The Study On The Upgrading Catalysis Of Vapor Product From Pyrolysis Of Woody Biomass With ZSM-5 To Yield Aromatics

The severe energy crisis and the environmental problems originating from the abuse of fossil fuel,have increasingly drawn more and more attention on bio-energy.The biomass could be converted into invaluable liquid bio-oil through biomass pyrolysis.For resolving current problems of bio-oil,such as high content of oxygen,high acidity,low hot value as well as complicated compositions in bio-oil,pyrolysis and catalytic pyrolysis of Pinus yunnanensis were conducted on the fixed-bed pyrolysis reactor.This research mainly focused on mechanism of pyrolysis and catalytic pyrolysis of Pinus yunnanensis,the parameters of catalytic pyrolysis,modification of ZSM-5 by inorganic alkali,and ZSM-5 loaded by metal.The measurements of XRD,N2 adsorption-desorption,and SEM were used for characterization of catalysts,what is more,GC-MS was used to identify the compositions of bio-oil.Firstly,during biomass pyrolysis the influence of pyrolysis temperature,N₂ flow rate and the particle size of feedstock on the yields of products were studied.From the result of pyrolysis of Pinus yunnanensis,when the pyrolysis condition at pyrolysis temperature of 500?,with size of feedstock particle of 0.250 mm-0.420 mm and N2 flow rate of 150 m L/min produced the most bio-oil,reaching 50%.The bio-oil from Pinus yunnanensis pyrolysis contained lots of phenols,acids,aldehydes,ketones,alcohols,and esters.Secondly,the pyrolysis and catalytic pyrolysis in the presence of ZSM-5 of cellulose,hemicelluloses,lignin,and Pinus yunnanensis were conducted.The mechanism of biomass pyrolysis and catalytic pyrolysis of biomass was conjectured based on the yield of aromatic hydrocarbons and the content BTX?benzene,toluene,and xylol?in bio-oil.During catalytic pyrolysis of cellulose ZSM-5 efficiently converted furan,3-propyl glutaric acid,?-D-allose and 2,4-pentadienic acid into 1-methyl naphthalene,naphthalene and 2,6-dimethyl naphthalene.During catalytic pyrolysis of hemicelluloses,furan mainly was transformed into 2-methyl naphthalene,naphthalene and butylated hydroxytoluene.Through catalytic pyrolysis of the alkaline lignin,butylated hydroxytoluene was converted into 1,8-dimethyl naphthalene and 1,7-dimethyl naphthalene.During catalytic pyrolysis of Pinus yunnanensis,2-methoxy-4 methyl phenol,?Z?-isoeugenol,4-hydroxy-3-tertiary butyl benzene methyl ether were transformed into 1-methyl naphthalene,1-methylene-1-hydrogen-indene and 2,6 dimethyl naphthalene.Thirdly,during catalytic pyrolysis the pyrolysis temperature,catalytic temperature of gas phase,N2 flow rate,Si/Al ratio of ZSM-5,the ratio of catalyst to biomass,and the catalytic patterns?in-situ catalysis and ex-situ catalysis?were researched,and the optimal catalytic pyrolysis condition was confirmed based on the yield of aromatic hydrocarbons and the content BTX in bio-oil.For catalytic pyrolysis of Pinus yunnanensis,the optimal technological parameter was at pyrolysis temperature of 450?,catalytic temperature of 500?,N₂ flow rate of 150 m L/min with ex-situ catalysis?catalyst/biomass ratio of 3:1?using the ZSM-5 which the Si/Al ratio is 25.Fourthly,solutions of NaOH with various concentrations were applied for upgrading ZSM-5.Afterwards,the upgraded ZSM-5 were applied in biomass catalytic pyrolysis.Based on the yield of aromatic hydrocarbons and the content BTX in bio-oil,the effect of NaOH was concluded.Compared with the original ZSM-5,the catalysts after modifying of NaOH obviously decreased the content of BTX with the increase of naphthalene,2-methyl naphthalene and 2,6-dimethyl naphthalene in bio-oil.The last,the catalysts loaded wih Cu,Mg,Ni,Co,and Ga were conducted in catalytic pyrolyis,the best loading condition was studied.ZSM-5 loaded with sole metal had great effect on the types of aromatics rather than the content of overall aromatics.Zn-ZSM-5 drastically increased the content of BTX,restricting the polyaromatic hydrocarbon.What is more,the loading capacity enhanced the catalytic performance.In the presence of Zn-5wt%-ZSM-5,the content of BTX in bio-oil was 79.67%.However,Ga?Ni?Mg?Co and Cu loading on ZSM-5 decreased the content of BTX.Compared with ZSM-5 loading Zn-5 wt%,multiple Ga-Zn?Ga-Ni?Ga-Co and Zn-Ni reduced the content of BTX with the increase of polyaromatic hydrocarbon,while Zn-Co loading on ZSM-5 yielded equal content of BTX with less ethyl benzene and more 2-methyl naphthalene and more naphthalene.