Acid strength of Ni–S₂O ²⁻₈ /ZrO₂ catalyst and its catalytic activity for n-pentane isomerization

Abstract

A series of bifunctional Ni–S₂O₈ ²⁻/ZrO₂ (Ni _x -SSZ-T) catalysts with different Ni mass fraction (x, %) and calcintion temperature (T, °C) were prepared by impregnation method. The catalysts were characterized by XRD, FTIR, and py-FTIR. The effects of Ni content and calcination temperature on the acidic property and isomerization performance of catalyst were investigated using n-pentane isomerization as a probe reaction. The results show that the acidity of Ni _x -SSZ-T catalysts mainly derives from L acid. The addition of a suitable amount of Ni can induce the formation of more acid sites and in turn enhance the isomerization performance of Ni _x -SSZ-T catalyst. With increasing the calcination temperature from 550 to 700°C, B acid strength of catalyst weakens gradually, while the L acid strength increases first and then decreases. The Ni _x -SSZ-T catalyst with Ni content of 1 wt % and calcination temperature of 650°C exhibits the best isomerization performance. At reaction temperature of 230°C, pressure of 2. 0 MPa hydrogen /hydrocarbon molar ratio of 4: 1, and weight hourly space velocity (WHSV) of 1.0 h⁻¹ the isopentane yield reaches 57.0%.