The synergic effects of highly selective bimetallic Pt-Pd/SAPO-41 catalysts for the n-hexadecane hydroisomerization

The hydroisomerization of n-hexadecane over Pt-Pd bimetallic catalysts is an effective way to produce clean fuel oil. This work reports a useful preparation method of bimetallic bifunctional catalysts by a co-impregnation or sequential impregnation process. Furthermore, monometallic catalysts with loading either Pt or Pd are also prepared for comparison. The effects of the metal species and impregnation order on the characteristics and catalytic performance of the catalysts are investigated. The catalytic test results indicate that the maximum iso-hexadecane yield over different catalysts increases as follows: Pt/silicoaluminophosphate SAPO-41 < Pd/SAPO-41 < Pt*-Pd/SAPO-41 (prepared by sequential impregnation) < Pt-Pd/SAPO-41 (prepared by co-impregnation). Owing to the synergic effects between Pt and Pd, the Pt-Pd/SAPO-41 catalyst prepared by the co-impregnation method demonstrates the effective promotion of (de)hydrogenation activity. Therefore, this catalyst exhibits the highest iso-hexadecane yield of 89.4% when the n-hexadecane conversion is 96.3%. Additionally, the Pt-Pd/SAPO-41 catalyst also presents the highest catalytic activity and best stability even after 150 h long-term tests.