coexisted, but that the relative proportion depended on the MoO{sub 3} loading. Independently of the coordination, the MoO{sub 3} essentially dispersed as a monolayer, as shown by the I{sub Mo3d}/I{sub Si2p} ratio obtained from the XPS spectra. The dispersion was lower for MoO{sub 3} loadings > 1%. Both the coordination and the degree of dispersion of the MoO{sub 3} determine the formation of C{sub 1} oxygenates.« less
  • In the studies of butane oxidation over supported vanadium oxides mentioned above, carbon oxides, butenes, and butadiene accounted for almost all of the reaction products, with only small amounts (less than 10%) of oxygenated products. Since the formation of oxygenated products probably involves the participation of lattice oxygen, it should depend also on the reducibility of the cations. It has been reported that oxygenates were formed in the oxidation of pentane over VPO, 12-molybdophosphoric acid, vanadomolybdophosphates, and vanadium-substituted molybdophosphoric acid. In particular, both maleic anhydride and phthalic anhydride were formed with high selectivities on VPO, whereas maleic anhydride was formedmore » on the heteropoly acids. Therefore, it seems that the oxidation of pentane can be used to further study the variation of selectivity on supported vanadia catalysts. Here, the authors report the results of such a study on vanadia catalysts supported on SiO{sub 2} and {gamma}-Al{sub 2}O{sub 3}. 11 refs., 2 figs., 1 tab.« less
  • The oxidation of ethane by oxygen was studied over silica catalysts supporting different amounts of vanadium with and without cesium. Three different catalytic properties of the product selectivity were observed, aldehyde formation, oxidative dehydrogenation (ODH), and combustion, depending upon the vanadium loading amount and the presence or the absence of cesium. A very low loading of vanadium (V:Si = 0.02--0.1 at.%) and the addition of Cs (Cs:Si = 1 at.%) on silica were found to be important for the formation of aldehyde. Not only acetaldehyde but also acrolein were observed in the aldehyde formation from ethane. On the other hand,more » catalysts with medium and high vanadium loadings (V:Si = 0.5--20 at.%) gave a dehydrogenated product, ethene, when Cs was not added to the catalysts. The addition of cesium to the catalysts with medium and high vanadium loadings changed the catalytic property from ODH to combustion. The different types of vanadyl species were identified by UV-visible and IR measurements in samples with different vanadium loadings. It was estimated that isolated vanadyl species with tetrahedral coordination, which were found mainly on the catalysts with vanadium loading lower than 0.5 at.%, became the active site for the aldehyde formation through the interaction with Cs. As a plausible reaction path giving acrolein from ethane, cesium-catalyzed cross-condensation between acetaldehyde and formaldehyde, formed in the reaction, was proposed. Polymeric vanadyl species with octahedral coordination were detected in the samples with medium (0.5--5.0 at.%) and high (10 and 20 at.%) vanadium loadings, respectively. Both species show the ODH catalytic property without cesium, but they bring about a deep oxidation of ethane if cesium is added to the catalysts.« less