Chen Lifang, Hu Juncheng, Richards Ryan M
Department of Chemistry and Geochemistry, Colorado School of Mines, Golden CO 80401, USA.
Chemphyschem. 2008 May 16;9(7):1069-78. doi: 10.1002/cphc.200800041.
Nanoscale iron-doped zirconia solid-solution aerogels are prepared via a simple ethanol thermal route using zirconyl nitrate and iron nitrate as starting materials, followed by a supercritical fluid drying process. Structural characteristics are investigated by means of powder X-ray diffraction (XRD), thermal analyses (TG/DTA), N(2) adsorption measurements and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results show that the resulting iron-doped solid solutions are metastable tetragonal zirconia which exhibit excellent dispersibility and high solubility of iron oxide. Further, when the Fe:(Fe+Zr) ratio x is lower than 0.10, all of the Fe(3+) ions can be incorporated into ZrO(2) by substituting Zr(4+) to form Zr(1-) (x)Fe(x)O(y) solid solutions. Moreover, for the first time, an additional hydroxyl group band that is not present in pure ZrO(2) is observed by DRIFTS for the Zr(Fe)O(2) solid solution. This is direct evidence of Fe(3+) ions incorporated into ZrO(2). These Zr(1-) (x)Fe(x)O(y) solid solutions are excellent catalysts for the solvent-free aerobic oxidation of n-hexadecane using air as the oxidant under ambient conditions. The Zr(0.8)Fe(0.2)O(y) solid-solution catalyst demonstrates the best catalytic properties, with the conversion of n-hexadecane reaching 36.2 % with 48 % selectivity for ketones and 24 % selectivity for alcohols and it can be recycled five times without significant loss of activity.
通过简单的乙醇热法，以硝酸氧锆和硝酸铁为起始原料制备了纳米级铁掺杂氧化锆固溶体气凝胶，随后进行超临界流体干燥过程。通过粉末X射线衍射（XRD）、热分析（TG/DTA）、N₂吸附测量和漫反射红外傅里叶变换光谱（DRIFTS）研究了结构特征。结果表明，所得的铁掺杂固溶体是亚稳四方氧化锆，其表现出优异的分散性和氧化铁的高溶解度。此外，当Fe:(Fe+Zr)比x低于0.10时，所有的Fe³⁺离子可以通过取代Zr⁴⁺掺入ZrO₂中，形成Zr₁₋ₓFeₓOᵧ固溶体。此外，首次通过DRIFTS观察到Zr(Fe)O₂固溶体中存在纯ZrO₂中不存在的额外羟基带。这是Fe³⁺离子掺入ZrO₂的直接证据。这些Zr₁₋ₓFeₓOᵧ固溶体是在环境条件下以空气为氧化剂对正十六烷进行无溶剂好氧氧化的优异催化剂。Zr(0.8)Fe(0.2)Oᵧ固溶体催化剂表现出最佳的催化性能，正十六烷的转化率达到36.2%，酮的选择性为48%，醇的选择性为24%，并且可以循环使用五次而活性没有明显损失。
