Effects Of Acid Modified ZSM-5 Catalysts On Hydrocarbon Selectivity Of Catalytic Copyrolysis Of Poplar Wood Sawdust And Highdensity Polyethylene

Biomass fast pyrolysis for bio-oil production is one of the promising technologies for the utilization of biomass.However,low heating value,high acidity(low p H)and chemical instability due to a large fraction of oxygenates are the main constraints for using bio-oil as an alternative to transportation fuel.Therefore,biomass catalytic pyrolysis is proposed as one of the upgrading technologies of bio-oil.Despite considerable progress in catalytic fast pyrolysis,challenges of biooil production completely lie with feedstock composition,reaction conditions and activity of catalysts used in the pyrolysis.Therefore,catalytic co-pyrolysis has brought the pyrolysis process one step forward by improving the quality of bio-oil and is significant to the development of biomass pyrolysis technology.The objective of this research was to improve the hydrocarbon yield from catalytic co-pyrolysis of poplar wood sawdust and high-density polyethylene over acid modified ZSM-5.The main results and achievements are as follows:(1)In this work,effects of acid modification on the catalytic performance of ZSM-5catalyst during co-pyrolysis have been evaluated.The ZSM-5 catalyst was modified by wet impregnation using different concentrations of sulfuric acid(0.1 M,0.3 M,0.5 M,and 0.7 M).Poplar wood sawdust and high-density polyethylene were mixed by grinding at a mass ratio of 1:1(wt.%)and then mixed with catalysts at 1:1(wt.%)for Py-GC/MS at 500 ℃.Results revealed that the highest yield of olefin(73.80 %)was observed over ZSM-5(0.3 M)and followed by 71.99 %over ZSM-5(0.5 M).Notably,there was no significant difference in alkane yield among catalytic co-pyrolysis processes,although the highest proportion of alkane was 13.06 % over ZSM-5(0.1M).The ZSM-5(0.5 M)was most selective for the highest amount of aromatic hydrocarbon yield(12.89 %)and led to the maximum hydrocarbon yield of 97.00 %.Furthermore,ZSM-5(0.5 M)showed better deoxygenation among catalysts used in this study.(2)In the catalytic co-pyrolysis,effects of temperature on the yield and selectivity of hydrocarbons were studied in this research.The ZSM-5(0.5 M)was selected from the previous study and used in Py-GC/MS of catalytic co-pyrolysis of poplar wood sawdust and high-density polyethylene at different temperatures of 450 ℃-650 ℃.For all the catalytic co-pyrolysis experiments,the mass ratio of catalyst and feedstock was 1:1(wt.%),while biomass and plastic had an equal share(1:1 wt.%).The results showed that the yield of olefin and alkane decreased,while aromatic hydrocarbon yield increased at high temperature reaching the highest value of18.87 % over ZSM-5(0.5 M)and 15.08 % over P-ZSM-5 at 650 ℃.The acidic compounds were eliminated at 650 ℃,whereas alcohol content gradually increased with elevating temperature.The proportion of monoaromatic hydrocarbons is relatively higher than undesirable polyaromatics at temperature of 550 ℃.(3)The role of catalyst loading on hydrocarbon yield has been investigated during catalytic co-pyrolysis over P-ZSM-5 and ZSM-5(0.5 M).Considering the abundance and selectivity of chemicals,550 ℃ was selected from the previous study and applied to the catalytic co-pyrolysis in Py-GC/MS at different catalyst loadings of 1:4,1:2,1:1,2:1 and 4:1(wt.%)in which the mass ratio of poplar wood sawdust and high-density polyethylene was 1:1(wt.%).Results showed that the relative abundance of olefin and alkane showed different trends at different loadings of PZSM-5 and ZSM-5(0.5 M)catalysts.However,the yield of aromatic hydrocarbon followed an increasing trend and reached a maximum of 34.57 % at 4:1 for ZSM-5(0.5 M)catalyst.Remarkably,all oxygen-containing species were completely deoxygenated at a catalyst loading of4:1 for both P-ZSM-5 and ZSM-5(0.5 M).Selectivity study revealed that total monoaromatic selectivity is relatively higher at 4:1 and there was no significant difference in polyaromatic selectivity compared with 2:1.Therefore,catalyst loading of 4:1 is efficient for high yield of hydrocarbons in catalytic co-pyrolysis.In summary,acid modified ZSM-5(0.5 M)catalyst,temperature of 550 ℃ and catalyst loading of 4:1 could be used in the co-pyrolysis of biomass and plastic for bio-oil production.Furthermore,this research work could be referred to as a directory study for catalyst modification,and selection of temperature and catalyst loading to maximize the hydrocarbon yield in future copyrolysis research.