调整二苯醚氢氧化的Pt/CNT催化剂的酸度
Summary
提出了HNbWO 6、HNbMoO6、HTaWO6固体酸纳米板改性Pt/CNT的合成方案。
Abstract
本文提出了一种合成HNbWO 6、HNbMoO6、HTaWO6固体酸纳米板改性Pt/CNT的方法。通过改变各种固体酸纳米片的重量，一系列具有不同固体酸成分的Pt/xHMNO 6/CNT（x = 5，20 wt）;M = Nb，塔;N = Mo， W） 已制备通过碳纳米管预处理、质子交换、固体酸去角质、聚合和最终 Pt 颗粒浸渍。Pt/xHMNO6/CNT 具有 X 射线衍射、扫描电子显微镜、传输电子显微镜和 NH3温度编程解吸的特点。研究表明，HNbWO6纳米板附着在CNT上，纳米片的一些边缘弯曲成形。支撑Pt催化剂的酸强度按以下顺序增加：Pt/CNTs <Pt/5HNbWO6/CNTs <Pt/20HNbMoO6/CNTs <Pt/20HNbWO6/CNT;Pt/20HT6 /lt;Pt/20HTaWO6/CNTs。此外，还研究了木质素衍生模型化合物的催化转化：使用合成Pt/20HNbWO6催化剂的二苯醚。
Introduction
许多制造化学品的工业过程都涉及使用水无机酸。一个典型的例子是传统的H2SO4工艺，用于水化环己醇，以产生环己醇。该过程涉及双相系统，环己酸二甲苯醚处于有机相，环己醇产物处于酸性水相，因此通过简单的蒸馏使分离过程变得困难。除了分离和回收的困难外，无机酸对设备也具有剧毒和腐蚀性。有时，使用无机酸会产生副产品，从而降低产品产量，必须避免。例如，使用H2 SO4脱水2环己酮-1-ol以生产1，3-环己二烯将导致聚合副产品1。因此，许多工业过程转向使用固体酸催化剂。各种耐水固体酸用于解决上述问题并最大限度地提高产品产量，例如使用 HZSM-5 和 Amberlyst-15。使用高硅HZSM-5沸石已被证明取代H2 SO4在生产环己醇从苯2。由于沸石存在于中性水相中，因此产品将完全进入有机相，从而简化分离过程。然而，由于刘易斯酸碱加法形成水分子到刘易斯酸位点，沸石材料仍然表现出较低的选择性，由于存在非活性位点3。在所有这些固体酸中，Nb2O5是同时含有刘易斯和布伦斯特德酸位的最佳候选体之一。Nb2O5μnH2O 的酸度相当于 70% 的 H2SO4溶液，因为存在实验室质子。与质子沸石材料相当的苯酸度非常高。这种酸度在除水后将转向刘易斯酸度。在存在水的情况下，Nb2O5形成四面体 NbO 4-H2O 加法，这可能会降低刘易斯酸度。然而，刘易斯酸位仍然有效，因为NbO4四面体仍然有有效的正电荷4。这种现象在葡萄糖转化为5-（羟基甲基）fural（HMF）和苯醛与水中四环锡的转化中得到了成功证明。因此，耐水催化剂在可再生能源应用中的生物量转化至关重要，尤其是在水等环境无害溶剂中进行转化时。
在许多环境良性固体酸催化剂中，使用石墨烯、碳纳米管、碳纳米纤维、中孔碳材料的功能化碳纳米材料在生物质的价化中一直发挥着重要的作用。可调孔隙度、极高的特异性表面积和优异的疏水性 6、7。磺化衍生物是特别稳定、活性高的质子催化材料。它们可以通过硫化芳香化合物8的不完全碳化制备，也可以由不完全碳化糖9的硫化制备。它们已被证明是非常高效的催化剂（例如，用于高脂肪酸的酯化），其活性可与使用液体H2 SO4相媲美。石墨烯和CNT是碳材料，具有较大的表面积、优异的机械性能、良好的耐酸性、均匀的孔径分布以及耐焦炭沉积。已发现硫酸石墨烯能有效催化乙酸乙酯10的水解，双功能石墨烯催化剂已发现，促进一锅的乳酸转化为β-瓦列洛酮11。CNT 上支持的双功能金属也是用于生物质转化 12、13的高效催化剂，例如，在 VO 2-PANI/CNT 上将 HMF 高度选择性的有氧氧化为 2，5-二甲基催化剂14.
利用 Nb2O5固体酸、功能化 CNT 和 CNT 上支持的双功能金属的独特特性，我们报告一系列基于 Nb（Ta） 的固体酸纳米板改性 Pt/CNT 的合成协议，具有高表面面积由纳米片聚合方法。此外，我们证明了Pt/20HNbWO6/CNTs，由于从HNbWO6纳米片衍生的分散的Pt粒子和强酸位点的协同效应，在转换中表现出最佳活性和选择性木质素衍生的模型化合物通过水力脱氧转化为燃料。
Protocol
Representative Results
Discussion
用硝酸对CNT进行预处理确实显著增加了特定表面积 （ SBET） .原始CNT具有103m2/g的特定表面积，而经过处理后，表面积增加到134m 2/g。因此，这种预处理在CNT表面产生缺陷，对固体酸改性、铂颗粒浸渍后催化剂的特定表面积有积极影响。由于加入纳米片后表面积会减少，因此这一步骤对于最大化最终催化剂的表面面积至关重要。这是因为在纳米板合并和金属浸渍后，部分表?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
本文件所描述的工作，得到中国香港特别行政区研究资助局（教资会/FDS25/E09/17）的资助。我们还感谢中国国家自然科学基金（21373038和21403026）为催化剂表征提供分析仪器，为催化剂性能评价提供固定床反应器。齐红旭博士感谢香港研究资助局（教资会/FDS25/E09/17）提供的研究助理。
Materials
| Carbon nanotubes (multi-walled) | Sigma Aldrich | 724769 | |
| Nitric acid (65%) | Sigma Aldrich | V000191 | |
| sulphuric acid (98%) | MERCK | 100748 | |
| Lithium carbonate (>99%) | Aladdin | L196236 | |
| Niobium pentaoxide (99.95%) | Aladdin | N108413 | |
| Tungsten trioxide (99.8%) | Aladdin | T103857 | |
| Molybdenum trioxide (99.5%) | Aladdin | M104355 | |
| Tantalum oxide (99.5%) | Aladdin | T104746 | |
| Chloroplatinic acid hexahydrate, ≥37.50% Pt basis | Sigma Aldrich | 206083 | |
| tetra (n-butylammonium) hydroxide 30-hydrate | Aladdin | D117227 | |
| Diphenyl ether, 98% | Aladdin | D110644 | |
| 2-Bromoacetophenone,98% | Aladdin | B103328 | |
| Diethyl ether,99.5% | Sinopharm | 10009318 | |
| n-Decane,98% | Aladdin | D105231 | |
| n-Dodecane,99% | Aladdin | D119697 | |
| Autoclave Reactor | CJF-0.05—0.1L (Dalian Tongda Equipment Technology Development Co., Ltd) | ||
| Tube furnace | SK2-1-10/12 (Luoyang Huaxulier Electric Stove Co., Ltd) |
References
- Jensen, J. L., Uaprasert, V., Fujii, C. R. Acid-Catalyzed Hydration of Dienes. 2. Changes in Activity Coefficient Ratios, Enthalpy, and Entropy as a Function of Sulfuric Acid Concentration. Journal of Organic Chemistry. 41 (10), 1675-1680 (1976).
- Ishida, H., Ono, M., Kaji, S., Watanabe, A. Synthesis of 1,3-Cyclohexadiene through Liquid Phase Dehydration of 2-Cyclohexen-1-ol in Aqueous Solution using Zeolite Catalyst. Nippon Kagaku Kaishi. 4, 267-275 (1997).
- Ishida, H. Liquid-phase hydration process of cyclohexene with zeolites. Catalysis Surveys from Japan. , 241-246 (1997).
- Ushikubo, T., Iizuka, T., Hattori, H., Tanabe, K. Preparation of highly acidic hydrated niobium oxide. Catalysis Today. 16, 291-295 (1993).
- Nakajima, K., et al. Nb2O5.nH2O as a heterogeneous catalyst with water-tolerant Lewis acid sites. Journal of the American Chemical Society. 133 (12), 4224-4227 (2011).
- Lam, E., Luong, J. H. T. Carbon Materials as Catalyst Supports and Catalysts in the Transformation of Biomass to Fuels and Chemicals. ACS Catalysis. 4 (10), 3393-3410 (2014).
- Sudarsanam, P., et al. Functionalised heterogeneous catalysts for sustainable biomass valorisation. Chemical Soceity Review. 47 (22), 8349-8402 (2018).
- Hara, M., et al. A carbon material as a strong protonic acid. Angewandte Chemie International Edition English. 43 (22), 2955-2958 (2004).
- Toda, M., et al. Biodiesel made with sugar catalyst. Nature. 438 (7065), (2005).
- Ji, J., et al. Sulfonated graphene as water-tolerant solid acid catalyst. Chemical Science. 2 (3), 484-487 (2011).
- Wang, Y., et al. Graphene-Based Metal/Acid Bifunctional Catalyst for the Conversion of Levulinic Acid to γ-Valerolactone. ACS Sustainable Chemistry & Engineering. 5 (2), 1538-1548 (2016).
- Ma, Q., et al. Catalytic depolymerization of lignin for liquefied fuel at mild condition by rare earth metals loading on CNT. Fuel Processing Technology. , 220-225 (2017).
- Rahzani, B., Saidi, M., Rahimpour, H. R., Gates, B. C., Rahimpour, M. R. Experimental investigation of upgrading of lignin-derived bio-oil component anisole catalyzed by carbon nanotube-supported molybdenum. RSC Advances. 7 (17), 10545-10556 (2017).
- Guo, Y., Chen, J. Bicomponent Assembly of VO2and Polyaniline-Functionalized Carbon Nanotubes for the Selective Oxidation of Biomass-Based 5-Hydroxymethylfurfural to 2,5-Diformylfuran. ChemPlusChem. 80 (12), 1760-1768 (2015).
- He, J., et al. Characterization of HNbMoO6, HNbWO6 and HTiNbO5 as solid acids and their catalytic properties for esterification reaction. Applied Catalysis A: General. , 145-152 (2012).
- Tagusagawa, C., Takagaki, A., Hayashi, S., Domen, K. Characterization of HNbWO6 and HTaWO6 Metal Oxide Nanosheet Aggregates As Solid Acid Catalysts. Journal of Physical Chemistry C. 113, 7831-7837 (2009).
- Niwa, M., Katada, N., Sawa, M., Murakami, Y. Temperature-Programmed Desorption of Ammonia with Readsorption Based on the Derived Theoretical Equation. Journal of Physical Chemistry. 99, 8812-8816 (1995).
- Leiva, K., et al. Conversion of guaiacol over supported ReOx catalysts: Support and metal loading effect. Catalysis Today. , 228-238 (2017).
- Deng, W., Liu, M., Tan, X., Zhang, Q., Wang, Y. Conversion of cellobiose into sorbitol in neutral water medium over carbon nanotube-supported ruthenium catalysts. Journal of Catalysis. 271 (1), 22-32 (2010).
- Huang, B., Huang, R., Jin, D., Ye, D. Low temperature SCR of NO with NH3 over carbon nanotubes supported vanadium oxides. Catalysis Today. 126 (3-4), 279-283 (2007).
- Takagaki, A., Tagusagawa, C., Hayashi, S., Hara, M., Domen, K. Nanosheets as highly active solid acid catalysts for green chemical syntheses. Energy & Environmental Science. 3 (1), 82-93 (2010).
- Hu, L. -. F., et al. Structure and photocatalytic performance of layered HNbWO6nanosheet aggregation. Journal of Nanophotonics. 9 (1), (2015).
- Geim, A. K. Graphene: Status and Prospects. Science. 324, 1530-1534 (2009).
- Golberg, D., et al. Boron Nitride Nanotubes and Nanosheets. ACS Nano. 4 (6), 2979-2993 (2010).
- Wilson, J. A., Yoffe, A. D. The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties. Advances in Physics. 18 (73), 193-335 (1969).
- Ma, R., Sasaki, T. Nanosheets of oxides and hydroxides: Ultimate 2D charge-bearing functional crystallites. Advanced Materials. 22 (45), 5082-5104 (2010).
- Pope, T. R., Lassig, M. N., Neher, G., Weimar Iii, R. D., Salguero, T. T. Chromism of Bi2WO6 in single crystal and nanosheet forms. Journal of Materials Chemistry C. 2 (17), 3223-3230 (2014).
- Yu, Y., et al. Controlled scalable synthesis of uniform, high-quality monolayer and few-layer MoS2 films. Scientific Reports. 3, 1866 (2013).
- Prasomsri, T., Shetty, M., Murugappan, K., Román-Leshkov, Y. Insights into the catalytic activity and surface modification of MoO3 during the hydrodeoxygenation of lignin-derived model compounds into aromatic hydrocarbons under low hydrogen pressures. Energy & Environmental Science. 7 (8), 2660-2669 (2014).
