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Title: Low-Temperature CO oxidation on Au/fumed SiO 2-based catalysts prepared from Au(en) 2C 13

Abstract

Many gold catalysts have been actively surveyed, but Au/SiO{sub 2} catalysts that are highly active for CO oxidation still remain evasive. In this work, gold nanoparticles well dispersed on Cab-O-Sil fumed SiO{sub 2} were prepared using Au(en){sub 2}Cl{sub 3} (en = ethylenediamine) as the precursor, and found to be very active for CO oxidation below 0 C. The catalyst pretreatment via reduction and calcination, effect of gold loading, post-treatment in acidic and basic media, catalyst deactivation, storage, regeneration, and effect of surface modification by other metal oxides were explored. The results provide new perspective on the activation and promotion of active Au/SiO{sub 2}-based catalysts.

Authors:
 [1];  [1];  [1];  [1];  [2];  [1]
  1. ORNL
  2. {Steve} H [ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931766
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Catalysis A; Journal Volume: 326; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBON MONOXIDE; OXIDATION; CATALYTIC EFFECTS; GOLD; CATALYST SUPPORTS; SILICON OXIDES; CHEMICAL PREPARATION; CATALYSTS; PRECURSOR; GOLD CHLORIDES; CALCINATION; DEACTIVATION; REGENERATION

Citation Formats

Zhu, Haoguo, Ma, Zhen, Clark, Jason C, Pan, Zhengwei, Overbury, Steven, and Dai, Sheng. Low-Temperature CO oxidation on Au/fumed SiO2-based catalysts prepared from Au(en)2C13. United States: N. p., 2007. Web. doi:10.1016/j.apcata.2007.04.004.
Zhu, Haoguo, Ma, Zhen, Clark, Jason C, Pan, Zhengwei, Overbury, Steven, & Dai, Sheng. Low-Temperature CO oxidation on Au/fumed SiO2-based catalysts prepared from Au(en)2C13. United States. doi:10.1016/j.apcata.2007.04.004.
Zhu, Haoguo, Ma, Zhen, Clark, Jason C, Pan, Zhengwei, Overbury, Steven, and Dai, Sheng. Mon . "Low-Temperature CO oxidation on Au/fumed SiO2-based catalysts prepared from Au(en)2C13". United States. doi:10.1016/j.apcata.2007.04.004.
@article{osti_931766,
title = {Low-Temperature CO oxidation on Au/fumed SiO2-based catalysts prepared from Au(en)2C13},
author = {Zhu, Haoguo and Ma, Zhen and Clark, Jason C and Pan, Zhengwei and Overbury, Steven and Dai, Sheng},
abstractNote = {Many gold catalysts have been actively surveyed, but Au/SiO{sub 2} catalysts that are highly active for CO oxidation still remain evasive. In this work, gold nanoparticles well dispersed on Cab-O-Sil fumed SiO{sub 2} were prepared using Au(en){sub 2}Cl{sub 3} (en = ethylenediamine) as the precursor, and found to be very active for CO oxidation below 0 C. The catalyst pretreatment via reduction and calcination, effect of gold loading, post-treatment in acidic and basic media, catalyst deactivation, storage, regeneration, and effect of surface modification by other metal oxides were explored. The results provide new perspective on the activation and promotion of active Au/SiO{sub 2}-based catalysts.},
doi = {10.1016/j.apcata.2007.04.004},
journal = {Applied Catalysis A},
number = 1,
volume = 326,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The active oxygen species and mechanism for catalytic CO oxidation with O{sub 2} on a highly active TiO{sub 2}-supported Au catalyst (denoted as Au/Ti(OH){sub 4}{sup *}), which was prepared by supporting a Au-phophine complex on as-precipitated wet titanium hydroxide followed by calcination at 673 K, have been studied by means of oxygen isotope exchange, O{sub 2} temperature-programmed desorption (O{sub 2} TPD), electron spin resonance (ESR), and Fourier-transformed infrared spectroscopy (FT-IR). Surface lattice oxygen atoms on the Au/Ti(OH){sub 4}{sup *} catalyst were inactive for oxygen exchange with O{sub 2} and CO and also for CO oxidation at room temperature. The surfacemore » lattice oxygen atoms were exchanged only with the oxygen atoms of CO{sub 2}, probably via carbonates. O{sub 2} did not dissociate to atomic oxygen on the catalyst. The catalyst showed a paramagnetic signal at g = 2.002 due to unpaired electrons trapped at oxygen vacancies mainly at the surface. O{sub 2} adsorbed on the oxygen vacancies to form superoxide O{sub 2}{sup {minus}} with g{sub 1} = 2.020, g{sub 2} = 2.010, and g{sub 3} = 2.005, which are characteristic of O{sub 2}{sup {minus}} with an angular arrangement. Upon CO exposure, all the adsorbed oxygen species disappeared. The mechanism for the catalytic CO oxidation on the active Au/Ti(OH){sub 4}{sup *} catalyst is discussed in detail and compared with mechanisms reported previously.« less
  • Gold catalysts for low-temperature CO oxidation were prepared by immobilizing gold colloids of about 2 nm size on TiO{sub 2} and ZrO{sub 2} in aqueous solution. The gold particles nearly retained their size after immobilization on both supports. Slight sintering was observed by X-ray diffraction and high-resolution transmission electron microscopy after calcination at 673 K. Some of the gold particles on ZrO{sub 2} showed hexagonal symmetry with close-packed Au(111) surfaces. X-ray photoelectron spectroscopy investigations indicated that the gold was in a metallic state. Whereas gold particles on TiO{sub 2} showed CO conversion directly after preparation and drying, significant activity ofmore » gold on ZrO{sub 2} was only observed after calcination in air. CO adsorption was reversible on all catalysts and weaker on the most active catalysts, as shown by diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and pulse thermal analysis. Probing of the gold sites by CO adsorption revealed the existence of different gold sites in these catalysts. Step/kink sites (2111--1223 cm{sup {minus}1}) and positively polarized gold sites (2128--2135 cm{sup {minus}1}) were identified on uncalcined and in situ calcined gold catalysts. The number of low-coordinated gold sites was much higher on TiO{sub 2}, whereas on ZrO{sub 2} more positively polarized gold atoms were found. This behavior was traced to the shape of the gold particles, which affects the number of low-coordinated gold atoms and is dependent on support and treatment. In situ treatment in oxygen led to a temporarily inactive catalyst with additional bands in the DRIFTS spectrum in the 2000--2400 cm{sup {minus}1} region, stemming from CO adsorbed on positively polarized gold sites (2130--2150 cm{sup {minus}1}) and on the support (2180--2200 cm{sup {minus}1}), and from molecularly adsorbed CO{sub 2} (2353 cm{sup {minus}1}). No bands arising from CO on low-coordinated, metallic gold sites were identified in that case.« less
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