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Title: Evidence for and mitigation of the encapsulation of gold nanoparticles within silica supports upon high-temperature treatment of Au/SiO(2) catalysts: Implication to catalyst deactivation

Abstract

Silica is one of the most widely used catalyst supports for metal nanocatalysts. Although the sintering of metal nanoparticles on various silicasupports has been extensively studied, the restructuring of silicasupports and its effect on supported metal nanoparticles have been seldom investigated. In this paper, silica-supported gold catalysts were used as a model system to probe the interplay of silicasupports and metal nanoparticles under high-temperature treatment conditions. Gold was loaded onto mesoporous SiO{sub 2} (SBA-15) using Au(en){sub 2}Cl{sub 3} as the precursor in the presence of aqueous NaOH (pH {approx} 10). The influence of high-temperature treatment on the textural and structural changes of SBA-15 and Au/SBA-15 was studied by X-ray diffraction (XRD), N{sub 2} adsorption-desorption, and transmission electron microscopy (TEM). Control experiments were conducted using an amorphous SiO{sub 2} (Cab-O-Sil) as the support. It was found that SBA-15 undergoes significant phase transformation to crystalline cristobalite upon high-temperaturetreatment, resulting in the dramatic decrease in surface area. More interestingly, the crystallization of SiO{sub 2} leads to the encapsulation of goldnanoparticles inside the SiO{sub 2} matrix. This conclusion was proven by aqua regia leaching, EDX, and SEM/TEM experiments. Goldnanoparticles can also be encapsulated into the SiO{sub 2} matrix when using Cab-O-Sil as the support,more » but the process takes place under much higher temperatures. The encapsulation of gold nanoparticles can be mitigated by coating Au/SBA-15 with amorphous Al{sub 2}O{sub 3} or by coating SBA-15 with Al{sub 2}O{sub 3} before loading gold. Our findings shed new light on the deactivation of supported gold catalysts under high-temperature conditions.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1044689
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Applied Catalysis A
Additional Journal Information:
Journal Volume: 386; Journal Issue: 1-2; Journal ID: ISSN 0926-860X
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AQUA REGIA; CATALYST SUPPORTS; CATALYSTS; COATINGS; CRISTOBALITE; CRYSTALLIZATION; DEACTIVATION; ENCAPSULATION; GOLD; LEACHING; MITIGATION; PHASE TRANSFORMATIONS; PRECURSOR; PROBES; SILICA; SINTERING; SURFACE AREA; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION

Citation Formats

Dai, Sheng, Yin, Hongfeng, Ma, Zhen, Zhu, Haoguo, and Chi, Miaofang. Evidence for and mitigation of the encapsulation of gold nanoparticles within silica supports upon high-temperature treatment of Au/SiO(2) catalysts: Implication to catalyst deactivation. United States: N. p., 2010. Web.
Dai, Sheng, Yin, Hongfeng, Ma, Zhen, Zhu, Haoguo, & Chi, Miaofang. Evidence for and mitigation of the encapsulation of gold nanoparticles within silica supports upon high-temperature treatment of Au/SiO(2) catalysts: Implication to catalyst deactivation. United States.
Dai, Sheng, Yin, Hongfeng, Ma, Zhen, Zhu, Haoguo, and Chi, Miaofang. Fri . "Evidence for and mitigation of the encapsulation of gold nanoparticles within silica supports upon high-temperature treatment of Au/SiO(2) catalysts: Implication to catalyst deactivation". United States.
@article{osti_1044689,
title = {Evidence for and mitigation of the encapsulation of gold nanoparticles within silica supports upon high-temperature treatment of Au/SiO(2) catalysts: Implication to catalyst deactivation},
author = {Dai, Sheng and Yin, Hongfeng and Ma, Zhen and Zhu, Haoguo and Chi, Miaofang},
abstractNote = {Silica is one of the most widely used catalyst supports for metal nanocatalysts. Although the sintering of metal nanoparticles on various silicasupports has been extensively studied, the restructuring of silicasupports and its effect on supported metal nanoparticles have been seldom investigated. In this paper, silica-supported gold catalysts were used as a model system to probe the interplay of silicasupports and metal nanoparticles under high-temperature treatment conditions. Gold was loaded onto mesoporous SiO{sub 2} (SBA-15) using Au(en){sub 2}Cl{sub 3} as the precursor in the presence of aqueous NaOH (pH {approx} 10). The influence of high-temperature treatment on the textural and structural changes of SBA-15 and Au/SBA-15 was studied by X-ray diffraction (XRD), N{sub 2} adsorption-desorption, and transmission electron microscopy (TEM). Control experiments were conducted using an amorphous SiO{sub 2} (Cab-O-Sil) as the support. It was found that SBA-15 undergoes significant phase transformation to crystalline cristobalite upon high-temperaturetreatment, resulting in the dramatic decrease in surface area. More interestingly, the crystallization of SiO{sub 2} leads to the encapsulation of goldnanoparticles inside the SiO{sub 2} matrix. This conclusion was proven by aqua regia leaching, EDX, and SEM/TEM experiments. Goldnanoparticles can also be encapsulated into the SiO{sub 2} matrix when using Cab-O-Sil as the support, but the process takes place under much higher temperatures. The encapsulation of gold nanoparticles can be mitigated by coating Au/SBA-15 with amorphous Al{sub 2}O{sub 3} or by coating SBA-15 with Al{sub 2}O{sub 3} before loading gold. Our findings shed new light on the deactivation of supported gold catalysts under high-temperature conditions.},
doi = {},
journal = {Applied Catalysis A},
issn = {0926-860X},
number = 1-2,
volume = 386,
place = {United States},
year = {2010},
month = {1}
}