RE2O3-promoted Pt–SO42−/ZrO2–Al2O3 catalyst in n-hexane hydroisomerization

Lanthanum, cerium and ytterbium nitrates used as RE oxide precursors, RE2O3-promoted PSZA catalysts for n-hexane hyroisomerization were prepared and RE2O3 promotion effects on catalytic activity and catalytic stability were investigated by N2-adsorption, XRD, TG, FTIR, XPS and H2-TPR. It was elucidated that the introduction of RE2O3 into Pt–SO42−/ZrO2–Al2O3 (PSZA) increased both the surface area and the number of active sites, resulting in a higher n-hexane isomerization activity. At the same time the catalyst stability has also been markedly increased by alleviating the sulfur loss and by stabilizing ZrO2 tetragonal crystalline structure. In addition, XPS for the spent catalysts showed during n-hexane hydroisomerization reaction a relative small amount of S6+ species was reduced to S4+, and the amount of the most active sulfate entities decided the overall amount of n-hexane transformed, their reduction being, perhaps, retarded by the RE2O3 addition to PSZA. The promotion effects of RE oxides addition decreased in the order: La2O3 > Yb2O3 > Ce2O3.