SOME ASPECTS OF THE MECHANISM OF HIGH-TEMPERATURE OXIDATION OF NICKEL IN SO2

A number of investigations on the mechanism of reaction of nickel with SO2 has been summarized The calculation results of the equilibrium gas composition in homogeneous SO2 + O-2 mixtures are described over wide ranges of temperatures (500-1100 degrees C) and initial gas compositions. The Ni-O-S phase diagram at 540 degrees C has been compared with data on the stability of interaction products under conditions close to equilibrium. The catalytic activity of NiO has been verified to accelerate the attainment of thermodynamic equilibrium in the SO2-O-2-SO3 system. The most effective catalytic activity of NiO occurred at 650-800 degrees C. A monolayer (approximate to 6 Angstrom) of NiSO4 was detected on the scale surface by ESCA. This surface phase is assumed to be formed either as an activated complex on the NiO catalyst or as the locally stable NiSO4 phase. Both assumptions lead to a possible recognition of the sulfate intermediate mechanism.