The Effect of Zn on Offretite Zeolite Properties. Acidic Characterizations and NH 3 -TPD Desorption Models

This article reports the effect of adding zinc to an offretite (OFF) zeolite. It is observed that zinc addition does not significantly change the specific surface area, the pore volume, or the pore size distribution. It is noticed, however, that zinc addition influences acid properties of the OFF significantly. For instance, when employing FTIR pyridine adsorption, it is observed that in the Zn-OFF, there are 2.5 times higher Lewis acid sites than Brönsted acid sites. Furthermore, when applying NH 3 -TPD, three acid sites were identified: (a) abundant number of weak acid sites, (b) fair number of moderate acid strength sites, and (c) scarce number of strong acid sites. Furthermore, NH 3 desorption kinetic parameters were also calculated. Two numerical methodologies, linear and nonlinear regression, were implemented. It was noticed that E d augments with zinc as E d for OFF < E d for Zn(2.0 wt %)-OFF < E d for Zn(3.5 wt %)-OFF.