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

Liu, Wenzhu, Xiao, Jiafu, Xu, Qiong, Liu, Xianxiang, Zhong, Sheng, Huang, Hua, Zheng, Min, Kirk, Steven Robert, Yin, Dulin
RSC advances 2018 v.9 no.1 pp. 185-191
Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, carbon, catalysts, catalytic activity, furfural, imidazoles, moieties, nitric acid, nitrogen content, oxidation, potassium hydroxide, titration
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.