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首页> 外文期刊>Catalysis science & technology >A transient in situ infrared spectroscopy study on methane oxidation over supported Pt catalysts
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A transient in situ infrared spectroscopy study on methane oxidation over supported Pt catalysts

机译：一项关于甲烷氧化的瞬时原位红外光谱研究，在受支持的PT催化剂上

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摘要

Catalysts with platinum dispersed on alumina, ceria and mixed alumina-ceria have been prepared by incipient wetness impregnation, characterized with transmission electron microscopy and X-ray diffraction, and evaluated for total oxidation of methane under both stationary and transient gas compositions (oxygen pulsing). Further, in situ diffuse reflectance Fourier transformed infrared spectroscopy has been used to monitor the evolution of surface species during precise transient gas composition changes using high-speed gas switching valves. The results show that platinum has a sufficiently strong interaction with all the supports so as to form small platinum particles. The smallest sizes are observed for the Pt/Ce sample. The alumina containing samples show, in contrast to the Pt/Ce sample, a decreased methane conversion with increasing oxygen concentration and a clear kinetic bistability between increasing and decreasing oxygen concentrations. The bistable kinetics is likely connected to oxidation and reduction of platinum occurring for different stoichiometric gas mixtures depending on the history of the system, for which an oxidation of the platinum particles effectively inhibits the dissociative adsorption of methane leading to a low reaction rate. It is shown for the alumina containing samples that the adverse effects of oxygen excess can be circumvented by the use of periodic operation so that the average methane conversion is improved. Further, the Pt/Ce sample seems to exhibit additional active sites at the platinum-ceria interface explaining the generally higher conversion of methane for this sample.
机译：通过初期湿度浸渍制备了分散在氧化铝，陶瓷和混合氧化铝壁的催化剂，以透射电子显微镜和X射线衍射为特征，并评估了在固定气体和瞬态气体成分（氧气脉冲）下的甲烷总氧化。此外，使用高速气体开关阀在精确的瞬态气体组成变化过程中，已使用原位弥漫性傅立叶转化红外光谱法监测表面物种的演变。结果表明，铂与所有支撑物具有足够强的相互作用，以形成小铂颗粒。对于PT/CE样品，观察到最小的尺寸。与PT/CE样品相比，包含氧化铝的样品表明，甲烷转化率降低，氧气浓度的升高和氧气浓度的增加和降低的动力学双重性。双态动力学可能与不同化学计量的气体混合物的氧化和减少有关，具体取决于系统的史，为此，铂颗粒的氧化有效地抑制了甲烷的解离，导致低反应速率。对于包含样品的氧化铝显示，可以通过定期操作来规避氧气过量的不利影响，从而改善了平均甲烷转化率。此外，PT/CE样品似乎在铂谷媒体界面上表现出其他活性位点，该位点解释了该样品的甲烷通常更高的转化率。

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