Study On Co-Pyrolysis Characteristics And Synergistic Effect Of Chlorella Vulgaris And Polypropylene

The efficient and clean utilization of biomass and waste plastics is one of the effective ways to alleviate the energy crisis and environmental pollution and implement the "double carbon" strategy.In this paper,Chlorella vulgaris(C.V)and Polypropylene(PP)were selected as the research object.The catalytic co-pyrolysis characteristics,product distribution,functional group evolution and synergistic effect of C.V and PP were studied by thermogravimetric analyzer(TGA),Fourier transform infrared(FTIR)and pyrolysis-gas chromatography-mass spectrometry(Py-GC/MS).The results of TGA analysis indicated that the pyrolysis weight loss process of C.V and PP was mainly divided into three stages:drying dehydration,main pyrolysis and carbonization.The weight loss rate of PP(94.52%)was much higher than that of C.V,(77.03%)and the law of non-catalytic and catalytic co-pyrolysis weight loss rate was:co-pyrolysis<CaO catalytic co-pyrolysis<ZSM-5 catalytic co-pyrolysis.The kinetic analysis of coats-Redfern method showed that the activation energy of PP(349.51 kJ/mol)was higher than that of C.V(40.09 kJ/mol),and the activation energy of co-pyrolysis of C.V/PP was lower than that of single pyrolysis.The addition of ZSM-5 decreased the activation energy of co-pyrolysis,while CaO showed the opposite result.The results of FTIR analysis showed that PP was mainly composed of C-H and C=C,and C.V was mainly composed of C-H,oxygen-containing groups(O-H、O=C=O、C=O and C-O)and nitrogen-containing groups(C-N and O-N).The peak intensity of C-H and C=C increased continuously with the increase of PP blending ratio,while the peak intensity of nitrogen-containing and oxygen-containing functional groups gradually weakened.The removal of oxygen-containing groups and nitrogen-containing groups was significantly enhanced by the addition of CaO and ZSM-5.The removal of oxygen-containing groups by CaO was stronger than that by ZSM-5,and nitrogen-containing groups was weaker than that by ZSM-5.The Py-GC/MS experimental results showed that the bio-oil cracked by C.V was mainly composed of aromatic hydrocarbons,aliphatic hydrocarbons,oxygen-containing compounds,nitrogen-containing compounds and acids,while PP was mainly composed of aliphatic hydrocarbons and oxygen-containing compounds.It was found that the bio-oil produced by C.V had the lowest oxygenated compounds and the highest hydrocarbon yield at a pyrolysis temperature of 500℃;PP was found to promote the deoxygenation reaction of C.V and enhance the aliphatic hydrocarbons and reduce the content of acids,oxygenated and nitrogenous compounds when co-pyrolysis was performed;The addition of ZSM-5 and CaO further enhanced the deoxygenation and denitrogenation of hydrocarbons,with ZSM-5 preferring the conversion of aromatic hydrocarbons and CaO favoring the conversion of aromatic hydrocarbons to aliphatic hydrocarbons when catalyzed by co-pyrolysis.The results of synergism analysis suggested that the synergistic effects of weight loss rate and activation energy of co-pyrolysis and catalytic co-pyrolysis was the best when C.V:PP was 1:1 and 1:3,respectively.The addition of ZSM-5 reduced the activation energy value,while CaO resulted in the opposite.Co-pyrolysis has the best synergistic effect on reducing oxygen-containing compounds(ketone,aldehyde,ester,phenolic and acids)and BTEXs(benzene,toluene,ethylbenzene,and xylene),and increasing aliphatic hydrocarbons and alcohols when C.V:PP was 3:1.The best deoxygenation and denitrogenation and hydrocarbon enhancement was presented when C.V:PP was 3:1 with the addition of CaO.And the best deoxygenation,denitrogenation and hydrocarbon-enhancing effect was presented when ZSM-5 was added with C.V:PP was 1:1.