Dry reforming of methane using non-thermal plasma-catalysis

This thesis has studied CO2 reforming of CH4 in atmospheric pressure, non-thermal plasma discharges. The objective of this research was to improve the current understanding of plasma-catalytic interactions for methane reforming. Chapter 1 introduces the existing and potential applications for methane reforming products. The industrial approaches to methane reforming and considerations for catalyst selection are discussed. Chapter 2 introduces non-thermal plasma technology and plasma-catalysis. An introduction to the analytical techniques used throughout this thesis is given. Chapter 3 investigates the effects of packing materials into the discharge gap. The materials were found to influence the reactant conversions for dry reforming of methane in the following order: quartz wool > no packing > Al2O3 > zeolite 3A > BaTiO3 > TiO2. In addition to the dielectric properties, the morphology and porosity of the materials was found to influence the reaction chemistry. The materials also affected the electrical properties of the plasma resulting in surface discharges, as opposed to a filamentary discharge mode. Chapter 4 investigates the effects of variation in CH4/CO2 ratios on plasma-assisted dry reforming of CH4. Differences in the reaction performance for different feed gas compositions are explained in terms of the possible reaction pathways and the electron energy distribution functions. A NiO/Al2O3 catalyst is introduced for plasma-catalytic dry reforming of CH4, which was found to have no significant effect on the reaction performance at low specific input energies. Chapter 5 presents the plasma-assisted reduction of a NiO/Al2O3 catalyst by CH4 and H2/Ar discharges. When reduced in a CH4 discharge, the active Ni/Al2O3 catalyst was effective for plasma-catalytic methane decomposition to produce H2 and solid carbon filaments. A decrease in the breakdown voltage was observed, following the catalyst reduction to the more conductive Ni phase. Chapter 6 investigates the performance of the plasma-reduced Ni/Al2O3 catalysts for plasma-catalytic dry reforming of methane. Whilst the activity towards dry reforming of CH4 was low, the CH4 plasma-reduced catalyst was found to be effective for catalysing the decomposition of CH4 into H2 and solid carbon filaments; both potentially useful products. Chapter 7 discusses further work relevant to this thesis.EThOS - Electronic Theses Online ServiceGBUnited Kingdo