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Title: Catalytic and sorption measurements using flux response technology
Author: Sasegbon, Ayodeji Oladipo
ISNI:       0000 0004 5349 4788
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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Advancements in characterisation techniques in the field of heterogeneous catalysis have been explored, in particular the powerful in situ perturbation method, Flux Response Technology (FRT). The adaptation of FRT as a novel in situ perturbation technique in gas sorption measurements continues to yield consistent results with literature values. This is made possible because FRT measures miniscule changes in transient flows in the order of 10-2 μl/min for gaseous processes involving a change in volume (dV/dt). These changes are measured directly by a very sensitive differential pressure transducer (DPT) in a pneumatic system analogous to an electrical Wheatstone bridge assembly, whereby gas molecules replace electrons and capillaries function as resistors. By showing the successful incorporation of the measurements of adsorption capacities and diffusivity coefficients in the same experimental window, FRT's use as a bolt-on technology for the rapid screening of catalyst material has been highlighted. The technique possesses a distinct advantage in requiring no prior calibrations to the system, enabling the analysis of a broad spectrum of materials and gases. The FRT technique also features a unique ability in being able to act as a dual flowrate and composition detector through the use of carefully calculated delay lines to separate changes in flowrate caused by perturbations of concentration and changes in composition. The FRT technique provides a quick, simple, accurate, and inexpensive method of characterising material properties in situ in heterogeneous catalysis. Several studies into the dynamics of gas sorption processes utilising FRT measurements on adsorbents were undertaken in the completion of this PhD. The diffusivity parameters of propane in varying alumina/CeZrOx washcoats of Cordierite monoliths were investigated under isothermal conditions. A novel method of analysing FRT derived response profiles with the Zero Length Column (ZLC) model was established and reported on. The diffusion coefficients obtained were consistent with previously reported macroscopic data and compared well when evaluating the structural differences of the washcoats of each sample (Granato et al., 2010). The dynamics of ammonia sorption on commercially available zeolites with varying SiO2/Al2O3 ratios was analysed to investigate the total acidity of these zeolites. The dynamics of carbon dioxide sorption were also investigated to analyse the total basicity of the same zeolite samples. Process optimisations were conducted to obtain an ultra fast isotherm measurement technique for the analysis of nitrogen sorption on aluminium oxides with varying surface areas at 77 K. Finally, insights into the development of a dynamic parallel performance testing (DPPT) FRT setup were undertaken to directly compare the activities of catalytic material operating side by side.
Supervisor: Hellgardt, Klaus Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral