Structural and catalytic studies of novel Au/Ni enantioselective catalysts

Enantioselective catalysis;Gold alloys;Nickel catalysts;Catalysts

Trant, Aoife Geraldine ; Baddeley, Christopher J. ; Baddeley, Christopher J.

University:University of St Andrews

Department:Chemistry (School of)

关键词: Enantioselective catalysis;    Gold alloys;    Nickel catalysts;    Catalysts;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/854/AoifeTrantPhDThesis.pdf?sequence=3&isAllowed=y

来源: DR-NTU

【 摘 要 】

Heterogeneous enantioselective catalysis strives to create new successful catalysts. One of themost researched examples is the hydrogenation β-ketoesters using nickel-based catalysts. Ahindrance in the industrial scale-up of this enantioselective hydrogenation reaction is the lackof exact details of how chirality is bestowed onto this achiral metal surface. While a numberof mechanisms have been proposed to explain the enantioselective behaviour of this system,these are predominantly based on catalytic studies. An alternative approach is through surfacescience studies examining the morphology, structure and composition of this catalyticsystem. A range of ultrahigh vacuum based model studies investigating the structure andcomposition of ultrathin Ni films and Ni/Au surface alloys on Au{111} using the techniquesof Scanning Tunnelling Microscopy (STM) and Medium Energy Ion Scattering (MEIS) arepresented in this thesis. In addition, the adsorption of the chiral modifier (S)-glutamic acidhas been studied on these surfaces using vibrational spectroscopy (Reflection AbsorptionInfrared Spectroscopy (RAIRS)) and Temperature Programmed Desorption (TPD).Furthermore, MEIS has been used to investigate the influence of (S)-glutamic acid on thesurface composition of Au/Ni model catalysts detecting effects such as adsorbate inducedsegregation and de-alloying behaviour.In addition, colloidal preparative routes have been used to synthesise bimetallic Au/Ninanoparticles supported on mesoporous silica. The catalysts are then modified by theadsorption of the chiral ligand, (R,R)-tartaric acid. Finally, the catalysts are tested for theiractivity and enantioselectivity with respect to methylacetoacetate hydrogenation. At eachstage the catalysts are characterised by a combination of Extended X-ray Absorption FineStructure (EXAFS); Transmission Electron Microscopy (TEM), Energy Dispersive X-raySpectrometry (EDS) and Atomic Absorption Spectroscopy (AAS).