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Keywords:

  • aromaticity;
  • mesoporous materials;
  • microporous materials;
  • surface chemistry;
  • Zn/ZSM-5

Abstract

Three Zn/ZSM-5 catalysts with Si/Al ratios of 17, 33, and 42 were treated with a weak base (Na2CO3) to create a hierarchical microporous–mesoporous system and to improve the catalyst stability in the aromatization of 2-methly-2-butene, a model compound that represented branched olefin byproducts that are produced from fluidized catalytic cracking. The Si/Al ratio of the parent ZSM-5 had a critical effect on the nature of the modified pore system. Thus, for Zn/ZSM-5 with a Si/Al ratio of 42, a hierarchical microporous–mesoporous system was formed in which intraparticle bimodal mesopores were in the form of cavities and cylinders, the latter of which connected internal micropores to the external surface of the catalyst. This pore structure was most suitable for enhancing the tolerance to coking and brought a dramatic increase in the catalyst stability in the aromatization of 2-methyl-2-butene.