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This paper explores the effects of concentration of acid activation on the properties of rare earth tailings catalyst. The results show that the denitration activity of rare earth tailings catalyst is enhanced by acid activation. The best denitration activity of catalyst, activated by sulfuric acid of 8 mol/L, is 86%. [ABSTRACT FROM AUTHOR]

The technology of chemical looping air separation, with the characteristics of simple operation, low cost, and low energy consumption, separates oxygen from air with the oxygen carrier. In this work, reaction properties of monolithic oxygen carriers were investigated in a fixed-bed apparatus, with the consideration of the reactor temperature, oxygen concentration, and reaction gas flow. The XRD results showed that active phase, Al2O3, and cordierite cannot react with each other in calcination processing. The SEM results showed that the micromorphology of oxygen carrier was loaded on cordierite honeycomb uniformly with sphere or sphere-like particles. Oxygen carriers show a faster oxygen release rate and a slower oxygen intake rate. With increasing of absorption temperature, oxygen concentration of inlet gas, and desorption temperature, the reaction rate per unit mass increases. With increasing of gas flow rate, the reaction rate per unit mass decreases. The maximum value of the reaction rate per unit mass was obtained by Y0.95Ti0.05BaCo4O7+δ monolith sample. Samples substituted with Dy element showed fine performance of stability, as Dy substitution causes more serious local lattice distortions. [ABSTRACT FROM AUTHOR]

In the previous work, YBaCo4O7 + δ and Y0.2Ti0.05Dy0.75BaCo4O7 + δ monolithic oxygen carriers worked at low temperature, were reported with good reactivity in oxygen absorption and desorption. Oxygen carriers reacted at low temperature can save amount of energy for the chemical looping air separation process. The objective of this work is to explore the detailed effect of new foreign ion K+ on reaction process of oxygen releasing and the reduction kinetics for YBaCo4O7 + δ and Y0.2Ti0.05Dy0.75BaCo4O7 + δ monolithic oxygen carriers in fixed‐bed reactor. The results showed that introducing K+ can improve the reaction rate of oxygen releasing. The process of oxygen releasing can be described by A model with different model exponentials of 2, 3, and 4. Adding K+ promotes reaction of oxygen releasing. The apparent activation energies and pre‐exponential factor of oxygen releasing process range from 23.11 to 29.72 kJ/mol and 12.46 to 29.73 min−1, respectively. The kinetic model of oxygen releasing process of monolithic oxygen carriers is established based on obtained kinetics parameters. The got kinetics parameters could be used for designing of a chemical looping air separation reactor. [ABSTRACT FROM AUTHOR]

Valuable information on adsorption and reaction of NO and NH3 on the rare earth tailings and rare earth tailings/γ-Al2O3 has been provided on the basis of the diffuse reflectance infrared Fourier transform spectroscopy experiments and characterization. The redox ability and acidity of rare earth tailings are enhanced after adding γ-Al2O3. The highest NO conversion achieved at 200 °C is 65% after adding γ-Al2O3, which is increased by 86%. The surface area of rare earth tailings/γ-Al2O3 is 96.3 m2/g. The improvement of NH3-SCR activity is attributed to the increase of the surface acidity, especially Brønsted acid sites. NH3 can be attributed to NH4 + on Brønsted acid sites and coordinated NH3 on Lewis acid sites on the rare earth tailings/γ-Al2O3. Spillover of ammonia species NH4 + between rare earth tailings and γ-Al2O3 exists. These NH4 + species (spillover) are activated to NH3 + and NH2 + on the Brønsted acid sites of rare earth tailings. Spillover of ammonia species NH4 + and activation are extremely significant for NH3-SCR reaction. The NH3-SCR reaction over rare earth tailings/γ-Al2O3 follows by both Eley–Rideal and Langmuir–Hinshelwood mechanisms especially by the Eley–Rideal mechanism. NH3NO and NH2NO are the vital intermediates of the reaction. The obtained results could provide some guidances in the application of catalyst got with rare earth tailings at low cost and application of rare earth tailings. [ABSTRACT FROM AUTHOR]

This paper explores the effects of concentration of acid activation on the properties of rare earth tailings catalyst. The results show that the denitration activity of rare earth tailings catalyst is enhanced by acid activation. The best denitration activity of catalyst, activated by sulfuric acid of 8 mol/L, is 86%. [ABSTRACT FROM AUTHOR]