Study On The Characteristics Of Biomass Pyrolysis Catalyzed By A New Type Of Composite Molecular Sieve

Biomass catalytic pyrolysis is one of the effective ways to transform low grade biomass energy into liquid fuel.It is a process of biodegradation of biomass under anaerobic or anoxic conditions.It will eventually produce bio-oil and flammable gases.Bio-oil produced by biomass pyrolysis can be used as fuel.However,the composition of the bio-oil is complex,the calorific value is low,the acid is strong and unstable,which restricts the large-scale use of bio-oil.The addition of suitable catalysts can change the pyrolysis process of biomass and improve the quality of bio-oil.Therefore,it is very important to find a suitable catalyst.At the same time,we need to proceed from the mechanism of biomass pyrolysis to make the process of biomass pyrolysis in the direction of our expectation.In this paper,based on the composition of biomass,the mechanism of catalytic pyrolysis of biomass components has been systematically studied in theory and experiment.In this paper,a microporous-mesoporous composite molecular sieve catalyst was prepared by molecular sieve Si-Al source method combined with two-step crystallization method.The physical structure and chemical properties of the ?(microporous molecular sieve catalyst)and MCM-41(mesoporous molecular sieve catalyst)were compared.Use commercially available microcrystalline cellulose and sodium lignosulfonate as raw materials.The pyrolysis behavior of them under the action of different catalysts and without catalyst was analyzed by the Thermo-Frequency Fourier Transformer(TG-FTIR).It is found that microcrystalline cellulose or sodium lignosulfonate have less residue in catalytic pyrolysis process,which indicates that adding catalyst can help them to degrade.In addition,the apparent activation energy(E),pre exponential factor(A)and reaction mechanism function of cellulose and lignin in the process of catalytic pyrolysis were solved by equal conversion method,Popescu method and double extrapolation method.The calculated results are in accordance with the results of the thermogravimetric analysis:The apparent activation energy of catalytic pyrolysis of cellulose and lignin was reduced,and the self-made composite zeolite catalyst greatly reduced the activation energy of pyrolysis of cellulose and lignin,indicating that the self-made catalyst was more conducive to the degradation of the two components.That is to say,the catalytic effect of the homemade catalyst on the pyrolysis of cellulose and lignin is better.The activation energy of catalytic pyrolysis of cellulose is 23.268 KJ/mol.The pyrolysis mechanism function is that the integral form is G(?)=?+(1-?a)ln(1-?);the differential form is f(a)=[-ln(1-?)]-1.The catalytic pyrolysis temperature of lignin is wide(200-550 ?),and the extrapolation activation energy is 422.043 KJ/mol.The pyrolysis mechanism function is that the integral form is G(a)=[-ln(1-?)]4;the differential form is f(a)=1/4(1-?)[-ln(1-?)]-3.The thermal pyrolysis gas chromatography mass spectrometry(Py-GCMS)was used to investigate the composition and product distribution of the pyrolysis of cellulose and lignin under typical conditions.The catalytic pyrolysis of cellulose produces more ketones,aldehydes,furans,esters and hydrocarbons.The analysis of cellulose pyrolysis showed that more ketones,esters,sugars and phenols were produced under the action of the composite molecular sieve catalyst than those of the other two catalysts.There are many kinds of lignin pyrolysis products,which mainly produce phenols,aromatic hydrocarbons,ketones,and carbohydrates.It was found that the homemade catalyst could promote the thermal cracking of lignin to produce more guaiacol.