Novel Deacon-like Process of HCl-Oxidation Catalyzed by RuO2

直到最近，住友化学才开发出一种高效稳定的Deacon型工艺，用于在RuO 2上用空气多相催化氧化HCl，生成Cl 2和水（住友工艺）[1]。Sumitomo工艺允许在工业（氯相关）化学中设计封闭的工艺循环，其中氯从副产物氯化氢中回收，几乎没有额外的能源成本。本项目的主要目标是在原子尺度上对单晶RuO_2（110）模型催化剂上氧催化氧化HCl的反应机理进行全面表征，包括确定催化剂的催化活性状态和基元反应步骤，确定活化势垒和相应的过渡态。我们将应用各种原位技术（包括红外光谱-RAIRS，表面X射线衍射-SXRD和质谱-MS）和密度泛函理论（DFT）计算，以确定在催化HCl氧化反应过程中的表面上的反应中间体，并确定RuO 2催化剂的催化活性状态。从我们小组的初步实验中，有证据表明，工作的RuO 2（110）模型催化剂由RuO 2-xClx（110）组成。特别注意RuO_（2-x）Cl_x（110）在反应2 HCl + 1/2 O_2 → Cl_2 + H_2 O中的作用。工作催化剂RuO 2-xClx（110）的原子表面结构将通过低能电子衍射（LEED）和DFT计算来确定。同样重要的是RuO 2-xClx（110）催化剂在反应条件下的结构和化学稳定性，这将通过原位表面X射线衍射来研究。通过DFT计算和光电子能谱，将氯化RuO 2（110）表面的电子性质与RuO 2（110）表面的电子性质进行比较，以及电子结构中的这些修饰如何影响催化剂表面的化学反应性。用钠作为典型的助催化剂（注意，NaCl被认为是Deacon类方法中有前途的助催化剂），可以调节催化剂的电子性质，从而调节催化活性。这种促进剂效应也应该通过PES和DFT计算来研究。更深入地理解为什么RuO 2（110）是用于HCl氧化的如此有效的催化剂，可以引发对改进的催化剂材料/化合物的合理搜索。

Only very recently Sumitomo chemicals have developed an efficient and stable Deacon-like process for the heterogeneously catalyzed oxidation of HCl with air over RuO2 producing Cl2 and water (Sumitomo process) [1]. The Sumitomo process allows to design closed process cycles in industrial (chlorine-related) chemistry in which chlorine is recycled from the byproduct hydrogen chloride almost without additional energy cost. The main objective of this project is the comprehensive characterization of the reaction mechanism of the catalyzed HCl oxidation by oxygen over single-crystalline RuO2(110) model catalyst on the atomic scale, including the identification of the catalytically active state of the catalyst and of the elementary reaction steps, the determination of activation barriers and the corresponding transition states. We shall apply various in-situ techniques (including infrared spectroscopy-RAIRS, surface x-ray diffraction-SXRD and mass spectrornetry-MS) and density functional theory (DFT) calculations to identify the reaction intermediates on the surface during the catalyzed HCl oxidation reaction and to determine the catalytically active state of the RuO2 catalyst. From preliminary experiments in our group there is evidence that the working RuO2(110) model catalyst consists of RuO2-xClx(110). Particular attention will be drawn to the role of RuO2-xClx(110) in the reaction 2HCl + 1/2O2 → CI2 + H2O. The atomic surface structure of the working catalyst RuO2-xClx(110) will be determined by low energy electron diffraction (LEED) and DFT calculations. Equally important is the structural and chemical stability of the RuO2-xClx(110) catalyst under reaction conditions which will be studied by in situ-surface x-ray diffraction. With DFT calculations and photoelectron spectroscopy the electronic property of the chlorinated RuO2(110) surface will be compared to that of RuO2(110) and how these modifications in the electronic structure influence the chemical reactivity of the catalyst's surface. With sodium as a typical promoter (note that NaCl is considered as a promising co-catalyst in Deacon-like processes) one may tune the electronic properties of the catalyst and thereby the catalytic activity. This promoter effect should be studied by PES and DFT calculations as well. A deeper understanding why RuO2(110) is such an efficient catalyst for the oxidation of HCl may trigger a rational search for an improved catalyst materials/ compounds.