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Article

PTFE-Modified Mn-Co-Based Catalytic Ceramic Filters with H2O Resistance for Low-Temperature NH3-SCR

by
Kun Li
,
Tao Zhou
,
Xinqiang Xu
,
Changye Han
,
Hua Zhang
* and
Jiang Jin
*
College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China
*
Authors to whom correspondence should be addressed.
Sustainability 2022, 14(9), 5353; https://doi.org/10.3390/su14095353
Submission received: 20 March 2022 / Revised: 25 April 2022 / Accepted: 27 April 2022 / Published: 29 April 2022
(This article belongs to the Section Environmental Sustainability and Applications)
Browse Figures
Versions Notes

Abstract

:
Mn-Co-based catalysts were loaded to ceramic filters element by impregnation for the coprocessing of dust and nitrogen oxide (NOx) in flue gas. The influence of the Mn/Co ratio and loading on the catalytic performance was investigated. The Mn-Co-based catalytic ceramic filter with a Mn/Co molar ratio of 2/1 can achieve 99% NO conversion by selective catalytic reduction of NOx with NH3 (NH3-SCR) in the temperature range of 100−180 °C, but its resistance to H2O was relatively poor. The filter element was modified by PTFE to improve the H2O resistance. After modification, the catalytic ceramic filter showed superior resistance to H2O and SO2 at low temperatures (100–180 °C) and satisfactory self-cleaning performance.

1. Introduction

With the development of industry, emissions of pollutants such as nitrogen oxides, particulate matter and sulfur dioxide are increased significantly [1]. It is a great challenge to treat pollutants efficiently and properly. In the conventional flue gas cleaning process, denitrification and dust removal are two independent processes, which have the disadvantages of large space occupation, high cost and difficult maintenance. The integrated flue gas purification process has become a new trend because of its short process flow, low investment in equipment, low operating cost and small space occupation [2]. Catalytic bag filters and catalytic filter elements are often used for the removal of NOx and dust, simultaneously. Commercial bag filters hardly maintain their basic performance in harsh environments of high temperatures, high humidity and corrosion. Additionally, the catalysts can fall off due to the deformation of the bag filter during the blowback process. The rigid ceramic filters show significant advantages in high mechanical strength, corrosion resistance and superior thermal stability [3,4]. Low-density porous ceramics made with ceramic fibers can remove more than 99% of dust in flue gas [5]. After loading the catalyst, the low-density porous ceramic can remove NOx and dust simultaneously [6,7].
Catalysts are one of the most important components in a catalytic filter [8]. V-based catalysts are often utilized in catalytic filters because of their satisfactory denitrification performance at high temperatures (300–400 °C) [9,10]. Even though low-temperature V-based catalysts have been reported in recent years, their biological toxicity restricted their application [11,12]. Fe-based catalysts are also frequently used in catalytic filters, but they exhibit higher catalytic activity only at high temperatures (250–400 °C) [13,14,15]. V-based catalysts and Fe-based catalysts do not maintain their catalytic performance at low temperatures. Mn-based catalysts are widely studied for flue gas denitrification at low temperatures owing to their rich variable valence [16]. The catalytic performance of Mn-based catalysts can be improved by introducing other transition metals such as Fe [17,18], Ce [19,20], Cu [21] and Zr [22]. Li et al. [23] have reported that a MnOx-CeO2-based catalytic filter showed >90% NO conversion from 120 to 250 °C. Some studies showed that Co as a doped element can significantly enhance low-temperature denitrification efficiency [24]. In this paper, Co was introduced to a Mn-based catalyst to enhance the low-temperature catalytic activity.
In low-temperature flue gas, a large amount of water vapor will compete with the reactants (NO or NH3) for adsorption [25]. The effect of H2O on the MnOx catalyst was mentioned by Pan et al. [26]. After the introduction of 10% H2O, the catalyst activity was severely lost, and the NO conversion over MnOx only retained 20% at 110 °C. It has been reported that graphite can enhance the resistance to H2O of MnOx [27]. The hydrophobic surface was constructed to enhance the H2O resistance for low-temperature catalysts. Zhang et al. [28] reported that the superhydrophobic MnOx-based octahedral molecular sieves (OMS-2) modified by PDMS maintained more than 88% NO conversion under 10% H2O content in feed gas from 200 to 280 °C. PTFE as an excellent hydrophobic modifier is widely used in chemical, petroleum, textile, electronic and mechanical industries due to its advantages of corrosion resistance, aging resistance and its’ having a low friction coefficient [29,30,31]. It has been reported that the MnOx catalyst mixed with PTFE showed hydrophobicity and good H2O resistance at low temperatures [32]. However, the application of manganese oxides is severely restricted because of their low surface area and poor thermal stability. The introduction of a secondary element into manganese metal oxides can increase the surface defects and promote the efficiency of the manganese metal oxides for the catalytic abatement of NOx in the NH3-SCR reaction.
In this work, the low-temperature catalytic ceramic filter was prepared by loading the Mn-Co-based catalyst on the low-density ceramic (LDC) for removing dust and nitrogen oxides simultaneously. The effects of the Mn/Co molar ratio and catalytic loading on the catalytic performances for the NH3-SCR process are discussed. The surface of the filter element was modified by PTFE for improving the H2O resistance at low temperatures. The H2O and SO2 resistance and self-cleaning performance of hydrophobic filter elements were investigated.

2. Materials and Methods

2.1. Preparation of Catalytic Ceramic Filters

The preparation procedure of LDC was described in previous works [33,34]. The mixture of alumina fiber, glass powder, binder and water was mixed thoroughly and pressed into cylindrical body (φ 22 × 10 mm). The green body was sintered at 1150 °C for 1 h. Mn-Co-based catalyst was loaded on LDC by the impregnation method. Firstly, the catalyst solution was prepared by dissolving cobalt nitrate hexahydrate (AR., Aladdin Reagent Co., Ltd., Shanghai, China) and manganese nitrate (AR., Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) in water. Then LDC was impregnated with the above solution for 15 min and dried at 60 °C for 4 h. Finally, LDC loaded with catalyst (Mn-Co/LDC) was heated at 450 °C for 2 h. Mn-Co/LDCs with different Mn/Co molar ratios were marked as MnaCobOx/LDC.
Polytetrafluoroethylene dispersion (PTFE, 60 wt.%) was used for the surface modification of Mn-Co/LDC. The Mn-Co/LDCs were soaked in PTFE dispersion (15 wt.%, 25 wt.%, 35 wt.%) for 10 min, then dried at 60 °C for 3 h and cured at 200 °C for 2 h. Lastly, the samples were labeled as 15-PTFE-Mn-Co/LDC,25-PTFE-Mn-Co/LDC and 35-PTFE-Mn-Co/LDC.

2.2. Catalytic Activity Measurement

A tubular catalytic reactor was utilized for testing catalytic activity of all catalysts. The feed gas was composed of 500 ppm NH3, 500 ppm NO, 6 vol.% O2, 50 ppm SO2 (when used), 5–15 vol.% H2O (when used), and balance N2. The filtration velocity was 1 m/min (GHSV = 75,000 h−1) The concentrations of NO were detected by an ECOM-D flue gas analyzer (Ecom GmbH, Nordrhein-Westfalen, Germany). The conversion efficiency of nitrogen oxides was calculated according to Equation (1).
NO   conversion = NO in − NOx out NO in × 100 %

2.3. Characterization

X-ray diffraction (XRD) for MnaCobOx was characterized by a Rigaku Smartlab X-ray diffractometer (Rigaku Co., Tokyo, Japan). The data were collected with a scanning speed of 10°/min and a step size of 0.02° over the angular range 10–80°. The microstructure and morphology of LDC and Mn-Co/LDC were detected by scanning electron microscope (SEM, JSM-6510, JEOL Ltd., Tokyo, Japan). Energy dispersive spectrometry (EDS) was obtained via a Vantage DS X-ray energy spectrometer. (JEOL Ltd., Tokyo, Japan) The hydrophobicity of PTFE-modified samples was characterized based on water contact angle (CA), which was measured using the contact angle system DSA 100(KRÜSS GmbH, Hamburg, Germany). FT-IR was conducted on IN10 (Thermo Nicolet Co., Madison, American) and the spectra were acquired within the frequency range of 4000–400 cm−1.
A laser dust meter was used for testing the dust concentration in feed gas and outlet gas to determine the dust removal efficiency of the catalytic ceramic filter. The filtration resistance was measured according to the Chinese standard “test method of the performance of high-efficiency particulate air filters” (GB/T 6165–2008) [34]. The filtration resistance of the ceramic filter can be calculated according to Equation (2).
F = Δ P · A Q
F is the resistance of the catalytic filter, Δ P is the pressure drop, A is the cross-sectional area, and Q is the flow rate.
The self-cleaning performance of PTFE-Mn-Co/LDC was studied through a simulation experiment [35] and the detailed process was described below. The filtration resistance was also used for evaluating the self-cleaning performance of PTFE-Mn-Co/LDC. The process is described as follows. First, Mn-Co/LDC and PTFE-Mn-Co/LDC were covered by fly ash with particle sizes of 2–3 µm. Then, the dust on the surface was washed off with water. The filtration resistance for Mn-Co/LDC and PTFE-Mn-Co/LDC were measured. The above experimental process is repeated several times. The change in filtration resistance with filtration times was recorded.

3. Results and Discussions

3.1. Denitrification and Filtration Performance of Mn-Co/LDC

The low-temperature catalytic performance of Mn-Co/LDCs with different Mn/Co molar ratios is shown in Figure 1a. The NO conversion over MnaCobOx/LDCs is above 80% from 120 to 220 °C. With the temperature rises, the denitrification performance of all samples declines gradually. Among them, Mn2Co1Ox/LDC and Mn3Co1Ox/LDC exhibit higher NO conversion, which keeps at ~100% from 100 to 180 °C. Mn2Co1Ox/LDC shows better catalytic performance after 180 °C. Obviously, the catalytic performance of MnaCobOx/LDCs is related to the molar ratio of Mn/Co. For comparison, the catalytic performance of MnOx/LDC and CoOx/LDC is measured and the NO conversion is significantly lower than that of MnaCobOx/LDCs. The excellent catalytic performance of MnaCobOx/LDCs is attributed to the synergistic effect of MnOx and CoOx.
The phase composition of MnaCobOx catalysts was analyzed by X-ray powder diffraction. The XRD patterns of Mn-Co catalysts with the Mn/Co ratio ≤1 exhibit sharp diffraction peaks, and can be indexed to Co3O4 (PDF# 42-1467) (Figure 1b). The XRD patterns for Mn2Co1Ox and Mn3Co1Ox show the broadening and weakening of the diffraction peaks, which implies a smaller particle size and lower crystallinity. Due to the better catalytic performance of Mn2Co1Ox and Mn3Co1Ox, it can be considered that the smaller particles and lower crystallinity provide higher catalytic activity for the SCR reaction.
NH3-TPD experiments were chosen to study the acid sites over the Mn2Co1Ox and MnOx surfaces as shown in Figure 1c. Compared with the MnOx catalyst, the Mn2Co1Ox catalyst has a larger NH3 desorption peak area, indicating that it has more acid sites, which is attributed to the introduction of Co. In this work, the Mn-Co catalyst exhibited much higher catalytic activity than MnOx. The results of the BET analysis are summarized in Table 1. It can be observed that the BET surface area and the pore volume of Mn2Co1Ox are larger than that of MnOx.
Catalyst loading is another important factor for catalytic performance. Overall, catalytic performance increased with catalyst loading and remained basically unchanged for the samples with more than 7% catalyst loading (Figure 2a). The NO conversion over Mn-Co/LDC with catalyst loading of 7% is above 95% in the temperature range of 100~200 °C. On the other hand, the filtration resistance of the catalytic ceramic filter is affected by catalyst loading. The filtration resistance increases slowly for the samples with catalyst loading of less than 7%, and increases dramatically after catalyst loading is more than 7% (Figure 2b). However, the catalytic efficiency does not significantly increase for the samples with catalyst loading >7%. Therefore, catalyst loading of 7% has a higher catalytic performance and relatively lower filtration resistance. In the dust removal performance test, the dust concentration was controlled at 5 g/m3 in feed gas. After the flue gas passed through LDC and Mn-Co/LDC, the dust concentration in outlet gas was reduced to less than 50 μg/m3. The dust removal efficiency for Mn-Co/LDC reaches 99.99%. Although the filtration resistance increases due to catalyst loading, the dust removal efficiency is not affected.
The microstructure and morphology of Mn-Co/LDC and LDC were observed by scanning electron microscope as shown in Figure 3. The surface of the ceramic fiber in LDC is smooth, and the interconnection of ceramic fibers built a large number of interconnected pores. After the catalyst was loaded, a large number of fine catalyst particles appeared on the ceramic fibers of Mn-Co/LDC. NOx and dust can be removed simultaneously by the Mn-Co/LDC ceramic filter with the combination of catalyst function and membrane separation. The chemical composition of Mn-Co/LDC was determined by EDS as listed in Table 2. The atomic ratio of Mn and Co is close to 2:1, which is consistent with the designed composition.

3.2. Improvement of H2O Resistance for Mn-Co/LDC

PTFE was selected as a surface modifier to improve the H2O resistance of Mn-Co/LDC., Mn-Co/LDC is hydrophilic with a contact angle of 0° as shown in Figure 4a. The surface polarity of Mn-Co/LDC is changed from hydrophilic to hydrophobic after surface modification (Figure 4b–d). The contact angle is 122° for 15-PTFE-Mn-Co/LDC (15% PTFE dispersion) and increases significantly to 136° for 25-PTFE-Mn-Co/LDC. However, the hydrophobicity of PTFE-Mn-Co/LDC does not improve much as the PTFE concentration increased to 35%.
Figure 5 shows an SEM image of PTFE-Mn-Co/LDC and EDS element mapping of fluorine to exhibit the distribution of PTFE on LDC. The uniform distribution of element F represents the uniform distribution of PTFE, and there is no obvious plugging of holes.
The H2O resistance of PTFE-Mn-Co/LDCs is investigated from 100 to 180 °C (Figure 6a). The catalytic performance of 15-PTFE-Mn-Co/LDC and 25-PTFE-Mn-Co/LDC is almost identical to that of Mn-Co/LDC without H2O. While the catalytic performance of 35-PTFE-Mn-Co/LDC is obviously low because the excess residue of PTFE covers the catalyst. The NO conversion over all samples reduces when there is 7% H2O in feed gas. The effect of H2O is more significant at lower temperatures and almost disappears at 180 °C. It is necessary to study the H2O resistance for the catalysts applied below 180 °C. Among PTFE-Mn-Co/LDCs, 25-PTFE-Mn-Co/LDC exhibits the lowest reduction for NO conversion and it maintains >90% NO conversion with 7% H2O at 140 °C. Therefore, 25-PTFE-Mn-Co/LDC with excellent hydrophobicity, economy and H2O resistance is selected for the later experiments.
N2 selectivity over Mn-Co/LDC and 25-PTFE-Mn-Co/LDC is determined and shown in Figure 6b. 25-PTFE-Mn-Co/LDC shows lower N2 selectivity compared with Mn-Co/LDC. It is considered that PTFE affects the adsorption of NH3 by the catalysts. The TG curves of Mn-Co/LDC and 25-PTFE-Mn-Co/LDC in air at a heating rate of 10 °C/min from 30 to 800 °C, are shown in Figure 6c. The weight loss of 25-PTFE-Mn-Co/LDC at 400–570 °C showed that PTFE was almost decomposed before 570 °C. It is confirmed that the percentage of PTFE modifier in PTFE-Mn-Co/LDC is about 3%.
The resistance to H2O 25-PTFE-Mn-Co/LDC was further tested with 5, 10 and 15% H2O at 140 °C in feed gas. When 5% H2O is introduced to feed gas, the NO conversion over 25-PTFE-Mn-Co/LDC remains 98%, while the NO conversion over Mn-Co/LDC decreases from 99.8% to 92% (Figure 7a). When the H2O content is raised to 10%, NO conversion over 25-PTFE-Mn-Co/LDC stays above 86% within 4 h, while the NO conversion over Mn-Co/LDC drops to 72%. The NO conversion returns to the initial value after removing H2O in feed gas, proving that the effect of H2O is reversible.
It is necessary to investigate the stability of the samples for low-temperature denitrification with small amounts of SO2 and high H2O content. As shown in Figure 7b, NO conversion over Mn-Co/LDC is lower than 70% under 50 ppm SO2 and 10% H2O at 140 °C. Apparently, SO2 in feed gas accelerates the deactivation of the Mn-Co/LDC catalyst. After removing SO2 and H2O, the NO conversion over Mn-Co/LDC hardly returns to the initial level. PTFE-Mn-Co/LDC shows good stability under the same test conditions and the NO conversion returns to the initial level after the removal of SO2 and H2O. Compared to other catalysts listed in Table 3, PTFE-Mn-Co/LDC maintains a higher NO conversion efficiency under the same condition of H2O content or temperature.
The resistance to SO2 and H2O of the catalyst is analyzed according to the FT-IR results of fresh and spent (tested in the presence of H2O and SO2) Mn-Co/LDC and 25-PTFE-Mn-Co/LDC samples (Figure 8a). The peaks at 1218 cm−1 and 1158 cm−1 are attributed to symmetrical and asymmetrical stretching vibrations of F-C-F in PTFE. A strong absorption peak located at 1091 cm−1 is attributed to the asymmetrical stretching vibration of the Si-O-Si bond due to the glass powder used in the preparation of ceramic filters. SO2 and H2O in feed gas will react with ammonia and cause the deposition of ammonium bisulfate during the NH3-SCR reaction, resulting in the deactivation of the catalyst. Figure 8b–e are FT-IR spectra after Gaussian fitting within 1030–1250 cm−1. Compared with the FT-IR spectra of fresh Mn-Co/LDC (Figure 8b), the FT-IR spectra of spent (tested in the presence of SO2 and H2O) Mn-Co/LDC (Figure 8c) exhibits a new band located at 1143 cm−1, which represents symmetrical stretching vibration of S = O from SO42− [37]. This phenomenon suggests there are ammonium bisulfate deposits on the surface of Mn-Co/LDC. The absence of a characteristic peak for SO42− in Figure 8e suggests that ammonium bisulfate is difficult to be deposited on the surface of PTFE-Mn-Co/LDC. Therefore, PTFE-Mn-Co/LDC exhibits superior catalytic activity for feed gas containing SO2 and H2O.

3.3. The Self-Cleaning Performance of PTFE-Mn-Co/LDC

The surface modification of PTFE also improves the stain resistance of Mn-Co/LDC. The effect of the fly ash covering and water cleaning on the filtration resistance of PTFE-Mn-Co/LDC and Mn-Co/LDC was recorded in Figure 9a. The filtration resistance increased rapidly with the experimental times and stabilized at 1600 Pa for Mn-Co/LDC, which suggested that large amounts of fly ash adhered on the surface or entered into the pores of Mn-Co/LDC. Whereas, the filtration resistance only increased by 150 Pa for PTFE-Mn-Co/LDC, indicating a superior self-cleaning effect.
The self-cleaning properties of PTFE-Mn-Co/LDC can be more visually described by a simulation experiment. The surface of PTFE-Mn-Co/LDC was covered with white Al2O3 powder (Figure 9b). After spraying with a drop of water, the surface remained in a hydrophobic state. As the water drop was rolling, the powder was absorbed by water and the surface of the PTFE-Mn-Co/LDC was cleaned. It shows an excellent self-cleaning ability of PTFE-Mn-Co/LDC. The dust on the surface of the catalyst also can be removed by water vapor. Therefore, H2O resistance and stain resistance of Mn-Co/LDC are significantly improved by PTFE hydrophobic modification.

4. Conclusions

The Mn-Co-based catalyst shows excellent NO reduction performance at low-temperature. Mn-Co/LDC with Mn/Co = 2:1 and catalyst loading of 7% shows 99% NO conversion from 100 to 180 °C. After surface hydrophobic modification by PTFE dispersion with 25% concentration, the contact angle of PTFE-Mn-Co/LDC increases to 136°. The resistance to H2O of Mn-Co/LDC is significantly improved after surface hydrophobic modification. PTFE-Mn-Co/LDC also shows better resistance to SO2 due to the sulfate-resistant deposition provided by PTFE. Additionally, PTFE-Mn-Co/LDC possesses excellent self-cleaning performance owing to the hydrophobic surface. Therefore, this approach can enhance the adaptability of catalytic ceramic filter elements for the coprocessing of NOx and dust at low-temperature.

Author Contributions

Conceptualization, J.J. and H.Z.; methodology, T.Z.; software, X.X.; validation, K.L. and T.Z.; formal analysis, T.Z. and C.H.; investigation, K.L. and T.Z.; resources, J.J.; data curation, K.L. and T.Z.; writing—original draft preparation, K.L.; writing—review and editing, H.Z.; visualization, X.X. and C.H.; supervision, J.J. and H.Z.; project administration, J.J. and H.Z.; funding acquisition, J.J. and H.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work has received financial support from the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data that support the findings of this study are included within the article.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Cramer, A.J.; Cole, J.M. Removal or storage of environmental pollutants and alternative fuel sources with inorganic adsorbents via host-guest encapsulation. J. Mater. Chem. A 2017, 5, 10746–10771. [Google Scholar] [CrossRef] [Green Version]
  2. Chen, Y.S.; Hsiau, S.S.; Smid, J.; Wu, J.F.; Ma, S.M. Removal of dust particles from fuel gas using a moving granular bed filter. Fuel 2016, 182, 174–187. [Google Scholar] [CrossRef]
  3. Hu, J.; Zhong, Z.X.; Zhang, F.; Xing, W.H.; Low, Z.X.; Fan, Y.Q. Coating of ZnO nanoparticles onto the inner pore channel surface of SiC foam to fabricate a novel antibacterial air filter material. Ceram. Int. 2015, 41, 7080–7090. [Google Scholar] [CrossRef]
  4. Hashim, S.M.; Mohamed, A.R.; Bhatia, S. Catalytic inorganic membrane reactors: Present research and future prospects. Rev. Chem. Eng. 2011, 27, 157–178. [Google Scholar] [CrossRef]
  5. Kim, Y.G.; Choi, J.H.; Yu, L.; Bak, Y.C. Modification of V2O5-WO3/TiO2 Catalysts Supported on SiC Filter for NO Reduction at Low Temperature. Solid State Phenom. 2007, 124–126, 1713–1716. [Google Scholar] [CrossRef]
  6. Cho, E.H.; Suh, K.S.; Shin, M.C.; Shin, H.G.; Lee, H.S.; Niihara, K. Thermal and chemical degradation behavior of a catalytic ceramic filter for dust/NOx removal. J. Ceram. Process. Res. 2009, 10, 73–76. [Google Scholar] [CrossRef]
  7. Heidenreich, S.; Nacken, M.; Hackel, M.; Schaub, G. Catalytic filter elements for combined particle separation and nitrogen oxides removal from gas streams. Powder Technol. 2008, 180, 86–90. [Google Scholar] [CrossRef]
  8. Li, J.H.; Chang, H.Z.; Ma, L.; Hao, J.M.; Yang, R.T. Low-temperature selective catalytic reduction of NOx with NH3 over metal oxide and zeolite catalysts-A review. Catal. Today 2011, 175, 147–156. [Google Scholar] [CrossRef]
  9. Kim, J.H.; Choi, J.H.; Phule, A.D. Development of high performance catalytic filter of V2O5-WO3TiO2 supported-SiC for NOx reduction. Powder Technol. 2018, 327, 282–290. [Google Scholar] [CrossRef]
  10. Nacken, M.; Heidenreich, S.; Hackel, M.; Schaub, G. Catalytic activation of ceramic filter elements for combined particle separation, NOx removal and VOC total oxidation. Appl. Catal. B 2007, 70, 370–376. [Google Scholar] [CrossRef]
  11. Gao, F.Y.; Tang, X.L.; Yi, H.H.; Li, J.Y.; Zhao, S.Z.; Wang, J.G.; Chu, C.; Li, C.L. Promotional mechanisms of activity and SO2 tolerance of Co- or Ni-doped MnOx-CeO2 catalysts for SCR of NOx with NH3 at low temperature. Chem. Eng. J. 2017, 317, 20–31. [Google Scholar] [CrossRef]
  12. Wu, R.; Li, L.; Zhang, N.; He, J.; Song, L.; Zhang, G.; Zhang, Z.; He, H. Enhancement of low-temperature NH3-SCR catalytic activity and H2O & SO2 resistance over commercial V2O5-MoO3/TiO2 catalyst by high shear-induced doping of expanded graphite. Catal. Today 2021, 376, 302–310. [Google Scholar] [CrossRef]
  13. Yang, S.J.; Liu, C.X.; Chang, H.Z.; Ma, L.; Qu, Z.; Yan, N.Q.; Wang, C.Z.; Li, J.H. Improvement of the Activity of gamma-Fe2O3 for the Selective Catalytic Reduction of NO with NH3 at High Temperatures: NO Reduction versus NH3 Oxidization. Ind. Eng. Chem. Res. 2013, 52, 5601–5610. [Google Scholar] [CrossRef]
  14. Zhang, N.N.; Xin, Y.; Wang, X.; Shao, M.F.; Li, Q.; Ma, X.C.; Qi, Y.X.; Zheng, L.R.; Zhang, Z.L. Iron-niobium composite oxides for selective catalytic reduction of NO with NH3. Catal. Commun. 2017, 97, 111–115. [Google Scholar] [CrossRef]
  15. Chitsazi, H.; Zhang, N.; Li, L.; Liu, X.; Wu, R.; He, J.; Song, L.; He, H. In-situ DRIFT assessment on strengthening effect of cerium over FeOx/TiO2 catalyst for selective catalytic reduction of NOx with NH3. J. Rare Earths 2021, 39, 526–531. [Google Scholar] [CrossRef]
  16. Arfaoui, J.; Ghorbel, A.; Petitto, C.; Delahay, G. New Mn-TiO2 aerogel catalysts for the low-temperature selective catalytic reduction of NOx. J. Sol.-Gel. Sci. Technol. 2021, 97, 302–310. [Google Scholar] [CrossRef]
  17. Ng, D.; Acharya, D.; Wang, X.D.; Easton, C.D.; Wang, J.X.; Xie, Z.L. Low temperature SCR of NOx over Mn/Fe mixed oxides catalyst: Comparison of synthesis methods. J. Chem. Technol. Biotechnol. 2021, 96, 2681–2695. [Google Scholar] [CrossRef]
  18. Zabihi, V.; Eikani, M.H.; Ardjmand, M.; Latifi, S.M.; Salehirad, A. Selective catalytic reduction of NO by Fe-Mn nanocatalysts: Effect of structure type. Environ. Sci. Pollut. Res. 2021, 28, 39159–39167. [Google Scholar] [CrossRef]
  19. Yang, B.; Zheng, D.H.; Shen, Y.S.; Qiu, Y.S.; Li, B.; Zeng, Y.W.; Shen, S.B.; Zhu, S.M. Influencing factors on low-temperature deNO(x) performance of Mn-La-Ce-Ni-O-x/PPS catalytic filters applied for cement kiln. J. Ind. Eng. Chem. 2015, 24, 148–152. [Google Scholar] [CrossRef]
  20. Zhang, N.; Li, L.; Guo, Y.; He, J.; Wu, R.; Song, L.; Zhang, G.; Zhao, J.; Wang, D.; He, H. A MnO2-based catalyst with H2O resistance for NH3-SCR: Study of catalytic activity and reactants-H2O competitive adsorption. Appl. Catal. B 2020, 270, 118860. [Google Scholar] [CrossRef]
  21. Urbanas, D.; Baltrenaite-Gediene, E. Selective Catalytic Reduction of NO by NH3 over Mn-Cu Oxide Catalysts Supported by Highly Porous Silica Gel Powder: Comparative Investigation of Six Different Preparation Methods. Catalysts 2021, 11, 702. [Google Scholar] [CrossRef]
  22. Gao, E.H.; Pan, H.; Zhang, W.; Li, Y.N.; Cao, G.H.; Bernards, M.T.; He, Y.; Shi, Y. Insights on the mechanism of enhanced selective catalytic reduction of NO with NH3 over Zr-doped MnCr2O4: A combination of in situ DRIFTS and DFT. Chem. Eng. J. 2020, 386, 123956. [Google Scholar] [CrossRef]
  23. Li, W.M.; Liu, H.D.; Chen, Y.F. Fabrication of MnOx-CeO2-Based Catalytic Filters and Their Application in Low-Temperature Selective Catalytic Reduction of NO with NH3. Ind. Eng. Chem. Res. 2020, 59, 12657–12665. [Google Scholar] [CrossRef]
  24. Fang, Q.; Zhu, B.; Sun, Y.; Song, W.; Xu, M. Effects of alkali metal poisoning and cobalt modification on the NH3 adsorption behavior on the MnxOy/Ni (1 1 1) surface: A DFT-D study. Appl. Surf. Sci. 2020, 509, 144901. [Google Scholar] [CrossRef]
  25. Zhang, N.; He, H.; Wang, D.; Li, Y. Challenges and opportunities for manganese oxides in low-temperature selective catalytic reduction of NOx with NH3: H2O resistance ability. J. Solid State Chem. 2020, 289, 121464. [Google Scholar] [CrossRef]
  26. Pan, S.W.; Luo, H.C.; Li, L.; Wei, Z.L.; Huang, B.C. H2O and SO2 deactivation mechanism of MnOx/MWCNTs for low-temperature SCR of NOx with NH3. J. Mol. Catal. A Chem. 2013, 377, 154–161. [Google Scholar] [CrossRef]
  27. Chitsazi, H.; Wu, R.; Zhang, N.; He, J.; Zhang, G.; He, H. Enhancement of low-temperature NH3-SCR catalytic activity and H2O resistance ability over MnOx/TiO2 catalyst by expanded graphite. Catal. Lett. 2020, 150, 2688–2694. [Google Scholar] [CrossRef]
  28. Zhang, G.D.; Huang, X.S.; Tang, Z.C. Enhancing Water Resistance of a Mn-Based Catalyst for Low Temperature Selective Catalytic Reduction Reaction by Modifying Super Hydrophobic Layers. ACS Appl. Mater. Interfaces 2019, 11, 36598–36606. [Google Scholar] [CrossRef]
  29. Hu, S.; Xiao, C.J.; Zhu, Z.L.; Luo, S.Z.; Wang, C. Catalytic Activity of Hydrophobic Pt/C/PTFE Catalysts of Different PTFE Content for Hydrogen-Water Liquid Exchange Reaction. At. Energy Sci. Technol. 2007, 41, 527–532. [Google Scholar] [CrossRef]
  30. Ghosh, S.K.; Miller, C.; Perez, G.; Carlton, H.; Huitink, D.; Beckford, S.; Zou, M. Effect of Cu nanoparticles on the tribological performance of polydopamine plus polytetrafluoroethylene coatings in oil-lubricated condition. Appl. Surf. Sci. 2021, 565, 150525. [Google Scholar] [CrossRef]
  31. Yoon, S.; Sim, H.M.; Cho, S.; Ko, H.; Park, Y.; Kim, Y.; Kim, H.K. Highly Stretchable, Conductive Polymer Electrodes with a Mixed AgPdCu and PTFE Network Interlayer for Stretchable Electronics. Adv. Mater. Interfaces 2021, 8, 2001500. [Google Scholar] [CrossRef]
  32. Zhang, N.Q.; Li, L.C.; Zhang, B.B.; Sun, Y.M.; Song, L.Y.; Wu, R.; He, H. Polytetrafluoroethylene modifying: A low cost and easy way to improve the H2O resistance ability over MnOx for low-temperature NH3-SCR. J. Environ. Chem. Eng. 2019, 7, 103044. [Google Scholar] [CrossRef]
  33. Zhao, L.; Li, K.; Wu, R.A.; Zhang, H.; Jin, J. Catalytic filter for the removal of dust and NOx at low temperature. Mater. Res. Express. 2020, 7, 125502. [Google Scholar] [CrossRef]
  34. Song, X.Y.; Jian, B.H.; Jin, J. Preparation of porous ceramic membrane for gas-solid separation. Ceram. Int. 2018, 44, 20361–20366. [Google Scholar] [CrossRef]
  35. Kim, T.I.; Tahk, D.; Lee, H.H. Wettability-controllable super water- and moderately oil-repellent surface fabricated by wet chemical etching. Langmuir 2009, 25, 6576–6579. [Google Scholar] [CrossRef] [PubMed]
  36. Shen, B.X.; Liu, T.; Zhao, N.; Yang, X.Y.; Deng, L.D. Iron-doped Mn-Ce/TiO2 catalyst for low temperature selective catalytic reduction of NO with NH3. J. Environ. Sci. 2010, 22, 1447–1454. [Google Scholar] [CrossRef]
  37. Ye, D.; Qu, R.; Song, H.; Gao, X.; Luo, Z.; Ni, M.; Cen, K. New insights into the various decomposition and reactivity behaviors of NH4HSO4 with NO on V2O5/TiO2 catalyst surfaces. Chem. Eng. J. 2016, 283, 846–854. [Google Scholar] [CrossRef]
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Figure 1. (a) NO reduction performance over MnaCobOx/LDC, (b) XRD pattern of MnaCobOx catalyst, (c) NH3-TPD profiles of Mn2Co1Ox and MnOx.
Figure 1. (a) NO reduction performance over MnaCobOx/LDC, (b) XRD pattern of MnaCobOx catalyst, (c) NH3-TPD profiles of Mn2Co1Ox and MnOx.
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Figure 2. (a) NO reduction performance on Mn-Co/LDC with the catalyst loading of 5–10%, (b) filtration resistance of Mn-Co/LDC with catalyst loading of 5–10% (face velocity = 1.5 m/min).
Figure 2. (a) NO reduction performance on Mn-Co/LDC with the catalyst loading of 5–10%, (b) filtration resistance of Mn-Co/LDC with catalyst loading of 5–10% (face velocity = 1.5 m/min).
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Figure 3. SEM images of (a,b) LDC and (c,d) 7% catalytic loading of Mn-Co/LDC.
Figure 3. SEM images of (a,b) LDC and (c,d) 7% catalytic loading of Mn-Co/LDC.
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Figure 4. The images and contact angles of (a) Mn-Co/LDC, (b–d) PTFE-Mn-Co/LDCs.
Figure 4. The images and contact angles of (a) Mn-Co/LDC, (b–d) PTFE-Mn-Co/LDCs.
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Figure 5. (a) SEM image and (b) EDS mapping of F element for PTFE-Mn-Co/LDC.
Figure 5. (a) SEM image and (b) EDS mapping of F element for PTFE-Mn-Co/LDC.
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Figure 6. (a) Mn-Co/LDC and PTFE-Mn-Co/LDCs NO conversion with 0% H2O (solid Line) and 7% H2O (dashed line). (b) N2 selectivity over Mn-Co/LDC and 25-PTFE-Mn-Co/LDC, (c) TG curves of Mn-Co/LDC and 25-PTFE-Mn-Co/LDC.
Figure 6. (a) Mn-Co/LDC and PTFE-Mn-Co/LDCs NO conversion with 0% H2O (solid Line) and 7% H2O (dashed line). (b) N2 selectivity over Mn-Co/LDC and 25-PTFE-Mn-Co/LDC, (c) TG curves of Mn-Co/LDC and 25-PTFE-Mn-Co/LDC.
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Figure 7. (a) Mn-Co/LDC and 25-PTFE-Mn-Co/LDC NO conversion with 5, 10 and 15% H2O at 140 °C. (b) Mn-Co/LDC and 25-PTFE-Mn-Co/LDC NO conversion with 50 ppm SO2 and 10% H2O (140 °C, NH3 = NO = 500 ppm).
Figure 7. (a) Mn-Co/LDC and 25-PTFE-Mn-Co/LDC NO conversion with 5, 10 and 15% H2O at 140 °C. (b) Mn-Co/LDC and 25-PTFE-Mn-Co/LDC NO conversion with 50 ppm SO2 and 10% H2O (140 °C, NH3 = NO = 500 ppm).
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Figure 8. (a) The FT-IR of samples in fresh and tested with 50 ppm SO2 and 10 % H2O. (b–e) The Gaussian fitting curves of FT-IR between 1030 and 1250 cm−1.
Figure 8. (a) The FT-IR of samples in fresh and tested with 50 ppm SO2 and 10 % H2O. (b–e) The Gaussian fitting curves of FT-IR between 1030 and 1250 cm−1.
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Figure 9. (a) Effect of fly ash covering and water cleaning on the filtration resistance of PTFE-Mn-Co/LDC and Mn-Co/LDC. (b) The pictures of self-cleaning performance simulation experiment on PTFE-Mn-Co/LDC.
Figure 9. (a) Effect of fly ash covering and water cleaning on the filtration resistance of PTFE-Mn-Co/LDC and Mn-Co/LDC. (b) The pictures of self-cleaning performance simulation experiment on PTFE-Mn-Co/LDC.
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Table
Table 1. Textural properties of Mn2Co1Ox and MnOx.
Table 1. Textural properties of Mn2Co1Ox and MnOx.
CatalystsSBET (m2 g−1) aPore Volume (cm3 g−1) bPore Diameter (nm) c
Mn2Co1Ox32.640.076.67
MnOx21.160.057.34
a BET surface area. b BJH desorption pore volume. c BJH desorption pore diameter.
Table
Table 2. The chemical composition of Mn-Co/LDC.
Table 2. The chemical composition of Mn-Co/LDC.
ElementO KAl KSi KMn KCo KTotal
Element wt.%39.0311.8828.2113.197.69100
Atom %57.3310.3523.615.643.07100
Table
Table 3. NO conversion of representative catalysts with H2O.
Table 3. NO conversion of representative catalysts with H2O.
CatalystsEvaluation ConditionsTemperature/°CNO ConversionReferences
PTFE-Mn-Co/LDC[NO] = [NH3] =500 ppm, [O2] =6%, [H2O] = 5%14098%This work
PTFE-Mn-Co/LDC[NO] = [NH3] =500 ppm, [O2] =6%, [H2O] = 10%14086%This work
Mn-Ce/TiO2[NO] = [NH3] =600 ppm, [O2] =3%, [H2O] = 3%14057%[36]
Co1Mn4Ce5Ox[NO] = [NH3] =500 ppm, [O2] =5%, [H2O] = 10%17575%[11]
MnO2-PTFE[NO] = [NH3] =1000 ppm [O2] =6%, [H2O] =10%, [SO2] = 50 ppm18087%[32]
OMS-2[NO] = [NH3] =500 ppm, [O2] =5%, [H2O] =10%15055%[28]
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Li, K.; Zhou, T.; Xu, X.; Han, C.; Zhang, H.; Jin, J. PTFE-Modified Mn-Co-Based Catalytic Ceramic Filters with H2O Resistance for Low-Temperature NH3-SCR. Sustainability 2022, 14, 5353. https://doi.org/10.3390/su14095353

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Li K, Zhou T, Xu X, Han C, Zhang H, Jin J. PTFE-Modified Mn-Co-Based Catalytic Ceramic Filters with H2O Resistance for Low-Temperature NH3-SCR. Sustainability. 2022; 14(9):5353. https://doi.org/10.3390/su14095353

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Li, Kun, Tao Zhou, Xinqiang Xu, Changye Han, Hua Zhang, and Jiang Jin. 2022. "PTFE-Modified Mn-Co-Based Catalytic Ceramic Filters with H2O Resistance for Low-Temperature NH3-SCR" Sustainability 14, no. 9: 5353. https://doi.org/10.3390/su14095353

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