Research On Microwave Enhanced Catalytic Degradation Of Cellulose

This paper was based on Microwave enhanced Fenton\classes-Fenton reagents and Microwave-ZnCl₂ method to degrade cellulose.Five kinds of Fenton\class Fenton reagents were used as the oxidants to research the effect of different reaction on cellulose depolymerization. And it was found that the ability of cellulose depolymerization is: Microwave-class Fenton > Microwave-Fenton > bathing - Fenton > Microwave - heating > water bathing. We focused on the effect of Cr (â…¥)– class - Fenton reagent as the catalyst in depolymerization of cellulose. The reaction conditions of pH value, reaction temperature, reaction time, Cr (â…¥) solution amount, H₂O₂ concentration and microwave power were studied for the cellulose depolymerization. When the optimally experimental conditions were established as microwave power 400W, pH value 4, the volume ratio of 0.1 mol/L Cr (â…¥) solution and the H₂O₂ to 4:0.7, reaction temperature 90℃and reaction time of 40 min., the average degrees of polymerization of cellulose decreased from1200 to 235, the depolymerization ratio was 80%, and there was no new functional groups generated in cellulose after the depolymerization by FTIR analysis.The microwave heating method was used to degrade cellulose as ZnCl₂ used as solvent and catalyst. The 5-hydroxymethyl furfural (5-HMF) and 1-(furan-2-yl)-2-hydroxyethanone were separated from degradation products by extraction and characterized using FT-IR, ¹H NMR, ¹³C NMR, and GC-MS spectra respectively. The effects of reaction temperature, time, ZnCl₂ concentration, cellulose content, microwave power, heating methods and reagents on the molar yields of products were studied. It was found that in the 140 ml 69% ZnCl₂ solution for consisting of cellulose amount of 1 g , the molar yields of 5-HMF reached to 19.4% under the microwave power of 500 W and 1-(furan-2-yl)-2-hydroxyethanone reached to 12.0% under the microwave power of 600 W when the reaction temperature was 135℃and reaction time reached 5 min. Microwave heating not only affects the production of 1-(furan-2-yl) -2- hydroxyethanone, but also increased molar yields of 5-HMF compared with ordinary oil bath heating method.