| Summary: | The transformation of carbon dioxide into added value chemicals by a plasma-activated catalytic process was studied. First of all, the current status of CO2 reutilisation by plasma-assisted technologies was reviewed. Followed by an in-depth study on the process of plasma-catalysis, the effects of dilution gas (i.e. argon and nitrogen) addition and operating parameters in CO2 dissociation were systematically investigated in non-thermal atmospheric pressure plasma barium titanate (BaTiO3) packed-bed reactor from both an engineering and scientific point of view. The extensive experimental and modelling study provided an insight into the relationship between the operating parameters, plasma electrical properties and electron-induced reaction processes in the discharge and the effect of the dilution gases on the product formation and reaction mechanism. The results showed that there was a higher CO2 conversion and energy efficiency in the studied packed-bed reactor than the dielectric barrier discharge (DBD) reactor with and without packed materials using electrodes covered by dielectric layers. Based on the above research work, an in-depth study of the complex mechanism of plasma-catalysis interface reaction was carried out. A new model catalyst (Ni/α-Al2O3 nanocatalyst) with a minimum of physical and chemical variables was specifically designed and synthesised for plasma-assisted reactions to help directly understand the intrinsic role of catalytic active sites during the plasma-catalytic process. In situ time-resolved tuneable lead salt diode laser (TDL) diagnostics of carbon dioxide decomposition over the model catalysts in a planar dielectric barrier discharge (DBD), non-thermal atmospheric pressure plasma reactor demonstrated that the active Ni metal sites do enhance the plasma-catalytic reaction in a similar way as that in conventional catalytic processes. Finally, demonstration of a novel catalysis concept of in situ capture-catalytic system was made for the plasma-assisted catalytic water gas shift reaction. This was investigated in a barium titanate (BaTiO3) packed-bed, non-thermal atmospheric pressure plasma reactor operating at 298 K. The results showed that the packed-bed reactor with CuBTC metal-organic framework (MOF) addition enhanced the CO conversion up to 43%. The comprehensive characterisation of the CuBTC MOF shows that CuBTC MOF exhibited sustainably good physical and chemical stabilities during 4 h long term continuous plasma reaction. The research work in this thesis showed that the BaTiO3 ferroelectric, packed-bed, non-thermal plasma reactor is a potential and powerful environmental solution for CO2 dissociation and other similar pollution treatments with a much higher conversion and energy efficiency at a high specific input energy, more mature and cheaper reactor configuration to scale-up without the need for dielectric barriers. As catalyst introduced into the plasma-assisted process, the demonstrated similar catalytic role of catalytic active sites in plasma-catalytic processes as in conventional thermal catalytic processes opened the gate to apply the catalysts and basic catalytic theories in conventional thermal catalysis field into the non-thermal and atmospheric plasma processes. The boundary of catalysis has been further extended, especially for the non-thermal atmospheric catalytic processes. The catalysis concept for the combination of plasma-catalytic process and conventional thermal catalytic process to enhance the adsorption process of the reactant and then catalyse it simultaneously over the active sites at room temperature and atmospheric pressure could be realised, as demonstrated by using the MOFs with a large gas capture capacity to catalyse water gas shift reaction in non-thermal atmospheric plasma.
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