Catalytic performances of dealuminated Hβ zeolite supported Pt catalysts doped with Cr in hydroisomerization of n-heptane

A series of dealuminated Hβ zeolite supported Pt catalysts doped with Cr, Ce, La or Zn were prepared via co-impregnation and characterized by X-ray diffraction (XRD), BET, NH3-TPD, H2-TPR, ICP, and H2-chemisorption techniques. The catalytic performance was evaluated in hydroisomerization of n-heptane with an atmospheric fixed bed flow reactor. At the reaction temperature 250 °C, Hβ zeolite supported Pt catalyst showed a low selectivity to isomerized products 47.3% with a high conversion of n-heptane 83.9%. By dealuminating the Hβ support with steaming and acid leaching, a high selectivity to isomerized products 96.4% with considerable conversion 52.3% was observed. Moreover, by doping Cr (La or Ce) into the Pt/dealuminated Hβ catalyst, a further increase of the selectivity to isomerized products was obtained. The optimal composition for Cr-doped Pt/dealuminated Hβ catalysts was 0.4 wt% of Pt loading and 5:1 of molar ratio of Cr to Pt. This catalyst proves to be a highly efficient catalyst for the hydroisomerization of n-heptane, giving a very high selectivity to isomerized products 97.0% with the conversion of n-heptane 65.5% at the reaction temperature 270 °C. The promotion effect of Cr is discussed in relation to the catalyst acidity and the dispersion and reducibility of the supported Pt.