Skip to main content
European Commission logo print header
Inhalt archiviert am 2022-12-23

The nature of sulfated zirconia strong acidity

Ziel

Two main problems are usually met in studies of sulfated zirconia based catalysts for alkanes isomerisation. One problem is that all attempts to register the so-called "superacid" sites on the catalyst surface with standard techniques failed up to now. Another problem is the bulk character of these catalysts, not allowing one to extract reliable data about the active sulfated zirconia surface with conventional physical and chemical methods.
It is possible to solve both problems by preparing finely dispersed sulfated zirconia on a support. However, the small clusters of sulfated zirconia strongly interact with the supports. This interaction essentially changes the electronic structure of sulfated zirconia and its properties allowing oxygen diffusion.
According to our recent data, the most active sulfated zirconia catalysts possess a large number of sites Zr3+, which interact with the adsorbed alkanes. Therefore, we believe the skeleton isomerization of alkanes to proceed via the radical but not acid-base mechanism. Oxygen thermal desorption data show that sites Zr3+ are indeed active in the skeleton isomerization reactions. These sites have a short life, but they are continuously generated at oxygen desorption.
The project aims at the synthesis of supported sulfated zirconia catalysts to be active in the skeleton isomerization of alkanes. Active sites on these catalysts will be investigated with various methods, and the role of radical mechanism in isomerization processes will be determined. With this regard we suggest the following programme:
Aluminium and titanium phosphates to be used as supports for sulfated zirconia clusters. Phosphates readily interact with zirconia, and their acid properties may be easily regulated (tailored), thus allowing regulating the acidity of supported sulfated zirconia. We are able to support 10 nm sulfated zirconia particles, and the thickness of surface coverage by zirconium ions may be varied from one to 20 layers.
Standard procedures will be used to test the synthesised catalysts activity in the skeleton isomerization of alkanes.
Acid properties of supports will be modified to determine their effect on catalysts performance.
EXAFS, WAXS (SR fir wavelength ~ 0.03 nm), Raman spectroscopy, NMR of P and S isotopes and HREM with EDX and EELS accessories will be used to investigate the structure, symmetry and conducting properties of active component.
Acidic properties of surface sites with coordination one or two will be studied with NMR and in situ FTIR using various probe molecules.
Selenated zirconia catalysts will also be synthesised for comparison to study surface species with in situ FTIR and Raman spectroscopies.
in situ ESR will be applied to investigate surface intermediates involved in Zr3+ reaction with alkanes.
Electrochemical methods will be used to reveal correlation between the lattice oxygen mobility and catalyst activity.
As a result of project implementation we shall elucidate
the role of radicals in the skeleton isomerization of alkanes;
the role of conducting properties of sulfated zirconia in this reaction;
the structure of active sites on the catalyst surface;
the actual mechanism of skeleton isomerization of alkanes on supported sulfated zirconia catalysts.

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

Data not available

Koordinator

University of Liverpool
EU-Beitrag
Keine Daten
Adresse
Oxford Street
L69 7ZD Liverpool
Vereinigtes Königreich

Auf der Karte ansehen

Gesamtkosten
Keine Daten

Beteiligte (4)