Preparation of Cu-Na-ZSM-5 catalysts by thermal spreading techniques

Publisher Summary In the preparation of redox catalysts from zeolites, transition-metal ions are often introduced by aqueous exchange or by solid-state ion exchange into H or ammonia forms. Recent publications about non-stoichiometric thermal spreading of transition metal compounds suggest that intra-zeolite but extra-lattice species may be created by these techniques. Microwave treatment has been claimed to accelerate this route of introduction of transition-metal compounds into Na-zeolites, e.g., of CuCl 2 into Na-ZSM-5. In a detailed study of the interaction between CuCl and Na-Y at elevated temperatures, Jiang and Karge came to the conclusion that CuCl exchanges on a stoichiometric basis with the concomitant formation of NaCl. Thermal spreading techniques may provide Cu-ZSM-5 samples suitable to probe the relevance of certain catalyst functions for the selective catalytic reduction of NO by hydrocarbons (SCR-HC) over Cu-ZSM-5. In particular, the role of zeolite acidity in the reaction mechanism of SCR-HC has been a matter of debate. This chapter presents a study of the spreading process by surface spectroscopy—XPS; XAES (X-ray induced Auger Spectroscopy)— and XRD. The IR spectroscopic data on the acidity of the materials obtained and the results of catalytic tests are briefly summarized in the chapter.