Applications of in situ spectroscopy in zeolite catalysis

Further progress in the field of zeolite science and heterogeneous catalysis depends on our knowledge of the coordination and chemical nature of surface sites and the mechanisms of chemical reactions catalyzed by these sites. Analytical tools for the investigation of heterogeneous reaction systems should allow the study of calcined and working catalysts under in situ conditions. In the laboratory scale, FTIR, UV-Vis, ESR, and NMR spectroscopy are suitable methods for in situ investigations of zeolites and reactions catalyzed by these materials. During the past decade, an increasing number of research groups were dealing with the development and application of new techniques allowing in situ studies under batch and continuous-flow conditions. In this contribution, a review on the most important experimental approaches of in situ FTIR, UV-Vis, ESR, and NMR spectroscopy in zeolite science is given. In addition, some characteristic applications of these methods such as for the investigation of the coordination change of iron during the calcination of microporous aluminophosphates, the mechanism of the methanol-to-olefin conversion process, and the coke formation during the synthesis of cumene and the conversion of olefins on acidic zeolites are described.