Microemulsion based synthesis of Ni/MgO catalyst for dry reforming of methane

Abstract

The dry reforming of methane has been investigated with two sets of catalysts (pure Ni and Ni/MgO) prepared by microemulsion system. In the first section, the influence of various synthesis parameters was studied over the formation of Ni particles such as: water to surfactant ratio, aging time, calcination temperature and Ni metal molar concentration and characterized by XRD and BET analysis. The study suggests that at constant water to surfactant ratio for a particular microemulsion system, the increase of water content leads to the decrease in surface area due to the higher micellar exchange rate favouring the growth of larger particles. The study also exhibits that the favourable parameters for the achievement of higher surface area are the low calcination temperature (450 °C), moderate aging time (2 h) and lower Ni molar concentration (2 M). The addition of MgO support in the microemulsion system leads to a strong increase in surface area from 23.87 to 153.22 m² g⁻¹ indicating the porous nature of MgO and lesser agglomeration of Ni particles. Ni/MgO catalyst exhibited higher methane (49.93%) and carbon dioxide (54.80%) conversion compared to pure Ni particles (18.41% CH₄ and 20.80% CO₂ conversion). Furthermore, the influence of calcination temperature (450 °C, 600 °C, 800 °C) over Ni/MgO catalysts indicates that increase of calcination temperature (from 450 to 800 °C) leads to the decrease in surface area from 153.22 to 34.72 m² g⁻¹ and also exhibits lower stability compared to the catalyst calcined at lower temperature (450 °C). This higher catalytic activity and stability of the catalyst calcined at lower temperature was attributed to the higher accessibility of the Ni nanoparticles, which seems to be difficult in the catalysts calcined at higher temperatures due to the formation of strong NiO–MgO solid solution.