Abstract-The reduction of bulk mixed oxides of zinc and titanium of various compositions and Zn-Ti-0 crystalline phases was studied in a thermogravimetric apparatus in Hz-H,O-N, gas mixtures at 550-1050°C.Comparative reduction experiments with ZnO were also performed. In the absence of water vapor, activation energies of 24 and 37 kcal mol-' were obtained for ZnO and Zn-Ti-0.resnectivelv. The addition of water vapor inhibited reduction and resulted in a change in activation energ; to &I kcal &ol-' for both ZnO and Zn-Ti-0 solids. Similar to H-0, H,S inhibited the initial reduction rate of ZnO and Zn-Ti-0 materials. Based on kinetic experiments, a two-site mode1 is proposed for ZnO reduction. One type of sites is characterized by a rapid reduction rate but is poisoned by water vapor as well as by the presence of titanium atoms in the solid. The other type of sites has a lower reduction rate, is not poisoned by H,O, and is slowly eliminated by the presence of titanium.The efficient removal of H,S from coal-derived gas streams at elevated temperatures is crucial for efficient and economic coal utilization in emerging advanced power generating systems such as the integrated gasification-combined cycle and the gasification-molten carbonate fuel cell. Typically, coal gases contain a mixture of CO, H,, H,O, CO,, N, and CH,. The composition of the gas mixture depends on the type of gasifier used and on the extent of the use of water for quenching. In addition to these gases, minor compounds, most of them undesirable or deleterious, such as H,S and alkali salts, exit the coal gasifier. The relative amounts of these components depend on the type of coal and the type of gasifier used.Previous studies (Jalan and Wu, 1980; Grindley and Steinfeld, 1981; Flytzani-Stephanopoulos et al., 1985) have investigated zinc oxide as a high-temperature, regenerable sulfur sorbent. The thermodynamic equilibrium for ZnO sulfidation is quite favorable, yielding H,S concentrations as low as a few parts per million (ppm) at typical hot gas cleanup temperatures (500-700°C).However, a difficulty with all sorbents containing zinc oxide is some reduction to volatile elemental zinc at temperatures above 600°C. ZnO reduction by H, has been detected at temperatures as low as 160°C (Bonasewicz et al., 1981)