Study On The Reaction Of Cellulose Catalyzed By FeCl₃-CuCl₂ To Produce 5-HMF In Two-phase System

Finding alternative energy sources for petroleum is a major challenge facing mankind.And it is also one of the 25 major scientific issues of this century published by journal of Science.Biomass,as the only renewable carbon source,is regarded as the most practical and available alternative to petroleum.Cellulose is an important component of biomass,which has the advantages of high natural reserves and does not occupy food resources.It is a high-molecular polymer formed by connecting glucose as a structural unit throughβ-1,4 bonds.It is also used as a raw material to prepare liquid fuels and high-value chemicals.Therefore,the pyrolysis of cellulose has important theoretical research and practical application significance.However,due to the uncontrollable cellulose depolymerization reaction and poor product selectivity,it is difficult to obtain platform compounds with high yield and purity,such as 5-hydroxymethylfurfural（5-HMF）and other furan derivatives.Choosing a suitable catalyst and reaction system is the key to solving this problem.Scientists creatively used a series of catalysts such as carbon-based catalysts,biological enzyme catalysts,and molecular sieve composite catalysts.Meanwhile,they also tried reaction systems such as ionic liquids,water,polyols,and methyl isopropyl ketone and so on.On the whole,there are still problems among the reaction such as complex catalyst preparation,high cost of solvent system,and massive inorganic acid used in the reaction process,which were required to be resolved urgently.This paper selected different two-phase systems,taking cellulose and its model compounds cellobiose,monosaccharide sugar and glucose as the research objects,using mixed Lewis acid FeCl₃-CuCl₂ as the catalyst to extract high-yield target products in time and prevent further product generation.The rehydration could even turn into carbon deposits.Kinetic calculations were carried out based on the experimental data,the apparent activation energy and reaction rate of the catalytic reaction were gained,and the conditions of the catalytic decomposition reaction were further optimized.Based on the product composition analysis and related characterization,the mechanism of cellulose degradation in the two-phase system with the mixed catalysts was reasonably inferred.The specific research content was as follows:1.The mixed catalyst FeCl₃-CuCl₂ in the two-phase system catalyzed the degradation of cellulose to prepare 5-HMFWe tookα-cellulose as the experimental object,and selected three different two-phase reaction systems:NaCl/n-butanol,NaCl/THF,NaCl/DCM according to the two-phase system selection rules,and catalyzed the degradation of cellulose by adjusting the mass ratio of the mixed catalyst,through GCMS,FTIR analysis of bio-oil,XRD,FTIR characterization of the residue after the reaction.The reaction temperature,reaction time,the volume ratio of the two-phase solvent,and the mass ratio of the catalyst were compared to the influence of the yield of product 5-HMF and furan derivatives.Therefore,the optimal reaction conditions were showed out:190℃,45min,NaCl/n-butanol（v/v=1:1）,mixed catalysts FeCl₃-CuCl₂（mg/mg=1:3）,in which the highest yield of 5-HMF obtained was 49.13%,and the content of furan derivatives was 2.98%.And on this basis,the reaction rate constant and apparent activation energy of the catalytic reaction at different temperatures were calculated according to first order reaction kinetics.The apparent activation energy was 21.65KJ/mol（190-230℃）by calculation,which was much lower than the apparent activation energy of the inorganic acid catalyzed reaction system（170-180KJ/mol）.We also performed UV-vis and Raman characterizations on the aqueous phase and the complex catalysts recovered from the aqueous phase after the reaction,which laid the foundation for the derivation of the reaction process of cellulose degradation catalyzed by the mixed catalysts.2.The mixed catalyst FeCl₃-CuCl₂ in the two-phase system catalyzed the production of 5-HMF from the cellulose model compoundWe used dimer cellobiose,monosaccharide sugar,and glucose as model compounds to carry out hydrothermal liquefaction reaction in the optimal two-phase system,and investigated the influence of factors such as reaction time,temperature on the output of the target product.In NaCl/n-butanol two-phase system,under mixed Lewis acid catalysis,the best reaction temperature and time for the three substrates were obtained at 160℃during 45min.Fructose had the highest selectivity to 5-HMF,the highest yield was 86%,the highest yield of cellobiose was 80%,and the highest yield of glucose was 82%.The experimental results showed that the mixed Lewis acid catalysts could effectively break theβ-1,4 bond and promote the dehydration of monosaccharides to selectively produce 5-HMF.According to the characterization results of GCMS and FTIR,combined with literature analysis,the reaction mechanism was investigated,and the cellulose decomposition reaction process was speculated based on the experimental results in Chapter 3.