Experimental Study On Biomass Pyrolysis With Hydrogen Supply

In this paper,the biomass pyrolysis behavior with hydrogen supply by hydrogen donor and H2 atmosphere were studied.Firstly,the effect of low density polyethylene(LDPE)as a hydrogen donor on biomass pyrolysis was investigated.Then,the impact of H2 atmosphere on biomass pyrolysis product yield and bio-oil component was explored by comparing with the experimental results under N2 atmosphere.Hydro-pyrolysis experiments on cellulose,hemicellulose and lignin were carried out to research the hydrogenation reaction pathway,which provides a theoretical basis for the study of biomass hydro-pyrolysis mechanism.The sawdust and LDPE co-pyrolysis experiments were carried out to investigate the synergistic effects of co-pyrolysis on bio-oil yield and composition.The results showed that the bio-oil yield were improved by the co-pyrolysis process,the maximum bio-oil yield(56.84%)was obtained at 600℃,which is 6%higher than the theoretical value.The co-pyrolysis bio-oil composition analyzed by GC-MS showed that the co-pyrolysis would lead to the generation of some specific components,some oxygen-containing long-chain compounds such as undecanol and 2-heptenal,which are the products of free radicals interaction between biomass and LDPE.The sawdust and LDPE co-pyrolysis behaviors were studied by thermogravimetric-infrared spectroscopy.The results showed that the co-pyrolysis maximum reaction rate temperature was 490 ℃,which was 22 ℃ lower than that of LDPE pyrolysis(512 ℃).The pyrolysis characteristics of biomass under H2 atmosphere were researched.The influence of hydrogen atmosphere on bio-oil yield and composition were investigated by comparing with the results under N2 atmosphere.Compared with N2 atmosphere,the char yield decreased by about 9%under H2 atmosphere,and the liquid yield increased by 5.8%.As the presence of hydrogen promotes the isomerization of the furan ring,aromatic hydrocarbon compounds such as 2-methylnaphthalene were found in bio-oil under H2,which were not present under N2.The hydro-pyrolysis experiments of cellulose,hemicellulose and lignin were carried out to explore the specific hydro-pyrolysis pathway of biomass.The affects of H2 atmosphere on three components pyrolysis process were discussed.Lignin pyrolysis char yield was higher than cellulose and hemicellulose due to more aromatic rings and complex hydrogen bonds.The presence of hydrogen accelerates the furan ring molecule rearrangement reaction when cellulose pyrolysis,the benzene ratio in the oil increases,and the relative content of alcohol in the hemicellulose pyrolysis oil increases.During lignin hydro-pyrolysis,the hydrodeoxygenation reactions of volatiles were intensified,and the proportion of aromatic hydrocarbons in pyrolysis oil increased.