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Optimal synthesis parameters of YBaCo4O7 had been done. The X-ray diffraction (XRD) results show that YBaCo4O7 samples are all single phase. The Scanning electron microscope (SEM) results indicate that with increasing calcination temperature, calcination time, and decreasing cooling rate, grain transformed from porous agglomerates of sphere or sphere-like to agglomerates of irregular polyhedron, as well as the grain size increased. YBaCo4O7+δ with oxygen storage capacity of 102.52 wt.%, maximum rate of intaking oxygen temperature of 339.7°C, and maximum rate of releasing oxygen temperature of 369.8°C can be obtained by the optimal synthesis parameters, calcination temperature of 1100°C, calcination time of 30 h, air-cooling, and solid-state reaction method. [ABSTRACT FROM AUTHOR]

Chemical looping air separation (CLAS) is a novel technology to separate oxygen from air. In CLAS process, oxygen carrier releases oxygen in steam atmosphere and the reduced oxygen carrier is regenerated in air atmosphere. The performance of oxygen carrier is essential to CLAS technology. In this study, the feasibility of CuO in steam atmosphere was evaluated by thermodynamics. Steam is not involved in any reaction. The production of oxygen is achieved by the decomposition of CuO to Cu 2 O and the optional reduction temperatures should be 850–1050 °C. In order to inhibit the agglomeration of copper oxides, oxygen carriers were prepared with 60 wt.% SiO 2 , TiO 2 , ZrO 2 and MgAl 2 O 4 as support materials. The oxygen release and absorb rates of the four oxygen carriers were determined under reduction temperatures of 950, 975 and 1000 °C and oxidation temperatures of 800, 850, 900 °C in a fixed-bed reactor. Both the reduction and oxidation include quick and slow reaction stages. The reduction rate increases and the oxidation rate decreases with the investigated temperature increasing. The reduction and oxidation macro-kinetic models of the four oxygen carriers were established based on the reactivity data. Binders have great effect on reduction kinetic parameters. The Cu4Mg6 oxygen carrier has the highest reduction and oxidation rates. The stability of Cu4Mg6 was investigated by multi-cycles test. The oxygen release and absorb rates keep stable in each cycle. The chemical and physical characteristics of the oxygen carriers prepared and reacted were also measured. The chemical phases are only copper oxides and binder. The surface area becomes larger after cycles. There is no obvious agglomeration observed after multi-cycles test. [ABSTRACT FROM AUTHOR]

Chemical looping with oxygen uncoupling and chemical looping air separation technologies all depend on the redox property of oxygen carrier. The present work investigated the redox properties of Cu/Zr oxygen carrier under different oxygen concentrations by TG technique. The durability and stability of oxygen carrier is also investigated under 1065°C reduction and 800°C oxidation temperatures. For reduction, the starting and ending temperatures and the peaks of DTG curves shift to high values with oxygen concentration increasing. The effect of oxygen concentration on oxidation is little and the regeneration of Cu/Zr oxygen carrier can be achieved in thin oxygen environment. For reduction and oxidation, times for complete conversion decrease with heating rates increasing. Kinetic models were proposed based on the nucleation and nuclei growth model. The reduction mechanism function is: [ABSTRACT FROM AUTHOR]

Chemical looping air separation (CLAS) is based on the chemical looping principle: oxygen carriers release oxygen to carrier gas in a reduction reactor and absorb oxygen from air in an oxidation reactor. High oxygen transport capacity, high reactivity in reduction and oxidation reactions, and resistance to attrition and agglomeration are some of the criteria that feasible oxygen carrier materials should fulfill. Thermodynamic analysis was applied to prove the potential of Co3O4 as oxygen carrier. ZrO2 served as binder to improve the anti-sintering property and reactivity. Kinetic experiments were performed to determine the reaction rate and conversion of the oxygen carrier. Stability and durability of the oxygen carrier were characterized before and after cyclic experiments. The Co/Zr oxygen carrier proved to be a suitable candidate for the CLAS process. [ABSTRACT FROM AUTHOR]

• Technical feasibility of CL-ODHP was proved by experiment. • Three different kinds of oxygen carriers were prepared and comparative studied. • Effect of temperature on reactivity were studied for prepared oxygen carriers. • V-based oxygen carrier is suitable for CL-ODHP. Chemical looping oxidative dehydrogenation of propane (CL-ODHP) is a promising technology for propylene production and offers several advantages over traditional dedicated propylene production processes, particularly a low energy consumption and safety in operation, with their associated economic advantages. In this study, the technical feasibility of employing oxygen carriers based on Ga, Mo and V for CL-ODHP was investigated and compared. The oxygen carriers were prepared by incipient wet impregnation, and their physical and chemical properties, as well as their reactivity performance were determined. Because of the required high temperature during calcination, the morphological properties of Mo-based and V-based oxygen carriers differed from their Al 2 O 3 support, whereas this was not the case for the Ga-based oxygen carrier. All three oxygen carriers show a stable performance during the redox cycle test, the V-based oxygen carrier showed a higher redox ability and oxygen transport capacity (1.78 wt.%) than the Mo- and Ga-based oxygen carriers (0.19 wt.% and 0.012 wt.% resp.). Among the studied oxygen carriers, the V-based oxygen carrier showed better performance in both the ODHP step and the regeneration step, with the highest propane conversion, propylene selectivity and re-oxidation, making the V-based oxygen carrier the most suitable for CL-ODHP. [ABSTRACT FROM AUTHOR]

• The Cu-Mn composite oxygen carrier with relatively low reaction temperature is constructed. • The reactivity and oxygen transport capacity of this oxygen carrier are determined. • The thermodynamic data including Δ G and K p of the redox reaction are obtained. • The redox kinetic models of the Cu-Mn composite oxygen carrier were established. The further development of the chemical-looping air separation (CLAS) technology is hindered by the required high redox temperature. Improving the thermodynamic properties of oxides by elemental composition is an effective way to decrease the reduction temperature of oxygen carrier. In this paper, a Cu-Mn composite oxygen carrier was prepared by the addition of Mn 2 O 3 to CuO, with Cu x Mn 3− x O 4 as the active phase, and the oxygen uncoupling properties of the Cu-Mn/Zr composite oxygen carrier were investigated, focusing on the redox reactivity under different oxygen concentrations of Cu x Mn 3− x O 4 ⇋ Cu x Mn 2− x + O 2 (g). The oxygen transport capacity of this type of oxygen carrier was determined as 0.0463 g O 2 /g oxygen carrier. With an increase in the oxygen concentration (0.001–50%) in the carrier gas, the required oxygen uncoupling temperature increases (625.5–921 °C). Based on relationship between initial reduction temperature and equilibrium oxygen concentration, the following thermodynamic characteristics of the redox reaction were obtained: ΔG = –0.119 T + 150.41 kJ/mol and K p = exp(14.31–18090.8/ T). Compared to a Cu-based oxygen carrier, the reduction temperature is significantly reduced and the equilibrium oxygen concentration at the same reaction temperature is greatly increased. The redox reactivity under different heating rates and reaction temperatures were also investigated, and the results show that both the reduction and oxidation reactions are temperature driven at the considered temperatures. The reduction and oxidation kinetic models were established by the iso -conversional method. When the relative conversion X < 0.5, the reduction of the Cu-Mn oxygen carrier follows a shrinking core model (n = 3), and the oxidation follows a shrinking core model (n = 2). When X ≥ 0.5, the reduction proceeds according to a one-dimensional diffusion model, whereas the oxidation follows a shrinking core model (n = 3). [ABSTRACT FROM AUTHOR]