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

Abstract

Whereas one-dimensional, 10-membered ring zeolites are typically used for hydroisomerization, Fe3+-containing SSZ-70 (Fe-SSZ-70) shows remarkable isomerization selectivity for a zeolite containing 12- and partially blocked 14-membered rings, in addition to 10-membered rings. Fe-SSZ-70 was compared to Al3+-containing SSZ-70 (Al-SSZ-70) in constraint index and n-decane hydrocracking tests. Fe-SSZ-70 exhibited a 74% total isomer yield (64% yield of monobranched isomers and 10% cracking yield) at 85% conversion compared to 49% total isomer yield (41% yield of monobranched isomers and 36% cracking yield) for Al-SSZ-70 at the same conversion. The selectivity to isomerization is attributed to the weaker acid strength of Fe-SSZ-70 over Al-SSZ-70. Fe-SSZ-70 was directly synthesized with Fe3+ isomorphously substituted in tetrahedral positions. The coordination environment of the Fe3+ 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, temperature-programmed desorption of isopropylamine, and nitrogen adsorption–desorption. The Fe3+ was tetrahedrally coordinated in the as-made materials and became partially octahedrally coordinated upon calcination; enough Fe3+ remained in the framework after calcination for Fe-SSZ-70 to remain catalytically active.

One-Pot Synthesized Fe-AEI Zeolite Catalysts Contribute to Direct Oxidation of Methane

“…The coordination state and extent of aggregation of Fe species in as-synthesized, calcined, and H-type Fe-AEI zeolites were investigated by UV–vis spectroscopy (Figure a–c). The spectra of as-synthesized zeolites were dominated by two characteristic oxygen-to-metal charge-transfer bands around 212 and 240 nm, which were related to tetrahedral Fe 3+ species in the framework (Figure a). , Thus, we concluded that Fe 3+ was predominantly built into the zeolite framework by the isomorphous substitution of Si 4+ by Fe 3+ . Compared to the as-synthesized zeolites, the band at 240 nm shifted to 270 nm for the calcined samples, which is typical for octahedral Fe species (Figure b) .…”

Structure Features and Physicochemical Performances of Fe-Contained Clinoptilolites Obtained via the Aqueous Exchange of the Balanced Cations and Isomorphs Substitution of the Heulandite Skeletons for Electrocatalytic Activity of Oxygen Evolution Reaction and Adsorptive Performance of CO2

“…As can be seen in Figure 1 Be,f, Fe(0.03) −H(0.05) −9−CP and Fe(0.06) −H(0.07) −9−CP showed essentially two absorption bands located at ca. 210 and 272 nm, which were assigned to electronic transitions of the anion (e.g., O 2− ), that is, t 2g and e g orbitals of Fe 3+ within [FeO 4 ] − tetrahedra [ 9 , 28 ]. Obviously, these observations were associated with ligand to metal charge-transfer characteristics that involved the isolated four-coordinated and octahedral coordinated mononuclear Fe 3+ [ 9 ].…”

“…Figure 5 shows the EPR spectra acquired at 77 K for Fe-substituted CPs. As can be seen, all samples presented two signals: a sharp signal at g = 4.3 assignable to tetrahedral Fe 3+ [ 28 ], and a broad signal at g = 2.0 assignable to octahedrally coordinated Fe 3+ in the non-framework positions. Their deformation was the same as profiles reported by Bordiga et al [ 45 ].…”

“…As can be observed, the isosteric heats of CO 2 adsorption on CP, Fe(0.03)−H(0.05)−CP−3, Fe(0.03)−H(0.05)−CP−9, and Fe(0.03)−H(0.00)−CP−9 were less than zero, indicating that the CO 2 adsorption was an exothermic process [ 75 ]. Meanwhile, the calculated isosteric heat of adsorption was commonly less than 40 kJ·mol −1 , meaning that physical adsorption dominates the CO 2 adsorption behaviors on all CPs [ 28 ].…”

Use of Nickel Oxide Catalysts (Bunsenites) for In-Situ Hydrothermal Upgrading Process of Heavy Oil

“…This allows an additional decrease in viscosity that could lead to a greater increase in the recovery factor. Studies have been reported on different metal-based catalysts (Fe, Co, Ni) [16][17][18]; however, it has been shown that Ni is the most active catalyst for the hydrocracking and hydrogenation of heavy components, while inhibiting condensation and recombination reactions, as demonstrated by Muneer et al in their study [2]. Several studies of hydrothermal upgrading of heavy oil using different catalysts have been performed [19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”