Next Article in Journal
The Effect of Ni-Modified LSFCO Promoting Layer on the Gas Produced through Co-Electrolysis of CO2 and H2O at Intermediate Temperatures
Next Article in Special Issue
Iron-Based Composite Oxide Catalysts Tuned by CTAB Exhibit Superior NH3–SCR Performance
Previous Article in Journal
Photocatalytic Pretreatment of Commercial Lignin Using TiO2-ZnO Nanocomposite-Derived Advanced Oxidation Processes for Methane Production Synergy in Lab Scale Continuous Reactors
Previous Article in Special Issue
High Resistance of SO2 and H2O over Monolithic Mn-Fe-Ce-Al-O Catalyst for Low Temperature NH3-SCR
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 11
Issue 1
10.3390/catal11010055
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Novel Preparation of Cu and Fe Zirconia Supported Catalysts for Selective Catalytic Reduction of NO with NH3

by
Katarzyna Świrk
1,*,†,
Ye Wang
2,3,†,
Changwei Hu
2,4,*,
Li Li
4,
Patrick Da Costa
3,* and
Gérard Delahay
1
1
Institut Charles Gerhardt Montpellier, Université de Montpellier, ENSCM (MACS), CNRS, 34296 Montpellier, France
2
College of Chemical Engineering, Sichuan University, Chengdu 610065, China
3
Institut Jean Le Rond d’Alembert, Sorbonne Université, CNRS, 78210 Saint Cyr l’Ecole, France
4
Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, China
*
Authors to whom correspondence should be addressed.
†
K.Ś. and Y.W. contributed equally.
Catalysts 2021, 11(1), 55; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010055
Submission received: 26 November 2020 / Revised: 26 December 2020 / Accepted: 30 December 2020 / Published: 2 January 2021
(This article belongs to the Special Issue Selective Catalytic Reduction of NOx by NH3)
Browse Figures
Versions Notes

Abstract

:
Copper and iron promoted ZrO2 catalysts were prepared by one-pot synthesis using urea. The studied catalysts were characterized by XRD, N2 physisorption, XPS, NH3-TPD, and tested in the selective catalytic reduction of NO with NH3 (NH3-SCR) in the absence and presence of water vapor under the experimental conditions representative of exhaust gases from stationary sources. The influence of SO2 on catalytic performance was also investigated. Among the studied catalysts, the Fe-Zr sample showed the most promising results in NH3-SCR, being active and highly selective to N2. The addition of SO2 markedly improved NO and NH3 conversions during NH3-SCR in the presence of H2O. The improvement in acidic surface properties is believed to be the cause.

Graphical Abstract

1. Introduction

Nitrogen oxides (NOx: NO, NO2) are known to be major pollutants of the atmosphere. Their emission mainly arises from stationary (fossil fuels combustion) and mobile sources (vehicles), contributing to the formation of photochemical smog, acid rains, and ozone depletion. Different technologies have been used to reduce NOx emission [1]. Among them, direct decomposition of NOx into N2 and O2 is ideal as it only requires a simple contact with the surface of a catalyst. However, the formed oxygen atoms may be strongly adsorbed and cause a rapid deactivation of the catalytic material [2,3]. The second type of technology used for mobile sources is NOx Storage/Reduction (NSR) or NOx trap [4]. These approaches, however, are limited due to the hydrocarbon and CO2 penalties caused by cyclic lean-fuel/rich-fuel conditions [5].
The last known technology for NOx emission control is the selective catalytic reduction (SCR), including HCs, CO, and H2-SCR for automotive pollution processes [6,7]. One of the well-established post-combustion technologies of NOx reduction is the selective catalytic reduction of NOx with ammonia (NH3-SCR). The process has been introduced in the late 1970s, being widely commercialized technology for NOx removal from flue gases from coal-fired power plants and other industrial facilities [8,9]. The standard reaction equation for NH3-SCR, involving only NO, is given by:
4 NO + 4 NH3 + O2 → 4 N2 + 6 H2O
With an equimolar amount of NO and NO2, the reaction called fast SCR reaction is much faster, and the reaction equation becomes:
2NO + 2 NO2 + 4 NH3 → 4 N2 + 6 H2O
On the other hand, with pure NO2 the NH3-SCR reaction is the slowest and can be presented by the following equation:
6 NO2 + 8 NH3 → 7 N2 + 12 H2O
The conventional catalysts are V2O5–WO3(MoO3)/TiO2 and Cu, Fe-zeolites [10,11]. In the former, V2O5 represents active phase, whereas WO3 and MoO3 increase the temperature window of the SCR reaction and improve the mechanical strength of the catalysts [12]. However, the main drawback of V2O5–WO3(MoO3)/TiO2 is a narrow operating temperature window (300–400 °C), sublimation of vanadium species at high temperatures, and high oxidation of SO2 to SO3 leading to a decrease of NOx conversion at 400 °C [10]. On the other hand, Cu and Fe zeolites show high activity in a low-temperature window and good hydrothermal resistance [11,13,14]. Both copper ions (Cu2+ and/or Cu+) and iron ions (Fe3+) play an important role of active sites in the reaction of NH3-SCR. Nevertheless, the application of Cu or Fe zeolites is still challenging as in most cases they are prone to be extensively poisoned by SO2 [15].
Over the past years, various novel catalysts for NOx reduction were described in the literature. Among them, zirconia-supported catalysts were found attractive due to the high thermal stability, high low-temperature activity and durability, as well as enhanced resistance to SO2 and H2O [16,17,18,19,20,21]. Cu/ZrO2 and Cu/ZrO2(SO42−) were found very promising in selective catalytic reduction by n-decane [22,23,24] or propene [25], and finally in NH3-SCR [26,27]. Pietrogiacomi et al. [26] prepared the zirconia support by hydrolysis of zirconium oxychloride with ammonia. The obtained carriers were impregnated with aqueous solutions of CuSO4 or Cu(NO3)2. Some portion of the latter was additionally sulphurized via gas phase (2770 ppm SO2 and 1%O2, in He). The authors found that impregnation with CuSO4 or sulphation via gas-phase yielded nearly identical catalysts. CuSO4/ZrO2 were much more selective than the relevant unsulphated CuOx/ZrO2 to NH3-SCR. However, sulphated ZrO2 catalysts were only slightly more active than unsulphated ZrO2.
Iron modified ZrO2 has been also studied extensively in other catalytic processes [25,28]. According to Apostolescu et al. [18], tetragonal zirconia was the most effective support for Fe catalyst used in NH3-SCR when compared to the metal deposited on MgAl2O4, SiO2, or TiO2. For Fe/ZrO2 prepared by sol-gel technique, Navío et al. [29] demonstrated that Fe loading equal or higher than 3 wt% allows to stabilize the zirconia tetragonal phase due to the high solubility of Fe3+ in the ZrO2 matrix. By studying NH3-SCR of NO over Mn-Fe supported catalysts, López-Hernández et al. [30] showed that acidity is necessary to catalyze the reaction, but not sufficient to obtain the most effective material. The authors showed a significant relationship between SCR activity at low temperatures and surface area through the better iron dispersion for the supports with Lewis acid properties (zirconia, alumina and titania). Since iron oxide also possesses Lewis acidity, resulting catalysts are in principle less sensitive to deactivation of the Brønsted acid sites. Considering this point, Kustov et al. [31] studied the effect of potassium on vanadium, copper, and iron oxides supported on sulphated zirconia (monoclinic), where a slight increase in alkali resistance was found compared to the vanadium.
Indovina et al. [32] examined FeOx/sulphated-ZrO2 and FeOx/ZrO2 prepared by impregnation of different Fe precursors. The authors have found that iron species were much less reducible in FeOx/sulphated-ZrO2 than in FeOx/ZrO2. Their lower reducibility explained why FeOx/sulphated-ZrO2 samples may achieve higher selectivity for the selective catalytic reduction of NO with NH3.
Fan et al. [33] investigated sulphate iron-based catalysts prepared by impregnation methods through changing the loading order of Fe2O3 and SO42− on ZrO2 carrier. The activities of sulphated Fe-based catalysts improved significantly compared to the Fe/Zr catalyst, when tested in the temperature range of 250–500 °C. The authors showed that sulphate supplied higher number of acid sites, which could adsorb more NH3 species that can react with gaseous NO + O2. Recently, Liu et al. [34] investigated the selective catalytic reduction of NOx with ammonia over sulphated iron-based catalysts in using different loadings of Fe3+ and SO42− on zirconia support. Their results indicated that the interaction between Fe3+ and SO42− can have an effect on the redox ability, acid sites, and adsorption of NOx and NH3. By increasing the content of Fe3+, the redox activity of the catalyst and the adsorption of ammonia improved at medium and low temperatures, whereas at higher temperatures, the increase in Fe3+ species led to the decrease in the conversion of NOx due to the enhancement of the NH3 oxidation.
In this work, a novel one-pot synthesis was proposed for the preparation of zirconia-supported Cu and Fe catalysts. The catalysts were tested in selective catalytic reduction of NO with NH3 in the presence and absence of water vapor. Physicochemical properties of catalysts were examined by N2 physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption of NH3 (NH3-TPD). The characterized materials were tested in NH3-SCR (with or without H2O). The activity changes during SO2 feeding (in situ sulphation) were studied at 450 °C. Additionally, the activity towards NH3-SCO (with or without H2O) was also investigated. The importance of support morphology and phase was highlighted.

2. Results and Discussion

2.1. Catalysts Characterization

2.1.1. Structural and Textural Properties of ZrO2 Supported Catalysts

The structure of the studied samples was determined by XRD, as presented in Figure 1 and Table 1. The reflections at 2θ ca. 30.1, 35.2, 60.4, 62.9, 74.8, 81.9, and 85.6° were attributed to the tetragonal ZrO2 (t-ZrO2 indication) [35,36,37,38]. In all studied catalysts, only ZrO2 diffraction peaks were observed. The absence of diffraction peaks attributed to iron or copper species suggests their good dispersion or insertion into the skeleton of ZrO2 [39,40]. The latter can be supported by a small shift to higher Bragg angles observed for Cu-Zr (30.376°) and Fe-Zr (30.349°) catalysts, compared to the ZrO2 support (30.192°). Moreover, the d-spacing decreased from 2.9576 Å (ZrO2) to 2.9402 Å (Cu-Zr) or 2.9427 Å (Fe-Zr). Generally, the ionic radii are influenced by coordination number and valence. Shannon [41] found a correlation between the coordination number and the ionic radius. The ionic radius of Zr4+ in ZrO2 (0.86 Å) is higher than that of Fe3+ in Fe2O3 (0.69 Å) or Cu2+ in CuO (0.60 Å) [42]. Probably some Zr4+ ions were substituted by Cu2+ or Fe3+ to form CuO−ZrO2 or Fe2O3-ZrO2 solid solutions in the lattice sites. This could be a consequence of the shrink of the lattice parameter [43], which is in line with the XRD results. The shift towards higher Bragg angles was more pronounced for the Cu-Zr catalyst when compared to the Fe-Zr. The crystallite size of ZrO2 was calculated by the Williamson and Hall method [44,45]. One can note that the crystallite size of ZrO2 decreased, from 13.7 nm to 11.3 and 8.8 nm for Cu-Zr and Fe-Zr catalysts, respectively.
N2 physisorption was employed to determine the textural properties of the synthesized catalysts. The analysis was performed for the calcined materials. The samples were found mesoporous with the Barrett−Joyner−Halenda (BJH) mesopore volume ranged from 0.12 to 0.06 cm3/g, average pore size of 3.3–5 nm, and the surface area from 81 to 139 m2/g. These textural parameters decreased and increased with metal modification, meaning that presence of Cu and Fe led to the enhancement of specific surface area with formation of smaller mesopores with less volume.

2.1.2. Acidic Properties of ZrO2 Supported Catalysts

The total acidity of the studied catalysts was evaluated by NH3 temperature programmed desorption (NH3-TPD). Figure 2 presents the desorption curves for the studied catalysts. All samples showed a wide NH3 desorption profiles between 100 and 550 °C, arising from weak (ca. 200 °C), medium (ca. 300–400 °C), and strong (T > 400 °C) acid sites [46,47]. The modification of ZrO2 with copper and iron influenced the acidic properties by offering new weak and medium acid sites. Accordingly, the total acidity increased for Cu- and Fe-containing samples in contrast to the unmodified support. These observations are in line with the previously published reports on Cu/ZrO2 and Fe/ZrO2 materials. Pietrogiacomi et al. [26] reported higher total amount of desorbed ammonia for ZCu2.5 sample than for ZrO2 (0.5 vs. 0.2 nm−1). Ismail et al. [28] observed the formation of new acidic sites on ZrO2 surface due to the Fe addition (1.25, 2.5, 5, and 10 wt%). The authors, however, reported increasing intensities of the desorption profiles in the wide-ranging temperature window (from 200 to 500 °C). In the other study of these authors [46], the modification with iron led to the formation of new strong acid sites only (T > 400 °C) in comparison to the acid sites recorded for pure zirconia.

2.1.3. Surface Properties of ZrO2 Supported Catalysts

The surface composition of the calcined samples was analyzed by XPS. Figure 3A–D present the obtained spectra for O 1s, Zr 3d, Fe 2p, and Cu 2p. The percentage values of the elements are listed in Table 2. ZrO2 support and Cu-Zr catalyst showed similar content of Zr species on the surface, whereas the percentage of Zr species decreased from 66.8 wt% (ZrO2 support) to 64.4 wt% for Fe-Zr. The content of surface Cu species is about 2.2 wt%, which is lower than the assumed content (3 wt%). One can assume that part of Cu species could exist in the framework of ZrO2 or in the bulk. On the contrary, the percentage of Fe species is 3.2 wt%, indicating that more Fe species are formed on the surface than the interior of ZrO2 catalyst. Thus, the higher content of surface Fe species may contribute to increased activity in NH3-SCR of NO into N2. Besides, the O 1s curve was resolved into three peaks, which are attributed to lattice oxygen (O2−), carbonate species (CO32−) and hydroxyl species (OH−) [43,48]. The Zr 3d was deconvoluted into Zr3+ and Zr4+ species as reported elsewhere [49]. The content of each deconvoluted peak is listed in Table 2. The peak of O 1s on Fe-Zr catalyst shifts to lower binding energy in contrast to ZrO2 support and Cu-Zr catalyst. There are two possible reasons of this observation: (i) higher content of lattice oxygen species on Fe-Zr catalyst, or (ii) less interaction between O2− species and Fe due to an exposure of Fe2O3 and/or FeO species on the surface. Similar results were reported in literature [48,50]. Moreover, in our materials the content of Zr4+ species decreased from 62.5% to 57.2% and 4.7% by introduction of Cu or Fe, respectively, indicating that the presence of Cu or Fe results in higher content of Zr3+ species on the catalysts. This effect was more pronounced for Fe-Zr catalyst showing 95.3% of Zr3+ species. It additionally implies that Cu or Fe could promote the formation of Zr species with lower valence value. Furthermore, according to Zhao et al. [48], the curve of Fe 2p and Cu 2p are resolved to Fe2+ and Fe3+ species, and Cu+ and Cu2+ species, respectively. In our study, the ratio of Fe2+/Fe3+ is 1.33, and the Cu+/Cu2+ is 3.84. This indicates that more Fe species are present in higher valence state on Fe-Zr catalyst, corresponding to higher content of Zr3+ species. Moreover, recently on functionalized iron hydroxyapatite catalysts it was clearly shown that the presence of Fe3+ highly dispersed on the surface led to a high selectivity to N2, a satisfactory activity in a wide temperature window [41] and improved catalytic activity [34].
The surface composition of the calcined samples was analyzed by XPS. Figure 3A–D present the obtained spectra for O 1s, Zr 3d, Fe 2p, and Cu 2p. The percentage values of the elements are listed in Table 2. ZrO2 support and Cu-Zr catalyst showed similar content of Zr species on the surface, whereas the percentage of Zr species decreased from 66.8 wt% (ZrO2 support) to 64.4 wt% for Fe-Zr. The content of surface Cu species is about 2.2 wt%, which is lower than the assumed content (3 wt%). One can assume that part of Cu species could exist in the framework of ZrO2 or in the bulk. On the contrary, the percentage of Fe species is 3.2 wt%, indicating that more Fe species are formed on the surface than the interior of ZrO2 catalyst. Thus, the higher content of surface Fe species may contribute to increased activity in NH3-SCR of NO into N2. Besides, the O 1s curve was resolved into three peaks, which are attributed to lattice oxygen (O2−), carbonate species (CO32−) and hydroxyl species (OH−) [43,48]. The Zr 3d was deconvoluted into Zr3+ and Zr4+ species as reported elsewhere [49]. The content of each deconvoluted peak is listed in Table 2. The peak of O 1s on Fe-Zr catalyst shifts to lower binding energy in contrast to ZrO2 support and Cu-Zr catalyst. There are two possible reasons of this observation: (i) higher content of lattice oxygen species on Fe-Zr catalyst, or (ii) less interaction between O2− species and Fe due to an exposure of Fe2O3 and/or FeO species on the surface. Similar results were reported in literature [48,50]. Moreover, in our materials the content of Zr4+ species decreased from 62.5% to 57.2% and 4.7% by introduction of Cu or Fe, respectively, indicating that the presence of Cu or Fe results in higher content of Zr3+ species on the catalysts. This effect was more pronounced for Fe-Zr catalyst showing 95.3% of Zr3+ species. It additionally implies that Cu or Fe could promote the formation of Zr species with lower valence value. Furthermore, according to Zhao et al. [48], the curve of Fe 2p and Cu 2p are resolved to Fe2+ and Fe3+ species, and Cu+ and Cu2+ species, respectively. In our study, the ratio of Fe2+/Fe3+ is 1.33, and the Cu+/Cu2+ is 3.84. This indicates that more Fe species are present in higher valence state on Fe-Zr catalyst, corresponding to higher content of Zr3+ species. Moreover, recently on functionalized iron hydroxyapatite catalysts it was clearly shown that the presence of Fe3+ highly dispersed on the surface led to a high selectivity to N2, a satisfactory activity in a wide temperature window [41] and improved catalytic activity [34].

2.2. Catalytic Results

2.2.1. NH3-SCR of NO in the Absence and Presence of Water Vapor

Figure 4 shows the catalytic performance of Cu-Zr and Fe-Zr catalysts and the support in NH3-SCR of NO as function of temperature. The tests were performed in the presence (3.5 vol%) and in absence of water vapor.
Figure 4A,B presents catalytic results of Cu-Zr catalyst. The catalyst revealed maximum NO conversion of 85% in the absence, and 40% in the presence of H2O at 450 °C. In the former conditions, the obtained conversions were two times higher than those observed by Pietrogiacomi et al. [27] (700 ppm NO, 700 ppm NH3, 36,000 ppm O2, balance He, GHSV = 105 h−1) on impregnated Cu/ZrO2 catalysts, which clearly shows that the newly used synthesis would be a good alternative for such type of catalysts. Above 450 °C, the NO conversion rapidly decreased, suggesting an excess production of nitric oxide which could originate from a significant contribution of NH3 oxidation reaction. This agrees with NH3 conversion which remained stable, or it increased constantly above 450 °C. The impact of NH3 oxidation will be studied by us further in this section. The production of N2O was minor, showing only max 20 ppm when sample was tested without water vapor, and 10 ppm when test was performed in hydrothermal conditions.
Figure 4C,D shows the NH3-SCR over Fe-Zr catalyst. The absence of water vapor led to a maximum of 55% of NO conversion at 500 °C. The N2O production was measured at ca. 28 ppm at this temperature. The presence of H2O resulted in a constant increase of NO and NH3 conversions, starting from 300 to 550 °C. At the latter temperature, the NO and NH3 conversions are 35 and 53%, respectively. The decrease of activity, in the presence of H2O, is believed to be mainly due to competing adsorption between water and ammonia on the acid sites [51]. It should be mentioned, additionally, that in the presence of H2O, the Fe-Zr catalyst did not produce N2O over the whole range of studied temperatures.
From Figure 4E, one can note that the support is inactive during NH3-SCR reaction as only conversion of NH3 was observed accompanied by the production of N2O and NO. Negative conversion values were recorded for the latter (not shown in Figure 4E). These observations suggest that selective oxidation of ammonia is a dominant reaction for the support. ZrO2 support tested in the hydrothermal conditions led to the complete inhibition of any significant catalytic reaction below 500 °C. However, some NH3 conversion, not exceeding 10% at 550 °C, occurred above 500 °C.
Furthermore, N2O is the only by-product detected during the NH3-SCR process, which determines selectivity to N2 presented in Figure 5. As shown in Figure 4B,D, the presence of water leads to a decrease in NO conversion but improves, despite this, the removal efficiency of NO by enhancing the selectivity to N2. In the whole SCR process, the N2O concentration detected during the tests in presence of water is very limited for Cu-Zr catalyst and negligible for Fe-Zr catalyst. Therefore, one can conclude that Fe-Zr could be a promising catalyst for NH3-SCR process after its optimization. This higher catalytic performance could be linked with the increase of electron transfer on Fe-Zr catalysts showed by XPS when compared to the Cu-Zr system. In order to confirm these promising results on Fe-Zr catalysts, selective catalytic oxidation of ammonia (NH3-SCO) was performed.
Furthermore, N2O is the only by-product detected during the NH3-SCR reaction process, which determines selectivity to N2 presented in Figure 5. As shown in Figure 4B,D, the presence of water leads to a decrease in NO conversion but improves, despite this, the removal efficiency of NO by enhancing the denitration selectivity to N2. In the whole SCR process, the N2O concentration on the samples in presence of water is very limited for Cu-Zr catalyst and negligible for Fe-Zr catalyst. Therefore, one can conclude that Fe-Zr could be a promising catalyst for NH3-SCR process after its optimization. This higher catalytic performance could be linked with the increase of electron transfer on Fe-Zr catalysts showed by XPS when compared to the Cu-Zr system. In order to confirm these promising results on Fe-Zr catalysts, selective catalytic oxidation of ammonia (NH3-SCO) was performed.

2.2.2. NH3-SCO in the Absence and Presence of Water Vapor

The selective catalytic NH3 oxidation (SCO) ability of a catalyst determines the efficiency of NH3 utilization in the SCR reaction. Figure 5A–F depicts the NH3 oxidation performance of the studied materials in the absence and presence of H2O. Cu-Zr catalyst shows high ammonia oxidation activity starting from 325 °C, reaching constant value of 87% at 450–550 °C (Figure 6A). The oxidation of NH3 led to N2O and NO by-products formation with maximum values of 38 ppm and 250 ppm, respectively. In the hydrothermal conditions, the Cu-Zr catalyst was less active in NH3-SCO, compared to the conditions without water vapor (Figure 6B). NH3 conversion constantly increased over the studied temperatures with a maximum of 68% at 550 °C. Iron promoted ZrO2 was also active in NH3-SCO with 89% of NH3 at 550 °C complemented by the production of N2, N2O, and NO (Supplementary Materials Figure S1; Figure 6C). Ammonia oxidation in the presence of H2O led to the decreased activity with only 28% of NH3 converted (Figure 6D) and low production of side products, i.e., N2O and NO. Figure 5E presents zirconia support which was active in NH3-SCO, resulting mostly in the production of NO (400 ppm) at the highest analyzed temperature. Small amounts of N2O were also observed (10 ppm). The presence of water in ammonia oxidation inhibited reaction, and only 5% of NH3 conversion was observed (Figure 6F). When compared to NH3-SCR results, one can conclude that NH3 oxidation is predominant at high temperature (T > 400 °C) over Cu-Zr and Fe-Zr catalysts. In contrast, during the hydrothermal conditions the adsorbed NH3 is more difficult to be oxidized on the surface of both Cu-Zr and Fe-Zr catalysts. Therefore, the adsorbed NH3 species can effectively react with NO, giving a high NO removal efficiency.

2.2.3. SO2 Activation of Cu-Zr and Fe-Zr Catalysts and their Catalytic Behavior in NH3-SCR of NO in the Absence and Presence of Water Vapor

SO2 Activation of Cu-Zr Catalyst in NH3-SCR of NO in the Absence of Water Vapor

The SO2 activation study in NH3-SCR of NO in the absence of H2O was carried out on Cu-Zr catalyst at 450 °C. Prior to this examination, the reaction of NH3-SCR of NO was performed as a function of temperature, which agrees well with previously obtained results (Figure 4A). Subsequently, the sample was allowed to be stabilized for 60 min before the addition of SO2 for another 60 min, and then after removing the SO2 for next 90 min. When the SO2 was added, a clear increase in both NH3 and NO conversions was observed resulting in ca. 100% (Figure 7). Once the SO2 was removed from the feed, a rapid decrease was registered for both, steadying the values to be initially slightly higher than those registered before SO2 feeding. Over the stabilization in the mixture free of SO2, the conversions gradually increased from 83.7 to 90.5% and 83.9 to 85.7% for NO and NH3 conversions, respectively. The in-situ sulphation promoted the activity of Cu-Zr catalyst in NH3-SCR of NO. Similar observations were made in the studies of Pietrogiacomi et al. [26,27] in which it has been reported that sulphation of Cu-containing ZrO2 catalysts positively affects catalytic performance NH3-SCR of NO due to the enhanced acidic properties of sulphated supports.

SO2 Activation of Fe-Zr in NH3-SCR of NO in the Presence of Water Vapor

Recently, Fan et al. [33] showed that Fe/ZrO2 sulphated catalysts were almost two times more active than non-sulphated Fe/ZrO2 in NH3-SCR of NO. Thus, in order to verify the activation of the catalysts in the presence of SO2, the experiment was performed in hydrothermal conditions over Fe-Zr catalyst and over the support. The results are presented in Figure 8A,B. In the presence of water, an interesting trend was observed for the Fe-Zr catalyst (Figure 8A). During the first hour of stabilization, the conversions of NO and NH3 were 29% and 30%, respectively. After SO2 addition, a slight decrease of NO and NH3 was observed, probably due to the sulphation of the Fe-Zr and inhibition of the active sites. However, after the first minutes in the presence of SO2, both conversions of NO and NH3 increased. It is worth to note that the consumption of NH3 reached 47%, whereas only 30% of NO was converted. This latter result could not be linked with any NH3 oxidation activity, despite the high temperature of 450 °C. No side products were recorded by MS that could suggest NH3-SCO occurrence. Moreover, on the ZrO2 support a similar NH3 consumption was registered (Figure 8B). One can assume that ammonia consumption is mainly due to its adsorption enhanced by a formation of new acidic sites in the presence of SO2 which can act as a reservoir [33]. Similar observations were made on other type of catalysts such as V2O5-WO3/TiO2 [52,53,54].

3. Materials and Methods

3.1. Catalysts Synthesis

Pluronic® P123 amphiphilic block copolymer (Aldrich, Saint-Quentin Fallavier, France), urea (Sigma-Aldrich, Saint-Quentin Fallavier, France), zirconium (IV) oxynitrate hydrate (Aldrich, Saint-Quentin Fallavier, France) and copper (II) nitrate hemi(pentahydrate) (Alfa-Aesar Thermo Fisher Lancashire, UK) were dissolved in 375 mL of distilled water. The suspension was heated from room temperature to 95 °C within 30 min under vigorous stirring. After stirring at 95 °C for 48 h, the obtained colloidal solution was aged at 100 °C for 24 h. Then, the material was filtrated, washed with deionized water, and dried at room temperature. Finally, the solid material was calcined at 600 °C for 5 h with a heating rate of 1 °C/min. The obtained material was denoted as Cu-Zr. The iron-containing catalyst was prepared using the same method with the iron nitrate nonahydrate. The dosage of different chemical reagents for synthesis of each catalyst is listed in Table 3 and corresponds to 3 wt% loading of Fe or Cu.

3.2. Characterization Techniques

The structural properties of samples were obtained using the X-ray diffraction (XRD) method on a DX-1000 CSC diffractometer (Malvern PANalytical, Shanghai, China), equipped with the Cu Kα radiation at 40 kV and 25 mA. The data was recorded in the range 5° < 2θ < 90° with 0.3 s/step scan speed and 0.03° step size.
Textural properties of the samples were determined by N2 physisorption at −196 °C using a Micromeritics (Aachen, Germany) ASAP 2020 instrument. The samples were previously treated in vacuum for 2 h at 200 °C. The data on the specific surface area, mesoporous pore volume and average pore diameter were calculated by the equations of Brunauer−Emmett−Teller (BET), Barrett−Joyner−Halenda (BJH) desorption average pore width (4V/A), and desorption of volume of pores Barrett−Joyner−Halenda (BJH), respectively.
The acidity of samples was examined by NH3-TPD using an AUTOCHEM 2910 (Micromeritics, Aachen, Germany). The solid was pre-treated at 550 °C (ramp 10 °C/min) during 2 h, under air flow (30 mL/min). Then, it was exposed to 5 vol% NH3 in He (30 mL/min) for 30 min, and subsequently with He (30 mL/min) for 30 min to remove the physiosorbed ammonia. Finally, the NH3 desorption was performed in helium flow (30 mL/min) from 100 to 550 °C (the heating rate was 5 °C/min).
The elemental analysis of sample surface was investigated by X-ray photoelectron spectroscopy (XPS) on a KRATOS spectrometer with an AXIS Ultra DLD (Manchester, UK). All the data were calibrated using the C 1s peak at 284.6 eV, as described elsewhere [43].

3.3. Catalytic Tests

The selective catalytic reduction of NO with NH3 (NH3-SCR) was studied in a U-shape glass reactor operating at atmospheric pressure. Prior to the catalytic tests, a catalyst (75 mg) was activated in situ at 550 °C for 30 min in a flow of O2/He and then cooled to 180 °C. The following compositions of the gas mixture for NH3-SCR of NO: [NO] = 1000 ppm, [NH3] = 1000 ppm, [H2O] = 3.5 vol%, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min. The tolerance of SO2 was examined at 450 °C with [SO2] = 100 ppm. The weight hourly space velocity (WHSV) was about 80,000 mL/g⋅h. The SCR was carried out on programmed temperature from 180 to 550 °C with the heating rate 5 °C/min. The reactants and products were analyzed by a quadruple mass spectrometer (Pfeiffer Omnistar, Saclay, France) equipped with Channeltron and Faraday detectors recording the following masses: NH3 (m/z = 15, 17, 18), NO (m/z = 30), O2 (m/z= 16, 32), H2O (m/z = 17, 18), N2 (m/z = 14, 28), N2O (m/z = 28, 30, 44), and He (m/z = 4).
The selective catalytic oxidation of NH3 (NH3-SCO) was studied in the U-shape glass reactor operating in similar conditions as described above, using the following gas mixture for NH3-SCO: [NH3] = 1000 ppm, [H2O] = 3.5 vol%, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min. Similarly, the reactants and products were analyzed by a quadruple mass spectrometer (Pfeiffer Omnistar, Saclay, France) equipped with Channeltron and Faraday detectors recording the following masses: NH3 (m/z = 15, 17, 18), NO (m/z = 30), O2 (m/z= 16, 32), H2O (m/z = 17, 18), N2 (m/z = 14, 28), N2O (m/z = 28, 30, 44), and He (m/z = 4).

4. Conclusions

A novel synthesis was proposed for the preparation of zirconia-supported Cu and Fe catalysts. The synthesized catalysts showed promising results in NH3-SCR of NO in both the presence and absence of water vapor. The studied materials presented NO reduction with NH3 which mainly led to N2 but side reactions resulting in N2O and NO2 formation were also present. Under hydrothermal conditions NO conversion was lower (<50%) and inferior N2O production (ca. 10 ppm) was measured for Cu-Zr and Fe-Zr catalysts, compared to the dry reaction. Furthermore, the Fe-Zr catalyst was highly inactive in NH3 oxidation during NH3-SCR of NO. Regardless of the presence or absence of H2O, the Cu and Fe promoted catalysts showed the enhanced resistance in the presence of SO2. Feeding SO2 resulted in an enhanced catalytic performance, suggesting that sulphur dioxide may positively affect the acidity of the ZrO2-supported samples. A thorough study is underway to optimize the sulphation of Cu-Zr and Fe-Zr catalysts, coupling FTIR-in situ studies in the presence and absence of SO2, for a better understanding of surface, acid-base properties and catalytic behavior.

Supplementary Materials

The following are available online at https://0-www-mdpi-com.brum.beds.ac.uk/2073-4344/11/1/55/s1, Figure S1: N2 selectivity as a function of temperature measured during NH3-SCO over Cu-Zr catalyst (A) in absence of water, (B) in presence of water, Fe-Zr catalyst (C) in absence of water, (D) in presence of water, and ZrO2 support (E) in absence of water, (F) in presence of water. The experimental conditions: [NH3] = 1000 ppm, [H2O] = 3.5 vol% when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 ml/min.

Author Contributions

Conceptualization, K.Ś., P.D.C., and G.D.; methodology, K.Ś., Y.W., C.H., L.L., P.D.C., G.D.; validation, K.Ś., and G.D.; formal analysis, K.Ś., Y.W., C.H., L.L., P.D.C., G.D.; investigation, K.Ś., Y.W., L.L., G.D.; resources, C.H., P.D.C., G.D.; writing—original draft preparation, K.Ś., Y.W., C.H., P.D.C., G.D.; writing—review and editing, K.Ś., Y.W., C.H., L.L., P.D.C., G.D.; supervision, K.Ś., C.H., P.D.C., G.D.; project administration, C.H., P.D.C., G.D.; funding acquisition, C.H., G.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Acknowledgments

We would like to thank Sichuan University and Institut Charles Gerhardt Montpellier, Université de Montpellier, for experimental and characterization facilities.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Vascellari, M. NOx Emission and Mitigation Technologies. In Handbook of Clean Energy Systems; John Wiley & Sons: Hoboken, NJ, USA, 2015; pp. 1–23. ISBN 9781118991978. [Google Scholar]
  2. Iwamoto, M.; Furukawa, H.; Mine, Y.; Uemura, F.; Mikuriya, S.I.; Kagawa, S. Copper(II) Ion-exchanged ZSM-5 zeolites as highly active catalysts for direct and continuous decomposition of nitrogen monoxide. J. Chem. Soc. Ser. Chem. Commun. 1986, 1272–1273. [Google Scholar] [CrossRef]
  3. Ishihara, T.; Ando, M.; Sada, K.; Takiishi, K.; Yamada, K.; Nishiguchi, H.; Takita, Y. Direct decomposition of NO into N2 and O2 over La(Ba)Mn(In)O3 perovskite oxide. J. Catal. 2003, 220, 104–114. [Google Scholar] [CrossRef]
  4. Liu, G.; Gao, P.X. A review of NOx storage/reduction catalysts: Mechanism, materials and degradation studies. Catal. Sci. Technol. 2011, 1, 552–568. [Google Scholar] [CrossRef]
  5. Seo, C.K.; Kim, H.; Choi, B.; Lim, M.T. The optimal volume of a combined system of LNT and SCR catalysts. J. Ind. Eng. Chem. 2011, 17, 382–385. [Google Scholar] [CrossRef]
  6. Mrad, R.; Aissat, A.; Cousin, R.; Courcot, D.; Siffert, S. Catalysts for NOx selective catalytic reduction by hydrocarbons (HC-SCR). Appl. Catal. A Gen. 2015, 504, 542–548. [Google Scholar] [CrossRef]
  7. Breen, J.P.; Burch, R. A review of the effect of the addition of hydrogen in the selective catalytic reduction of NOx with hydrocarbons on silver catalysts. Top. Catal. 2006, 39, 53–58. [Google Scholar] [CrossRef]
  8. Chen, G.; Xu, J.; Yu, H.; Guo, F.; Xie, J.; Wang, Y. Effect of the non-thermal plasma treatment on the structure and SCR activity of vanadium-based catalysts. Chem. Eng. J. 2020, 380, 122286. [Google Scholar] [CrossRef]
  9. Kowalczyk, A.; Święs, A.; Gil, B.; Rutkowska, M.; Piwowarska, Z.; Borcuch, A.; Michalik, M.; Chmielarz, L. Effective catalysts for the low-temperature NH3-SCR process based on MCM-41 modified with copper by template ion-exchange (TIE) method. Appl. Catal. B Environ. 2018, 237, 927–937. [Google Scholar] [CrossRef]
  10. Abid, R.; Delahay, G.; Tounsi, H. Selective catalytic reduction of NO by NH3 on cerium modified faujasite zeolite prepared from aluminum scraps and industrial metasilicate. J. Rare Earths 2020, 38, 250–256. [Google Scholar] [CrossRef]
  11. Kieffer, C.; Lavy, J.; Jeudy, E.; Bats, N.; Delahay, G. Characterisation of a commercial automotive NH3-SCR copper-zeolite catalyst. Top. Catal. 2013, 56, 40–44. [Google Scholar] [CrossRef]
  12. Arfaoui, J.; Ghorbel, A.; Petitto, C.; Delahay, G. A new V2O5-MoO3-TiO2-SO42− nanostructured aerogel catalyst for diesel DeNOx technology. New J. Chem. 2020, 44, 16119–16134. [Google Scholar] [CrossRef]
  13. Leistner, K.; Mihai, O.; Wijayanti, K.; Kumar, A.; Kamasamudram, K.; Currier, N.W.; Yezerets, A.; Olsson, L. Comparison of Cu/BEA, Cu/SSZ-13 and Cu/SAPO-34 for ammonia-SCR reactions. Catal. Today 2015, 258, 49–55. [Google Scholar] [CrossRef]
  14. Jabłońska, M.; Delahay, G.; Kruczała, K.; Błachowski, A.; Tarach, K.A.; Brylewska, K.; Petitto, C.; Góra-Marek, K. Standard and fast selective catalytic reduction of NO with NH3 on zeolites Fe-BEA. J. Phys. Chem. C 2016, 120, 16831–16842. [Google Scholar] [CrossRef]
  15. Zhang, L.; Wang, D.; Liu, Y.; Kamasamudram, K.; Li, J.; Epling, W. SO2 poisoning impact on the NH3-SCR reaction over a commercial Cu-SAPO-34 SCR catalyst. Appl. Catal. B Environ. 2014, 156–157, 371–377. [Google Scholar] [CrossRef]
  16. Li, Y.; Cheng, H.; Li, D.; Qin, Y.; Xie, Y.; Wang, S. WO3/CeO2-ZrO2 a promising catalyst for selective catalytic reduction (SCR) of NOx with NH3 in diesel exhaust. Chem. Commun. 2008, 1470–1472. [Google Scholar] [CrossRef]
  17. Djerad, S.; Geiger, B.; Schott, F.J.P.; Kureti, S. Synthesis of nano-sized ZrO2 and its use as catalyst support in SCR. Catal. Commun. 2009, 10, 1103–1106. [Google Scholar] [CrossRef]
  18. Apostolescu, N.; Geiger, B.; Hizbullah, K.; Jan, M.T.; Kureti, S.; Reichert, D.; Schott, F.; Weisweiler, W. Selective catalytic reduction of nitrogen oxides by ammonia on iron oxide catalysts. Appl. Catal. B Environ. 2006, 62, 104–114. [Google Scholar] [CrossRef]
  19. Shen, B.; Zhang, X.; Ma, H.; Yao, Y.; Liu, T. A comparative study of Mn/CeO2, Mn/ZrO2 and Mn/Ce-ZrO2 for low temperature selective catalytic reduction of NO with NH3 in the presence of SO2 and H2O. J. Environ. Sci. 2013, 25, 791–800. [Google Scholar] [CrossRef]
  20. Peng, B.; Rappé, K.G.; Cui, Y.; Gao, F.; Szanyi, J.; Olszta, M.J.; Walter, E.D.; Wang, Y.; Holladay, J.D.; Goffe, R.A. Enhancement of high-temperature selectivity on Cu-SSZ-13 towards NH3-SCR reaction from highly dispersed ZrO2. Appl. Catal. B Environ. 2020, 263. [Google Scholar] [CrossRef]
  21. Verdier, S.; Rohart, E.; Bradshaw, H.; Harris, D.; Bichon, P.; Delahay, G. Acidic zirconia materials for durable NH3-SCR deNOx catalysts. SAE Tech. Pap. 2008, 1, 1022. [Google Scholar]
  22. Delahay, G.; Ensuque, E.; Coq, B.; Figuéras, F. Selective catalytic reduction of nitric oxide by n-decane on Cu/sulfated-zirconia catalysts in oxygen rich atmosphere: Effect of sulfur and copper contents. J. Catal. 1998, 175, 7–15. [Google Scholar] [CrossRef]
  23. Delahay, G.; Coq, B.; Ensuque, E.; Figuéras, F. Catalytic behaviour of Cu/ZrO2 and Cu/ZrO2(SO42−) in the reduction of nitric oxide by decane in oxygen-rich atmosphere. Catal. Lett. 1996, 39, 105–109. [Google Scholar] [CrossRef]
  24. Figueras, F.; Coq, B.; Ensuque, E.; Tachon, D.; Delahay, G. Catalytic properties of Cu on sulphated zirconias for DeNOx in excess of oxygen using n-decane as reductant. Catal. Today 1998, 42, 117–125. [Google Scholar] [CrossRef]
  25. Pasel, J.; Speer, V.; Albrecht, C.; Richter, F.; Papp, H. Metal doped sulfated ZrO2 as catalyst for the selective catalytic reduction (SCR) of NO with propane. Appl. Catal. B Environ. 2000, 25, 105–113. [Google Scholar] [CrossRef]
  26. Pietrogiacomi, D.; Sannino, D.; Magliano, A.; Ciambelli, P.; Tuti, S.; Indovina, V. The catalytic activity of CuSO4/ZrO2 for the selective catalytic reduction of NOx with NH3 in the presence of excess O2. Appl. Catal. B Environ. 2002, 36, 217–230. [Google Scholar] [CrossRef]
  27. Pietrogiacomi, D.; Magliano, A.; Sannino, D.; Campa, M.C.; Ciambelli, P.; Indovina, V. In situ sulphated CuOx/ZrO2 and CuOx/sulphated-ZrO2 as catalysts for the reduction of NOx with NH3 in the presence of excess O2. Appl. Catal. B Environ. 2005, 60, 83–92. [Google Scholar] [CrossRef]
  28. Ismail, R.; Arfaoui, J.; Ksibi, Z.; Ghorbel, A.; Delahay, G. Effect of the iron amount on the physicochemical properties of Fe–ZrO2 aerogel catalysts for the total oxidation of toluene in the presence of water vapor. J. Porous Mater. 2020, 27, 1847–1852. [Google Scholar] [CrossRef]
  29. Navío, J.A.; Hidalgo, M.C.; Colón, G.; Botta, S.G.; Litter, M.I. Preparation and physicochemical properties of ZrO2 and Fe/ZrO2 prepared by a sol-gel technique. Langmuir 2001, 17, 202–210. [Google Scholar] [CrossRef]
  30. López-Hernández, I.; Mengual, J.; Palomares, A.E. The influence of the support on the activity of Mn–Fe catalysts used for the selective catalytic reduction of NOx with ammonia. Catalysts 2020, 10, 63. [Google Scholar] [CrossRef] [Green Version]
  31. Kustov, A.L.; Rasmussen, S.B.; Fehrmann, R.; Simonsen, P. Activity and deactivation of sulphated TiO2- and ZrO2-based V, Cu, and Fe oxide catalysts for NO abatement in alkali containing flue gases. Appl. Catal. B Environ. 2007, 76, 9–14. [Google Scholar] [CrossRef]
  32. Indovina, V.; Campa, M.C.; Pepe, F.; Pietrogiacomi, D.; Tuti, S. Iron species in FeOx/ZrO2 and FeOx/sulphated-ZrO2 catalysts. Stud. Surf. Sci. Catal. 2005, 155, 329–337. [Google Scholar] [CrossRef]
  33. Fan, B.; Zhang, Z.; Liu, C.; Liu, Q. Investigation of sulfated iron-based catalysts with different sulfate position for selective catalytic reduction of NOx with NH3. Catalysts 2020, 10, 1035. [Google Scholar] [CrossRef]
  34. Liu, C.; Wang, H.; Bi, Y.; Zhang, Z. A study on the selective catalytic reduction of NOx: by ammonia on sulphated iron-based catalysts. RSC Adv. 2020, 10, 40948–40959. [Google Scholar] [CrossRef]
  35. Yu, Z.; Liu, B.; Zhou, H.; Feng, C.; Wang, X.; Yuan, K.; Gan, X.; Zhu, L.; Zhang, G.; Xu, D. Mesoporous ZrO2 fibers with enhanced surface area and the application as recyclable absorbent. Appl. Surf. Sci. 2017, 399, 288–297. [Google Scholar] [CrossRef]
  36. Gao, S.; Chen, X.; Wang, H.; Mo, J.; Wu, Z.; Liu, Y.; Weng, X. Ceria supported on sulfated zirconia as a superacid catalyst for selective catalytic reduction of NO with NH3. J. Colloid Interface Sci. 2013, 394, 515–521. [Google Scholar] [CrossRef] [PubMed]
  37. Kogler, M.; Köck, E.M.; Vanicek, S.; Schmidmair, D.; Götsch, T.; Stöger-Pollach, M.; Hejny, C.; Klötzer, B.; Penner, S. Enhanced kinetic stability of pure and Y-doped tetragonal ZrO2. Inorg. Chem. 2014, 53, 13247–13257. [Google Scholar] [CrossRef]
  38. Tan, D.; Lin, G.; Liu, Y.; Teng, Y.; Zhuang, Y.; Zhu, B.; Zhao, Q.; Qiu, J. Synthesis of nanocrystalline cubic zirconia using femtosecond laser ablation. J. Nanoparticle Res. 2011, 13, 1183–1190. [Google Scholar] [CrossRef]
  39. Boroń, P.; Chmielarz, L.; Dzwigaj, S. Influence of Cu on the catalytic activity of FeBEA zeolites in SCR of NO with NH3. Appl. Catal. B Environ. 2015, 168–169, 377–384. [Google Scholar] [CrossRef]
  40. Du, L.; Wang, W.; Yan, H.; Wang, X.; Jin, Z.; Song, Q.; Si, R.; Jia, C. Copper-ceria sheets catalysts: Effect of copper species on catalytic activity in CO oxidation reaction. J. Rare Earths 2017, 35, 1186–1196. [Google Scholar] [CrossRef]
  41. Shannon, R.D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr. Sect. A Cryst. Phys. Diffr. Theor. Gen. Crystallogr. 1976, 32, 751–767. [Google Scholar] [CrossRef]
  42. Breviglieri, S.T.; Cavalheiro, É.T.G.; Chierice, G.O. Correlation between ionic radius and thermal decomposition of Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) diethanoldithiocarbamates. Thermochim. Acta 2000, 356, 79–84. [Google Scholar] [CrossRef]
  43. Wang, Y.; Zhao, Q.; Wang, Y.; Hu, C.; Da Costa, P. One-Step synthesis of highly active and stable Ni-ZrOx for dry reforming of methane. Ind. Eng. Chem. Res. 2020, 59, 11441–11452. [Google Scholar] [CrossRef]
  44. Khorsand Zak, A.; Abd Majid, W.H.; Abrishami, M.E.; Yousefi, R. X-ray analysis of ZnO nanoparticles by Williamson-Hall and size-strain plot methods. Solid State Sci. 2011, 13, 251–256. [Google Scholar] [CrossRef]
  45. Williamson, G.K.; Hall, W.H. X-ray line broadening from filed aluminium and wolfram. Acta Metall. 1953, 1, 22–31. [Google Scholar] [CrossRef]
  46. Ismail, R.; Arfaoui, J.; Ksibi, Z.; Ghorbel, A.; Delahay, G. Ag/ZrO2 and Ag/Fe–ZrO2 catalysts for the low temperature total oxidation of toluene in the presence of water vapor. Transit. Met. Chem. 2020, 45, 501–509. [Google Scholar] [CrossRef]
  47. Lee, S.M.; Park, K.H.; Hong, S.C. MnOx/CeO2-TiO2 mixed oxide catalysts for the selective catalytic reduction of NO with NH3 at low temperature. Chem. Eng. J. 2012, 195–196, 323–331. [Google Scholar] [CrossRef]
  48. Zhao, H.; Wang, Y.; Wang, Y.; Cao, T.; Zhao, G. Electro-Fenton oxidation of pesticides with a novel Fe3O4@Fe2O3/activated carbon aerogel cathode: High activity, wide pH range and catalytic mechanism. Appl. Catal. B Environ. 2012, 125, 120–127. [Google Scholar] [CrossRef]
  49. Wang, Y.; Li, L.; Wang, Y.; Da Costa, P.; Hu, C. Highly carbon-resistant Y doped NiO–ZrOm catalysts for dry reforming of methane. Catalysts 2019, 9, 1055. [Google Scholar] [CrossRef] [Green Version]
  50. Sutthiumporn, K.; Maneerung, T.; Kathiraser, Y.; Kawi, S. CO2 dry-reforming of methane over La0.8Sr0.2Ni0.8M0.2O3 perovskite (M = Bi, Co, Cr, Cu, Fe): Roles of lattice oxygen on C-H activation and carbon suppression. Int. J. Hydrogen Energy 2012, 37, 11195–11207. [Google Scholar] [CrossRef]
  51. Jiang, H.; Zhou, J.; Wang, C.; Li, Y.; Chen, Y.; Zhang, M. Effect of cosolvent and temperature on the structures and properties of Cu-MOF-74 in low-temperature NH3-SCR. Ind. Eng. Chem. Res. 2017, 56, 3542–3550. [Google Scholar] [CrossRef]
  52. Khodayari, R.; Odenbrand, C.U.I. Regeneration of commercial SCR catalysts by washing and sulphation: Effect of sulphate groups on the activity. Appl. Catal. B Environ. 2001, 33, 277–291. [Google Scholar] [CrossRef]
  53. Miao, J.; Li, H.; Su, Q.; Yu, Y.; Chen, Y.; Chen, J.; Wang, J. The combined promotive effect of SO2 and HCl on Pb-poisoned commercial NH3-SCR V2O5-WO3/TiO2 catalysts. Catal. Commun. 2019, 125, 118–122. [Google Scholar] [CrossRef]
  54. Yu, Y.; Wang, J.; Chen, J.; Meng, X.; Chen, Y.; He, C. Promotive effect of SO2 on the activity of a deactivated commercial selective catalytic reduction ratalyst: An in situ DRIFT study. Ind. Eng. Chem. Res. 2014, 53, 16229–16234. [Google Scholar] [CrossRef]
Catalysts 11 00055 g001 550
Figure 1. X-ray diffraction (XRD) diffractograms of ZrO2 support, Cu-Zr and Fe-Zr calcined catalysts.
Figure 1. X-ray diffraction (XRD) diffractograms of ZrO2 support, Cu-Zr and Fe-Zr calcined catalysts.
Catalysts 11 00055 g001
Catalysts 11 00055 g002 550
Figure 2. Temperature-programmed desorption of NH3 (NH3-TPD) profiles of ZrO2 support, Cu-Zr and Fe-Zr calcined catalysts.
Figure 2. Temperature-programmed desorption of NH3 (NH3-TPD) profiles of ZrO2 support, Cu-Zr and Fe-Zr calcined catalysts.
Catalysts 11 00055 g002
Catalysts 11 00055 g003 550
Figure 3. X-ray photoelectron spectroscopy (XPS) profiles of ZrO2 support, Cu-Zr and Fe-Zr calcined catalysts. (A) The O 1s, (B) Zr 3d, (C) Fe 2p, and (D) Cu 2p. All the data are referenced using the C 1s peak at 284.6 eV.
Figure 3. X-ray photoelectron spectroscopy (XPS) profiles of ZrO2 support, Cu-Zr and Fe-Zr calcined catalysts. (A) The O 1s, (B) Zr 3d, (C) Fe 2p, and (D) Cu 2p. All the data are referenced using the C 1s peak at 284.6 eV.
Catalysts 11 00055 g003
Catalysts 11 00055 g004 550
Figure 4. NO and NH3 conversion profiles and N2O production as a function of temperature in NH3-SCR over Cu-Zr catalyst (A) in absence of water, (B) in presence of water, Fe-Zr catalyst (C) in absence of water, (D) in presence of water, and ZrO2 support (E) in absence of water, (F) in presence of water. The experimental conditions: [NO] = 1000 ppm, [NH3] = 1000 ppm, [H2O] = 3.5 vol% when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Figure 4. NO and NH3 conversion profiles and N2O production as a function of temperature in NH3-SCR over Cu-Zr catalyst (A) in absence of water, (B) in presence of water, Fe-Zr catalyst (C) in absence of water, (D) in presence of water, and ZrO2 support (E) in absence of water, (F) in presence of water. The experimental conditions: [NO] = 1000 ppm, [NH3] = 1000 ppm, [H2O] = 3.5 vol% when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Catalysts 11 00055 g004
Catalysts 11 00055 g005 550
Figure 5. N2 selectivity as a function of temperature measured during NH3-SCR over Cu-Zr catalyst (A) in absence of water, (B) in presence of water, Fe-Zr catalyst (C) in absence of water, (D) in presence of water, and ZrO2 support (E) in absence of water. The experimental conditions: [NO] = 1000 ppm, [NH3] = 1000 ppm, [H2O] = 3.5 vol% when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Figure 5. N2 selectivity as a function of temperature measured during NH3-SCR over Cu-Zr catalyst (A) in absence of water, (B) in presence of water, Fe-Zr catalyst (C) in absence of water, (D) in presence of water, and ZrO2 support (E) in absence of water. The experimental conditions: [NO] = 1000 ppm, [NH3] = 1000 ppm, [H2O] = 3.5 vol% when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Catalysts 11 00055 g005
Catalysts 11 00055 g006 550
Figure 6. NH3 conversion profile and N2O and NO production profiles as a function of temperature in NH3-SCO over Cu-Zr catalyst (A) in absence of water, (B) in presence of water; Fe-Zr catalyst (C) in absence of water, (D) in presence of water; and ZrO2 support (E) in absence of water, (F) in presence of water. The experimental conditions: [NH3] = 1000 ppm, [H2O] = 3.5 vol% when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Figure 6. NH3 conversion profile and N2O and NO production profiles as a function of temperature in NH3-SCO over Cu-Zr catalyst (A) in absence of water, (B) in presence of water; Fe-Zr catalyst (C) in absence of water, (D) in presence of water; and ZrO2 support (E) in absence of water, (F) in presence of water. The experimental conditions: [NH3] = 1000 ppm, [H2O] = 3.5 vol% when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Catalysts 11 00055 g006
Catalysts 11 00055 g007 550
Figure 7. Effect of SO2 addition during NH3-SCR over Cu-Zr catalyst in the absence of water. The experimental conditions: [NO] = [NH3] = 1000 ppm, [SO2] = 100 ppm when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Figure 7. Effect of SO2 addition during NH3-SCR over Cu-Zr catalyst in the absence of water. The experimental conditions: [NO] = [NH3] = 1000 ppm, [SO2] = 100 ppm when used, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Catalysts 11 00055 g007
Catalysts 11 00055 g008 550
Figure 8. Effect of SO2 addition during NH3-SCR over Fe-Zr and ZrO2 catalysts in the hydrothermal conditions. (A) Fe-Zr catalyst, (B) ZrO2 support. The experimental conditions: [NO] = [NH3] = 1000 ppm, [SO2] = 100 ppm when used, [H2O] = 3.5 vol%, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Figure 8. Effect of SO2 addition during NH3-SCR over Fe-Zr and ZrO2 catalysts in the hydrothermal conditions. (A) Fe-Zr catalyst, (B) ZrO2 support. The experimental conditions: [NO] = [NH3] = 1000 ppm, [SO2] = 100 ppm when used, [H2O] = 3.5 vol%, [O2] = 2.5 vol% diluted in helium; total flowrate of 100 mL/min.
Catalysts 11 00055 g008
Table
Table 1. Structural and textural properties of ZrO2, Cu-Zr and Fe-Zr calcined catalyst.
Table 1. Structural and textural properties of ZrO2, Cu-Zr and Fe-Zr calcined catalyst.
SampleBragg Angles/°d-Spacing/ÅCrystallite Size of ZrO2/nm *Specific Surface Area/m2/gVolume of Mesopores/cm3/gAverage Pore Size/nm
ZrO230.1922.957613.7810.12 5.0
Cu-Zr30.3762.940211.31280.06 3.3
Fe-Zr30.3492.94278.81390.09 3.5
* calculated by the Williamson and Hall method.
Table
Table 2. Elemental composition of ZrO2, Cu-Zr calcined catalyst and Fe-Zr calcined catalyst from XPS analysis.
Table 2. Elemental composition of ZrO2, Cu-Zr calcined catalyst and Fe-Zr calcined catalyst from XPS analysis.
SampleZr
(wt%)		O
(wt%)		Cu
(wt%)		Fe
(wt%)		O Species (%)Zr Species (%)
O2−CO32−OH−Zr3+Zr4+
ZrO266.833.2--70.618.111.337.562.5
Cu-Zr66.631.22.2-64.924.710.442.857.2
Fe-Zr64.432.4-3.275.819.94.395.34.7
Table
Table 3. The chemical dosage used during for the synthesis of Cu-Zr and Fe-Zr catalysts.
Table 3. The chemical dosage used during for the synthesis of Cu-Zr and Fe-Zr catalysts.
SampleP123/gUrea/gZrO(NO)3·2H2O/gCu(NO)2·2.5H2O/gFe(NO)3·9H2O/g
Cu-Zr7.847.505.030.14-
Fe-Zr7.847.505.03-0.24
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Świrk, K.; Wang, Y.; Hu, C.; Li, L.; Da Costa, P.; Delahay, G. Novel Preparation of Cu and Fe Zirconia Supported Catalysts for Selective Catalytic Reduction of NO with NH3. Catalysts 2021, 11, 55. https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010055

AMA Style

Świrk K, Wang Y, Hu C, Li L, Da Costa P, Delahay G. Novel Preparation of Cu and Fe Zirconia Supported Catalysts for Selective Catalytic Reduction of NO with NH3. Catalysts. 2021; 11(1):55. https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010055

Chicago/Turabian Style

Świrk, Katarzyna, Ye Wang, Changwei Hu, Li Li, Patrick Da Costa, and Gérard Delahay. 2021. "Novel Preparation of Cu and Fe Zirconia Supported Catalysts for Selective Catalytic Reduction of NO with NH3" Catalysts 11, no. 1: 55. https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010055

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop