Finely adjusting material properties
We revealed the alumination mechanism of siliceous SBA-15, SBA-16, and zeolite Y alumination using sodium aluminate. Synthesis conditions are improved for a maximum aluminum introduction. Na-form materials proof excellent ion exchangers, whereas acid forms loose a lot of the framework aluminum and generate comparably few acid sites. A deep characterization of acid sites using molecular probes is included.
A library of copper mordenites was synthesized by variation of Cu/Al stoichiometry, ion exchange methodology and framework counter ions. It could be shown that copper in H-form Mordenties almost quantitatively participates in the stoichiometric methane oxidation. This was accompanied by the formation of extra-framework aluminum species. Thus, the presence of counter ions adds substantial stability to MOR framework aluminum.
New SUZ-4 zeolite catalysts were dealuminated, desilicated, and synthesized with incorporated boron. Acid sites were quantitatively located within 8- and 10-MR channels of the SZR topology. Furthermore, samples were applied in the methanol conversion reaction and, after exchange with copper, in the selective oxidation of methane.
ZSM-22 zeolites were desilicated to improve their lifetime in the methanol-to-olefin conversion reaction. The desilication was accompanied by a surprisingly strong loss in acid site density and resulted in a likewise high propene yield.