Pt-Re-Sn/Al2O3 trimetallic catalysts for naphtha reforming processes without presulfiding step Original Research Article

The n-heptane reforming and the cyclopentane hydrogenolysis reactions over noble metal monometallic catalysts (0.3% Pt), bimetallic catalysts (0.3% Pt, x% Re, x = 0.1, 0.3, 0.9 and 2.0, sulfided) and trimetallic catalysts (0.3% Pt, 0.3% Re, y% Sn, y = 0.1, 0.3, 0.6 and 0.9, unsulfided) were studied. The metal function was supported over a chlorided γ-alumina that provided the acid function. The reforming of n-heptane was performed at 450 °C, molar ratio H2/n-C7 = 4 and WHSV = 7.3 while the hydrogenolysis of cyclopentane was performed at 350 °C, H2/CP = 20 and WHSV = 2.4.The sulfided 0.3Pt-0.3Re catalyst (with 0.06% S) was found to be the best performing bimetallic one. It had a great stability, typical of this kind of catalysts, and also produced a reformate with a high iso-heptanes/toluene ratio. This is advantageous for fulfilling the current environmental regulations that limit the amount of aromatic hydrocarbons in reformulated gasolines. The best trimetallic catalyst was 0.3Pt-0.3Re-0.6Sn which had a similar activity and selectivity as sulfided 0.3Pt-0.3Re, though it displayed a higher stability and a lower hydrogenolysis activity, without the need of presulfidation. Tin affected the metal and acid functions of the catalyst simultaneously and inhibited them to such different degrees that a very convenient metal/acid activity ratio was obtained, resulting in an improvement of the activity, selectivity and stability of the catalysts.