Effects of metal promoters on one-step Pt/SAPO-11 catalytic hydrotreatment of castor oil to C₈-C₁₆ alkanes

a series of Pt/SAPO-11 catalysts were synthesized by using incipient wetness impregnation method with SAPO-11 molecular sieve as the carrier and the active mental component Pt. The properties of the catalysts were changed by adding different metals: La, Ce, Sn, Fe, Co, Ni, Cu and Zn. Using castor oil as the model molecular probe, a one-step continuous catalyzed hydrogenation preparation of bio-aviation kerosene was carried out in a high pressure micro fixed-bed reactor. The effects of bimetallic multifunctional catalysts with an auxiliary metal agent on hydrodeoxygenation performance, the selectivity of C₈-C₁₆ alkanes, the selectivity of C₈-C₁₆ iso-alkanes and the selectivity of C₈-C₁₆ arene were evaluated systematically. Three catalysts with good comprehensive performances, namely, Pt-La/SAPO-11, Pt-Ce/SAPO-11, Pt-Co/SAPO-11, were selected for characterization with XRF, XRD, BET, TEM, H₂-TPR, NH₃-TPD and Py-IR. The relationship between macroscopic catalytic properties and micro structure of the selected catalysts was discussed. It was found that the addition of La, Ce and Co reduced the specific surface area, pore volume and average pore diameter of SAPO-11 molecular sieve carrier, but increased the acid sites and total acid sites of the carrier, decreased the crystalline size of the active component Pt and promoted the interaction between Pt and the carrier. The Pt-La/SAPO-11 catalyst was the best catalyst because of its high selectivity of C₈-C₁₆ alkanes and C₈-C₁₆ iso-alkanes.