Rapid Formation and Facile Separation of Biofuel 5-EMF over Integration of Sustainable Catalyst with Oxygen Environment under an Ultrasonic-Assisted Ethanolysis System

Abstract

In this work, ultrasonic-assisted ethanolysis of raw sugar (RS) into 5-ethoxymethylfurfural (5-EMF) product was performed under a biphasic system under mild conditions. The sulfonic-magnetic activated carbon (S-MAC) was prepared via pyrolysis and sulfonation processes and further applied for catalytic production of 5-EMF. The catalytic behaviors for facile formation/rapid production of 5-EMF were described through several factors such as type of catalyst, S-MAC and choline chloride (ChCl) adding amounts, reaction temperature, reaction time, and ultrasonic power generation. The integrating roles of various catalysts with the introduction of oxygen were described using turnover rate investigation, and the result found to be a great effect for improving the 5-EMF yield via major reactions such as hydrolysis, isomerization, dehydration, and etherification while side reactions for formation of polymeric intermediates were remarkably suppressed. Herein, a maximum yield of 5-EMF (actual yield = 93.2 ± 0.6%) was obtained at a low temperature of 80 °C and short reaction time for 11 min under an optimization process via linear-quadratic designs. Finally, the reusable systems under O2 and N2 addition were compared up to 10 cycles, and the result found that very few changing in 5-EMF yield could be obtained while hard carbon/humins deposited on S-MAC structure was significantly obstructed and reduced in each cycle via special oxidative degradation. In addition, lower energy consumption was required for regeneration of spent catalyst derived from reaction under an oxygen environment. This work was notably expected for further application in practical procedure under a reusable system.