Na Ji,Alazar Alemayehu,Hanyang Li,Poknam Ri,Xinyong Diao
The production of phenol from lignin or its model compounds, instead of cumene oxidation is very interesting from the viewpoint of sustainability and economics. The selective demethylation of anisole was an efficient but challenging route to produce phenol. In this work, we demonstrated the fabrication of nickel sulfide (Ni 9 S 8 +Ni x S 6 ) nanoparticles on Al 2 O 3 matrix by a facile in situ sulfidation of NiAl hydrotalcite and announced that nickel sulfide can serve as efficient active site for the demethylation of anisole for the first time. The as-designed 4Ni1Al-S catalyst exhibited a hierarchical morphology with a high particle density and high dispersion, affording a 95.6% yield of phenol in the demethylation of anisole under relative milder reaction temperature (270 °C) when compared to the reported state-of-the-art results. By comprehensive characterizations and experiments, we inferred that the nickel sulfide exsolved from the LDH structure exhibited stronger metal-support interaction than that obtained from the impregnation method, which not only benefits the uniform dispersion of active nickel sulfide but also results in the electronic transfer from Ni center to Al 2 O 3 support. As a consequence, enhanced demethylation activity was achieved on 4Ni1Al-S in comparison to Ni-S/Al 2 O 3 -IM.
Phenol is one of the most important chemicals in industry. One-step selective benzene hydroxylation is an attractive yet challenging method for phenol production, especially when such a reaction can be driven by solar energy. Herein, we reported that a highly selective benzene hydroxylation to phenol can be achieved over two Fe-based metal–organic frameworks [MIL-100(Fe) and MIL-68(Fe)] under visible light irradiations using hydrogen peroxide (H2O2) as an oxidant. An optimal benzene conversion of 30.6% was achieved with a H2O2:benzene ratio of 3:4 over MIL-100(Fe) after 24 h irradiations. ESR results and the kinetic studies suggested that a successful coupling of the photocatalysis of Fe–O clusters in Fe-based metal–organic frameworks (MOFs) with a Fenton-like route is involved in this benzene hydroxylation process. The comparison of the reaction over MIL-100(Fe) and MIL-68(Fe) reveals that the structure of MOFs significantly influences the photocatalytic efficiency. Because the composition and the structure of MOFs are highly tunable, this study highlights the great potential of using Fe-based MOFs for photocatalytic benzene hydroxylation to form phenol, which may result in an economical, sustainable, and thus green process for phenol production.
Tao Chen,Dongxin Pan,Jie Zhu,Menglin Xie,Ting Li,Yu Zhou,Jun Wang
Direct benzene hydroxylation with dioxygen (O 2 ) is among the most promising alternative pathways for green phenol production, but efficient catalysis systems usually involve metal species or other additives such as sacrificial agents. In this work, we designed a carbon catalyst from the hydrothermal treatment of biomass-derived sucrose and constructed a metal-/additive free heterogeneous catalytic system for benzene hydroxylation to phenol with O 2 . The champion carbon sample gave a high phenol yield of 13.4%. The catalyst was facilely recovered and reused without apparent deactivation. There abundant oxygen functional groups such as phenolic and quinone carbonyl groups served as the active sites and polyfuran units accelerated the O 2 adsorption and activation. The synergistic effect of these surficial organic groups is conducive to the formation of reactive oxygen species, hydroxyl radicals, which effectively oxidized the benzene to phenol.
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