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

A series of dealuminated HP 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, H-2-TPR, ICP, and H-2-chemisorption techniques. The catalytic performance was evaluated in hydroisomerization of n-heptane with an atmospheric fixed bed flow reactor. At the reaction temperature 250 degrees C, H beta 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 H beta 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 H beta catalyst. a further increase of the selectivity to isomerized products was obtained. The optimal composition for Cr-doped Pt/dealuminated H beta 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 degrees C. The promotion effect of Cr is discussed in relation to the catalyst acidity and the dispersion and reducibility of the supported Pt. (C) 2008 Elsevier B.V. All rights reserved.