Preparation Of Industrial Lignin-derived Carbon-based Solid Acids And Their Application In Furfural Production

The overexploitation of fossil resources will inevitably brings environmental pollution and energy crisis.Biomass,as a renewable resource with a wide range of sources and low price,has great potential in alleviating energy and environmental problems.Furfural derived from biomass,as an important platform chemical,can be used to prepare a variety of fuels and high value-added derivatives,and has great application prospects and development potential.At present,there are problems such as low yield,corrosion equipment,and high cost in the furfural industry.Nowdays,carbon-based solid acid catalysts have attracted the attention of scholars because of their many acidic sites,simple preparation,and recyclability.In this thesis,aiming at the green and efficient production of furfural and the difficulty of high-value utilization of industrial alkali lignin,a lignin-based porous carbon material was prepared by using industrial alkali lignin as raw material and synergistically with urea.The lignin-based porous carbon as a carrier,carbon-based solid acid catalysts were prepared by surface oxidation and ionic liquid modification,and applied to furfural production.The specific surface area,pore size structure and its formation mechanism of porous carbon materials were studied,and the effects of the structure,acid properties,and surface functional groups of carbon-based solid acids on the preparation of furfural from xylose dehydration were explored.As well as the properties of carbon-based solid acids catalyzing the preprationof furfural from cornco.The main conclusions are as follows:（1）Lignin-based porous carbon materials with high specific surface area and rich pores were prepared from industrial alkali lignin with urea assistance.NLC has high specific surface area and pore volume,reaching 1482 m² g^-1 and 0.9743 cm³ g^-1,and belongs to amorphous carbon.The addition of urea enabled the successful doping of nitrogen into the porous carbon materials,endowing high degree of defection in porous carbon materials.The synergistic effect of alkali and urea is the key to realize the preparation of porous carbon with high specific surface area and abundant pore structure.（2）A series of nitrogen-doped porous carbons with high specific surface area and abundant pores were prepared by adjusting the amount of urea added.And the carbon-based solid acid O-NLC-0.25 was successfully prepared by oxidation of hypochlorite using the obtained high specific surface area porous carbon NLC-0.25 as a carrier.In the two-phase reaction system of water and dichloromethane,O-NLC-0.25 catalyzed the production of furfural from xylose in a maximum yield of 76.69%,and the catalyst had high stability,retaining 61.81%of furfural yield after five consecutive uses.In addition,O-NLC-0.25 also obtained good results in the experiments of catalytic preparation of furfural from corncob,with the highest furfural yield of51.33%.（3）Using porous carbon NLC-x with different nitrogen doping amount and specific surface area as the carrier,the carbon-based solid acid AIL-NLC-0.67 was successfully designed and prepared by loading acidic ionic liquid.The prepared AIL-NLC-0.67 is rich in surface functional groups and is a porous carbon catalyst with both B-acid and L-acid acid sites.AIL-NLC-0.67 has high reactivity.The yield of furfural reaches 40.11%when water was used as the reaction solvent.In the two-phase reaction system of water and dichloromethane,after optimizing the reaction conditions,the highest yield of furfural could reach 86.09%.At the same time,AIL-NLC-0.67 has good cycle stability performance.The yield of furfural can still be 70.65%,after 5 consecutive uses.In addition,AIL-NLC-0.67 also achieved good results in catalyzing the reaction of corncob to furfural,and the optimal yield of furfural reached 62.08%.