Phenolic resin aerogels: The significance of inserting an oxidative ring-fusion aromatization step at the early stages of pyrolytic carbonization, and the application of these materials in CO₂ storage and separation
"Phenolic aerogels, prepared via polycondensation of phenolic monomers and formaldehyde, were converted to carbon aerogels at 800 ⁰C/Ar followed by reactive etching under flowing CO2. Previously, it was found that a lower-temperature air-oxidation of polybenzoxazine aerogels was necessary in order to obtain highly porous, isomorphic carbon aerogels with high carbonization yields. Using those findings as the point of departure, phenolic aerogels were oxidized at 240 ⁰C/air prior to carbonization. During that air-oxidation step, phenolic aerogels based on phloroglucinol (1,3,5- trihydroxybenzene) undergo fusion of their aromatic rings, yielding 6-membered heteroaromatic pyryliums with pendant phenoxide ions. The resulting carbon aerogels have higher surface areas than other carbon aerogels not subjected to aromatization. Subsequently, carbon aerogels were studied for their CO2 adsorption capacity at 273 K up to 1 bar, relevant to post-combustion separation of CO2 from N2. Carbon aerogels from phenolic resins were compared to carbon aerogels from Ishida's polybenzoxazine, and from a random copolymer of polyamide, polyurea, and polyimide. The results show that phenolic resin-derived carbons (containing phenoxide) adsorb more CO2 than the latter, which contain N in addition to oxygen. Interestingly, resorcinol-formaldehyde-derived carbon aerogels uptook 14.8 ± 3.9 mmol g-1 CO2, which is much higher than the values reported in the literature for other microporous materials. Opening of closed micropores and enlargement of micropore size, resulted in a multilayer coverage of micropore walls with CO2. The high capacity for CO2 was attributed to an energy-neutral reaction between surface phenoxides and CO2"--Abstract, page iv.
Winiarz, Jeffrey G.
Miller, F. Scott, 1956-
Ph. D. in Chemistry
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Air-oxidation of phenolic resin aerogels: Backbone reorganization, formation of ring-fused pyrylium cations, and the effect on microporous carbons with enhanced surface areas
- Exceptionally high CO2 adsorption at 273 K by microporous carbons from phenolic aerogels: The role of heteroatoms in comparison with carbons from polybenzoxazine and other organic aerogels
xix, 239 pages
© 2018 Hojat Majedi Far, All rights reserved.
Dissertation - Open Access
Electronic OCLC #
Majedi Far, Hojat, "Phenolic resin aerogels: The significance of inserting an oxidative ring-fusion aromatization step at the early stages of pyrolytic carbonization, and the application of these materials in CO₂ storage and separation" (2018). Doctoral Dissertations. 2725.