NMR study of tungstated zirconia catalyst: characterizing the surface of tungstated zirconia and the influence of reduction treatment Original Research Article

In this NMR study, reduction treatment formed and increased Brönsted acid sites on tungstated zirconia (WZ); in contrast, Lewis acid sites was decreased. The upfield shift of pyridine bound to Brönsted acid sites (from −173 to −181 ppm) in reduced and evacuated WZ was ascribed to the increased interaction between pyridine and the H+ of the Brönsted acid sites, indicating that reduction treatment not only increased the number of Brönsted acid sites but also enhanced their strength. However, this upfield shift was not observed in the 31P NMR spectra of trimethylphosphine (TMP). Brönsted acid strength is not high when compared with that of zeolite.