Noncatalytic Hydropyrolysis of Lignin in a Micro-Pyrolyzer

Lignin hydropyrolysis characteristics were investigated in a high-pressure micro-reactor with on-line analysis. The effects of atmosphere, pressure, and temperature on product formation during lignin pyrolysis were quantitatively studied. The formation mechanisms of typical products were proposed and verified with experiments using model compounds. The hydrogen, elevated pressure and temperature promoted the production of condensable vapors and permanent gas while inhibited the formation of char. High-pressure hydrogen boosted the conversion of methoxy phenolics to non-methoxy phenolics, and facilitated the generation of hydrocarbon condensable vapors and hydrocarbon gases. Non-methoxy phenolics were major condensable vapor when the temperature ≥ 500 °C, with a yield of 19.68 C% at 3 MPa and 500 °C. The monocyclic and polycyclic aromatic hydrocarbons and aliphatic hydrocarbons were observed in hydrocarbon condensable vapors. CH 4 was the most abundant gas when the temperature ≥ 500 °C, with a yield of 10.27 C% at 2 MPa and 600 °C. The formation of non-methoxy phenolics, monocyclic aromatic hydrocarbons and aliphatic hydrocarbons is related to the substitution of methoxy (and its methyls) and phenolic hydroxyl groups on benzene rings by alkyls, alkenyls and hydrogen radicals, as well as the hydrogenation of π bonds