Physicochemical and Isomerization Property of Zn-Pt/SAPO-11 Catalysts Promoted by Zn

Monometallic catalyst Pt/SAPO-11 was prepared by impregnation method. Bimetallic catalyst Zn-Pt/SAPO-11 was prepared by sequential impregnation method. X-ray diffraction (XRD), nitrogen adsorption, temperature-programmed desorption of ammonia (NH(3)-TPD) and Fourier transform infrared spectroscopy (FT-IR) techniques were employed to analyze the natures of catalysts. The results show that the BET surface areas, porous volume and the number of Bronsted acid decrease slightly with the addition of metal additive Zn. However, the addition of additive Zn leads to an increasement in the number of Lewis acid and the total acidity of the catalyst. In addition, the catalytic performances of catalysts for the hydroisomerization of n-heptane at 300 similar to 380 degrees C were studied. The conversion of n-heptane is varied significantly and the selectivity of C(7) isomers is not obviously affected by the addition of Zn to Pt/SAPO-11 catalyst. A maximum n-heptane conversion and C(7) isomers yield over the Zn-Pt/SAPO-11 catalyst containing 0.2 wt% Zn and 0.2 wt% Pt is observed. However, further increase in Zn addition leads to a fall in the n-heptane conversion and C(7) isomers yield. The results show that the synergistic effect between metallic function and acid function is very important for the bifunctional catalyst over the n-heptane hydroisomerization reaction.