Ni-Sr/TiZr for H from methane POM: Sr loading & optimization.

Achieving remarkable H yield with significantly high H/CO over Ni-based catalysts through partial oxidation of methane (POM) is a realistic approach to depleting the concentration of CH and using H and CO as synthetic feedstock. This study examined Ni catalysts on titania-zirconia for methane conversion POM at 600 °C and atmospheric pressure. The addition of strontium to the catalyst was explored to improve its performance. Catalysts were characterized by X-ray diffraction, Raman-infrared-UV-vis spectroscopy, and Temperature-programmed reduction-desorption techniques (TPR, TPD). 2.5 wt% Sr addition induced the formation of the highest concentration of extreme basic sites. Interestingly, over the unpromoted catalyst, active sites are majorly generated by hardly reducible NiO species whereas upon 2.5 wt% promoted Sr promotional addition, most of active sites are derived by easily reducible NiO species. 45% CH conversion and 47% H yield with H/CO = 3.5 were achieved over 2.5 wt% Sr promoted 5Ni/30TiO + ZrO catalyst. These results provide insight into the role of basic sites in enhancing activity through switching indirect pathways over direct pathways for POM. Further process optimization was carried out in the range of 10 000-22 000 SV, 0.35-0.75 O/CH and 600-800 °C reaction temperature over 5Ni2.5Sr/30TiO + ZrO by using central composite design under response surface methodology. The optimum activity as high as ∼88% CH conversion, 86-87% yield of H, and 2.92H/CO were predicted and experimentally validated at 800 °C reaction temperature, 0.35O/CH ratio, and 10 000 space velocity.