Solvent extraction and separation of rare earths (REs: La ~ Lu, plus Y and Sc) by a novel synthesized extractant, (2-ethylhexylamino)methyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP, abbreviated as H₂A₂), were investigated in chloride medium. The favorable separation factors (SFs) between adjacent heavy REs suggested that HEHAMP has a better separation performance than P507. The extracted complex of trivalent REs was determined to be REClH₂A₄ by the slope analysis method. Thermodynamic parameters (ΔH, ΔG, and ΔS) of Lu were calculated as 7.47 kJ mol⁻¹, −6.05 kJ mol⁻¹, and 45.4 J mol⁻¹ K⁻¹ at 298.15 K, respectively, which indicate that the extraction reaction of Lu is an endothermic process. The loading capacity of 30% (v/v) HEHAMP toward Lu(III), Yb(III), and Y(III) was about 15.17 g Lu₂O₃/L, 14.46 g Yb₂O₃/L, and 12.64 g Y₂O₃/L, respectively. HCl is the most efficient stripping acid, and 92% of the loaded Yb(III) can be stripped by one-stage stripping with 2 mol/L HCl.

Selective catalytic reduction of nitrogen oxides with NH₃ (NH₃-SCR) is still the most commonly used control technology for nitrogen oxides emission. Specifically, the application of rare earth materials has become more and more extensive. CeO₂ was widely developed in NH₃-SCR reaction due to its good redox performance, proper surface acidity and abundant resource reserves. Therefore, a large number of papers in the literature have described the research of cerium-based catalysts. This review critically summarized the development of the different components of cerium-based catalysts, and characterized the preparation methods, the catalytic performance and reaction mechanisms of the cerium-based catalysts for NH₃-SCR. The purpose of this review is to highlight: (1) the modification effect of the various metal elements for cerium-based catalysts; (2) various synthesis methods of the cerium-based catalysts; and (3) the physicochemical properties of the various catalysts and clarify their relations to catalytic performances, particularly in the presence of SO₂ and H₂O. Finally, we hope that this work can give timely technical guidance and valuable insights for the applications of NH₃-SCR in the field of NO_x control.

NH₃ selective catalytic reduction (NH₃-SCR) is the most prevalent and effective method for removing nitrogen oxides. Over the past few decades, manganese (Mn)-based catalysts have demonstrated strong catalytic activity and have been extensively studied for low-temperature NH₃-SCR reactions. This paper provides an in-depth introduction to four forms of Mn-based catalysts: single manganese oxide-based catalysts, binary Mn-based metal oxide catalysts, ternary and multivariate Mn-based metal oxide catalysts, and nano-Mn-based catalysts. Advances have been made in enhancing Mn-based catalysts’ redox performance and acidity, increasing the active component’s dispersion, lowering binding energy, enlarging specific surface area, raising the Mn⁴⁺/Mn³⁺ ratio, and enriching surface adsorbed oxygen by optimizing preparation methods, altering the oxidation state of active components, modifying crystal phases, and adjusting morphology and dispersion, along with various metal modifications. The mechanism of low-temperature NH₃-SCR reactions has been elucidated using various characterization techniques. Finally, the research directions and future prospects of Mn-based catalysts for low-temperature NH₃-SCR reactions are discussed, aiming to accelerate the commercial application of new Mn-based catalysts.

Selective catalytic reduction (SCR) stands out as a pivotal method for curbing NO_x emissions from flue gas. The support, crucially, for SCR efficacy, loads and interacts with the active components within the catalyst. The catalysts could be amplified by the denitration performance of the catalyst by enhancements in support pore structure, acidity, and mechanical robustness. These improvements ensure efficient interaction between the support and active materials, thereby optimizing the structure and property of the catalysts. TiO₂ is the most commonly used support of the NH₃-SCR catalyst. The catalyst with TiO₂ support has poor thermal stability and a narrow temperature range, which can be improved. This paper reviews the research progress on the effects of various aspects of TiO₂ support on the NH₃-SCR catalyst’s performance, focusing on the TiO₂ crystal type, TiO₂ crystal surface, different TiO₂ structures, TiO₂ support preparation methods, and the effects of TiO₂-X composite support on the NH₃-SCR catalyst’s performance. The reaction mechanism, denitrification performance, and anti-SO₂/H₂O poisoning performance and mechanism of TiO₂ support with different characteristics were described. At the same time, the development trend of the NH₃-SCR catalyst using TiO₂ as the support is prospected. It is hoped that this work can provide optimization ideas for SCR catalyst research.

Green and short preparation of CeO₂ nanoparticles with large specific surface area from rare earth extraction (CeCl₃) was successfully achieved by spray pyrolysis (SP). In this method, a precursor solution is first prepared by mixing CeCl₃, C₆H₈O, and H₂O in the requisite quantities. Subsequently, the precursor consisting of a mixture of CeO₂ and C was obtained by SP method by using the precursor solution. Finally, the calcination at 500 °C~800 °C in air for two hours to transform the precursor to CeO₂ nanoparticles. Thermodynamic analysis and experimental studies were performed to determine the optimal SP temperature and citric acid amount. The results indicated that the maximum specific surface area (59.72 m²/g) of CeO₂ nanoparticles were obtained when the SP temperature was 650 °C and the molar ratio of citric acid to CeCl₃ was 1.5.