Adsorption of sulfur compounds in the gasoline boiling range over FCC catalysts under process conditions

Abstract

Experiments on commercial FCC equilibrium catalysts with different hydrogen transfer properties and content of Ni and V contaminant metals were performed in a CREC Riser Simulator reactor to study the behavior of thiophenic compounds in the gasoline boiling range. Thiophene and alkylthiophenes were used as test reactants dissolved in aromatic and paraffinic solvents in usual concentrations of the process, from about 150 to 400 ppm of each compound. The experiments were performed under conditions similar to those of the industrial operation (510 º C, contact time 5 to 20 s). The reaction effluents were analyzed by on-line gas chromatography using two detectors simultaneously: FID (hydrocarbons) and PFPD (sulfur). The results showed that a higher hydrogen transfer capacity in a catalyst favors the decrease of the concentration of sulfur compounds in gasoline by adsorption and / or coke formation. These results were more pronounced as the molecular weight of the alkylthiophene increased. Reductions in total sulfur concentration in the gas phase as high as 65 % were observed. Among contaminant metals, Ni seemed to have an important contribution to this effect.