Selectivity improvement in the aromatization of C-2-C-5 alkanes using polyfunctional metallosilicate catalysts

Improvement in selectivity in the aromatization of n-C4H10 and n-C5H12 Was investigated on Pt-incorporated H-Ga- or H-Zn-silicate (designated as H-Pt . Ga- or H-Pt . Zn-silicate) prepared by the addition of Pt at the stage of mixed:gel formation for preparing the precursor of the crystals. The perfo rmance of these catalysts was compared with that on Pt-ion-exchanged H-Ga- or H-Zn-silicate (designated as Pt/H-Ga-silicate, Pt/H-Zn-silicate), The co nversion of C-2-C-5 saturated hydrocarbons on H-Pt . Ga- or H-Pt . Zn-silic ate was lower than that on Pt/H-Ga- or Pt/H-Zn-silicate, but still higher t han that on Pt-free H-Ga- or H-Zn-silicate catalyst. On the Pt-incorporated catalysts, the selectivity to light aromatics and/or olefinic hydrocarbons increased, indicating that activities for cracking, alkylation of benzene ring, hydrogenation, and dehydrogenation caused by Pt could be moderated by incorporation of Pt into the crystals. On the other hand, activities of de hydrogenation and aromatization caused by Ga or Zn were exerted more explic itly. These are attributed to the difference of the Pt state between Pt-inc orporated and Pt-ion-exchanged catalysts, which could be compared through m easurements of CO adsorption and TEM observation. (C) 2000 Elsevier Science B.V. All rights reserved.