Study On Hydrocarbon-Rich Oil Production From Microwave Catalytic Co-Pyrolysis Of Biomass And Low Density Polyethylene Using Modified Multistage Pore Molecular Sieve

Biomass resources are one of the most important renewable resources on earth and can be used as a substitute for liquid fuel.Biomass can be converted into liquid,solid and gas products via microwave pyrolysis.Environmental pollution and resource crisis induced by organic waste such as waste plastics have forced humans to develop effective solutions.Waste plastics will generate a large amount of hydrogen and hydrogen ions during the pyrolysis process.It will generate high value-added liquid fuels or chemicals with the supplement of hydrogen sources from the cracking of waste plastics during its co-pyrolysis with biomass.Due to the characteristics that lignin is not easy to be degraded and the structure is more complex,millions tons of lignin are abandoned every year,and a lot of lignin resources are wasted.Lignin can be converted into high-value products by catalytic pyrolysis,but there are disadvantages such as low yield of liquid products and poor selectivity in the process of catalytic pyrolysis of lignin.In order to deal with these problems,in this study,a modified multi-stage pore molecular sieve(M-ZSM-5/MCM41,M represents transition metal)with micropore-mesoporous structure was created,it is used to improve the conversion efficiency of intermediate macromolecules produced in the pyrolysis process of lignin,increase the yield of liquid products and their chemical selectivity.High-yield hydrocarbon-rich oil was obtained by microwave-assisted co-pyrolysis of lignin and low density polyethylene(LDPE),and the reaction mechanism and kinetic of the corresponding process were revealed.At the same time,microwave catalytic co-pyrolysis of lignin rich lignocellulosic biomass(peanut shells)and LDPE was studied,and the product yield distribution and reaction mechanism of the corresponding process were investigated.Therefore,it provides a theoretical and technical basis for the development of the application of lignocellulosic biomass and waste plastic resources.The obtained results are as follows:(1)Multistage pore molecular sieve(ZSM-5/MCM41)was prepared by hydrothermal synthesis method,and the multistage pore molecular sieve was modified by solution impregnation method to prepare multistage pore molecular sieve catalyst loaded with Ni,Zn,Mo and carried out SEM,XRD,BET,NH3-TPD characterization analysis.The results showed that Ni,Zn and Mo were successfully loaded on the multistage pore molecular sieve material.(2)In the microwave catalytic co-pyrolysis experiment of lignin and LDPE,the Zn-ZSM-5/MCM41 multi-stage pore molecular sieve catalyst showed the best catalytic activity;the optimized LDPE addition ratio was 25% of the lignin mass,a highest aromatic hydrocarbons(20.19%)was obtained;when the catalytic reforming temperature was 650?,the highest bio-oil yield was 19.81%,the hydrocarbons content in the bio-oil reached 87.22%,and the aromatic hydrocarbons content was about 20%,the phenols content was minimum as well.(3)The microwave catalytic co-pyrolysis of peanut shells and LDPE was studied,The reaction conditions was optimized by the central experiment method(CCD)during microwave catalytic co-pyrolysis of peanut shells and LDPE for hydrocarbon-rich oil production,quadratic models for the experimental yield,temperature and catalyst were established via response surface analysis.Results showed that the major components of the obtained bio-oil were hydrocarbons and phenols,the content of hydrocarbons in most cases were in the range of 61-68%(including 23-30% of aromatic hydrocarbons).In comparison with the control result(content of hydrocarbons was 28.45%(no aromatic hydrocarbons were observed),the phenolic compounds were 62.89%),the addition of Zn-ZSM-5/MCM41 catalyst obviously promoted the increase of hydrocarbons and the aromatic hydrocarbons included,there was also some promotion effect for bio-oil yield with the addition of the catalyst.The optimized reaction condition for hydrocarbon-rich oil production via microwave catalytic co-pyrolysis of peanut shells and LDPE was reaction temperature 550?,the amount of catalyst 12%,the obtained bio-oil yield was 30.25%,the hydrocarbons of bio-oil was 66.77%(including 29% aromatic hydrocarbons).(4)Thermal degradation behavior and kinetic analysis of lignocellulosic biomass(peanut shells and lignin)and LDPE were investigated.Results indicated that there was a synergistic effect during microwave co-pyrolysis of lignocellulosic biomass and LDPE.The addition Zn-ZSM-5/MCM41 promoted the the thermal decomposition behavior of biomass and LDPE,the thermal decomposition temperature tended to move to a lower reaction temperature range,and the thermal decomposition was more thorough.In the process of microwave catalytic co-pyrolysis of lignocellulosic biomass and LDPE,the modified multi-stage pore molecular sieve catalyst(Zn-ZSM-5/MCM41)significantly reduced the reaction activation energy,when peanut shells and lignin were used as feedstock,their activation energies decreased from 147.3 kJ/mol and 111.55 kJ/mol to 104.6 kJ/mol and 57.93 kJ/mol,respectively.