Synthesis of ethyl levulinate over amino-sulfonated functional carbon materials

Functional carbon materials (FCM) containing amino and sulfonate groups (NS-FCM) were prepared with one-pot hydrothermal carbonization of cellulose using ammonium formate and 5-sulfosalicylic acid additives. The catalytic materials were applied to levulinic acid or furfuryl alcohol substrates in ethanol solvent for synthesizing ethyl levulinate (EL). Catalytic activity of NS-FCM was found to be related to its sulfonate groups, while substrate selectivity of NS-FCM was found to be related to its amino groups as supported by equilibrium adsorption and reaction experiments. Pre-adsorbed LA substrate onto NS-FCM followed by ethanol treatment at reaction conditions achieved EL yields higher than 90% that is attributed to a selective adsorption and cooperative desorption mechanism. The activity of NS-FCM catalyst was stable for five reuse cycles, but lost about 10% of its activity from the third cycle that is attributed to adsorption of humin precursors onto active sites. (C) 2020 Elsevier Ltd. All rights reserved.