Catalytic De Polymerization Of Lignin To Aromatic Compounds And The Influence Of Lignin-first Transformation On Holocellulose

Lignin depolymerization to aromatic compounds will reduce the societies' dependence on fossil resources,and improve tec.hno-economic feasibility of transformation of whole lignocellulosic biomass to fuels or value-added chemicals.Lignin features structural complexity and recalcitrant character,and it also suffers from structural changes and chemical properties variation during the biomass fractionation procedure.Therefore,catalytic hydropyrolysis of lignin at ambient pressure and protolignin primarily depolymerization as well as the concurrent influence on the rest of holocellulose(i.e.,structure and pyrolysis behavior)were studied in this thesis.The main investigations and results are as follows:(1)MoO3 was employed in lignin catalytic pyrolysis in the presence of H2 under ambient pressure,discovering that it not only facilitate the depolymerization of lignin,but also hydrodeoxygenated lignin intermediates,that enhanced catalytic efficiency was achieved with the rising reaction temperature and amount of catalyst,and that liquid products were mainly consisted of phenols and benzene rings were unsaturated.When lignin to MoO3 ratio of 1/4 was introduced,the relative concentration of phenol in liquid products under 400,500,and 600? were 17.2%,27.5%,and 44.3%,respectively;under 500?,the relative concentration of phenol in liquid products with lignin to MoO3 ratio of 1/2,1/4,and 1/6 were 15.7%,27.5%,and 51.5%,respectively;(2)Ru/C and Raney Ni were used to depolymerization lignin primarily,and found that catalyst to biomass ratio has a positive correlation with lignin oil yield at a certain range.When a Ru/C to biomass mass ratio of 0.075 was used,it produced 31.6 wt%of lignin oil and 45.6 wt%of holocellulose.Comparing the catalytic performance of Ru/C and Raney Ni,it could be concluded that the latter owned better ability in breaking linkage like ?-5 and ?-O-4 than the former;(3)Crystallinity of holocellulose derived from lignin-first depolymerization were evaluated,suggesting that Raney Ni holocellulose had a higher crystallinity index than Ru/C based on X-ray diffraction,i.e.,91.9%versus 84.1%.Fixed bed and free-falling bed reactor were used investigating their pyrolysis behavior.In free-falling bed reactor at 500? under N2 atomsphere,the relative concentration of phenols in liquid product from Raney Ni holocellulose and Ru/C holocellulose pyrolysis were 1.2%and 8.4%,and solid yields were 35.8 wt%and 29.7 wt%,respectively,indicating that Raney Ni depolymerized protolignin efficiently than Ru/C,and that the former procedure generated a shorter chain length cellulose.