On the role of H2 to modify surface NOx species over Ag-Al2O3 as lean NOx reduction catalyst: TPD and DRIFTS studies
Journal article, 2015

Formation and stability of surface NOx species related to the promotional effect of H2 over Ag–Al2O3 as NOx reduction catalyst were investigated with temperature-programmed desorption and DRIFT spectroscopy. Formation of two groups of surface NOx species was found: a less thermally stable group of “low temperature (LT) species” and a more thermally stable group of “high temperature (HT) species”. The LT NOx was attributable to the decomposition of surface NOx species formed on the active sites where its elimination by addition of H2 or thermal decomposition correlated with higher NO oxidation and NOx reduction conversion. Under reaction conditions, these possibly inhibiting LT NOx species were stable up to about 300 °C and their formation depended on donation of oxygen from surface oxides. Removal of LT nitrate species by H2 accounted for only a fraction of the increased NO oxidation and NOx reduction conversion by co-feeding H2. Furthermore, it was also found that H2 facilitates formation of HT NOx that primarily corresponded to the decomposition of spectator species on the Al2O3 support identified as monodentate nitrate species. From TPD studies of C3H6-SCR, it was shown that H2 not only eliminated LT NOx but also promoted formation of greater quantities of adsorbed hydrocarbons.

HC-SCR

DRIFT

NOx reduction

TPD

Hydrogen effect

Silver alumina

Author

Muhammad Mufti Azis

Competence Centre for Catalysis (KCK)

Chalmers, Chemistry and Chemical Engineering, Chemical Technology, Chemical Reaction Engineering

Hanna Härelind

Competence Centre for Catalysis (KCK)

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Applied Surface Chemistry

Derek Creaser

Chalmers, Chemistry and Chemical Engineering, Chemical Technology, Chemical Reaction Engineering

Catalysis Science and Technology

2044-4753 (ISSN) 2044-4761 (eISSN)

Vol. 55 1 296-309

Model development for heterogeneous catalytic reactors

Swedish Research Council (VR), 2012-01-01 -- 2014-12-31.

Areas of Advance

Transport

Subject Categories

Chemical Process Engineering

Chemical Sciences

DOI

10.1039/C4CY00816B

More information

Created

10/8/2017