Effects of doping Y on crystal structure and catalytic activity of α-Bi₂Mo₃O₁₂

Abstract

The single phase Y_0·2Bi_1·8Mo₃O₁₂ and α-Bi₂Mo₃O₁₂ catalysts have been synthesised by solid state reaction, and the Y_0·2Bi_1·8Mo₃O₁₂ shows better catalytic performance than α-Bi₂Mo₃O₁₂ in the selective oxidation of isobutene to methacrolein. X-ray powder diffraction structural analysis, X-ray photoelectron spectroscopy and O₂ temperature programmed desorption have been used to reveal the effects of doping Y on the crystal structure and catalytic activity of α-Bi₂Mo₃O₁₂ induced by Y substitution for Bi. It is found that when Bi in α-Bi₂Mo₃O₁₂ crystal structure is partially substituted by Y with lower electronegativity, the electronic densities of oxygen will increase, which could improve the rate determining α-H abstraction at Bi sites in the selective oxidation of isobutene to methacrolein. On the other hand, the partially regularised MoO₄ tetrahedra also promote the catalytic selectivity to methacrolein due to the decrease in oxidation ability. Besides, the longer interatomic distances between Mo3 and Bi in the principal cleavage plane (010) and (010) might result in the lesser catalytic activity of Mo3 sites.

Keywords:

• BISMUTH MOLYBDATE
• SELECTIVE OXIDATION
• YTTRIUM
• X-RAY DIFFRACTION