Assessing the potential of nanoporous carbon adsorbents from polyethylene terephthalate (PET) to separate CO2 from ﬂue gas
A.S. Moura1, E. Vilarrasa‑Garcia1, D.A.S. Maia1, M. Bastos‑Neto1 C.O. Ania2,3, J.B. Parra2, D.C.S. Azevedo1 Published online: 7 March 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018
A series of nanoporous carbons was obtained by physical activation of polyethylene terephthalate and investigated for the separation of CO2 from ﬂue gas. The prepared carbons exhibited extremely low functionalization—negligible content in oxygen and other heteroatoms—accompanied by well-developed porous networks consisting of gradually increasing surface areas and micropore volumes. Such features allowed to study the role of nanopore conﬁnement in the separation of carbon dioxide in CO2/N2 gas mixtures. The analysis of the adsorption isotherms of individual gases and their mixtures revealed diﬀerent trends for the CO2 uptake and the selectivity.
Whereas CO2 uptake was larger in the carbons with higher burn-oﬀ degree, the selectivity of CO2 over N2 was favoured in the carbons with a higher fraction of narrow micropores. The diﬀerential adsorption enthalpy curves are typical of highly microporous samples reaching values close to those found in zeolites for low loadings. Data also show that the choice of the best adsorbent for cyclic gas adsorption and separation processes should consider a broad context, taking into account various parameters simultaneously such as gas selectivity, working capacity, adsorption enthalpy and energy consumption in the synthesis of the adsorbent.
The nanotextural characteristics of the activated carbons were evaluated from the high resolution N2 and CO2 adsorption/desorption isotherms at 77 and 273K, respectively, using volumetric analyzers ASAP 2020HD, Micromeritics. The instruments are equipped with a turbo molecular vacuum pump and three pressure transducers (1, 10 and 1000 torr, uncertainty within 0.15% of each reading) to enhance the sensitivity in the low-pressure range. Prior to each experiment, the samples were degassed at 423K under vacuum for 12h.