Effect of Stoichiometry and Method of Synthesis of Powdered Cu–Fe–Al Precursors on the Stability and Activity of CuFeAlO/CuFeAl Ceramometals in the High-Temperature Water Gas Shift Reaction

The ceramometal CuFeAlO/CuFeAl catalysts 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 + H 2 O ⇄ CO 2 + H 2 ). The catalysts were a monolith porous composite, in which metal particles were covered with an oxide shell. The sample with the atomic ratio Cu : Fe : Al = 45 : 22 : 33, synthesized from a powder precursor in two stages, was found to be the most stable. At the first stage, the mechanochemical melting of iron and copper powders was carried out, and the resulting product mixed with aluminum powder was mechanochemically treated at the second stage. This procedure made it possible to provide a more uniform distribution of components in the precursor. The ceramometal catalyst samples were studied before and after the reaction performed at 400°C using X-ray diffraction analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. It was found that the catalysts most active at 350°С had reduced Cu 1+ and Fe 3+ sites after treatment in a reducing atmosphere. The least active catalysts were completely reduced to Cu 0 and partially to Fe 0 . It was found that the activity in a temperature range of 330–400°C was determined not only by iron but also by copper active sites on the surface of the catalysts or by their combined action. Two-stage mechanical activation, apparently, led to a deeper chemical interaction of the Fe and Cu components to provide a higher activity of chromium-free CuFeAl ceramic metal catalysts.