In this study, the changes of physical properties and reactivity of the metal oxide sorbents were investigated under the reducing conditions of coal gas. Metal oxide sorbents are converted into metal sulphides as a result of reaction with H2S in synthesis gas. This could cause the reduced reactivity of sorbents if the metal oxides were converted into metallic elements due to the reduction by either hydrogen or carbon monoxide. In this experiment, the changes of physical properties and reactivity of the metal oxides were investigated over the temperature range 480-700 degrees C. It is confirmed that the reactivity of sulphidation and the reduction of metal oxide increased with increasing temperature. Even though the sulphur capacity of the sorbents in the early stage was high, it reduced rapidly due to the progressive reduction of metal oxides as the sulphidation/regeneration process was repeated. The reduction of metal oxide and the extent of reduction were verified by measuring the amount of oxygen consumed and the amount of SO2 produced during the regeneration of sulphidated sorbents with the aids of a gas analyser. It was concluded that the reactivity of the metal oxide sorbents was influenced by reduction with coal gas at high temperature. (c) 2005 Elsevier Ltd. All rights reserved.