Abstract
The water-gas shift (WGS) reaction is a well-known industrial process used for the production of hydrogen. During the last few decades, it has attracted renewed attention due to the need for high-purity hydrogen for fuel-cell processing systems. The aim of the present study was to develop a cost-effective and catalytically efficient formulation that combined the advantageous properties of transition metal oxides and gold nanoparticles. Alumina-supported copper- manganese mixed oxides were prepared by wet impregnation. The deposition-precipitation method was used for the synthesis of gold catalysts. The effect of the Cu:Mn molar ratio and the role of Au addition on the WGS reaction’s performance was evaluated. Considerable emphasis was put on the characterization of the as-prepared and WGS-tested samples by means of a number of physicochemical methods (X-ray powder diffraction, high-resolution transmission electron microscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and temperature-programmed reduction) in order to explain the relationship between the structure and the reductive and WGS behavior. Catalytic tests revealed the promotional effect of gold addition. The best performance of the gold-promoted sample with a higher Cu content, i.e., a Cu:Mn molar ratio of 2:1 might be related to the beneficial role of Au on the spinel decomposition and the highly dispersed copper particle formation during the reaction, thus, ensuring the presence of two highly dispersed active metallic phases. High-surface-area alumina that was modified with a surface fraction of Cu–Mn mixed oxides favored the stabilization of finely dispersed gold particles. These new catalytic systems are very promising for practical applications due to their economic viability because the composition mainly includes alumina (80%).
Highlights
The development of energy devices with a high efficiency and environmental friendliness contributes to the future of sustainable energy, improving the quality of life
The effect of the Cu:Mn molar ratio on the water-gas shift (WGS) activity is illustrated in Figure 1a where the temperature dependence of CO conversion over γ-Al2 O3 -supported Cu-Mn mixed oxides with a Cu-to-Mn ratio of 2:1 and 1:5 were compared
Reliable information was provided if the CO conversion resulted only from the WGS reaction and no CO consumption as for example for CO oxidation or CuO reduction occurred
Summary
The development of energy devices with a high efficiency and environmental friendliness contributes to the future of sustainable energy, improving the quality of life. The advancements in fuel-cell processing technology stimulated intensive research of the water-gas shift (WGS) reaction. Catalysts 2018, 8, 563 because of its importance in hydrogen production [1]. This reaction is well known due to its long application as an industrially important process for the CO removal in the syngas, coupled with additional hydrogen generation. In order to avoid the kinetic and thermodynamic constraints, two reactors in series, involving high temperature and low-temperature WGS processes, are employed industrially [2]. Copper is widely used as an active component in commercially applicable WGS catalysts for large-scale hydrogen production due to its activity at low temperatures and its lower cost in comparison to the noble metals. The evaluation of the WGS catalytic behavior of mixed copper-manganese oxides pointed out the promising opportunity for their practical application [3,4,5,6,7,8,9]
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