Imidazolyl activated carbon refluxed with ethanediamine as reusable heterogeneous catalysts for Michael addition

Abstract

Imidazolyl activated carbon, denoted as AC-N, was prepared via oxidation of AC with HNO₃ (AC-O) and then refluxed with ethanediamine under mild conditions. The results showed that the N content of AC-N was 10.3%, and the surface alkali group density of AC-N was 0.96 mmol g⁻¹ from 0.78 mmol g⁻¹ carboxy group of AC-O by Boehm titration. It was revealed that the basic functional groups on the AC-N surface included imidazole and amine groups, from XPS and FT-IR. Evaluated with Michael addition of furfural, the catalytic performance of AC-N showed higher conversion and selectivity than that of commonly used base catalyst such as 2-methylimidazole and KOH. Very remarkably, AC-N showed extraordinary recyclability, in that there was no decline of conversion and selectivity after being recycled 5 times.