CONVERSION OF HEAVY N-ALKANES INTO LIGHT ISOMERS OVER H-MORDENITE, PLATINUM/H-MORDENITE, PLATINUM/ALUMINA AND COMPOSITE CATALYSTS

H-MOR, chlorided Al2O3, Pt/H-MOR, Pt/Al2O3, Pt-Re/Al2O3 and some of their mixtures were used as catalysts in the isomerization-cracking of pure n-alkanes (n-C-7 to n-C-12) and two paraffinic commercial cuts at 1.5 MPa, 473-773 K, H-2:n-alkane=6 and weight hourly space velocity=4. Depending on the degree of conversion, the sequence of reactions on all catalysts was: isomerization, central and successive cracking. The activity and selectivity to light isomers increase with the increase in platinum concentration using Pt/H-MOR. The conversion increases with the chain length of the n-alkane, presenting an optimum temperature at which light isomers production is maximum. Ratios isoalkane/n-alkane higher than those corresponding to thermodynamic equilibrium are obtained. H-MOR is deactivated due to the production of a large amount of coke, which greatly decreases the specific surface area and pore volume of the zeolite. The synergy produced by the addition of platinum decreases deactivation and increases the selectivity to isoalkanes. A composite catalyst obtained by pressing powders of H-MOR and Pt/Al2O3 (platinum is in this case outside the zeolite particle) showed the best synergetic effect, which depends on the contact of the particles and which is ascribed to hydrogen spillover from platinum to H-MOR. This spillover decreases coke formation on and blocking of the surface of H-MOR.