Study On Sugarcane Molasses Preparation Of High-value Chemicals

Biomass resource represented by molasses and agroforestry residues is a good sustainable resource because of the fact that they are widely distributed,cheap and their regeneration cycle is short.Biomass can serve as feedstock for production of value-added chemicals,which attracts the attention of researchers at home and abroad.5-Hydroxymethylfurfural（HMF）and levulinic acid（LA）are recognized as green platform compounds with great potential.They have good chemical properties and can generate a large number of chemicals with wide application value.They are of great significance to the chemical,food and pharmaceutical industries.In this thesis,sucrose and sugarcane molasses were used as the starting material for production of HMF and LA.The research process of preparing HMF for sucrose and molasses mainly investigates the influence of factors such as catalyst,reaction system and reaction conditions.Results showed that Lewis acid AlCl₃ is effective in catalytic transformation of sucrose.Combining AlCl₃ with different Br（?）nsted acids,no matter whether they were inorganic acids or organic acids,or variation of ratio of Lewis acid/Br（?）nsted acid represented by AlCl₃/HCl,did not change the obtained maximum HMF yields compared with AlCl₃ alone,but shortened the time required to reach the maximum HMF yield.The nontoxic,renewable and biodegradation properties of GVL make it a promising reaction solvent.Addition of monovalent salt NaCl and divalent salt Na₂SO₄ produced opposite effect with Cl^-promoting while SO₄^2-inhibiting HMF production.Furthermore,HMF synthesis from constituent monosaccharides of sucrose and molasses,a by-product from sugar manufacturing process,was also carried out and it was found that an equivmole mixture of glucose and fructose gave rise to almost identical HMF yield to the same mole of sucrose.Molasses,even after chemical pretreatment for removal of certain amount of inorganic salts and color substances,was significantly inferior to synthetic molasses in terms of HMF formation,indicating the complexity and difficulty in chemical valorization of molasses for production of platform molecules.In the liquid acid catalyzed LA formation from sucrose in aqueous system,the optimum reaction conditions for LA preparation from 60 g/L sucrose（equal to the sucrose concentration in molasses after 6 times dilution）in aqueous phase were:reaction temperature of 160℃and catalyst loading of 0.1M AlCl₃+0.3M HCl.Under these conditions,the yield of LA from can reach as high as 67 mol%.The effect of non-sugar components in molasses on LA synthesis were investigated in detail.It was found that suspended solids,colloidal particles and pigments had no significant effects on LA production from molasses.Treatment of molasses with anion exchange resin D296R and cation exchange resin D001x7 for removal of the majority of anions and cations,respectively,significant improved LA production.Further experiments confirmed that anion SO₄^2-and cations Ca²⁺and Mg²⁺have inhibitory effects on LA preparation.Furthermore,two solid acids,i.e.strong acid cation exchange resin Amberlyst-15 and zeolite HZSM-5 were modified and applied in catalytic conversion of sucrose into LA.It was found that modification,however,did not significantly improved the catalytic activity of two catalysts in comparison to unmodified counterparts.