Composite Assisted Approach for the Synthesis of Ni@SiO₂-ZrO₂ Catalysts and Their Performance Evaluation in Methane Dry Reforming

The work here reports a new and versatile approach for distributing metal nanoparticles within an encapsulating nonhydrolytic sol-gel metal oxide framework. The method uses a metal-chitosan composite material as a sacrificial precursor, which allows for easy expansion to a range of encapsulating metal oxides as well as different active metal specie. To demonstrate this catalyst synthesis approach, we examined the distribution of Ni particles within an encapsulating SiO₂-ZrO₂ support. We show that the grafting of Si-sites on the chitosan backbone, the solvent used, and the drying rate can be controlled to obtain a high surface area composite of up to 178 m²/g. The effects of the initial composite surface area, the Si content, and Ni loading in the materials, obtained following encapsulation in the zirconia gel and calcination, are examined with respect to Ni distribution in the calcined material. Using methane dry reforming as a probe reaction, it is shown that the encapsulated Ni catalysts have higher activity (XCH₄ = 33%; XCO₂ = 41%) as compared to the impregnated catalyst (XCH₄ = 26%; XCO₂ = 32%). This result was obtained despite the higher NiO distribution on the impregnated supports and demonstrates the promoting effect of the encapsulation.