In situ and operando characterization of zeolite-based catalysts by means of Raman spectroscopy

The main goal of this doctoral project has been the application of Raman spectroscopy to the characterization of zeolites, with particular regard to their behavior in controlled atmosphere and/or under reaction conditions. Even if apparently this may be considered a trivial task (as for many other spectroscopic techniques), the Raman approach to zeolites is rather complex because of the several drawbacks affecting it (e.g. fluorescence and laser induced sample damaging). A key point of this thesis has been to exploit/develop a set of tools able to overcome such limitations: several implementations have been reported in the literature with the same aim, however each one demonstrated some incompatibilities with the purposes of the present work. For such reason, a totally new experimental setup was designed, developed and tested. Following the good preliminary results achieved, the novel device was then applied to the study of two relevant processes in the zeolite/catalysis field: the Methanol To Hydrocarbon (MTH, based on acid zeolites) and the Hydrogen Peroxide to Propylene Oxide (HPPO, catalyzed by Titanium Silicalite- 1, TS-1). The former represented an optimal benchmark for the new setup, since the reaction involves labile organic reactants and products, thus threatened by the photon induced damaging. The latter, instead, thanks to the peculiar features of the TS-1, can be regarded as a more fundamental research work, also involving a multiple technique approach and quantum mechanical simulation (the latter representing a significant fraction of this thesis work).