Validation of Zn–Cu/ZSM-5 catalyst performance, at pilot scale, in the catalytic conversion of butane ($n$C$_{4}+i$-C$_{4}$) technical fraction

Abstract

In petroleum refining processes, the conversion of alkanes and alkenes C2–C4 to aromatics and isoparaffins would be promising, as the concentration of olefins in fuel could be reduced and the octane rating of gasoline could be improved. The main objective of this work is to validate the performance at pilot scale of a bifunctional catalyst, Zn–Cu/ZSM-5, prepared in our laboratory and tested in the conversion of butane technical fraction. The catalyst has been obtained by ion-exchange reaction of HZSM-5 zeolite with zinc and copper nitrate aqueous solutions. As the butane fraction ($n$-C$_{4}+i$-C$_{4}$) (with variable composition) is considered a by-product in petroleum refineries, the catalytic performance of the prepared bifunctional catalyst in its conversion was investigated. Thus, in the present work, a pilot-scale Twin Reactor System Naky has been considered in order to perform the catalytic reaction tests, where the performance of the prepared Zn–Cu/ZSM-5 bifunctional catalyst has been evaluated. Concerning this, ten catalytic tests have run consecutively, regenerating the catalyst after each cycle. In was noticed that the yield of aromatic hydrocarbons (benzene, toluene and xylenes—BTX) significantly increased due to $\mathrm{Zn}^{2+}/\mathrm{Cu}^{2+}$ cations spreading through ZSM-5 zeolite framework. Accordingly, the prepared Zn–Cu/ZSM-5 catalyst showed a higher aromatization activity and selectivity for product distributions under considered experimental conditions at pilot-scale reactor. Therefore, the concentration of aromatic hydrocarbons in liquid fraction was found to exceed 80 wt% (middle value per test) even at the end of ten catalytic cycles.

Keywords

• Aromatization
• Zn–Cu/ZSM-5 catalyst performance
• Pilot-scale reactor
• C₄ technical fraction
• Dehydrogenation reaction of alkanes
• BTX formation