| The porous molecular sieve material has excellent shape selectivity,variable pore structure and huge specific surface area,it can not only play an important role in the fields of separation,chemical industry,adsorption,and petroleum catalytic cracking,but also promote the development of human energy structure and chemical structure.In addition,the large consumption of non-renewable energy such as petroleum has reduced the reserves,which has increased the utilization of renewable energy such as biomass.In particular,the catalytic conversion of biomass has been considered as one of the effective methods for the manufacture of biofuels and high value-added chemicals.The preparation of porous molecular sieve materials that can be used for the catalytic pyrolysis of biomass has high significance and value for the upgrading of biofuels.The main results of this paper are as follows:(1)Taking temperature,heating rate,and nitrogen flow rate as variables,and liquid yield as the response value,microwave non-catalytic pyrolysis of maize straw was performed.The quadratic mathematical regression equation is obtained by applying Box-Behnken statistical analysis in Design-Expert 8.0.6.1 software,and the result shows that this regression equation is very suitable for the test results.Variance analysis and response surface analysis were conducted according to the results,the primary and secondary order of the influence of the three factors on the yield of bio-oil is temperature > heating rate > nitrogen flow rate.The optimal process parameters for non-catalytic pyrolysis of maize straw are: temperature 563.30 ℃,heating rate16.21 ℃/min,nitrogen flow rate 78.43 m L/min,and maximum liquid yield of 27.63 wt%,which is close to the theoretical value.Under the optimal process parameters,the microwave catalytic pyrolysis of maize straw was carried out using mesoporous SBA-15,microporous ZSM-5 and meso-microporous composite catalyst ZSM-5@SBA-15.The results show that,compared with microwave non-catalytic pyrolysis,the relative content of hydrocarbons in the liquid product of microwave catalytic pyrolysis has undergone a "qualitative" change,from almost zero to 6.42 area%(ZSM-5@SBA-15).Meanwhile,the relative content of phenols also increased by ~16 area%,indicating that the presence of catalysts has a significant effect on the upgrading of liquid products.(2)With ZSM-5 as the core and SBA-15 as the shell,the meso-microporous composite catalyst ZSM-5@SBA-15 was prepared by hydrothermal synthesis and characterized by XRD,SEM,TEM,NH3-TPD.After the catalyst was applied to the microwave catalytic pyrolysis and rapid catalytic pyrolysis of coconut shell,the product oil was analyzed by GC-MS.The results show that the obtained composite catalyst ZSM-5@SBA-15 not only has the properties of the mesoporous catalyst SBA-15 but also the properties of the microporous catalyst ZSM-5.The introduction of SBA-15 reduces the acidity of the composite catalyst ZSM-5@SBA-15,and achieves the effect of upgrading bio-oil.Compared with non-catalytic pyrolysis,whether it is rapid catalytic pyrolysis or microwave catalyzed pyrolysis,the introduction of catalysts has caused a qualitative change in the relative content of hydrocarbons in bio-oil.The composite catalyst ZSM-5@SBA-15 has the most significant effect of microwave catalyzed pyrolysis of coconut shell,and the relative content of hydrocarbons has increased by ~41 area%.The combination of fast catalytic pyrolysis reactor and porous graded ZSM-5@SBA-15 can produce bio-oil rich in phenols(74.21 area%).The microwave reactor and ZSM-5@SBA15 catalyst are combined to produce bio-oil rich in hydrocarbons(41.71 area%).(3)Using a series of metal/ZAM-5@SBA-15-type catalysts,the three metals of gallium,zinc and nickel are introduced through the combination of ion exchange(iex)and impregnation(imp)methods to achieve the improvement of bio-oil by catalytic pyrolysis of biomass.Characterization of catalyst by XRD,SEM,TEM,XPS and pyridine infrared.The results showed that gallium,zinc,and nickel were successfully introduced on the ZSM-5@SBA-15 catalytic support,and during the rapid catalytic pyrolysis of maize straw,the bimetal modified Ga/Zn-ZSM-5@SBA-15-iex shows the most moderate acidity and the highest bio-oil yield(26.36 wt%).In the chemical composition analysis of biological oil,Ga/Zn-ZSM-5@SBA-15-iex showed the best selectivity to hydrocarbons(10.56 area%)and phenols(36.31 area%).(4)The core ZSM-5 of the composite catalyst was desiliconized by alkali treatment,and the hollow ZSM-5@SBA-15 multi-stage molecular sieve material was prepared.At the same time,the gallium-modified Hollow-ZSM-5@SBA-15 multi-stage molecular sieve material was prepared by the impregnation method,and the loading of different metals was changed.And perform XRD,SEM,TEM,NH3-TPD,BET,XPS,ICP and other characterization,and apply to the catalytic pyrolysis of coconut shell.The implication of results suggest that the alkali-treated multi-channel molecular sieve material has a large cavity,which can provide space for the catalytic conversion of organic macromolecules in the catalytic cracking of biomass,and shows a relatively high relative content of hydrocarbons(44.29 area%);When the loading of metal gallium is 11%,the catalytic performance is the best,and the relative content of hydrocarbons in the bio-oil is as high as 49.76 wt%.(5)Using ZSM-5 as a catalyst,microwave catalyzed pyrolysis of coconut shell.The research ranges of reaction time,heating rate,temperature,and nitrogen flow rate are 5-15 min,15-30 ℃/min,400-700 ℃,50-200 ml/min,respectively.The best relative content of hydrocarbons in bio-oil is 36.02 area%,and the best reaction conditions: reaction time is 10 min,heating rate is 20 ℃/min,temperature is 500 ℃,and nitrogen flow rate is 100 ml/min.The three factors of heating rate,temperature,and nitrogen flow rate were used as variables,and the relative content of hydrocarbons and phenols in bio-oil were used as response values to construct a model to further optimize the process parameters of coconut shell microwave catalytic pyrolysis. |
PDF Full Text Request