Abstract
A sol-gel technique was applied to prepare the two-component oxide system Cu-Mg-O, where MgO plays the role of oxide matrix, and CuO is an active chemical looping component. The prepared samples were characterized by scanning electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction analysis. The reduction behavior of the Cu-Mg-O system was examined in nine consecutive reduction/oxidation cycles. The presence of the MgO matrix was shown to affect the ability of CuO towards reduction and re-oxidation significantly. During the first reduction/oxidation cycle, the main characteristics of the oxide system (particle size, crystallization degree, etc.) undergo noticeable changes. Starting from the third cycle, the system exhibits a stable operation, providing the uptake of similar hydrogen amounts within the same temperature range. Based on the obtained results, the two-component Cu-Mg-O system can be considered as a prospective chemical looping agent.
Highlights
The catalysts based on copper and copper oxide are traditionally attractive for researchers and industrialists mainly due to their high activity in a number of industrially important processes at relatively low temperatures
In the case of dispersed particles, for example, when copper nitrate is supported on alumina, the complete decomposition can occur at even lower temperatures [74]
The second process occurs at lower temperatures if compared with the magnesium hydroxide systems reported in the literature [75,76]
Summary
The catalysts based on copper and copper oxide are traditionally attractive for researchers and industrialists mainly due to their high activity in a number of industrially important processes at relatively low temperatures (about 100–300 ◦C). Coppercontaining systems were intensively studied in the water gas shift reaction [1–8] and steam reforming of methanol and methane [9–12] In these cases, the main advantages of using copper as an active component are its low cost if compared with precious metals, high dispersity of copper species, and their strong interaction with the support that allows tuning the catalytic properties. Copper-based catalysts are highly efficient in the processes of total and partial (selective) oxidation [13–25], hydrogenation [26–29], dehydrogenation of alcohols [30–33], reduction of nitrogen oxides [34,35], etc Such a high activity of the copper-containing systems in the oxidation reactions is stipulated, in many ways, by the high reactive capacity of copper oxide CuO. All this causes the increased attention to CuO as a prospective oxygen carrier for the developed chemical looping technologies, among which the chemical looping combustion processes [36–38] should be mentioned specially
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