Process optimization and properties of petroleum pitch/polyacrylonitrile electrospun carbon nanofibers
Objective Due to the complexity of its own components and structure,long-term low-value utilization of petroleum pitch often causes it to become an environmental pollutant.The research aims to achieve the high-value utilization of petroleum pitch by preparing pitch based composite carbon nanofibers,reducing the production cost and environmental pollution,and providing a reliable preparation method and process support for the application of carbon nanofibers in adsorption,energy storage and other fields.Method Petroleum pitch and polyacrylonitrile were dissolved in various solvents and mixed at different ratios to prepare the spinning solution for composite nanofiber production.Electrospinning technology was utilized to create the nanofibers from the solutions,and the spinning parameters including flow rate,voltage,and tip-to-collector distance were optimized using Box-Behnken response surface methodology.The composite nanofibers then underwent pre-oxidation and carbonization treatments at varying temperatures.The structural transformation of the fibers was analyzed by X-ray diffraction,fourier transform infrared spectroscopy,scanning electron microscope,and Raman spectroscopy.The effect of petroleum pitch ratio and carbonization temperature on the graphitization degree of the carbon nanofibers was investigated.Results The main factors affecting the fiber diameter were found to be the flow rate,spinning voltage and tip-to-collector distance,in descending order of significance.The optimal electrospinning conditions were obtained to be 0.64 mL/h flow rate,15.28 kV voltage,and 13.08 cm distance,resulting in an average fiber diameter of 342.43 nm with a relative error of 9.13％compared to the predicted value.The regression model was found to have high reliability and accuracy,as demonstrated by the response surface analysis and verification experiments.The structural transformation of the composite fibers during pre-oxidation and carbonization was analyzed systematically.The aromaticity index of the pre-oxidized fibers was found to be significantly affected by the pre-oxidation temperature,reaching the maximum value of 77.56％at 250 ℃.The linear structure of polyacrylonitrile was verified to convert into a ladder-shaped structure during pre-oxidation,and dehydrogenation reaction occurred in the molecular chain of the pre-oxidized fibers.The effect of petroleum pitch ratio and carbonization temperature on the graphitization degree of the carbon nanofibers was investigated.It was found that increasing the petroleum pitch ratio could improve the graphitization degree to some extent,and that the minimum value of R(the intensity ratio of D peak to G peak in Raman spectra)was obtained when the pitch ratio was 20％-30％.Increasing the carbonization temperature was found to reduce the fiber diameter and increase the crystallite size and interlayer spacing of the carbon nanofibers,indicating a gradual increase in the ordered structure of graphite with the increase in heat treatment temperature.Conclusion Petroleum pitch/polyacrylonitrile composite carbon nanofibers were successfully prepared using the electrospinning technology,and the spinning parameters were optimized using response surface methodology.The structural transformation and graphitization degree of the composite fibers during pre-oxidation and carbonization processes were investigated.It was found that the optimal pre-oxidation temperature was 250 ℃,and increasing the petroleum pitch ratio and carbonization temperature could improve the graphitization degree of the carbon nanofibers to some extent.Potential applications of the composite carbon nanofibers were identified in adsorption,energy storage,and catalyst support fields.Further research is needed to explore their performance and mechanism in these fields.Some challenges and limitations of the research method were also pointed out,including the difficulty of controlling the uniformity and orientation of the fibers,and the influence of solvent selection and environmental factors on the fiber morphology.
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