Carbon-covered Alumina: A Superior Support of Noble Metal-like Catalysts for Hydrazine Decomposition
- PDF / 551,523 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 88 Downloads / 190 Views
Carbon-covered Alumina: A Superior Support of Noble Metal-like Catalysts for Hydrazine Decomposition Mingyuan Zheng Æ Yuying Shu Æ Jun Sun Æ Tao Zhang
Received: 24 July 2007 / Accepted: 4 October 2007 / Published online: 20 October 2007 Ó Springer Science+Business Media, LLC 2007
Abstract Carbon-covered alumina (CCA) were synthesized from mesoporous alumina and a series of carbon sources (including sucrose, furfuryl alcohol, and benzene). They had structural properties of alumina and surface characteristics of carbon. When they were used as supports for molybdenum carbide, nitride, and phosphide catalysts, significantly higher activities were obtained in hydrazine decomposition as compared to those supported on the conventional alumina. The difference in the interactions of catalytic active sites with the CCA and with the alumina supports was preliminarily deemed to be the main cause of the better performance of CCA supported catalysts. Carbon contents on alumina and carbon sources were found to be important for CCA to be a good support. Carbon deposited on alumina in a near monolayer form showed the best activities. In contrast with sucrose and furfuryl alcohol, benzene as the carbon source readily yielded CCA supports with a hydrophobic surface, which resulted in relatively low dispersions of metal and, in turn, decreased activity of the supported catalysts. Keywords Hydrazine decomposition Carbon covered alumina Carbide Nitride Phosphide
M. Zheng Y. Shu J. Sun T. Zhang (&) Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China e-mail: [email protected] Y. Shu e-mail: [email protected]
123
1 Introduction Hydrazine catalytic decomposition has important applications in attitude control of spacecrafts, in which Ir/Al2O3 is usually used as a catalyst. Transition metal interstitial compounds, including carbides, nitrides, and phosphides, behave noble metal-like in many reactions involving hydrogen transfer [1–3]. They have been found to be promising substitutes for the rare and expensive iridium in N2H4 decomposition [4–6]. For instance, the supported catalysts Mo2C/Al2O3 and Mo2N/Al2O3 reported by Chen et al. showed high performances in hydrazine thrusters at 100 °C [7, 8]. However, at lower temperatures, these noble metal-like catalysts presented activities needing further improvement for future applications. Support is very important for a catalyst, as the support determines the catalytic performance from micro and macro aspects. This is especially true for hydrazine decomposition. In this process catalysts endure high temperature, high pressure, and rapid flushing with reactant and products at high velocities. Alumina has been conventionally used as a support for this reaction due to its various advantages in terms of high surface areas, numerous pores, and strong mechanical strength. On the other hand, it also has some potentially detrimental characteristics. For example, its strong interactions with metal atoms might cause a decrease in catalytic activity. The a
Data Loading...
