Experimental Study On Preparation Of Carbon Nanotubes By Pyrolysis Of Waste Tires

At present,the output of waste tires has soared,and its efficient treatment and disposal technology has attracted wide attention.The use of waste tires as a carbon source for the catalytic pyrolysis of carbon nanotubes is an emerging direction of its resource utilization.However,due to the traditional single metal catalysts,the particle size is too large and the catalytic activity is not high.There are many problems such as tube impurities;the mechanism of operation parameters affecting the yield and morphology of carbon nanotubes is unknown,and the mechanism of growth mode is unclear.Based on this,this article uses waste tires as a carbon source and transition metals as a catalyst to explore the influence of several factors on the yield and morphology of carbon nanotubes,and compares and analyzes the purification methods of carbon nanotubes.The carbon nanotubes were prepared by using Ni-Co/Al₂O₃ bimetal catalyst with waste tire as carbon source.The catalyst and carbon nanotubes were tested by SEM,TEM,XRD,Raman spectroscopy,BET and other characterization methods.Analyze the ratio of raw materials and catalysts for waste tires(1:1,1:2,2:1)and the atomic molar ratio of nickel to cobalt in the catalyst(Ni:Co=1:1,2:1,3:1)Of three factors,pyrolysis temperature(700?,800?,900?)on the yield and purity of carbon nanotubes.The co-precipitation method and gel-sol method were used to prepare Fe-Co-Ni trimetal catalysts.The effects of different catalyst preparation methods,different ratios of waste tire and catalyst,and different pyrolysis temperatures on the yield and purity of carbon nanotubes were studied.This article found through research:1.When preparing carbon nanotubes with Ni-Co/Al₂O₃ catalyst,the optimized conditions obtained after orthogonal test are that the ratio of waste tire to catalyst is2:1,and the atomic molar ratio of nickel to cobalt in the catalyst is 2:1.The pyrolysis temperature was 800?,and the maximum yield was 26.2%.The influencing factors that affect the yield and appearance of carbon nanotubes are as follows:the ratio of nickel and cobalt in the catalyst>pyrolysis temperature>the ratio of waste tire to catalyst.2.The gel-sol method was used to prepare the Fe-Co-Ni trimetal catalyst.The ratio of waste tire to catalyst was 2:1,and the pyrolysis temperature was 800?,the yield of carbon nanotubes was 27.6%.The yield of carbon nanotubes obtained using trimetal catalysts is higher than that of bimetal catalysts by 5%,which is attributed to the higher catalytic activity of the catalyst after the addition of iron elements,and the structure of carbon nanotubes is better regulated by nickel and cobalt elements.3.By comparing the purification methods of carbon nanotubes,it was found that the purification effect was better after mixed acid or concentrated nitric acid treatment.This article explores the influencing factors for the preparation of carbon nanotubes by bimetallic catalysts and trimetallic catalysts,and obtains optimized operating conditions,carbon nanotube growth methods,and carbon nanotube purification methods,which lays the foundation for industrialization promotion.