Inorganic Functional Materials

Dr. Sebastian Wohlrab

Selected examples for process-oriented materials development

LPG separation using zeolite membranes

A more sophisticated seeding technique for the generation of MFI membranes was developed for this process. Basically, MFI slurries are used for the activation of inert Al2O3 supports for heterogeneous crystallization. The resulting MFI seed layer acts both as a heterogeneous nucleation side and as a flexible distance holder between support and MFI membrane; this suppresses defective formations during thermal template removal. An investigation is currently in progress, using such mechanically stabilized membranes, examining the separation of natural gas under realistic process conditions.

Oxygen removal from biogas

Methane from biogas contains typically up to 5000 ppm (0.5 %) oxygen. However, significantly lower values are permitted when supplying into the gas grid. With the aim of improving the quality of biomethane, the most recent project of our group is about materials development for the reduction of oxygen in biomethane. Therefore, developments focus mainly on process-adapted reduction catalysts and also novel inorganic absorbents. In the event of success, a technology should be available for the removal of oxygen to concentrations below 10 ppm.

Membrane reactors for the production of syngas

Perovskite membranes can be used for the production of pure oxygen. Ionic conduction via the oxygen lattice of the perovskite is used for a highly-selective separation of the oxygen from the air feed. An interesting application of this property is the usage of enriched oxygen in the permeate room of such a perovskite membrane for chemical reactions. Membrane reactors were developed for the partial oxidation of methane to syngas. Furthermore, stable perovskites against carbon dioxide and derived membranes are in the focus of our research. Currently perovskite membranes for the selective oxidation of methane are under investigation.

Selective oxidation catalysts for the conversion of methane

The influence of the nature of support materials on the catalytic performance of VOx is currently being investigated. In particular, nanoporous glass, something that is almost unexplored in terms of catalysis, can be synthesized with a narrow pore size distribution and with pore sizes ranging from 1 to 1000 nm. Pore volumes between 0.1 and 1.1 cm3/g and inner surfaces of up to 500 m2/g can be provided in such materials. Broad flexibility in the geometric properties makes such materials promising candidates for application as improved support materials. It is possible to optimize suppression of overoxidation during an oxidative conversion of methane, while support is required in restrictive reaction rooms.