Rational design of vanadia based catalysts for SCR of NOx using advanced X-ray spectroscopic techniques
Sponsor: Haldor Topsøe A/S
Supervisors: Prof. dr. Frank de Groot and dr. Anna Puig Molina (Haldor Topsøe A/S)
Nitrogen oxides (NOx) are environmentally harmful byproducts of the combustion of fossil- and biofuels. NOx can be efficiently removed from waste gas streams by means of reduction by ammonia and oxygen to yield N2 and water in a process called selective catalytic reduction (SCR). The commercial SCR catalyst is based on supported vanadium oxide V2O5/TiO2 (anatase) formulations. To address current and future environmental challenges there is a need to develop better catalysts. A better understanding of the catalytic system is however needed to allow for the rational design of these new catalysts.
Advanced X-ray spectroscopic techniques (XAS and RIXS), both in- and ex situ, will be used to gain a better understanding of the SCR catalyst. X-ray absorption spectroscopy (XAS) can give chemical and structural information and is a suitable technique to study oxidation state and local geometry of the catalyst. Resonant inelastic X-ray scattering (RIXS) is a photon-in photon-out spectroscopy that allows for the acquisition of valence or site selective XAS spectra. In addition, RIXS data can be used to generate element, valence or site specific optical spectra. Together with electronic structure calculations, XAS and RIXS allow for a detailed study of the electronic structure, the geometry and the intermolecular interactions in the catalyst.
The aim of this project is to elucidate the role of the catalyst-support interactions; the role of promoter species (WO3, MoO3) and the effect of alkali poisoning on the electronic structure and geometry of the catalyst and how this effects the activity. In a later stage the information gained will be used to design new SCR catalysts.