日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Recent development of microporous crystalline Mo-V mixed oxides (MoVO) are reviewed. MoVO is formed by a self-assembly of structural units supplied by the boll-shaped large polyoxometalate, [Mo₇₂V₃₀O₂₈₂(H₂O)₅₆(SO₄)₁₂]^36-({Mo₇₂V₃₀}), resulting in the formation of a sophisticated crystal structure. Addition of MoVO seed crystal into the precursor solution of MoVO induced the crystal formation of MoVO having the same crystal structure with the seed crystal. Comparison of catalytic activities of 4 distinct MoVO catalysts with the same elemental composition and with different crystal structure clearly demonstrated a strong dependence of the crystal structure on the catalytic activity for the selective oxidation of ethane and acrolein. Then, catalysis field of MoVO for selective oxidations were investigated by using MoVO catalysts with the same microporosity and with the difference external surface area. It was proved that ethane, accessible into the micropore, is converted to ethene inside the micropore without diffusion effect. On the other hand, acrolein which is inaccessible into the micropore is converted to acrylic acid at the mouth of the micropore. Proper redox treatment for MoVO leaded a partial structural change around the micropore which strongly affected its microporosity and the catalytic performance of the ethane oxidation. The significant role of the micropore for the selective oxidation of ethane was observed. On the basis of the comprehensive studies, molecular-level insight of the selective oxidation by using MoVO could be obtained.