Selenium Dioxide （SeO₂） was experimentally observed to be an excellent selective catalyst which helps to remove oxygen from coal matrix and increase atomic H/C ratio at below 600 K(323 ℃). The evolved gas consisted mainly of carbon dioxide at a lower temperature range and the level of deoxygenation was highly enhanced at a higher pressure. The evolved oxygen-containing gases like CO and CO₂ from thermal decomposition of coal in the presence of SeO₂ were resulted from carboxylic and hydroxyl functional groups, whereas carbonyl and etheric functional groups were relatively inert to the cartlyst.