Invited Lecture
Microimaging of diffusion in nanoporous solids: novel input for Chemical Engineering, Material Science and Fundamental Research

Though diffusion is well-known to be among the rate limiting phenomena in numerous technical processes based on the application of nanoporous materials, our knowledge about molecular mass transfer in such systems is still far from complete. The advent of the techniques of “microimaging” [1] could thus, over the last few years, give rise to a remarkable gain in our knowledge in this field. After an introduction into the various types of experiments by which molecular diffusion may be recorded, special emphasis shall be given on the novel evidence on mass transfer attainable with the application of interference and IR microscopy for “microimaging”. These options include the quantitation of transport resistances on the external surfaces of the particles, which in numerous cases are found to notably exceed the diffusional resistance of the genuine pore network [2], transport assessment in pore space hierarchies [3], the simultaneous observation of the fluxes of different components including “uphill” diffusion and “overshooting” [4], the recording of transient concentration profiles during catalytic reactions with the option of the one-shot determination of the effectiveness factor [5] and the decision on the applicability of Fick’s laws in complex systems [6]

[1] J. Kärger et al., Nat. Mater. 13 (2014) 333–343.

[2] J.C.S. Remi et al., Nat Mater 15 (2015) 401–406.

[3] D. Schneider et al., Chemie Ingenieur Technik 87 (2015) 1794–1809.

[4] A. Lauerer et al., Nat. Comms. 6 (2015) 7697.

[5] T. Titze et al., Angew. Chem. Int. Ed. 54 (2015) 5060–5064.

[6] T. Titze et al., Angew. Chem. Int. Ed. 54 (2015) 14580–14583.