Catalytic Conversion Of Lignocellulosic Biomass Into Biofuels And High-value Chemicals

To high-efficiently utilize the lignocellulosic biomass, corncob and herb residuewere chosen as research objects in this thesis. Because of the difficulties for usingthese substrates directly, we employed some pathways via chemical methods andbiological methods, and tried to structure the transformation platform to biofuels andhigh-value chemicals. The key technologies and theoretical issues in these processeswere studied systematically.(1) Effect of formic acid on conversion of fructose to5-hydroxymethylfurfural(HMF) in biphasic system: A new process for the dehydration of fructose into HMF inaqueous/butanol media enhanced by using formic acid was developed. The effects offormic acid concentration, reaction temperature, and reaction time on the fructoseconversion and HMF yield showed the significant influences of these processvariables. Under optimum conditions, a HMF yield of69.2%was achieved.(2) Production enhancement of HMF from fructose in biphasic system: areasonable mechanism describing the effect of stirring speed on HMF yield inaqueous/butanol media was proposed. The optimization of stirring speed led to a highHMF yield of81.7%. By studying the kinetics of the fructose-to-HMF reaction, it wasdemonstrated that a low value of reaction rate constant was of benefit to obtain highHMF yield for this biphasic system. The simple addition process of high-fructosesolution greatly reduced the side-reaction and made the operation more continuousand stable, and a HMF yield of83.3%was achieved after three additions at1000rpm.(3) Direct conversion of glucose to HMF using Sn-ceramic powder catalyst:Combined with hydrochloric acid, a new ceramic powder catalyst containing Sn4+wasdesigned for the catalytic conversion of glucose to HMF. The effects of differentreaction factors on the prouction of HMF were investigated, and a HMF yield of63.9%was achieved. After being used five times, HMF yields were always above53.7%. This catalytic system demonstrated excellent activity in the conversion ofdifferent sugars, and showed a wide applied range.(4) Direct conversion of glucose to HMF using Cr2O3nanoparticle-loadedceramic powder catalyst: A process of synthesis of Cr2O3nanoparticle-loaded ceramic powder catalyst decreased the content of chromium in the ceramic powder catalyst to0.11%. Furthermore, combined with dilute sulphuric acid, the ceramic powdercatalyst catalyzed the conversion of glucose to HMF. The effects of different reactionfactors in this reaction system were investigated, and a HMF yield of63.2%wasachieved. This catalytic system demonstrated excellent activity in the conversion ofsome sugars (starch&sucrose), but less activity in the conversion of cellobiose andcellulose.(5) Conversion of corncob into high-value chemicals: After the pretreatment viaH2SO4-NH3H2O, corncob was separated into alkali lignin, hemicellulosichydrolysates and cellulose. Catalytic conversion of hemicellulosic hydrolysates intofurfural with a yield of79.1%was achieved. Catalytic conversion of enzymatichydrolysates of cellulose into HMF with a yield of42.0%was achieved.(6) Feasibility of ethanol production from herb residues using simultaneoussaccharification and fermentation (SSF): When only using glucoamylase for thesaccharification of radix glehniae residue, semen coicis residue and lily residue,ethanol concentration of45.9g/L was obtained via SSF-experiments. Via the enzymecomplexes of glucoamylase and GC220and fed-batch SSF-experiment, ethanolconcentration of33.8g/L was obtained from30%DM concentration (w/v) herbresidue of salvia miltiorrhiza.