•Ce made the shape of magnetite island change from roughly circular to slat-like.•The magnetite pellets of both CLAM and Ce-CLAM specimens had a growth trend from small to large.•Ce enhanced the ...adhesion, continuity and integrity of oxide scale, and delayed the evolution of magnetite.•The mechanism model of Ce effect on the evolution of magnetite and the scale growth model of the two kinds of specimens were proposed.
Lead-cooled fast reactor (LFR) is one of the six types of fourth-generation advanced nuclear reactors, and the corrosion with liquid lead-bismuth eutectic (LBE) to structural materials is regarded as a major obstacle restricting the development of LFR. This study focused on the surface morphology of oxide scale, aiming to illustrate the evolution law of oxide scale and the mechanism of Ce effect on oxide scale. China low activation martensitic (CLAM) and Ce-containing CLAM (Ce-CLAM) specimens generated roughly circular and slat-like magnetite islands respectively, but their magnetite pellets had similar growth trends from small to large sizes. Ce delayed the evolution of magnetite, enhanced the adhesion, continuity and integrity of oxide scale for Ce-CLAM specimen. The mechanism model of Ce effect on the evolution of magnetite and the scale growth model of the two kinds of specimens were proposed.
The hydrogenation properties and the microstructures of TiFe0.9Mn0.1Cex (x = 0, 0.02, 0.04, 0.06) alloys were investigated by PCT, XRD and SEM/EDX. The results showed that the addition of small ...amount of Ce remarkably improved the activation properties of TiFe0.9Mn0.1 alloys. The alloys could start to absorb hydrogen at 353 K under the initial hydrogen pressure of 4.0 MPa without noticeable incubation time. XRD profiles and SEM observation indicated that Ce dispersing in TiFe matrix played an important role for the improvement of activation properties. The addition of Ce didn't affect the thermodynamics and the cycling properties of TiFe0.9Mn0.1 alloy. The degradation of hydrogen capacity after cycles of hydrogenation was recovered by a heat treatment at 623 K.
•Effects of Ce on the hydriding properties of TiFe0.9Mn0.1 alloy were studied.•The added Ce remarkably improved the activation properties of TiFe0.9Mn0.1 alloy.•Ce dispersing in TiFe matrix contributes for improving the activation properties.•The degraded H2 capacity after cycling was recovered by a heat treatment at 623 K.
The evolution of inclusions with Ce addition and Ca treatment in Al-killed steel during RH refining process was investigated through experimental observations and thermodynamic calculations. The ...results indicated that the typical inclusions before Ce addition are CaO–Al2O3 inclusions, which were a liquid state during RH refining. After Ce addition, the typical inclusions was transformed from calcium aluminate inclusion to (Ca–Ce–S–O)+(Ce–Al–Ca–O) complex inclusion. After Ca treatment, the types and morphologies of typical inclusions in steel did not change. Experimental observation and thermodynamic calculations shown that a certain amount of Ca addition can’t affect the formation of Ce-containing inclusion, which may indicate that Ca treatment should not be carried out for rare earth treated steel.
The evolution of inclusions with Ce addition and Ca treatment in Al-killed steel during RH refining process was investigated through experimental observations and thermodynamic calculations. The ...results indicated that the typical inclusions before Ce addition are CaO–Al2O3 inclusions, which were a liquid state during RH refining. After Ce addition, the typical inclusions was transformed from calcium aluminate inclusion to (Ca–Ce–S–O)+(Ce–Al–Ca–O) complex inclusion. After Ca treatment, the types and morphologies of typical inclusions in steel did not change. Experimental observation and thermodynamic calculations shown that a certain amount of Ca addition can't affect the formation of Ce-containing inclusion, which may indicate that Ca treatment should not be carried out for rare earth treated steel.
•Ce-added LaNiO3 showed superior reduction and microwave absorption properties than LaNiO3.•La0.8Ce0.2NiO3 required one-fourth microwave power to achieve 100% CO conversion compared to ...LaNiO3.•Lattice oxygen in LaNiO3 contributed to CO oxidation.•Highly dispersed CeO2 improved the reactivity of LaNiO3 lattice oxygen.
Microwave-assisted catalytic reactions have been investigated for energy-efficient chemical processes. However, catalysts with comparatively high heating properties, activities, and economics have been developed with limited success. In this study, we investigated the catalytic properties of Ce addition to LaNiO3 catalyst, which has high CO oxidation activity and high microwave heating properties. Ce-added catalysts exhibited high heating properties under microwave heating. Increasing the Ce content in the catalyst enhanced the dielectric loss factor, the ability to absorb microwaves and convert them to heat, and improved the microwave heating properties of the catalyst. The catalytic activity toward CO oxidation over Ce-added catalysts decreased in the order of La0.8Ce0.2NiO3 > La0.9Ce0.1NiO3 > LaNiO3 at all oxygen partial pressures when compared to the same microwave power. To clarify the role of Ce addition, temperature programmed reduction (TPR) by H2, CO, and XAFS measurements were performed. TPR results suggested that Ce promotes oxygen mobility and then affects both CO oxidation and microwave heating properties.
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•The enhancement effect of Ce addition on Mn3O4/diatomite desulfurizer is explored.•The strong redox couples are formed between CeO2 and Mn3O4.•The agglomeration of active component ...is restrained by the designed micro reticulated framework.•The mechanism of desulfurization-regeneration of M2C2D6 is systematically elaborated.
To improve the performance of single manganese oxide (MnOx) for moderate-temperature flue gas desulfurization, a series of cerium (Ce) modified Mn3O4/diatomite sorbents with different Ce/Mn molar ratios are prepared by the sol–gel method. Results show that the desulfurization performance of single Mn-based sorbents is significantly enhanced by the addition of CeO2. The strong redox couples are formed between CeO2 and Mn3O4 to further improve the desulfurization activity of sorbents. Moreover, the agglomeration of active component on the surface of carrier is restrained by the designed CeO2-Mn3O4 binary oxides with a micro-reticulated framework to provide more active sites, which is conducive to improving the utilization of active component. The M2C2D6 sorbent is verified as the most outstanding sorbent with the desulfurization efficiency of 96 %, sulfur capacity of 221 mg-SO2/g-sorbent and breakthrough time of 251 min. To master the reaction path and control the types of products, the mechanism of desulfurization-regeneration of M2C2D6 is systematically elaborated by the combination of thermodynamic calculation and product calibration. The above results further prove the effectiveness of Ce doping in the enhancement of desulfurization performance of single Mn-based sorbents for moderate-temperature flue gas desulfurization.
Ce-CLAM specimens were exposed to lead-bismuth eutectic (LBE) for 1500 h under 10−6 wt% oxygen concentration at 500 °C. The continuity and integrity of the oxide scale were better in Ce-CLAM ...specimens than in CLAM specimens, and the parabolic rate constant kp of oxide scale growth was only about 1/2 that of CLAM specimens. Ce-CLAM specimens exhibited better LBE corrosion resistance compared with CLAM specimens, which was mainly attributed to the inhibition function for Fe out-diffusing and the improvement for grain boundaries from Ce. A model was proposed to illustrate the mechanism of Ce-CLAM’s LBE corrosion resistance.
•Ce can improve the LBE corrosion resistance of CLAM specimens.•Ce mainly segregates at grain boundaries, especially triple junctions.•There are less M23C6 precipitates at grain boundaries in Ce-CLAM specimens.•Ce have a hindering effect on the outward diffusion of Fe.•A model is proposed to explain the improving mechanism from Ce.
The catalytic activity and stability of MnOx/TiO2 and MnOx-CeO2/TiO2 catalysts for the oxidative degradation of 1,2-dichorobenzene (o-DCBz) at low temperatures (≤275 °C) were experimentally examined. ...The chlorine (Cl) poisoning mechanism of the catalysts was also clarified based on the catalyst characterization combined with theoretical calculations. Experimental results show that the MnOx/TiO2 catalyst is considerably deactivated during o-DCBz catalytic decomposition, mainly due to the chlorination of the catalytic active component. Ce addition and high temperature can effectively promote the resistance of MnOx/TiO2 catalyst to Cl poisoning. Density functional theory (DFT) calculations in the framework of first-principles reveal that Cl atom prefers to anchor on surface oxygen vacancy (OV) rather than on top site of Mn atom. The adsorption of Cl atom on surface OV hinders the dissociated adsorption of O2 on surface OV and interrupts the regeneration of the surface reactive oxygen species. The adsorption of Cl atom on top site of Mn atom increases the formation energy of surface OV and damages the surface Lewis acid sites which act as the important adsorption sites for o-DCBz molecules. Ce addition causes Cl atom to adsorb preferentially onto the OV around Ce atom, which weakens the interaction between Cl atom and Mn atom. Consequently, the chlorination of the MnOx species is prevented and the oxygen mobility of the catalyst is guaranteed to some extent.
•Chlorination of active component is the main poisoning reason.•Cl atom prefers to anchor on surface OV rather than on the top sites of Mn atom.•Adsorption of Cl atom on catalyst makes the surface OV more difficult to form.•Adsorption of Cl atom weakens the oxygen mobility of the catalyst.•Preferential reaction of CeO2 with Cl atom prevents the chlorination of MnOx.
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•HCl severely poisons the MnOx/TiO2 catalyst towards NH3-SCR of NO.•Surface acid sites and reactive oxygen species are ruined in catalyst chlorination.•Ce addition improves ...Cl-resistance of catalyst by preferentially reacting with HCl.•Cl atom prefers to anchor on the uncoordinated sites of Ce atom.•Competitive effect between o-DCB, NO and NH3 aggravates the catalyst deactivation.
A novel selective catalytic reduction (SCR) catalyst with strong chlorine resistance ability is urgently needed to extend the catalyst life, when SCR technique is applied in plants with high chlorine content (e.g. municipal solid waste and medical waste incinerators). This study investigates the influences of typical chlorine-containing inorganic/organic compounds (i.e. hydrogen chloride (HCl) and o-dichlorobenzene (o-DCBz)) on NH3-SCR of NO over MnOx/TiO2 and MnOx-CeO2/TiO2 catalysts at low temperatures (100−250 °C). The results indicate the presence of HCl severely inhibits the NH3-SCR reaction. On one hand, the reaction between NH3 and HCl causes the deposition of NH4Cl on catalyst surface and reduces the amount of NH3; on the other hand, HCl consumes the surface acid sites which is essential to the adsorption and activation of NH3; moreover, chlorine (Cl) atom prefers to anchor on the uncoordinated metal sites that restrains the regeneration of surface reactive oxygen species and interrupts the redox cycle of catalysts. Ce addition enhances the chlorine resistance property of MnOx-CeO2/TiO2 catalyst by interacting with HCl preferentially. The negative effect of o-DCB on NH3-SCR reaction is more serious than that of HCl below 200 °C. That’s because the competitive effect between o-DCB catalytic oxidation and deNOx via NH3-SCR reaction as well as the accumulation of o-DCB incomplete oxidation byproducts on catalyst surface further aggravates the catalyst deactivation induced by Cl atom.
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