Reaction analysis and global kinetics of partial oxidation of methane using Ni–hydroxyapatite composite catalysts

•Reaction analysis clearly reveals dominant reaction profile at each temperature•Activation energy for POM reaction using Ni-HAp catalyst is determined•Ni metal surface area rather increases after POM reaction when Ni loading is low Reaction analysis and global kinetics of the partial oxidation of methane (POM) were investigated for Ni–hydroxyapatite composite catalysts (Ni–HAp) containing 5- and 20-wt% Ni. The composite particles were prepared using slurry precursor materials. The amount of each gas component at the exit of the reactor was determined on the basis of the change in the gas volume obtained from the total mass balance. As the Ni–HAp catalyst is believed to undergo a direct mechanism of the POM reaction, in the proposed multiple reaction analysis, we assumed the following three independent reactions; direct POM, complete combustion of methane, and a water–gas shift reaction. The extent of these reactions clearly revealed the dominating reaction profile at each temperature. The results indicate that both direct and indirect mechanisms of the POM reaction were followed in parallel even at high temperatures. The activation energy of POM using Ni–HAp catalyst containing 5-wt% Ni was found to be 71.3 kJ/mol. The catalyst were characterized using XRD, BET method, CO pulse method, and TGA. The results of these tests showed the positive effect of changing the Ni loading on the catalyst structure.