Effect of metal precursor solvent on n-dodecane isomerization of Pt/ZSM-22

A series of Pt/ZSM-22 bifunctional catalysts were prepared by using different metal precursor solvents including water, methanol, acetone and acetic acid. The phase structure, texture properties, metal properties and acidity were systematically investigated by XRD, BET, TEM, CO-chemisorption, CO-FTIR and Py-FTIR. The effect of metal precursor solvents on n-dodecane isomerization was also studied. The results indicate that the solvents with different polarities lead to different locations of Pt particles. Part of Pt particles locate on ZSM-22 when methanol, acetone and acetic acid are used as solvents, and the interaction between Pt and acid sites lead to the electron-deficient of Pt. However, the Pt particles almost locate on the Al₂O₃ binders when water is used as solvent, and their electronic properties are little affected. Higher activity and selectivity are achieved when Pt particles locate on ZSM-22 in the n-dodecane isomerization reactions. These results indicate that shorten the distance between acid sites and metal sites can expedite the diffusion of reactants and isomerized intermediates to proceed dehydrogenation and hydrogenation reactions.