TY - JOUR
T1 - Aerobic oxidation of alkyl chain in alkylphenols over combination of Pt and Pd catalysts
AU - Nakagawa, Yoshinao
AU - Tokuma, Kensuke
AU - Nakaji, Yosuke
AU - Miyagawa, Akari
AU - Tamura, Masazumi
AU - Tomishige, Keiichi
N1 - Funding Information:
Part of this work is supported by JSPS KAKENHI “Grant-in-Aid for Scientific Research (C) ” K15K065640 . We thank the Technical Division of School of Engineering, Tohoku University for the ICP and TEM-EDX measurements.
Publisher Copyright:
© 2018 Elsevier B.V.
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
PY - 2019/1/5
Y1 - 2019/1/5
N2 - Oxidation of benzylic position in alkylphenols with molecular oxygen in acidic conditions, which is very difficult because of the intense dimerization or polymerization, was investigated with various combinations of noble metal catalysts. The combination of Pt/C and Pd(CH3COO)2 catalysts showed activity in the formation of p-hydroxybenzaldehyde formation from p-cresol. The best p-hydroxybenzaldehyde yield was 35%, which was obtained in 50 wt% aqueous acetic acid, Pt on carbon : Pd(CH3COO)2 weight ratio = 1 : 2, at 353 K. From XRD, TEM-EDX and XAFS characterizations, the Pt and Pd species were totally reduced to Pt and Pd metal particles, respectively, in spite of the oxidative reaction conditions. Polymerized products (“tar”) of p-cresol formed with Pt/C catalyst and air can be the reductants for Pd(CH3COO)2 into Pd metal. The catalysts or catalyst combinations without Pd metal showed no activity in the formation of p-hydroxybenzaldehyde, suggesting that Pd° is the active species. The effects of the air pressure and presence of radical scavenger were very small, suggesting that non-free-radical mechanism was involved.
AB - Oxidation of benzylic position in alkylphenols with molecular oxygen in acidic conditions, which is very difficult because of the intense dimerization or polymerization, was investigated with various combinations of noble metal catalysts. The combination of Pt/C and Pd(CH3COO)2 catalysts showed activity in the formation of p-hydroxybenzaldehyde formation from p-cresol. The best p-hydroxybenzaldehyde yield was 35%, which was obtained in 50 wt% aqueous acetic acid, Pt on carbon : Pd(CH3COO)2 weight ratio = 1 : 2, at 353 K. From XRD, TEM-EDX and XAFS characterizations, the Pt and Pd species were totally reduced to Pt and Pd metal particles, respectively, in spite of the oxidative reaction conditions. Polymerized products (“tar”) of p-cresol formed with Pt/C catalyst and air can be the reductants for Pd(CH3COO)2 into Pd metal. The catalysts or catalyst combinations without Pd metal showed no activity in the formation of p-hydroxybenzaldehyde, suggesting that Pd° is the active species. The effects of the air pressure and presence of radical scavenger were very small, suggesting that non-free-radical mechanism was involved.
KW - Aerobic oxidation
KW - Cresol
KW - Palladium
KW - Platinum
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U2 - 10.1016/j.apcata.2018.10.024
DO - 10.1016/j.apcata.2018.10.024
M3 - Article
AN - SCOPUS:85055888980
SN - 0926-860X
VL - 569
SP - 149
EP - 156
JO - Applied Catalysis A: General
JF - Applied Catalysis A: General
ER -