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Project

Fluorescence microscopy tools for in situ catalyst characterization

The goal of this PhD thesis is to apply fluorescence microscopy to investigate the interplay between local catalytic performance and catalyst porosity and to derive structure-activity and selectivity relationships for heterogeneous catalysts at the level of individual catalytic turnovers. To achieve this goal, I employed both diffraction-limited and super-resolution fluorescence microscopy with support from other techniques.

A first objective was to study the effects of dealumination on the distribution of acid sites inside individual mordenite crystals and the impact hereof on the catalytic activity. Using super-resolution fluorescence microscopy, Raman microspectroscopy, and focused-ion-beam-assisted scanning electron microscopy I identified significant variations in catalytic properties inside individual dealuminated mordenites as well as strong variations between individual catalyst crystals. The origin of this suboptimal catalytic performance could be linked to variabilities that exist during commercial, large-scale dealumination.

Secondly I studied the effect of solvents on the catalytic performance of acid H-ZSM-5. Using fluorescence microscopy with the acid-catalyzed furfuryl alcohol oligomerization reaction I discovered that the reaction preferentially occurs in a subset of the ZSM-5 pores. Using solvents of different polarity this pore selectivity could be altered. This result can be used to selectively perform catalytic reactions in either of the micropore subsystems.

Later, this fluorescence based approach was extended to study the catalytic activity of metal-organic frameworks. For ZIF-8 I could prove that the reactivity is limited to the outer surface and bulk crystal defects. This inefficient use of the MOF material can be abated by the introduction of larger mesopores. In this project, I used oleic acid etching to increase the molecular penetration of the whole crystal volume.

In conclusion, in this thesis I have applied fluorescence microscopy to resolve the structure-activity relationships in zeolites and metal-organic frameworks, and suggested strategies to optimize the catalytic activity. The results and the wealth of inferences therefrom demonstrate how fluorescence microscopy can enrich catalysis research as a characterization method. Such studies can be used to advance the field of catalyst design and development.

Date:4 Dec 2012 →  28 Jun 2017
Keywords:Heterogenous Catalysis, Fluorescence Microscopy
Disciplines:Analytical chemistry, Macromolecular and materials chemistry
Project type:PhD project