Synthesis of C60 Nanotube from Pyrolysis of Plastic Waste (Polypropylene) with Catalyst

Fullerene nanotube was synthesized in this research by pyrolysis of plastic waste Polypropylene (PP) at 1000 ° C for two hours in a closed reactor made from stainless steel using molybdenum oxide (MoO3) as a catalyst and nitrogen gas. The resultant carbon was purified and characterized by energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD). The surface characteristics of C60 nanotubes were observed with the Field emission scanning electron microscopy (FESEM). The carbon is evenly spread and has the highest concentration from SEM-EDX characterization. The result of XRD and FESEM shows that C60 nanotubes are present in Nano figures, synthesized at 1000 ° C and with pyrolysis temperature 400° C. The synthesis operation doing in one reactor and limited time.


Introduction:
Plastic materials are characterized by many properties that make them desirable in practical applications such as low cost, lightness and durability and as a result are necessary for our daily lives (1). Municipal solid waste is non-degradable and is not implemented in nature. It is disposed of by the way known as landfill, which accumulates multiple types of plastic waste. In these tombs there are many microorganisms that accelerate the degradation of organic matter associated with plastic waste (2). In many developing countries, the amount of plastic consumption is much higher than the average global consumption. The large production of plastic poses a major challenge to deal with these huge quantities of plastic waste after use. Plastic materials in solid waste release harmful chemicals in the soil that can then flow into the groundwater or other surrounding rivers and lakes so it can pose a significant risk to the organisms that drink contaminated water (3). Polypropylene is an attractive candidate for packaging applications and has a wide popularity in automobile and electronics field due to its excellent advantages of good thermal stability, chemical resistance, easy handling, good mechanical characteristics and inexpensiveness ) 4).
Department of Chemistry, College of science, University of Anbar, AL-Anbar, Iraq. * Corresponding author: amal990sh@gmail.com 8102 -8244 -0002 -https://orcid.org/0000 ID: ORCID * Waste materials from domestic wastes to industrial remains, rise harmful effects on environmental and human health regarded as a source of air, soil, water and marine pollution. However, wastes can be used as tools to produce useful goods. A significant technique to obtain this goal is pyrolysis. Pyrolysis relates to thermal decomposition that is operated in an air-free condition (5). Pyrolysis is a probable alternative to landfill for processing plastic waste, resulting decomposition products which can be used as" fuels instead of gas, diesel or fuel oils" (6). Additionally, pyrolysis of plastics has also been utilized to manufacture various types of Nano Carbon such as nanotubes, nanofiber, Nano rods, nanowires, etc., C 60 nanotube which have high value and exceptional physical and chemical properties because of their impressive characteristic like high surface area, porous-rich structure, high conductivity and excellent chemical stability, by blending plastics and catalyst in one reactor (7). The properties of carbon nanotubes and the percentage of the product depend mainly on raw materials. For instance, various methods have been developed to produce CNTs such as arc discharge, pyrolysis, laser ablation of carbon, plasma assisted deposition and chemical vapor deposition (CVD) (8)(9)(10). Fullerene is any molecule in the form of an ellipsoid, tubular or a hollow sphere structure composed entirely of carbon. They are generally referred to as "Buckyballs" (11). There are many types of fullerene such as C 60 rods and C 60 tubes (12). The research objectives are to increase the economic value to benefit from plastics waste and assist in addressing environmental problems associated with this waste and produce new nanomaterials that inter into the technological industry.

Preparation of system gas
The nitrogen gas bottle was connected to three traps, the first trap contained concentrated sulfuric acid (H 2 SO 4 ), which absorbed water from the gas, then the gas was passed to the second trap which contained a saturated solution of pyrogallol to absorb oxygen from the gas, finally the gas was passed to the magnesium sulphate (MgSO 4 ) to absorb the rest of the acid. Then the gas was passed to the reactor system through a trap.

Methods
The samples were washed, air-dried and shredded into small pieces of an area that's around 1mm². 25 g of shredded PP was placed inside a stainless-steel reactor that is filled with some inert gas (nitrogen) at low pressure (between 50 and 70 mbar). 0.5 g of (MoO 3 ) catalyst was placed in tube nozzle connected with reactor. The reactor was tightly closed and put in an electric furnace to be heated as shown in Fig.1. This reactor is connected to condenser and then to three neck round-bottom flask for products collection. Nitrogen gas was pumped at 25 ° C until the temperature reached 500 ° C. The temperature of the furnace was gradually raised. When the temperature of 400 ° C was reached and the wastes began to decompose, the catalyst was added from the tube nozzle. At this level the distillation process began and at the end of distillation the temperature was raised to required temperature. We used 1000 ° C for two hours, at a heating ramp rate of 13 °C/min, then allowed to cool to room temperature naturally. It was found that the final product in the reactor included carbon powder.

Carbon Nanotube Identification
The following equipments were used to identify C 60 nanotubes properties:

Field Emission Scanning Electron Microscopy (FE-SEM)
The morphology and size of samples were studied by scanning electron microscopy (SEM; FEG-SEM MIRA3 TESCAN, Czech Republic), which is configured to operate at (15.0 kV) various magnification level.

X-Ray Diffraction (XRD)
The X-ray diffraction (XRD, X'PERT PRO from Philips, Netherlands) was evaluated to determine the crystal structure and phase the samples, with Cu-Kα radiation (λ=1.54178 Å), operated at 40 kV and 40 mA, was measured in 2θ range from 10 o to 80 o , performed on a University of Kashan (Iran).

Energy Dispersive X-Ray Analysis (EDS)
The elemental composition of samples was studied by (EDS, MIRA3 TESCAN, Czech Republic) Figure 2A shows the XRD patterns of the PP pyrolysis at 1000ºC without catalyst and having the diffraction peaks at the value of 23º, 28.5º and 43º were ascribed to the (002), (100) and (101) reflections. Figure 2B shows the XRD patterns of the C 60 nanotubes from waste PP with MoO 3 , the diffraction peaks at the value of 23º, 28.5º and 43º were ascribed to the (002), (100)  The other peaks notices refer to the additives of polymer and the substrate used in the measurement (17)(18) Average crystal size in the product that can be found using X-ray diffraction profile. Calculating the crystal size (D) can be done by using the Debye Scherrer equation: D =

Results and Discussion:
Where is the Scherrer constant, λ is the wavelength of light used for the diffraction, β is the full width at half maximum of the sharp peaks and θ is the angle measured. The Scherrer constant ( ) in the above formula accounts for the shape of the particle and is generally taken to have the value 0.9 (19).  From Table1, we could calculate the average crystal size of C 60 NTs as shown below: Average crystal size = 84.17 nm.
The morphology of the sample was revealed by FESEM. Figure 3-A shows a typical FESEM image of the sample. It is found that large quantities of nanostructures (C 60 NTs) were obtained (12). These nanotubes are carbon (34.5-90.6) nm in diameter, and a few micrometers in length, as shown in Fig. 3 Figure 4 shows the high concentration of the carbon content which indicates high purity, and shows the amount of catalyst used in pyrolysis (20). The other elements noticed (Au, Si, Al and Cl) refer to the elements in standard in analysis device (21)(22), and the other components (K, Ca and Na) are additives to improve properties of polymer.

Conclusions:
CNT is successfully synthesized via a new experimental method by using one pyrolysis reactor of polypropylene at 400°C for about 30 minutes and decomposed the polymer chains at 1000°C for two hours with nitrogen ambiance. Resulting of XRD and FESEM shows there is carbon nanostructure at this temperature and marked by a peak intensity at 2θ = 23º, 28.5º and 43º. Moreover, the result of EDX shows that carbon is highest spread when compared with the others.