In situ studies of the oxidation of HCl over RuO2 model catalysts: Stability and reactivity

• Published in: Journal of catalysis Vol. 272; no. 1; pp. 169 - 175
• Main Authors: ZWEIDINGER, S, HOFMANN, J. P, BALMES, O, LUNDGREN, E, OVER, H
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 25.05.2010; Elsevier BV
• Subjects: Atom and Molecular Physics and Optics; Atom- och molekylfysik och optik; Catalysis; Chemical reactions; Chemistry; Deacon process; Exact sciences and technology; Fysik; General and physical chemistry; Heterogeneous catalysis; In situ SXRD; Natural Sciences; Naturvetenskap; Oxidation; Physical Sciences; Reactivity; RuO2; Stability; Surfaces; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Stability; In situ; Active site; Surfaces; Oxides; X ray diffraction; RuO; Thickness; Chemical reduction; Heterogeneous catalysis; Partial pressure; Reactivity; Frequency; Models; Oxidation; Reactor; Chemical reactivity; Structure; Mass spectrometry; In situ SXRD; Catalyst; Deacon process
• ISSN: 0021-9517; 1090-2694; 1090-2694
• DOI: 10.1016/j.jcat.2010.02.030

In situ surface X-ray diffraction reveals that RuO2 -model catalysts are long-term stable for the HCl oxidation reaction by oxygen with a mean TOF of 0.6s-1 for Cl2 using a batch reactor. Structure-activity experiments were performed for the HCl oxidation reaction (Deacon-like process) over RuO2 model catalysts - RuO2 (110) and RuO2 (100) - applying in situ surface X-ray diffraction (SXRD) combined with on-line mass spectrometry. The studied model catalysts turned out to be long-term stable under reaction conditions with gas feed ratios p(HCl):p(O2 ) ranging from 1:4 to 4:1 in the mbar pressure regime and temperatures as high as 685K. Even pure HCl exposure in the mbar regime was not able to reduce RuO2 below 600K; above 650K chemical reduction of the oxide sets in. Under strongly oxidizing reaction conditions, the (surface) oxides grow slowly in thickness. On-line reactivity experiments of both types of model catalysts in a batch reactor yield a mean turn-over frequency (TOF) of 0.6Cl 2 molecules per second and active site for the HCl oxidation at 650K and initial partial pressures of p(HCl)=2mbar and p(O2 )=0.5mbar. The HCl oxidation over RuO2 is therefore considered to be structure insensitive. [PUBLICATION ABSTRACT]