Study On The Synthesis Reaction Of Biomass-based Monomer 2,5-furandicarboxylic Acid

With the increasing depletion of fossil raw materials,the development of bio-based chemicals based on biomass raw materials has become an inevitable trend.As a biomass platform molecule,5-Hydroxymethylfurfural(HMF)and its oxide 2,5-furandiformaldehyde(FDCA)are highly appreciated because of their excellent reactivity and can be converted into a variety of high-value-added chemicals.There are many ways to prepare FDCA,among which the HMF route is the most promising route to realize the industrial production of FDCA.This work mainly discusses the process of preparing FDCA from fructose via the HMF route,which is mainly divided into "two-step method" and "one-pot method" : the two-step method is mainly to oxidize the separated HMF to synthesize FDCA;the "one-pot method" is to directly oxidize the HMF stock solution obtained by dehydration of fructose to FDCA in situ without separation,and the entire reaction is "one-pot complete".For the "two-step method",the main difficulty in the reaction is that HMF is too polar and difficult to separate.The study have shown that fructose has a better dehydration effect in high-boiling solvents,but it makes the separation of strongly polar HMF very difficult,which restricts the large-scale production of FDCA.Therefore,the fundamental problem that needs to be solved is to design a low boiling point solvent system to achieve efficient synthesis of HMF.In this study,using a low-boiling acetone/water mixed system under the catalysis of hydrochloric acid catalyst,the highest yield of fructose dehydration to HMF can reach 93.1%.And the reaction conditions are mild,the dehydration temperature only needs to be 70-80°C,and the reaction time is shortened to within 30 minutes.At the same time,the mixed solvent can be removed by low-temperature vacuum distillation,which solves the problem of HMF separation while ensuring a high HMF yield.Then,the crude product of HMF produced by fructose dehydration was directly used for oxidative synthesis of FDCA,and the final yield was as high as 90.32%.For the "one-pot method",it is mainly based on the "one-pot two-step method" of a high-boiling solvent system.The main idea is to synthesize HMF by dehydrating fructose in a high-boiling solvent,and then directly oxidize the HMF solution to FDCA,avoiding the separation step of HMF.This not only takes advantage of the advantages of high boiling point solvents in fructose dehydration to synthesize HMF,but also avoids the problem that HMF is difficult to separate in high boiling point solvents.In this experiment,under microwave-assisted conditions,a strong polar,high boiling point organic solvent DMSO was used as the solvent to prepare HMF with a yield of 93.7%.At the same time,the oxidation activity of the cheap chlorine-containing tap water disinfectant chlorine dioxide effervescent tablets in the oxidation of HMF stock solution was discovered.The oxidation intermediates for preparing FDCA from HMF oxidation under this oxidation system are HMFCA and FFCA.It is worth mentioning that the HMF stock solution can be oxidized at 40°C for 50 min to obtain FDCA with a yield of 92%.