4‐OH‐TEMPO radical grafted onto a novel polyaromatic ether sulfone containing carboxyl side chains as solid catalyst for alcohol oxidation

Abstract

Abstract2,2,6,6‐Tetramethylpiperidinium‐nitroxide (TEMPO) is a mild and efficient catalyst, which is important in the industrial production of selective oxidation of alcohols to the corresponding aldehyde or ketone compounds. However, it is a challenge to recover the expensive TEMPO catalyst in homogeneous catalytic systems. In this study, a novel polymer‐supported catalyst was prepared using 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxy (4‐OH‐TEMPO) and polyaromatic ether sulfone (PAES). The successful grafting of 4‐OH‐TEMPO in PAES‐C was demonstrated by 1H nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FT‐IR), load capacity can be calculated by elemental analysis (EA). BET and scanning electron microscopy (SEM) to depict the structure‐performance relationship. Herein, SEM images revealed the existence of porous structure. This structure can effectively adsorb NO molecules to form a PAES‐TEMPO/NOx catalytic system to selectively oxidize benzyl alcohol. The experimental results indicated the high activity, the subsequent benzyl alcohol oxidation cycle can reach more than 93% conversion without showing a large loss of selectivity. More importantly, the as‐prepared catalyst exhibited the attractive recyclability (recovery rate is 98%). After 10 consecutive runs, no significant loss of conversion and selectivity was observed (the conversion rate of benzyl alcohol was more than 93% and the selectivity was more than 95%). This study might provide some recommendation on the development of highly efficient catalysts for alcohol oxidation.