Insight in cyclohexene hydroconversion process using catalysts containing 0.35% Pt on amorphous and zeolite supports

Commercial non crystalline silica and gamma-alumina were used as supports, whereas Na-Y, Na-ZSM-5 and Na-MOR-zeolites were exchanged with NH4NO3 to obtain the corresponding NH4-zeolites and calcined producing the H-zeolites which were then impregnated with H2PtCl6 to obtain 0.35% Pt on each support. These catalysts were characterized via TPD, TPR, XRD and Pt dispersion using H-2 chemisorption and tested for cyclohexene hydroconversion in atmospheric flow-type reactor. TPR of the calcined samples showed that PtOx species supported on SiO2 were the most easily reducible among all catalysts, i.e., at 80 degrees C, since SiO2 acquires the weakest Pt-support-interaction. Hence, Pt particles dispersion on SiO2 was the lowest (28.2%) and this catalyst was the least active for cyclohexene hydroconversion. However, the P/gamma-alumina catalyst exhibited the highest hydrogenation and dehydrogenation activities due, principally, to acquiring the highest Pt dispersion (86.5%). In general, the zeolite loaded catalysts possessed higher Pt-support interaction compared to very weakly acidic amorphous catalysts. The most acidic zeolite supported catalysts (Pt/H-MOR and Pt/H-ZSM-5) possessed the highest hydroisomerization and hydrocracking activities by virtue of their higher acid site strength. Although, Pt/H-ZSM-5 acquires lower acid sites number and strength than Pt/H-MOR, it is found more active for these reactions. We assume that the more active Bronsted acid sites in H-ZSM-5 have overcompensated the higher acidity of Pt/H-MOR. The Pt/HY catalyst, although acquires the largest acid site density and widest channels, it is the least active zeolite for CHE isomerization and hydrocracking most probably due to its weaker acid sites strength. Published by Elsevier Ireland Ltd on behalf of Taiwan Institute of Chemical Engineers.