Insight into the element migration induced tandem cooperation between CuNa-doped Fe based catalyst and Mn-treated HZSM-5 for direct CO2 hydrogenation to aromatics

Abstract

Direct hydrogenation of carbon dioxide (CO2) to aromatics is a promising strategy for relieving the stress of fossil fuels. Here, a copper and sodium co-modified Fe-based catalyst (NFC-DM) was synthesized through the pyrolysis of Cu-doped MIL-101(Fe) and Na impregnation. After combining with Mn(NO3)2 solution treated HZSM-5, 46.2% CO2 conversion and 56.1% aromatics selectivity was achieved. The tandem interaction between metal oxide and HZSM-5 triggered by element migration was clarified. The Mn(NO3)2 treatment incrassated the extra-framework Al (AlEF) layer of HZSM-5, producing more surface Lewis acid sites (LAS) and decreased total Brönsted acid site (BAS) amount. Moreover, the AlEF acted as acceptor of Cu migration from NFC-DM, leading to enhanced surface LAS amount and intensity, catalyzing additional reverse water gas shift (RWGS) on zeolite surface. Formed CO could diffuse to metal oxide surface and participate in FTS, thermodynamically boosting CO2 conversion. Finally, the mechanism of CO2 activation over zeolite surface was studied and the whole reaction pattern was proposed.