Oxydative Deammonisierung von NH4-Zeolithen

Abstract

A comparative thermogravimetric study of the deammoniation of NH~-mordenite, NH4-chabazite , and NH~-stilbite in oxidizing and inert atmosphere has been carried out. The results suggest that in oxygen atmosphere an intracrystalline oxidation of thermally-excited ammonium lattice cations occurs. This reaction proceeds at much lower temperatures than the thermal deammoniation in an inert atmosphere and consequently results in a much better separation of the dehydroxylation process from the deammoniation. Because of the hydrothermal conditions resulting from the formation of water during the oxidizing deammoniation, certain structural changes of the hydrogen form of chabazite and stilbite occur as revealed by changes of the dehydroxylation behaviour.In der Wasserstoff-Form vorliegende, saure Zentren des Br6nsted-Typs enthaltende Zeolithe finden als Kata|ysatoren eine weitverbreitete Anwendung und werden im allgemeinen dutch thermische Zersetzung der NHrZeolithe erhalten:In vielen Fiillen wird angestrebt, die sog. Deammonisierung bei m6glichst niedriger Temperatur auszufiihren, um die Dehydroxylierung der H-Form zu vermeiden