Insight into the direct conversion of syngas toward aromatics over the Cu promoter Fe-zeolite tandem catalyst

Direct conversion of syngas into aromatics (STA) on the tandem catalyst containing Fischer-Tropsch (F-T) synthesis catalysts and acid zeolites, especially Fe-based catalysts and ZSM-5, has been attracting significant attention due to the higher cost efficiency. Even though promoters have frequently been added into the Fe-based part to improve the performance of STA reaction, its motivating mechanism is still unclear in the tandem catalyst system. Herein, the influence of the Cu promoter was evaluated for the catalytic activity of Fe-based/zeolite tandem catalysts in the STA process. Moreover, the working mechanism of the Cu promoter had been systematically investigated by adding different copper amounts and deliberately designed experiments. It was demonstrated that the addition of copper could improve aromatic selectivity because the Cu promoter could facilitate CO to participate in the conversion of olefins into aromatics over the tandem catalyst. In addition, the Cu promoter doped into the Fe-based catalyst drastically suppressed methane formation and enhanced the stability of the catalyst in the STA reaction. These findings provide insights into the effect of the Cu promoter on producing aromatics from syngas over the Fe-based/zeolite tandem catalyst system.