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Review

TiO2-Supported Catalysts in Low-Temperature Selective Reduction of NOx with NH3: A Review of Recent Progress

by
Xue Bian
1,2,*,
Jing Wang
1,2,
Yuting Bai
3,
Yanping Li
1,2,
Wenyuan Wu
1,2 and
Yuming Yang
1,2
1
Key Laboratory of Ecological Metallurgy of Multi-Metal Intergrown Ores of Ministry of Education, Shenyang 110819, China
2
School of Metallurgy, Northeastern University, Shenyang 110819, China
3
School of Metallurgy and Materials Engineering, Liaoning Institute of Science and Technology, Benxi 117004, China
*
Author to whom correspondence should be addressed.
Catalysts 2024, 14(9), 558; https://doi.org/10.3390/catal14090558
Submission received: 8 June 2024 / Revised: 21 August 2024 / Accepted: 23 August 2024 / Published: 25 August 2024
(This article belongs to the Special Issue Recent Catalytic Progresses for Environmental Remediation and Pollutant Degradation)
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Abstract

:
Selective catalytic reduction (SCR) stands out as a pivotal method for curbing NOx 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.

Graphical Abstract

1. Introduction

Nitrogen oxides (NOx) stand as significant contributors to a plethora of environmental problems, including the greenhouse effect, acid rain, and photochemical smog [1,2,3]. Consequently, nations worldwide have implemented stringent regulations to curb NOx emissions, particularly in industrial settings where combustion processes were prevalent. For instance, the European Union imposes NOx emission limits of 175 mg/m3 for fluidized bed combustion (FBC) and 150 mg/m3 for pulverized coal combustion (PC) [1]. Similarly, China mandated NOx emission standards of 100 mg/m3 for new power plants and natural gas boilers, and 50 mg/m3 for gas turbines [4]. Meeting these standards necessitated the deployment of effective NOx reduction strategies. The emission status of nitrogen oxides is shown in Figure 1. In industrial settings, several methods are employed to mitigate NOx control, with selective catalytic reduction (SCR) emerging as one of the most efficient technical methods [5,6,7]. SCR systems utilize a reducing agent, such as, typically, ammonia (NH3) and convert poisonous NOx into harmless nitrogen (N2) and water vapor (H2O) in the presence of a catalyst [8]. The choice between SCR, selective non-catalytic reduction (SNCR), or combined approaches depends on various factors, including emission regulations, cost considerations, space limitations, and specific operating conditions [9].
The catalyst is central to SCR technology and plays a pivotal role in the conversion process of nitrogen oxides. Catalysts are typically composed of support materials, active components, and additives [10]. The support provides the support structure and reaction surface for the catalyst [11]. Moreover, the support also has catalytic activity, which can not be ignored in broadening the temperature range of the catalyst reaction and improving the catalytic performance [12]. Common support materials include metal oxides, molecular sieves, and carbon-based materials, each with distinct properties influencing the SCR system performance [13,14,15,16,17]. Taking TiO2-supported Mn as an example, the reaction process of the TiO2-supported catalyst is mainly the Lewis acid site reaction and the Brønsted acid site reaction (Figure 2), and its various characteristics will directly affect the progress of the two reactions [18]. Because, in the non-power plant environment, the plant first desulfurizes the flue gas, and the flue gas temperature to complete the desulfurization is mostly below 250 °C, researchers had to develop low-temperature denitrification catalysts to adapt to industrial requirements [19,20,21,22]. TiO2 has many advantages, such as abundant acidic sites, and offers excellent dispersion of active components and SO2 resistance [23,24,25]. Therefore, TiO2 as an excellent low-temperature SCR catalyst support has been widely studied and applied [26,27]. However, the catalyst with TiO2 support has poor thermal stability and a narrow temperature range, which can be improved. And the research on the mechanism of the catalyst’s resistance to H2O/SO2 poisoning is poor.
This paper mainly reviewed the influence and mechanism of TiO2 support on the NH3-SCR catalyst from micro and macro perspectives, including TiO2 crystal form, crystal face, support structure, composite of other substances, and preparation methods. The effects of these factors on the resistance of the catalyst to H2O and SO2 were also discussed. It is hoped that this paper can provide reference for the development and improvement of TiO2 support.
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Figure 1. Industrial exhaust gases source and comparation of various NOx removal technologies [28].
Figure 1. Industrial exhaust gases source and comparation of various NOx removal technologies [28].
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Figure 2. Schematic diagram of denitration mechanism of MnOx/TiO2 catalyst [18].
Figure 2. Schematic diagram of denitration mechanism of MnOx/TiO2 catalyst [18].
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2. Effect of TiO2 Support Morphological Regulation on Catalysts

TiO2 possesses three crystalline phases: anatase, rutile, and brookite, with the anatase and rutile phases being the most investigated ones. Recently, TiO2 nanomaterials with novel properties and applications, especially TiO2 nanotubes, nanorods, fibers and mesoporous materials derived from the hydrothermal treatment, have been developed [29,30,31]. Anatase has a higher specific surface area and wider application than rutile in the selective catalytic reduction of NO catalysts in ammonia synthesis [32,33,34]. Anatase is also more active in catalysis than rutile [35,36]. For anatase TiO2 support, different crystal planes show dissimilar activities due to different surface nature. The sequence of the average facet energies of anatase TiO2 is {001} (0.90 J/m2) > {100} (0.53 J/m2) > {101} (0.44 J/m2) [37]. The advantages of anatase are well known, and the researchers recently verified them by comparing the performance of catalysts supported by single-crystal anatase (101) and single-crystal rutile (110).

2.1. Mechanism and Properties of SCR Catalysts with Different Crystal Faces

P.R. Ettireddy et al. utilized a wet-impregnation method to synthesize Mn/TiO2 catalysts. The performance of catalysts supported by anatase and rutile TiO2 was compared [25]. The finding showed that the NO conversion rate of a single rutile is zero, but the interaction between anatase TiO2 and Mn is better, and the denitrification efficiency of the catalyst with anatase TiO2 is also higher. Y. Zeng [38] prepared Mn/TiO2 using rutile TiO2 as supports. TiO2 and MnOx provided acidic and redox sites for catalytic reaction, respectively. The uneven dispersion of acid sites enhanced the selectivity of N2O, leading to excessive activation of NH3. Therefore, anatase TiO2 is the main source of support for SCR catalysts. Many researchers who discussed the denitrification performance of the SCR catalysts preferentially exposed anatase (001) and (101) surfaces. It was found that loading the active component on the (001) surface can obtain better activity and N2 selectivity [39]. L. Xin et al.’s research pointed out that the (001) surface of anatase TiO2 was proved to be more active than the (101) surface in the SCR reaction. When the two surfaces are separately loaded with MnO2, the energy barriers of the SCR reaction on the Mn (001) surface were smaller than those on the Mn (101) surface, indicating that N2 and H2O formation on the Mn (001) surface was easier [40]. Deng et al. found that MnOx/TiO2 with exposed {001} surface performed better than the conventionally used MnOx/TiO2 with exposed {101} surface [39]. The MnOx/TiO2 (NS) catalyst could achieve both great NO removal efficiency and excellent N2 selectivity from 80 to 280 °C. L. Quan et al. [41] synthesized Mn-Ce/TiO2 catalysts, and TiO2 with different crystal faces was used as the support. The results pointed out that the anatase TiO2 (001) could be preferentially exposed, which was beneficial to the selective catalytic reduction performance of Mn-Ce/TiO2 at low temperature. The results showed that titanium dioxide preferentially exposed the (001) crystal plane is helpful for a larger specific surface area and increasing the surface acidic sites of the catalyst. In the temperature range of 100–160 °C, as shown in Figure 3, it can be observed that the NO conversion of Mn-Ce/TiO2 (001) is about 30%, which was higher than that of Mn-Ce/TiO2 (101). Subsequently, F. Meng et al. [42] prepared catalysts by TiO2, and preferentially exposed the TiO2 (001), (101), and (010) facet, in turn. Comparison results showed that the catalyst with exposed TiO2 (001) had excellent denitration efficiency; it was due to the fact that the Ti-OOH generated on the surface of TiO2 (001) could better produce O2.

2.2. Resistance to H2O/SO2 of TiO2 Catalysts with Different Crystal Faces

It was probable that ammonium sulfate and thermostable active ingredient sulfates such as MnSO4 and Ce2(SO4)3 formed, which could lead to deactivation of catalysts’ active sites [43,44]. Compared with the anatase TiO2 exposing {101} facets, the anatase TiO2 with {001} facets exposed had a large number of Lewis acid sites and active oxygen atoms, which was conducive to improving the reaction performance of NH3-SCR [45].
Firstly, after sulfur poisoning, the catalyst surface will form a sulfate precipitate, resulting in the catalyst surface plugging and agglomeration [46]. However, TiO2 (001) as the support catalyst can reduce the formation of surface sulfate and improve the sulfur resistance of the catalyst [47,48]. Additionally, the anatase TiO2 {001} surface could effectively inhibit the sulfation of active ingredients, which was owing to the five coordinated titanium atoms (Ti5c) and two coordinated oxygen atoms on the anatase TiO2 {001} facets, which could preferentially react with SO2 to avoid the deactivation of active sites after the poisoning experiment [49]. L.Junchen et al. prepared Mn-Ce/TiO2-NS and Mn-Ce/TiO2-NP catalysts with anatase TiO2 with {001} facets (TiO2-NS) exposed and anatase TiO2 with {101} facets (TiO2-NP) exposed as supports [50]. The Mn-Ce/TiO2-NS catalyst still had a relatively excellent catalytic performance after the SO2 resistance test (Table 1). The TiO2-NS catalyst still had a high specific surface area after the SO2 resistance test, which was attributed to the inhibition of the formation of ammonium bisulfate and ammonium sulfate. H2O typically has a detrimental impact on the NH3-SCR reaction, exacerbating the sulfur poisoning of the catalysts. Although Mn/TiO2 catalysts have shown excellent performance in NH3-SCR reactions, conventional Mn-based catalysts still suffered from severe deactivation in flue gases containing low concentrations of sulfur dioxide, especially in the presence of water vapor (H2O (g)), due to the formation of Mn sulfates [51,52]. Li Junchen et al. had found that anatase TiO2 {001} facets can enhance the denitrification and reduce the effect of H2O on the performance of the catalyst [53].

3. Effect of TiO2 Structure on Catalyst

The different structures such as particle size, pores, and core-shell of TiO2 could also have an effect on the catalytic performance. By preparing SCR catalysts with TiO2 controllable structure support, the denitrification performance and water/sulfur poisoning resistance of the SCR catalysts can be improved.

3.1. Pore Structure

The reactants need to enter the catalyst through the pore structure on the catalyst surface for reaction. The abundant pore structure increases the specific surface area and active sites. The reactants are better able to physically or chemically adsorb on the catalyst surface [54,55,56,57]. Therefore, researchers can design 3DOM through experiments and regulate the size of mesoporous and microporous TiO2, etc., to prepare the catalyst support, so that it can better adapt to the application conditions [58,59,60]. Yang et al. [61] produced MnOx/TiO2 catalysts by TiO2 with different initial particle sizes as supports. The comparison results showed that the appropriate TiO2 particle size was beneficial for bridging nitrate reactions and promoted NH3 reactions. The suitable denitrification temperature for the MnOx/TiO2 (10–25 nm) catalyst can reach 135 °C. Nannuzzi et al. [24] prepared the catalyst by loading V2O5 with titanium dioxide of different particle sizes for low temperature NH3-SCR, based on standard and HSA-TiO2 anatase supports, with a surface area of 89 m2/g and 181 m2/g, respectively. The results show that V2O5 is easily dispersed on TiO2 support with high specific surface area. As shown in Figure 4, more Brønsted acid sites were generated on the catalyst surface, which was conducive to the performance of the catalyst. The mesoporous (DT-51) and microporous TiO2 were used as supports for synthesized 5 wt % V2O5/TiO2 catalysts by Youn et al. [62]. The NO removal efficiency of V2O5/microporous TiO2 catalyst can reach 99%, and that of the V2O5/mesoporous TiO2 catalyst is about 95%. Under 500 ppm SO2 and 3% H2O added in flue gas, the NO conversion of the former was decreased to 97.5%, while that of the latter was obviously reduced to 85%. It was because abundant V2O5 formed on the mesoporous TiO2 surface, which had more V-O-V groups and facilitated the reaction between SO2 and O2, leading to catalyst NH4HSO4 poisoning and reduced denitration efficiency. M Yibo et al. synthesized a novel and rational framework-confined ordered mesoporous CeSnOx/TiO2 catalyst [63]. Their research showed that the presence of the ordered mesoporous structure makes the catalyst had a prominent confined effect on the framework. In addition, the ordered mesoporous structure of the catalyst guided the active components to produce a synergistic effect. The uniform pore structure and metal doping enhanced the anti-poisoning ability. Tan et al. [64] prepared four kinds of CeTiOx catalysts with different mesoporous structures, as shown in Table 2. Due to the change of pore structure, the specific surface area of the catalyst is optimized. More Brønsted acid is generated on the surface of the catalyst, which is conducive to the low temperature reaction of SCR [65].

3.2. Core-Shell Structure

A single nano TiO2 is easy to agglomerate at high temperature, making its chemical properties unstable. In order to change this property, TiO2 nanoparticles are coated with porous and stable shells [66,67]. The inner shell and outer shell are combined through physical and chemical interactions to form a stable core–shell structure [68,69]. The SCR catalyst support of nano-TiO2 with a core–shell structure greatly enhances the low temperature performance of SCR catalysts. The catalysts had better H2O/SO2 poisoning tolerance [70,71,72]. Core–shell materials have several advantages, such as a large specific surface area, regular shape, controllable size, and stable performance, making them highly promising in the field of catalysis.
Liu et al. prepared the 5% WO3/TiO2@CeO2 (W/Ti@Ce) catalyst with core–shell structures. Compared to ordinary WO3/TiO2 catalysts, it exhibited the best NH3-SCR performance (NO conversion and N2 yield above 95% at 250–500 °C) due to the synergistic effect of redox ability and acidity [73]. Fu Zihao et al. prepared the H-MnO2@TiO2 catalyst with a hollow spherical structure [74]. They changed the properties of the Mn-Ti catalyst by hydrothermal method and modified by kinetic adsorption and vapor deposition methods. The TiO2 layer can effectively limit the excessive redox performance and improve the acidity of the catalyst surface, with the NO conversion above 90% at 140–380 °C of the H-MnO2@TiO2 catalyst. As shown in Figure 5, NH3 and NO could be adsorbed and activated on the catalyst surface, and the catalytic reaction follows the Langmuir–Hinshelwood (L–H) mechanism. Under the presence of H2O, the NH4+ bonding to Brønsted acid sites was inhibited but the NH3 bonding to Lewis acid site was almost unaffected. Co(3-x)MnxO4@TiO2 core–shell catalysts synthesized by Qi et al. demonstrated that core–shell structure enhanced acidity and redox capacities [75]. Because of titanium dioxide shell protection in the core–shell structure, the catalyst had improved water and sulfur resistance. In Figure 6, we can clearly see the denitration performance and sulfur resistance effect of different catalysts. The most probable reason is that the high resistance of CoMn2O4@TiO2 may cause a reaction between SO2 and TiO2 on the outer surface of the catalyst that generates TiSO4O, thus trapping the SO2 in the flue gas outside the catalyst.

4. The Effect TiO2-X Composite Structural Support on SCR Catalyst Performance

Because metal oxides (Al2O3, SiO2, etc.) and carbon materials themselves also have catalytic properties, and doping into the TiO2 support can amplify the characteristics of the two substances at the same time [76,77,78], researchers had prepared composite supports to improve the stability of the catalyst and the ability to resist H2O/SO2 poisoning [79].

4.1. TiO2 Composite Metal Oxide as the Support

In order to improve the poor thermal stability of TiO2, researchers doped TiO2 with strong thermal stability of metal compounds such as Al2O3, SiO2, CeO2, and ZrO2. Such composite support can broaden the temperature range of the catalyst and make the low temperature performance of the catalyst more stable [80,81,82].
In the heterogeneous catalysis of titanium dioxide, the surface acidity of the support and the acid–base interaction between it and the active component play an important role [83,84]. When the amount of active components is constant, the Al2O3-TiO2 composite support may affect the surface acid concentration of the catalyst, especially in the low-temperature NH3-SCR reaction [85,86]. R. Camposeco et al. prepared a SCR-NH3 catalyst using titanate nanotubes with alumina (NT-Al) as the support. Because Al2O3 was added to the TiO2 support, the amount of L-acid was increased by two times while keeping the surface B-acid unchanged. This makes the catalyst have a good low-temperature denitrification ability [87]. Meanwhile, R. Camposeco et al. synthesized V2O5/NPTiO2-Al2O3 (nanoparticles) and V2O5/NTiO2-Al2O3 (nanotubes) catalysts. The V2O5/NTiO2–Al2O3 model catalyst featured a high catalytic activity (98% of NO conversion), good thermal stability (up to 450 °C), and high H2O deactivation resistance. After adding Al, NTiO2 has a better-ordered tubular shape and the effective temperature range of the catalyst was broadened [88]. Qijie Jin, Dr et al. prepared a WCeMnOx/TiO2-ZrO2 catalyst. The circular TiO2-ZrO2 nanoparticles have a unique hollow structure, exposing more active centers. The catalyst can remove Hg and chlorobenzene as well as NO [89]. Lu Qiu et al. prepared a Mn-Co-Ce/TiO2-SiO2 catalyst using TiO2/SiO2 nanocomposites as the support. The specific surface area of TiO2-SiO2 is larger than that of TiO2, resulting in a thinner layer of active components and a reduced wall thickness of the catalyst. Therefore, the catalyst has good low temperature performance and improved SO2 resistance [90].

4.2. TiO2 Composite Carbon Material as the Support

Activated carbon (AC), carbon nanotubes (CNTs), and graphene (GR) were recently regarded as important catalytic supports due to their unique electronic transportation properties and facile flowing bond [91,92,93,94]. Li et al. [95] prepared the V2O5-CeOx/TiO2-carbon nanotube by sol–gel method and found that the appearance of CNTs increased chemisorbed oxygen thus facilitated the SCR activity. S.Raja et al. prepared titania-carbon nanotubes (TiO2-CNTs) that supported MnOx-CuO catalysts [96]. As the TiO2-CNTs composite structure was used as the support, the specific surface and porosity of the catalyst were increased, and the average pore diameter was decreased. Simultaneously, the ratio of Oα/(Oα + Oβ) on the catalyst’s surface had the higher relative concentration. The temperature peak of the catalyst also moves like low temperature. More than 90% of the denitration efficiency of the catalyst moves 50 °C to the low temperature region, and the denitration efficiency can reach more than 90% at 150–300 °C. Before that, their work also demonstrated the advantages of carbon composite structures. The SCR catalyst made of copper or iron with titanium as a support also has a better catalytic performance than the catalyst supported by titanium alone [97]. Jae-Rang Youn et al. studied the influence of CNTs addition on Mn-Ce/TiO2 catalysts for low-temperature NH3-SCR of NO. Due to the addition of CNTs, the surface oxygen species of the catalyst and the oxygen form of Mn were changed. This suggests the catalytic activity and N2 selectivity of the catalyst are significantly improved at 140–240 °C [98]. Wang Qiulin et al. prepared V2O5/TiO2-CNTs catalysts, which removed PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) and NOx [99]. Lu Xining et al. prepared CeOX-MnOX/TiO2-GE catalysts with TiO2–graphene (TiO2–GE) nanocomposites as support. As shown in Figure 7, tiny particles of TiO2 were distributed uniformly throughout the lamellar of GE. The full contact between the support and the active component promotes the catalytic reaction [100].

5. Conclusions and Perspectives

NH3-SCR is the most effective catalytic denitrification technology, and the application of catalyst is related to the improvement of NH3-SCR reaction efficiency. The paper reviews the influences of various aspects of TiO2 support on catalysts (such as crystal form, crystal surface, structure, doping with other substances, etc.) and the reaction mechanism of the catalyst with TiO2 support. This paper also briefly summarized the influence of different TiO2 supports on the water/sulfur toxicity resistance of the catalyst. This is conducive to the further study of NH3-SCR catalyst. The catalyst with TiO2 support has poor thermal stability and a narrow temperature range, which can be improved by the above methods.
Although people have made a lot of efforts in the research of NH3-SCR catalyst with TiO2 as the support, the following problems still exist.
First of all, most studies are conducted from the perspective of active components, and there are few in-depth studies on the influence and mechanism of the support itself.
Secondly, the research on the mechanism of the catalyst’s resistance to H2O/SO2 poisoning is limited to the catalyst as a whole, and the analysis of the support alone is lacking.

Author Contributions

Data curation, Y.Y.; writing—original draft preparation, J.W.; writing—review and editing, J.W., Y.B. and Y.L.; supervision, Y.B.; project administration, X.B. and W.W.; funding acquisition, X.B. and W.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 3. Reaction mechanism of different crystal surface of TiO2 and denitrification performance under the same conditions [41].
Figure 3. Reaction mechanism of different crystal surface of TiO2 and denitrification performance under the same conditions [41].
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Figure 4. V surface density of TiO2 with different specific surface areas.
Figure 4. V surface density of TiO2 with different specific surface areas.
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Figure 5. Effect of modification on physicochemical properties of catalysts and catalytic reaction mechanism [72].
Figure 5. Effect of modification on physicochemical properties of catalysts and catalytic reaction mechanism [72].
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Figure 6. Sulfur resistance of CoMn2O4@TiO2 core–shell catalyst at 225 °C for 24 h. Reaction conditions: 500 ppm NO, 500 ppm NH3, 5% O2, and balance N2, with 100 ppm SO2, GHSV = 24,000 h−1 [73].
Figure 6. Sulfur resistance of CoMn2O4@TiO2 core–shell catalyst at 225 °C for 24 h. Reaction conditions: 500 ppm NO, 500 ppm NH3, 5% O2, and balance N2, with 100 ppm SO2, GHSV = 24,000 h−1 [73].
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Figure 7. Schematic diagram of denitration reaction on CeOX-MnOX/TiO2-GE catalysts.
Figure 7. Schematic diagram of denitration reaction on CeOX-MnOX/TiO2-GE catalysts.
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Table 1. Effect of SO2 poisoning on Mn-Ce/TiO2-NS and Mn-Ce/TiO2-NP catalytic performance [50].
Table 1. Effect of SO2 poisoning on Mn-Ce/TiO2-NS and Mn-Ce/TiO2-NP catalytic performance [50].
Catalyst Mn-Ce/TiO2-NS (001)Mn-Ce/TiO2-NP (101)
the NO conversionNo SO2 at 180 °C91.2%68.1%
200 ppm SO2 at 180 °C81.7%50.6%
BET (m2/g)normal conditions39.733.7
After SO2 poisoning39.623.1
The acid situation Brønsted acid (lmol/g)Before SO2 poisoning2.0582.872
After SO2 poisoning19.24323.617
Lewis acid (lmol/g)Before SO2 poisoning43.53623.105
After SO2 poisoning42.50630.845
Table 2. Effect of different pore structures on catalyst properties.
Table 2. Effect of different pore structures on catalyst properties.
CatalystThree-Dimensionally Ordered Macroporous–Mesoporous (3DOM-m) CeTiOxThree-Dimensionally Ordered Macroporous (3DOM) CeTiOxThree-Dimensionally Ordered Mesoporous (3DOm) CeTiOxDisordered Mesoporous (DM) CeTiOx
The NO conversion
(above 90%)/°C		250–400 °C300–400 °C275–400 °C325–400 °C
Surface area A/(m2·g−1)107.360.957.649.3
Pore volume v/(cm3·g−1)0.2170.1190.3480.097
Average pore size d/nm8.17.45.47.5
Brønsted acid (μmol/g)10443.96632.8
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Bian, X.; Wang, J.; Bai, Y.; Li, Y.; Wu, W.; Yang, Y. TiO2-Supported Catalysts in Low-Temperature Selective Reduction of NOx with NH3: A Review of Recent Progress. Catalysts 2024, 14, 558. https://doi.org/10.3390/catal14090558

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Bian X, Wang J, Bai Y, Li Y, Wu W, Yang Y. TiO2-Supported Catalysts in Low-Temperature Selective Reduction of NOx with NH3: A Review of Recent Progress. Catalysts. 2024; 14(9):558. https://doi.org/10.3390/catal14090558

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Bian, Xue, Jing Wang, Yuting Bai, Yanping Li, Wenyuan Wu, and Yuming Yang. 2024. "TiO2-Supported Catalysts in Low-Temperature Selective Reduction of NOx with NH3: A Review of Recent Progress" Catalysts 14, no. 9: 558. https://doi.org/10.3390/catal14090558

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