Dual rare earth-doped Pt–Sn/Al2O3 catalysts with synergistic Ce and Sm effects on high-efficiency aromatization and coke suppression in naphtha reforming

In the present study, the effect of rare earth (RE) metals of Ce and Sm on the naphtha reforming process catalyst, i.e., Pt-Sn/γ-Al₂O_3, is investigated. Two-, three-, and four-metal catalysts were synthesized through the successive wet impregnation of the support, employing various concentrations of cerium at 0.17 and 0.47 wt% and samarium at 0.33, 0.51, and 0.87 wt%. The corresponding catalytic activity on the naphtha reforming reactions was conducted in a reactor at 5 bar, 500 ℃, and WHSV = 2 h^{- 1}. FESEM, BET, NH₃-TPD, and H₂-TPR were employed to scrutinize the physicochemical and active site properties of the developed catalysts. Besides, TGA was used to determine the deactivation rate of the developed catalysts. It is shown that adding a suitable amount of RE metals can reduce the Pt particle agglomeration and promote the distribution of the metal particles. Catalytic testing demonstrated that Ce and Sm-containing catalysts, especially SPC(0.47)S(0.33), exhibited superior aromatization activity, producing high levels of C₈ and C₉ aromatics, which are valuable for gasoline blending. Such catalysts also showed reduced cracking and paraffin production, which was attributed to the optimal balance of metallic and acidic properties resulting from the REMs. In addition, such RE dopants could diminish the degree of graphitization, resulting in decreased coke content and a lower combustion temperature, facilitating the catalyst regeneration process. Moreover, incorporating RE metals could inhibit the reduction of tin oxides, enhancing platinum's role as the promoter. Besides, the catalysts containing 0.47 wt% cerium, 0.33 wt% samarium and a combination of both RE metals exhibited superior activity in producing reformate with a high-octane number.