On the enhanced selectivity of HZSM-5 modified by chemical liquid deposition

S. Zheng, H. R. Heydenrych, H. P. Röger, A. Jentys, J. A. Lercher

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62 Scopus citations

Abstract

The external surfaces and pore mouth regions of HZSM-5 samples with different crystal sizes were modified by chemical liquid deposition (CLD) with tetraethoxysilane, which led to the passivation of unselective acid sites. The modification was more effective for zeolite samples of larger crystal size. The diffusivity of o-xylene was substantially reduced after silylation, while the diffusivity of toluene hardly changed. Dealumination of the external surface of the zeolite crystals enhanced the silylation effects. This was related primarily to the removal of acid sites related to extra-framework alumina. For the modified catalysts, a significant increase in the selectivity to p-xylene in the disproportionation of toluene was achieved. CLD led to a narrowing of the pore openings of the zeolite and to a restricted o-xylene diffusion into the pores of HZSM-5.

Original languageEnglish
Pages (from-to)101-106
Number of pages6
JournalTopics in Catalysis
Volume22
Issue number1-2
DOIs
StatePublished - Jan 2003

Keywords

  • Chemical liquid deposition
  • Shape selective catalysis
  • Silylation
  • Toluene disproportionation
  • ZSM-5

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