Strong wave-absorbing catalyst cooperates with microwave energy to enhance fructose dehydration to produce 5-hydroxymethylfurfural
Multihole hollow carbon spheres(MHCS)were prepared by using a hard template method.The effects of heat treatment temperature,metal loading,and etching on the electromagnetic parameters of MHCS were systematically studied.Among the prepared carbon spheres,MHCS-800 with high dielectric loss(ε″=213)was selected as the support for catalysts,while SCS-800(ε″=50)and SCS(ε″=0.08)served as control groups.These carbons after sulfonation were used to catalyze the hydrolysis of fructose.Based on the reaction kinetics under microwave(MW)and conventional heating conditions,the influence of dielectric loss on the MW-assisted catalytic effect was investigated.The results showed that the conversion rate can reach 97.7%within 5 min using MHCS-800-SO3H as catalysts under 80 W MW power irradiation.Besides,the reaction rate constant(k)under MW is 0.76 min-1,which is 8.97 times of that under conventional heating(k=0.0847 min-1).The MW enhancement effect occurred in MHCS-800-SO3H is much more significant compared with SCS-800-SO3H and SCS-SO3H(where k values were increased by 164.9%and 11.9%,respectively).The above results can be attributed to the combination of the hollow porous structure and the high graphitization degree of MHCS-800,which is conducive to the formation of"hotspots"on the surface of catalyst particles,thereby accelerating catalytic reactions.
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