Synthesis, Characterization, and Catalytic Testing of Iron(III)-Containing SSZ-70

Real-feed hydrocracking tests using Al-SSZ-70 (International Zeolite Association three-letter framework code *-SVY) show evidence of overcracking of jet fuel to naphtha, which suggests that the acid sites are too strong. In contrast, the acid sites in B-SSZ-70 are too weak to be useful. Previous studies have shown that Brønsted acid site strength can be modified through isomorphic substitution into the tetrahedral positions according to Si < B < Fe < Ga < Al. As a result, Fe-SSZ-70 was prepared through a direct synthesis method. Characterization of the coordination environment of the iron(III) showed that it was tetrahedrally coordinated in the SSZ-70 framework in the as-made materials, but some iron(III) became octahedrally coordinated upon calcination. However, enough iron(III) remained in the framework to be catalytically active. Catalytic testing using n-decane as a model compound resulted in higher isomerization activity and less cracking for Fe-SSZ-70 over Al-SSZ-70 at comparable conversions. These results support previous work that showed that Fe does indeed have an intermediate acid site strength to that of Al and B.