Study On The Preparation And Hydrogen Storage Properties Of PAN-ACHF

In this work, activated carbon hollow fibers (ACHF) were prepared from polyacrylonitrile (PAN) hollow fiber through oxidation, carbonization and activation. The preparation and reaction mechanism of PAN-based activated carbon hollow fibers (PAN-ACHF) with high adsorption capacity were studied.The influence of the oxidation, carbonization and activation conditions on the structure and properties of the result ed ACHF was discussed. And the effect of morphologies on hydrogen adsorption capacity was preliminary investigated.Effects of oxidation on the structure and properties of PAN-ACHF were studied during the process of oxidation, and the optimal oxidation condition was selected. With the increasen of oxidation temperature and duration, the adsorption capacity of Iodine and Methylene blue of ACHF first increased, then decreased, and reached maximum at 250℃ for 2hr.. The higher oxidation temperature and longer time contribute to the change of AI-Aryl Index value yield of ACHF, which increases at the beginning then slides down. The quicker the oxidation heating rate, the higher yield of ACHF. The effect of oxidation heating rate on the adsorption capacity of Iodine and Methylene blue of ACHF is not remarkable. The results show that the optimal oxidation condition is 250℃ for 2hr..Effects of carbonization condition on the structure and properties of PAN-ACHF were studied during the process of carbonization, and the optimal carbonization condition was selected. The results show that with the increase of the carbonization temperature and duration, the specific surface area and adsorption capacity of Iodine and Methylene blue increase, and reaches maximum at 900℃ for 1hr.. The yield of ACHF first increases and then decreases with the increase of carbonization temperature. The longer duration of carbonization the lower yield of AHCF. The quicker the carbonization heating rate, the larger specific surface area and adsorption capacity of Iodine and Methylene blue of ACHF. However, ACHF at low carbonization heating rate has higher yield of ACHF.Effects of activation condition on the structure and properties of PAN-ACHF were studied during the process of activation, and the optimal activation condition was selected. The results show that with the increase of the activation temperature and duration, the yield of ACHF which prepared through activation with carbon dioxide(CO2) decreased, and the specific surface area increased which not exceed 1000m²/g. PAN-ACHF was activated by potassium hydroxide (KOH), which has larger specific surface area approach 2000m²/g and higher yield than PAN-ACHF that prepared by CO₂ activation method. The specific surface area and adsorption capacity of Iodine and Methylene blue of ACHF are increased with the KOH dipping concentration. The specific surface area and adsorption capacity of Iodine and Methylene blue of ACHF reach maximum at 900℃ for 60min.PAN-ACHF has larger specific surface area and better adsorption capacity for Iodine and Methylene blue than PAN-based activated carbon fibers (PAN-ACF) which during the same oxidation, carbonization and activation condition, with the increase in amount of activating agent (KOH), the surface area and pore volume increase significantly.The token about pore structure of PAN-ACHF was studied, especially about the distribution of pore diameter and pore volume of PAN-ACHF. The results show that there are mostly microspores in PAN-ACHF, and the dominant pore size is about 0.8nm.The hydrogen storage was measured. The result shows that samples, which has larger pore volume and specific surface area has the higher rate of hydrogen adsorption. In this work, the hydrogen adsorption reached values of approximately 1.33wt% in PAN-ACHF at 0℃ and 5MPa.