Efficient Cellobiose Hydrolysis over a Sulfonated Carbon Catalyst in a Spatially Separated Microwave Electric- and Magnetic-Field Flow Reactor

Enhanced polysaccharide hydrolysis is essential for converting polysaccharides into mono- and oligosaccharide sugars for use in food, pharmaceutical, and biobased chemical applications. In this study, we developed an efficient continuous-flow hydrolysis process by applying microwaves and sulfonated carbon catalyst (AC-SO3H) using cellobiose as a model sugar substrate. We built a microwave flow reactor equipped with a rectangular waveguide and a solid-state microwave generator capable of applying microwaves to a fixed catalyst bed with spatially separated electric (E-) and magnetic (H-) fields and showed that the microwave flow reaction under the E-field improves the glucose formation rate up to 21.7 mmol/g per hour, which is 35.3 times higher than that achieved in the batch microwave reactor. AC-SO3H showed 16-30 times higher activity than Amberlyst 70 because of the higher dielectric loss tangent (tan delta) value of AC-SO3H (0.187) than Amberlyst 70 (0.040). H-field heating of AC-SO3H also improved the glucose formation rate by 1.2-1.6 times. Notably, the H-field reduced the microwave power to 45% of that of the E-field. Therefore, a microwave H-field flow reactor equipped with an AC-SO3H catalyst greatly improves both the glucose production rate and energy efficiency of cellobiose hydrolysis.