Liquid phase catalyst characterization is experimentally challenging, but it deserves consideration because solvent choice can affect catalyst structure and acidity. Thus, in vacuo spectroscopy of adsorbed probe molecules such as pyridine, while valuable, may provide incomplete information on available catalytic sites in liquid phase reactions. To this end, an Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR) cell was used to detect pyridine adsorbed on sodium exchanged faujasite (NaY) in liquid water. The slow accumulation of pyridinium on NaY in the presence of liquid water was observed, suggesting water promotes the protonation of pyridine on NaY, a Lewis acidic material. Transmission FTIR and ATR-FTIR experiments revealed that pyridinium concentration increased with increasing amount of water in NaY, making the liquid phase technique more apt than the established vacuum technique for observing the effect of water on the acid sites of NaY. Further, we develop a procedure that allow the quantification the density of both Bronsted and Lewis acid sites in the presence of different solvents with the ATR-FTIR technique.  <br/>

Characterization and quantification of acid sites on zeolites in the presence of solvents

254th National Meeting (2017)

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