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In-situ synchrotron based investigations of the structure of iron substituted microporous catalysts under operating conditions

Gregori, GP; (2017) In-situ synchrotron based investigations of the structure of iron substituted microporous catalysts under operating conditions. Doctoral thesis , UCL (University College London).

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Abstract

Microporous aluminosilicates and aluminophosphates have been studied for a variety of applications. Incorporation of a transition metal ion into their framework structure allows them to be modified into functional redox catalysts for a wide range of industrially important processes. In particular, FeZSM-5 has shown remarkable catalytic activity under mild conditions for the oxidation of benzene to phenol (OBP) using N2O as oxidant. Recent work has shown that the aluminophosphate FeAlPO-5 is also equally active as a catalyst for this reaction. Therefore, the aim of this work is to investigate the changes occurring during the calcination (activation) and catalytic reaction conditions of various Fe-substituted nanoporous catalysts using synchrotron based X-ray diffraction and spectroscopic methods. High-resolution powder diffraction (HRPD) measurements were carried out on FeAlPO-5 and FeZSM-5 to investigate changes to the crystal structure occurring during calcination. Pawley refinement, indicates strong negative thermal expansion upon loss of template for FeAlPO-5. The local structure and oxidation state changes of Fe located in FeAlPO-5 and FeSAPO-34 were studied using XAS during calcination in air. In addition to the above, ruthenium containing system is also investigated to examine the possible synergistic effects between Ru and Fe by supporting over Fe containing nanoporous materials. FeMFI, FeSAPO-5, RuFeMFI and RuFeSAPO-5 were then studied using in situ Fe and Ru K-edge EXAFS during calcination in air, activation in He, and pulsed experiments with N2O/benzene. The results show reduction of Fe and Ru upon the introduction of benzene to the system, indicating that the catalytic mechanism for the (OBP) reaction may require this step for the generation of the active Fe species. In summary, the project allowed us to examine the host crystalline material and catalytically active sites using synchrotron based Xray techniques, and complementary characterisation methods.

Type: Thesis (Doctoral)
Title: In-situ synchrotron based investigations of the structure of iron substituted microporous catalysts under operating conditions
Event: UCL (University College London)
Language: English
UCL classification: UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1559778
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