Stable Fe/ZSM-5 Nanosheet Zeolite Catalysts for the Oxidation of Benzene to Phenol

Abstract

Fe/ZSM-5 nanosheet zeolites of varying thickness were synthesized with di- and tetraquaternary ammonium structure directing agents and extensively characterized for their textural, structural, and catalytic properties. Introduction of Fe3+ ions in the framework of nanosheet zeolites was slightly less effective than in bulk ZSM-5 zeolite. Steaming was necessary to activate all catalysts for N2O decomposition and benzene oxidation. The higher the Fe content, the higher the degree of Fe aggregation was after catalyst activation. The degree of Fe aggregation was lower when the crystal domain size of the zeolite or the Fe content was decreased. These two parameters had a substantial influence on the catalytic performance. Decreasing the number of Fe sites along the b-direction strongly suppressed secondary reactions of phenol and, accordingly, catalyst deactivation. This together with the absence of diffusional limitations in nanosheet zeolites explains the much higher phenol productivity obtainable with nanostructured Fe/ZSM-5. Steamed Fe/ZSM-5 zeolite nanosheet synthesized using C22-6-3·Br2 (domain size in b-direction ∼3 nm) and containing 0.24 wt % Fe exhibited the highest catalytic performance. During the first 24 h on stream, this catalyst produced 185 mmolphenol g–1. Calcination to remove the coke deposits completely restored the initial activity.

The ZSM-5-Catalyzed Oxidation of Benzene to Phenol with N2O: Effect of Lewis Acid Sites

“…And H-ZSM-5-ST seems to have a higher yield than that of Fe-ZSM-5-ST after 3 h reaction time. Probably because catalysts containing Fe deactivated more severely and rapidly [47]. In addition, it is seen that the initial selectivity toward phenol has a certain relationship with the acid properties when combines the data from Figure 6, Figure 7, and Table 4.…”

Organic–inorganic hybrid of anchored dicationic ionic liquid on Al‐MCM‐41‐phosphovanadomolybdate toward selective oxidation of benzene to phenol

“…However, phenol is more activate than the substrate and can undergo over‐oxidation to producing the byproducts . Among the current oxidants and especially compared to O 2 as an eco‐friendly oxidant that needs a high temperature for its activation and N 2 O with limited source, H 2 O 2 is a promising choice because of easy handling and producing water as the only byproduct . In the last decades, various catalysts based on noble and transition metals including Pd, Pt, Fe, Cu, Cr, and V were used for direct oxidation of benzene to phenol which vanadium based catalysts due to the intrinsic tendency of vanadium for oxidation of hydrocarbons have shown to be useful and promising catalysts …”

Hard meso/macroporous iron oxide/iron silicate macrospheres obtained by the multi‐templating technique

“…The incorporation/doping of heteroatoms into the open silica framework has received considerable attention because of the need to develop more efficient and more stable materials for applications in catalysis, separation, coating and other fields . In particular, iron‐containing silica materials are remarkable heterogeneous catalysts for various reactions such as oxidation, acylation, alkylation, reduction, Fischer–Tropsch synthesis, polymerization, dehydrogenation and hydroformylation …”

“…[4][5][6][7][8][9] In particular, iron-containing silica materials are remarkable heterogeneous catalysts for various reactions such as oxidation, acylation, alkylation, reduction, Fischer-Tropsch synthesis, polymerization, dehydrogenation and hydroformylation. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] The main limitation of the hierarchical porous materials synthesized via the techniques reported to date in the scientific literature is that they are obtained usually in the form of a powder or as a film, making it difficult to separate and therefore to reuse them.…”