Preparation Of Aromatic Hydrocarbons By Catalytic Co-pyrolysis Of Walnut Shell/polypropylene

Biomass as a green,clean,renewable and environmentally friendly energy,the conversion of biomass energy into light aromatics(BTX)by thermochemical technology has become a global research hotspot.The key lies in improving the effective hydrogen-carbon ratio of biomass,preparing catalysts with high reactivity and excellent cycle performance.The hydrogen-carbon ratio of biomass raw materials,the pore size and surface acidity of the catalyst are the key factors affecting the preparation of BTX by biomass pyrolysis.The mixed pyrolysis of biomass and the structural characteristics of the catalyst are of great significance for the preparation of high yield light aromatics by biomass catalytic co-pyrolysis.In this paper,the experimental study on the preparation of light aromatics by walnut shell/polypropylene-catalyst mixed pyrolysis was carried out.Through the cyclic pyrolysis experiments of catalysts with different pore sizes,the effects of catalyst structure-pore size and catalyst metal active center on the preparation of light aromatics by walnut shell/polypropylene pyrolysis were further studied,and the reaction mechanism of the preparation of BTX by walnut shell/polypropylene catalytic co-pyrolysis was discussed.The main research contents of this paper are as follows:(1)Thermogravimetric-mass spectrometry-Fourier transform infrared spectroscopy(TG-MS-FTIR),gas chromatography-mass spectrometry(GC/MS)and tubular furnace reactor were used to investigate the catalytic co-pyrolysis of catalyst-walnut shell l polypropylene to prepare BTX.The results showed that compared with the pyrolysis of walnut shell alone,the activation energy of the mixed pyrolysis reaction of walnut shell/polypropylene decreased by 25 kJ/mol,indicating that walnut shell and hydrogen-rich material polypropylene had a positive role in promoting the pyrolysis reaction.After HZSM-5,MCM-41 and HBate were added,the activation energy of pyrolysis reaction further decreased,indicating that the molecular sieve catalyst had a positive promoting effect on the co-pyrolysis of walnut shell and polypropylene.In the mixed reaction of walnut shell and polypropylene catalyzed by different molecular sieve catalysts,the activation energy of pyrolysis reaction is in the order of HZSM-5<MCM-41<HBate,which indicates that the activation energy of walnut shell/polypropylene catalyzed by HZSM-5 is the smallest.(2)Non-catalytic and catalytic co-pyrolysis experiments of walnut shell/polypropylene were carried out by gas chromatography-mass spectrometry(GC/MS)and tubular furnace reactor.The catalysts used were microporous molecular sieve HZSM-5 and mesoporous molecular sieve MCM-41,and each pyrolysis experiment was carried out three times in parallel.The experimental results show that compared with non-catalytic pyrolysis,the addition of catalyst in walnut shell and polypropylene mixture can improve the content of BTX.After adding HZSM-5 and MCM-41,the relative content of BTX is about 40 area%and 18 area%,respectively,which is about 30 area%and 10 area%higher than that of walnut shell-polypropylene mixture.Therefore,the catalysts with different pore sizes have different effects on the preparation of aromatic hydrocarbons from biomass pyrolysis.(3)Four kinds of catalyst carriers with different pore sizes were prepared.The walnut shell/polypropylene was subjected to 10 times of cyclic pyrolysis experiments in a tubular furnace to determine the pore size structure that was most suitable for the preparation of aromatics and had good cyclic performance.On the selected optimal pore size carrier,different metal active centers(Zn,Ni,Ce)were loaded to investigate the characteristics of BTX prepared by mixed catalytic pyrolysis of walnut shell/polypropylene.The results showed that among the four catalysts with different pore sizes,the support with pore sizes of 0.55 nm～1.2 nm was the most suitable for the preparation of aromatics by biomass pyrolysis,and the cycle performance was the best.The relative content of BTX was between 9 and 20 area%,and the yield of BTX was 23～67 mg/graw.The catalytic effect of loading 10 wt%Zn was the best,and the relative content of BTX was 39.49 area%,and the yield was 111.13 mg/graw.The existing research level of biomass pyrolysis to prepare BTX at home and abroad was promoted.