Acid properties and catalytic performance for phosphonic acid modified MCM-49 zeolites in skeletal isomerization of n-butene

The acid properties of MCM-49 zeolites were modified by phosphonic acid via a simple impregnation method. The physicochemical properties of the samples were well characterized by XRD, NH3-TPD, FT-IR of d3-acetonitrile adsorption, 27Al MAS NMR, and their activity in the skeletal isomerization of n-butene was measured as well. It was found that the concentrations of Brønsted and Lewis acid sites have been markedly reduced by the phosphonic acid impregnation. The catalytic results indicated that Brønsted acid sites were active sites for the skeletal isomerization of n-butene, while Lewis acid sites almost had no effect.