Tailoring the Synergistic Bronsted-Lewis acidic effects in Heteropolyacid catalysts: Applied in Esterification and Transesterification Reactions

摘要

In order to investigate the influences of Lewis metals on acidic properties and catalytic activities, a series of Keggin heteropolyacid (HPA) catalysts, H_nPW₁₁MO₃₉ (M?=?TiIV, CuII, AlIII, SnIV, FeIII, CrIII, ZrIV and ZnII; for Ti and Zr, the number of oxygen is 40), were prepared and applied in the esterification and transesterification reactions. Only those cations with moderate Lewis acidity had a higher impact. Ti Substituted HPA, H₅PW₁₁TiO₄₀, posse lower acid content compared with Ti_xH_3?4xPW₁₂O₄₀ (Ti partial exchanged protons in saturated H₃PW₁₂O₄₀), which demonstrated that the Lewis metal as an addenda atom (H₅PW₁₁TiO₄₀) was less efficient than those as counter cations (Ti_xH_3?4xPW₁₂O₄₀). On the other hand, the highest conversion reached 92.2% in transesterification and 97.4% in esterification. Meanwhile, a good result was achieved by H₅PW₁₁TiO₄₀ in which the total selectivity of DAG and TGA was 96.7%. In addition, calcination treatment to H₅PW₁₁TiO₄₀ make it insoluble in water which resulted in a heterogeneous catalyst feasible for reuse.