中文   |   English   |   Email Alert
Fig/Tab
Advanced Search
image

The Use of Rare Earths in Catalysts for Selective Catalytic Reduction of NOx

Bolin Zhang , Shengyang Zhang , Shengen Zhang

Progress in Chemistry ›› 2022, Vol. 34 ›› Issue (2) : 301 -318.

PDF
Progress in Chemistry ›› 2022, Vol. 34 ›› Issue (2) : 301-318 DOI: 10.7536/PC210630
research-article
Scan to read & Share
The Use of Rare Earths in Catalysts for Selective Catalytic Reduction of NOx
Author information +
History +
PDF

Abstract

Nitrogen oxides (NOx) can be reduced by technology of selective catalytic reduction (SCR) with NH3, while the spent commercial V2O5/TiO2 catalysts with biotoxicity for SCR technology is recognized as hazardous wastes in China. Rare earths (REEs) possess unique 4f electron orbit ensuring superior performance of oxygen storage and release, which plays a significant role in catalytic reaction. Thus, REEs are the important research subject in SCR catalysts recently and the proposed substitutes for V2O5/TiO2 catalysts. This review mainly summarizes the progress of 12 REEs including Ce, Sm and La in novel SCR catalysts in recent 5 years, and there is seldom study on Sc, Lu, etc. We primarily review the effect of REEs on improving the catalytic activity, N2 selectivity and stability of Mn-, Fe-, V- and other based DeNOx catalysts. The REEs mainly improve the redox behavior via the formation of redox couples with other transition elements and providing more oxygen vacancies. In the aspect of resistance towards SO2, the REEs, such as Ce and Sm, could suppress the oxidation of SO2 to SO3 and attract the poison of SO2 from the main active components, thus improving the resistance towards SO2. We also review the molding and application of REEs-based catalysts. Additionally, the primitive design strategy of SCR catalysts is proposed, and the development prospect of REEs-based catalysts is forecast finally.

Contents

1 Introduction

2 Reaction mechanism and design of catalysts

3 Ce-based SCR catalysts

3.1 Single ceria-based catalysts

3.2 Mn-Ce based catalysts

3.3 Fe-Ce based catalysts

3.4 V-Ce based catalysts

3.5 Other Ce-containing catalysts

4 Sm,La and other REEs in SCR catalysts

4.1 Sm in SCR catalysts

4.2 La in SCR catalysts

4.3 Other REEs in SCR catalysts

5 Molding and application of REEs-based catalysts

6 Conclusion and outlook

Graphical abstract

Keywords

rare earths / deNOx / selective catalytic reduction / redox / surface acidity / reaction mechanism

Cite this article

Download citation ▾
Bolin Zhang, Shengyang Zhang, Shengen Zhang. The Use of Rare Earths in Catalysts for Selective Catalytic Reduction of NOx. Progress in Chemistry, 2022, 34(2): 301-318 DOI:10.7536/PC210630

登录浏览全文

4963

注册一个新账户 忘记密码

1 Introduction

The selective catalytic reduction (SCR) technology with selective catalytic reduction as reductant can achieve ultra-low emission of nitrogen oxides (NOx) in industrial flue gas, and its core is SCR denitrification catalyst[1⇓~3]. The existing commercial V2O5-WO3(MoO3)/TiO2 catalyst has been successfully applied to denitration in thermal power plants, and its working temperature is generally 300-420 ℃.Increasing the content of V2O5 can expand the temperature range to 200-420 ℃, so as to meet the denitration requirements of medium and high temperature flue gas in different industries such as steel, coking, cement, glass and so on[4]. However, V2O5 is a category 2B carcinogen recognized by the World Health Organization, and the waste vanadium (V) titanium catalyst produced in the flue gas denitrification process is classified as hazardous waste in the National Hazardous Waste List (2016) (waste category: HW50, hazardous characteristics: T). The Catalogue of Substitutes for Toxic and Harmful Raw Materials (Products) Encouraged by the State (2016 Edition) encourages the research and development of rare earth elements (REEs) denitrification catalysts such as lanthanum (La), cerium (Ce) and yttrium (Y) to replace the existing V-based denitrification catalysts for industrial denitrification such as power plants and kilns. In 2017, China issued the national standard of Rare Earth Selective Catalytic Reduction (SCR) Denitrification Catalyst (GB/T 34700-2017), which limits the relevant technical indicators and requirements for Rare Earth Denitrification Catalyst. In 2021, the national key research and development plan launched the implementation of the key project of "rare earth new materials", and deployed the common key technology research and development task of "rare earth denitrification catalyst for deep purification of industrial flue gas under complex working conditions and its application", which shows that China attaches great importance to the research and development of new rare earth denitrification catalyst and its urgent need.
Rare earth elements (REEs) are not rare in the earth's crust. The abundance of Ce, Y, neodymium (Nd) and La is even higher than that of common metals such as tungsten (W) and molybdenum (Mo), and the price of REEs is much lower than that of V, the main active component of commercial denitrification catalysts. REEs have unique unfilled 4F and vacant 5d electron orbital structures, and 4F electrons can realize energy level transition in f-f or f-d configurations, so that lattice oxygen is easy to be detached and recaptured.Thereby showing excellent oxygen storage and release capacity, being suitable for being applied to the catalytic field, and being widely applied to various homogeneous or heterogeneous catalytic reactions such as hydrogenation, dehydrogenation, cracking, polymerization, oxidation, reduction, synthesis and the like[5,6]. In the field of industrial flue gas denitrification, REEs can be used as the main active component or important active coagent to improve the denitrification performance of SCR catalyst by exerting its excellent oxygen storage and release capacity and redox performance[7,8]. To sum up, REEs not only have the advantages of relatively cheap economic benefits, but also have excellent catalytic potential, which will have a good application prospect in the field of denitrification catalysts.

2 SCR Reaction Mechanism and Catalyst Design

The NH3-SCR reaction refers to the reduction of a NOx with a NH3 to produce a N2 and a H2O (Formula 1).When O2 is involved, the molar Gibbs free energy of the reaction is lower (Formula 2), and when the NOx is NO2, the reaction can be called a fast SCR reaction (Formula 3)[9,10].
6NO + 4NH3 → 5N 2 + 6H2OΔ G 298 0=-1821 kJ·mol-1
4NO + 4NH3 + O2 → 4N 2 + 6H2OΔ G 298 0=-1651 kJ·mol-1
2NO2 + 4NH3 + O2 → 3N 2 + 6H2OΔ G 298 0=-1412 kJ·mol-1
The target of SCR catalyst is to reduce the activation energy to carry out the reaction at a lower temperature, and to increase the conversion frequency to obtain a higher denitrification efficiency.NO conversion rate, N2 selectivity and stability are the three key indicators. Langmuir-Hinshelwood (L-H) mechanism and Eley-Rideal (E-R) mechanism are widely used to describe the NOx reduction pathway in the study of SCR reaction mechanism, and the reaction pathway of dual-adsorption L-H mechanism is as follows:[11]
NH3(g) → NH 3(ad)
NO(g) → NO(ad)
Me(n+1)+ =O + NO(ad) → Me n+—O—NO
Men+—O—NO + 1/2 O2 → Me n+—O—NO2
Men+—O—NO + NH3(ad) → Me n+—O—NO—NH3 → Me n+—OH + N2 + H2O
Men+—O—NO2 + NH3(ad) → Me n+—O—NO2—NH3 → Me n+—OH + N2O + H2O
Men+—OH + 1/4 O2 → Me (n+1)+ =O + 1/2 H2O
The reaction path described by the single adsorption E-R mechanism is as follows:[11]
NH3(g) → NH 3(ad)
Me(n+1)+ =O + NH3(ad) → Me n+—OH—NH2
Men+—OH—NH2 + NO(g) → Me n+—OH + N2 + H2O
Men+—OH—NH2 + Me(n+1)+ =O → Me n+—OH—NH + Men+—OH
Men+—OH——NH + NO(g) + Me(n+1)+ =O → 2Me n+—OH + N2O
Men+—OH + 1/4 O2 → Me (n+1)+ =O + 1/2 H2O
In that above formula, Me represent a metal element.
Regardless of the reduction path, the primary condition of heterogeneously catalyzed SCR reaction is the adsorption and activation of reductant NH3 on the surface of catalyst, and further redox reaction with adsorbed or gaseous NOx, in which the catalyst acts as a medium for electron transfer in the redox reaction process and may form a variety of intermediate products. Therefore, the active sites of SCR reaction should have good surface acid properties to adsorb reactants such as NH3 and NOx, and the reactants adsorbed on Lewis acid sites and Brønsted acid sites can participate in the SCR reaction, and should have good redox behavior to promote the SCR reaction. This idea was first put forward by Topsøe in the 1990s[12].
As shown in fig. 1, the SCR reaction is carried out on active sites having surface acidity and redox properties, and includes an acidic cycle and a redox cycle process. Whether the active site is a mononuclear site with both surface acidity and redox properties, or a binuclear site coupling the two properties, although there is a lack of in-depth research so far, more scholars agree with the binuclear site model[13,14]. Li et al. Earlier proposed a binuclear site model coupling surface acidity and redox properties, which provided ideas for the design of SCR catalysts[15]. Tang et al., Fudan University, based on the study of monatomic W catalysts supported on Fe2O3, showed that the W-Fe binuclear site was the effective active site for SCR reaction[16].
It can be seen from the formulas (10) and (16) that the participation of O2 can restore the active sites and accelerate the catalytic cycle process, so the oxygen storage and release capacity of the catalyst is very important. It can be seen from the formula (9) and (15) that the excessive oxidation of the reactant NH3 or NO can lead to the formation of N2O, and the direct oxidation of NH3 is also an important way for the formation of N2O (formula 17), which ultimately reduces the selectivity of N2, so the oxidation ability of the catalyst should be adjusted to be moderate in the design[9,17,18].
2NH3 + 2O2 → N 2O + 3H2O Δ G 298 0=-551 kJ·mol-1
Poisoning factors such As H2O, SO2, alkali metals and arsenic (As) in flue gas can lead to catalyst deactivation, so the design of SCR catalyst should further consider strengthening its resistance to potentially harmful components[19,20]. Based on the above analysis, we propose the following design ideas for SCR catalysts: ① Multi-component catalysts are coupled with different characteristics of different components to achieve complementarity; (2) The combination of multivalent oxides and stable oxides, multivalent oxides usually have good redox properties, while stable oxides generally have strong surface acidity, and the combination of the two can regulate the surface acidity and redox properties; (3) that construction of the catalyst realize the high dispersion of similar sites and the close combination of different site.
The application of REEs in denitration catalysts can improve the redox performance by increasing oxygen vacancies and enhancing oxygen storage and release capacity, improve the surface acidity and adsorption characteristics of NH3 and NOx by adjusting the surface charge of the catalysts, and improve the anti-poisoning performance of SO2 by inhibiting the formation of SO3 or transferring the sulfation of active components.

3 Ce-based denitration catalyst

Ce is the cheapest and the most widely studied REEs in denitration catalysts, which can be used as the main active component, and also as the active promoter of Mn, Fe, V and other catalysts[21][22][23,24][25,26].

3.1 Ingle Ce-based catalyst

Good oxygen storage and release ability of CeO2 is one of the important characteristics required by SCR catalyst, but a single CeO2 calcined in air usually has a good oxidation state, so there are few oxygen vacancies, showing poor denitrification activity. Zhang et al. Prepared a single CeO2 catalyst by citric acid sol method, and compared and analyzed the denitration activity after calcination in air and argon atmosphere, indicating that there was oxygen deficiency on the surface of the CeO2-Ar catalyst obtained by calcination in argon.Therefore, the concentration of oxygen vacancies is high, which shows good oxygen storage and release characteristics and adsorption ability for NH3 and NO, thus greatly improving the denitrification activity of CeO2 (Fig. 2)[8]. However, the oxygen vacancy of single CeO2 obtained by this method is not stable, and the activity decreases to a certain extent in repeated tests.
Cong et al. Hydrothermally synthesized a flower-shaped CeO2 catalyst, and further obtained a coral-shaped N-doped CeO2 catalyst after treatment at 900 ℃ in a NH3 reduction atmosphere[27]. The doping of N increases the lattice defects of the CeO2 and also obtains abundant oxygen vacancies,Thus, more than 95% of NO conversion and N2 selectivity ([NO]=[NH3]=500 ppm, [O2]=5 vol%, GHSV=177 000 h-1, and gas flow 500 mL·min-1) were obtained at 275 ~ 400 ℃. Chen et al. Found that the treatment of S-containing organic compounds such as pyridine sulfonic acid can promote the adsorption of reactants, thus improving the activity of CeO2 catalysts, while inhibiting the activity of surface oxygen, thus inhibiting the oxidation of NH3 to form N2O, so as to improve the selectivity of N2[28].
The CeO2 can better exert the SCR activity by means of the carrier. Abid et al. Found that the catalyst of octahedral zeolite supported 20 wt%CeO2 obtained better NO conversion at 300 ~ 550 ℃[29]. Zhong et al. Found that the CeO2 supported by TiO2 showed good denitrification activity, and the activity of TiO2 carrier could be further improved after P doping modification.CeO2 with 20 wt% loading can achieve nearly 100% NO conversion at 200 ° C (200 mg catalyst, [NO]=[NH3]=500 ppm, [O2]=5 vol%, gas flow 200 mL·min-1)[30]. The reaction mechanism study showed that the reaction followed the L-H mechanism below 200 ℃, while the reaction followed the E-R mechanism above 200 ℃. Liu et al. studied the Ti-modified CeO2 catalyst, and both DFT calculations and DRIFTs studies showed that the NOx was reduced by the E-R mechanism on the surface of the CeTiOx catalyst.Ce sites connected to Ti or oxygen vacancies serve as the main active sites, while Ti sites can adsorb SO2 and avoid the influence of SO2 on Ce, thus showing good resistance to SO2 (fig. 3)[31].
Zhang et al. Studied the effect of SO2 on the performance of Ce-TiO2 at different temperatures. The results showed that with the increase of reaction temperature, the amount of ammonium salt deposition on the catalyst surface decreased, while the amount of Ce(SO4)2 formation increased[32]. The formation of Ce(SO4)2 at 180 ℃ significantly affected the performance of the catalyst, while at 240 ℃ and 300 ℃, the Ce(SO4)2 could act as an acidic site to cooperate with the redox performance of the CeO2 to maintain a high NO conversion. Therefore, for the design of CeO2 catalysts, the formation of Ce(SO4)2 should be mainly avoided at low temperatures.
In general, the performance of single CeO2 catalyst is not good, and its denitrification performance can be improved by doping elements to increase lattice defects to obtain abundant oxygen vacancies, or loading on the surface of strong acidic carriers to obtain better adsorption characteristics.

3.2 Mn-Ce based catalyst

MnOx has excellent low-temperature SCR denitrification activity and is the research focus of low-temperature SCR catalyst, but its N2 selectivity is low and its resistance to SO2 is poor, so it still needs further improvement to achieve industrial application[33⇓~35]. Ce-doping is a common method to improve Mn-based catalysts, which can not only improve their resistance to SO2 poisoning, but also improve their N2 selectivity.
Ren et al. supported 6 wt% Mn-Ce (7:3) on biomass char pretreated with nitric acid, in which Mn and Ce played an effective synergistic role, and 99.2% NO conversion (1 G catalyst, [NO]=[NH3]=600 ppm, [O2]=11 vol%, and gas flow 500 mL·min-1) could be obtained at 175 ° C[36]. MnOx plays a major catalytic role, providing acid sites and redox sites for NH3 and NO adsorption, while Ce captures O2 based on its excellent oxygen storage and release ability.O as to provide abundant active oxygen to assist in re-oxidizing the Mn2O3 formed by the MnOx in the catalytic process into MnO2, namely Mn2O3+Ce4++O2-→MnO2+Ce3+, so as to improve the catalytic cycle efficiency.
Li et al. showed that Mn-Ce catalysts supported on different crystal faces of TiO2 had significant differences in denitration performance. The NO conversion rate and N2 selectivity of Mn-Ce/TiO2-NS supported on { 001 } crystal face were significantly higher than those of Mn-Ce/TiO2-NP supported on { 101 } crystal face, indicating that the differences in physical and chemical characteristics of the interaction between different crystal faces of TiO2 and Mn-Ce could affect their catalytic process[37]. Yan et al. prepared a series of Mn-Ce/TiO2 catalysts by sol-gel method, and analyzed the effect of Mn and Ce loading order on their denitration activity. It was found that Mn-Ce were uniformly distributed and closely combined when they were loaded at the same time, which played a better synergistic role in the SCR reaction, so they showed higher denitration activity than the catalysts loaded first and later[38].
Wu et al. Earlier studied the role of Ce in improving the SO2 resistance of Mn/TiO2 catalysts, indicating that the doping of Ce promoted the formation of sulfates mainly in a bulk-like state, and transferred the object of SO2 from MnOx to CeO2.At the same time, it can also promote the decomposition of ammonium sulfate, thus hindering the poisoning effect of SO2 on the MnOx of the main active substances.Xhibits good resistance to SO2 poisoning at 150 deg C ([NO]=[NH3]=800 ppm,[O2]=3 vol%, [SO2]=100 ppm, [H2O]=3 vol%, and GHSV=40 000 h-1)[39]. Fang et al. Obtained good SO2 resistance at 150 ℃ by adding Ce into birnessite-MnO2 (birnessite).The NO conversion decreased from 100% after 2 H only to 95%([NO]=[NH3]=500 ppm, [O2]=5 vol%, [SO2]=250 ppm, [H2O]=10 vol%, and GHSV=30 000 h-1)[40]. As shown in fig. 4, the SO2 is more likely to adsorb at the Ce site with strong basicity, while the Ce3+ transfers electrons to the Mn4+ to form a Mn3+.The oxidation of SO2 by Mn4+ was hindered, thus inhibiting the formation of sulfate, while the adsorbed SO2 could provide new acidic sites to ensure the SCR reaction.
The Mn-Ce composite oxide catalyst synthesized by Chen et al. By hydrothermal method has obtained more than 90% NO conversion at 150 ~ 310 ℃.When 200 ppm SO2 was introduced at 150 ℃, the conversion of nitric oxide increased from 92.6% to 97.8%([NO]=[NH3]=500 ppm.[O2]=3 vol%, [SO2]=200 ppm, [H2O]=5 vol%, and GHSV=52 500 h-1)[41]. The analysis shows that the SO2 at low temperature inhibits the excessive oxidation of NH3 on Mn-Ce catalyst, thus improving the activity at low temperature. However, the effect of SO2 on the redox performance of the catalyst is shown after all. Generally speaking, the effect of SO2 on the improvement of the activity at low temperature is transient, and the difficulty is still to avoid the impact of SO2 on redox performance.
Yan et al. Prepared a one pot method catalyst with mesoporous zeolite (ZSM-5) as shell and Mn-Ce oxide as core by one pot method.The poisoning effect of the H2O and the SO2 on the Mn-Ce active component is effectively hindered through the construction of the core-shell structure (fig. 5), and compared with the MnCeOx/Z5 catalyst in which the Mn-Ce active component is loaded on the surface, the catalyst shows remarkably excellent H2O and SO2 resistance performance[42].
Yan et al. Found that the SO2 had a significant effect on the Mn-Ce/TiO2 prepared by sol-gel method. At 140 ℃, the conversion rate of nitric oxide decreased from 84% to 42% under the action of SO2, and could not be restored by itself[43]. The Mn-Ce/AC catalyst prepared by Yang Liu et al. By impregnation method achieved 87% NO conversion at 120 ℃, and the conversion decreased to 15% after adsorption saturation SO2, and the NO conversion only recovered to 48% after thermal regeneration at 500 ℃. The analysis showed that the formation of Ce2(SO4)3 or Ce(SO4)2 with strong thermal stability was an important reason for the difficulty of regeneration[44].
Table 1 further summarizes the SCR denitration performance of some other Mn-Ce-based catalysts.
The aim of Mn-Ce catalyst design is generally to combine the good surface acidity of Mn component and the excellent redox performance of Ce component, and to realize the improvement of Mn-based catalyst by taking advantage of the good SO2 resistance of Ce component. In terms of catalytic activity, the addition of Ce can enhance the activity of Mn-based catalysts at low temperature and improve the selectivity of N2 at high temperature by forming a redox cycle with Mn. In the aspect of anti-SO2 performance, the conventional method of doping Ce to improve the anti-SO2 performance of Mn-based catalyst, its main role is to transfer the poisoning of SO2 on Mn component to Ce component, but this can only temporarily delay the deactivation of the catalyst, which can be reflected in the short-term laboratory test, but it is far from enough for the 24 000 H service life required for industrial application.

3.3 Fe-Ce based catalyst

FeOx is one of the important research objects of new denitration catalysts because of its low cost, non-toxic and good SCR denitration activity at medium and high temperature, but its low temperature activity and SO2 resistance are poor, and Ce doping modification is one of the commonly used methods[51⇓~53]. He et al. Found that Ce doping can increase the active sites of FeTi catalyst, thus improving its denitrification activity at 175-400 ℃[54]. The CeO2-Fe2O3/TiO2 catalyst prepared by Zhang et al. by sol-gel method has strong oxygen storage capacity. Due to the synergistic effect of Fe-Ce, the surface active oxygen shows good migration ability between Fe and Ce, which makes the catalyst obtain good denitration efficiency[55]. Liu et al. studied the CO-SCR performance of Fe-Ce catalyst, and synthesized a three-dimensional ordered microporous (3DOM) dimension ally ordered microporous catalyst by a template method, which achieved a NO conversion of more than 90% at 200 ~ 700 ℃ (25 mg catalyst, [NO] = 5 vol%, [CO] = 10 vol%)[56]. The synergistic effect of Fe and Ce makes the surface active oxygen concentration high, Fe mainly provides adsorption sites for NOx, while Ce improves the redox performance and promotes the rapid electron transfer by increasing oxygen vacancies. Yang et al. Also found that the CeO2-Fe2O3 catalyst had higher CO-SCR performance[57].
Chitsazi et al. Also studied the synergistic effect between Ce and Fe, indicating that the addition of Ce accelerates the catalytic cycle process through Ce4++Fe2+↔Ce3++Fe3+ redox cycles.The 3FeOx-8CeO2/TiO2 catalyst prepared by impregnation method was made to have higher than 98% NO conversion ([NO]=[NH3]=1000 ppm, [O2]=6 vol%, and GHSV=30 000 h-1) at 230 ~ 350 ℃, but the effect of harmful components such as SO2 on the catalyst performance was not discussed in this paper[24]. Zhang et al. studied the synergistic denitrification and demercuration (multiwalled carbon nanotubes) effect of Fe-Ce composite oxide catalyst supported on multiwalled carbon nanotubes (MWCNTs)[58]. As shown in fig. 6, the addition of Ce improves the oxygen storage and release capacity by increasing the oxygen vacancy of the catalyst, and the captured O2 is converted into active chemisorbed oxygen to participate in the SCR reaction to accelerate the recovery of active sites, thereby improving the catalytic efficiency. The denitration efficiency of the Fe2Ce0.5Ox/MWCNTs reaches 99.1% (1 G catalyst, [NO] = 1000 ppm, [NH3]=1200 ppm, [O2]=6 vol% and gas flow 1000 mL·min-1) at 240 ℃.However, in the case of excessive NH3, the conversion rate of nitric oxide is generally increased, and whether the MWCNTs loading can improve the performance of SO2 is not discussed in this paper.
Zhang et al. prepared CeO2-Fe2O3/Al2O3 catalyst from Baiyunebo rare earth concentrate by microwave hydrothermal method, and found that Ce provided abundant oxygen vacancies for the catalyst to increase the surface chemisorbed oxygen concentration, which showed good redox performance and enabled it to obtain more than 90% NO conversion (0.5 G catalyst, [NO]=[NH3]=500 ppm, [O2]=3 vol% and GHSV=6000 h-1) at 200 ~ 300 ℃[23].
Zhang et al. prepared Ce-Fe-Ox catalyst by hydrothermal synthesis method and obtained 100% NO conversion rate at 250 ~ 450 ℃ after sulfation. The analysis showed that S O 4 2 - could refine the CeO2 grain, and the synergistic effect of Fe-Ce could improve the redox ability of the catalyst, in which Fe3+ and Ce3+ played an important role in the redox process[59]. It is worth mentioning that the catalyst containing S O 4 2 - has excellent resistance to SO2, and the SO2 of 50 ppm has little effect on the NO conversion at 215 ℃ and 300 ℃. Wang et al. Studied the deactivation mechanism of Na and K on FeCeOx composite oxide catalysts prepared by citric acid method. The results showed that both Brønsted and Lewis acid sites were damaged by Na and K, resulting in a significant decrease in surface acidity and redox performance[60]. The comparative analysis shows that K has a greater impact on the FeCeOx.
Similar to the Mn-Ce-based catalyst, the addition of Ce in the catalyst improves the redox performance of the catalyst mainly by increasing oxygen vacancies and improving the oxygen storage and release capacity, thus providing SCR denitrification activity. Compared with MnOx,FeOx, the low temperature activity of the catalyst is relatively poor, and the addition of Ce does not significantly improve the low temperature activity. The results show that the high activity temperature range of Fe-Ce based catalyst is above 200 ℃. Fe component is sensitive to SO2, and it is still difficult to improve its SO2 resistance only by adding CeO2. Pretreatment with sulfate ion should be one of the better ways to improve its SO2 resistance.

3.4 V-Ce based catalyst

The V-based catalyst is a widely used commercial SCR denitration catalyst at present, and its working temperature is high. Generally, the working temperature can be extended to 200 ~ 420 ℃ by increasing the V2O5 content to 2. 0 ~ 5. 0 wt%, but its cost will increase significantly. Doping Ce is one of the common methods to improve V-based catalyst[61⇓~63].
Zhu et al., Institute of Process Research, Chinese Academy of Sciences found that the addition of Ce can better improve the denitration activity of V2O5-WO3/TiO2 catalyst and greatly reduce the amount of V, which has the prospect of reducing the amount of V in the existing V-based catalyst[64]. By combining the low-temperature activity of Mn and the oxygen storage capacity of Ce, Huang et al. modified the V2O5-WO3/TiO2 catalyst with Mn-Ce as a whole, and obtained excellent denitration activity at 180-240 ℃, but at 240 ℃, the H2O and SO2 still had a significant impact on its performance[65].
Gao et al. studied the reaction mechanism of NH3-SCR on VOx/CeO2 catalyst, and the results showed that the weak surface acidity of VOx/CeO2 led to low adsorption and storage capacity of NH3, so the denitrification effect was not good[26]. The mechanism study shows that the synergetic effect of the surface V5+-OH and the adjacent Ce4+-O groups, as well as the formation of Ce3+/Ce4+ redox couples, greatly reduces the oxidative activation of the catalyst for NO, which can effectively improve the activation of NO in the SCR reaction. Therefore, based on the VOx/CeO2, coupling the surface acidity of another component is expected to obtain excellent SCR activity. As shown in fig. 7, the compounding of the VOx/CeO2 and the H-SSZ-13 molecular sieve further couples the surface acidity of H-SSZ-13 and supplements the performance requirement of the catalyst for NH3 adsorption, thereby obtaining good SCR activity.
Yang et al. Found that Ce doping can better improve the denitration efficiency and resistance to H2O and SO2 poisoning of the V2O5-WO3/TiO2 catalyst in the intermediate temperature range of 200 ~ 350 ℃[66]. However, Zhang et al. Found that the effect of Ce doping on improving the denitrification activity of V2O5-MoO3/TiO2 was not good, while the simultaneous doping of Ce and Mn could improve the NO conversion rate, and showed excellent resistance to H2O and SO2 at 275 ℃[67].
Gao et al. prepared V2O5-WO3/CeO2 catalyst by impregnation method with CeO2 as support, and found that both Lewis and Brønsted acid sites on it could participate in the SCR reaction, and the reaction activity of NH3 adsorbed on Lewis acid sites was higher, with a rate constant four times higher than that of N H 4 + on Brønsted acid sites[68]. Wu Xiaomin et al loaded VOx-MnOx on CeO2 carriers with different exposed crystal faces (Fig. 8).It was found that the VOx-MnOx/CeO2-R catalyst supported on the mainly exposed { 110 } facets exhibited more than 95% NO conversion from 220 to 330 ° C (200 mg catalyst, [NO]=[NH3]=500 ppm, [O2]=5 vol%, and GHSV=16 000 h-1),Higher than the CeO2-P supported on exposed { 111 } faces and the CeO2-C supported on exposed { 100 } faces[69]. DRIFTs analysis shows that the surface of VOx-MnOx/CeO2-R is more likely to adsorb NH3 and nitrogen oxides, thus improving the denitrification efficiency.
Vuong et al. Found that the V2O5/Ce1-xTixO2 catalyst showed 100% NO conversion and N2 selectivity at 190 ℃ ([NO]=[NH3]=1000 ppm, [O2]=5 vol% and GHSV=70 000 h-1),Ce, Ti combined to refine the grain size of the support and produce more oxygen vacancies,The fluidity and reducibility of the surface oxygen are improved, the NOx is reduced through a path shown in fig. 9, and after the V5+ is converted into V4+, gaseous O can be adsorbed by oxygen vacancies in the CeTi carrier to be restored to V5+[70].
The above study shows that Ce can extend the denitration activity of V-based catalyst to the medium and low temperature, and show good resistance to SO2, but the V-based catalyst itself has good resistance to SO2, and the mechanism of Ce in improving the resistance to SO2 of V-based catalyst at medium and low temperature needs further study.

3.5 Other Ce-containing catalysts

As an effective active promoter, Ce has also been widely studied in SCR denitration catalysts of Nb, W, Cu, Co and other systems. Ma et al. Found that Ce3+/Ce4+ in Ce-Nb-Ti catalyst can be efficiently converted to each other, showing good redox performance, while Nb2O5 shows good adsorption performance for NOx and NH3, that is, surface acidity[71]. Liu et al. Also found that the Nb2O5-CeO2/TiO2 catalyst coupled the excellent surface acidity of Nb and the good redox performance of Ce, thus obtaining good denitration efficiency[72].
Bian et al. Found that CeO2-WO3/TiO2 catalyst has a very wide working temperature range and excellent resistance to SO2 poisoning, which is expected to replace the existing commercial V2O5-WO3/TiO2 catalyst[73]. He et al. Found that Ce-W formed a redox cycle of Ce4++W5+↔Ce3++W6+, which could promote the SCR reaction[74]. Geng Xinze's research shows that the Ce-W/TiO2 denitration catalyst also has good mercury removal performance[75]. Li et al. of Beijing University of Aeronautics and Astronautics proposed a strategy to reduce the poisoning of active components by As and release the active sites of As poisoning in view of the problem that denitration catalysts are easy to be poisoned by As (Fig. 10)[76]. It was found that the poisoning effect of As on Ce led to the reduction of Lewis acid sites, oxygen vacancies and the formation of oxidation sites in CeO2-WO3 catalyst, and the poisoning effect of As on Ce was transferred by adding Al, which made CeO2-WO3-Al2O3 catalyst show good resistance to As poisoning and excellent N2 selectivity.
Molecular sieve denitration catalyst has good activity at low temperature, but its hydrothermal stability is generally poor[77,78]. Fan et al. Found that Ce modification could greatly improve the hydrothermal stability of SAPO-34 molecular sieve, so that Cu-SAPO-34 catalyst still maintained good activity after steam treatment at 700 ℃[79]. The NbOPO4 supported Cu-Ce composite oxide catalyst developed by Wang et al. Shows good denitration activity and resistance to H2O and SO2[80]. Wang et al. found that the Co-Ce/TiO2 catalyst prepared by sol-gel method had abundant acid sites and surface chemisorbed oxygen, and showed excellent SCR denitrification performance above 350 ℃[81].
Dong et al. Have rich research on rare earth-based catalysts, and prepared CeSi2 catalysts with composite CeO2-SiO2 by co-precipitation method, so that the Ce-based catalysts have the unique properties of SiO2, and the surface has abundant hydroxyl groups, which not only shows strong surface acidity, but also effectively prevents the adsorption of SO2[82]. The Lewis acid sites of CeSi2 are affected by SO2, which can reduce the adsorption capacity of NOx, thus hindering the reduction path of L-H mechanism of NOx. However, SO2 enhanced the adsorption capacity of CeSi2 on NH3, thus promoting the E-R mechanism reduction path of NOx (Fig. 11c). Therefore, the CeSi2 showed good denitration efficiency even under the SO2 condition of 500 ppm (fig. 11A, B).
Dong et al. Also studied the Ce-Zr composite oxide catalyst and found that more Ce3+ and oxygen vacancies were formed on the surface of the C e 0 . 6 Z r 0 . 4 O2 after SO2+O2 treatment.Therefore, the SO2 has little effect on its performance, and it can still maintain good SCR activity[83]. The Ce0.3-Zr-Ti catalyst prepared by Gong et al. using the hydrothermal synthesis method also achieved a NO conversion higher than 80% at 200 – 375 ° C (2 G catalyst, [NO] = 800 ppm, [NH3]=720 ppm, [O2]=3 vol%, gas flow 1120 mL·min-1)[84].
Ce is the most widely studied REEs in denitration catalysts, which mainly uses its excellent oxygen storage and release performance to capture O2 and release active oxygen to participate in the SCR reaction through Ce3+/Ce4+ redox pairs[85].
The concentration of oxygen vacancies can be improved by controlling the preparation process or doping N and other elements to form lattice defects in single CeO2, but in general, the activity of single CeO2 catalyst is difficult to achieve greater improvement, and the oxygen vacancies obtained are unstable, which are gradually oxidized and filled in the use process, resulting in the decline of denitrification activity.
Ce is combined with transition metals such as Mn, Fe, V and the like to form a multi-component catalyst, and the excellent redox performance of Ce and the surface acidity of other transition metals are combined to obtain two necessary characteristics required by the SCR reaction. In addition, Ce doping can inhibit or transfer the poisoning effect of SO2 on the main active components, thus improving the anti-poisoning performance of the catalyst, but this effect should only temporarily alleviate the poisoning of SO2, which is still difficult to meet the long-term service of industrial applications. The promoting effect of the SO2 on the activity of the catalyst is essentially a transient apparent effect, that is, the activity of the catalyst is improved by temporarily increasing the surface acidity, while the redox performance is not improved, on the contrary, it will play an inhibitory role, and the selectivity of N2 can also be improved apparently, which is essentially a decline in catalytic activity. The above studies show that the sulfidation pretreatment of the catalyst can enhance the resistance of the catalyst to SO2, but its mechanism still needs to be further clarified. The above studies have shown that the incorporation of Ce can promote the decomposition of ammonium sulfate[39]. For low-temperature catalysts, the formation of ammonium salts can occur outside the catalyst, so it is of great significance to further explore the mechanism of Ce in inhibiting the conversion of SO2 to SO3 and promoting the decomposition of ammonium salts.

4 Sm, La and other rare earth based catalysts

4.1 Sm-based catalyst

samarium (Sm) plays an important role in the fields of permanent magnet, laser materials and so on, but its price is not very expensive, so there are many studies in the field of denitrification catalysts, among which the research as an additive of modified Mn-based catalysts is the most extensive.
Liu et al. studied the effect of Sm on the performance of Mn/TiO2 catalyst, and showed that Sm could improve the dispersion, specific surface area, Lewis acid sites and Mn4+ concentration of MnOx, and improve its redox performance by increasing the surface active oxygen, so as to promote the reduction of NOx[86]. The doping of Sm can also hinder the oxidation of SO2 to form S O 4 2 - and improve the SO2 resistance of Mn/TiO2. The TiSmMnOx mixed oxide catalyst prepared by Xu et al. Achieved NOx conversion of > 80% and N2 selectivity of > 90% at a low temperature of 60 ~ 225 ℃ (300 mg catalyst,[NO]=[NH3]=500 ppm, [O2]=5 vol%, and GHSV=50 000 h-1),And exhibited good resistance to H2O and SO2 at 100 deg.c (fig. 12)[87].
Gao et al. Also found that the doping of Sm can increase the specific surface area, acid sites and surface chemisorbed oxygen of MnOx-TiO2, but the difference is that the concentration of surface Mn4+ decreases.The prepared Sm-modified MnOx-TiO2 catalyst achieved 100% NO conversion and N2 selectivity (600 mg catalyst, [NO]=[NH3]=500 ppm, [O2]=5 vol%, and gas flow 600 mL·min-1) from 180 to 390 ℃[88]. Since the oxidation ability of the Mn4+ is strong, the formation of the Mn3+ by suppressing the Mn4+ can adjust the catalytic oxidation performance to an appropriate level, thereby improving the N2 selectivity by suppressing the reaction formula (17). Sun et al. Used Sm and Zr co-doping to improve the MnOx-TiO2, and its denitration efficiency and N2 selectivity were improved.Nearly 100% NO conversion and above 95% N2 selectivity ([NO]=[NH3]=500 ppm, [O2]=5 vol%, and GHSV=30 000 h-1) were obtained at 125 – 275 ° C[89]. It is worth mentioning that Sm2+ tend to provide electrons to Mn4+ through Mn4++Sm2+↔Mn3++Sm3+ redox cycles.Thereby suppressing the SO2 adsorbed on the Mn4+ from donating electrons to the Mn4+,That is to say, the oxidation of SO2 is hindered to form sulfate, and finally the catalyst has good resistance to SO2 poisoning. Wang et al. Obtained a BET specific surface area of 214 m2·g-1 using a mesoporous MnCeSmTiOx complex oxide catalyst prepared by a co-precipitation method,It exhibited nearly 100% NO conversion and N2 selectivity ([NO]=[NH3]=500 ppm, [O2]=5 vol%, and GHSV=80 000 h-1) at 140 to 320 ° C[90]. The results show that the synergistic effect of Lewis acid sites and catalytic oxidation sites on MnCeSmTiOx catalyst ensures the reduction of NO by L-H mechanism, while the addition of Sm increases the concentration of oxygen vacancies.Lectron in that reactant are promoted to be transfer to the Mn4+ and the Ce4+ to improve the reaction efficiency,And that oxidation of the SO2 by the Mn4+ and the Ce4+ is inhibit, thereby improving the SO2 resistance (fig. 13).
The MnOx itself has good activity at low temperature, and the doping of Sm and Mn can also form a redox cycle that promotes each other, thus improving the activity at low temperature. Compared with Ce, the above studies show that the doping of Sm has a better effect on improving the low-temperature activity of Mn, and excellent denitrification performance can be obtained at a low temperature of 60 ℃.
Wei et al. Showed that SmFeOx composite oxides had high denitrification activity at 150 ~ 250 ℃, and the activity temperature range could be further broadened by adding Ti[91]. Wang et al. improved Cu-SSZ-13 catalyst by Sm and Ce, which not only enhanced its denitration activity, but also improved its hydrothermal stability[92]. As shown in Fig. 14, the large-sized Sm and Ce ions occupy the ion-exchange sites of the molecular sieve, which can prevent the aggregation of isolated Cu2+ to form CuOx, thereby improving the hydrothermal stability of Cu-SSZ-13 catalyst.
Dong et al. Found that Sm doping can further enhance the oxygen storage and release capacity of CeO2-TiO2 catalysts, thereby promoting the activation of NOx and NH3.And also inhibit that conversion of SO2 adsorbed on the Ce4+ to SO3 based on the redox cycle of the Sm2++Ce4+↔Sm3++Ce3+, thereby improving the SO2 poisoning resistance of the catalyst[93,94]. This study provides an idea for the study of rare earth-based composite oxide catalysts.
The effect of Sm on improving the activity of the catalyst is consistent with that of Ce, that is, to improve the oxygen storage and release capacity of the catalyst and to enhance the redox performance, while the above studies show that Sm can inhibit the conversion of SO2 to SO3, which is an effective way to improve the resistance of the catalyst to SO2 poisoning.

4.2 La-based catalyst

La is also one of the cheapest REEs with stable characteristics, which can promote the dispersion of active components and improve the migration ability of active oxygen in the catalyst, thus improving the performance of the catalyst. Wu Yanxia et al. Found that La doping could improve the denitration activity of V2O5-MoO3/TiO2 catalyst at 80 ~ 200 ℃[95]. Zhang et al. Found that Co-La mixed oxide catalysts had good performance in the oxidation and reduction of NO, but the SO2 had a significant effect on it[96]. Shen Boxiong et al. found that the 6% Mn-La/Ti-PILC with La/Mn molar ratio of 1/12 had the highest denitration activity by using the Mn-based catalyst supported on pillared interlayered clay (PILC) pillared by La-doped Ti[97]. Liu et al. Found that La3+ can promote the redox cycle of Mn4++Cu+↔Mn3++Cu2+, promote the formation of active ion Cu2+, Mn3+ and surface oxygen defects, thus improving the redox performance of catalysts[98].
In general, Ce has a significant role in improving the redox properties, while there are relatively few studies showing that La has a significant role in improving the redox properties, and it is generally necessary to further dope Ce after doping La[99]. Wang et al. Obtained better denitration activity by loading perovskite-type LaMnO3 on hematite by citric acid complexation impregnation method, and further improved its redox performance by Ce doping[100]. Li et al. studied attapulgite (ATP) supported perovskite-type La1-xCexMnO3 catalyst, and showed that the denitration efficiency of LaMnO3/ATP with only La addition was not good, while the La0.9Ce0.1MnO3/ATP effect was greatly improved with the addition of Ce[101]. The above studies show that the effect of single La doping on improving the performance of Mn-based catalyst is not good, and the combination of La and Ce not only plays the role of Ce, but also further assists Ce to improve the redox performance of the catalyst.
Zhu et al. Have done a lot of research on the theory and application of rare earth Ce-based denitrification catalysts.The constructed polytetrafluoroethylene (PTFE) functional-membrane coated Mn-La-Ce-Ni-Ox honeycomb catalyst had 93% NO conversion at 180.d egree. C. (honeycomb catalyst,[NO]=[NH3]=600 ppm, [O2]=6 vol%, [SO2]=300 ppm, [H2O]=10 vol%, and GHSV=5000 h-1),Since the functional film prevents the H2O from being adsorbed on the surface of the catalyst and blocks the formed ammonium salt out of the film, its anti-poisoning performance is improved (fig. 15)[102]. PTFE functional film will be gradually aged at medium and high temperature, but it should be able to play a better role at low temperature.
Zhang et al. obtained excellent H2O resistance and SO2 performance by sulfidation treatment of nanocrystalline Ni-Ce-La composite oxide. Analysis showed that the Brønsted acid sites on the surface increased after sulfidation treatment, and the main Lewis acid sites were still retained[103]. Zhong et al. Found that the Ce4+ and La3+ in Cu-Ce-La/SSZ-13 can effectively assist the migration of Cu2+, so that it has excellent low-temperature denitrification activity, and its denitrification activity and hydrothermal stability are further improved after the ZSM-5 shell is constructed on its surface[104,105].

4.3 Other rare earth based catalysts

REEs such as praseodymium (Pr), Nd, europium (Eu), gadolinium (Ga), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and Yttrium (Y) have been studied in denitration catalysts. Jin et al. Found that doping Pr in CeO2(ZrO2)/TiO2 by impregnation method would form Ce-O-Pr structure, increase the content of Ce3+ and surface acidity, thus improving the denitrification activity of the catalyst[106]. Chao found that the specific surface area, surface chemisorbed oxygen, and Brønsted acid sites of the V2O5-MoO3/TiO2 catalyst could be enhanced by doping the TiO2 support with Pr[107]. Yu et al. Found that Pr-doped MnOx/SAPO-34 had better low-temperature activity than Ce-doped one. Pr could inhibit the formation of ammonium sulfate and transfer the poisoning effect of SO2 on Mn, so that the catalyst had good resistance to SO2 poisoning[108].
Wu et al. Showed that Nd enabled the Mn/TiO2 to achieve high denitration activity at 80 ℃, NO conversion of more than 90% (300 mg catalyst, [NO]=[NH3]=500 ppm, [O2]=5 vol% and 100 mL·min-1 of gas flow) at 100 ~ 260 ℃, and good resistance to SO2[109]. Huang et al. Found that Nd, Ce, Sm, Er and Y could improve the activity of Mn/TiO2 to some extent, and Nd had the best effect[110]. Feng et al. Found that Nd doping could improve the hydrothermal stability of Cu/SAPO-34[111].
Guo et al. Used Eu doping to improve the MnOx catalyst, which increased the Mn4+ and the content of chemisorbed oxygen.The NO conversion at 100 ~ 400 ℃ is higher than that of 90%,N2 and the selectivity is higher than 94% (280 mg catalyst, [NO]=[NH3]=500 ppm, [O2]=5 vol% and GHSV=108 000 h-1).Further study found that Eu could improve the SO2 resistance of Mn/TiO2 catalyst[112]. Liu et al. Found that the SO2 hindered the adsorption of NH3 and NOx on the Mn/TiO2 catalyst.Eu doping can inhibit the formation of ammonium sulfate and make the catalyst maintain a good adsorption capacity for NH3 and NOx[113].
Niu et al. Found that MnOx doped with appropriate amount of Ga can improve Mn4+, chemisorbed oxygen and surface acidity, so that MnGdO catalyst can achieve 100% NO conversion at 120-330 ℃.It has 100% N2 selectivity (300 mg catalyst, [NO]=[NH3]=500 ppm, [O2]=5 vol% and gas flow 120 mL·min-1) at 150 ~ 300 ℃[114]. In addition, the doping of Gd can inhibit the conversion of the MnO2 to the Mn2O3, the chemical property of the MnO2 is stable, and the Mn2O3 is easy to react with acid substances,Therefore, the generation of MnSO4 is inhibited, and the SO2 resistance of the Mn-based catalyst is improved. Guan et al. Found that when the molar ratio of Gd/Mn was 0.3, the Gd-modified GdMn/ZSM-5 catalyst obtained 100% NO conversion at 120-240 ℃ and good resistance to SO2 poisoning ([NO]=[NH3]=800 ppm, [O2]=5 vol% and GHSV=40 000 h-1)[115].
Dy plays an important role in nuclear reaction and luminescent materials, and its price is relatively high, so there is little research on Dy in denitrification catalysts. Gao et al. modified the nanowire MnFeOx catalyst by doping Dy. When the molar ratio of Dy/Mn was 0.3, the surface acidity of the catalyst was improved, the adsorption capacity of NH3 and NO was increased, and the oxidation activation capacity of NH3 and NO was improved due to the increase of Mn4+ and chemisorbed oxygen concentration, thus improving the denitrification efficiency through Fast SCR reaction[116].
Li et al. Found that Ho can improve the low-temperature denitrification performance of Mn-Ce/TiO2[117]. 100% NO conversion ([NO]=[NH3]=800 ppm, [O2]=5 vol%, and GHSV=20 000 h-1) can be obtained at 120 ° C with Ho modified Fe-Mn/TiO2 catalyst by Huang et al.And has good resistance to 15 vol%H2O+400 ppm SO2, but irreversible deactivation can be found under the condition of higher concentration of SO2, and the main reason is the formation of (NH4)2SO4 and MnSO4 on the surface of the catalyst[118,119]. The physical and chemical properties and denitration activity of the deactivated catalyst can be obviously recovered after the catalyst is treated at 350 ℃ for 1 H under the atmosphere of NH3 with a concentration of 5%. Similar experimental results were obtained after the catalyst was further prepared into a honeycomb catalyst[120].
Trovarelli et al. Found that the TiO2-WO3-SiO2 carrier loaded with FeVO4 will change from anatase to rutile at high temperature, resulting in the decrease of catalyst performance. After doping Er into FeVO4, it can not only improve its denitration performance, but also inhibit the crystal transformation of TiO2-WO3-SiO2 carrier and enhance the thermal stability of the catalyst[121]. Kim et al. constructed a TiO2-WO3(10 wt%) supported vanadate C e 1 - x ErxVO4 catalyst, and the analysis showed that with the increase of Er content, the surface electron density of the catalyst decreased, and Lewis acid sites were more easily formed, which improved the adsorption capacity of NOx and NH3[122]. When the molar ratio of Ce/Er is equal to 1, the C e 0 . 5 E r 0 . 5 VO4 exhibits the most moderate redox performance and Lewis acidity strength, enabling it to achieve excellent SCR activity. Jin et al. Found that the doping of Er could further improve the oxygen vacancy concentration and oxygen storage capacity of CeO2(ZrO2)/TiO2 catalysts[123]. Du et al. found that Er modified FeMn/TiO2 could not only improve its denitration activity, but also reduce the competitive adsorption of SO2 and NH3, thus ensuring the reduction of NOx through E-R mechanism and improving the resistance to SO2 (Fig. 16)[124]. The above study shows that Er has a good effect on improving the stability of denitration catalyst.
Tm is the least abundant REEs in the Earth's crust and has been less studied in denitrification catalysts. In 2021, Niu et al. studied the Tm-modified Mn/TiO2 catalyst, and showed that Tm doping could improve the surface acidity, Mn4+ and chemisorbed oxygen concentration, and then showed good adsorption and redox capabilities for both NH3 and NO. Therefore, the reduction of NOx on Tm-Mn/TiO2 catalyst was mainly through the E-R mechanism of double adsorption[125].
Y is the second most abundant REEs in the crust after Ce. Fokema et al studied the CH4-SCR performance of Y2O3 earlier and found that it had a certain denitrification efficiency above 600 ℃[126]. The TiO2 doped with Y by Zhong et al. Has abundant oxygen vacancies and superoxide ions, and the MnOx/Y2O3-TiO2 catalyst loaded with MnOx has achieved good low temperature activity[127]. Damma et al. also modified the TiO2 nanotube carrier with Y, so that the Mn/Y-TiO2 catalyst obtained good thermal stability. Even after the high-temperature treatment at 650 ℃, the surface Mn4+, active oxygen and acid sites were not significantly affected, and good denitration activity was maintained[128].
promethium (Pm) can not be used as denitration catalyst because of its radioactivity, while terbium (Tb), lutetium (Lu), ytterbium (Yb) and scandium (Sc) are all expensive REEs, which are rarely reported in the research of denitration catalyst.

5 Molding and Application of Rare Earth Based Catalyst

The research progress of REEs in denitration catalysts was summarized in the previous paper. In order to realize its industrial application, the rare earth-based denitration catalysts need to be further molded into specific components. The existing vanadium-titanium denitration catalyst is mainly formed in three types of honeycomb type, flat plate type and corrugated plate type. Among them, the honeycomb catalyst with the largest market share is prepared by impregnating active components after integral extrusion molding or carrier extrusion molding.The flat plate catalyst is mainly used to load the pug on the stainless steel mesh by rolling and coating, while the corrugated plate catalyst is mainly used to load the active components on the calendered glass fiber plate by impregnation or spraying.
At present, there are many network reports on the formation and application of rare earth-based catalysts.It mainly includes Shandong Tiancan Environmental Protection Technology Co., Ltd., Yunnan Chihong Resources Comprehensive Utilization Co., Ltd., Jiangsu Ningtian New Material Technology Co., Ltd. and Inner Mongolia Seagate Environmental Protection Technology Ltd.However, there are relatively few literature and patent reports involving specific research details.
As early as 2014, Zhang Yandong of Shandong Tiancan Environmental Protection Technology Co., Ltd. reported the application of rare earth-based honeycomb denitration catalyst in 300 MW coal-fired units. The 18 × 18 hole honeycomb catalyst was arranged in the way of 2 layers of initial installation + 1 layer reserved. The flue gas volume was about 1.3 million Nm3·h-1, the denitration temperature was 340 ℃, the inlet NOx concentration (calculated by NO2) was 450 mg/Nm3, and the designed denitration rate was ≥ 80%[129]. The project runs steadily, and the NOx emission meets the requirements of the national emission standards. Guohua Taicang Power Generation Co., Ltd.Xiao Guozhen reported the application of new non-toxic REE-based denitration catalyst in 630 MW generating units, the flue gas volume was about 4.49 million m3·h-1, the denitration temperature was 378 ℃, the inlet NOx concentration was 350 mg/m3,([SO2]=370 ppmNOx emission standards under 360 MW, 500 MW and 600 MW conditions[130]. However, the specific REEs and their contents involved in the rare earth-based denitration catalyst used are not disclosed in the above cases. The existing honeycomb molding process route of the vanadium-titanium denitration catalyst comprises the steps of blending, aging, pre-extrusion and extrusion molding, wherein the raw materials generally adopt ammonium metavanadate, ammonium tungsten/molybdate, titanium dioxide, glass fiber, carboxymethyl cellulose, polyethylene oxide and the like, and the pH of the pug is adjusted to be weakly alkaline by adding ammonia water and the like. Similar to manganese-based catalysts, the formation of rare earth-based catalysts, such as the use of soluble salts of REEs (such as nitrate), is generally acidic, requiring the addition of excessive ammonia, and the decomposition of nitrate ions during calcination will produce gas, which will easily lead to catalyst cracking. Therefore, it is a better choice to load the rare earth active component after the carrier is formed.
Wu et al. of Hubei Shenwu Thermal Energy Technology Co., Ltd. disclosed a method for preparing a wide-temperature rare earth denitration catalyst, which uses TiO2 as a main carrier, adds active components such as Ce(NO3)3(3~10 part) and yttrium oxide, and obtains a formed catalyst by adding carboxymethyl cellulose, polyethylene oxide, stearic acid, kapok pulp and the like through mixing, kneading, aging, extrusion forming, drying and calcining[131]. Tang et al. also disclosed a method for preparing a rare earth-based medium and low temperature denitration catalyst by mixing, extrusion and other processes, wherein the REEs components comprise 8-20 wt% of CeO2, 0-3 wt% of Pr6O11 and 0-3 wt% of Ho2O3, wherein the Ce precursor is also a soluble salt such as Ce(NO3)3[132]. The method is that same as the preparation proces of the existing vanadium-titanium catalyst, but when the content of Ce(NO3)3 is too high, the catalyst is easy to crack due to gas release in the calcination proces, and NOx generated by the decomposition of nitrate can cause equipment corrosion.
Zhu et al. invented a method for preparing a CeO2-based denitration catalyst using titanium-based or aluminum-based ceramic as a carrier, in which titanium-based or aluminum-based ceramic is used as a first carrier, TiO2-ZrO2 composite sol is coated as a second carrier layer, and then nitrate, sulfate or phosphate of Ce is loaded by an impregnation method[133,134]. This method can avoid the problem of cracking caused by gas escape, but the impregnation method is difficult to break through the load of highly active components. In addition, Zong et al. disclosed a method for preparing a rare earth based flat-plate denitration catalyst, which is characterized in that a solution of tantalum (Ta), Ce and La is added to a TiO2 carrier and stirred, the pH is adjusted by ammonia water, and other additives are added and stirred to obtain a paste material, and then the rare earth based flat-plate denitration catalyst is obtained by coating, drying and calcining[135]. At present, Inner Mongolia Seagate Environmental Protection Technology Co., Ltd. has built a rare earth-based denitrification catalyst production line with an annual output of 50000 m3.

6 Conclusion and prospect

The existing V2O5-WO3(MoO3)/TiO2 catalyst has a narrow working temperature range and is hazardous waste after being scrapped, which has a great environmental risk, so it is urgent to develop a new V-free wide-temperature catalyst to replace the existing V-based catalyst. Because of its unique electronic orbital structure, REEs makes lattice oxygen easy to be separated and recaptured, and shows excellent oxygen storage and release ability, which can play an excellent SCR denitrification activity, and is also a substitute for the existing vanadium-based catalyst encouraged by the state. Redox performance and surface acidity are two important properties to achieve efficient denitrification, and resistance to harmful components such as SO2 is a necessary characteristic to achieve stable denitrification. In this paper, the research status of REEs such as Ce, Sm and La in denitration catalysts is reviewed, which shows that it is difficult to improve the performance of denitration catalysts with single REEs component, and the main role of REEs in denitration catalysts is to cooperate with other transition metals to exert redox performance and enhance the stability of catalysts.
(1) improve oxidation-reduction performance. Doping Ce, Sm and Er can significantly improve the oxygen storage and release capacity of Mn, Fe and V transition metal-based catalysts, capture O2 to form active oxygen and release it to participate in the SCR reaction, and cooperate to form Ren++Me(n+1)+↔Re(n+1)++Men+(Re (REEs) redox cycle, accelerate the catalytic reaction, and to some extent, improve the adsorption performance of NH3 and NOx by reducing the electron density of the catalyst.
(2) Strengthen stability. Ce, Pr and Eu can inhibit the electron transfer from SO2 to Me(n+1)+ based on their strong electron donating ability, that is, they can hinder the oxidation reaction of SO2 to SO3, thus inhibiting the formation of sulfate. At the same time, REEs also have the function of transferring harmful substances such as SO2 to poison the main active components. In addition, Ce, La and Nd can also enhance the hydrothermal stability of molecular sieve catalysts.
Mn-based catalyst is an important object of REEs modification, because MnOx has been recognized as a catalyst with good low-temperature activity. However, after decades of research on Mn-based denitrification catalyst, there are still few successful application cases of Mn-based catalyst. Hubei Siboying Environmental Protection Technology Co., Ltd. was the first to apply Mn-based denitration catalyst in China, but due to the sensitivity of Mn to SO2, the catalyst still uses V and other components. With the promotion of ultra-low emission, the concentration of SO2 in flue gas will gradually decrease, which will provide better and better application conditions for low-temperature catalysts. If REEs can effectively solve the problem of SO2 deactivation of Mn-based catalysts, it will greatly promote the industrial application of Mn-based catalysts.
Based on the analysis of this paper, the research of REEs denitration catalysts should further combine the high activity catalysts such as Mn, Fe and V, couple the advantages of each component in redox performance, surface acidity and anti-poisoning performance, and construct functional films and other characteristic structures to hinder the poisoning of harmful substances.Develop a wide temperature range denitration catalyst with high activity, high N2 selectivity and excellent stability, and further strengthen the formation and application research of REEs denitration catalyst to realize the replacement of existing V-based catalysts or the reduction of V.

References

Publishing order | Descend order by publishing year | Descend order by cited within
[1]

Paolucci C, Khurana I, Parekh A A, Li S C, Shih A J, Li H, di Iorio J R, Albarracin-Caballero J D, Yezerets A, Miller J T, Delgass W N, Ribeiro F H, Schneider W F, Gounder R. Science, 2017, 357(6354): 898.
[2]

Han L P, Cai S X, Gao M, Hasegawa J Y, Wang P L, Zhang J P, Shi L Y, Zhang D S. Chem. Rev., 2019, 119(19): 10916.
[3]

Wang X H, Liu C X, Song C F, Ma D G, Li Z G, Liu Q L. Progress in Chemistry, 2020, 32(12):1917.
[4]

( 王晓晗, 刘彩霞, 宋春风, 马德刚, 李振国, 刘庆岭. 化学进展, 2020, 32(12):1917.
[5]

Shao X Z, Wang H Y, Yuan M L, Yang J, Zhan W C, Wang L, Guo Y, Lu G Z. Rare Met., 2019, 38(4): 292.
[6]

Akah A. J. Rare Earths, 2017, 35(10): 941.
[7]

Wang L Y, Yu X H, Wei Y C, Liu J, Zhao Z. J. Rare Earths, 2021, 39(10): 1151.
[8]

Vargas M A L, Casanova M, Trovarelli A, Busca G. Appl. Catal. B Environ., 2007, 75(3/4): 303.
[9]

Zhang B L, Zhang S G, Liu B. Appl. Surf. Sci., 2020, 529: 147068.
[10]

Zhang S G, Zhang B L, Liu B, Sun S L. RSC Adv., 2017, 7(42): 26226.
[11]

Zhang B, Deng L, Liu B, Luo C, Liebau M, Zhang S, Gläser R. Rare Met., 2021, 41(1): 166.
[12]

Yang S J, Xiong S C, Liao Y, Xiao X, Qi F H, Peng Y, Fu Y W, Shan W P, Li J H. Environ. Sci. Technol., 2014, 48(17): 10354.
[13]

Topsøe N Y. Science, 1994, 265(5176): 1217.
[14]

Nuguid R J G, Ferri D, Marberger A, Nachtegaal M, Kröcher O. ACS Catal., 2019, 9(8): 6814.
[15]

He G Z, Lian Z H, Yu Y B, Yang Y, Liu K, Shi X Y, Yan Z D, Shan W P, He H. Sci. Adv., 2018, 4(11): eaau4637.
[16]

Qu R Y, Gao X, Cen K F, Li J H. Appl. Catal. B Environ., 2013, 142/143: 290.
[17]

Qu W Y, Liu X N, Chen J X, Dong Y Y, Tang X F, Chen Y X. Nat. Commun., 2020, 11: 1532.
[18]

Li X Y, Chen J, Lu C M, Luo G Q, Yao H. Fuel, 2021, 299: 120910.
[19]

Zhang B L, Liebau M, Liu B, Li L, Zhang S G, Gläser R. J. Mater. Sci., 2019, 54(9): 6943.
[20]

Li G, Mao D S, Chao M X, Li G H, Yu J, Guo X M. J. Rare Earths, 2021, 39(7): 805.
[21]

Wang H, Qu Z P, Liu L L, Dong S C, Qiao Y J. J. Hazard. Mater., 2021, 414: 125565.
[22]

Zhou J, Guo R T, Zhang X F, Liu Y Z, Duan C P, Wu G L, Pan W G. Energy Fuels, 2021, 35(4): 2981.
[23]

Geng Y, Shan W P, Liu F D, Yang S J. J. Hazard. Mater., 2021, 405: 124223.
[24]

Zhang K, Wang J J, Guan P F, Li N, Gong Z J, Zhao R, Luo H J, Wu W F. Mater. Res. Bull., 2020, 128: 110871.
[25]

Chitsazi H, Zhang N Q, Li L C, Liu X J, Wu R, He J D, Song L Y, He H. J. Rare Earths, 2021, 39(5): 526.
[26]

Kwon D W, Kim J, Ha H P. Appl. Surf. Sci., 2019, 481: 1503.
[27]

Hu W S, Zou R Z, Dong Y, Zhang S, Song H, Liu S J, Zheng C H, Nova I, Tronconi E, Gao X. J. Catal., 2020, 391: 145.
[28]

Cong Q L, Chen L, Wang X X, Ma H Y, Zhao J K, Li S J, Hou Y, Li W. Chem. Eng. J., 2020, 379: 122302.
[29]

Chen L X, Agrawal V, Tait S L. Catal. Sci. Technol., 2019, 9(8): 1802.
[30]

Abid R, Delahay G, Tounsi H. J. Rare Earths, 2020, 38(3): 250.
[31]

Zeng Y Q, Wang Y N, Hongmanorom P, Wang Z G, Zhang S L, Chen J T, Zhong Q, Kawi S. Chem. Eng. J., 2021, 409: 128242.
[32]

Liu B, Liu J, Xin L, Zhang T, Xu Y B, Jiang F, Liu X H. ACS Catal., 2021, 11(13): 7613.
[33]

Zhang W J, Liu G F, Jiang J, Tan Y C, Wang Q, Gong C H, Shen D K, Wu C F. Chemosphere, 2020, 243: 125419.
[34]

Xu H M, Yan N Q, Qu Z, Liu W, Mei J, Huang W J, Zhao S J. Environ. Sci. Technol., 2017, 51(16): 8879.
[35]

Zhang B L. Doctoral Dissertation of University of Science and Technology Beijing, 2020.
[36]

( 张柏林. 北京科技大学博士论文, 2020.)..
[37]

Zhang B L, Liebau M, Suprun W, Liu B, Zhang S G, Gläser R. Catal. Sci. Technol., 2019, 9(17): 4759.
[38]

Yang J, Su Z H, Ren S, Long H M, Kong M, Jiang L J. J. Energy Inst., 2019, 92(4): 883.
[39]

Li Q, Li X, Li W, Zhong L, Zhang C, Fang Q Y, Chen G. Chem. Eng. J., 2019, 369: 26.
[40]

Yan D J, Yu Y, Xu Y, Huang X M. Chem. Ind. Eng. Prog., 2015, 34(6): 1652.
[41]

( 闫东杰, 玉亚, 徐颖, 黄学敏. 化工进展, 2015, 34(6): 1652.)
[42]

Jin R B, Liu Y, Wang Y, Cen W L, Wu Z B, Wang H Q, Weng X L. Appl. Catal. B Environ., 2014, 148/149: 582.
[43]

Fang X, Liu Y J, Cheng Y, Cen W L. ACS Catal., 2021, 11(7): 4125.
[44]

Chen J Y, Fu P, Lv D F, Chen Y, Fan M L, Wu J L, Meshram A, Mu B, Li X, Xia Q B. Chem. Eng. J., 2021, 407: 127071.
[45]

Yan R, Lin S X, Li Y L, Liu W M, Mi Y Y, Tang C J, Wang L, Wu P, Peng H G. J. Hazard. Mater., 2020, 396: 122592.
[46]

Yan D J, Yu Y, Huang X M, Liu S J, Liu Y H. J. Fuel Chem. Technol., 2016, 44(2): 232.
[47]

( 闫东杰, 玉亚, 黄学敏, 刘树军, 刘颖慧. 燃料化学学报, 2016, 44(2): 232.)
[48]

Yang L, Tan Y, Sheng Z Y, Zhou A Y, Hu Y F, Dan Y X. Journal of Chemical Engineering of Chinese Universities, 2015, 29(6): 1438.
[49]

( 杨柳, 谭月, 盛重义, 周爱奕, 胡宇峰, 单云霞. 高校化学工程学报, 2015, 29(6): 1438.)
[50]

Wu X M, Yu X L, He X Y, Jing G H. J. Phys. Chem. C, 2019, 123(17): 10981.
[51]

Liang Y Z, Wang X T, Zhang Q Y, Luo S F, Zhou Y F. Journal of Fuel Chemistry and Technology, 2020, 48(2):205.
[52]

( 梁彦正, 王学涛, 张乾蔚, 罗绍峰, 周瑜枫. 燃料化学学报, 2020, 48(2):205.)
[53]

Zhang X L, Zhang X C, Hu X R, Wu X P, Fang C, Xiao K S. Environ. Chem., 2021, 40(2): 632.
[54]

( 张先龙, 张新成, 胡晓芮, 吴雪平, 方城, 肖客松. 环境化学, 2021, 40(2): 632.)
[55]

Chu Y H, Gai Z P, Wang T Z, Liu Z, Yao Y, Yin H Q, Guo J X. Advanced Engineering Sciences, 2015, 47(3): 180.
[56]

( 楚英豪, 盖志谱, 王天泽, 刘正, 姚远, 尹华强, 郭家秀. 四川大学学报(工程科学版), 2015, 47(3): 180.)
[57]

Jiang L J, Liu Q C, Ran G J, Kong M, Ren S, Yang J, Li J L. Chem. Eng. J., 2019, 370: 810.
[58]

Yang J, Ren S, Zhang T S, Su Z H, Long H M, Kong M, Yao L. Chem. Eng. J., 2020, 379: 122398.
[59]

Chen L, Wang X X, Cong Q L, Ma H Y, Li S J, Li W. Chem. Eng. J., 2019, 369: 957.
[60]

Ma S B, Zhao X Y, Li Y S, Zhang T R, Yuan F L, Niu X Y, Zhu Y J. Appl. Catal. B Environ., 2019, 248: 226.
[61]

Shu Y, Aikebaier T, Quan X, Chen S, Yu H T. Appl. Catal. B Environ., 2014, 150/151: 630.
[62]

Zhang W S, Shi X Y, Shan Y L, Liu J J, Xu G Y, Du J P, Yan Z D, Yu Y B, He H. Catal. Sci. Technol., 2020, 10(3): 648.
[63]

Zhang G X, Zhou A Q, Fan H Y, Wang J Q, Chi Z H. J. Fuel Chem. Technol., 2015, 43(10): 1267.
[64]

( 张光学, 周安琪, 范海燕, 王进卿, 池作和. 燃料化学学报, 2015, 43(10): 1267.)
[65]

Liu H, Wu Y H, Liu L H, Chu B X, Qin Z Z, Jin G Z, Tong Z F, Dong L H, Li B. Appl. Surf. Sci., 2019, 498: 143780.
[66]

Yang L C, Luo H J, Li B W, Zhang K, Wu W F. Chinese Journal of Rare Metals, 2021, 45(2): 187.
[67]

( 杨利超, 罗慧娟, 李保卫, 张凯, 武文斐. 稀有金属, 2021, 45(2): 187.)
[68]

Ma Y G, Zhang D Y, Sun H M, Wu J F, Liang P, Zhang H W. Ind. Eng. Chem. Res., 2018, 57(9): 3187.
[69]

Zhang X J, Zhang T J, Song Z X, Liu W, Xing Y. Journal of Fuel Chemistry and Technology, 2021: 1.
[70]

( 张学军, 张庭基, 宋忠贤, 刘威, 邢赟. 燃料化学学报, 2021:1.).
[71]

Wang L X, Zhong Z P, Zhu L, Yang H. Chemical Industry and Engineering Progress, 2017, 36(11): 4064.
[72]

( 王丽霞, 仲兆平, 朱林, 杨瀚. 化工进展, 2017, 36(11): 4064.)
[73]

Xu J Q, Chen G R, Guo F, Xie J Q. Chem. Eng. J., 2018, 353: 507.
[74]

Zhang D J, Ma Z R, Wang B D, Sun Q, Xu W Q, Zhu T. J. Rare Earths, 2020, 38(2): 157.
[75]

Li P P, Yu F, Zhu M Y, Tang C J, Dai B, Dong L. Progress in Chemistry, 2016, 28(10): 1578.
[76]

( 李盼盼, 于锋, 朱明远, 汤常金, 代斌, 董林. 化学进展, 2016, 28(10): 1578.)
[77]

Liu X L, Zhao Z W, Ning R L, Qin Y, Zhu T Y, Liu F G. Catal. Lett., 2020, 150(2): 375.
[78]

Huang J, Zhong Z P, Zhu L, Xue J M, Xu Y Y, Wu P T. Chemical Industry and Engineering Progress, 2018, 37(6): 2242.
[79]

( 黄金, 仲兆平, 朱林, 薛建明, 许月阳, 吴培亭. 化工进展, 2018, 37(6): 2242.)
[80]

Yang J, Lin F, Chen K, Kong M, Zhao D, Meng F. Journal of Fuel Chemistry and Technology, 2016, 44(11): 1394.
[81]

( 杨剑, 林凡, 陈奎, 孔明, 赵冬, 孟飞. 燃料化学学报, 2016, 44(11): 1394.)
[82]

Zhang D J, Ma Z R, Wang B D, Zhu T, Weng D, Wu X D, Chen J Y, Wang H Y, Li G, Zhou J L. J. Rare Earths, 2020, 38(7): 725.
[83]

Hu W S, Zou R Z, Dong Y, Xin Q, Zheng C H, Gao X. Journal of Engineering Thermophysics, 2021, 42(1): 239.
[84]

( 胡文硕, 邹任智, 董毅, 辛琦, 郑成航, 高翔. 工程热物理学报, 2021, 42(1): 239.)
[85]

Wu X M, Ni K W, Yu X L, Zhao N. J. Fuel Chem. Technol., 2020, 48(2): 179.
[86]

( 吴孝敏, 倪凯文, 宇小龙, 赵宁. 燃料化学学报, 2020, 48(2): 179.)
[87]

Vuong T H, Radnik J, Rabeah J, Bentrup U, Schneider M, Atia H, Armbruster U, Grünert W, Brückner A. ACS Catal., 2017, 7(3): 1693.
[88]

Ma S Y, Gao W Q, Yang Z D, Lin R Y, Wang X W, Zhu X B, Jiang Y. J. Energy Inst., 2021, 94: 73.
[89]

Liu S S, Wang H, Zhang R D, Wei Y. Mol. Catal., 2019, 478: 110563.
[90]

Bian X, Xiao K Y, Wang S H, Qiu B L. Chinese Journal of Rare Metals, 2020, 44(9): 974.
[91]

( 边雪, 肖坤宇, 王书豪, 邱保龙. 稀有金属, 2020, 44(9): 974.)
[92]

He J F, Xiong Z B, Du Y P, Lu W, Tian S L. J. Energy Inst., 2021, 94: 85.
[93]

Geng X Z, Duan Y F, Hu P, Liu S, Liang C. China Environ. Sci., 2019, 39(4): 1419.
[94]

( 耿新泽, 段钰锋, 胡鹏, 柳帅, 梁财. 中国环境科学, 2019, 39(4): 1419.)
[95]

Jiang S, Li T, Zheng J K, Zhang H, Li X, Zhu T L. Environ. Sci. Technol., 2020, 54(22): 14740.
[96]

Yan Z P, Chong M B, Cheng D G, Chen F Q, Zhan X L. Prog. Chem., 2008, 20(S2): 1037).
[97]

( 颜志鹏, 崇明本, 程党国, 陈丰秋, 詹晓力. 化学进展, 2008, 20(S2): 1037.).
[98]

Han M J, Jiao Y L, Zhou C H, Guo Y L, Guo Y, Lu G Z, Wang L, Zhan W C. Rare Met., 2019, 38(3): 210.
[99]

Fan J, Ning P, Wang Y C, Song Z X, Liu X, Wang H M, Wang J, Wang L Y, Zhang Q L. Chem. Eng. J., 2019, 369: 908.
[100]

Wang X Q, Liu Y, Wu Z B. Chem. Eng. J., 2020, 382: 122941.
[101]

Wang S Q, Li J M, Du Z H. Environmental Pollution & Control, 2021, 43(4): 475.
[102]

( 王淑勤, 李金梦, 杜志辉. 环境污染与防治, 2021, 43(4): 475.)
[103]

Tan W, Liu A N, Xie S H, Yan Y, Shaw T E, Pu Y, Guo K, Li L L, Yu S H, Gao F, Liu F D, Dong L. Environ. Sci. Technol., 2021, 55(6): 4017.
[104]

Tan W, Wang J M, Li L L, Liu A N, Song G, Guo K, Luo Y D, Liu F D, Gao F, Dong L. J. Hazard. Mater., 2020, 388: 121729.
[105]

Gong P J, Xie J L, He F, Li F X, Qi K. Appl. Surf. Sci., 2020, 505: 144641.
[106]

Li P, Chen X Y, Li Y D, Schwank J W. Catal. Today, 2019, 327: 90.
[107]

Liu L J, Xu K, Su S, He L M, Qing M X, Chi H Y, Liu T, Hu S, Wang Y, Xiang J. Appl. Catal. A Gen., 2020, 592: 117413.
[108]

Xu Q, Fang Z L, Chen Y Y, Guo Y L, Guo Y, Wang L, Wang Y S, Zhang J S, Zhan W C. Environ. Sci. Technol., 2020, 54(4): 2530.
[109]

Gao C, Shi J W, Fan Z Y, Wang B R, Wang Y, He C, Wang X B, Li J, Niu C M. Appl. Catal. A Gen., 2018, 564: 102.
[110]

Sun C Z, Liu H, Chen W, Chen D Z, Yu S H, Liu A N, Dong L, Feng S. Chem. Eng. J., 2018, 347: 27.
[111]

Wang B, Wang M X, Han L N, Hou Y Q, Bao W R, Zhang C M, Feng G, Chang L P, Huang Z G, Wang J C. ACS Catal., 2020, 10(16): 9034.
[112]

Wei Y, Fan H, Wang R. Appl Surf Sci, 2018, 459:63.
[113]

Wang Y J, Shi X Y, Shan Y L, Du J P, Liu K, He H. Ind. Eng. Chem. Res., 2020, 59(14): 6416.
[114]

Liu H, Fan Z X, Sun C Z, Yu S H, Feng S, Chen W, Chen D Z, Tang C J, Gao F, Dong L. Appl. Catal. B Environ., 2019, 244: 671.
[115]

Liu H, Sun C Z, Fan Z X, Jia X X, Sun J F, Gao F, Tang C J, Dong L. Catal. Sci. Technol., 2019, 9(13): 3554.
[116]

Wu Y X, Liang H L, Chen X, Chen C, Wang X Z, Dai Z Y, Hu L M, Chen Y F. Materials Reports, 2021, 35(6): 6020.
[117]

( 吴彦霞, 梁海龙, 陈鑫, 陈琛, 王献忠, 戴长友, 胡利明, 陈玉峰. 材料导报, 2021, 35(6): 6020.)
[118]

Zhang T J, Li J, He H, Song Q Q, Liang Q M. Front. Environ. Sci. Eng., 2017, 11(2): 1.
[119]

Shen B X, Ma J, Hu G L, Sun X, Li D Q. Journal of Fuel Chemistry and Technology, 2012, 40(11): 1372.
[120]

( 沈伯雄, 马娟, 胡国丽, 孙喜, 李冬倩. 燃料化学学报, 2012, 40(11): 1372.)
[121]

Liu T K, Wei L Q, Yao Y Y, Dong L H, Li B. Appl. Surf. Sci., 2021, 546: 148971.
[122]

Lao Y J, Jiang X X, Huang J, Zhang Z, Wang X Y. Rare Met., 2021, 40(3): 547.
[123]

Wang R, Gui K T, Liang H. Journal of Southeast University (Natural Science Edition), 2016, 46(6): 1234.
[124]

( 王瑞, 归柯庭, 梁辉. 东南大学学报(自然科学版), 2016, 46(6): 1234.)
[125]

Li X Z, Yin Y, Yao C, Zuo S X, Lu X W, Luo S P, Ni C Y. Particuology, 2016, 26: 66.
[126]

Yang B, Shen Y S, Su Y, Li P W, Zeng Y W, Shen S B, Zhu S M. Catal. Commun., 2017, 94: 47.
[127]

Zhang L, Qu H X, Du T Y, Ma W H, Zhong Q. Chem. Eng. J., 2016, 296: 122.
[128]

Chen Z Q, Guo L, Qu H X, Liu L, Xie H F, Zhong Q. Chem. Commun., 2020, 56(15): 2360.
[129]

Chen Z Q, Liu L, Qu H X, Zhou B J, Xie H F, Zhong Q. J. Catal., 2020, 392: 217.
[130]

Jin Q J, Shen Y S, Zhu S M, Liu Q, Li X H, Yan W. J. Rare Earths, 2016, 34(11): 1111.
[131]

Chao J D, He H, Song L Y, Fang Y J, Liang Q M, Zhang G Z, Qiu W G, Zhang R. Chemical Journal of Chinese Universities, 2015, 36(3): 523.
[132]

( 晁晶迪, 何洪, 宋丽云, 房玉娇, 梁全明, 张桂臻, 邱文革, 张然. 高等学校化学学报, 2015, 36(3): 523.)
[133]

Yu C L, Huang B C, Dong L F, Chen F, Yang Y, Fan Y M, Yang Y X, Liu X Q, Wang X N. Chem. Eng. J., 2017, 316: 1059.
[134]

Wu P, Zhang Y P, Zhuang K, Shen K, Wang S, Huang T J. J. Rare Earths, 2020, 38(11): 1215.
[135]

Huang J, Huang H, Jiang H T, Liu L C. Catal. Today, 2019, 332: 49.
[136]

Feng X, Lin Q J, Cao Y, Zhang H L, Li Y S, Xu H D, Lin C L, Chen Y Q. J. Taiwan Inst. Chem. Eng., 2017, 80: 805.
[137]

Sun P, Guo R T, Liu S M, Wang S X, Pan W G, Li M Y. Appl. Catal. A Gen., 2017, 531: 129.
[138]

Liu J, Guo R T, Li M Y, Sun P, Liu S M, Pan W G, Liu S W, Sun X. Fuel, 2018, 223: 385.
[139]

Fan Z Y, Shi J W, Gao C, Gao G, Wang B R, Wang Y, He C, Niu C M. Chem. Eng. J., 2018, 348: 820.
[140]

Guan J K, Zhou L S, Li W Q, Hu D, Wen J, Huang B C. Catalysts, 2021, 11(3): 324.
[141]

Gao C, Xiao B, Shi J W, He C, Wang B R, Ma D D, Cheng Y H, Niu C M. J. Catal., 2019, 380: 55.
[142]

Li W, Zhang C, Li X, Tan P, Fang Q Y, Chen G, Journal of Fuel Chemistry and Technology, 2017, 45(12): 1508.
[143]

( 李伟, 张成, 李鑫, 谭鹏, 方庆艳, 陈刚. 燃料化学学报, 2017, 45(12): 1508.)
[144]

Zhuang K, Zhang Y P, Huang T J, Lu B, Shen K. Journal of Fuel Chemistry and Technology, 2017, 45(11): 1356.
[145]

( 庄柯, 张亚平, 黄天娇, 陆斌, 沈凯. 燃料化学学报, 2017, 45(11): 1356.)
[146]

Zhu Y W, Zhang Y P, Xiao R, Huang T J, Shen K. Catal. Commun., 2017, 88: 64.
[147]

Huang T J, Zhang Y P, Zhuang K, Lu B, Zhu Y W, Shen K. Journal of Fuel Chemistry and Technology, 2018, 46(3): 319.
[148]

( 黄天娇, 张亚平, 庄柯, 陆斌, 朱一闻, 沈凯. 燃料化学学报, 2018, 46(3): 319.)
[149]

Casanova M, Llorca J, Sagar A, Schermanz K, Trovarelli A. Catal. Today, 2015, 241: 159.
[150]

Kim J, Lee S, Kwon D W, Ha H P. Catal. Today, 2021, 359: 65.
[151]

Jin Q J, Shen Y S, Zhu S M, Li X H, Hu M. Chin. J. Catal., 2016, 37(9): 1521.
[152]

Du H, Han Z T, Wu X T, Li C L, Gao Y, Yang S L, Song L G, Dong J M, Pan X X. Catalysts, 2021, 11(5): 618.
[153]

Niu C H, Wang B R, Xing Y, Su W, He C, Xiao L, Xu Y R, Zhao S Q, Cheng Y H, Shi J W. J. Clean. Prod., 2021, 290: 125858.
[154]

Fokema M D, Ying J Y. J. Catal., 2000, 192(1): 54.
[155]

Zhang S, Liu X, Zhong Q, Yao Y. Catal Commun, 2012, 25:7.
[156]

Damma D, Pappas D K, Boningari T, Smirniotis P G. Appl. Catal. B Environ., 2021, 287: 119939.
[157]

Zhang Y D, Ji M L, Zhou G H, Zhang Z Y. Harbin: 2014203.
[158]

( 张延东, 姬明林, 周广贺, 张志远. 哈尔滨: 2014203.).
[159]

Xiao G Z. Clean Coal Technol., 2019, 25(6): 146.
[160]

( 肖国振. 洁净煤技术, 2019, 25(6): 146.).
[161]

Wu D J, Zhou S H, Li J Y, Yang X B, Ge C M. CN201610418613.6. 2016-11-08.
[162]

Tang Z C, Zhang G D, Han W L. CN202010418630.6. 2020-08-13.
[163]

Zhu S M, Shen Y S. CN200810020425.3. 2008-08-05.
[164]

Zhu S M, Shen Y S. CN200810020427.2. 2008-08-05.
[165]

Zong Y H, Wang H, Chen Z P. Huang L, Li Q, Wang X W, Sun D. CN201610725462.9. 2017-01-03.

Funding

National Natural Science Foundation of China(U2002212)

Fundamental Research Funds for the Central Universities(FRF-IDRY-20-005)

Postdoctor Research Foundation of Shunde Graduate School of University of Science and Technology Beijing(2020BH012)

PDF (7125KB)

2096

Accesses

0

Citation

Detail
Sections
Recommended

/

〈 〉

Address of Editorial Office: No. 33 Beisihuan Xilu, Zhongguancun , Beijing 100190, China
Tel: +86 10 8262 7757
Fax: +86 10 8262 7757
E-mail: progchem@mail.las.ac.cn
http://www.progchem.ac.cn
    • 　
    Copyright © Editorial Office of Progress in Chemistry