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Abstract:

A half century ago, Rosalind Franklin identified two distinct families of organic materials: those that become graphitic during carbonization at high temperatures and those that do not. According to Franklin, sucrose-derived biocarbons showed no trace of homogeneous development of the true graphitic structure, even after heating to 3000 oC [Proc. R. Soc. A 1951, 209, 196-218]. Franklin concluded that non-graphitizing carbons (e.g., sucrose biocarbons) are typically formed from oxygen-rich or hydrogen-poor substances that develop a strong system of cross-linking, which immobilizes the structure and unites the crystallites in a rigid mass. In this work, we show that there is a spectrum of non-graphitizing biocarbons ranging from those that release little CO during carbonization at temperatures approaching 1000 oC to those that strongly and persistently emit CO during carbonization at temperatures approaching 1000 oC. Typically, very low-ash biocarbons are not persistent CO emitters, but biocarbons with moderate ash contents can also be a member of this class if their ash lacks the catalytic species K, P, Mg, and/or Na that appear to be responsible for persistent CO evolution at 1000 oC.

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