Aerobic oxidation of alkyl chain in alkylphenols over combination of Pt and Pd catalysts

Yoshinao Nakagawa, Kensuke Tokuma, Yosuke Nakaji, Akari Miyagawa, Masazumi Tamura, Keiichi Tomishige

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)149-156
Number of pages8
JournalApplied Catalysis A: General
Volume569
DOIs
Publication statusPublished - 2019 Jan 5

Keywords

  • Aerobic oxidation
  • Cresol
  • Palladium
  • Platinum

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

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