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

• Applicant: Professor Dr. Herbert Over
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 60700559

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.

• DFG Programme: Research Grants
• Major Instrumentation: Massenspektrometer mit Molekularstrahlen
• Instrumentation Group: 1700 Massenspektrometer