Catalytic Conversion Of 5-Hydroxymethylfurfural And Furfural To Produce High-value Chemicals

Global economic growth is driving a sharp increase in demand for fuels and chemicals.To achieve sustainable production of fuels and chemicals,modern societies need to develop economical and energy-efficient processes.In addition,the depletion of fossil energy,high oil prices,energy security and environmental pollution also promote the human need to find carbon neutral,green and renewable new energy.Biomass is an abundant,sustainable and cost-effective source of organic chemicals and liquid biofuels.Furfural（FUR）and 5-hydroxymethylfurfural（HMF）are considered to be the bridge between biomass and biomass fuels and chemicals.Therefore,it is of great significance to design and develop new efficient catalysts and methods using biomass platform compounds HMF and FUR as raw materials.This can not only solve various problems caused by dependence on fossil energy,but also producing high value-added fine chemicals from low-value biomass based platform compounds.This paper focuses on the development of new methods,new paths,catalyst preparation and catalytic mechanism for the high-value utilization of biological based chemicals HMF and FUR.The main research contents are as follows:（1）Iodide assisted radical induced disproportionation of 5-hydroxymethylfurfural under acidic conditions.In the absence of additional reducing agents and oxidants,disproportionation of alcohols produces both alkanes and aldehydes/ketones.However,the reported methods are limited,and the range of substrates is narrow or the reaction conditions are harsh.Herein,we report that alcohol disproportionation can proceed with high efficiency catalyzed by iodide under acidic conditions.This method exhibits high functional group tolerance including aryl alcohol derivatives with both electron-withdrawing and electron-donating groups,furan ring alcohol derivatives,allyl alcohol derivatives,and dihydric alcohols.Under the optimized reaction conditions,a 49%yield of 5-methylfurfural and a 49%yield of 2,5-diformylfuran were obtained simultaneously from 5-hydroxymethylfurfural.An mechanistic study suggested that the hydrogen transfer during this redox disproportionation occurred through the inter-transformation of HI and I₂.EPR and free radical trapping experiments proved that the disproportionation reaction was driven by the radicals generated in the original site of the reaction.（2）The direct conversion of furfural（FUR）to 2-methyltetrahydrofuran（2-MTHF）over a trimetallic CuNi Re/Hβcatalyst has been studied.Under optimal reaction conditions at 240℃under 3 MPa H₂ for 1 h,almost complete conversion of FUR and high-yield of 2-MTHF（81%）was achieved.This is the highest yield reported for the direct conversion of FUR to 2-MTHF.HR-TEM demonstrated that the growth of Cunanoparticles（NPs）on the surface of Hβwas inhibited after loading Ni or Re resulted in the smaller Cuparticle size and better hydrogenation and hydrodeoxygenation activity.H₂-TPR characterization exhibited that the reducibility of bimetallic and trimetallic catalysts was higher than that of monometallic catalysts.NH₃-TPD explained that Hβacid sites mainly contributed to FUR deoxygenation.The adsorption configurations of FUR,furfuryl alcohol（FOL）and 2-methylfuran（2-MF）on the catalyst were revealed by ATR-IR.Catalyst evaluation and control experiments proved that FUR was first hydrogenated to FOL,followed by hydrodeoxygenation to 2-MF,and finally hydrogenated to 2-MTHF catalyzed by the combination of three metals.（3）Without additive,Ru/Zr（OH）₄ catalyzes the conversion of furfural to furfuryl alcohol by hydrogen transfer reaction.Ru/Zr（OH）₄ was developed as an effective transfer hydrogenation catalyst for a broad substrate scope,including nitro,alkene,and aldehyde/ketones groups without additives.XPS study and catalyst evaluation indicated that Ru⁰ was the main active catalytic species during the reaction.FT-IR and CO₂-TPD analysis showed that Zr（OH）₄ has abundant basic sites.The synergistic effect of Ru metal and basic sites of Zr（OH）₄ support provides Ru/Zr（OH）₄ with good catalytic activity without additional base addition.Ru-Hactive species was detected by1H solid-state NMR,and the mechanism of nitrobenzene transfer hydrogenation was proposed.Ru/Zr（OH）₄ catalyst was stable and can be reused for at least 5 cycles with only slight loss of activity and selectivity.It also has good activity to furfural.Ru/Zr（OH）₄ catalyzes the hydrogen transfer of furfural to obtain furfuryl alcohol with95%yield.We believe this methodology provides an environmentally benign process for transfer hydrogenation under additives-free conditions with the advantages of high activity,stability,and broad substrate scope.（4）Preparation ofγ-butyrolactone from furfural derivatives photocatalyzed by Ru/Ti O₂ under mild conditions.The high efficiency cracking of C-C bond catalyzed by oxygen is an important method for producing oxygen-containing fine chemicals from biomass.Here,we report the photocatalytic oxidation of furfural derivative tetrahydrofurfuryl alcohol（THFAL）to prepareγ-butylactone（GBL）under the light irradiation of air at normal temperature and pressure.Ru/Ti O₂ was used as photocatalyst and air as oxidant.The effects of different metal loads,light sources and reaction time on the photocatalytic oxidation of THFAL to GBL were investigated.In addition,strict controlled experiments and material characterization,free radical quenching,EPR detection experiments to illustrate the possible reaction mechanism.The formation of alkoxy intermediates is essential for the cleavage of C-C bonds,and superoxide radical anions have been shown to be reactive oxygen species for this reaction.In this project,we expanded the photocatalytic conversion path of biomass resources and realized the photocatalytic synthesis of GBL by biomass based furfural derivative THFAL under mild conditions.