N Parsafard - Departmentof chemistry, Shahid Beheshti University, Tehran, ۱۹۸۳۹۶۳۱۱۳, Iran
M.H Peyrovi - Departmentof chemistry, Shahid Beheshti University, Tehran, ۱۹۸۳۹۶۳۱۱۳, Iran

Pt loaded on a series of ZSM-5/HMS composites with different H-zeolite amounts has been prepared and used as a solid acid catalyst for n-heptane isomerization that compared as a function of H-zeolite content. The structure characterization, acid distribution and morphology of the Pt catalysts supported on these composite materials were characterized by XRD, NH3–TPD, SEM, FTIR, nitrogen sorption and TGA techniques. Compared with HMS and HZSM-5, these new composite materials have higher ability for n-heptane isomerization reaction. The results show that these micro/mesoporous catalysts exhibit both properties of mesoporous HMS and microporous HZSM-5. TPD measurements showed that the acidity of HZSM-5/HMS materials enhanced with the increasing zeolite content. Results showed that the ratio of BrÖnsted/Lewis acidic sites increased with the increasing zeolite content. The catalytic evaluation revealed that Pt/ZSM5-HMS catalysts had a high activity for conversion of n-heptane. The distribution of products was described based on the nature of the acidic sites. These new composite catalysts prove a higher thermal stability, which result in their thicker pore-wall, and appropriate acidity.

ZSM-5/HMS composites; Catalytic isomerization; Acid distribution; Morphology; Thermal stability