合成和金插在介孔二氧化硅的墙壁催化性能
Summary
Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.
Abstract
作为有希望的催化活性纳米反应器，在介孔二氧化硅（GMS）的插层纳米金成功地合成和材料的性能进行了研究。我们使用了一锅溶胶 – 凝胶方法来插层中孔二氧化硅的壁金纳米颗粒。开始与合成，P123用作模板以形成胶束。然后TESPTS用作表面改性剂插层金纳米颗粒。按照此过程，TEOS加入在作为经历聚合过程在酸性环境中的二氧化硅源。热液处理和煅烧后，获得的最终产品。几种技术被用于表征金插孔二氧化硅的孔隙率，形态和结构。结果表明金插后的介孔二氧化硅的稳定的结构。通过苄醇的氧化为基准的反应，所述GMS材料表现出高选择素拉了一和可回收性。
Introduction
作为一项新兴技术，在催化领域的应用潜力巨大，纳米材料已收到深入研究的兴趣在过去几十年。当中的纳米级催化剂报道，贵金属催化剂，如金，银，钯和铂吸引了世界的广泛关注1-3。选择催化反应包括一氧化碳研究者氧化的金，赫克在Pd催化剂的反应，并与铂分解水。尽管有为催化潜力，纳米级金在其适用性由于从中毒，焦化，热降解，和烧结失活限制。已经报道了金，作为贵金属的代表，具有高的选择性和不易于金属浸出，过度氧化和自中毒4。然而，金的催化性能强烈地依赖于颗粒尺寸。春田等人已报告的催化性能与去之间的关系ld的团簇直径，这表明金催化剂的活性最高粒度〜2.7毫微米5。
贵金属的粒径，可以通过在制备方法6-9进行控制;然而，走向广阔的应用的主要障碍仍然聚集而失去活性。为了解决烧结的问题，通常的方法是将固定纳米级颗粒在载体材料上。各种辅助材料已应用于包括多孔二氧化硅10-11，半导体金属氧化物12-13，聚合物14，石墨烯15和碳纳米管16。之间所使用的材料，多孔硅石是一个有吸引力的材料作为支持，因为它是唯一的弱酸性，相对惰性的，热和化学稳定的，并且能以非常明确的内消旋/微孔隙率来制备。多孔结构提供了良好的支持金属颗粒，但也赋予的大小选择衬底通道的金属催化剂。这种选择性是因为与这些多孔材料有关的可调谐性的特别有前途的。通常情况下，金颗粒被发现是在硅胶上表面17-18极其移动和容易地当暴露于高温时形成非常大的（50 + nm）的反应性的颗粒，从而使得难以制备金纳米颗粒在二氧化硅上19。 Mukherjee 等。的单分散金纳米粒子上的介孔二氧化硅的MCM-41由3-氨基丙基-三甲氧基硅烷和3-巯基丙基-三乙氧基硅烷，以及支持的金纳米颗粒报道固定化被认为是用于氢化反应的高活性和无浸出的金被发现在反应20。
下面介孔二氧化硅的表面改性的报告中，我们报道了法制备金嵌入到介孔二氧化硅（GMS）的墙。此外，介孔二氧化硅支持的方法提供了一个可扩展的APproach潜在独立地改变催化剂和多孔环境。由于催化过程是重要的经济意义，带来的好处可能是深远的。开发能力的“绿色”催化剂会对环境产生深远的积极影响和改善重要的工业过程的经济可行性和资源利用效率。
Protocol
Representative Results
Discussion
内的合成方案，关注的表面活性剂的浓度，pH值的溶液中，反应温度是在成功形成GMS是至关重要的。关键步骤是1.2，1.3，1.4和1.6。上述参数控制从表面活性剂形成的胶束的临界堆积参数和相位。胶束的相位和形态确定二氧化硅基质，将成为用于GMS框架的最终状态。另外，在形成过程中重要的是该序列和时间添加氯金酸溶液。 TEOS和TESPTS分别作为二氧化硅源和表面改性剂。加入两种化学物质首先确保…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors acknowledge National Science Foundation grant CHE- 1214068 for supporting this research project.
Materials
| poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) | Aldrich | 435465-250ML | |
| tetraethoxysilane | TCI | 201-083-8 | |
| bis[3-(triethoxysilyl)propyl]-tetrasulfide | GELEST | SIB1825.0-100GM | |
| chloroauric acid | Aldrich | 520918-1G | |
| benzyl alcohol | Sigma-Aldrich | 305197-1L | |
| nitrogen physisorption | Micromeritics | Tristar II | |
| X-ray diffraction | Philips | X'Pert Pro | |
| transmission electron microscopy | Philips | CM200 | |
| gas chromatography | Shimadzu | GC-2010 |
References
- Liguras, D. K., Kondarides, D. I., Verykios, X. E. Production of hydrogen for fuel cells by steam reforming of ethanol over supported noble metal catalysts. Appl. Catal. B-Environ. 43 (4), 345-354 (2003).
- Gelin, P., Primet, M. Complete oxidation of methane at low temperature over noble metal based catalysts: a review. Appl. Catal. B-Environ. 39 (1), 1-37 (2002).
- Lu, S. F., Pan, J., Huang, A. B., Zhuang, L., Lu, J. T. Alkaline polymer electrolyte fuel cells completely free from noble metal catalysts. Proc. Natl. Acad. Sci. U. S. A. 105 (52), 20611-20614 (2008).
- Ma, C. Y., et al. Catalytic oxidation of benzyl alcohol on Au or Au–Pd nanoparticles confined in mesoporous silica. Applied Catalysis B: Environmental. 92 (1-2), 202-208 (2009).
- Bamwenda, G. R., Tsubota, S., Nakamura, T., Haruta, M. The influence of the preparation methods on the catalytic activity of platinum and gold supported on TiO2 for CO oxidation. Catalysis Letters. 44 (1-2), 83-87 (1997).
- Brown, K. R., Walter, D. G., Natan, M. J. Seeding of colloidal Au nanoparticle solutions. 2. Improved control of particle size. 12 (2), 306-313 (2000).
- Niesz, K., Grass, M., Somorjai, G. A. Precise control of the Pt nanoparticle size by seeded growth using EO13PO30EO13 triblock copolymers as protective agents. Nano Lett. 5 (11), 2238-2240 (2005).
- Yuranov, I., et al. Pd/SiO2 catalysts: synthesis of Pd nanoparticles with the controlled size in mesoporous silicas. J. Mol. Catal. A-Chem. 192, 1-2 (2003).
- Brinas, R. P., Hu, M. H., Qian, L. P., Lymar, E. S., Hainfeld, J. F. Gold nanoparticle size controlled by polymeric Au(I) thiolate precursor size. J. Am. Chem. Soc. 130 (3), 975-982 (2008).
- Zhu, H. G., Liang, C. D., Yan, W. F., Overbury, S. H., Dai, S. Preparation of highly active silica-supported Au catalysts for CO oxidation by a solution-based technique. J. Phys. Chem. B. 110 (22), 10842-10848 (2006).
- Gabaldon, J. P., Bore, M., Datye, A. K. Mesoporous silica supports for improved thermal stability in supported Au catalysts. Top. Catal. 44 (1-2), 253-262 (2007).
- Li, F. B., Li, X. Z. The enhancement of photodegradation efficiency using Pt-TiO2 catalyst. Chemosphere. 48 (10), 1103-1111 (2002).
- Sakthivel, S., et al. Enhancement of photocatalytic activity by metal deposition: characterisation and photonic efficiency of Pt, Au and Pd deposited on TiO2 catalyst. Water Res. 38 (13), 3001-3008 (2004).
- Jia, C. G., Wang, Y. P., Feng, H. Y. Preparation and Catalytic Properties Of Polymer-Supported Fe-Co-Cu And Fe-Co-Au Pentametallic Clusters. React. Polym. 18 (3), 203-211 (1992).
- Yu, X. Q., et al. Reduced graphene oxide supported Au nanoparticles as an efficient catalyst for aerobic oxidation of benzyl alcohol. Appl. Surf. Sci. 280, 450-455 (2013).
- Xu, Y. Y., et al. Au@Pt core-shell nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation. Catal. Commun. 13 (1), 54-58 (2011).
- Baker, C. O., et al. Size Control of Gold Nanoparticles Grown on Polyaniline Nanofibers for Bistable Memory Devices. ACS Nano. 5 (5), 3469-3474 (2011).
- Wei, G. -. T., Yang, Z., Lee, C. Y., Yang, H. Y., Wang, C. R. Aqueous−Organic Phase Transfer of Gold Nanoparticles and Gold Nanorods Using an Ionic Liquid. J. Am. Chem. Soc. 126 (16), 5036-5037 (2004).
- Gadenne, B., Hesemann, P., Moreau, J. E. Supported ionic liquids: ordered mesoporous silicas containing covalently linked ionic species. Chemical Communications. 15, 1768-1769 (2004).
- Yang, J. H., et al. Understanding preparation variables in the synthesis of Au/Al2O3 using EXAFS and electron microscopy. Applied Catalysis A: General. 291 (1-2), 73-84 (2005).
- Chen, L. F., et al. Intercalation of aggregation-free and well-dispersed gold nanoparticles into the walls of mesoporous silica as a robust ‘green’ catalyst for n-alkane oxidation. Journal of the American Chemical Society. 131, 914-915 (2009).
- Wang, X., et al. Nanoscale gold intercalated into mesoporous silica as a highly active and robust catalyst. Nanotechnology. 23, 294010-294018 (2012).
- Chen, L. F., et al. Controlled synthesis of nanoscale icosahedral gold particles at room temperature. Chemcatchem. 4, 1662-1667 (2012).
