N-Hydroxyphthalimide-Catalyzed Oxidative Production of Phthalic Acids from Xylenes Using O₂/HNO₃ in an Ionic Liquid

Abstract

A simple and mild process for oxidation of xylenes to phthalic acids using N-hydroxyphthalimide/O₂/HNO₃ in an ionic liquid, wherein the ionic liquid can be successfully recovered and reused, is described.

Keywords:

• N-Hydroxyphthalimide
• ionic liquid
• nitric acid
• oxidation
• phthalic acid

ACKNOWLEDGMENT

Financial support from the Petrochemical Research and Technology Company of Iran is gratefully acknowledged.

Notes

^a 2 mmol p-xylene, HNO₃, O₂, 1.48 g bmim[OMS], 110°C, 1 atm, 6 h.

^b GC conversion.

^c Isolated yield and selectivity by weight of terephthalic acid to p-xylene and product mixture.

^d 1 mL of EtOAc was added to the IL.

^e 1 mL CHCl₃ was added to the IL.

^f 3 mol% AIBN was used as initiator.

^g Tetramethylpyrrolidine N-oxide (TEMPO) was used as initiator.

^h NHPI was used as initiator. Recycling experiment for [bmim]OMS.

ⁱ NHPI was used as initiator.

^j H₂O₂ 30% was used as the oxidizing agent.

^a 40°C, 6 h.

^b 60°C, 4 h.

^c 110°C, 6 h.

^d T, terephthalic acid; I, isophthalic acid; P, phthalic acid.