Hydrogen transfer route and interaction mechanism during co-pyrolysis of Xilinhot lignite and rice husk

In this study, co-pyrolysis of Xilinhot lignite (XL) and rice husk (RH) was carried out in an aluminum retort to investigate potential interaction mechanism by analyzing the product distribution and hydrogen transfer route. Results indicate that co-pyrolysis yields more water and less tar. This may be related to the hydrogen transfer route during co-pyrolysis process. Hydrogen free radicals prefer combining with small molecular free radicals to produce water and gas rather than combining with medium and large molecular free radicals to produce tar and char. The addition of RH induces the polycondensation reactions to form more condensed char, leading to a higher C/H atomic ratio of char. H-1 NMR shows that the tar molecules from co-pyrolysis are with shorter side chains, which may be because that more methoxyl free radicals from RH transfer into tar than individual pyrolysis, which can be confirmed by the higher content of methoxy phenols in co-pyrolysis tar than expected (from GC/MS analysis). Besides, the alkali and alkaline earth metals (AAEMs) in RH intensify not only the second cracking of tar from RH but also that from XL, leading to hydrogen transfer from tar to gas.