A fluidizable Zn offretite for selective thiophenic species adsorption. Additive performance under FCC conditions
Abstract This study evaluates a new Zn OFF additive (3.5 wt% of Zn in an offretite zeolite) to reduce sulfur in gasoline range hydrocarbons. The additive is contacted with Thiophene (Th) 2 methyl thiophene (2MTh) and 2,5 dimethyl thiophene (25DMTh) which are used to represent sulfur species. These species are concurrently fed with 1,3,5 trimethylbenzene (TMB) into a CREC Fluidized Reactor Simulator. Selected temperatures, partial pressures, reaction times and C/Os (catalyst/oil) are representative of operating conditions in FCC industrial units. It is proven that the Zn OFF additive displays an excellent performance for 2MTh selective adsorption. The best sulfur removal using the Zn OFF additive was found using the 2MTh at 530 degC and 5 s. It is hypothesized that the selective sulfur adsorption on the Zn OFF additive involves dominant Lewis acid sites. On the basis of the results reported, it is anticipated that the Zn OFF additive can provide a valuable "in situ" sulfur selective adsorption for the thiophene compounds. It is also found that the used Zn OFF additive while blended with a FCC commercial catalyst mixture reduces coke production, in particular sulfur in coke. It is thus, demonstrated that under typical FCC unit operating conditions, the Zn OFF additive can decrease sulfur in coke with this leading to a mitigation of SOx emissions in the FCC regenerator, where coke is combusted.