Synthesis, Characterization, and CO2 Methanation Over Hierarchical ZSM-5-NiCoAl Layered Double Hydroxide Nanocomposites: Improvement of C-C Coupling to Ethane.

Abstract

To date, preparing materials with highly dispersed metal nanoparticles without metal agglomeration on a solid support is challenging. This work presents an alternative approach for synthesizing NiCo species on hierarchical ZSM-5 materials derived from a ZSM-5@NiCoAl-LDHs composite. The designed material was prepared by the growth of a NiCo-layered double hydroxides (LDHs) precursor on the surface of hierarchical ZSM-5 nanosheets. The effect of the weight ratio of NiCo-LDHs precursor to ZSM-5 on the composite properties has been studied. The results show that 45 wt.% LDHs (ZSM-5@NiCoAl-LDHs-45) is the most suitable condition for preparing NiCoAl-LDHs/ZSM-5 composite, which promotes a strong interaction between bimetallic NiCo and hierarchical ZSM-5. The ZSM-5@NiCoAl-LDHs-45 showed a BET surface of 386 m² g^-1, in which the surface area has been re-allocated between microspores and mesopores due to the presence of NiCoAl-LDHs composite. The catalyst was also tested for CO₂ methanation at 380 °C under atmospheric hydrogen pressure. The results show that the catalyst could provide CO₂ conversion of up to 40 % at WSHV of 2.91 h^-1. Interestingly, it could not only promote methane but also provide a high selectivity of ethane, approximately 20.4 %. Moreover, the excellent catalytic stability of ethane production was illustrated over 24 hours of time-on-stream (TOS).