Acid-Metal Bifunctional Catalysis For Processing Xylose To Oxygenated Chemicals

Cellulose fuel ethanol will by-produce a large amount of hemicellulose.The multi-step conversion of hemicellulose to high-value oxygenated chemicals using furfural or its derivatives as reaction intermediates has some problems,such as long process route,high separation cost and low overall yield of the reaction.However,the coupling law of dehydration-hydrogenation reaction in the one-pot conversion system,the reaction mechanism of biomass and the design strategy of acid-metal bifunctional catalysts in the new reaction system are not clear enough.Based on this,this paper studies the system of catalytic conversion of xylose in one pot,using acid-metal bifunctional catalysts convert xylose to highvalue oxygenated chemicals.Studing the coupling law of dehydration-hydrogenation reaction,the conversion mechanism of xylose in dehydration-hydrogenation series reaction system and the design strategy of acid-metal bifunctional catalysts.The specific research contents,results and conclusions are as follows:1.Aiming at the problem of xylose priority hydrogenation to xylitol,the reaction system of one-pot conversion of xylose was optimized.Through the construction of cyclohexane-water two-phase system,introducing mass transfer resistance,increasing the apparent activation energy of xylose hydrogenation to xylitol,promoting the conversion of xylitol by dehydration,the selectivity of xylitol was reduced from 95.9%to 4.1%.The hydrogenation ability of the two-phase system was optimized by adding ypentanolactone,and the results of 31.4%selectivity for 2-pentanediol,34.8%selectivity for xylitol and 82.5%total carbon yield were obtained.The results show that the hydrogenation ability of the reaction in the dehydration-hydrogenation coupling system can significantly change the distribution of the products.2.The conversion of xylose to 1-2-pentanediol requires the synergistic effect of acid and hydrogenation catalyst.the hydrogenation catalyst mainly produces xylitol,and when the acid catalyst acts alone,xylose is converted to furfural.Through deuteration experiments,it was verified that furfural and its hydrogenation derivatives were not the reaction precursors of 1-2-pentanediol in acid-metal bifunctional catalytic system.The possible reaction mechanism for the conversion of xylose to 1-2pentanediol by acyclic route in dehydration-hydrogenation series reaction system was proposed.3.Based on the above reaction mechanism and reaction network,investigating the product distribution of xylose conversion by changing the number and combination of active sites of acid-metal bifunctional catalysts.The main product in the reaction system was transformed from 1-2-pentanediol to cyclopentyl alcohol and acetone alcohol.The results show that the construction mode of acid-metal bifunctional catalyst can significantly affect the product selectivity of xylose conversion.