Preparation And Performance Study Of Polyimide-based Activated Carbon

Activated carbons are usually synthesized from carbon enriched biomass, coal, heavy components derived from oil or coal chemical industry. However, these raw materials always contain a lot of ash, which can’t meet the purity requirement of porous carbon materials for their application in the modern medical industry, environmental protection and new energy technology and other related fields. Heat resistant polymers, such as polyimide (PI), are very suitable for the preparation of high quality activated carbon materials with low ash content, due to high carbon yield, easy activation and the absent of inorganic additives during the process.In this thesis, the preparation technology of ultra pure low ash activated carbon is developed by using physical activation technique with PI film as the precursor. First, the effect of activation parameters, including the activation temperature, activation time, and the dosage of activation reagents, on the performance of activated carbon were investigated in detail, the activation parameters were optimized. Second, the cascade activation process has been adopted for the synthesis of activated carbon, and the effect of activation parameters on the performance of activated carbons were investigated, the activation parameters were optimized thereafter. Finally, the pore structure, surface morphology, microstructure and surface chemical properties of obtained activated carbons were characterized by the nitrogen adsorption, X ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FT-IR). And the ethanol/ether steam mixture adsorption performance of the synthesized activated carbon vs commercial activated carbon fibers were investigated by dynamic adsorption method.The results show that:1. The optimized activation temperature and time for the steam activation process are 880 ℃ and 30 min, respectively. The optimized activation temperature, time and flow rate for the CO2 activation process are 900 ℃,3 h and 200 ml/min, respectively. The optimized activation conditions for the steam/CO2 cascade activation process are as follows:steam activation 15 min at 850 ℃ with water carbon ratio of 4, then switch to CO24 h at 880 ℃ with CO2 flow of 200 ml/min.2, The adsorption performance of activated carbon significantly enhanced by steam/CO2 cascade activation. The resulted activated carbon exhibit typical amorphous turbostratic structure with a high BET specific surface area up to 2186 m2/g, a high pore volume of 1.068 cm3/g and a pore size distribution range from 0 to 3nm.3. The obtained activated carbon displays an excellent performance for ethanol/ether mixture adsorption. The saturated adsorption capacity for ethanol and ether were 294 and 320 mg/g, respectively; the breakthrough adsorption capacity for ethanol and ether were 179 and 192 mg/g, respectively; the breakthrough time reaches 111 min, which is 5 times longer than that of the commercial activated carbon fiber.