In situ powder X-ray diffraction study of the process of NiMoO4–SiO2 reduction with hydrogen

Abstract

An interest in NiMoО₄–SiO₂ reduction stems from its promising use as catalysts for hydrodeoxygenation and hydrodesulfurization processes. The work exploits in situ X-ray diffraction to investigate phase transformations during NiMoO₄–SiO₂ reduction with hydrogen in a temperature range of 30-700°C. The α-NiMoО₄ reduction is shown to proceed in two stages. In the first stage, at 400-500°C, an intermediate state (Ni,Mo,□)O mixed oxide and Ni_1–xMo_x form. In the second stage, above 650°C, two solid solutions based on the Mo and Ni structures form. The structure of the intermediate state is refined by the Rietveld method. It is demonstrated that the Ni–Mo mixed oxide forms based on the NiO structure, which contains a certain number of cation vacancies.