Regulation Of Aromatic Hydrocarbons In Catalytic Co-Pyrolysis Of Biomass And Waste Plastics

Aromatic hydrocarbons are important chemical intermediates,among which benzene,toluene,ethylbenzene and xylene(BTEX)have high application value and are widely used in the production of chemicals.The catalytic co-pyrolysis of biomass and waste plastics is considered as one of the promising and valuable technologies in line to produce aromatic hydrocarbons with current energy utilization and solid waste management strategies.However,the oil produced by co-pyrolysis of biomass and waste plastics has low energy density,high viscosity,and low content of hydrocarbon fuels,resulting in unstable polymerization reaction,which seriously restricts the application of co-pyrolysis of biomass and waste plastics.In this paper,catalysts with different functions were prepared to regulate the products in pyrolysis oil and improve the selectivity of aromatic hydrocarbons and BTEX.A series of biochar catalysts were prepared by impregnating biomass with different chlorides to catalyze the co-pyrolysis of biomass and waste plastics.The results showed that the selectivity of furfural in the pyrolysis oil impregnated with ZnCl2 was the highest,reaching 95.34%.The fast pyrolysis derived carbon(F-AC)showed the best catalytic efficiency with 72.53%selectivity of aromatic hydrocarbons in pyrolysis oil and 32.17%selectivity of BTEX.Characterization results showed that F-AC had developed porous structure and rich oxygen containing functional groups,which improved the adsorption capacity of biochar intermediates in the reaction.The porous structure and high specific area provided a region for reaction intermediates to interact with reactive oxygen-containing functional groups,which enhanced the synergistic effect between biomass and waste plastics,thereby improving the selectivity of aromatic hydrocarbons.Zeolite catalysts with different b-axis lengths and different metal supports were synthesized by hydrothermal method,and their directional regulation ability of BTEX in the catalytic co-pyrolysis products of biomass and waste plastics was investigated.The experimental results showed that zeolite catalyst had excellent catalytic shapeselecting ability.When Si/Al was 50,catalytic temperature was 650℃,catalyst to raw material ratio was 2:l,the selectivity of aromatic hydrocarbons in pyrolysis oil produced by biomass and waste plastics co-pyrolysis was 96.98%,with 70.12%selectivity of BTEX.Among them,the ratio of p-xylene in xylene after co-pyrolysis was 94.82%,and the selectivity of PAHs decreased from 33.79%to 18.32%.The results showed that urea reduced the strength of Bronsted acid(B-acid)on the outer surface of the catalyst by changing the crystal size of zeolite catalyst,inhibited the alkylation of BTEX on the outer surface of the catalyst and the polymerization of monocyclic aromatic hydrocarbons,which improved the selectivity of BTEX.At the same time,the incorporation of ZnOH+interacted with the B-acid on the outer surface of the zeolite to generate new Lewis acid(L-acid)sites,which enhanced the activity of cyclization and dehydrogenation,inhibited the further oligomerization of aromatic hydrocarbons,and reduced the selectivity of polycyclic aromatic hydrocarbons.