Comprehensive study of structure model, pyrolysis and liquefaction behaviour of Heidaigou lignite and its liquefied oil

•An integrated study involving structure model, pyrolysis and liquefaction of Heidaigou lignite (HL) and its liquefied oil was carried out to have an in-depth and comprehensive understanding of lignite.•The chemical–structural properties of HL was investigated with molecular structural model constructed using various techniques.•The changes of HL conversion rate and oil yield with time or temperature were studied.•Agreements and consistency exist between HL model, pyrolysis and aromatics in liquefied oil.