Carbon Adsorbents from Polycarbonate Pyrolysis Char Residue: Hydrogen and Methane Storage Capacities

The pyrolysis of bisphenol A polycarbonate (PC) can he a solution to chemical recycling of this widely used polymer, which, once it is used, losses its value. The char residue produced in the pyrolysis constitutes more than a quarter of the weight of the PC pyrolyzed and is considered one of the drawbacks of the recycling process. The hypothesis that such char can become a potential good precursor for selective carbon adsorbents, attending to the high carbon content and regular structure of the polymer, is worth considering. Therefore, this work analyses the physical and chemical activation of such char to produce selective high-capacity carbon adsorbents for acting as gas storage solutions. According to an exhaustive textural characterization, the activated carbons prepared are eminently microporous, with a significant volume of narrow micropores, which make them efficient for the adsorption of light energy-carrier gases, such as methane and hydrogen. The methane and hydrogen uptakes measured are in the highest end of those reported for physisorption storage processes and seem to be only related to micropore textural parameters. Surprisingly, a certain amount of very narrow micropores (totally inaccessible to nitrogen molecules at 77 K and showing diffusion restrictions for CO2 adsorption at 273 K hence, very difficult to characterize) arc already present in the char and prove to be effective in hydrogen adsorption.