Spectroscopic studies of MFI and USY zeolite layers over stainless steel 316L wire gauze meshes

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

Contents lists available at ScienceDirect

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa

Spectroscopic studies of MFI and USY zeolite layers over stainless steel 316L wire gauze meshes Ł. Kuterasiński a,⁎, P. Bodzioch b, K. Dymek b, R.J. Jędrzejczyk c, D.K. Chlebda d, J. Łojewska d, M. Sitarz e, G. Kurowski b, P. Jeleń e, P.J. Jodłowski b,⁎ a

Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Kraków, Poland Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska 24, 30-155 Kraków, Poland Małopolska Centre of Biotechnology, Jagiellonian University, ul. Gronostajowa 7A, 30-387 Kraków, Poland d Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland e Faculty of Materials Science and Ceramics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland b c

a r t i c l e

i n f o

Article history: Received 11 November 2019 Received in revised form 9 January 2020 Accepted 9 January 2020 Available online 10 January 2020 Keywords: In situ hydrothermal synthesis Structured catalysts Zeolite Spectroscopic characterisation SCR deNOx

a b s t r a c t The objective of our study was to develop and optimize the in situ synthesis of zeolitic thin coatings with USY (ultrastabilised form of faujasite) and MFI (Model Five) type structure on metallic structured catalysts supports using the hydrothermal method. Thus, obtained zeolitic materials were studied in terms of their prospective activity in selective catalytic reduction of nitrogen oxides (SCR of NOx) with ammonia. Optimization of the preparation method consisted of several steps including: the pretreatment of steel carrier to obtain an adhesive surface, hydrothermal synthesis of zeolites at different conditions and adjustment of the zeolite structure type (MFI vs. USY). As a result, uniform zeolitic layers were deposited on steel supports. Prepared structured supports were ion-exchanged with copper or cobalt precursors to obtain active catalysts and then characterised by various physicochemical methods with a particular reference to the in situ Fourier-Transform Infrared Spectroscopy (FTIR), Ultraviolet–Visible Diffusion Reflectance Spectroscopy (DRS-UV/VIS) and Raman spectroscopy. For CuUSY sample, slightly better catalytic properties are related to higher copper content. In the case of Cosamples, worse catalytic properties in comparison with Cu counterparts might imply from higher concentration of Brønsted acid sites, lower cobalt loading (thus concentration of Lewis acid sites) and the presence of cobalt cation significantly in oxide form (evidenced by Raman, DRS-UV/VIS spectroscopy and by in situ FT-IR sorption studies). © 2020 Elsevier B.V. All rights reserved.

1. Introduction Zeolites (molecular sieves) are crystallographically defined microporous solids commercially available in white powder form that could be used as catalysts precursors. The structure (framework) of zeolites consists of tetrahedral units in which small Al or Si cations (collectively denoted T-sites) are located at their centers and oxygen atoms at their corners. The most popular method of zeolites preparation is hydrothermal synthesis. High temperature and autogenous pressure of water vapor present in the starting gel of Al and Si oxides or hydroxides allow for the formation and growth of the product crystals [1,2].

⁎ Corresponding authors. E-mail addresses: [email protected] (Ł Kuterasiński), [email protected] (P.J. Jodłowski).

https://doi.org/10.1016/j.saa.2020.118060 1386-1425/© 2020 Elsevier B.V. All rights reserved.

The application of zeolites as catalysts in powder form is associated with some difficulties related to the mass and heat transport, and among them especially overheating of catalysts, flow resistance and connected with it high pressure drop inside the reactor. A remedy for this seems a structured catalysts and especially ceramic monoliths that has already found a widespread application in many areas of chemical industry. Another type of structured carriers studied by us are steel carriers in form of short channel structures of different shapes [3–5]. Recently, foam like carriers have also been intensely studied and shown to be even better than monoliths and short channeled structures regarding mass transport and flow resistance properties [3–5]. In brief, the indubitable advantages of the structured carries mentioned above are high surface area, enhanced heat and mass transport properties which result in elimination of hot-spots and better overall reactor performance. The deposition of a uniform zeolite layer over metallic support is influenced not only by the parameters of zeolite gels and deposition conditions, but also by the shape and type of the material of the structured

2

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

support. Due to the large number of possible shapes of structured supports (monoliths, short channel structures, gauzes, membranes, foams) and different material types including ceramics, metals or polymers, the literature provides information on specific preparation condition [6–19]. In our paper we investigate the in situ synthesis of USY and MFI zeolite layers on short channel structured stainless steel support using the in situ hydrothermal method. The novelty of our work is a comprehensive optimization of such parameters as the presence/absence of steel carrier pretreatment, the application of static or dynamic conditions during in situ hydrothermal synthesis of zeolites and the influence of zeolite structure type on deposited coating loadings. For the sake of the methods comparison and optimization of the preparation conditions thus obtained Cu and Co exchanged samples were characterised by various physicochemical techniques and tested in SCR of NOx with ammonia. 2. Experimental 2.1. Sample preparation 2.1.1. Steel carrier pretreatment Stainless steel 316L wire gauze meshes (ANN-FILTER Poland, 66.5% Fe, 17.5% Cr, 11.5% Ni, 2.5% Mo, 2% Mn and traces of C, Si, P, S and N) were used as a support for the zeolites coatings. The wire gauze parameters were: Dh = 1.5 × 10−3 m, wire diameter 0.5 × 10−3 m. Prior to the coating deposition, the metallic wire gauzes were cut into 10.0 cm2 pieces. To determine the influence of the support pretreatment on the coating quality three different procedures were used:,: i) the first part constituted unmodified steel support, ii) the second part of steel carrier was treated with a 25% aqueous hydrochloric solution (20 min, room temperature), iii) the last group of stainlesssteel sample was cleaned by boiling toluene for 2 h, followed by the treatment in hydrochloric acid aqueous solution (conditions as above mentioned). Improving the bonding of zeolite with the support and thus the coating stability or increasing the loading on the support might be some reasons for the pretreatment of the supports. 2.1.2. In situ hydrothermal synthesis of zeolites on steel carrier The survey was based on the following zeolite types: i) MFI-type zeolite. ii) ultrastabilised form of Y zeolite (USY).

Subsequently, dry NH+ 4 -zeolites were calcined in dry air at 450 °C for 8 h with temperature ramp 2 °C/min in order to generate protonic acid sites by the formation of ammonium ions according to the reaction: + NH+ 4 →H . In the case of USY-type zeolite, the procedure was similar. The colloidal silica was added under vigorous stirring to the sodium aluminate, previously dissolved in the sodium hydroxide aqueous solution. The synthesized gel (Na2O:H2O:SiO2:Al2O3 = 283:4323:282:31) was then transferred into a Teflon-lined stainless-steel autoclaves with prepared steel carriers, sealed and kept at room temperature for 24 h. After aging, the autoclaves were transferred to the furnace and hold for the next 24 h at 95 °C under static or dynamic conditions (56 rpm). Obtained systems were rinsed by distilled water and dried at 80 °C in air. At the end, all steel carriers coated with Y type zeolite were weighted carefully with the analytical accuracy. The whole procedure was repeated seven times to determine the mass increase-deposition ratio. As for MFI zeolite, further repetition of faujasite type zeolite (Y) deposition procedure did not cause relevant mass increase of zeolitic layer on steel support. In order to obtain USY-type structure, the triple ion exchange of Y type zeolite with a 0.1 M aqueous ammonium nitrate solution was carried out at 80 °C for 2 h. After washing with distilled water and drying, the NH+ 4 -Y layers deposited on the steel support were steamed at 700 °C for 3 h in a temperature ramp of 2 °C/min. Saturated water vapor at 1.25 kPa and at a flow 50 cm3/min was used. When the temperature was changed (i.e., during heating and cooling), saturated water vapor was replaced by dry air. Finally, the system consisting of USY-type zeolite on the steel carrier was weighted. To obtain a reference sample in form of NH+ 4 -Y zeolite was calcined in dry air at 450 °C for 8 h with temperature ramp of 2 °C/min and flow rate of 50 cm3/min, resulting in the formation of zeolite Y in protonic form (HY). In order to obtain the HMFI zeolite reference sample, the MFI zeolite in sodium form was ion-exchanged triple with a 0.1 M aqueous ammonium nitrate solution at 80 °C for 2 h. Subsequently, both + kinds of ion-exchanged samples (NH+ 4 -MFI and NH4 -Y) were washed three times with distilled water and dried. Afterwards, samples were calcined in dry air under the same conditions as above. In the final step, prepared catalysts were immersed in 0.5 M aqueous copper or cobalt nitrate solution (Sigma Aldrich) at 20 °C for 24 h. Thus obtained, ion-exchanged samples were washed three times with distilled water and dried. Then, the Cu- and Co-zeolites were calcined in dry air at 500 °C for 4 h with temperature ramp of 2 °C/min and flow rate of 50 cm3/min.

2.2. Characterisation of zeolitic coatings For the MFI-type zeolite, the gels of defined chemical composition (Na2O:H2O:SiO2:Al2O3(TPA)2O = 8:4579:192:6:15) were obtained in several steps. Firstly, sodium aluminate (Avantor, p.a) was dissolved in water. Subsequently, a template (tetrapropylammonium hydroxide - TPAOH; 1.0 M, Sigma-Aldrich) and silicon source (tetraethylortosilicate; 98%, Sigma-Aldrich) were added to the sodium aluminate aqueous solutions under vigorous stirring and then aged for 20 h at room temperature. After the aging procedure, the gels were transferred into Teflon-lined stainless-steel autoclaves (containing prepared steel carriers), sealed and kept at 175 °C for 20 h under static or dynamic (56 rpm) conditions. Afterwards, the resulting samples were washed by distilled water and dried at 80 °C in a ventilated oven. After this step, the mass increase of the MFI zeolite on the stainless steel support was determined. The procedure given above was repeated seven times to determine the mass increase-deposition ratio. We made sure that further repetition of deposition procedure did not cause relevant mass increase of zeolitic layer on steel carrier. To remove the organic template (TPAOH) from prepared catalysts samples, calcination at 480 °C for 8 h with a temperature ramp of 2 °C/min was performed. In the next step, template-free samples were triply ion-exchanged with a 0.1 M aqueous ammonium nitrate solution at 80 °C for 2 h.

The X-ray powder diffraction (XRD) was recorded with a PANalytical X'Pert PRO MPD diffractometer at room temperature. The analysis was carried out with CuKα radiation (λ = 1.5418 Å) at 40 kV and 30 mA. The scanning was conducted continuously over a 2θ range from 5 to 50° with a 0.033° step for 12 min. The studied zeolitic samples were in powder form that scraped from the surface of the structured steal carriers. Physisorption of N2 at 77 K was studied using Quantachrome Nova 2000, after activation in vacuum at 300 °C for 20 h. Surface Area (SBET) and micropore volume (Vmicro) were determined by the application of Brunauer-Emmett-Teller (BET) and t-plot methods, respectively. Pore size distribution and meso- and micropores volume (Vmeso, Vmicro) were obtained with using the Barrett-Joyner-Halenda (BJH) model to the adsorption branch of the isotherm. The morphology of the prepared samples was determined by scanning electron microscopy (SEM, FEI Company Nova Nano SEM 200, Hillsboro, OR, USA) in backscattered electron mode. The SEM/EDX mapping experiments were performed using a JEOL 5400 scanning microscope (JEOL USA, Inc., Peabody, MA, USA) with a LINK ISIS microprobe analyser (Oxford Instruments, Tubney Woods Abingdon, Oxfordshire,

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

3

UK). Prior to analysis, the catalyst samples were covered with a carbon layer. The concentrations of Brønsted and Lewis sites were determined by in situ FT-IR sorption studies. Prior to the analysis, the catalyst powders were pressed into self-supporting wafers (ca 20 mg/cm2) and activated under vacuum conditions at 400 °C for 1 h at a temperature ramp of 5 °C/min. After activation, the reference spectrum was recorded at 120 °C. The NH3 (Air Products, 99.95%) was distilled by freeze/thaw cycles before adsorption to remove any traces of moisture and impurities. The NH3 sorption studies were performed at 120 °C in an IR quartz cell with a calibrated dosing bulb. The amount of probe molecules introduced into the IR cell was calculated from the ideal gas law. The concentration of Brønsted and Lewis sites was calculated from the intensities of 1450 cm˗1 and 1620 cm˗1 bands of ammonium ions (NH+ 4 ) and ammonia interacting with Lewis sites (NH3L) using their extinction coefficients equal to 0.12 and 0.026 cm2/mold, respectively. The spectra were recorded using NICOLET iS10 spectrometer equipped with an MCT detector. The spectra resolution was of 4 cm−1. IR experiments were also used in order to determine the status of Cu and Co sites in the studied zeolites. CO and NO (Air Products) were used as probe molecules. The adsorption of NO was performed at room temperature, while adsorption of CO was done at both room temperature and − 100 °C. DRS-UV/VIS spectra were collected using AvaSpec-ULS3648 Highresolution spectrometer equipped with a Praying Mantis HighTemperature Reaction Chamber (Harrick Scientific Co., Ossining, NY) and a high-temperature reflection probe (FCR-7UV400–2-ME-HTX, 7400 μm fibers). As a light source the AvaLight-D(H)-S DeuteriumHalogen Light Source was used. The spectra were registered in the frequency range 200–1000 nm. The instrument was controlled by AvaSoft v 9.0 software. The spectra were collected after dehydration of the samples at 110 °C in helium flow (30 cm3/min). Raman spectra were collected using a μ-Raman confocal microscope (LabRAM HR, Horiba Jobinn Yvonne, France) equipped with a deeply depleted thermoelectrically cooled CCD array detector. Data were registered using long working distance objective of magnification 50×. A sample was placed in a sample holder of a cold-wall CVD microreactor (CCR1000, Linkam Scientific Instruments, fitted with quartz windows). The spectra were collected after first calcination in 450 °C in an air flow and after dehydration at 110 °C in helium flow (30 cm3/min). Raman analysis was carried out using a visible 532-nm green diode laser, 633 nm He\\Ne gas laser and 325 nm HeCd gas laser. The μRaman maps were taken for catalysts revealing best catalytic activity i.e. CoMFI and CuUSY by using Witec Alpha 300 M + confocal Raman microscope equipped 488 nm laser and ZEISS lenses (×10,

×50, ×100). The μRaman maps were collected for 25 μm × 25 μm area for catalysts deposited circular wire gauzes by averaging 40 × 40 points using 600 grating. The adherence of zeolite layer was evaluated by the application of ultrasonic method previously described elsewhere [16]. The method relies on measuring weight loss of the sample treated in ultrasonic bath. The steel carriers covered with the zeolite layers were immersed in acetone, and subjected to ultrasonication (Bandelin, 20 kHz) for 30 min, then dried for 1 h at 80 °C. Differences in the zeolite mass of sample before and after the ultrasonic treatment were a measure to evaluate the mechanical stability of the zeolite layer attached to the steel support. The measurements of catalytic properties of the prepared samples in selective catalytic reduction of NO with NH3 were performed under atmospheric pressure in a fixed-bed quartz microreactor CATLAB system coupled with a quadrupole mass spectrometer (Hiden Analytical). In all cases, obtained zeolites were placed on a quartzwool plug inside the reactor and the reaction was carried out in the temperature range from 50 to 500 °C. Catalytic tests procedure included: i) outgassing the sample in a flow of pure helium at 550 °C for 1 h; ii) cooling the reactor to a temperature of 100 °C; iii) launching the SCR reaction by introducing the gas mixture containing 2500 ppm of NO, 2500 ppm of NH3 and 25,000 ppm of O2 balanced by helium, at a total flow rate of 40 cm3/min and iv) measuring catalytic performance at a selected temperature. The registered m/z during the temperature ramp included: 28 (N2), 30 (NO), 44 (N2O) and 46 (NO2).

Fig. 1. The influence of the stainless steel carrier pretreatment on the efficiency of embedment of zeolite MFI layer: A) static, B) rotational conditions.

Fig. 2. The influence of the stainless steel carrier pretreatment on the efficiency of embedment of zeolite Y/USY layer: A) static, B) rotational conditions.

3. Results and discussion 3.1. Coating efficacy The rate/progress of the zeolite phase deposition on the stainless steel carrier is presented in Figs. 1 and 2. The data presented in Fig. 1a indicated, that the way of steel support pretreatment has an influence on the efficiency of zeolite MFI layering. The highest MFI loadings were recorded for unmodified support, thus only this system was selected for further studies. In turn, the poorest zeolite deposition was found for steel modified either with toluene or hydrochloric acid, that is in contrast to the data reported by Kryca et al. [20]. The discrepancy in the results obtained in this work might be explained by the fact that the authors used Kanthal steel foam as a structured support that evidently influence the preparation effectiveness. It is possible that Kanthal steel foam is characterised by higher roughness in comparison with our stainless steel support. Furthermore, the modification of our stainless steel carrier by toluene and/or hydrochloric acid might lead

4

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

to the smoothing of the surface of the carrier as a result of the removal of some impurities bonded with the support. Apparent decrease of the mass of zeolite on steel support refers to the sample after calcination, which implies the removal of the organic template from the MFI zeolite [1]. Another parameter was the influence of mixing on the zeolite layering progress (Fig. 1b). For the in situ synthesis of MFI type zeolite on stainless steel in rotating autoclaves, the zeolite deposition was independent of the way of the support modification. Direct comparison of static and dynamic conditions leads to the conclusion that static conditions are definitely more efficient. It means that for static autoclaves, the amount of zeolite deposited on steel carrier was much higher as compared to the dynamic conditions. The observed tendency may be explained by the fact that the zeolite gel flowing in the autoclave removes the excess of the crystalline zeolite phase from the surface of the steel carrier. Hence, the accumulation of zeolite on a steel support is limited. This situation does not occur for the static conditions. Opposite conclusions were formed by Shan et al. [21], who investigated the influence of the dynamic conditions during MFI type zeolite layer deposition on stainless steel monoliths. It was shown that the use of rotational autoclaves led to higher coverage than those obtained for static autoclaves. This observation was accounted for by Shan et al. [21] who implied that the movement of zeolite gel during hydrothermal synthesis, for example by rotating the autoclave or by using magnetic stirrer, increased the probability of crystal forming in the liquid phase, instead forming it on the carrier surface. Observed disagreement between our and Shan's results led to the conclusion that in our case, zeolitic phase was weaker bonded with support than the systems obtained by Shan et. a. [21] probably due to lower roughness of stainless steel meshes in relation to stainless steel monoliths. Another parameter controlled upon zeolites deposition was the zeolite structure type. The obtained results given in Fig. 2a showed, that the amount of Y type zeolite over steel support is distinctly higher that of the MFI analogue, when the experiment was performed under static conditions (Fig. 1a). Similar trend was found for the dynamic conditions (Fig. 1b, Fig. 2b). The observed effect may be explained by higher adhesion of zeolite Y (Si/Al = 4.52) to steel in comparison with the MFI (Si/ Al = 15) type zeolite. [15,22–25]. On the other hand, Li et al. [26] examined the deposition of Y, Linde Type A (LTA), mordenite (MOR) and MFI type zeolites on cordierite support. The increase in Si/Al ratio (related to the zeolite structure type) caused the rise in the coverage of a cordierite by a zeolite layer. It may be concluded that the amount of zeolite coating over carrier depends either on the structure of zeolite (Si/ Al ratio) or the type of a structured support that further implies that the deposition efficacy depends on both on the Si amount in the zeolite, as well as the adhesion properties of a structured support and the mass transport phenomena accompanying the deposition process. In the case of Y type zeolite deposition, the pretreatment of steel support also plays a role in the effectiveness of anchoring of zeolite on the steel surface (Fig. 2a, b). As previously noted for MFI zeolite, the highest efficiency of deposition was due to a raw support, thus for further investigations, only unpretreated carriers were chosen. The lowest zeolite content was obtained for support modified only with aqueous HCl solution. Notable decrease of the mass of zeolite on the carrier refers to the sample that was exposed to ultrastabilisation. The application of dynamic conditions for in-situ synthesis of zeolite Y leads to the similar effects as described in the case of MFI zeolite, that means that the static conditions are much more effective. 3.2. Catalyst structural characterisation The X-ray diffraction (XRD) patterns for pure zeolites and Cu and Co modified catalysts prepared using a classical ion exchange method are presented in Fig. 3. The analysis of the diffraction patterns was performed based on the American Mineralogist Crystal Structure Database [27]. The analysis confirmed the MFI and Y (including USY) structures of

Fig. 3. Diffractograms of the copper- and cobalt-substituted zeolites: (A) HMFI, CuMFI and CoMFI samples; (B) HY, CuY and CoY samples; (C) USY, CuUSY and CoUSY samples.

the zeolites for both raw and ion-exchanged samples. For Y and USY zeolites before copper or cobalt exchange, the diffraction peaks are more intense than those observed after ion exchange (Fig. 3b, c). Neither XRD patterns of Cu/Co oxides nor Cu/Co hydroxides were found in all catalyst's samples. It might be concluded that the incorporated copper or cobalt are uniformly distributed within the zeolite structure as cations attached to Al–OH groups [28–31]. The details concerning the samples (names, the Si/Al ratio, metal content, porosity and acidity) are presented in Table 1. Atomic absorption spectroscopy (AAS) results showed that the metal loadings are different on different types of the zeolites. The amount of copper in CuMFI (0.62 wt%) catalyst was 2–3 times lower than the amount of Co in the same zeolite type - CoMFI catalyst (1.60 wt%). Another observation can be made for Y and USY-based catalysts. Both samples contain significantly higher content of copper than cobalt (for Y: Cu- 6.50 wt% vs Co: 3.51 wt%, and for USY: Cu- 4.91 wt% vs Co: 3.41 wt%. In summary, much higher metal loading was found for Y and USY catalysts than for the MFI catalysts. This can be explained by the low Si/Al ratio of the Y and USY zeolite and connected with that higher number of Al-OH groups susceptible to cation exchange [32]. The results of specific surface areas determined by sorption of N2 for the raw zeolites were higher in respect to the cation exchanged samples however, more profound differences were found for the Y and USY than for the MFI-based catalysts. For CuY and CoY (281 m2/g and 371 m2/g, respectively) the decrease reaches almost 50%, as for the pristine Y zeolite sample the specific surface area amounts to 516 m2/g (cf. Table 1). A similar observation can be made when comparing the total pore volume results. The total pore volume measured for the pure zeolite Y, was equal to 0.353 cm3/g, whereas for the Cu- and Co- containing samples it decreased to 0.212 and 0.255 cm3/g, respectively. A possible

Table 1 Catalysts preparation and characterisation details. Sample

Si/Al

Cu or Co content [%]

SBET [m2/g]

Vp total [cm3/g]

Vp micro [cm3/g]

BAS [μmol/g]

LAS [μmol/g]

HMFI CuMFI CoMFI HY CuY CoY USY CuUSY CoUSY

15 15 15 4.52 4.52 4.52 4.52 4.52 4.52

n.a. 0.62 1.60 n.a. 6.50 3.51 n.a. 4.91 3.41

297 283 300 516 281 371 552 440 497

0.246 0.262 0.281 0.353 0.212 0.255 0.376 0.335 0.366

0.124 0.112 0.114 0.261 0.076 0.159 0.246 0.184 0.228

534 229 304 241 49 193 33 21 140

88 355 321 527 2116 887 249 1452 988

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

5

Fig. 4. Scanning electron microscopy (SEM) images of steel carrier with embedded zeolite phase: (A) HMFI (200 μm); (B) HMFI (10 μm); (C) USY (200 μm); (D) USY (10 μm); (E) CuUSY (200 μm); (F) CuUSY (10 μm).

explanation of those decreases found for the Y and USY catalysts can be blocking the pore system by metal oxides that can be formed upon cation exchange [33]. From analysis of porous structure of Y and USY-based samples (Table 1), we can see that CuY and CoY show obvious decrease in surface area and pore volume compared with HY. However, CuUSY and CoUSY show the slight decrease in surface area and pore volume in relation to USY. Observed correlation may be explained by the fact

that the procedure associated with ultrastabilisation (transformation of some framework Al lying at tetrahedral coordination into extraframework Al species)led to the decrease of microporosity, thus some part of Cu or Co was located inside mesopores, which resulted in lower amount of these metal species blocking the accessibility to micropores. The results of specific surface areas and total pore volumes showed relevant correlation between Cu- and Co-containing catalysts.

Fig. 5. Energy-dispersive X-ray spectroscopy (EDS) distribution maps of selected elements over the surface of copper- or cobalt-exchanged zeolites: (A) CuMFI, (B) CuY, (C) CuUSY, (D) CoMFI, (E) CoY, (F) CoUSY. Correspondence of colors and elements: O: red, Na: green, Al: blue, Si: yellow, Cu or Co: violet.

6

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

Fig. 6. In situ micro-Raman spectra of prepared metal-substituted zeolites registered with 632 nm laser illumination after dehydration in 110 °C in pure helium low: A) CuMFI, CuY, CuUSY catalysts; B) CoMFI, CoY, CoUSY catalysts.

For the catalysts of Y and USY structure, all presented values were notably higher for Co-zeolite. For the MFI-based catalysts, neither the introduction of Cu nor Co led to apparent changes in the distribution of pores. The FTIR results of the NH3 chemisorption on the samples referring to the assessment of the active sites are presented in Table 1. A significant difference can be noted between prepared samples. For USY and Y zeolites, the concentration of Brønsted acid sites was between 21 and 241 μmol/g, whereas for the MFI zeolites this value was significantly higher, between 229 and 534 μmol/g. Aluminosilicates characterised by low Si/Al ratio (like Y type zeolites) are susceptible to easy dehydroxylation of acidic OH groups in close vicinity to one another. As a result Lewis acidic sites on aluminum cations are formed [34–36]. Generally, the incorporation Cu or Co cations led to distinct decrease of the concentration of Brønsted acid sites that is rather obvious taking into account the acid-base Brønsted reaction that occurs upon cation exchange. One exception was CoUSY, for which a huge increase from 33 to 140 μmol/g was observed. This phenomenon seems to be difficult to explain at this moment. In addition, for Cu-catalysts, a decrease

of the concentration of Brønsted acid sites was more evident in comparison with Co-analogues. The detailed analysis of the Lewis acid sites concentration allows for clear correlation between zeolite structure and the acidic properties. The Lewis site concentration was considerably higher in Y and USY catalysts than for MFI catalysts, that corresponds to the low Si/Al ratio. On the other hand, higher cation exchange capacity for zeolites of low Si/Al ratio should correlate with higher Cu or Co loading. For all studied samples (both MFI and Y/USY-based catalysts), the incorporation Cu or Co cations led to distinct increase of the concentration of Lewis acid sites, especially for Cu containing samples [37–39]. Scanning electron microscopy (SEM) (Fig. 4) was used for the examination of the morphology of prepared catalysts. The SEM images were obtained in the backscattered electron mode (BSE). In all cases, uniform distribution of zeolite layer over steel support was found. Furthermore, apparent border between zeolite layer and steel carrier was observed, thus the presence of zeolite phase supported on still carrier was evidenced (Fig. 4 a, 4c, 4e). The thickness of zeolitic layer is ca. 40–50 μm. Another observation is that the MFI, Y and USY-based catalysts are of spherical-like shape [40]. The spatial distribution of the selected elements (Si, Al, Na, Cu and Co) within the samples is illustrated in Fig. 5. The analysis of EDS maps implies that in all samples, the incorporated copper or cobalt are uniformly distributed over zeolites. The results of the structural characterisation of prepared catalyst samples by in situ Raman spectroscopy are presented in Fig. 6. When considering copper containing catalysts, the bands at 275, 330, 384, and 825 cm−1 can be assigned to the vibrations related to zeolite structure [41,42]. Moreover, the presence of bands at 275, 330, 621 and at 720 cm−1 reflect the vibrations originating from CuO and/or from Cu2O phase [43–46]. In the case of Y and USY-based catalysts, the presence of the band at 496 cm−1 might be associated with Cu3O4 species [43–46]. Fig. 6b shows the in situ Raman spectra of Co-zeolites. As can be seen, the bands at 187, 477, 530, 615 and 680 cm−1 are attributed to Co3O4 agglomerates, which were not detected by XRD [47]. The results of the μRaman mapping are presented in Fig. 7 and Fig. 8 for CoMFI and CuUSY catalysts, respectively. The corresponding Raman spectra for individual Raman map colors are presented in Fig. 7a and Fig. 8a for CoMFI and CuUSY catalysts, respectively. The μRaman analysis of the CoMFI exhibited the presence of the bands at 415, 445, 609, 690 and 800 cm−1. The bands at 415, 445 and 609 cm−1 may be

Fig. 7. Raman maps for CoMFI catalyst.

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

Fig. 7a. Raman spectra for corresponding Raman maps in this figure.

attributed to the α-Fe2O3 originating from the wire gauze support [48]. The additional band at ca. 800 cm−1 may be attributed to zeolite framework. The band at 690 cm−1 is characteristic for cobalt in spinel Co3O4 form [49]. It must be emphasized, that the Raman map exhibit that

7

the cobalt impregnation on the MFI catalysts results in complete surface coverage with spinel type cobalt oxide (green color). Indeed some defects in surface coverage may be observed as in a form of α-Fe2O3, however it must be also pointed out that despite the fact that the α-Fe2O3 bands may be observed, the Raman spectra (green) also reveal weak signals from zeolite structure. This phenomenon may be related with local crack in zeolite layer which allow for detection of α-Fe2O3 from wire gauze structure. The Raman maps and corresponding Raman spectra of the CuUSY sample are presented in Fig. 8 and 8a, respectively. The blue spot at the Raman map relates to the α-Fe2O3 with the characteristic 265, 415 and 605 cm−1 bands [48]. While the red color at the Raman maps correspond with the presence of CuO with the bands at 295, 343 cm−1 [50]. The additional band appear at 380 cm−1 which correspond with E1g of α-Fe2O3. The band originating from zeolite structure appearing at 800 cm−1 is still visible at Raman spectrum. The DRS-UV/VIS spectra of the Cu containing catalysts are shown in Fig. 9a. The maxima at ca 230–240 nm as well as broad and weak bands between 550 and 1000 nm were found. It was reported in [47] that the signal at 230–240 nm may correspond to Cu2+ interacting with oxygen atoms in the zeolite structure (charge transfer O– N Cu transmission). The band between 550 and 1000 nm with a maximum at ca 850 nm might be assigned to CuO [47,51]. In the DRS-UV/VIS spectra of Co - catalysts (Fig. 9b), the bands at 250–260 nm, 275–280 nm and between 450 and 900 nm are observed. The maxima at 250 and 275 nm (for MFI), as well as at 260 and 280 nm (for Y and USY) correspond to Co2 + that are exchanged in the zeolite and oxygen-to-metal charge transfer (CT) transition, respectively. For CoMFI, the broad signal at 425–600 nm with maximum at 530 nm is attributed to Co3O4 oxide [47], while the broad signal in the range of 600–900 nm with a maximum at 720 nm originates from surface Co2+/Co3+ species [52]. In the case of CoY or CoUSY, in the broad band at 450–900 nm, small maxima at ca 550, 610 and 660 nm can be distinguished, which may be associated with isolated tetrahedral Co(II) species and attributed to 4A2– N 4 T1 (4P),4A2– N 4 T1 (4F), and 4A2– N 4 T2 transitions, respectively [30]. In order to determine the structure of Cu sites present in the examined samples (CuMFI, CuUSY and CuY), the FT-IR experiments were conducted. CO and NO were applied as probe molecules at both −100 °C and room temperature (Fig. 10 and Fig. 11). When CO was sorbed at room temperature for Cu-containing zeolites, the presence of two maxima at 2158 cm−1 and 2144 cm−1 was found (Fig. 10A). These bands are assigned to Cu+ reacting with CO molecule in both exchange

Fig. 8. Raman maps for CuUSY catalyst.

8

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

existence of bands at 2141–48 cm−1 (depending on the zeolite) confirmed the presence of Cu+ in oxide form (Cu+ oxo-CO). The sorption of CO performed at −100 °C over Co-zeolites led to the appearance of the bands at 2206 cm−1 and 2192 cm−1 (Fig. 10C). These maxima reflect the occurrence of Co2+ in both exchange positions (Co2+ exch-CO) and oxide form (Co2+ oxo-CO), respectively [55,56]. The band of 2175 cm−1 comes from acidic OH groups from zeolite [54]. FT-IR results received from the adsorption of NO over Cu-zeolites resulted in the appearance of the bands at 1813 cm−1, 1903–1909 cm−1 and at 1945 cm−1 (Fig. 11A). These maxima revealed the formation of nitrosyls of Cu+, Cu2+ and Cu3+, respectively. The Cu3+ cations were produced as a result of disproportionation of Cu2+ ions from associated species: Cu2+–O–Cu2+ → Cu+–O–Cu3+. In the presence of NO, the Cu3 + –NO complexes are reduced to Cu+–NO and Cu2+–NO. According to Tortorelli et al. [57] Cu+ sites are formed during interaction of Cu2+ ions with NO and the ability of Cu3+ ions to form dinitrosyls favor the hypothesis that dinitrosyl species are intermediates in NO decomposition. The spectra of NO sorbed in Co-zeolites are presented in Fig. 11B. The frequencies of Co2+–(NO)2 for Co2+ in CoY and CoUSY (1833 cm−1, 1905 cm−1) are higher than for CoMFI (1813 cm−1, 1897 cm−1, [55,56,58]). It may be suggested that π- back donation is ruled not only by the concentration of negative (AlO4)− tetrahedra but also by geometric factor which seems to be even more important than the framework composition. For CoMFI a distinct bands at ca 1940 cm−1 and 1960 cm−1 were found, which may be attributed to Co3+–NO species [55,56,58]. Co3+ exists in the forms of ill-defined oxides [55,58]. In our case, for CoY and CoUSY the intensity of Co3+–NO was difficult to see, which may be caused too small accessibility of Co3+ to NO molecules. 3.3. Mechanical endurance

Fig. 8a. Raman spectra for corresponding Raman maps in this figure. + positions (Cu+ exch-CO) and oxide form (Cuoxo-CO), respectively [53]. The same types of Cu+ species (i.e. Cu+ and Cu+ exch oxo) were found, when we performed sorption of CO at −100 °C (Fig. 10B). The bands at 2192 cm−1 and at 2169 cm−1 may originate from tricarbonyls Cu+ exch(CO)3 formed at higher CO loadings as well as may come from extraframework species of Al from zeolite structure, respectively [53]. The band at 2174 cm−1 corresponds to dicarbonyls Cu+ exch(CO)2 or may be also attributed to Si-OH-Al groups existing in zeolite [54]. The co-

The mechanical endurance of the synthetized zeolite layers over stainless steel support was determined from the weight loss after ultrasonic treatments of zeolite-stainless steel composites. The results obtained for both MFI and USY-based samples are shown in Fig. 12. Ultrasound irradiation of zeolites deposited over the carriers resulted in the mass loss (not exceeding 50%). This results is comparable with the results obtained by Asakura et al. [17] and Kryca et al. [20]. Somewhat worse mechanical endurance of USY-based samples may be explained by a partially breached structure of faujasite as a result of its ultrastabilisation, which probably led to an elevated sensitivity of USY zeolitic layer to any modification (including ultrasonic irradiation). Obtained results revealed the difference of adherence strength of the zeolite layers depending both on their structure type (MFI vs. USY) and the type of exchanges metal (Cu vs. Co). 3.4. Catalytic performance

Fig. 9. In situ diffuse reflectance UV/visible (UV/Vis) spectra of prepared metal-substituted zeolites: A) CuMFI, CuY, CuUSY catalysts; B) CoMFI, CoY, CoUSY catalysts.

The activity of Cu or Co exchanged USY and MFI zeolites deposited over stainless steel carriers during the SCR of NO was tested. The results are presented in Fig. 13. The reaction was run in the temperature range of 100–500 °C. It can be noted that the catalytic activity of the copper catalysts depends either on temperature or the zeolite structure type. For example at 400 °C. NO conversion was 30%, 45% and 50% for CuMFI, CuUSY and CuY, respectively. Their selectivity to N2 was between 75 and 80%. Poor catalytic properties of CuMFI come from low copper loading resulting in small concentration of Lewis acid sites related to copper cation which are necessary for the reaction to occur (Table 1). Let us note that among Cu-containing samples, CuMFI shows the highest concentration of Brønsted acid sites and only for this sample deactivation did not occur above 450 °C. In the case of Cu\\Y and CuUSY samples, slightly better catalytic properties correspond to higher copper content (thus higher of Lewis and lower of Bronsted acid sites concentrations).

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

9

Fig. 10. IR spectra of CO adsorbed on: A) Cu-zeolites at room temperature; B) Cu-zeolites at −100 °C; C) Co-zeolites at −100 °C.

Catalytic performance of CuUSY and CuMFI in NOx abatement with ammonia was widely discussed in the literature. According to Ochońska et al. [59], the ultrastabilised catalyst (CuUSY) revealed high activity at low temperature as well as good hydrothermal resistance, which may be connected with the abundance of the Lewis (Cu+ to Cu2+) sites and their distribution. High activity of the CuY and CuUSY catalysts at low temperatures (in comparison with CuMFI) may be associated with the presence of the Cu+ active sites, having a low binding energy with NO molecules. In the available literature review [60], many opinions concerning the role of Cu+ and Cu2+ active sites within the zeolite structure in the NH3-SCR process can be found. Some authors claim that only Cu+ is active in the NH3-SCR process, meanwhile in many cases it was shown that the Cu2+ sites are necessary for the oxidation of NO to a NO2 intermediate - a rate determining step in the NH3-SCR mechanism [61]. The catalysts modified with cobalt revealed much worse catalytic properties in comparison with their copper counterparts. The most

active catalyst was CoUSY, for which NO conversion achieved 35% at 450 °C. All investigated Co-catalysts underwent deactivation at the higher temperatures. The highest selectivity to N2 was found in the case of CoMFI and varied between 65 and 70% throughout the tested temperature range. For both Y and USY-based catalysts a selectivity to N2 drop can be noted from 55% to 50% with temperature raising from 100 °C to 500 °C. However, in the literature, Co-zeolites were reported as catalysts for selective catalytic reduction of NOx mainly with methane or higher hydrocarbons used as reducing agents both in the presence and absence of excess of oxygen [62–64]. Bin et al. [52] performed the SCR of NO with ammonia on CoMFI and CoSBA-15 catalyst. In turn, Boroń et al. [65,66] tested CoBEA zeolite. However, direct comparison of Cu- or Co-MFI as well as Cu- or Co-Y/USY as catalysts for DeNOx process with ammonia have not been well documented. Poor catalytic properties of Co-zeolites in comparison with Cu analogues can be related to their acidic properties. In all cases, Co-samples show higher concentration of Brønsted acid sites and lower cobalt loading (thus concentration of Lewis acid sites) in relation to their Cu counterparts (Table 1). Furthermore, the presence of cobalt cation partly in oxide form may be responsible for weak catalytic activity and selectivity to N2.

Fig. 11. IR spectra of NO adsorbed on: A) Cu-zeolites at room temperature; B) Co-zeolites at room temperature.

Fig. 12. Mechanical strength measurements of zeolite layers deposited on stainless steel performed using ultrasonic treatment 20 kHz for 30 min in acetone.

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

10

Fig. 13. Catalytic properties of prepared metal-containing zeolites: A) CuMFI, CuY, CuUSY, B) CoMFI, CoY, CoUSY in the removal of NO.

4. Summary and conclusions In this study, the MFI, Y and USY type zeolite thin layers were synthesized in situ over stainless steel supports under various conditions. The highest amounts of either MFI or Y/USY zeolite phase were due to unmodified steel carrier without any pretreatment. It was also found that the efficiency of the layering notwithstanding the zeolite type is higher when the zeolite growth is performed in static conditions without any mixing. Moreover, it was noted that the zeolite structure plays an important role in the efficacy of zeolite embedment over steel carrier. The amount of Y and USY zeolite is notably higher in comparison with MFI, probably due to higher adhesion of zeolite Y connected with higher amount of exposed Al-OH groups, which is associated with low Si/Al ratio (4.52) comparing to MFI (Si/Al = 15). The results of mechanical endurance tests by ultrasonication demonstrated that the adhesion of the in situ deposited layers is satisfying and corresponds to the results of zeolite phase deposition efficacy on stainless steel carrier. The analysis of physicochemical data led to the conclusion that deposited zeolite phase exhibit high crystallinity, porosity and acidity properties. All determined physicochemical properties of zeolite layers were strongly influence by their topological structure (MFI vs. Y/USY) and the type of introduced metal species. The optimized in situ zeolite preparation over metallic supports may be successfully used to prepare active catalytic systems for SCR deNOx. The performed catalytic tests indicated both catalytic activity or selectivity to N2 the studied catalysts depend the type of zeolite structure and the type of introduced metal. The catalysts modified with copper revealed much better catalytic properties in comparison with their cobalt counterparts. It was found that among Cu-containing samples, CuMFI revealed the highest concentration of Brønsted acid sites and only for this sample deactivation did not take place above 450 °C. For CuY and CuUSY samples, slightly better catalytic properties are related to higher copper content (thus higher of Lewis and lower of Bronsted acid sites concentrations). Worse catalytic properties of Co-zeolites in comparison with Cu counterparts might imply from their acidic properties. In all cases, Cosamples show higher concentration of Brønsted acid sites and lower cobalt loading (thus concentration of Lewis acid sites) in relation to their

Cu analogues. Furthermore, the presence of cobalt cation partly in oxide form may be responsible for weak catalytic activity and selectivity to N2. Preliminary catalytic results showed clearly that prepared systems prompt to further studies on mechanistic aspects of SCR deNOx reaction to reveal the exact correlation between acidity-activity properties. CRediT authorship contribution statement Ł. Kuterasiński:Formal analysis, Investigation, Writing - original draft, Writing - review & editing.P. Bodzioch:Formal analysis, Investigation.K. Dymek:Formal analysis, Investigation.R.J. Jędrzejczyk:Formal analysis, Investigation.D.K. Chlebda:Formal analysis, Investigation.J. Łojewska:Formal analysis.M. Sitarz:Formal analysis, Investigation.G. Kurowski:Formal analysis, Investigation.P. Jeleń:Formal analysis, Investigation.P.J. Jodłowski:Formal analysis, Investigation, Data curation, Writing - review & editing. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements The Project was financed by National Centre for Research and Development No LIDER/204/L-6/14/NCBR/2015. The authors would like to thank Monika Hanula for technical support during the AAS analyses. References [1] C.S. Cundy, P.A. Cox, The hydrothermal synthesis of zeolites: precursors, intermediates and reaction mechanism, Microporous Mesoporous Mater. 82 (2005) 1–78, https://doi.org/10.1016/j.micromeso.2005.02.016. [2] R.M. Barrer, Zeolites and their synthesis, Zeolites 1 (1981) 130–140, https://doi.org/ 10.1016/S0144-2449(81)80001-2. [3] A. Cybulski, J.A. Moulijn, Monoliths in heterogeneous catalysis, Catal. Rev. Sci. Eng. 36 (1994) 179–270, https://doi.org/10.1080/01614949408013925.

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060 [4] P.J. Jodłowski, R. Gołąb, J. Kryca, a. Kołodziej, M. Iwaniszyn, S.T. Kolaczkowski, A comparison between monolithic and wire gauze structured catalytic reactors for CH4 and CO removal from biogas-fuelled engine exhaust, Top. Catal. 56 (2013) 390–396, https://doi.org/10.1007/s11244-013-9985-5. [5] P. Avila, M. Montes, E.E. Miró, Monolithic reactors for environmental applications: a review on preparation technologies, Chem. Eng. J. 109 (2005) 11–36, https://doi. org/10.1016/j.cej.2005.02.025. [6] A. Cybulski, J.A. Moulijn, Structured Catalysts and Reactors, Taylor & Francis, 2006https://doi.org/10.1201/9781420028003. [7] V. Meille, Review on methods to deposit catalysts on structured surfaces, Appl. Catal. A Gen. 315 (2006) 1–17, https://doi.org/10.1016/j.apcata.2006.08.031. [8] A. Kuperman, S. Nadimi, S. Oliver, G.A. Ozin, J.M. Garces, M.M. Olken, Non-aqueous synthesis of giant crystals of zeolites and molecular sieves, Nature 365 (1993) 239, https://doi.org/10.1038/365239a0DO. [9] H.P.A. Calis, A.W. Gerritsen, C.M. van den Bleek, C.H. Legein, J.C. Jansen, H. van Bekkum, Zeolites grown on wire gauze: a new structured catalyst packing for dustproof, low pressure drop denox processes, Can. J. Chem. Eng. 73 (1995) 120, https://doi.org/10.1002/cjce.5450730113. [10] T. Bein, Chem. Mater. 8 (1996) 1636–1653, https://doi.org/10.1021/cm960148a. [11] J.C. Jansen, E.N. Coker, Zeolitic membranes, Curr. Opinion Solid State Mater. Sci. 1 (1996) 65, https://doi.org/10.1016/S1359-0286(96)80012-X. [12] Y. Yan, S.R. Chaudhuri, A. Sarkar, Synthesis of oriented zeolite molecular sieve films with controlled morphologies, Chem. Mater. 8 (1996) 473–479, https://doi.org/10. 1021/cm950393e. [13] L. Medvecky, J. Mihalik, J. Briancin, Possibilities of coating of glass with synthetic zeolites, J. Mater. Sci. Lett. 12 (1993) 907, https://doi.org/10.1007/BF00455614. [14] R.K. Grasselli, R.M. Lago, R.F. Socha, J.G. Tsikoyiannis, Synthesis of zeolite films bonded to substrates, structures and uses thereof, US Patent 5,310,714 (1994). [15] E.V. Rebrov, G.B.F. Seijger, H.P.A. Calis, M.H.J.M. de Croon, C.M. van den Bleek, J.C. Schouten, Preparation of highly ordered single layer ZSM-5 coating on prefabricated stainless steel microchannels, Appl. Catal. A Gen. 206 (2001) 125–143, https://doi. org/10.1016/S0926-860X(00)00594-9. [16] J. Ochońska, A. Rogulska, P.J. Jodłowski, M. Iwaniszyn, M. Michalik, W. Łasocha, A. Kołodziej, J. Łojewska, Prospective catalytic structured converters for NH3-SCR of NOx from biogas stationary engines: in situ template-free synthesis of ZSM-5 Cu exchanged catalysts on steel carriers, Top. Catal. 56 (2013) 56–61, https://doi.org/10. 1007/s11244-013-9929-0. [17] H. Asakura, C.D. Madhusoodana, Y. Kameshima, A. Nakajima, K. Okada, Zeolite coating on foamed stainless steel by in situ crystallization method, J. Electroceram. 17 (2006) 31–36, https://doi.org/10.1007/s10832-006-9931-z. [18] L. Bonaccorsi, E. Proverbio, A. Freni, G. Restuccia, In situ growth of zeolites on metal foamed supports for adsorption heat pumps, J. Chem. Eng. Japan 40 (2007) 1307–1312, https://doi.org/10.1252/jcej.07WE174. [19] G. Clet, J.C. Jansen, H. Van Bekkum, Synthesis of a zeolite Y coating on stainless steel support, Chem. Mater. 11 (1999) 1696–1702, https://doi.org/10.1021/ cm980751o. [20] J. Kryca, P.J. Jodłowski, M. Iwaniszyn, B. Gil, M. Sitarz, A. Kołodziej, T. Łojewska, J. Łojewska, Cu SSZ-13 zeolite catalyst on metallic foam support for SCR of NOx with ammonia: catalyst layering and characterisation of active sites, Catal. Today 268 (2016) 142–149, https://doi.org/10.1016/j.cattod.2015.12.018. [21] Z. Shan, W.E.J. van Kooten, O.L. Oudshoorn, J.C. Jansen, H. van Bekkum, C.M. van den Bleek, H.P.A. Calis, Optimization of the preparation of binderless ZSM-5 coatings on stainless steel monoliths by in situ hydrothermal synthesis, Microporous Mesoporous Mater. 34 (2000) 81–91, https://doi.org/10.1016/S1387-1811(99)00161-4. [22] S.B. Derouane-Abd Hamid, P. Pal, H. He, E.G. Derouane, Propane ammoxidation over Ga-modified zeolites, Proceedings of the 4th European Congress on Catalysis, Europacat-4, Rimini, Italy 1999, p. 14. [23] Y. Li, J.N. Armor, A reaction pathway for the ammoxidation of ethane and ethylene over co-ZSM-5 catalyst, J. Catal. 176 (1998) 495–502, https://doi.org/10.1006/jcat. 1998.2089. [24] J.C. van der Waal, E.J. Creyghton, P.J. Kunkeler, K. Tan, H. van Bekkum, Beta-type zeolites as selective and regenerable catalysts in the Meerwein–Ponndorf–Verley reduction of carbonyl compounds, Top. Catal. 4 (1997) 261, https://doi.org/10.1023/ A:1019160827175. [25] K.G. Davenport, R.A. Sheldon, J. LeBass, W.H. Werner, US Patent 5,466,869 (1995). [26] L. Li, B. Xue, J. Chen, N. Guan, F. Zhang, Direct Synthesis of Zeolite Coatings on Cordierite Supports by In Situ Hydrothermal Method, vol. 292, 2005 312–321, https://doi. org/10.1016/j.apcata.2005.06.015. [27] R.T. Downs, M. Hall-Wallace, The American mineralogist crystal structure database, Am. Mineral. 88 (2003) 247–250. [28] B. Pereda-Ayo, U. De La Torre, M. JoséIllán-Gómez, A. Bueno-López, J.R. GonzálezVelasco, Role of the different copper species on the activity of cu/zeolite catalysts for SCR of NOx with NH3, Appl. Catal. B 147 (2014) 420–428, https://doi. org/10.1016/j.apcatb.2013.09.010. [29] J.Y. Yan, G.D. Lei, W.M.H. Sachtler, H.H. Kung, Deactivation of Cu/ZSM-5 catalysts for lean NOx reduction: characterization of changes of Cu state and zeolite support, J. of Catal. 161 (1996) 43–54, https://doi.org/10.1006/jcat.1996.0160. [30] J. Janas, T. Machej, J. Gurgul, R.P. Socha, M. Che, S. Dzwigaj, Effect of Co content on the catalytic activity of CoSiBEA zeolite in the selective catalytic reduction of NO with ethanol: nature of the cobalt species, Appl. Catal. B 75 (2007) 239–248, https://doi.org/10.1016/j.apcatb.2007.07.029. [31] L.D. Li, Q. Shen, J.J. Yu, Z.P. Hao, Z.P. Xu, G.Q.M. Lu, Fe-USY zeolite catalyst for effective decomposition of nitrous oxide, Environ. Sci. Technol. 41 (2007) 7901–7906, https://doi.org/10.1021/es071779g. [32] J. Weitkamp, Zeolites and catalysis, Solid State Ionics 131 (2000) 175–188, https:// doi.org/10.1016/S0167-2738(00)00632-9.

11

[33] K. Lee, H. Kosaka, S. Sato, T. Yokoi, B. Choi, D. Kim, Effects of Cu loading and zeolite topology on the selective catalytic reduction with C3H6 over Cu/zeolite catalysts, J. Industrial and Eng. Ch. 72 (2019) 73–86, https://doi.org/10.1016/j.jiec.2018.12.005. [34] J. Datka, M. Kawałek, Strength of Brønsted acid sites in boralites, J. Chem. Soc. Faraday Trans. 89 (1993) 1829–1831, https://doi.org/10.1039/FT9938901829. [35] T. Yashmina, K. Yamazaki, H. Ahmad, M. Katsuta, N. Hara, Alkylation on synthetic zeolites: II. Selectivity of p-xylene formation, J. Catal. 17 (1970) 151–156, https://doi. org/10.1016/0021-9517(70)90088-6. [36] D. Freude, T. Frochlich, M. Hunger, H. Pfeifer, G. Scheler, NMR studies concerning the dehydroxylation of zeolites HY, Chem. Phys. Lett. 98 (1983) 263–266, https://doi. org/10.1016/0009-2614(83)87162-0. [37] K. Brylewska, K.A. Tarach, W. Mozgawa, Z. Olejniczak, U. Filek, K. Góra-Marek, Modification of ferrierite through post-synthesis treatments. Acidic and catalytic properties, J. Mol. Struct. 1126 (2016) 147–153, https://doi.org/10.1016/j.molstruc.2015. 12.046. [38] L. Chmielarz, P. Kuśtrowski, M. Zbroja, B. Gil-Knap, J. Datka, R. Dziembaj, SCR of NO by NH3 on alumina or titania pillared montmorillonite modified with Cu or Co part II. Temperature programmed studies, Appl. Catal. B 53 (2004) 47–61, https://doi. org/10.1016/j.apcatb.2004.04.019. [39] M. Rutkowska, U. Diaz, A.E. Palomares, L. Chmielarz, Cu and Fe modified derivatives of 2D MWW-type zeolites (MCM-22, ITQ-2 and MCM-36) as new catalysts for DeNOx process, Appl. Catal. B 168-169 (2015) 531–539, https://doi.org/10.1016/j. apcatb.2015.01.016. [40] S. Keerthana, S. Agilan, N. Muthukumarasamy, R. Balasundaraprabhu, D. Velauthapillai, Synthesis and characterization of zeolite NaA and NaY coating on mild steel, J. Sol-Gel Sci. Technol. 79 (2016) 510–519, https://doi.org/10.1007/ s10971-016-4094-0. [41] Y. Yu, G. Xiong, C. Li, F. Xiao, Characterization of aluminosilicate zeolites by UV Raman spectroscopy, Microporous Mesoporous Mater. 46 (2001) 23–34, https:// doi.org/10.1016/S1387-1811(01)00271-2. [42] P.P. Knops-Gerrits, D.E. De Vos, E.J.P. Feijen, P.A. Jacobs, Raman spectroscopy on zeolites, Microporous Mater 8 (1997) 3–17. [43] J.F. Xu, W. Ji, Z.X. Shen, W.S. Li, S.H. Tang, X.R. Ye, D.Z. Jia, X.Q. Xin, Raman spectra of CuO nanocrystals, J. Raman Spectrosc. 415 (1999) 413–415, https://doi.org/10.1002/ (SICI)1097-4555(199905)30:5b413::AID-JRS387N3.0.CO;2-N(Cited by: 214ePDFPDF). [44] Lung - Chieh Chen, Cheng-Chiang Chen, Kai-Chieh Liang, Sheng Hsiung Chang, ZhongLiang Tseng, Shih-Chieh Yeh, Chin-Ti Chen, Wen-Ti Wu, Chun-Guey Wu, Nano-structured CuO-Cu2O complex thin film for application in CH3NH3 PbI3 Perovskite solar cells, Nanoscale Res. Lett. 11 (2016) 402, https://doi.org/10.1186/s11671016-1621-4. [45] Y. Deng, A.D. Handoko, Y. Du, S. Xi, B.S. Yeo, In situ Raman spectroscopy of copper and copper oxide surfaces during electrochemical oxygen evolution reaction: Identyfication of cu III oxides as catalytically active species, ACS Catal. 6 (2016) 2473–2481, https://doi.org/10.1021/acscatal.6b00205. [46] M. Rashad, M. Rüsing, G. Berth, K. Lischka, A. Pawlis, CuO and Co3O4 nanoparticles: synthesis, characterizations, and Raman spectroscopy, J. Nanomater. (2013) 1–6, https://doi.org/10.1155/2013/714853. [47] R. Martins, R. Peguin, E. Urquieta, Cu and Co exchanged ZSM-5 zeolites — activity towards NO reduction and hydrocarbon oxidation, Quim Nova 29 (2006) 223–229, https://doi.org/10.1590/S0100-40422006000200009. [48] L. Wang, X. Lu, C. Han, R. Lu, S. Yang, X. Song, Electrospun hollow cage-like α-Fe2O3 microspheres: synthesis, formation mechanism, and morphology-preserved conversion to Fe nanostructures, Cryst. Eng. Comm. 16 (2014) 10618–10623, https:// doi.org/10.1039/C4CE01485E. [49] A. Diallo, A.C. Beye, T.B. Doyle, E. Park, M. Maaza, Green synthesis of Co3O4 nanoparticles via Aspalathus linearis: physical properties, Green Chem. Lett. Rev. 8 (2015) 30–36, https://doi.org/10.1080/17518253.2015.1082646. [50] A.P. Litvinchuk, A. Möller, L. Debbichi, P. Krüger, M.N. Iliev, M.M. Gospodinov, Second-order Raman scattering in CuO, J. Phys. Condens. Matter. 25 (2013) 105402–105406, https://doi.org/10.1088/0953-8984/25/10/105402. [51] L. Li, F. Zhang, N. Guan, M. Richter, R. Fricke, Selective catalytic reduction of NO by propane in excess oxygen over IrCu-ZSM-5 catalyst, Catal. Commun. 8 (2007) 583–588, https://doi.org/10.1016/j.catcom.2006.08.013. [52] Feng Bin, Chonglin Song, Gang Lv, Jinou Song, Xiaofeng Cao, Huating Pang, Kunpeng Wang, Structural characterization and selective catalytic reduction of nitrogen oxides with ammonia: a comparison between Co/ZSM-5 and Co/SBA-15, J. Phys. Phem. C 116 (2012) 26262–26274, https://doi.org/10.1021/jp303830x. [53] K. Góra-Marek, A.E. Palomares, A. Glanowska, K. Sadowska, J. Datka, Copper sites in zeolites — quantitative IR studies, Microporous and Mesoporous Mater 162 (2012) 175–180, https://doi.org/10.1016/j.micromeso.2012.06.029. [54] J. Datka, B. Gil, T. Domagała, K. Góra-Marek, Homogeneous OH groups in dealuminated HY zeolite studied by IR spectroscopy, Microporous and Mesoporous Mater 47 (2001) 61–66, https://doi.org/10.1016/S1387-1811(01)00314-6. [55] K. Góra-Marek, H. Mrowec, S. Walas, Cobalt sites in zeolites FAU — IR investigations, J. Mol. Str. 923 (2009) 67–71, https://doi.org/10.1016/j.molstruc.2009.01.054. [56] K. Góra-Marek, B. Gil, J. Datka, Quantitative IR studies of the concentration of Co2+ and Co3+ sites in zeolites CoZSM-5 and CoFER, Appl. Catal. A 353 (2009) 117–122, https://doi.org/10.1016/j.apcata.2008.10.034. [57] M. Tortorelli, K. Chakarova, L. Lisi, K. Hadjiivanov, Disproportionation of associated Cu2+ sites in Cu-ZSM-5 to Cu+ and Cu3+ and FTIR detection of Cu3+(NO)x (x = 1, 2) species, J. Catal. 309 (2014) 376–385, https://doi.org/10.1016/j.jcat.2013.10. 018. [58] K. Góra-Marek, B. Gil, M. Sliwa, J. Datka, An IR spectroscopy study of Co sites in zeolites CoZSM-5, Appl. Catal. A Gen. 330 (2007) 33, https://doi.org/10.1016/j.apcata. 2007.06.033.

12

Ł Kuterasiński et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 230 (2020) 118060

[59] J. Ochońska, D. McClymont, P.J. Jodłowski, A. Knapik, B. Gil, W. Makowski, W. Łasocha, A. Kołodziej, S.T. Kolaczkowski, J. Łojewska, Copper exchanged ultrastable zeolite Y—a catalyst for NH3-SCR of NOx from stationary biogas engines, Catal. Today 191 (2012) 6–11, https://doi.org/10.1016/j.cattod.2012.06.010. [60] M. Iwamoto, Air pollution abatement through heterogeneous catalysis, Stud. Surf. Sci. and Catal. 130 (2000) 23–47, https://doi.org/10.1016/S0167-2991(00)80943-X. [61] S. Brandenberger, O. Kröcher, Oliver, A. Tissler, R. Althoff, The state of the art in selective catalytic reduction of NOx by ammonia using metal-exchanged zeolite catalysts, Catal. Rev.-Sci. Eng. 50 (2008) 492–531, https://doi.org/10.1080/ 01614940802480122. [62] B.J. Adelman, T. Beutel, G.D. Lei, W.M.H. Sachtler, Mechanistic cause of hydrocarbon specificity over Cu/ZSM-5 and Co/ZSM-5 catalysts in the selective catalytic reduction of NOx, J. Catal. 158 (1996) 327–335, https://doi.org/10.1006/jcat.1996.0031. [63] Y. Li, J.N. Armor, Catalytic reduction of nitrogen oxides with methane in the presence of excess oxygen, Appl. Catal. B 1 (1992) L31–L40, https://doi.org/10.1016/ 0926-3373(92)80050-A.

[64] F. Seyedeyn-Azad, D. Zhang, Selective catalytic reduction of nitric oxide over Cu and Co ion-exchanged ZSM-5 zeolite: the effect of SiO2/Al2O3 ratio and cation loading, Catal. Today 68 (2001) 161–171, https://doi.org/10.1016/S0920-5861(01)00308-X. [65] P. Boroń, L. Chmielarz, B. Gil, B. Marszałek, S. Dźwigaj, Experimental evidence of NOSCR mechanism in the presence of the BEA zeolite with framework and extraframework cobalt species, Appl. Catal B 198 (2016) 457–470, https://doi.org/10. 1016/j.apcatb.2016.06.012. [66] P. Boroń, L. Chmielarz, S. Casale, C. Calers, J.M. Krafft, S. Dźwigaj, Effect of Co content on the catalytic activity of CoSiBEA zeolites in N2O decomposition and SCR of NO with ammonia, Catal. Today 258 (2015) 507–517, https://doi.org/10.1016/j.cattod. 2014.12.001.