Enhancing ammonia storage by tailoring zeolite doping
Typ
Examensarbete för masterexamen
Program
Applied physics (MPAPP), MSc
Publicerad
2020
Författare
Schörling, David
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Selective catalytic reduction with NH3 as a reducing agent (NH3-SCR) is currently
the most widely used technology to reduce NOx emissions from automotive diesel
engines. One of the most prevalent types of catalysts for this purpose is zeolites.
The technology requires storage of NH3 in the zeolites over a large temperature
range. NH3 is stored by adsorption to H+ Brønsted acid sites and other counter
ions.
In this thesis, adsorption of NH3 in the zeolites CHA, BEA and MFI and the zeolite
like structure AlPO have been investigated using density functional theory (DFT).
In all cases, the effect of doping the zeolite framework was explored. Calculations
were performed for four different dopant atoms and the counter ions H+, Cu(I),
Cu(II) and Cu(II) with (OH)− adsorbed. It was found that the type of dopant atom
has a clear effect on the adsorption energies of NH3 on H+ and Cu(II), while the
effect is less noticeable in the cases of Cu(I) and Cu(II) with (OH)− adsorbed. The
type of zeolite was also found to largely influence the results. The effect of different
Al dopant distributions in CHA was also explored. It was found that the relative
positions of the dopant atoms have a considerable impact on the adsorption energies.
Beskrivning
Ämne/nyckelord
AlPO , BEA , catalysis , CHA , Cu , DFT , Al distribution , MFI , NH3 , NOx , SCR , temperature programmed desorption , zeolites