Catalytic Co-pyrolysis Characteristics Of Water Hyacinth And Scrap Tires Over Multilamellar MFI Nanosheets

Water hyacinth,as a kind of biological invasive species with strong reproductive ability,can be used as biomass resources.In order to overcome the characteristics of high oxygen content and low calorific value of biomass pyrolysis oil,and to improve the quality of liquid products,the research of biomass pyrolysis is developing in the direction of co-pyrolysis with other hydrogen-rich wastes such as scrap tires.In order to further improve the efficiency of the pyrolysis reaction,a zeolite catalyst is usually added to participate in the pyrolysis process.Ordinary zeolite such as HZSM-5 with micropore is easy to be blocked by carbon deposits during the pyrolysis process and cause poisoning and deactivation.However,catalysts with larger pores have poor catalytic performance due to their fewer acidic sites.Therefore,seeking a zeolite catalyst with both multi pore size and strong acidic sites to participate in the pyrolysis reaction is the current research hotspot.In this paper,water hyacinth and scrap tires are used as research objects,a new type of multilamellar MFI nanosheets catalyst is used for catalytic pyrolysis,and its catalytic effect is compared with the commercial HZSM-5 zeolite catalyst.The details of this work are as follows:Firstly,the pyrolysis characteristics of water hyacinth,scrap tire and their mixtures in different proportions were analyzed and the distribution of pyrolysis products was studied through thermal weight loss experiment and rapid pyrolysis experiment.In this paper,the yield and selectivity of the target product monocyclic aromatic hydrocarbons are used as important indicators for the quality evaluation of pyrolysis products.It is found that the mixed pyrolysis of water hyacinth and scrap tires has a synergistic effect.The synergistic effect is the most significant under the mixing ratio of 1:1,and the quality of the obtained pyrolysis product is the best.Secondly,the in-situ pyrolysis experiment method was used to study the influence of different zeolite materials and catalyst ratios on the distribution of co-pyrolysis products of water hyacinth and scrap tires.Then HZSM-5 and the multilamellar MFI nanosheets were characterized,and it was found that the multilamellar MFI nanosheets had an open multi-layer structure with multi-level pore size.Compared with HZSM-5,the multilamellar MFI nanosheets has a larger specific surface area and more strong acid sites.In-situ pyrolysis experiments found that under the same mixture and catalyst ratio,the use of multilamellar MFI nanosheets is more thorough than using HZSM-5 to remove oxygen-containing compounds in the pyrolysis product.Multilamellar MFI nanosheets can increase the ratio of monocyclic aromatic hydrocarbons up to 60.68%.Finally,in order to further improve the quality of pyrolysis products,the ex-situ catalytic pyrolysis experimental method was adopted.In each studied ratio,the average output of monocyclic aromatic hydrocarbons obtained from the use of multilamellar MFI nanosheets was12% higher than that of HZSM-5,the maximum output of monocyclic aromatic hydrocarbons can reach 69.18%.The effect of multilamellar MFI nanosheets on the conversion of aliphatic hydrocarbons to aromatic hydrocarbons is stronger than that of HZSM-5.Multilamellar MFI nanosheets has high selectivity to macromolecular monocyclic aromatic hydrocarbons(such as alkylbenzene and indene,etc.).The proportion of hydrocarbons in the pyrolysis products obtained by using multilamellar MFI nanosheets can reached over 89%.When using multilamellar MFI nanosheets for ex-situ catalytic pyrolysis experiments,the effect of less catalyst usage(material: catalyst=2:1)on removing nitrogen and oxygen compounds and increasing monocyclic aromatic hydrocarbon products is similar to the effect of the condition in material: catalyst=1:2 using in-situ catalytic pyrolysis method,indicating that the ex-situ catalytic pyrolysis method is better than in-situ catalytic pyrolysis.In summary,the use of multilamellar MFI nanosheets in ex-situ catalytic co-pyrolysis of water hyacinth and scrap tire can deeply reform the pyrolysis products,further improve the utilization value of the pyrolysis products and improve the quality of the pyrolysis oil.