Production Of High Value-added Chemicals From Cellulose-based Carbohydrate

Sythesis of high value-added chemicals from biomass by using5-hydroxymethylfurfural?HMF?as a“bridge”molecule has recently attracted much attention.HMF can be obtained through cellulose hydrolysis,glucose isomerization and fructose dehydration in successive,and converted to various high value-added chemicals via different catalytic routes.2,5-diformylfuran?DFF?and2,5-furandicarboxylic acid which are obtained from HMF oxidation,have important applications in industry.Therefore,the preparation of HMF,DFF and FDCA from cellulose-based carbohydrates is of great importance.In this paper,several novel multifunctional catalysts were prepared for effective production of glucose,HMF,DFF and FDCA from cellulose-based carbohydrates,in order to solve some key scientific issues.The main contents are shown as follows:?1?Preparation of glucose from cellulose hydrolysis catalyzed by magnetic solid acid Fe₃O₄-RGO-SO₃H.Reduced graphene oxide functionalized with magnetic Fe₃O₄ nanoparticles and-PhSO₃H groups?Fe₃O₄-RGO-SO₃H?was prepared.Except for-PhSO₃H groups,-COOH and-OH groups derived from graphene oxide?GO?were also expected in the structure of Fe₃O₄-RGO-SO₃H.Fe₃O₄-RGO-SO₃H exhibited outstanding catalytic performance for the hydrolysis of cellulosic materials.On one hand,the-OH groups can absorb cellulose through forming strong hydrogen bonds between-OH groups and the oxygen atoms in?-1,4 glycosidic bonds.On the other hand,the–COOH and PhSO₃H groups provided a large amount of acid sites.Meanwhile,Fe₃O₄-RGO-SO₃H possessed high hydrothermal stability.Furthermore,Fe₃O₄-RGO-SO₃H can be easily separated from the reaction residue with an extra magnetic force and further used at least five times.?2?Preparation of HMF from fructose dehydration catalyzed by hydrophobic solid acid.Four functionalized silica nanoparticles with strong acidity and different hydrophobicity were synthesized.The hydrophobic groups in the silica nanoparticles can effectively isolate-SO₃H groups with water molecules in the reaction system,and thus the rehydration of HMF was avoided.Both the yield and selectivity of HMF increased with the hydrophobicity of the silica nanoparticles.By using the most hydrophobic solid acid(SiNP-SO₃H-C₁₆)as a catalyst,HMF yield can be up to 87%under the optimum reaction conditions.?3?Selective production of DFF and FDCA from fructose catalyzed by combination of Fe₃O₄-SBA-SO₃H and ZnFe_1.65Ru_0.35O₄.A novel magnetic spinel-type mixed oxide ZnFe_1.65Ru_0.35O₄ was prepared by a simple alkali-coprecipitation method.ZnFe_1.65Ru_0.35O₄ exhibited high catalytic activities for HMF oxidation to selective produce DFF and FDCA under different reaction conditions.Kinetic study indicated that DFF and FFCA were two mediate products in the process of HMF to FDCA,and the conversion of FFCA to FDCA was the rate-determining step.Mechanism analysis showed that the oxidation of HMF to DFF might proceed via a Ru-alkoxide intermediate,followed by?-hydride elimination.In the presence of water,DFF can be further converted to FFCA and finally FDCA,via oxidation of the-CHO group to the-COOH group.The-CHO group is believed to undergo rapid reversible hydration to a germinal diol,followed by the dehydrogenation of the germinal diol intermediate to produce the carboxylic acid.In addition,DFF or FDCA could be produced from fructose by sequentially using Fe₃O₄-RGO-SO₃H and ZnFe_1.65Ru_0.35O₄.?4?Preparation of DFF from fructose catalyzed by 3D flower-like Ce-Mo micro/nano composite oxides(f-Ce_10-xMo_xO_?).F-Ce_10-xMo_xO_?with different Ce/Mo molar ratio was prepared by an ethylene-glycol-mediate process.F-Ce_10-xMo_xO_?was a kind of micro/nano material which possessed 3D flower-like morphology,both acid and redox sites.F-Ce_10-xMo_xO_?was used as catalysts for fructose dehydration to HMF and HMF oxidation to DFF,the relationship between the catalytic activity with the structure and physico-chemical properties was investigated,and the reaction parameters were optimized to obtain the highest product yields.The results showed that f-Ce₉Mo₁O_?exhibited highest catalytic activity for fructose dehydration and HMF oxidation,due to its highest acid density,surface O_?ratio,specific surface area and polymeric octahedral MoO_z species.Futhermore,high DFF yield can be obtained from fructose catalyzed by f-Ce₉Mo₁O_?through a“one-pot,two step”method,and the highest DFF yield was up to 74%.