Constructing directional component distribution in a bifunctional catalyst to boost the tandem reaction of syngas conversion

Abstract

Controlling the formation, diffusion, and conversion of bridging intermediate is important for improving the performance of a tandem reaction over a multi-component catalyst. However, it remains highly challenging because the random distribution of catalytic components via conventional mechanical combination usually endows nondirectional diffusion, resulting in an obvious decrease in catalytic performance. Here, we report a recrystallization methodology dealing with the extruded Cr 2 O 3 /ZSM-5 bifunctional catalyst to distribute the oxide on zeolite in an oriented manner. It is confirmed that Cr 2 O 3 preferentially locates on the (100) and (101) surfaces of plate-like ZSM-5 and that the (010) surface is highly exposed. Hence, the diffusion of the bridging intermediate and products is modulated in a directional way, boosting the tandem reaction of CO conversion to aromatics. A 2.99 mmol g −1 h −1 formation rate of aromatic rings (on carbon base) at a 49.4% CO conversion is achieved over the recrystallized catalyst, which is the highest performance data yet reported. • Oriented component distribution in Cr 2 O 3 /ZSM-5 is achieved via recrystallization • Diffusion of the intermediate and products is modulated in a directional way • Directional spatial pathway boosts the tandem reaction of syngas to aromatics Syngas is an important platform for producing a variety of value-added chemicals. The direct conversion of syngas to olefins and aromatics over oxide-zeolite bifunctional catalysts could achieve high selectivity of desired products via a tandem-reaction coupling strategy in a short-cut process. The tandem reaction usually involves the transfer or diffusion of key intermediates among catalytic components, which is critical for catalytic performance. Therefore, modulating the diffusion behavior of the intermediates is significant but remains a great challenge. Here, using a recrystallization methodology, we constructed a Cr 2 O 3 /ZSM-5 catalyst with an oriented distribution of Cr 2 O 3 component on specific surfaces of ZSM-5. Hence, the diffusion of the intermediate and products is modulated in a directional way, highly boosting the syngas-to-aromatics conversion. This approach is thus justified as a promising and universal strategy to improve the catalytic performance in bifunctional catalysts. Diffusion and conversion of bridging intermediates is crucial to driving tandem reactions over multi-component catalysts. In this work, the oriented component distribution in Cr 2 O 3 /ZSM-5 bifunctional catalysts was successfully achieved via a recrystallization approach as characterized by nano-computed tomography. The rearrangement of component distribution and the simultaneous functionalization of inert binder via recrystallization highly promote the transfer of C 1 intermediate and product in a directional spatial pathway and improve the reaction efficiency of syngas to aromatics in bifunctional catalysts.