Direct hydroxylation of benzene to phenol using Fe containing MFI catalysts is still a hot spot due to the puzzle of activation C-H bond, industrial value of phenol, energy and environment-friendly one-pot method, cheap and recyclable catalysts. The activity of Fe-containing zeolite catalysts need to improve. According to our previous study, the OSDA and Na in the synthesis of Al-MFI influence the distribution of Al in the framework. Moreover, self-organization of extraframework Fe in zeolites is a general spectacle. In this work, based on the strategy of control the distribution of Al, Fe-site controlled MFI zeolites were synthesized, and the effect of Fe site location in MFI zeolites on the performance of hydroxylation of benzene to phenol with H2O2 was investigated. The Fe-MFI were synthesized by using only TPA and a mixture of TPA and Na. Thus obtain products were designated as FM(T) and FM(TN), respectively. Fe-ZSM-5 zeolites were also synthesized in a similar manner, FZ(T) and FZ(TN). The Si/Fe and Si/Al ratios in the catalysts were higher than those in the synthesis gel, and the gap of FM(T) and FZ(T) were more significant than FM(TN) and FZ(TN) because the former zeolites lacked the Na cations to balance the charge. The reaction of direct hydroxylation of benzene to phenol with H2O2 was carried out by using acetonitrile as solvent at 60 oC. The all catalysts attained similar high phenol selectivity (ca. over 90 %). The catalysts synthesized with only TPA (FM(T) and FZ (T)) showed higher phenol yield and H2O2 conversion than those with TPA and Na. These differences would be caused by the difference in the Fe state; for FM(T), Fe atoms were distributed at the intersection, while for FM(TN), Fe atoms were distributed at the intersection and channels. The UV-vis. and FT-IR results suggest that Fe atoms distributed at the intersection were more migrated to the extra framework by calcination, forming Fe clusters, than those in the channels. We considered that thus formed Fe clusters are active for this reaction.

Influence of Fe site location in Fe-MFI zeolite catalysts on the performance of hydroxylation of benzene to phenol with H2O2

255th National Meeting (2018)

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