Decomposition of NH3 over Zn–Ti-based desulfurization sorbent promoted with cobalt and nickel

Zn–Ti-based sorbents promoted with cobalt and nickel additive were prepared by simple physical mixing of single oxides. Their capacities for removing H2S and NH3 simultaneously, emitted from coal gasifiers, were investigated in a micro-reactor at 1 atm and 650 °C. NH3 within the fuel gases did not affect the sulfur removing capacity of the Zn–Ti-based sorbent. The additives, cobalt and nickel, were found to be active components in NH3 decomposition as well as H2S absorption, while major components such as ZnO and TiO2 did not show any activity in the NH3 decomposition reaction. NH3 was decomposed over both oxide and sulfide forms of the additives, even though the NH3 decomposition ability of their sulfides dramatically decreased in the presence of H2 gas owing to the equilibrium limitation of NH3 decomposition. In the case of oxide forms, cobalt oxide showed excellent NH3 decomposition capacity regardless of H2 concentrations, while the capacity of nickel oxide depended on the H2 concentrations.