Switchable transformation of biomass-derived furfural to furfuryl alcohol and isopropyl furfuryl ether over a zirconium-based bifunctional catalyst

Abstract

Selectively converting biomass-derived furfural (FF) to furfuryl alcohol (FFA) and isopropyl furfuryl ether (IPFE) via the same catalytic system is an important strategy for the production of high-value chemicals and fuels. However, this strategy still faces a great challenge because the formation of FFA and IPFE requires different catalyst types and reaction conditions. Hence, developing a compatible catalytic system is extremely necessary. In this work, we designed a high-efficiency zirconium-based bifunctional catalyst (Zr-HC-SO3H), simultaneously containing Lewis acid-base sites (Zr4+–O2−) and Brønsted acid sites (–SO3H), which were mainly responsible for the Meerwein-Ponndorf-Verley reduction reaction of FF and further etherification reaction of FFA, respectively. By controlling reaction conditions, the action orders and catalytic activities of Zr4+–O2− and –SO3H could be accurately regulated. Thus, Zr-HC-SO3H showed excellent catalytic performance for the switchable transformation of FF, leading to 98.9 % FFA yield at 120 °C for 4 h and 95.1 % IPFE yield at 170 °C for 12 h in isopropanol (iPrOH). Additionally, the analysis results of reaction pathways indicated that the etherification of FFA was much more difficult than the reduction of FF over Zr-HC-SO3H in iPrOH, so IPFE was only formed under the harsher reaction conditions. More significantly, Zr-HC-SO3H also catalyzed the switchable transformation of many other carbonyl compounds and demonstrated satisfactory catalytic universality in iPrOH. In conclusion, this work offered some momentous clues for the development of multipurpose catalytic systems and the controllable synthesis of valuable products in the biorefinery process.