Yuzhou Wu,Xubin Zhang,Fumin Wang,Yi Zhai,Xianbao Cui,Guojun Lv,Tao Jiang,Jiaqi Hu
Direct hydroxylation of benzene to phenol is an effective and environment-friendly route to obtain phenol. Herein, Fe-doped and cupric acetylacetonate [Cu(acac)2]-grafted mesoporous silica (Cu/Fe-SBA-15) with highly dispersed metallic sites has been synthesized and used as a heterogeneous catalyst in the hydroxylation of benzene. The physiochemical properties of the synthesized materials as well as the reciprocity between iron and copper sites were analyzed by several characterization techniques including nitrogen adsorption–desorption, X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In direct hydroxylation of benzene with H2O2 as the oxidant, the prepared Cu/Fe-SBA-15 material showed great catalytic activity. Moreover, the synergistic effect between doped Fe sites and grafted Cu sites was also investigated. In this catalyst, Fe and Cu species both played the role of active sites. Excessive activity of iron would lead to benzene peroxidation, while the presence of copper sites could effectively hinder benzene peroxidation.
A heterogeneous catalyst (Cu/ZSM-5) was prepared by a metal-organic chemical vapor deposition (MOCVD) method under nitrogen atmosphere using Cu(acac) 2 as the copper precursor, and further characterized by XRD , AAS , SEM, BET, H 2 -TPR and XPS as well as catalytic activity performance for the oxidation of toluene. N 2 adsorption data revealed that the samples (CVD-4) prepared by MOCVD with calcination at 500 °C for 4 h possessed higher surface areas than that (CVD-BC) not calcined. The results of XPS demonstrated that CVD-4 exhibited higher redox property and more surface oxygen species compared with CVD-BC and IM (Cu/ZSM-5 catalyst prepared by impregnation). In particular, the CVD-4 catalysts prepared by MOCVD with calcinations showed the highest catalytic activity for toluene oxidation with 90% conversion of toluene at 293 °C with the feed concentration of 1000 ppm and GHSV of 15,000 h −1 , which was lower than IM (310 °C). The results of a reaction durability test revealed that the Cu/ZSM-5 catalysts prepared by MOCVD possessed excellent durability for toluene oxidation for 63 h, while the conversion of toluene fell down from 90% to 60% after 48 h over IM catalyst.
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