Design of Ni-based catalysts for the combined steam and carbon dioxide reforming of methane

Abstract

Synthesis gas with a $H_2/CO$ ratio of 2, which is required for methanol and Fischer-Tropsch synthesis, has been successfully produced by combined steam and carbon dioxide reforming of methane (CSCRM). In addition, Ni-based catalysts have been investigated in combined steam and carbon dioxide reforming of methane (CSCRM). The prepared catalysts were characterized by X-ray diffraction (XRD), BET surface area, $H_2-temperature$ programmed reduction (TPR), and $H_2-chemisorption. The coke formation in the employed catalysts was monitored by SEM$. Various supported Ni catalysts $(Ni/MgO-Al_2O_3, Ni/MgO, Ni/CeO_2, Ni/ZrO_2, and Ni/α-Al_2O_3)$ have been applied for combined steam and carbon dioxide reforming of methane to produce synthesis gas $(H_2/CO = 2)$. $Ni/MgO-Al_2O_3$, a highly active and stable nano-sized catalyst, has been successfully developed for CSCRM. Its high activity and stability is due to the beneficial effects of MgO such as enhanced steam and $CO_2$ adsorption, as well as its basic property, nano-sized NiO crystallite size, and strong interaction between the Ni and support. MgO-promoted $Ni/Al_2O_3$ catalysts have been investigated with respect to catalytic activity and coke formation in CSCRM. $Ni/Al_2O_3$ catalysts were promoted with various MgO content by an incipient wetness method. The catalysts prepared with 20 wt% MgO exhibit the highest catalytic performance and have a high coke resistance in CSCRM. MgO promotion leads to the formation of a $MgAl_2O_4$ spinel phase. This phase is stable at high temperatures and effectively prevents coke formation by increasing steam and $CO2$ adsorption due to an increase in the base strength on the surface of the catalyst. Highly active and stable nano-sized Ni catalysts supported on $MgO-Al_2O_3$ prepared from hydrotalcite-like materials have been designed for CSCRM. $Ni/MgO-Al_2O_3$ exhibits remarkable coke resistance, while $Ni/MgAl_2O_4$, which has been used as a commercial catalyst, shows consi...