Perovskite materials of the type Ca x La 1−x Mn 1−y M y O 3−δ (M = Mg, Ti, Fe, or Cu) have been investigated as oxygen carriers for the chemical-looping with oxygen uncoupling (CLOU) process. The oxygen carrier particles were produced by mechanical homogenization of primary solids in a rotary evaporator, followed by extrusion and calcination at 1300°C for 6 h. The chemical-looping characteristics of the substituted perovskites developed in this work were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900−1000°C during alternating reducing and oxidizing conditions. The oxygen carriers showed oxygen releasing behavior (CLOU) in an inert atmosphere between 900 and 1000°C. In addition, their reactivity with methane was high, approaching complete gas yield for all of the materials at 950°C, with the exception being the Cu-doped perovskite, which defluidized during reduction. The rates of oxygen release were also investigated using devolatilized wood char as solid fuel and were found to be similar. The required solids inventory in the fuel reactor for the perovskite oxygen carriers is estimated to be 325 kg/MW th . All of the formulations exhibited high rates of oxidation and a high degree of stability, with no particle fragmentation or agglomeration. The high reactivity and favorable oxygen uncoupling properties make these oxygen carriers promising candidates for the CLOU process.
Oxygen carrier particles consisting of 60 wt % copper, iron, or manganese oxide supported on 40 wt % ceria (CeO 2 ) or gadolinia doped-ceria (Ce 0.9 Gd 0.1 O 1.9 ) have been manufactured and examined as oxygen carrier materials for chemical-looping combustion (CLC). Unlike conventional support materials, such as alumina (Al 2 O 3 ), these ceria-based support materials are active under prevailing conditions in the fuel reactor and have the ability to participate in redox reactions. The oxygen carrier materials were synthesized via extrusion and were examined by successive oxidation and reduction cycles in a bench-scale fluidized bed reactor made of quartz. The experiments were conducted at 900 and 925 °C for copper-based materials, and at 950 °C for iron-and manganese-based materials. Methane or syngas (50% CO and 50% H 2 ) using a flow rate of 900 mL/ min for Cu-based materials and 450 mL/min for Mn-and Fe-based materials was used as the fuel. For all experiments, 15 g of oxygen carrier was used. The oxidation was performed with a gas mixture of 5% O 2 and 95% N 2 . The results show that CeO 2 and Ce 0.9 Gd 0.1 O 1.9 are viable support materials for the oxides of copper and iron. Moreover, the active particles supported on Ce 0.9 Gd 0.1 O 1.9 were more reactive compared to those supported on CeO 2 . CH 4 was completely converted to CO 2 and H 2 O by CuO supported on Ce 0.9 Gd 0.1 O 1.9 , while the conversion of CH 4 for Fe 2 O 3 supported on Ce 0.9 Gd 0.1 O 1.9 was as high as 90%. Ceriasupported Mn 3 O 4 particles showed poor performance when CH 4 was used as fuel. Syngas was fully converted to CO 2 and H 2 O by all the oxygen carriers synthesized and examined in this work. The ability of CuO and Mn 2 O 3 to release O 2 in gas phase when fluidized in inert background was also investigated; in the case of copper oxide, substantial oxygen release was observed. Analysis of fresh and used particles by X-ray diffractometry did not reveal the formation of any unexpected phases. All particles showed good fluidization properties with low attrition and little tendency toward agglomeration.
Different types of metal oxide nanoparticles (NPs) have been suggested for various applications such as water treatment and construction of agricultural pesticides; however, there are concerns about the potential toxicity of these compounds for the nontarget organism especially aquatic organisms. The aims of this study were assessing toxicity and histopathological effects of copper oxide NPs (NPs-CuO) on common carp (Cyprinus carpio) as a model organism. For this purpose 150 common carp with an average weight 7 ± 1 g were exposed to 0, 10, 20, 30, 40, 60, 80, 100, 150, and 200 mg/l of CuO-NPs (10 treatment with three replicates) for 96 hrs. After 24, 48, 72, and 96 hrs exposures, mortality rates recorded and gill samples were collected. Statistical analysis showed significant differences in carp survival between control and treatment groups (p < 0.05); regression between fish mortality rate and NPs-CuO concentration was also revealed (p < 0.01). The LC 96h of NPs-CuO for common carp was estimated as 124.9 mg/l in this study. Various tissue damages were observed in gill of treatments; such as, hypertrophy, hyperplasia, lamellar fusions, erythrocyte infiltration, epithelial lifting; also, there was significant correlation between intensity of tissue lesions and concentration of NPs-CuO (p < 0.01). The findings of the present study demonstrate that sublethal concentration of NPs-CuO can lead to serious tissue lesions. Whats more, concentrations above 30 ml/l of NPs-CuO can lead to some clinical signs; such as skin darkening and death with open mouth as well as definite fish death.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.