HZSM-5 On-line Catalytic Cracking Of The Fast Pyrolysis Vapors Of Polyolefin-based Wood Plastic Composites

Wood plastic composite materials(abbreviated as WPCs)is a kind of composite materials made of wood and plastic wastes which can be recycled after regeneration and recycling.Because WPCsareunbiodegradable,we should consider the problem of WPCs wastes pollution to the environment.Both biomass(as a renewable carbon source)and waste plastic(as oil derivatives)are substance energy,so we can use them produce energy and chemical products through a variety of conversion technology.This method,realizing the recycling use of biomass and waste plastics,is recycling and low carbon economy.Based on this background,this paper mainly investigated the polyolefin-based WPCs fast pyrolysis to provide theoretical support on the WPCs transforming into fuel.The main research effort and results are as follows:The composition and distribution of polyethylene wood plastic composite(WF-PE)and polypropylene wood plastic composite material(WF-PP)fast pyrolysis products were investigated by Py-GC/MS.The results showed that the pyrolysis products of WF-PE and WF-PP basically can be regarded as the superposition of the polyolefin pyrolysis products and biomass pyrolysis products.The volatile products of biomass pyrolysis were oxygen containing compounds,such as alcohol,aldehyde,ketone,acid,furan,phenol and their derivatives.The volatile products of polyolefin pyrolysis were mainly consists of hydrocarbons,such as alkenes,alkanes and the diolefins.The hydrocarbons have high calorific value which contributes to the upgrading of bio-oil.The on-line catalytic cracking of the fast pyrolysis vapors of WF-PE,WF-PP,glucose,lignin,polyethylene(PE)and polypropylene(PP)on different Si/Al HZSM-5 were investigated using Py-GC/MS.The catalytic cracking mechanism of the WF-PP and WF-PE catalytic on HZSM-5 had been proposed.The results showed that the WF-PE and WF-PP fast pyrolysis vapors catalytic cracking by HZSM-5 produce large quantities of benzene,toluene,xylene,indene,naphthalene and other aromatic compounds.The aromatic compounds content increased with the silica alumina ratio reducing.The acid sites played an important role in the formation of aromatic compounds.After catalytic pyrolysis on HZSM-5,the acetic acid content decreased significantly,the bio-oils were upgraded.And the content of aliphatic hydrocarbon decreased,as well,the aromatic hydrocarbon and total hydrocarbon increased with the silica alumina ratio reducing.The formation of aromatic compounds in the catalytic cracking of WPC fast pyrolysis vapors on HZSM-5 may be in three ways.The first one is from the cellulose and hemicelluloses,which are pyrolized into anhydrosugar and hydroxy aldehyde through depolymerization and ring-opening reaction,then the anhydrosugar further cracked into furan,furfural and 5-HMF,and then those smaller molecule compounds converted into aromatic compounds by the HZSM-5 pore shape-selective.The second one is from the pyrolysis lignin derivatives,which are formed in pyrolysis of wood powder,then deoxidized under the catalysis of HZSM-5 generating aromatic compounds with C-O and C-C keys fracturing.The third one is from the pyrolysis products of PE or PP,the oligomer hydrocarbon,which were transformed into aromatic compounds by the shape-selective catalysis of HZSM-5.Also,the WPCs catalytic cracking on the multifunctional catalysts Me/HZSM-5(Me=Fe,Ni,Cu,Mo,Ag)were evaluated.The results showed that the catalyst HZSM-5 without metal had the best total products yield.The on-line catalytic cracking of WF-PP fast pyrolysis vapors on MexOy/HZSM-5 also produces large quantities of benzene,toluene,xylene,indene,naphthalene and other aromatic compounds.Considering the highest aromatics yield,the catalytic effecacy of HZSM-5 was best,and Fe/HZSM-5 behind.While Fe/HZSM-5 was best catalyst to obtain the higher aromatic hydrocarbon percentage content in the product,and the percentage content of aromatic hydrocarbon is 98%in the case of 20 percent of Fe in the catalyst.The Fe/HZSM-5 selectivity for producing benzene,toluene and xylene is very high.For the reducing conversion of aliphatic hydrocarbon,Mo(10)/HZSM-5 catalyst is the best.Considering the minimum percentage content of oxygen containing compounds was 0.64%,Fe(20)/HZSM-5 catalytic effect was best.