Application Of Fenton And Microreactor In The Conversion From Carbohydrate To 5-Hydroxymethylfurfural

To get 5-hydroxymethylfurfural(5-HMF),an important chemical platform compound,two new ways were studied conversion from carbohydrate to 5-HMF via the Fenton reaction and conversion from glucose to 5-HMF via a microreactor modified with Cr2O3 nanostructures.In the conversion of starch,glucose and fructose to 5-HMF via Fenton,we investigated the influences including temperature,reaction time,the ratio of water to butanol,and the ratio of Fenton(Fe2+ and H2O2).It was found that 5-HMF yield first increased and then decresed.Because higher temperature contributed to both formation and decomposition of 5-HMF,increase of temperature helped to improve the yield of 5-HMF in a short time but conversely for a long time.Similarly 5-HMF yield first increased and then decresed with the increase of total water in water-butanol two-phase system or Fe2+ contents of Fenton.Finally,we obtained the optimal reaction conditions.For starch and glucose,the highest yields 46.5% and 47.4% could be reached when the mole ratio of water and n-butanol was 1:1;the ratio of Fe2+ to H2O2 was 1:50;the reaction temperature was 150 ? in 90 min.For fructose,the highest yield 61.7% could be reached when the mole ratio of water to n-butanol was 1:3;the ratio of Fe2+ to H2O2 was 1:50;the reaction temperature was 150 ? in 180 min.At the same time,we found that Fenton could also catalyze sucrose and cellulose to 5-HMF.The yields were not high,21.9% and 10.2%,but it offered new ideas for the conversion of biopolymers and biological raw materials to 5-HMF.Then the mechanism of the Fenton reaction was discussed that Fenton can degrade starch to glucose,catalyze glucose to fructose and convert fructose to 5-HMF.In the conversion from glucose to 5-hydroxymethylfurfural via a microreactor modified with Cr2O3 nanostructures,the process to make the new type of microreactor was introduced in detail.The speed of injection of the sample and the concentration of reactants were discussed as influence factors.It was found that the more quickly we injected,the lower conversion,yield and selectivity we obtained.The best result was obtained with 68.7% yield and 75.4% selectivity at 91.1% fructose conversion when 0.5g glucose involoed in the reaction and the speed of injection was 16.67 ?L·min-1.The yield and selectivity were both higher than those of tank reactor.Under the same conditions,the less glucose we added,the higher selectivity and yield we got.The 5-HMF yield from fructose via the same microreactor was 85.6%,which was much higher than that via a tank reactor with Cr3+ or sulfuric acid as catalyst.The reaction rate of preparing 5-HMF via the microreactor was very quick and we could collect the product in 9.8s.After a long time reaction,the micoreactor efficiency would be decreased,but the 5-HMF yield was still above 50% after 16 hours.