Study On Experiment And Mechanism Of Biomass Dual Catalytic Pyrolysis To Produce Upgrade Bio-oil

As a kind of renewable energy with huge reserves and wide distribution,biomass energy can be used to produce high value-added chemicals and fuels through pyrolysis,which utilization has great potential under the situation of increasingly severe energy and environmental challenges.However,the bio-oil prepared by conventional pyrolysis of biomass has many problems,such as high oxygen content,low calorific value,strong corrosiveness and poor stability,etc.,which restrict the storage,transportation and application of bio-oil.Therefore,it is necessary to take measures to improve the bio-oil to produce high-grade biofuel.In this paper,rice husk was used as raw material and the effects of composite modification and transition metal modification on the catalytic performance of the catalyst were investigated with Py-GC/MS reactor.The microwave fluidized bed test bed was used to conduct synergistic catalytic experiments with porous metal elements and molecular sieve catalysts to explore the best catalysis-deoxidation system.And the quantum chemistry software was used to simulate the non-catalytic and catalytic pyrolysis reactions of the three components of biomass,to explore the influence of catalyst on the pyrolysis reaction,and to provide data support and theoretical basis for the selection and optimization of catalyst.In the catalytic performance of the modified molecular sieve catalyst,the H/M mesomicroporous composite molecular sieve prepared by the composite modification of HZSM-5increased the selectivity of hydrocarbons from 51.73% to 69.84%,but the proportion of polycyclic aromatic hydrocarbons(PAHs)in hydrocarbon products was higher.After metal modification of MCM-41 by Cu,Fe,Co and Ni,Cu,Fe and Ni will lead to a small decrease in the content of hydrocarbon products but will increase the proportion of small molecular chain hydrocarbon in hydrocarbon products.Ni can slightly increase the content of hydrocarbons but has little effect on the proportion of hydrocarbon products.After the modification of H/M by transition metal,Cu showed the best inhibition effect on PAHs,and the PAHs decreased from22.90% to 17.89%.Ni modification had the best effect on the improvement of hydrocarbon products,and the total hydrocarbon content increased from 69.84% to 70.91%.The content of hydrocarbons in the non-catalytic pyrolysis products of algae reached 22.31%,which was much higher than that of rice husk.However,the content of hydrocarbons in the pyrolysis products under the catalysis of molecular sieve was lower than that of rice husk.Moreover,molecular sieve catalysis could not reduce the content of nitrogen-containing organic matter in the pyrolysis products(>20%),so molecular sieve catalyst was not suitable for the catalytic pyrolysis of algae organic matter.In the microwave fluidized bed pyrolysis test,when the pyrolysis temperature was 550℃,the content of liquid products reached the highest 40.63%.Under single stage metal catalysis,the content of hydrocarbon in the pyrolysis products does not increase obviously,while the content of acids and aldehydes decreases,and the stability of the pyrolysis products increases.The content of hydrocarbon products increased from 17.78% to 21.22%(Cu)under H/M single catalysis,and the selectivity of Ni to aromatic hydrocarbons was the highest at 27.20%.The Cu-H/M+Ni system showed the best catalytic effect during the co-pyrolysis of metal elemental substance and metal modified H/M,and the content of hydrocarbon products reached 22.14%and the proportion of single cyclic aromatic hydrocarbons reached 31.26%.In the quantum chemical simulation of the three-component catalytic pyrolysis reaction of biomass,hemicellulose is easy to be pyrolysis in the three components,and the activation energy of ring-opening reaction of monomer is 178.87 k J/mol and that of cellulose is 251.71 k J/mol.In the subsequent chain breaking reaction of ring opening,the activation energies of several reaction paths of hemicellulose and cellulose under uncatalyzed conditions are all about80 k J/mol,which means that each reaction path is competitively close to each other.Ni O catalyzes and promotes the partially broken link diameter obviously.The activation energy of eight reaction paths decreased from 332.00 k J/mol,324.43 k J/mol and 369.24 k J/mol /mol to257.40 k J/mol,266.31 k J/mol and 277.61 k J/mol,respectively,which was much lower than that of other reaction paths.The competition of the three reaction paths increased,and the products of the three paths were mainly three-carbon and four-carbon fragments,and the content of lowmolecular-weight compounds in the pyrolysis products increased.