Towards renewable fuels: The effect of upscaling on catalysts used for bio-oil upgrading

Abstract

This thesis aims to elucidate the effect of upscaling on K-grafted USY catalysts used in the gas-phase aldol condensation of propanal, which is chosen as model reaction for the upgrading of bio-oil. Technical extrudate catalysts are obtained via extrusion of USY zeolite with a clay binder, either attapulgite or bentonite, followed by a K-grafting procedure. The effect of this upscaling procedure on the physicochemical properties of the catalysts was studied with several characterization methods, including ICP-OES, XRD, Ar physisorption, CO2- and Py-IR studies and CFM-based techniques. K-grafted USY/Attapulgite and USY/Bentonite extrudates were successfully synthesized given that the physicochemical properties of the parent USY material are largely preserved after upscaling. In both cases, the inclusion of clay results in the incorporation of active sites originating from the binder material. Upon K-grafting, additional active sites are created in attapulgite-bound extrudates, whereas active sites are removed from the bentonite-bound catalyst. Catalytic performance was studied with operando FT-IR/DRS-UV-Vis and in-situ FT-IR/DRS-UV-Vis measurements combined with on-line MS and off-line GC, respectively. It was found that the inclusion of binder results in an increased activity accompanied by a reduced selectivity and stability. Upon K-grafting, the overall performance of the technical catalysts improves. The trends in performance correlated with the changes in active sites observed during both steps of the upscaling procedure. Hence, it is concluded that the upscaling procedure has a significant effect on the technical catalyst properties and performance.