Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, Netherlands.
Chemistry. 2012 Feb 6;18(6):1800-10. doi: 10.1002/chem.201102151. Epub 2012 Jan 3.
New routes for the preparation of highly active TiO(2)-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, (63)Cu nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO(2) catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO(2) at 120 °C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO(2) at 140 °C, corresponding to an initial reaction rate of 104 mmol g(cat) (-1) s(-1). The activation energy on the Cu/mesoporous TiO(2) catalyst was found to be (144±5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123±3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO(2) support (75±2 kJ mol(-1)).
已经开发出用于 C-O 偶联反应的高度活性 TiO2 负载的 Cu 和 CuZn 催化剂的新制备路线。将钛酸盐前体的浆料浸渍到玻璃珠上，以获得结构化的介孔或无孔 TiO2 薄膜。使用溶剂还原法合成的 Cu 和 CuZn 纳米粒子被沉积在煅烧的薄膜上，以获得 2wt%的 Cu 负载量。通过电感耦合等离子体（ICP）光谱法、程序升温氧化/还原（TPO/TPR）技术、（63）Cu 核磁共振（NMR）光谱法、X 射线衍射（XRD）、扫描和透射电子显微镜（S/TEM-EDX）和 X 射线光电子能谱（XPS）对催化剂进行了表征。在 4-氯吡啶和苯酸钾的 C-O 乌尔曼偶联反应中，研究了所获得的催化剂的活性和稳定性。负载在 TiO2 上的纳米颗粒在长达 12 小时的时间内保持催化剂活性。然而，由于 Cu 纳米粒子的氧化，在更长的操作时间内观察到催化剂失活。由于 Zn 的存在，CuZn/TiO2 催化膜上的氧化速率可以显著降低。在 120°C 时，Cu/无孔 TiO2 上的 4-苯氧基吡啶的产率为 64%。在 140°C 时，Cu/介孔 TiO2 上的产物产率最高，为 84%，对应于初始反应速率为 104mmol g(cat) (-1) s(-1)。在 Cu/介孔 TiO2 催化剂上的活化能被发现为（144±5）kJ mol(-1)，这与无载体 CuZn 纳米粒子上的反应获得的值（123±3）kJ mol(-1)接近，几乎是负载在无孔 TiO2 载体上的催化剂观察到的值（75±2）kJ mol(-1)的两倍。
