γ-Fe2O3 as the precursor of iron based catalyst prepared by solid-state reaction at room temperature for Fischer-Tropsch to olefins

•Simple solid-sate reaction method is reported for the preparation of FTO catalyst.•γ-Fe2O3 were obtained as the catalyst precursor following the preparation by solid-sate reaction method.•γ-Fe2O3 facilitates the formation of active phase, Fe5C2 with the exposure of (021) facet.•Higher FTO activity and selectivity to lower olefins was achieved.•Solid- sate reaction is a promising pathway to prepare iron based catalysts at room temperature.