Design of hollow spherical Co@hsZSM5@metal dual-layer nanocatalysts for tandem CO2 hydrogenation to increase C2+ hydrocarbon selectivity

Abstract

A thin hollow shell nanostructure can increase effectiveness of zeolites while allowing metal nanoparticles to be supported on both its inner and outer surfaces. Herein, nanoscale hollow spherical ZSM-5 (hsZSM5) shells were synthesized from sub-micron silica spheres through a dissolution–recrystallization mechanism with assistance of a positively charged polymer. The as-prepared hsZSM5 can function as a spacer: different metals (M_n) can be preferentially separated by the thin shell of hsZSM5, making the derived M₁@hsZSM5@M₂ suitable for tandem reactions. The dual-layer Co@hsZSM5@Pt shows higher resistance to metal sintering and alloying in tandem hydrogenation of CO₂ (i.e.; reverse water gas shift reaction followed by Fischer–Trøpsch reaction) to short-chain hydrocarbons, which can be used as an alternate clean feedstock to produce chemicals such as olefins, aromatics and polymers. Hydrocarbon selectivity of C₂₊ can be increased up to 46% in Co@hsZSM5@Pt, which was not observed in co-impregnated Pt–Co catalyst.