Estudio sobre la conveniencia del agregado de Ni o Pt a WO42--ZrO2 en reacciones de hidroisomerización-craqueo de parafinas pesadas

J.C. YORI; V.M. BENÍTEZ; J.M. GRAU; C.R. VERA; C.L. PIECK; J.M. PARERA

Foz do Iguacu, PR - Brasil

Congreso; 13º Congresso Brasileiro de Catálise 3º MercoCat; 2005

The production of C4-C6 isoparaffins by hydroisomerization and cracking of n-octane (n-C8) (300 °C, 1 atm) with a WO3-ZrO2 (WZ) catalyst promoted with Pt or Ni was studied in this work. The effect of both promoters on the two catalytic functions (acid and metallic) was analyzed by means of temperate programmed reduction, temperature programmed desorption of pyridine and tests reactions specific to each function (isomerization of n-C4 and dehydrogenation of cyclohexane).  A different behavior is seen depending on the amount of Ni loaded, at low amounts (0,1 and 0,5%) or high amounts (1,0 and 5,0%).  At the reactions conditions used in this test, Ni is found as NiO at low Ni concentrations.  At high Ni concentrations a fraction of the Ni is present as a metal.  Pt is present mainly as a finely dispersed metal phase.  Both Ni and Pt modify the acidity of WZ, though in a different way.  Ni has a higher promoting effect than Pt and its effect is to increase the total acidity and concentration of strong acid sites.  The results of isomerization-cracking of n-C8 show an increase of the total conversion in the Pt and Ni promoted catalysts in comparison to the unpromoted ones.  Upon Ni loading there is also an increase of the cracking capacity of the support and an enhancement of the production of isoparaffins, a fact that is compatible with the increase of the octane number (RON) of the reaction products.  This increase in the RON is proportional to the production of light gases (fracción C1-C3) so there is a compromise between increasing the octane number and keeping a cost-effective liquid yield.