larger picture

larger picture

larger picture

Publications

Below are some recent examples of publications from The Competence Centre for Catalysis. A complete list in pdf format can be found on the link below.

Publications.pdf

NO2 dissociation on Ag(111) revisited by theory

Anders Hellman, Itai Panas and Henrik Grönbeck
Journal of Chemical Physics 128 (2008) 104704 .

Selective catalytic reduction using hydrocarbons (HC-SCR) as reducing agent is a promising technique. In particular, silver (Ag) supported on alumina has shown high activity as HC-SCR catalyst. The role of Ag in this catalyst is presently unclear and studies of adsorption and reaction of NOx on single crystal surfaces may provide understanding of relevant reaction mechanisms.

In order to address the details of adsorption and dissociation of NO2 on Ag(111), we report an extensive first-principles study of O, NO, (NO)2, NO2 and NO3 on Ag(111). For single NO2 molecules, a high adsorption potential energy is found to prohibit dissociation. This result is surprising as experiments indicate dissociation at low temperatures. Neither entropy effects nor irregularities in the potential energy surface can remedy the discrepancy. Instead it is proposed that collective Eley-Rideal type of reaction mechanisms can drive the dissociation.

Structural, Energetic and Vibrational Properties of NOx adsorption on Agn, n=1-8

Henrik Grönbeck, Anders Hellman and Andreas Gavrin
Journal of Physical Chemistry A, 111(27) (2007) 6062-6067.

It has recently been suggested that the active metal phase in the Ag/Al2O3 catalyst for selective catalytic reduction of NOx with hydrocarbons is small Agn clusters. To investigate on this the density functional theory was used to explore NO, NO2 and     NO3 adsorption on Agn, with n=1-8. The binding energies for all adsorbates show a marked odd/even alternation with a stronger bonding to odd clusters. Such variations are also present in vibrational properties of the adsorbed radicals.

Mechanistic Aspects of Lean NO2 Reduction by Propane over HZSM-5

Hanna Härelind Ingelsten, Anders Palmqvist and Magnus Skoglundh
Topics in Catalysis 42-43 (2007) 105.

In this study we show that the lean NO2 reduction with isopropylamine proceeds in a rapid reaction over HZSM-5. This reaction most probably occurs over Brønsted acid sites where isopropylamine-derived species reacts with nitrosonium ions (NO+). The amine species are likely formed by a hydrolysis reaction of isocyanate species and water, which is supported by the results in this investigation. Formation of isocyanate species, in turn, may take place via surface reactions of NO+ species and carbenium ion adsorbates and/or alkenes.