Synthesis of a sustainable and robust heterogeneous TEMPO catalyst utilizing activated carbon for aerobic alcohol oxidation

Abstract

The selective oxidation of alcohols is a crucial process in organic chemistry, but current methodologies have limitations such as pollution and over-oxidation. The use of 2,2,6,6-tetramethylpiperidine oxide (TEMPO) as a catalyst offers a promising approach for selective aerobic alcohol oxidation. However, the high cost of TEMPO and difficulty in catalyst recycling hinder its industrial application. This study focuses on developing a sustainable and robust heterogeneous TEMPO catalyst by immobilizing TEMPO on activated carbon (AC) through ozonation and reductive amination. The surface modification of AC through ozone carbonylation is explored, and a green and safe process is established using water as a dispersing and heat-shifting medium. The TEMPO-functionalized AC as a heterogeneous catalyst is characterized using various analytical techniques, and its catalytic performance is evaluated for continuous aerobic alcohol oxidation in a micro-packed bed reactor. The results demonstrate an extended catalyst lifetime (turnover number reaches 1465.0 for benzyl alcohol oxidation) and significant potential for industrial applications.