The accumulation of coke mainly from CH~4 decomposition on the Ni/Al~2O~3 catalyst surface in partial oxidation of CH~4 to syngas can lead to the catalyst deactivation. In this paper, we used a sequential pulse technique to investigate the reasons of coke formation. Ni~xC from CH~4 decomposition is one of the intermediates for partial oxidation of CH~4, which can be transformed into more inert carbon species under the experimental conditions. The graphitization of carbon from Ni~xC not reacting with surface oxygen in time in partial oxidation of CH~4 is the main reason of coke formation.

Key words: NICKEL, ALUMINIUM OXIDE, METHANE, CATALYST, DECOMPOSITION