Rare Earth Metals Ion-exchanged β-Zeolites as Supports of Platinum Catalysts for Hydroisomerization of n-Heptane

A series of Pt catalysts supported on the Hβ-zeolite that is ion-exchanged with the rare earth metal ions of Ce(III) and La(III), are prepared by impregnation, characterized by inductively coupled plasma (ICP), X-ray diffraction (XRD), BET, temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed reduction of hydrogen (H2-TPR) and H2-chemisorption techniques, and evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The reaction temperature, time on stream, space velocity, and the ratio of H2/n-heptane are changed to get the optimal conditions. The Ce(III) and La(III)-exchanged Hβ-zeolites exhibit higher selectivity for isomerized products than the neat Hβ-zeolite. Moreover, the Ce(III)-exchanged catalysts give higher conversions of n-heptane, whereas the La(III)-exchanged ones do not show any improvement in conversion. Under optimal conditions, the catalyst with 0.4% (by mass) Pt and 0.5% (by mass) Ce loading presents very high selectivity of isomerized products of 95.1% coupled with high n-heptane conversion of 68.7%. Effects of the ion-exchange of Ce(III) and La(III) on the catalytic performance are discussed in relation with the physicochemical properties of catalysts.