Dataset Information

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 C_22-6-3·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 mmol_phenol g^-1. Calcination to remove the coke deposits completely restored the initial activity.

SUBMITTER: Meng L

PROVIDER: S-EPMC5389689 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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

Meng Lingqian L Zhu Xiaochun X Hensen Emiel J M EJM

ACS catalysis 20170310 4

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 Fe<sup>3+</sup> 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 N<sub>2</sub>O decomposition and benzene oxidation. The higher the Fe content, the higher the de ...[more]

PMID: 28413693

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Project description:Anaerobic benzene oxidation coupled to the reduction of Fe(III) was studied in Ferroglobus placidus in order to learn more about how such a stable molecule could be metabolized under strict anaerobic conditions. F. placidus conserved energy to support growth at 85°C in a medium with benzene provided as the sole electron donor and Fe(III) as the sole electron acceptor. The stoichiometry of benzene loss and Fe(III) reduction, as well as the conversion of [14C]-benzene to [14C]-carbon dioxide, was consistent with complete oxidation of benzene to carbon dioxide with electron transfer to Fe(III). Benzoate, but not phenol or toluene, accumulated at low levels during benzene metabolism and [14C]-benzoate was produced from [14C]-benzene. Analysis of gene transcript levels revealed increased expression of genes encoding enzymes for anaerobic benzoate degradation during growth on benzene versus growth on acetate, but genes involved in phenol degradation were not up-regulated during growth on benzene. A gene for a putative carboxylase that was more highly expressed in benzene- versus benzoate-grown cells was identified. These results suggest that benzene is carboxylated to benzoate and that phenol is not an important intermediate in the benzene metabolism of F. placidus. This is the first demonstration of a microorganism in pure culture that can grow on benzene under strict anaerobic conditions and for which there is strong evidence for degradation of benzene via clearly defined anaerobic metabolic pathways. Thus, F. placidus provides a much needed pure culture model for further studies on the anaerobic activation of benzene in microorganisms. A six-chip study using total RNA recovered from three separate cultures of Ferroglobus placidus DSM 10642 grown with 1 mM benzene (experimental condition) and three separate cultures of Ferroglobus placidus DSM 10642 grown on 0.5 mM phenol (control condition). Each chip measures the expression level of 2,613 genes from Ferroglobus placidus DSM 10642 with nine 45-60-mer probe pairs (PM/MM) per gene, with three-fold technical redundancy.

Project description:Anaerobic benzene oxidation coupled to the reduction of Fe(III) was studied in Ferroglobus placidus in order to learn more about how such a stable molecule could be metabolized under strict anaerobic conditions. F. placidus conserved energy to support growth at 85°C in a medium with benzene provided as the sole electron donor and Fe(III) as the sole electron acceptor. The stoichiometry of benzene loss and Fe(III) reduction, as well as the conversion of [14C]-benzene to [14C]-carbon dioxide, was consistent with complete oxidation of benzene to carbon dioxide with electron transfer to Fe(III). Benzoate, but not phenol or toluene, accumulated at low levels during benzene metabolism and [14C]-benzoate was produced from [14C]-benzene. Analysis of gene transcript levels revealed increased expression of genes encoding enzymes for anaerobic benzoate degradation during growth on benzene versus growth on acetate, but genes involved in phenol degradation were not up-regulated during growth on benzene. A gene for a putative carboxylase that was more highly expressed in benzene- versus benzoate-grown cells was identified. These results suggest that benzene is carboxylated to benzoate and that phenol is not an important intermediate in the benzene metabolism of F. placidus. This is the first demonstration of a microorganism in pure culture that can grow on benzene under strict anaerobic conditions and for which there is strong evidence for degradation of benzene via clearly defined anaerobic metabolic pathways. Thus, F. placidus provides a much needed pure culture model for further studies on the anaerobic activation of benzene in microorganisms. A five-chip study using total RNA recovered from three separate cultures of Ferroglobus placidus DSM 10642 grown with 0.5 mM phenol (experimental condition) and two separate cultures of Ferroglobus placidus DSM 10642 grown on 1 mM benzoate (control condition). Each chip measures the expression level of 2,613 genes from Ferroglobus placidus DSM 10642 with nine 45-60-mer probe pairs (PM/MM) per gene, with three-fold technical redundancy.

Dataset Information

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

Publications

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

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