Bruk Lev, Titov Denis, Ustyugov Alexander, Zubavichus Yan, Chernikova Valeriya, Tkachenko Olga, Kustov Leonid, Murzin Vadim, Oshanina Irina, Temkin Oleg
Moscow Technological University, Institute of Fine Chemical Technology, Department of General Chemical Technology, Moscow 119571, Russia.
National Research Centre "Kurchatov Institute", Moscow 123182, Russia.
Nanomaterials (Basel). 2018 Apr 3;8(4):217. doi: 10.3390/nano8040217.
The state of palladium and copper on the surface of the PdCl₂-CuCl₂/γ-Al₂O₃ nanocatalyst for the low-temperature oxidation of CO by molecular oxygen was studied by various spectroscopic techniques. Using X-ray absorption spectroscopy (XAS), powder X-ray diffraction (XRD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), freshly prepared samples of the catalyst were studied. The same samples were also evaluated after interaction with CO, O₂, and H₂O vapor in various combinations. It was shown that copper exists in the form of Cu₂Cl(OH)₃ (paratacamite) nanophase on the surface of the catalyst. No palladium-containing crystalline phases were identified. Palladium coordination initially is comprised of four chlorine atoms. It was shown by XAS that this catalyst is not capable of oxidizing CO at room temperature in the absence of H₂O and O₂ over 12 h. Copper(II) and palladium(II) are reduced to Cu(I) and Pd(I,0) species, respectively, in the presence of CO and H₂O vapor (without O₂). It was found by DRIFTS that both linear (2114 cm, 1990 cm) and bridging (1928 cm) forms of coordinated CO were formed upon adsorption onto the catalyst surface. Moreover, the formation of CO₂ was detected upon the interaction of the coordinated CO with oxygen. The kinetics of CO oxidation was studied at 18-38 °C at an atmospheric pressure for CO, O₂, N₂, and H₂O (gas) mixtures in a flow reactor (steady state conditions).
通过各种光谱技术研究了用于一氧化碳低温氧化的PdCl₂-CuCl₂/γ-Al₂O₃纳米催化剂表面钯和铜的状态。使用X射线吸收光谱（XAS）、粉末X射线衍射（XRD）和漫反射红外傅里叶变换光谱（DRIFTS）对新鲜制备的催化剂样品进行了研究。还对相同的样品在与一氧化碳、氧气和水蒸气以各种组合相互作用后进行了评估。结果表明，铜以Cu₂Cl(OH)₃（副氯铜矿）纳米相的形式存在于催化剂表面。未鉴定出含钯的晶相。钯最初的配位由四个氯原子组成。XAS表明，在没有水和氧气的情况下，该催化剂在室温下12小时内无法氧化一氧化碳。在一氧化碳和水蒸气（无氧气）存在下，铜（II）和钯（II）分别还原为Cu（I）和Pd（I,0）物种。通过DRIFTS发现，吸附在催化剂表面时会形成线性（2114 cm，1990 cm）和桥式（1928 cm）配位一氧化碳形式。此外，检测到配位一氧化碳与氧气相互作用时会形成二氧化碳。在流动反应器（稳态条件）中，在1个大气压下，于18-38℃研究了一氧化碳、氧气、氮气和水蒸气（气体）混合物中一氧化碳氧化的动力学。
