Showing papers by "Angelika Brückner published in 2003"
TL;DR: In this article, the authors showed that some level of association of iron species leads to higher activities in direct N 2 O decomposition, rather than the existence of a unique active site.
128 citations
TL;DR: In this article, a review of multitechnique approaches for in situ studies of real heterogeneous catalysts during conditioning, reaction, and deactivation processes is presented, with the aim to point out the particular benefits that arise from multitone approaches for understanding processes like formation of active sites, interaction of those sites with reactant molecules, and catalyst deactivation.
Abstract: Adapting physico-chemical characterization techniques for in situ studies of real heterogeneous catalysts during conditioning, reaction, and deactivation processes is a research topic of growing importance. Up to now, in most studies only one single in situ technique is applied. However, new trends are focused on using a portfolio of several in situ methods to obtain comprehensive information on structure-reactivity relationships. This review discusses such application examples with the aim to point out the particular benefits that arise from multitechnique approaches for understanding processes like formation of active sites, interaction of those sites with reactant molecules, and catalyst deactivation. Except for Fourier-transform infrared spectroscopy and quasi-in situ X-ray photoelectron spectroscopy, the examples deal mainly with the combined use of bulk techniques such as electron paramagnetic resonance, ultraviolet/visible diffuse reflection spectroscopy, laser-Raman spectroscopy, temperature-progr...
108 citations
TL;DR: In this paper, the properties of transition metal oxide (TMI) catalysts are analyzed using Operando EPR, which provides simultaneous information on valence state, coordination geometry and electronic interactions of paramagnetic TMI.
Abstract: Tailoring the properties of transition metal oxide catalysts so as to provide optimum performance for the desired reaction is a major goal in catalysis research that can only be reached by deep understanding of structure–reactivity relationships of active sites. Operando EPR is a versatile tool for that purpose since it provides simultaneous information on valence state, coordination geometry and electronic interactions of paramagnetic TMI in relation to activity and selectivity of the catalysts. This is demonstrated by illustrative examples comprising the action of different TMI: (i) structure and function of V ions in vanadia-based catalysts used for the oxidative dehydrogenation of propane to propene (ODP) and the selective oxidation of toluene to benzaldehyde; (ii) activity and stability of Cr sites in supported chromium oxides during dehydrogenation of propane; (iii) structure and function of Mn ions in MnOx storage catalysts for selective catalytic reduction of NOx. Benefits arising from combined operando EPR/UV-vis/on-line GC studies are also shown. This combination provides an excellent opportunity to monitor the reaction-dependent interconversion of diamagnetic and paramagnetic TMI.
39 citations
TL;DR: In this article, the interaction of NO, NO 2, H 2 O, SO 2 and NH 3 with supported MnO 2 /NaY used as storage catalyst in the SCR of NO x has been studied as a function of temperature between 20°C and 500°C by in situ EPR, in situ FTIR and quasi-in situ XPS.
Abstract: The interaction of NO, NO 2 , H 2 O, SO 2 and NH 3 with supported MnO 2 /NaY used as storage catalyst in the SCR of NO x has been studied as a function of temperature between 20°C and 500°C by in situ -EPR, in situ -FTIR and quasi-in situ -XPS.
1 citations
Patent•
12 Feb 2003
TL;DR: In this paper, a mixed oxide catalyst was used for the gas phase production of nitriles by ammonoxidation and is based on antimony (Sb) and vanadium (V) oxides.
Abstract: Regeneration of a mixed oxide catalyst, which has been used in the gas phase production of nitriles by ammonoxidation and is based on antimony (Sb) and vanadium (V) oxides, comprises passing gas containing oxygen and free from reducing compounds over the deactivated catalyst at 300-900[deg]C. An independent claim is also included for the production of 3-cyanopyridine by reacting 3-methylpyridine with ammonia and oxygen, using a heterogeneous mixed oxide catalyst based on Sb and V oxides and then regenerating the deactivated catalyst as above.
1 citations