TiO2 as textural promoter on high loaded Ni catalysts for methane decomposition

The influence of the preparation method (impregnation and fusion) and calcination temperature (450, 600, 800, and 1000 °C) on the performance of high loaded Ni–TiO2 and Ni–Cu–TiO2 catalysts in the catalytic decomposition of methane at 700 °C has been investigated in a fixed bed reactor. All catalysts tested after a H2 pre-reduction treatment at 550 °C performed well in the process of yielding hydrogen concentrations over 60% without catalyst deactivation at the fixed times used in the reactivity tests. Those catalysts prepared by fusion and those including copper in their composition both show enhanced catalytic activity. The calcination temperature only slightly affects the hydrogen concentration of the outlet gas from the reactor. Characterization of the fresh and used catalysts after the reaction was carried out using different techniques such as powder X-ray diffraction (XRD), temperature programmed reduction (TPR), and scanning electron microscopy (SEM-EDX). In the used catalysts, the deposited carbon appears as long nanofilaments and uniform coatings on catalyst particles, depending on the nickel particle size. The largest Ni particles do not promote the formation of carbon filaments but of uniform coatings, as the catalyst deactivation occurs rapidly.