The Impact of Stoichiometry and Method of Synthesis of Powder Cu–Fe–Al Precursor on Stability and Activity of Ceramometals CuFeAlO/CuFeAl in High Temperature WGSR

Ceramometal catalysts CuFeAlO/CuFeAl, obtained from various powdered Cu–Fe–Al precursors differing in stoichiometry and preparation method, were characterized by physicochemical methods and studied in the water gas shift reaction (CO + H2O ⇌ CO2 + H2). The catalysts are a monolith porous composites, in which metal particles are covered with an oxide shell. The sample Cu : Fe : Al = 45 : 22 : 33, synthesized from powder precursor in two stages was shown to be the most stable. At the first stage the mechanochemical melting of Cu and Fe powders was done. The mechanochemical treatment of obtained product and Al powder was performed at the second stage. This procedure provides the most homogeneous distribution of the components in the precursor. Initial and tested at 400°C ceramometal catalysts were characterized with XRD, SEM and XPS methods. It was revealed that the most active at 350°C catalysts after reductive treatment have Cu1+ and Fe3+ sites. The least active catalysts are completely reduced to Cu0 and partially – to Fe0. It was found that the activity at 330–400°C is determined not only by iron, but also by copper active centers on the surface of the catalysts, or their combined action. Two-stage mechanical activation, apparently, leads to a deeper chemical interaction of the components – Fe and Cu, which provides a higher activity of chromium-free CuFeAl ceramic-metal catalysts.