Catalytic Solvolysis Of Lignocellulosic Biomass To 5-hydroxymethypfurfural And Levulinic Acid

The energy crisis and environmental pollution are two main challenges nowadays.The conversion of renewable lignocellulosic biomass with abundant reserves and sources to high value-added chemicals is currently the focus of research and the development trend of future industries.The main researches in this thesis started with the conversion of renewable lignocellulosic biomass to highly value-added platform chemicals,and systematically studies the production of 5-hydroxymethylfurfural(HMF)and levulinic acid(LA)by using highly selective and stable solid acids,mild and efficient pretreatment,or a novel and green solvent system.The utilization of the residue after the preparation of LA from xylose residues was investigated.A mild co-solvent-enhanced dilute sodium carbonate(CELF-Na2C03)pretreatment method was used to improve the efficiency of corncob enzymatic hydrolysis.The amount of Na2CO3 used was only 2 g/L,and the co-solvent,THF can be recycled.It was found that the losing of glucose and sugar was significantly reduced after pretreatment,and 94.5%of glucose and 80.0%of xylose are obtained.By characterizing the physicochemical structure of the corncob after pretreatment,it was found that an amount of the lignin of corncob was removed after CELF-Na2CO3 pretreatment.The surface of the corncob became rough,and wrinkling was observed.No obvious lignin microsphere aggregation was observed on the surface.More effective contact sites were provided for enzymatic hydrolysis reactions.A synergistically catalytic conversion of glucose to HMF by AlCl3 and dilute hydrochloric acid in the biphasic system(CPME/H2O-NaCl)was systematically studied.It was found that the catalytic performance of only Lewis(L)acid AlCl3 was superior to that of only Bronsted(B)acid acid.The addition of dilute hydrochloric acid to AlCl3 solution not only provided the Bronsted acid site,but also regulated the Lewis acid site[Al(OH)2(aq)]that could catalyze glucose isomerization to fructose.It promoted the glucose conversion to HMF with a high yield of 54.5%.The HMF generated during the reaction was continuously extracted into the CPME phase,reducing the occurrence of side reactions.In addition,disaccharides and polysaccharides yielded a 40%of HMF;when xylose residues was used as a substrate,the yield of HMF reached 30.5%.The conversion of glucose to HMF by using mesoporous phosphorylated mixed oxide(P-TiO2-SiO2)was studied in detail.The yield of HMF was 63.0%at 170? for 90 min.This solid acid can be used for many cycles.The catalytic performance of P-TiO2-SiO2 was better than that of TiO2-SiO2.The moderate amount of acid(2.64 mmol/g)and the appropriate B/L acid ratio(0.21)of the solid acid contributed to the selective conversion of glucose to HMF.In addition,a mild concentrated H3PO4 pretreatment enhanced the solid acid-catalytic conversion of cellulose and biomass to HMF.The relationship of change in the composition of raw materials and crystallinity after mild pretreatment and the yield of HMF was revealed.The results showed that the decrease of cellulose crystallinity is beneficial to the catalytic conversion of glucose to HMF.The FeCl3-catalytic conversion of xylose residues to LA with under the mild high-concentration NaCl system was systematically explored.The high yield of LA was 68.0%at 180? for 2 h.The NaCl effectively destroyed the hydrogen bonds in cellulose,and promoted the hydrolysis of cellulose to the intermediate glucose under mild conditions.The LA-derived 2-MeTHF can efficiently extract LA with an extraction rate of more than 80%.The LA concentration was increased by the process strengthening technique of multiple batch reactions.The LA concentration was as high as 93.5 g/L,and the residue after the reaction had a high heating value similar to lignite.A sulfonated magnetic solid acid(MXRsC-SO3H)was prepared in situ using the residue after the LA reaction.In the pyrolysis process,the formation of pore structure and the generation of magnetic properties were promoted by the chemical reaction of Fe species.The MXRsC-SO3H with a high acid content of 2.31 mmol/g effectively promoted the dehydration fructose to HMF with a yield of 84.5%.The solid acid separation was simple,and the solid acid can be used repeatedly.This catalyst can also be effectively applied to the LA esterification and the sucrose hydrolysis.