Study of the diffusion properties of zeolite mixtures by combined gravimetric analysis, IR spectroscopy and inversion methods (IRIS)

We report the development of a new method of investigation of the mass transport properties of acidic zeolite-based materials aiming to overcome the limitations of classical approaches. It consists in hyphenating gravimetric analysis and infrared spectroscopy. The former allows assessing the diffusion from the gas phase to all the porosity, while IR allows for selective assessment of diffusion to the zeolite active sites located in the micropores. Furthermore, the data are processed by an original methodology allowing the recovery of the distribution of diffusion domains by inversion of the integral equations describing the uptake curves or the evolution of the infrared spectra. The combination of gravimetric analysis and IR spectroscopy makes it possible to monitor and distinguish diffusion within the various components of the material. The methodology has been applied to the isooctane uptake in the mechanical mixture of FAU and MFI zeolites. Analysis of both gravimetric uptake curves and evolving infrared spectra allows distinguishing and assigning diffusion domains to the H-FAU and H-MFI components of the mixture, with high and low effective diffusion rate constants, respectively. The advantages and limits of the methodology are discussed. A method combining gravimetric analysis and infrared spectroscopy to study the mass transport properties of zeolite-based materials overcomes some of the limitations of conventional approaches.

Automated summary

This study presents a new method for investigating the mass transport properties of acidic zeolite-based materials. By combining gravimetric analysis and infrared spectroscopy, diffusion within the various components of the material can be monitored and distinguished. The method was applied to a mechanical mixture of FAU and MFI zeolites, allowing for the identification of diffusion domains with high and low effective diffusion rate constants.