Study On Pyrolysis Of Wood-Plastic Composites With The Hierarchical Zeolites

Due to the limited reserves of traditional fossil fuels and environmental concerns,the developmental of clean and efficient renewable energy is urgently required.waste plastics and biomass are pyrolyzed and directly liquefied by thermochemical conversion technology,which is the most common renewable energy technology.Due to the dual advantages of microporous and mesoporous materials,the hierarchical zeolites are applied to the co-pyrolysis of"oxygen-rich hydrogen-deficient"biomass and"hydrogen-rich"plastics,which can effectively improve the quality of liquid fuel.In this thesis,wood-plastic composite（WPC）was used as an experimental model of the blending of biomass and plastics.The pyrolysis/catalytic pyrolysis of WPC were systematically studied with the different pore sizes hierarchically structured MFI zeolites as catalysts.Details as follow:（1）We synthesized a kind of Bola form quaternary ammonium surfactant as the the Structure Directing Agents（SDAs）,and then synthesised the hierarchically structured MFI zeolites with different pore sizes(C₆-ZSM-5 and C₁₀-ZSM-5).Their morphology,structure and properties were characterized by XRD,SEM,BET and NH₃-TPD.The results showed that the the prepared samples belonged to MFI zeolites with high specific surface area,micropore and mesopore structures,and including Lewis acid site and Br?nsted acid site.（2）The optimal pyrolysis conditions of WPC and the interaction between wood flour and HDPE during the co-pyrolysis were investigated by using Py-GC/MS.The results showed that the optimal pyrolysis conditions of WPC were 600 ⁰C,20 ⁰C/ms and 10 s.WPC pyrolysis products included both oxy-organics（aldehydes,ketones,furans,phenols,etc.）and hydrocarbons with carbon number of 3-26（diolefins,olefins,alkanes and aromatics,etc.）,as well as Cyclohexane,2-propylene-,Furan,2-ethyl-,etc.Furthermore,the experimental contents of oxy-organics and heavy aliphatic hydrocarbons were lower than the theoretical values,while the contents of light aliphatic hydrocarbons and monocyclic aromatics were higher than the theoretical value,which indicated that there were interaction between wood flour and HDPE.The effects of C₆-ZSM-5 and C₁₀-ZSM-5 catalysts on products composition and distribution of WPC pyrolysis were investigated,and the interaction mechanism between wood flour and HDPE with C₁₀-ZSM-5 were investigated.The results showed that the hierarchically structured MFI zeolites had good catalytic activity.Wood flour-derived compounds could react with HDPE-derived olefins to form aromatics via C₁₀-ZSM-5catalyzed Diels-Alder reactions,which increased from 7.19%to 31%（C₆-ZSM-5）and 37.14%(C₁₀-ZSM-5).Compared with the rapid pyrolysis experiment,wood flour and HDPE did not interact in the slow co-pyrolysis process.However,under the action of C₁₀-ZSM-5,the temperature range moved to the low temperature zone to varying degrees,indicating that there was interaction between the two in the catalytic co-pyrolysis process.（3）The pyrolysis characteristic parameters,and evolutions of pyrolytic products of wood flour,HDPE and WPC were investigated by TGA and TG-FTIR.The results showed that wood flour pyrolysis included three stages:drying stage,pyrolysis stage and carbonization stage.HDPE pyrolysis was a one-stage reaction.WPC pyrolysis contained wood flour pyrolysis stage and HDPE pyrolysis stage.Compared with fast pyrolysis,there were not interaction between HDPE and wood flour in the slow co-pyrolysis process.However,There were obvious CO and CO₂ characteristic absorption peaks,and the thermogravimetric temperature range moved to the low temperature zone with C₁₀-ZSM-5 as catalyst.Their reaction activation energy was calculated by Flynn-Wall-Ozawa method（FWO）.The results show that the C₁₀-ZSM-5 catalyst reduced the reaction activation energy of WPC two-stage pyrolysis with drupped 8.7 KJ/mol and 88.8 KJ/mol,respectively.