Porous Materials and Hierarchical Systems
Porous materials play an important role both in nature and engineering. The porosity of certain soil is fundamental for the ability to store water or oil, whereas porous construction materials are mainly used for the insulating properties. In engineering, porosity is an important factor in separation and catalysis processes. In most cases, bimodal pore systems are desired, having large transport pores combined with small reaction pores (high reaction surface), ensuring low pressure drop and high reaction rates. Depending on the pore diameter, micr-, meso- and macro pores can be distinguished.
Several ten thousand molecules are comprised in macropores (> 100 nm), resulting in bulk-like behavior of the molecules inside the porous material. In mesopores interaction with the pore wall will result in Knudsen diffusion processes. The configurationally diffusion inside micropores can be used to separate different molecules. Zeolites are an important class of microporous materials and their unique properties are investigated in membrane separation and catalysis at CRT, especially in the group of Prof. Schwieger.