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Framework redox sites in nanoporous molecular sieve catalyst

Nguyen, K.D.H.; (2008) Framework redox sites in nanoporous molecular sieve catalyst. Doctoral thesis, UCL (University College London).

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Abstract

The work described in this thesis is concerned with the characterisation of metal ions substituted nanoporous materials. The first chapter deals with the introduction to nanoporous materials, with historical background, structural chemistry, synthetic methods and catalytic applications. The second chapter describe the experimental techniques used in this work. Chapter 3 deals with the study of cobalt ions substituted nanoporous aluminophosphate material. Here the main aim is to understand the effect of synthesis condition used in preparing CoA1PO-34, CoSAPO-34 materials on the particle size, micro-structure stability and more importantly the oxidation-reduction chemistry of cobalt ions. It was found using microscopy and in situ XRD/EXAFS technique, that when CoA1PO-5.PO or CoSAPO-34 materials are prepared around pH 7.5, the system has small particles, with good structural stability and complete redox chemistry of cobalt ions. Chapter 4 describes the results obtained from the in situ studies of iron substituted A1PO-5. Here the aim to investigate the influence of structure directing organic template on the state of iron in the as-synthesised and calcined form. It was found that, depending on the nature of template, the coordination of Fe(III) ions change from octahedral to tetrahedral at different temperature. In situ studies of reactivity of Ti(IV) species in titanosilicate TS-1 material was studied using X-ray absorption near edge structure and they are described in chapter 5. A comparison between amorphous titanosilicate and crystalline TS-1 was made and it was found that titanium ions in amorphous material reacts much more readily with water molecules compared to crystalline counter part and this correlates with the hydrophobic character of crystalline TS-1 material. In the final chapter, 6, a brief summary and conclusions obtained from the work described in the results chapter are given.

Type:Thesis (Doctoral)
Title:Framework redox sites in nanoporous molecular sieve catalyst
Language:English
Additional information:Authorisation for digitisation not received
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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