Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Chemical and Biochemical Engineering


Dr. Hugo de Lasa


Fluid Catalytic Cracking (FCC) unit is one of the most important conversion processes used in petroleum refineries. Nowadays, petroleum refineries, and specifically FCC units, have to be improved. New technologies must be developed to increase the refineries revenues as well to comply with environmental regulations. One area of significant concern is the necessary in-situ FCC gasoline sulfur reduction.

In this respect, this PhD dissertation proposes a new Zn-Offretite (Zn-OFF) additive for gasoline sulfur reduction via selective adsorption in FCC units. The PhD research developed covers the preparation of the Zn-OFF zeolites and their physicochemical characterization. This physicochemical characterization leads to the demonstration that zinc species are most likely included in the OFF framework. Furthermore, it is also shown that the Zn in the OFF zeolites, may considerably increase acidity as well as the abundance of Lewis acid sites. As a result, it is found that the Zn in the OFF is tailored for thiophenic species selective adsorption.

Regarding the Zn-OFF performance, it is proven in this PhD dissertation, that the Zn-OFF additive displays an excellent performance for 2-methylthiophene (2MTh) selective adsorption. The best sulfur removal was found using the Zn(3.5wt%)-OFF additive and 2MTh at 530 °C and 5 s.

On the basis of the results obtained, it is anticipated that the Zn(3.5wt%)-OFF additive can provide a valuable in-situ sulfur selective adsorption for the thiophenic compounds. It is also established that the used Zn(3.5wt%)-OFF additive, when blended with a FCC commercial catalyst reduces both coke production and sulfur in coke.

It is thus, demonstrated that under typical FCC unit operating conditions, the Zn(3.5wt%)-OFF additive can selectively adsorb sulfur contained species. This additive can also decrease sulfur in coke with this leading to a mitigation of SOx emissions in the FCC regenerator, where coke is combusted and catalyst reactivated.