Catalytic Conversion Of Carbohydrate Preparation Platform Compounds

Owing to diminishing fossil fuel reserves and growing concerns about global warming,sustainable sources of energy are needed in the near future,and establishing a renewable chemical industry featuring renewable resources as the dominant feedstock rather than fossil resources is very important for the future.5-HMF is considered to be the key intermediate to bridge the gap between biomass resources and fossil fuel resources,which is can be upgraded to liquid fuel via hydrogenation or etherification.The catalytic conversion of cellulose,glucose and fructose has been comprehensively studied,however,the low 5-HMF yield form cellulose and the high cost of fructose limit their further applications.Sucrose is an inexpensive chemical,and compared to cellulose,its bond is much more easily hydrolyzed and it produces higher 5-HMF yields.Although high yields of 5-HMF have been achieved with fructose,chemical and/or biochemical transformations that convert sucrose to highly valuable synthetic intermediates such as 5-HMF,is more commercially feasible.In addition,chitosan is the second most plentiful biopolymer on earth,there are few reports on the conversion of chitosan biomass into furan derivatives.Chitosan is generated at a rate of about 100 billion tons every year.There is no satisfactory solution to utilize them at present.Therefore,the conversion of chitosan biomass and sucrose into 5-HMFare very important for the futureIn this study,we systematically studied the catalytic performance of ionic liquid,metals salt and solid acid on the yield of 5-HMF from chitosan biomass and sucrose in water-dimethyl sulfoxide mixture.In addition,several carbohydrates such as fructose,glucose,lactose,etc,were also tested in this system to determine 5-HMF conversion yields.To obtain a better understanding of GlcNAc dehydration pathways,HPLC-MS spectra were used to monitor this process.Meanwhile,we examined chitosan,GlcNAc,and their residues generated from chitosan by Fourier transform infrared(FTIR)analysis.Various reaction parameters,including reaction temperature and time,DMSO/water mass ratios and catalyst dosage were optimized.This dissertation mainly focus on the study as follows:Firstly,the ionic liquid N-methylimidazolium hydrogen sulfate([Hmim][HSO4])exhibited the best catalyst performance-achieving 5-HMF with yields of 34.7%and 64.6%from chitosan and GlcNAc,respectively,at 180? under hydrothermal conditions.And this catalysis system can be recycled at least five times.The results of HPLC-MS analysis show that the GlcNAc via ring-opening isomerization,deamination and further dehydration to form 5-HMF.Secondly,the direct conversion of chitin biomass to 5-hydroxymethylfurfural(5-HMF)over metal salts catalysts was studied,and FeCl2 exhibited the best performance-achieving 5-HMF with yields of 26.6%and 37.9%from chitosan and GlcNAc,respectively.Water-soluble oligosaccharide molecule was confirmed in reaction solution by HPLC-MS,and the peak-to-peak mass difference is 146 mass units,which is corresponding to the repeating units of GlcN(C6H11O4N)without-NH.Maybe the-NH2 group in chitosan structure was removed under the catalysis of FeCl2.As can be seen from the FTIR spectroscopies of solid residue,some of important functional groups were still present and other important functional groups were damaged during the hydrothermal process.Thirdly,several types of ILs and solid acids were used as catalysts in one-pot conversion of sucrose to 5-hydroxymethylfurfural.A remarkable 5-HMF yield of 91.8%was achieved catalyzed by CS2.3H0.7PW12O40 within 3 h at 180 ?,and the ionic liquid[Hmim][HSO4]gave the 5-HMF in 82.2%yield from sucrose.To the best of our knowledge,it was almost the highest yield of HMF from sucrose by now.Furthermore,the reaction mechanism of sucrose converting into HMF was speculated.Various reaction parameters including reaction temperature and time and catalyst dosage were optimized.