Abstract
Smog has received a lot of attention and is still a major problem in big cities all over the world. A major contribution to smog are nitrogen oxides (NOx), which are mainly produced by road transport, industrial processes and power plants. A lot of research has been put into the
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reduction of these pollutants, and heterogeneous catalysts have made a major contribution to this field. Selective catalytic reduction (SCR) is an efficient technology to reduce these NOx, and is already used in diesel cars, trucks and stationary power plants. Especially Cu-based small pore zeolites as the active catalysts, like Cu-SSZ-13, have received a lot of attention and are now implemented commercially. This is not the only reason people are investigating these Cu-based zeolite materials. It turns out these materials are also very selective in the production of methanol, directly out of methane. This reaction has been considered one of the holy grails of catalysis, since it is very hard to upgrade methane, which is the major component in natural gas, directly to useful chemicals. The aim of this PhD thesis was to contribute towards the understanding of small pore Cu zeolites, in particularly Cu-SSZ-13, used in both the SCR of NOx using NH3 (NH3- SCR), as well as the activation of methane-to-methanol, on a fundamental level. In order to do this, zeolite SSZ-13 was synthesized, modified to change its properties, and exchanged to its active Cu form using different (deactivation) procedures. The catalyst materials made were characterized using conventional laboratory-based techniques, such as X-ray diffraction (XRD), ammonia temperature programmed desorption (NH3-TPD), scanning electron microscopy in combination with energy dispersive X-ray analysis (SEM-EDX), Fourier transform infrared (FT-IR) spectroscopy and ultraviolet visible near-infrared diffuse reflectance spectroscopy (UV-vis-NIR DRS). They were further tested for their catalytic activity for both the NH3-SCR and the methane-to-methanol activation, whilst following the products and unreacted feed using on-line gas-phase IR, mass spectrometry (MS), or gas chromatography (GC). During these reactions, the catalysts were studied using UV-vis-NIR DRS, so called operando spectroscopy, to yield valuable information of what is exactly going on with the catalyst during real reaction conditions. In addition, thorough characterization was performed on a small selection of catalysts using atom probe tomography (APT), a technique which can tell you the exact coordinates were each atom was located inside these zeolites.
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