Experimental and Theoretical Investigations on True Thermal Conductivity of FAU-Type Zeolite in Porous Composites by Laser Flash Method
An approach of determining true thermal conductivity of FAU-type zeolite is introduced, due to the lack of knowledge of its solid phase conductivity as database for evaluating multi-phase heat transfer of porous composites as catalyst supports. Pellet-shaped samples made of zeolite with different fraction of pseudoboehmite (binder) were prepared. Samples with different total porosity (?) were achieved by tuning the proportion of peptizing agent added during slurry preparation, as well as using different pelletizing pressure. Pellet’s apparent thermal conductivity (?app) was determined by equation ?(T)=?(T)??(T)?c_p (T) at 20-200°C under atmospheric pressure, where thermal diffusivity was measured by Laser Flash method, bulk density was calculated from its geometry and heat capacity was determined by DSC. Results showed that binder has a positive effect on thermal properties, and apparent thermal conductivity decreased with increasing porosity in a linear function, while increased with increasing temperature. Therefore, solid thermal conductivity (?s) of each composition was found by extrapolating the measured thermal conductivity vs. porosity relationship to zero volume pore fraction. Followed by extrapolating solid thermal conductivity of all compositions to zero binder fraction, true thermal conductivity (?true) of zeolite-FAU was found to be 0.10 W/(m?K). Furthermore, based on the empirical equation of porous materials, ?_app=?_s (1-b??)+?_g?b??, porosity fitting coefficient (b) of 1.56 was found for this composite system. This method enables to determine any solid’s true thermal conductivity from its apparent conductivity measurements. It is also of great interests to compare different composite’s porosity fitting coefficient based on microstructure in the future work.
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Lisha Wang (POC,Primary Presenter), Joint Institute of Advanced Materials and Processes (ZMP), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), email@example.com;