Zeolites are widely used in catalytic and adsorptive applications in which heat transfer plays an important role. In adsorptive heat exchangers, sorption efficiency depends strongly on the thermal conductivity of the adsorbent beds, while in catalytic reactors reaction rates and selectivity are closely related to the thermal conductivity of the catalysts. Despite their technological relevance, reliable data on the heat transfer properties of zeolites and zeolite-based coatings remain limited, mainly due to experimental difficulties associated with porous materials and thin layered systems. This thesis addresses the challenges in determining the thermal conductivity of zeolitic materials using the laser flash method and develops experimental strategies for both bulk materials and thin coatings. In the first part, a combined approach of laser flash measurements and mathematical modeling was established to determine the intrinsic thermal conductivity of zeolites from measurements on porous zeolite-containing composites. Systematic experiments were performed to quantify the influence of binder content and porosity on the effective thermal conductivity. By fitting the experimental results to theoretical models for porous materials and extrapolating to zero porosity and pure zeolite composition, the intrinsic solid-phase thermal conductivity was obtained. The method was applied to three framework types (FAU, MFI and CHA), allowing a comparative evaluation based on their crystalline microstructure. The second part focuses on thin zeolite coatings below 200 µm in layered structures. An adapted layered laser flash approach was developed to characterize coating properties. The influence of graphite layers used in sample preparation was quantified and eliminated by extrapolation, and the effects of coating morphology and surface roughness were systematically examined. Spray-applied (ex-situ) and chemically synthesized (in-situ) coatings were compared, showing that reactive in-situ coatings exhibit higher thermal conductivity, which is attributed to reduced grain boundary resistance and improved interfacial thermal contact.
Lisha Wang (Thu,) studied this question.