Effect of la2O3 in carbon deposition on Pt/Al 2O3 during methylcyclopentane reaction

In this work, we have studied the effect of the addition of lanthanum oxide to Pt/Al2O3 catalysts on its catalytic properties and its resistance to coke deactivation. The catalysts used contained 1.0 wt % in Pt, dispersed on three different supports: γ-Al2O3 (Pt/A), La2O3 (Pt/L), and a mixture (50:50 wt %) of La2O3-γ-Al2O3 (Pt/ AL). All the samples were characterized by X-ray diffraction (XRD), BET analysis, and temperature-programmed reduction (TPR). TPR profiles evidence the presence of an important interaction between Pt and La2O3. The activity and selectivity of the catalysts were evaluated in the hydrogenolysis of methylcyclopentane (MCP) reaction. The specific initial rates showed the following order: Pt/A Pt/AL Pt/L. Regarding selectivity, the three samples were all alike. The ratios of specific rates, final to initial, were: Pt/A 0.68; Pt/AL 0.50; Pt/L 0.52. The amount of carbon deposited on the Pt/AL catalyst was comparable to that on Pt/A, and both were smaller than the one deposited on Pt/L. The characterization of deactivated samples by TPO, Fourier transform infrared (FTIR), 27Al MAS (magic-angle spinning) NMR and 13C MAS NMR showed differences in the coke nature between the samples. The results point out lanthana sites with differences responses to carbonaceus residues. © 2007 American Chemical Society.