Preparation Of Industrial Lignin-derived Solid Acids And Research On Catalytic Hydrolysis Of Cellulose

Two kinds of lignin-derived solid acid were prepared from masson pine alkali lignin in black liquor of soda pulping via different thermochemical conversion methods,including pyrolysis and hydrothermal carbonization.And then,hydrochar and pyrochar were sulfonated with concentrated sulfuric acid.The generating lignin-derived solid acids were used to hydrolyze cellulose in an ionic liquid or aqueous reaction system.The details are as follows:First of all,refined alkali lignin was obtained using base-dissolving acidification method.And then it as carbon precursor to prepare lignin-derived solid acids?LDSA?by carbonization-sulfonation method.The effects of three different carbonization processes,which direct carbonization,H₂SO₄ pretreatment pyrolysis and H₃PO₄ activation carbonization pyrolysis,on catalytic performance of hydrolyze cellulose were investigated.The LDSA were characterized by FESEM,XRD,FTIR,TGA,BET and acid-base titration,respectively.A comparison study on the catalytic performance of LDSA prepared by different pretreatment method before carbonation in the hydrolysis of microcrystalline cellulose was carried out.Results show that LPC-SO₃ H exhibited superior catalytic activity due to its higher densities of-COOH group?1.68mmol/g?and-SO₃ H group?0.88 mmol/g?as well as its larger specific surface area?488.4m²/g?than those of the other two LDSAs.Afterwards,The LPC-SO₃ H was optimized on cellulose of hydrolysis and the catalytic performance other acid catalysts?H₂SO₄,HZSM-5,Amberlyst-15?were compared.And then,the adsorption properties and hydrolysis kinetics of solid acid on cellulose were preliminary investigated.The results showed that adsorption capacity of LPC-SO₃ H on cellobiose was much higher than that Amberlyst-15,and it was not adsorbed glucose.moreover,a total reducing sugar was higher and the yield was 50.8% in cellulose hydrolysis under the optimal reaction the reaction conditions of cellulose concentration of 6mg/mL and mass ratio of solid acid to cellulose of 3.3?w/w?,reaction temperature 180 °C,reaction time 3 h Additionally,the value activation energy for hydrolysis of MCC to reducing sugars using LPC-SO₃ H was 83.31 kJ/mol.On the side,the kind of SO₃H-functionalized lignin-derived solid acid were synthesized by hydrothermal carbonization method,using acrylic acid as the guide agent The effect of the additive amount of acrylic acid on the hydrolysis of cellulose in ionic liquid [BMIM]Cl was investigated in the process of hydrothermal carbonization.According to the characterization analysis?FESEM,XRD,FTIR,TGA,BET,XPS and acid-base titration?to elucidated the possible catalyst structure–performance relationship.Results showed that LHAC-SO₃H-40 prepared with adding 40 wt% of acrylic acid showed competitive catalytic activity for cellulose hydrolysis,which was attributed to its high densities of –COOH group?2.85 mmol/g?and –SO₃H group?1.58 mmol/g?.Compared to those conventional solid acid catalysts?HZSM-5,Amberlyst-15,?-Al₂O₃?,LAHC-SO₃H-40 exhibited high active catalyze for cellulose hydrolysis in ionic liquid [BMIM]Cl or aqueous reaction system.And then,the process conditions for hydrolyze cellulose were optimized.Results showed that the highest total reducing sugar yield of 75.42% was achieved under reaction conditions of 50 mg of cellulose,60 wt% of solid acid loading,10 mg of deionized water,reaction temperature of 130°C and reaction time of 2 h.Furthermore,TRS yield with 5 cycles for LAHC-SO₃H-40 was higher than 68.09%,and the active stability of catalyst could be fully recovered easily by regeneration in concentrated sulfuric acid.