Synthesis, Physicochemical Characterization, and Catalytic Evaluation of Fe3+-Containing SSZ-70 Zeolite

Whereas one-dimensional, 10-membered ring zeolites are typically used forhydroisomerization, Fe3+-containing SSZ-70 (Fe-SSZ-70) shows remarkable isomerizationselectivity for a zeolite containing 12- and partially blocked 14-membered rings, in addition to10-membered rings. Fe-SSZ-70 was compared to Al3+-containing SSZ-70 (Al-SSZ-70) inconstraint index andn-decane hydrocracking tests. Fe-SSZ-70 exhibited a 74% total isomeryield (64% yield of monobranched isomers and 10% cracking yield) at 85% conversioncompared to 49% total isomer yield (41% yield of monobranched isomers and 36% crackingyield) for Al-SSZ-70 at the same conversion. The selectivity to isomerization is attributed tothe weaker acid strength of Fe-SSZ-70 over Al-SSZ-70. Fe-SSZ-70 was directly synthesizedwith Fe3+isomorphously substituted in tetrahedral positions. The coordination environmentof the Fe3+was characterized using Mo??ssbauer, electron paramagnetic resonance, and diffusereflectance UV-vis spectroscopies. The physicochemical properties were further probed withinductively coupled plasma atomic emissionspectroscopy, temperature-programmeddesorption of isopropylamine, and nitrogen adsorption-desorption. The Fe3+was tetrahedrally coordinated in the as-madematerials and became partially octahedrally coordinated upon calcination; enough Fe3+remained in the framework after calcinationfor Fe-SSZ-70 to remain catalytically active.