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

To reduce overcracking from aluminum in SSZ-70 (Al-SSZ-70), iron(III)-containing SSZ-70 (Fe-SSZ-70) was directly synthesized with iron(III) isomorphously substituted in tetrahedral positions. The coordination environment of the iron(III) was characterized using Mössbauer, Electron Paramagnetic Resonance, and Diffuse Reflectance UV-Vis spectroscopies. The physicochemical properties were further probed with inductively coupled plasma atomic emission spectroscopy, NH₃ temperature-programmed desorption, and nitrogen adsorption-desorption. The iron(III) was tetrahedrally coordinated in the as-made materials and became partially octahedrally coordinated upon calcination; enough iron(III) remained in the framework after calcination for Fe-SSZ-70 to remain catalytically active. Fe-SSZ-70 was compared to Al-SSZ-70 in constraint index and n-decane hydrocracking tests. Fe-SSZ-70 exhibited 74% total isomer yield at 85% conversion (86% of the isomers were mono-branched) compared to 49% total isomer yield for Al-SSZ-70 at the same conversion. While medium-pore zeolites are typically used for hydroisomerization, Fe-SSZ-70 shows remarkable isomerization selectivity for a zeolite containing 12 and partially-blocked 14 membered rings, in addition to 10 membered rings.