Study On Selective Fast Pyrolysis Of Typical Biomass To Produce High Value-added Chemicals

Fast pyrolysis is an important biomass thermochemical conversion technology which can convert solid biomass into liquid bio-oil,char and non-condensable gas.Compared to solid biomass,bio-oil has the advantage of reproducibility,easy to transport,and high energy density.However,the composition of bio-oil obtained by conventional pyrolysis reaction is complicated.The selectivity of bio-oil is poor,thus significantly inhibiting its application in the current thermochemical industry.Based on this background,experiments were conducted in this dissertation to produce value-added chemicals from selective fast pyrolysis of biomass,and the works can be divided into five sections:1.Interaction characteristics and mechanism in the fast co-pyrolysis of cellulose and lignin model compounds During biomass fast pyrolysis process,the interactions among biomass components will affect the pyrolytic product distribution.In this study,D-glucose and a ?-O-4 type lignin model dimer(LMD)were selected as the model compounds of cellulose and lignin.The interaction characteristics and mechanism during their fast co-pyrolysis process were investigated by combined pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)experiments and density functional theory(DFT)calculations.The Py-GC/MS results indicated that the presence of LMD significantly decreased the formation of levoglucosan from D-glucose,while promoted the formation of linear carbonyls and furans.Meanwhile,the presence of D-glucose enhanced the decomposition of LMD to generate phenolic compounds.2.Catalytic fast pyrolysis of cellulose and biomass to selectively produce levoglucosenone Magnetic superacid(SO42-/TiO2-Fe3O4)was prepared for catalytic fast pyrolysis of cellulose and poplar wood to produce levoglucosenone(LGO).Its catalytic activity was evaluated via Py-GC/MS experiments,and compared with the non-magnetic SO42-/TiO2,H3PO4 and H2SO4 catalysts.The results indicated that the magnetic SO4-/TiO2-Fe3O4 was effective to selectively produce LGO from both cellulose and poplar wood.Its catalytic capability was a little better than the non-magnetic SO42-/TiO2 and H3PO4,and much better than the H2SO4.The maximal LGO yields from both cellulose and poplar wood were obtained at 300? with the feedstock/catalyst ratio of 1/1,reaching as high as 15.43 wt%from cellulose and 7.06 wt%from poplar wood,respectively.Activated carbon(AC)prepared by chemical activation with H3PO4(named as AC-P)was employed for catalytic fast pyrolysis of cellulose and biomass to selectively produce LGO.The catalytic pyrolysis behaviors and product distributions were revealed via both analytical Py-GC/MS and lab-scale experiments.The results indicated that the AC-P catalyst was effective to selectively prepare LGO from both cellulose and biomass,and performed better than other catalysts.Pine wood showed the best selectivity to produce LGO.The maximal LGO yield of 18.1 wt%and 9.1 wt%were obtained from cellulose and pine wood respectively in Py-GC/MS experiments under catalyst-to-feedstock ratio of 1/3 at 300?.Whereas,the lab-scale setup obtained the highest LGO yield of 14.7 wt%and 7.8 wt%from cellulose and pine wood.Furthermore,granular AC-P catalyst exhibited good reusability and stability in the recycling experiments.Stable yields of LGO above 12.5 wt%from cellulose were obtained in six consecutive runs without any regeneration of the recycled granular AC-P catalyst.3.Fast pyrolysis of corn stalks to selectively produce 4-vinyl phenol(4-VP)and 5-hydroxymethyl furfural(5-HMF)Fast pyrolysis of specific corn stalk(CS)materials offered a promising and convenient way to selectively produce two valuable compounds,i.e.,4-VP and 5-HMF.In this study,CSs at five different growth stages were prepared,including trefoil stage,elongation stage,heading stage,ripening stage and full ripening stage.Moreover,three fractions were separated from CSs except the CS of trefoil stage,including leaf,stem bark and stalk pulp.Fast pyrolysis of CSs were performed via Py-GC/MS technique.The results indicated that the pyrolytic characteristics of these CSs differed greatly from each other.4-VP and 5-HMF were the two major products at low pyrolysis temperatures.Stem bark at elongation stage was the best feedstock for selective production of 4-VP,with a yield of 4.98 wt%at 300?.Stalk pulp at ripening stage was optimal for selective production of 5-HMF,with a yield of 4.87 wt%at 300?.4.Catalytic fast pyrolysis of sugarcane bagasse using activated carbon catalyst to selectively produce 4-ethyl phenol(4-EP)AC prepared by physical activation with steam(named as AC-H2O)was employed for catalytic fast pyrolysis of bagasse in hydrogen atmosphere to selectively produce 4-EP.Lab-scale fast pyrolysis experiments were conducted to quantitatively determine the pyrolytic products and investigate several factors on the 4-EP production.The results indicated that the AC-H2O catalyst exhibited much better performance on 4-EP production than other ACs prepared by different activation methods.Compared with the inert atmosphere,the presence of hydrogen atmosphere could significantly promote the 4-EP formation with the yield increase by over 36%.The maximal 4-EP yield of 3.55 wt%with the selectivity of 17.42%was obtained under AC-to-bagasse ratio of 1.5 at 330?.5.Selective production of nicotyrine from catalytic fast pyrolysis of tobacco biomass with Pd/C catalystA new technique was proposed to selectively produce nicotyrine from catalytic fast pyrolysis of tobacco mixed with the Pd/C catalyst.Py-GC/MS experiments were performed to investigate the effects of pyrolysis temperature and catalyst-to-tobacco ratio on the selective nicotyrine production.The catalytic activity of the Pd/C catalyst was compared with those of the AC,Ru/C and Pd/SBA-15 catalysts.The results indicated that during the catalytic fast pyrolysis process,the Pd/C catalyst possessed promising dehydrogenation capability to selectively convert the nicotine in tobacco into the nicotyrine,and it performed much better than the other three catalysts.The maximal nicotyrine yield reached as high as 2.80 wt%,obtained at the pyrolysis temperature of 400? and catalyst-to-tobacco ratio of 2.