PURPOSE: To obtain a gas comprised mainly of hydrogen and carbon monoxide at low cost, by calcining a magnesia adsorbent on which an organic matter has been adsorbed in a nonoxidizing atmosphere.
CONSTITUTION: A magnesia adsorbent on which an org. matter has been adsorbed is calcined in a nonoxidizing atmosphere at 600oC or above, thereby decomposing the organic matter on the surface of the magnesia absorbent. It is preferred that the water content of the magnesia absorbent on which an org. matter has been adsorbed be 30-90 wt%, since the proportion of hydrogen in the pyrolysis gas thus formed can be increased. The magnesia adsorbent which has been calcined can be regenerated to have a sufficient adsorptivity by calcining it at about 400-550oC in an oxidizing atmosphere. The magnesia adsorbent can be prepd. by calcining magnesium hydroxide, magnesium carbonate or the like at 400-700oC for 30 min-several hr according to the form