Effect of rare earth doping on property of S₄^2-/ZrO₂/ Al₂O₃ catalyst

Impregnation-precipitation method was applied to support the nano ZrO₂ onto the Al₂O₃ with bigger surface area to prepare the supported nano-ZrO₂/ Al₂O₃ composite supports. A series of rare earth oxides such as scandium oxide and praseodymium oxide, neodymium oxide were doped into ZrO₂/Al₂O₃ composite supports to improve the surface properties of ZrO₂. The SO₄^2-/ RE_xO_y-ZrO₂/ Al₂O₃ catalysts were obtained by supporting S₄^2- onto the composite supports doped by rare earth oxides. Crystalline structures, surface area, pore diameter distribution and acid properties of the catalysts were characterized by XRD, BET, in-suit FTIR, and TPD. The α-pinene isomerization reaction was chosen to investigate the catalytic properties of the catalysts. The results indicated that there was no change in the crystalline structures of the ZrO₂. And the grain size of the ZrO₂ was decreased and the surface area of the catalysts was increased. The existence of the rare earth oxide changed the coordination mode of SO₄^2- which had the directive influence on the acid site number and acid strength to increase the activity of the catalysts. The pore structure had great influence on the selectivity of the catalysts.