纳米金催化剂

态形式存在的金元素是惰性的，但呈纳米形态时就会表现出独特的催化活性。纳米金原子簇团负载在氧化物上所产生的新的多相催化行为，对于大气污染物的消除、燃料电池用氢气的生产和净化、精细化学品的形成以及有机物的液相氧化反应都将产生重大的影响；尤其是纳米金催化剂优异的低温活性，对于制备常温环境净化材料将会有突出的贡献。

纳米金催化剂是一种新型的催化材料，其应用涉及众多反应，如催化CO氧化、臭氧分解、水气转移反应、NOx的还原、乙炔氢氯化、丙烯的环氧化、1，2-二醇的选择性液相氧化等。纳米金催化剂在环境温度和湿度下催化CO，可完全转化，因此使其成为军事和民事生命保障系统中净化CO的一个完美选择。

美国STREM工厂提供各种高纯度、品质卓越的纳米金催化剂，满足从事新材料以及纳米催化剂研究的科技人员研究需求。2008 年百灵威与STREM 正式签署战略合作协议，全权负责STREM 在中国市场的产品销售、技术应用与支持等各项业务。百灵威始终秉承“资源共享，共同发展”之理念，一如既往地为中国化学行业广大科研和生产用户提供品质卓越的有机金属、配体、催化剂等产品及服务！

metals • inorganics • organometallics • catalysts • ligands • customsynthesis • cGMP facilities • nanomaterials
Catalog Number and Name 79-0160
Gold 1% on aluminum oxide extrudates
(AUROlite™ Au/Al2O3 ) 79-0165
Gold 1% on titanium dioxide
extrudates
(AUROlite™ Au/TiO2) 79-0170
Gold 1% on zinc oxide granulate
(AUROlite™ Au/ZnO)
Color and Form dark purple extrudates
~1.2mm dia. x 5mm (avg) dark purple/gray extrudates
1.5mm dia. x 5mm (avg) dark purple granulate
1-2mm dia.
Analysis Au 1 wt% ± 0.1%
Al2O3 98 wt%
Na+, Cl- <1500ppm Au 1 wt% ± 0.1%
TiO2 98 wt%
Na+, Cl- <1500ppm Au 1wt% ± 0.1%
ZnO 88wt%
(contains Al2O3)
Na+, Cl- <1500ppm
Other Bulk density: 0.6–0.8 g/ml
Specific surface area:
200-260 m2/g (store cold) Bulk density: 0.85–0.95 g/ml
BET (surface area):
40-50 m2/g (store cold) Bulk density: 1-1.2 g/ml
BET (surface area):
40-50 m2/g (store cold)
Note:PCT WO2005115612
Available sizes: 10g, 50g
Sold in collaboration with Project AuTEK for research purposes. Reverse engineering and product modification prohibited.
Only open before use, store cold in dark.
Technical Note:
1. Useful product for the catalytic oxidation of a variety of substrates including carbon monoxide, aldehydes, alkenes and methane. Average gold crystallite size is ~2-3nm.
References:
1. J.Catal.,2007,252, 119.
2. J.Catal.,2008,260, 86.
3. Green Chem.,2008,10, 168.
4. Gold Bulletin,2008,41, 296.
"Please note: every care has been taken when producing the gold catalysts and their data sheets, however, users of the catalysts are advised that Mintek and its partners in Project AuTEK bear no responsibility for the performance of the catalysts or any accident, injury, death and / or damage arising from their delivery, handling or use.”


Reproduced from The Strem Chemiker, May, 2009.
Capabilities of AUROliteTMCatalysts
Jason S. McPherson and David T. Thompson
Project AuTEK, Advanced Materials Division, Mintek, Private Bag X3015, Randburg 2125, Republic of South Africa

AUROliteTMcatalysts (1wt%gold on titania, alumina and zinc oxide supports) are made in kilogram quantities by Project AuTEK and their advantages over other precious metal catalysts are being demonstrated by achieving high activities and selectivities in both liquid- and gas-phase reactions which have commercial potential.

1. Introduction
Gold catalysts are very active under the mild conditions which favour their selectivity and the economics of the processes involved. Careful choice of preparative conditions and supports helps to maximize their selectivity and activity [1]. Their potential in chemicalprocessing reactions has been clearly demonstrated and there is definite evidence of increasing R&D involving gold and gold-platinum group metal (PGM) combinations [2]. This is likely to result in new industrial applications for gold catalysts in chemical processing and pollution control. Selective oxidation of carbon monoxide in the hydrogen streams used for fuel cells has been achieved using AuTEK catalysts, as is the use of this ambient temperature oxidation process for use in gas masks for protection from CO poisoning and for CO removal from room atmospheres [2,3]. AuTEK has produced three gold catalyst systems, and use of these catalysts, and other closely related gold catalysts to optimize requirements for particular reactions where high activity or selectivity to desirable products is required, is indicated below.

2. Gas Phase Reactions
AUROliteTM catalysts have been evaluated for their CO oxidation characteristics at Oak Ridge National Laboratories, USA [4]. The Au/TiO2 catalyst gave 100% conversion of CO at < O°C and the Au/Al2O3 catalyst was also very active at low temperatures. All three AUROliteTM catalysts are being developed by Project AuTEK for CO oxidation in respiratory protection devices [5]. As can be seen in Figure 1, under typical EN403 (fire escape mask) test conditions the Au/TiO2 is more active and durable than the established commercial technology namely Hopcalite (CuMnOx). Furthermore under these conditions the activity of this material is amplified by the presence of moisture, unlike Hopcalite which experiences rapid deactivation.



Figure 1 : EN403 Simulation, feed = 2500ppm CO in air, 90%RH, 30LPM, constant flow, bed = 4.7cm diameter, particle size 1 - 2mm.

The AUROliteTM Au/TiO2 catalyst has been used for the oxidation of CO and H2 by O2 and N2O by a group from the Technical University of Denmark, Lyngby [6]. This group also studied the low temperature oxidation of methane on AUROliteTM catalysts and found them active and stable with very little sintering up to 250°C [7]. The catalysts have also been shown to give complete conversion of propene at 250 – 350°C (i.e. VOC removal) and the gold particles do not sinter under these conditions either [8]. The alumina and zinc oxide catalysts give high conversions in methanol oxidation [9]. In addition, all three catalysts are currently being assessed for water-gas shift and selective hydrogenation activity.

Gas phase selectivity of gold catalysts has been confirmed in an unconventional PROX system, where the complete removal of CO from ‘dirty’ hydrogen (i.e. down to < 1ppm CO from up to 2000 ppm). For use in a fuel cell, the carbon monoxide still present in the hydrogen, obtained by water-gas shift or from other sources, must be removed to prevent it poisoning the platinum electro-catalyst inside the fuel cell. Gold catalysts have been found to be effective for this preferential oxidation reaction. Whereas PGM catalysts oxidize both the CO and the hydrogen, gold is selective for CO at close to ambient temperatures. This has enabled Project AuTEK to develop a new system for hydrogen purification for PEM fuel cells, trade named AUROPureH2TM based on the use of a 3wt%Au/TiO2catalyst used at room temperature [10].

3. Liquid Phase Reactions


Following their successful use in the oxidation of glucose to gluconic acid, the conversion of D-lactose to D-lactobionic acid (LBA) has been studied using Project AuTEK catalysts.

Results obtained using samples of the three AuTEK gold catalysts show that all of these materials produce high selectivity for LBA under mild conditions [11]. It has been found, however, that the activities vary with support type, with the 1wt%Au/ZnO catalyst being the most reactive, as indicated in Table 1:

Table 1 : Support effects in the oxidation of D-lactose to D-lactobionic acid
0.8%Au/Al2O3 1%Au/TiO2 1%Au/ZnO
M x t20%*
( gAumin) 9.12 7.4 5.6
Selectivity (%) 94.3 95.1 93.9
C0=99.6 mmol l-1, 0.2 gcat, T = 60°C, pH=8, O2=2.5ml min-1, results adapted from ref 11.
*time in minutes to reach 20% conversion

AuTEK catalysts have also been used to catalyse the aerobic oxidation of aldehydes to esters, e.g. the conversion of acrolein tomethyl acrylate [12]:



Methyl acrylate is used in the manufacture of paints, in solvents and for acrylate coatings. This reaction proceeds in methanol using air as oxidant at room temperature, and therefore has the appeal of being 'green’ chemistry. The high conversions and selectivities are indicated in Table 2.

Table 2 : Synthesis of methyl acrylate from acrolein using 1wt%Au/TiO2 AuTEK catalyst
Time (h) 1 4 20
Conversion (%) 46 75 97
Selectivity (%) 43 66 87
Acrolein:Methanol 1:80, 0.3 mol % 1wt %Au/TiO2, T = 25°C, results adapted from ref 12.

In addition, the use of AuTEK catalysts has been studied for the reaction between benzaldehyde and methanol to produce methyl benzoate [12], which has a pleasant odour and is used in perfumes. 100% conversion was obtained in ca. 20 min when the benzoic acid:methanol ratio was 1:30 in the presence of 0.2 mol% 1wt%Au/TiO2 AuTEK catalyst and 10mol% NaOMe at 40°C:



Other reaction types for which AUROliteTM catalysts are being investigated include glucose and glycerol oxidation, direct hydrogen peroxide synthesis and hydrodechlorination of water contaminants such as trichloroethene.

4.Conclusions
Gold catalysts are likely to make a large and unique contribution to applications where efficient chemical processes of the kinddescribed herein are required under mild energy-efficient conditions, as is adequately indicated by the examples obtained using AuTEK catalysts and related work described in recent literature.

References:
[1] G.C. Bond, C. Louis and D.T. Thompson, Catalysis by Gold, Imperial College Press, London, 2006.
[2] C.W. Corti, R.J. Holliday and D.T. Thompson, Topics Catal., 2007, 44, 331.
[3] D.T. Thompson, Nanotoday, 2007, 2, 40.
[4] Z. Ma, C. Liang, S.H. Overbury and S. Dai, J Catal, 2007, 252, 119.
[5] D.Ramdayal, J. McPherson, T. Khumalo, G. Pattrick and E. van der Lingen, Proc. GOLD 2009, Heidelberg, Germany, July 2009.
[6] G. Walther, D.J. Mowbray, T. Jiang, G. Jones, S. Jensen, U.J. Quaade and S. Horch, J. Catal, 2008, 260, 86.
[7] G.Walther, L. Cervera-Gontard, U. Quaade and S. Horch, Gold Bull, 2009, in press
[8] L.F. Liotta, G. Pantaleo, G. Di Carlo, A.M. Venezia, G. Dagenallo, M. Ousmane, A. Giroir-Fendler and L. Retailleau, Proc. 'Catalysis for Society’ Conference, Krakow, Poland, May 2008.
[9] M. Ziolek, Paper to be presented to 6th World Conference on Oxidation Chemistry, Lille, France, July 2009.
[10] J. Steyn, G. Pattrick, E. van der Lingen, M. Scurrell and D. Hildebrandt, South African Patent Appl., 2006, 1120.
[11] E.V. Murzina, A.V. Tokarev, K. Kordas, H. Karhu, J.-P. Mikkloa and D.Y. Murzin, Catal Today, 2008, 131, 385.
[12] C.Marsden, E.Taarning, D.Hansen, L.Johansen, S.K.Klitgaard, K.Egeblad , C.H.Christensen, Green Chem, 2008, 10, 168, and private communication.