Xi Yan, Reed Corey, Lee Yong-Kul, Oyama S Ted
Environmental Catalysis and Nanomaterials Laboratory, Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA.
J Phys Chem B. 2005 Sep 22;109(37):17587-96. doi: 10.1021/jp052930g.
Supported manganese oxide catalysts were prepared by the impregnation of alumina foam blocks washcoated with alumina and silica. The manganese content based on the weight of the washcoats was 10 wt % calculated as MnO2. Fourier transform profiles of the Mn K-edge EXAFS spectra for these samples gave three distinctive peaks at 0.15, 0.25, and 0.32 nm and were close to the profiles of Mn3O4 and beta-MnO2. The number of surface active sites was determined through oxygen chemisorption measurements at a reduction temperature (Tred = 443 K) obtained from temperature-programmed reduction (TPR) experiments. Acetone catalytic oxidation was studied from room temperature to 573 K, and was found to be highly accelerated by the use of ozone on both catalysts with substantial reductions in the reaction temperature. The only carbon-containing product detected was CO2. The alumina-supported catalyst was found to be more active than the silica-supported catalyst in acetone and ozone conversion, with higher turnover frequencies (TOFs) for both reactions. The pressure drop through the foam was low and increased little (0.003 kPa/10 000 h(-1)) with space velocity. In situ steady-state Raman spectroscopy measurements during the acetone catalytic oxidation reaction showed the presence of an adsorbed acetone species with a C-H bond at 2930 cm(-1) and a peroxide species derived from ozone with an O-O bond at 890 cm(-1).
通过用氧化铝和二氧化硅对泡沫氧化铝块进行涂覆后浸渍来制备负载型氧化锰催化剂。以MnO₂计算，基于涂层重量的锰含量为10 wt%。这些样品的Mn K边扩展X射线吸收精细结构（EXAFS）光谱的傅里叶变换谱在0.15、0.25和0.32 nm处给出三个明显的峰，并且与Mn₃O₄和β-MnO₂的谱接近。通过在程序升温还原（TPR）实验获得的还原温度（Tred = 443 K）下进行氧化学吸附测量来确定表面活性位点的数量。研究了从室温到573 K的丙酮催化氧化，发现使用臭氧时两种催化剂上的反应均被高度加速，反应温度大幅降低。检测到的唯一含碳产物是CO₂。发现在丙酮和臭氧转化中，氧化铝负载的催化剂比二氧化硅负载的催化剂更具活性，两种反应的周转频率（TOF）更高。通过泡沫的压降很低，并且随着空速增加很小（0.003 kPa/10 000 h⁻¹）。丙酮催化氧化反应过程中的原位稳态拉曼光谱测量表明，存在一个在2930 cm⁻¹处有C-H键的吸附丙酮物种和一个在890 cm⁻¹处有O-O键的源自臭氧的过氧化物物种。
