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When wood is pyrolysed in absence of air is $\ce{CO2}$ emitted. If yes why is it not combustible?

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    $\begingroup$ Wood contains oxygen on its own. $\endgroup$ – Ivan Neretin Aug 22 '18 at 7:03
  • $\begingroup$ CO$_{2}$ is already oxidized, if that is why you ask. Or, the wood does not have enough oxygen to fully burn it, but what there is (in various forms) is reacted and driven off as gases. $\endgroup$ – Jon Custer Aug 22 '18 at 14:26
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$\ce{CO2}$ is emitted yes. It is not formed in the usual combustion manner however. There a likely two routes to $\ce{CO2}$ formation during wood pyrolysis. Either through the elimination of carboxyl groups e.g., $$\ce{PhCOOH -> Ph + CO2}\text{,}$$ or by a water gas shift reaction: $$\ce{H2O + CO -> CO2 + H2}\text{.}$$ My opinion is that the latter is more likely as there are many more reactions that would liberate $\ce{CO}$ and $\ce{H2O}$ than would yield $\ce{CO2}$.

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