Zn modulating the metal support interaction to promote the sintering resistance of hydrotalcite-derived NiZnAl catalyst for methane cracking

Abstract

Developing an efficient and environmentally friendly catalyst is important for the production of pure H₂ and carbon nanomaterials. Catalytic cracking of methane offers the possibility of producing these high-value products. For this reason, stabilizing the surface active sites of activated methane by modulating the interaction between metal and support has attracted much attention in the development of hydrotalcite-derived NiAl catalysts. Hence, the influence of Zn content and cracking temperature on the structure and performance of hydrotalcite-derived NiZnAl methane cracking catalysts were investigated. It is shown that alloying Zn with Ni reduces the electron density near Ni atoms, promotes the reduction of mixed metal oxides, producing strong interactions between Ni and support, thus improving the stability of the catalyst during methane decomposition. Thus, this strong interaction between Ni and support stabilized the Ni particle size and inhibited the sintering of Ni during the reaction. The Ni_2.7Zn_0.3Al can maintain a H₂ yield of more than 60 % over a 600 min reaction time at 600 °C. TEM analysis showed that the strong metal support interaction changed the morphology of the deposited carbon, maintained the balance between carbon diffusion and CH₄ dissociation, provided more growth sites for carbon nanotubes, and also prevented the rapid deactivation of the catalysts because of carbon encapsulation. This article may provide guidance for the design of Ni-based methane cracking catalysts with excellent stability.