Synthesis Of Carbon Nanotubes By Catalytic Pyrolysis Of Polyethylene And Their Adsorption Properties

Carbon nanotubes had been widely used as adsorbent materials,catalyst support material and supercapacitors owing to their superior physical and chemical properties.In the present paper,carbon nanotubes?CNTs?were first synthesized via in-situ catalytic pyrolysis of polyethylene using Fe,Co and Ni monometallic/bimetallic nanoparticles as catalysts.The effects of pyrolyzed temperatures,catalyst contents and type of catalysts,protective agents contents and type of protective agents on the growth of CNTs were investigated.Moreover,the adsorption capacity for methylene blue of as-prepared CNTs was also analyzed.Finally,graphene oxide/CNTs ultralight aerogel was prepared by hydrothermal reduction method,and its adsorption properties for oil were studied.The results indicate that:?1?CNTs were prepared via catalytic pyrolysis of polyethylene using ferric nitrate,cobalt nitrate and nickel nitrate as catalyst precursors.The catalytic activity of the nanoparticles was in the following order:Ni>Fe>Co,and Ni was the best catalyst for CNTs growth.The CNTs synthesized at the optimal conditions of 973 K/2 h and0.75 wt%Ni were 30⁵0 nm in diameter,tens of microns in length and almost 1500 in aspect ratio.?2?CNTs were prepared via catalytic pyrolysis of polyethylene using Fe,Co and Ni containing bimetallic nanoparticles.NiCo and FeCo bimetallic nanoparticle catalysts are not suitable for the growth of CNTs,and FeNi was the best catalyst for CNTs growth.The CNTs synthesized at the optimal conditions of 973 K/2 h and 0.50wt%FeNi were 20³0 nm in diameter and tens of microns in length.The catalytic activity of FeNi bimetallic nanoparticles is superior to that corresponding monometallic catalyst.?3?The effacts of protective agent type?including polyvinylpyrrolidone?PVP?,2,5-Furandione,polymers,polymer with 2-methyl-1-propene,ammonium salt?ISOBAN-104?,cetyltrimethyl ammonium bromide?CTAB?,sodium dodecylbenzene sulfonate?SDBS?and oleylamine?OAm??catalytic pyrolysis of polyethylene was investigated.OAm is suitable for the growth of CNTs,and Co was the best catalyst for CNTs growth.The CNTs synthesized at the optimal conditions of 773 K/2 h,0.50 wt%Co and R_OAm=6 were 5¹0 nm in diameter and tens of microns in length?molar ratio of protective agent to catalyst?.The specific surface area of as-prepared CNTs was195.71 m²·g^-1,and its maximum adsorption capacity for methylene blue was 107.13mg·g^-1.Comparing with CNTs prepared without protective agents,the reaction temperature decreased by 100 K,the specific surface area of the CNTs increased by about 6 times,and the adsorption capacity for methylene blue increased by about 4times.?4?Graphene oxide/CNTs ultralight aerogel was prepared using commercial graphene oxide and CNTs prepared via catalytic pyrolysis of polyethylene as starting materials.The ultralight aerogel showed excellent oil adsorption capacity and elasticity.The optimal conditions for preparation of ultralight aerogel were 433 K/12 h,0.10⁰.20 wt%solid content and m_CNTs:m_GO=4:6⁶:4.The maximum adsorption capacity of as-prepared graphene oxide/CNTs was 350 g·g^-1.