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Linking flow reactor and temporal analysis of product (TAP) kinetic studies

Ruiz Castillo, Leticia 2020. Linking flow reactor and temporal analysis of product (TAP) kinetic studies. PhD Thesis, Cardiff University.
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Abstract

The study of chemical kinetics of various catalytic systems has been the focus of the work presented in this thesis, which was primarily supported on continuous flow approaches complemented with TAP reactor experimental analysis. Software development constituted an essential part in this research. On the one hand, the implementation of a software system made possible the automation of continuous flow reactions. On the other hand, a second piece of software allowed the extraction of kinetic information from experimental TAP data. During the continuous flow investigation, inactivity of Au/TiO2 toward the CO oxidation reaction was observed. Near atmosphere pressure (NAP)-XPS analyses revealed the presence of both Au1+ and Au0 species on the surface of Au/CeO2 while only Au0 was detected on Au/TiO2. This suggested that the presence of both cationic and metallic gold species is important to kick start the CO oxidation reaction at low temperatures. Based on the different activities observed during temperature ramp up and ramp down stages when fresh and reused samples were tested, and also supported on the NAP-XPS analysis results, the transition from Au+1 to Au0 starting at a temperature threshold of around 40-50 °C was proposed. Regarding activation energies, values around 40-45 kJ mol-1 were calculated for both Au/CeO2 and AuPd/CeO2. Finally, orders of reaction with respect to CO at constant ratio between concentration of reactants (CO and O2) with similar values of around 1 were obtained for both Au/CeO2 and AuPd/CeO2. Flow reactor studies were complemented with TAP reactor experiments. Relevant parameters such as the number of molecules per pulse or the percentage of active surface oxygen were calculated. Finally, based on a series of qualitative assessments, a combination of both Eley-Rideal and Langmuir-Hinshelwood mechanisms was proposed to be taking place on the surface of Au/CeO2.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Date of First Compliant Deposit: 14 July 2020
Last Modified: 16 Jul 2020 08:59
URI: http://orca.cf.ac.uk/id/eprint/133417

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