In situ and Operando Catalytic Raman Studies

tools for real-time Monitoring of Energy and Sustainable Related Processes

Catalysis Science stands on knowledge as a key ingredient to support further progress. Determining which structure, which functional group, is efficient for a given reaction step is a key ingredient to be able to design and develop new catalyst; it is also critical to understand how a catalyst operates and, ultimately, how to control its performance.

   Reactants and products shape the catalyst structure during catalytic operations, which accounts for activation and deactivation phenomena. This is the driving force to combine in situ studies with genuine catalytic operation (i.e., the Operando methodology). The key feature of operando studies lies on the spectroscopic cell design: it is critical that an operando reactor cell satisfies the requirements of both an in situ cell (spectroscopy) and those of a catalytic reactor (catalysis) (1); this is not the case for most in situ cells. Major progress has been made since operando methodology was proposed in 2002 (2), as it has been summarized in recent reviews and reports (3-5); the key message is that catalysis is a science that cannot be understood without spectroscopy. Currently, progress is made to implement reactor-engineering considerations into operando spectroscopy (6,7).

   We will present applications of Raman spectroscopy relevant to energy and sustainable process. First, we will present the study of structural transformations in ammonia-borane related materials (operando Raman reactor) and its simultaneous release of hydrogen (on line quadrupole mass spectrometry or online Raman gas cell). Next, we will present the use of real-time Raman spectroscopy to monitor the reaction progress during the valorization of renewables, in particular, conversion of glycerol into glycerol carbonate by reaction with urea. These examples will illustrate the value of spectroscopy in general, and of operando spectroscopy in particular, as the enabling tool for the knowledge-based design of catalysts.