Design Of nanostructured gold and gold alloy catalysts for sustainable selective oxidation processes
File(s)
Author(s)
Khawaji, Motaz Moid M.
Type
Thesis
Abstract
The transition into greener and more sustainable chemical manufacturing processes necessitates the
development new generations of heterogeneous catalysts. The selective oxidation of organic
molecules is a class of reaction of paramount importance to the chemical industry as it enables the
production of epoxides, alcohols, aldehydes and other important oxygenates. Metal nanoparticles
(NPs) consisting of several hundreds or thousands of atoms possess unique properties which are often
drastically different from the bulk state properties. This is particularly true for Au NPs, which have
recently been shown to exhibit high catalytic activity for a range of reactions. The present thesis
investigates the design of nanostructured Au-based catalysts and their performance in selective
oxidation reactions. Using advanced synthesis and characterization techniques has enabled the
fabrication of novel and highly active Au-based catalysts. Monometallic and bimetallic Au-Pd
colloidal NPs with various atomic compositions have been synthesized and immobilized on titania
and ceria nanostructures. The new catalysts were tested in the selective oxidation of benzyl alcohol
and glucose, and were found to be substantially more active than similar catalysts reported in the
literature. The catalytic activity and product selectivity were found to be strongly dependent on the
Au-Pd particle size, composition, and the morphology and physiochemical properties of the support.
In the selective oxidation of glucose over AuxPdy/titanate nanotubes, a new linear correlation between
the concentration of Au in the alloyed Au-Pd NPs and the formation of deep oxidation products was
discovered. Amongst the various ceria nanostructured supports examined, ceria nanorods (Ce-NR)
were found to give the most active Au-Pd catalysts. The exceptional catalytic activity and stability of
Au-Pd/Ce-NR in benzyl alcohol and glucose oxidation was ascribed to the high oxygen activation
potential of Ce-NR and its ability to stabilize finely dispersed colloidal Au-Pd NPs on its exposed
facets and defect sites. Characterization of the various catalysts by TEM, STEM, STEM-EDX, XPS
and XRD provided invaluable insights into the structure-activity relationship in supported Au-Pd
catalysts, which helped in optimizing catalyst design. This thesis has also shed light on some
fundamental aspects in the selective oxidation of hydrocarbons in the liquid phase with Au catalysts.
development new generations of heterogeneous catalysts. The selective oxidation of organic
molecules is a class of reaction of paramount importance to the chemical industry as it enables the
production of epoxides, alcohols, aldehydes and other important oxygenates. Metal nanoparticles
(NPs) consisting of several hundreds or thousands of atoms possess unique properties which are often
drastically different from the bulk state properties. This is particularly true for Au NPs, which have
recently been shown to exhibit high catalytic activity for a range of reactions. The present thesis
investigates the design of nanostructured Au-based catalysts and their performance in selective
oxidation reactions. Using advanced synthesis and characterization techniques has enabled the
fabrication of novel and highly active Au-based catalysts. Monometallic and bimetallic Au-Pd
colloidal NPs with various atomic compositions have been synthesized and immobilized on titania
and ceria nanostructures. The new catalysts were tested in the selective oxidation of benzyl alcohol
and glucose, and were found to be substantially more active than similar catalysts reported in the
literature. The catalytic activity and product selectivity were found to be strongly dependent on the
Au-Pd particle size, composition, and the morphology and physiochemical properties of the support.
In the selective oxidation of glucose over AuxPdy/titanate nanotubes, a new linear correlation between
the concentration of Au in the alloyed Au-Pd NPs and the formation of deep oxidation products was
discovered. Amongst the various ceria nanostructured supports examined, ceria nanorods (Ce-NR)
were found to give the most active Au-Pd catalysts. The exceptional catalytic activity and stability of
Au-Pd/Ce-NR in benzyl alcohol and glucose oxidation was ascribed to the high oxygen activation
potential of Ce-NR and its ability to stabilize finely dispersed colloidal Au-Pd NPs on its exposed
facets and defect sites. Characterization of the various catalysts by TEM, STEM, STEM-EDX, XPS
and XRD provided invaluable insights into the structure-activity relationship in supported Au-Pd
catalysts, which helped in optimizing catalyst design. This thesis has also shed light on some
fundamental aspects in the selective oxidation of hydrocarbons in the liquid phase with Au catalysts.
Version
Open Access
Date Issued
2019-07
Date Awarded
2019-10
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Chadwick, David
Sponsor
Saudi Aramco
Engineering and Physical Sciences Research Council
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)