2007 Fiscal Year Final Research Report Summary
Development of Catalysts for Selective Phenol Synthesis by Oxidation of Benzene in Gas Phase
| Project/Area Number |
18560740
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Catalyst/Resource chemical process
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| Research Institution | Kobe University |
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Principal Investigator |
KUMAGAI Norihisa Kobe University, Graduate School of Engineering Department fo Chemical Science and Engineering, Technician (60437457)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIYAMA Satoru Kobe University, Graduate School of Engineering Department fo Chemical Science and Engineering, Professor (00156126)
ICHIHASH Yuichi Kobe University, Graduate School of Engineering Department fo Chemical Science and Engineering, Assistant Professor (20362759)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Phenol / Benzene / Zeolite / Cupper / Difficult oxidation reaction / Coordination / Redox propert / Ti addition |
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| Research Abstract |
Direct phenol synthesis from benzene and molecular oxygen was investigated on Cu^<2+> ion-incorporated in ZSM-5 zeolite in gas phase. The calcinations at high temperatures improved the formation of phenol from benzene. Electron spin resonance spectra indicated that two type of Cu^<2+> ions were observed in HZSM-5 zeolites, one Cu^<2+> was bonded by oxygen with square pyramidal coordination, the other Cu^<2+> was bonded by oxygen with square planar coordination. The ratio between the pyramidal to the planar was changed by the calcinations temperature. The catalyst with the highest pyramidal Cu^<2+> indicated the highest yield of phenol. These results clearly indicate that the square pyramidal Cu^<2+> ions in HZSM-5 are active sites for direct oxidation of benzene in gas phase. Reduction behavior of Cu^<2+> ions in HZSM-5 was also studied by CO adsorption on the catalysts after evacuation at high temperatures. Carbon monoxide molecules are adsorbed not on Cu^<2+> and Cu^0 but on Cu. The
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catalyst with the highest pyramidal Cu^<2+> indicated that Cu^<2+> was readily reduced to Cu^+ by the evacuation. These results indicate that the pyramidal Cu^<2+> ions have high redox capacity. Benzene oxidation to phenol would proceed as follows;
1) Cu^<2+> is reduced to Cu^+ by a reducing agent (benzene, CO, etc.)
2) Cu^+ activates an oxygen molecule and produces specific oxygen species.
3) The specific oxygen species reacts with benzene and phenol is selectively formed. So, one of the important steps in the catalytic cycle of the oxidation is considered to be the reduction of Cu^<2+>. These considerations suggest that the square pyramidal Cu^<2+> sites have high redox capacity and form the specific oxygen species which produces phenol directly.
To control the redox property of the catalysts, addition of Ti and alkaline metals was investigated. The addition of Ti to Cu/HZSM-5 catalysts improved the activity of phenol formation. Electron spin resonance spectra and CO adsorption experiments indicated that the presence of Ti or alkaline metal neighboring Cu^<2+> ions would promote redox property. Less
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