Fast Pyrolysis Of Wood Plastic Composite And Catalytic Upgrading Of The Resulted Bio-Oil

Wood plastic composites(WPC)are composites that are primarily composed of a plastic matrix reinforced with biomass-based fibers and other additives.WPC is a kind of new material with the advantages of both wood and plastics,and its commercial products are increasingly replacing many products,especially in outdoor applications.WPC are considered to be an effective way to utilize waste lignocellulosic materials and recycling plastic waste,as well as offering alternative applications for virgin materials.Although WPC can be reprocessed many times,new waste will be produced eventually,as the mechanical properties of WPC decrease in quality because of the degradation of macromolecules.Both biomass and plastics are renewable energy sources.They can be converted into liquid fuel by fast pyrolysis technology.In order to increase resources use efficiency,the comprehensive and high efficiency pattern of biomass and waste plastic resources utilization,namely,"Wasteplastics+Biomass?WPC?Fuels",was put forward.The obtained pyrolytic oil from WPC via fast pyrolysis contains high proportions of oxygenated compounds and normal straight-chain paraffins.The resulting liquid should be refined before it can be used as a transportation fuel,due to its poor fuel properties such as high oxygen content,low heat values,strong corrosiveness,low stabilities and poor miscibility with fossil fuels for bio-oil and low light component contents and octane number for waste plastic pyrolysis products.The catalytic upgrading includes reducing the aldehydes and ketones content in pyrolysis oil to increase stability;reducing acid product to lower corrosion;deoxidizing oxygen-containing orgsanics to increase calorific value;obtaining isoparaffin from straight-chain paraffin through catalytic reformate to increase octane value;cracking large molecular organic components to small molecular organics to lower viscosity and density.In chapter two,thermo-gravimetric analysis(TGA)and pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)were employed to investigate the pyrolytic behavior and primary pyrolysis product distribution of the pyrolysis of cellulose,holocellulose,xylose,lignin,poplar wood(PW),high-density polyethylene(HDPE)and wood-plastic composites(WPC).The formation mechanism of the pyrolysis products and the mutual effects of poplar wood and high-density polyethylene were detailed discussed.The TGA indicated that cellulose has the highest onset temperature of pyrolysis and lowest char yield.Lignin decomposes over a broad temperature range and leads to the highest char yields.Xylose shows the lowest thermal stability.The thermal decomposition of biomass could be considered as the sum of the thermal decompositions of each individual chemical component.In comparison with biomass,HDPE decomposes at higher temperature over a rather narrow temperature range giving lower fixed carbon contents.The experimental char yield of WPC was lower than theoretical ones at final pyrolysis temperature.The reason could be that polyolefinic polymers provide hydrogen during thermal process with wood biomass and recondensation or recombination of thermal cracking products of biomass is reduced,resulting in the less amount of char production and enhancement of volatile products formation.The Py-GC/MS indicated that there was an interaction between biomass and plastic.Due to the lower temperature of biomass component decomposition compared with polyolefins,free radicals are formed from biomass pyrolysis and participate in reactions of plastic decomposition,yielding more light paraffins.Thereby,these experimental results showed a significant synergistic effect between plastic and biomass.Cellulose and hemicellulose exhibit similar pyrolysis pathways,consisting of depolymerization,dehydration to furan and pyran ring derivatives and furanose and pyranose ring-breakage to light oxygenated species such as acetic acid,furan derivatives,light aldehydes and ketones;among them,cyclopentenone and acetic acid were primarily produced from hemicellulose.Phenols were formed because of the cleavage and substitution of alkyl groups,ether links,?-O-4 bonds,and C-C linkages in lignin,along with side chains of aromatic subunits,C?-?and C?-? bond.The thermal cracking of WPC includes HDPE and poplar wood pyrolysis.In chapter three,different Si/Al ratio of the HZSM-5,HY,HUSY,HBeta zeolites and mesoporous Al-SBA-15 materials were developed and employed for catalytic cracking of WPC fast pyrolysis vapors using Py-GC/MS.As a result,after catalysis with these porous materials,all the aldehydes and esters were completely eliminated.Aliphatics were significantly decreased while large amount aromatics were obtained.A comparison of the products distribution results after catalysis with the zeolites and Al-SBA-15 catalysts showed that zeolites had better catalytic results for decreasing the content of acetic acid.The higher acidity of the catalyst should theoretically increase the propensity of the catalyst to promote cracking reactions.Inside the porous materials,the volatile species undergo a series of cracking,dehydration,decarbonylation,decarboxylation,isomerization,oligomerization,and dehydrogenation reactions that lead to aromatics.The catalysts showed selectivity of aromatics products.The HZSM-5(25)offered shape selectivity in terms of favourably producing more p-xylene than other catalysts.The biphenyls was selectively produced after catalysis with Al-SBA-15.The framework and Si/Al ratio of the catalysts plays a major role in their ability to effecti-vely catalyze the vapors and produce aromatic hydrocarbons.In chapter four,nanosolid superacids SO42-/ZrO2,SO42-/TiO2,SO42-/Fe2O3 and mesoporous nanosolid superacids MST,sul-SnO2-0.2-1.5,sul-SnO2-0.2-3 and sul-SnO2-0.33-3 were developed and employed for catalytic cracking of WPC fast pyrolysis vapors using Py-GC/MS.After catalysis,the products distribution was in line with the catalytic effects of Al-SBA-15.The selectivity of aromatics products was different for the catalysts.Long-chain alkylbenzenes were formed for all the catalysts,while biphenyls were formed by SO42-/Fe2O3,MST and sul-SnO2.The catalytic upgrading of WPC fast pyrolysis vapors with all catalysts not only lowered viscosity,but also increased stability,calorific value,octane value and hydrocarbon solubility.While the acetic acid was increased after catalysis except for zeolites.