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1.
As a renewable feedstock and due to its high functionality glycerol is an attractive reactant for the production of a large number of valuable compounds. We report on an environmentally friendly alternative to produce chemicals from the glycerol oxidation, which are currently produced either by stoichiometric oxidation processes or by enzymatic routes. We investigate the heterogeneously catalyzed liquid-phase oxidation of glycerol with carbon supported gold catalysts. The prepared nanosized gold catalysts are highly active, so that the reaction could be performed under atmospheric pressure. The influence of the preparation method of the catalysts has been investigated. Moreover, the support effect on the catalytic process has been studied and discussed in terms of pore structure of the investigated carbon materials. The promotor effect of platinum on Au/C catalysts was examined and it could be shown that the presence of Pt increases not only the catalyst activity but also the selectivity. By promoting the gold catalysts with platinum the selectivity to dihydroxyacetone could be increased from 26% (Au/C) to 36% (Au–Pt/C). 相似文献
2.
Christine Baatz Nadine Thielecke Ulf Prüße 《Applied catalysis. B, Environmental》2007,70(1-4):653-660
In this work, two deposition–precipitation methods for the preparation of gold catalysts for glucose oxidation were investigated. Thus far, gold colloids immobilized on carbon have been used for catalytic glucose oxidation, but the long-term stability of these systems was not sufficient. To improve the long-term stability we used the deposition–precipitation methods using NaOH (DP NaOH) or urea (DP urea) as precipitation agents as they were described by Haruta and Dekkers, respectively, using alumina as a support material. With these methods, it was possible to prepare highly active and selective catalysts which showed an excellent long-term stability. DP urea was found to be the preferred method, because in contrast to DP NaOH, no losses of gold occurred during the preparation, and it was possible to adjust various gold contents up to 10 wt% Au. 相似文献
3.
Vasko Idakiev Tatyana Tabakova Krassimir Tenchev Zhong-Yong Yuan Tie-Zhen Ren Bao-Lian Su 《Catalysis Today》2007,128(3-4):223-229
New gold catalytic system prepared on ceria-modified mesoporous titania (CeMTi) used as water-gas shift (WGS) reaction catalyst is reported. Mesoporous titania (MTi) was synthesized using surfactant templating method through a neutral [C13(EO)6–Ti(OC3H7)4] assembly pathway. Ceria modifying additive was deposited on MTi by deposition precipitation (DP) method. Gold-based catalysts with different gold content (1–5 wt.%) were synthesized by DP of gold hydroxide on mixed metal oxide support. The supports and the catalysts were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), N2 adsorption analysis and temperature-programmed reduction (TPR). The catalytic behavior of the gold-based catalysts was evaluated in WGS reaction in a wide temperature range (140–300 °C) and at different space velocities and H2O/CO ratios. The influence of gold content and particle size on the catalytic performance was investigated. The WGS activity of the new gold/ceria-modified mesoporous titania catalysts was compared with that of gold catalysts supported on simple oxides CeO2 and mesoporous TiO2, as well as gold/ceria-modified titania and reference catalyst Au/TiO2 type A (World Gold Council). A high degree of synergistic interaction between ceria and mesoporous titania and a positive modification of structural and catalytic properties by ceria has been achieved. It is clearly revealed that the ceria-modified mesoporous titania is of much interest as potential support for gold-based catalyst. The Au/ceria-modified mesoporous titania catalytic system is found to be efficient catalyst for WGSR. 相似文献
4.
纳米金复合催化剂制备及其低温选择催化环己烷氧化性能 总被引:3,自引:0,他引:3
采用光催化直接还原法将Au(0)负载在TiO2修饰的中孔分子筛MCM-41的孔道内外,采用XRD, N2吸附-脱附,FT-IR, TEM和EDS等手段对所制催化剂进行了表征,并考察了其在温和条件下对环己烷选择性氧化反应的催化性能. 结果表明,所制纳米金催化剂的分子筛载体仍具有较高的结晶度,金颗粒粒径在10 nm左右. 在环己烷氧化反应中,纳米金与TiO2光催化共同作用,使复合催化剂具有低温高催化活性. 在温度100℃、压力1.0 MPa及250 W紫外灯光照8 h的条件下,环己烷转化率高达3.9%,目的产物的总选择性为90.2%. 相似文献
5.
Nanoporous gold (NPG), a novel unsupported gold catalyst prepared by dealloying, exhibits exceptional catalytic activity for CO oxidation. Systematic studies were carried out on this new catalytic system, including the active sites of catalysts, the reaction kinetics, and activity dependence as functions of space velocity and temperature. Our results show strong evidence that metallic gold atoms on NPG are the intrinsic active sites at which the reaction of CO with O2 occurs. The kinetic study found that the reaction rate of CO oxidation on unsupported NPG depends significantly on CO concentration but only slightly on O2 concentration. We suggest that CO adsorption plays a decisive role in CO oxidation on NPG as the rate-limiting step. By completely ruling out the support influence, our findings provide considerable insight into the role of gold catalysts. 相似文献
6.
《Journal of Catalysis》2006,237(1):190-196
Gold catalysts supported on TiO2 were prepared by a deposition–precipitation (DP) method to investigate how highly reproducible performance of the gold catalysts in CO oxidation can be achieved. A protocol was established for synthesizing identically performing catalysts by different operators. The results show that for this synthesis route, the calcination step is not needed to form highly active Au/TiO2 catalysts, but leads to decreased activity. Improved catalytic activity was observed when a high solution pH was adjusted during the precipitation. Surprisingly, wet impregnation followed by ammonia steam treatment and a washing step with water also leads to Au/TiO2 with 2- to 4-nm individual gold particles highly dispersed on the TiO2 surface. In addition, this catalyst is active for room temperature CO oxidation. The temperature for 50% conversion of CO is below 25 °C, which is comparable to that of the gold catalyst prepared by the DP method. Therefore, contrary to reports in the literature, the impregnation method can be used in the preparation of high-activity gold catalysts. 相似文献
7.
8.
A. Aboukaïs E. A. Zhilinskaya I. N. Filimonov N. S. Nesterenko S. E. Timoshin I. I. Ivanova 《Catalysis Letters》2006,108(1-2):97-102
The Au/SnO2 catalysts were prepared by a co-precipitation method. The structure of the sample treated at different temperatures was investigated
by means of HRTEM and XPS. The structure of the samples after various treatments and their activity in the CO oxidation were
compared. The results showed that the catalytic behavior was related to the particle size of gold and surface oxygen species
on the support. Highly dispersed gold particles and adsorbed surface oxygens and hydroxyl groups on the support were responsible
for the high catalytic activity of the Au/SnO2 catalyst. 相似文献
9.
V. Idakiev T. Tabakova K. Tenchev Z.-Y. Yuan T.-Z. Ren B.-L. Su 《Journal of Porous Materials》2012,19(1):15-20
New gold catalytic system prepared on ceria-modified mesoporous zirconia used as water–gas shift (WGS) catalyst is reported.
Mesoporous zirconia was synthesized using surfactant templating method through a neutral [C13(EO)6-Zr(OC3H7)4] assembly pathway. Ceria modifying additive was deposited on mesoporous zirconia by deposition–precipitation method. Gold-based
catalysts with different gold content (1–3 wt. %) were synthesized by deposition–precipitation of gold hydroxide on mixed
metal oxide support. The supports and the catalysts were characterized by powder X-ray diffraction, high-resolution transmission
electron microscopy, N2 adsorption analysis and temperature programmed reduction. The catalytic behavior of the gold-based catalysts was evaluated
in WGS reaction in a wide temperature range (140–300 °C) and at different space velocities and H2O/CO ratios. The influence of gold content and particle size on the catalytic performance was investigated. The WGS activity
of the new Au/ceria-modified mesoporous zirconia catalysts was compared with that of gold catalysts supported on simple oxides
CeO2 and mesoporous ZrO2, revealing significantly higher catalytic activity of Au/ceria-modified mesoporous zirconia. A high degree of synergistic
interaction between ceria and mesoporous zirconia and a positive modification of structural and catalytic properties by ceria
have been achieved. It is clearly revealed that the ceria-modified mesoporous zirconia is of much interest as potential support
for gold-based catalyst. The Au/ceria-modified mesoporous zirconia catalytic system is found to be effective catalyst for
WGS reaction. 相似文献
10.
V. Idakiev T. Tabakova A. Naydenov Z.-Y. Yuan B.-L. Su 《Applied catalysis. B, Environmental》2006,63(3-4):178-186
Mesoporous ZrO2 with high surface area and uniform pore size distribution, synthesized by surfactant templating through a neutral [C13(EO)6–Zr(OC3H7)4] assembly pathway, was used as a support of gold catalysts prepared by deposition–precipitation method. The supports and the catalysts were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, N2 adsorption analysis, temperature programmed reduction and desorption. The catalytic activity of gold supported on mesoporous zirconia was evaluated in water–gas shift (WGS) reaction at wide temperature range (140–300 °C) and at different space velocities and H2O/CO ratios. The catalytic behaviour and the reasons for а reversible deactivation of Au/mesoporous zirconia catalysts were studied. The influence of gold content and particle size on the catalytic performance was investigated. The WGS activity of the new Au/mesoporous zirconia catalyst was compared to the reference Au/TiO2 type A (World Gold Council), revealing significantly higher catalytic activity of Au/mesoporous zirconia catalyst. It is found that the mesoporous zirconia is a very efficient support of gold-based catalyst for the WGS reaction. 相似文献
11.
12.
《Catalysis communications》2007,8(1):57-64
Au, Ag and Au–Ag catalysts on different supports of alumina, titania and ceria were studied for their catalytic activity of ethylene oxidation reactions. An addition of an appropriate amount of Au on Ag/Al2O3 catalyst was found to enhance the catalytic activity of the ethylene epoxidation reaction because Au acts as a diluting agent on the Ag surface creating new single silver sites which favor molecular oxygen adsorption. The Ag catalysts on both titania and ceria supports exhibited very poor catalytic activity toward the epoxidation reaction of ethylene, so pure Au catalysts on these two supports were investigated. The Au/TiO2 catalysts provided the highest selectivity of ethylene oxide with relatively low ethylene conversion whereas, the Au/CeO2 catalysts was shown to favor the total oxidation reaction over the epoxidation reaction at very low temperatures. In comparisons among the studied catalysts, the bimetallic Au–Ag/Al2O3 catalyst is the best candidate for the ethylene epoxidation. The catalytic activity of the gold catalysts was found to depend on the support material and catalyst preparation method which govern the Au particle size and the interaction between the Au particles and the support. 相似文献
13.
锆改性氧化铝负载的纳米金催化剂上环己烷氧化研究 总被引:6,自引:0,他引:6
通过浸溃法制备氧化锫改性的氧化铝载体,并采用改进的阴离子交换法(DAE)制备了负载型纳米金催化剂.以分子氧为氧化剂,考察了金催化剂在环己烷选择性氧化制环己酮和环己醇反应中的催化性能.结果表明,提高锆含量,环己烷转化率保持稳定,环己酮和环己醇总选择性,尤其是环己酮的选择性明显提高.随着金负载量增加,金颗粒增大,催化剂的活性降低,金颗粒在6nm以下的催化剂具有很高的催化活性.在423K,1.5MPa、3h反应条件下,0.6%(wt) 金和17%(wt)锆含量的催化剂上环己烷氧化得到9,5%的转化率,环己酮和环己醇的选择性分别为38.8%和51.5%. 相似文献
14.
Jong Hwa Park Ji Man Kim Mingshi Jin Jong-Ki Jeon Seung-Soo Kim Sung Hoon Park Sang Chai Kim Young-Kwon Park 《Nanoscale research letters》2012,7(1):14
The low-temperature catalytic ozone oxidation of benzene was investigated. In this study, Al-SBA-16 (Si/Al = 20) that has
a three-dimensional cubic Im3m structure and a high specific surface area was used for catalytic ozone oxidation for the first
time. Two different Mn precursors, i.e., Mn acetate and Mn nitrate, were used to synthesize Mn-impregnated Al-SBA-16 catalysts.
The characteristics of these two catalysts were investigated by instrumental analyses using the Brunauer-Emmett-Teller method,
X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction. A higher catalytic activity was
exhibited when Mn acetate was used as the Mn precursor, which is attributed to high Mn dispersion and a high degree of reduction
of Mn oxides formed by Mn acetate than those formed by Mn nitrate. 相似文献
15.
16.
Oxidation Catalysis by Supported Gold Nano-Clusters 总被引:4,自引:0,他引:4
The historical notion regarding the inability of gold to catalyze reactions has been discarded in view of recent studies, which have clearly demonstrated the high catalytic efficiency of supported nano-gold catalysts. Although nano-Au catalysts are known to catalyze a variety of reactions, the major focus has been on CO oxidation catalysis. In this work we focus on the important aspects related to the CO oxidation reaction. Special emphasis is placed on the studies undertaken on model nano-Au systems as these studies have considerably enhanced the understanding of the oxidation process. Gold in a highly dispersed state can selectively oxidize CO in the presence of excess hydrogen (of tremendous interest to state-of-the-art low-temperature fuel cells); related studies are addressed in this review. The nano-gold catalysts have also been investigated for the direct vapor-phase oxidation of propylene to propylene oxide in the presence of molecular oxygen; these investigations are highlighted in this work. 相似文献
17.
Supported gold catalysts on the mesoporous (MSP) metal oxides were prepared by a one-step, ultrasound-assisted reduction method,
and characterized by XRD, HRTEM, EDX, BET, and XPS analysis. Their catalytic activities were examined in the oxidation of
CO. Compared to the Au/Fe2O3(MSP) catalyst, the Au/TiO2(MSP) and Au/Fe2O3-TiO2(MSP) catalysts exhibited higher catalytic activity in the oxidation of CO at low temperatures. The high catalytic activity
of Au/TiO2(MSP) was attributed to the metallic state of the gold nanoparticles, their small size (2–2.5 nm), and their high dispersion
on the catalyst support. 相似文献
18.
Li Wen Jin-Kun Fu Ping-Ying Gu Bing-Xing Yao Zhong-Hua Lin Jian-Zhang Zhou 《Applied catalysis. B, Environmental》2008,79(4):402-409
Monodispersed nano-Au/γ-Al2O3 catalysts for low-temperature oxidation of CO have been prepared via a modified colloidal deposition route, which involves the deposition of dodecanethiolate self-assembled monolayer (SAM)-protected gold nanoparticles (C12 nano-Au) in hexane on γ-Al2O3 at room temperature. The diameter of the gold nanoparticles deposited on the support is 2.5 ± 0.8 nm after thermal treatment, and their valence states comprise both the metallic and oxidized states. It is found that the thermal treatment temperature affects significantly the catalytic activity of the catalysts in the processing steps. The catalyst treated at 190 °C exhibits considerably higher activity as compared to catalysts treated at 165 and 250 °C. A 2.0-wt.% nano-Au/γ-Al2O3 catalyst treated at 190 °C for 15 h maintains the catalytic activity at nearly 100% CO oxidation for at least 800 h at 15 °C, at least 600 h at 0 °C, and even longer than 450 h at −5 °C. Evidently, the catalysts obtained using this preparation route show high catalytic activity, particularly at low temperatures, and a good long-term stability. 相似文献
19.
《Catalysis communications》2008,9(3):355-361
A series of gold/iron-oxide catalysts for catalytic combustion of formaldehyde were prepared by co-precipitation. The catalyst containing 7.10 wt% of gold exhibited the highest catalytic activity. On this catalyst, the catalytic combustion reaction of formaldehyde proceeded at considerable rates at 20 °C and complete burn-off of formaldehyde was achieved at 80 °C. The catalysts were stable and remained active in the presence of moisture and are good substitutes for the noble metals (Pt, Pd) catalysts. The structure of catalysts, the valence state of gold and the size of gold particles were investigated by X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy techniques. Gold atoms with fractional positive charge (Auδ+) were found to exist in the catalyst and play an important role in the catalytic activity. Interaction between active species and support also provided important contribution to the valence state of gold and the activity for the catalytic combustion of HCHO. 相似文献
20.
Peter Haider Bertram Kimmerle Frank Krumeich Wolfgang Kleist Jan-Dierk Grunwaldt Alfons Baiker 《Catalysis Letters》2008,125(3-4):169-176
The effect of the size of gold particles deposited on CeO2 and TiO2 supports on their catalytic behavior in the aerobic oxidation of benzyl alcohol in different solvents (mesitylene, toluene, and supercritical carbon dioxide) has been investigated. The size of supported gold particles deposited via a colloidal route was in the range 1.3–11.3 nm, as determined by means of EXAFS and HAADF-STEM measurements. The catalytic performance of the supported gold catalysts in the different solvents revealed a significant effect of the gold particle size. Optimal activity was observed for catalysts with medium particle size (ca. 6.9 nm) whereas smaller and bigger particles showed inferior activity. Identical trends for the activity–particle size relationship were found using Au/CeO2 and Au/TiO2 for the reaction at atmospheric pressure in conventional solvents (mesitylene, toluene) as well as under supercritical conditions (scCO2). Selectivity to benzaldehyde was only weakly affected by the gold particle size and mainly depended on reaction conditions. In supercritical CO2 (scCO2) selectivity was higher than in the conventional solvents under atmospheric pressure. All catalysts tested with particle sizes ranging from 1.3 to 11.3 nm showed excellent selectivity of 99% or higher under supercritical conditions. 相似文献