Effect of synthesis pH on the structure and catalytic properties of FeMo catalysts

Shuai Zhang; Minghan Han

doi:10.1039/c9ra07202k

Effect of synthesis pH on the structure and catalytic properties of FeMo catalysts

RSC Adv. 2019 Dec 17;9(71):41720-41728. doi: 10.1039/c9ra07202k. eCollection 2019 Dec 13.

Authors

Shuai Zhang¹, Minghan Han¹

Affiliation

¹ Department of Chemical Engineering, Beijing Key Laboratory of Green Reaction Engineering and Technology, Tsinghua University Beijing 100084 China hanmh@tsinghua.edu.cn.

Abstract

The effect of pH on polynuclear molybdenum species (isopolymolybdates) synthesis was investigated by Raman spectroscopy. As the pH decreased from 6.0 to 1.0, the main isopolymolybdates changed from MoO₄ ^2- to Mo₇O₂₄ ^6- to Mo₈O₂₄ ^6- to Mo₃₆O₁₁₆ ^8-. They began to aggregate and their solubility decreased with decreasing pH. The FeMo catalysts comprised particle- and plate-like structures, which were Fe₂(MoO₄)₃ and MoO₃, respectively. When a low pH value was used in the catalyst preparation, there was severe aggregation of the particles which have a high Mo/Fe mole ratio and Mo enrichment on the surface layer, which decreased the activity and selectivity of the FeMo catalyst.