Abstract
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 31 P NMR spectra of trimethylphosphine (TMP). Brönsted acid strength is not high when compared with that of zeolite.
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