The transformation of methane into C-2 hydrocarbons over thermally degraded Mg, Pb, Al-hydrotalcite material proceeds with the active participation of beta-PbO. The conditions of pre-treatment leading beta-PbO formation in the catalyst have been examined on the Pb, Al-hydrotalcite material as a model system. By use of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy and diffuse-reflectance spectroscopy techniques, it was found that the temperature interval 600-750 degrees C is optimal for beta-PbO crystallization. On the basis of the present and previous results, the formation of all components of the catalytically active thermally degraded Mg, Pb, Al-hydrotalcite material, has been explained. During calcination of the Mg, Pb, Al-hydrotalcite material, the lead-containing components form beta-PbO and gamma-Al2O3 and the magnesium-containing components transform to a finely dispersed MgO-Al2O3 matrix.