Hydroisomerization and Hydrocracking of Alkanes. 6. Influence of the Pore Structure on the Selectivity of Pt-Zeolite

  • Giuseppe Giannetto
  • Fernanda Alvarez
  • Fernando Ramoa Ribeiro
  • Guy Pérot
  • Michel Guisnet
Part of the NATO ASI Series book series (NSSB, volume 221)


Bifunctional metal-acid zeolites are used in numerous industrial processes in petroleum refining and in petrochemical industries1–3: hydrocracking, hydroisomerization of light alkanes or of C8 aromatics… On these catalysts alkane hydrocracking requires i) chemical steps on the metallic sites (dehydrogenation of alkanes and hydrogenation of olefinic intermediates) and on the acid sites (isomerization and cracking of olefins) and ii) diffusion steps of the intermediates from the metallic sites to the acid sites and vice versa 3. Therefore the activity, the stability and the selectivity of these bifungtjonal catalysts depend first on the acid and on the metallic functions3,4. We have recently shown in n-heptane transformation on PtHY catalysts that a definite correlation exists between the catalytic properties and the balance between the metallic and the acid functions characterized by nPt/nA, the ratio of the number of accessible platinum atoms to the number of strong acid sites (sites on which the heat of ammonia adsorption is greater than 100 kJ per mol). Thus for low values of this ratio the activity is low, the deactivation rapid and apparently n-heptane leads directly to all the isomerization and cracking products. For high values the activity is great, the deactivation very slow and n-heptane transforms successively into monobranched isomers, dibranched isomers and cracking products.


Acid Site Strong Acid Site Light Alkane Ammonia Adsorption Catalytic Characteristic 
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Copyright information

© Plenum Press, New York 1990

Authors and Affiliations

  • Giuseppe Giannetto
    • 1
  • Fernanda Alvarez
    • 2
  • Fernando Ramoa Ribeiro
    • 2
  • Guy Pérot
    • 3
  • Michel Guisnet
    • 3
  1. 1.Escuela de Ingenieria de PetroleoUniversidad Central de VenezuelaCaracasVénézuela
  2. 2.Instituto Superior TecnicoLisboa CodexPortugal
  3. 3.URA CNRS DO350, Catalyse en Chimie OrganiqueUniversité de PoitiersPoitiers CedexFrance

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