The Impact of Lanthanum and Zeolite Structure on Hydrocarbon Storage

catalysts

Article The Impact of Lanthanum and Zeolite Structure on Hydrocarbon Storage

Rasmus Jonsson, Phuoc Hoang Ho , Aiyong Wang , Magnus Skoglundh and Louise Olsson *

Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96 Göteborg, Sweden; [email protected] (R.J.); [email protected] (P.H.H.); [email protected] (A.W.); [email protected] (M.S.) * Correspondence: [email protected]; Tel.: +46-31-772-4390

Abstract: Hydrocarbon traps can be used to bridge the temperature gap from the cold start of a vehicle until the exhaust after-treatment catalyst has reached its operating temperature. In this work, we investigate the effect of zeolite structure (ZSM-5, BEA, SSZ-13) and the effect of La addition to H-BEA and H-ZSM-5 on the hydrocarbon storage capacity by temperature-programmed desorption and DRIFT spectroscopy. The results show that the presence of La has a significant effect on the adsorption characteristics of toluene on the BEA-supported La materials. A low loading of La onto zeolite BEA (2% La-BEA) improves not only the toluene adsorption capacity but also the retention of toluene. However, a higher loading of La results in a decrease in the adsorbed amount of toluene, which likely is due to partial blocking of the pore of the support. High loadings of La in BEA result in a contraction of the unit cell of the zeolite as evidenced by XRD. A synergetic effect of having simultaneously different types of hydrocarbons (toluene, propene, and propane) in the feed is found for samples containing ZSM-5, where the desorption temperature of propane increases, and the quantity that desorbed increases by a factor of four. This is found to be due to the interaction between Citation: Jonsson, R.; Ho, P.H.; Wang, toluene and propane inside the structure of the zeolite. A.; Skoglundh, M.; Olsson, L. The Impact of Lanthanum and Zeolite Keywords: HC trap; cold start; toluene; gasoline; zeolite; lanthanum; La-BEA Structure on Hydrocarbon Storage. Catalysts 2021, 11, 635. https:// doi.org/10.3390/catal11050635 1. Introduction Academic Editors: Maria Casapu and Efficient exhaust after-treatment is vital to reduce the emissions of harmful bi-products Dmitry E. Doronkin from combustion engines, such as nitrogen oxides (NOx), carbon monoxide, unburnt hydrocarbons (HC), and particulates. Modern catalytic converters are efficient in removing Received: 31 March 2021 these species when operated within the designated temperature range. However, during Accepted: 12 May 2021 Published: 15 May 2021 the warm-up period after a cold-start of the engine, the efficiency of catalytic converters is sharply reduced. Therefore, different trapping materials can be used to delay the unwanted

Publisher’s Note: MDPI stays neutral bi-products until the converter has reached operating temperature, i.e., above the so-called with regard to jurisdictional claims in light-off temperature. NOx-adsorbers and HC traps are in this connection interesting published maps and institutional afﬁl- techniques [1–4] since 80–90% of all pollutants from vehicles are released during cold iations. starts [3]. The light-off temperature occurs around 300–350 ◦C for a three-way catalyst (TWC) [5]. Ideally, an HC trap should release the adsorbed hydrocarbons in the light-off temperature range. However, HC traps usually release hydrocarbons around 200–250 ◦C[5]. Closing this temperature gap is urgent and calls for more research in the ﬁeld of HC traps. Develop- Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ment of effective adsorbents in terms of high uptake of HC at low temperature, compatible This article is an open access article desorption temperatures with the active temperature window for the TWC, and high distributed under the terms and resistance to hydrothermal aging is crucial [6]. In this regard, zeolites have been widely conditions of the Creative Commons used for the development of HC traps [5,7]. The temperature range for the desorption Attribution (CC BY) license (https:// of HC from the trapping material depends on the interaction between the hydrocarbons creativecommons.org/licenses/by/ and the zeolite. The characteristics that are highly relevant for this interaction are the pore 4.0/). and channel sizes of the zeolite and its acidity (Brønsted and Lewis acidity) [8–12]. Pore

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and channel sizes are dependent on the zeolite type, whereas acidity is strongly regulated by the Si/Al- ratio that affects the Brønsted acidity or by the presence of ion-exchanged cations that induce Lewis acidity [5,8–12]. Toluene is a common HC component in gasoline, however, measurements of the distribution of HC components during cold-start emissions indicate that ethene is the most redundant one, while toluene is the largest component if calculated based on carbon atoms [13]. For this reason, propene (which has properties similar to ethene) and toluene are commonly used to study HC traps [14–16]. These two components interact differently with the zeolite framework. Propene is suggested to adsorb on the OH groups of the Brønsted acid sites by forming hydrogen bonds via the π- electrons in the C=C bond of the propene molecule [17]. Since Brønsted acidity is governed by low Si/Al-ratio, the trapping of propene is enhanced by low Si/Al-ratio. Toluene has been proposed to interact with both Lewis acid sites and Brønsted acid sites [9,18]. Lewis acid sites, such as the negatively charged oxygens in the zeolite framework, have been proposed to interact with the methyl group of the toluene molecule [18,19]. Brønsted acid sites, in contrast, have been proposed to interact with the phenyl ring in toluene [11,18–22]. Lowering the Si/Al-ratio leads to an increased number of Brønsted acid sites, which enhances the adsorption of propene and ethylene in the porous structure of the zeolite. However, this also increases the adsorption of water since the zeolite becomes more hydrophilic. Studies have shown that water competes with smaller HCs for Brønsted acid sites. This is due to the strong interaction between Brønsted acid sites and water, and therefore, water inhibits HC adsorption [23,24]. Ivanov and co-workers have reported that the SiO2/Al2O3-ratio of ZSM-5 does not significantly influence the adsorption of small alkanes (e.g., propane and butane) in the presence of moisture [25]. Increasing the Si/Al-ratio, in contrast to decreasing it, governs the adsorption of toluene in the zeolite. Burke et al. [26] have studied thermal aging of La-BEA and measured the adsorption of toluene and propene using temperature-programmed desorption (TPD). They found a reduction in the adsorption capacity of propene onto La-BEA caused by the dealumination during thermal aging [26]. These findings indicate a connection between the Si/Al-ratio and the Brønsted acidity, which subsequently affects the adsorption patterns in the porous structure of the zeolite. Zeolites are often ion-exchanged with cations in order to increase the Lewis acidity in HC traps. Ag+ has proven to be an efficient addition to HC traps. The positive effects of the silver ion have been attributed to its size and water resistance [5,24,27,28]. The size of an ion-exchanged cation is of major importance for larger molecules to adsorb. For this reason, there have been several studies on Na+ in which it acts as a Lewis acid when ion-exchanged in the zeolite [29]. A commonly studied metal for HC storage is Pd [28,30–32]. Lupescu et al. have found that Pd together with Brønsted acid sites promote polymerization of stored HC compounds in the zeolite when gasoline is direct-injected into the exhaust after-treatment system of a Ford Focus passenger car [31]. We have recently studied the effect of impregnating H-BEA with Fe, La, and Pd on the HC-trapping ability of the sample formation [33]. We found that incorporation of La contributed to the adsorption of toluene in zeolite BEA and increased binding strength of the hydrocarbon. However, to our knowledge, no studies have examined the effect of lanthanum loading and the effect of incorporating La into different zeolite structures, which is the objective of the present study. Therefore, we investigate the effect of zeolite structure—ZSM-5 (MFI), Beta (BEA) and SSZ-13 (CHA)—and the effect of La addition to H-BEA and H-ZSM-5 on the storage capacity of toluene, propene, and propane by temperature-programmed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Catalysts 2021, 11, 635 3 of 21

2. Results and Discussion 2.1. Catalyst Characterization

The catalysts were characterized using N2 physisorption, Inductively coupled plasma, sector ﬁeld mass spectrometry (ICP-SFMS), and X-ray diffraction (XRD). The elemental compositions, speciﬁc surface area, and total pore volume of the samples are summarized in Table1.

Table 1. Compositions and textural properties of the catalyst samples.

BEA 2% La-BEA 6% La-BEA 9% La-BEA 2% La-ZSM-5 ZSM-5 SSZ-13 a SiO2/Al2O3 20.2 20.6 21.0 21.4 20.5 20.2 25.2 La wt.% a - 2.2 6.4 8.6 2.0 - - La/Al a - 0.14 0.43 0.62 0.12 - - 2 −1 SBET (m g ) 569 467 433 420 330 356 638 2 −1 b Smicropore (m g ) 354 327 305 294 253 273 598 3 −1 c Vp (cm g ) 0.65 0.59 0.53 0.52 0.17 0.18 0.34 3 −1 b Vmicropore (cm g ) 0.17 0.16 0.15 0.14 0.12 0.13 0.29 a b Elemental compositions were analyzed with ICP-SFMS; speciﬁc surface area and speciﬁc micropore volume (Smicropore and Vmicropore) c were determined with the t-plot method; total pore volume Vp was calculated at p/po = 0.97.

The N2 physisorption isotherms for H-SSZ-13 and H-ZSM-5 are close to type I, and the N2 physisorption isotherm for H-BEA is similar to type IV (IUPAC classification of adsorption isotherms) [34]. The isotherms for all three samples reveal the presence of microporosity with enhanced N2 uptake at very low relative pressure ranges (Figure A3 in AppendixA). A small hysteresis between the adsorption and desorption isotherms was observed for both H-ZSM-5 and HSSZ-13, indicating a minor contribution of inter-crystal mesoporosity. The hysteresis was more pronounced for H-BEA. Thus, H-BEA has a lower ratio of micropore volume per total pore volume than H-ZSM-5 and H-SSZ-13 (Table1). The impregnation with La leads to a decrease of the specific surface area for the BEA and ZSM-5 samples, in line with previous studies [25]. To observe the crystalline state of the samples, X-ray diffraction was used for H-BEA, 2% La-BEA, 2% La-BEA loaded with toluene, 6% La-BEA, 9% La-BEA, H-SSZ-13, and H-ZSM-5 samples. The XRD results are shown in Figure1. All five BEA samples show the characteristic diffractogram for zeolite BEA [35]. The diffractograms for the ZSM-5 and SSZ-13 samples agree well with reported XRD patterns [36,37]. The samples containing zeolite BEA are compared in Figure1B. The reflection intensity for the La-doped samples is lower than that for the parent BEA zeolite. This can be due to either a partial collapse of the framework [38] or enhanced X-ray absorption in the presence of La [39]. Moreover, the reflection of 2θ = 22.5◦ is slightly shifted to higher angles for all La-BEA samples. This reveals that the unit cell of the zeolite is contracted with the incorporation of La. Such contraction of the unit cell has previously been observed for zeolites modified with rare-earth elements [38]. However, the shift is not significantly different for the La- BEA samples with increasing La loadings from 2 to 9% (Figure A1). This suggests that only a certain amount of La can be incorporated in the zeolite, and therefore a further increase of La loading does not contract the unit cell further. Note that although no segregation phase of La2O3 has been identified, the oxidation state of 3+ has been reported for La cations in La-doped zeolites [40]. Figure1C shows the enlargement of the X-ray diffraction pattern for the 2% La- BEA sample saturated with toluene at 80 ◦C. In contrast to the modification with La, the adsorption of toluene leads to a shift of the main reflection to a lower reflection angle (2θ), indicating an expansion of the unit cell of the zeolite structure due to the confinement of toluene in the pores of the beta zeolite. Expansion of the unit cell of the host zeolite during the adsorption of guest molecules has previously been reported [41–43]. Catalysts 2021, 11, 635 4 of 22

toluene in the pores of the beta zeolite. Expansion of the unit cell of the host zeolite during the adsorption of guest molecules has previously been reported [41–43]. Figure 1D compares the XRD patterns for the ZSM-5 and 2.5% La-ZSM-5 samples. The incorporation of La into ZSM-5 results in a similar characteristic to the La-BEA samples. The intensity of the diffraction peaks for La-ZSM-5 is slightly lower than that for pristine ZSM-5. Moreover, the diffraction peaks for the 2.5% La-ZSM-5 sample are also Catalysts 2021, 11, 635 4 of 21 slightly shifted to higher diffraction angles than those for ZSM-5 due to contraction of the unit cell (Figure A2).

Figure 1. XRD patterns from H-BEA, 2% La-BEA, 6% La-BEA, 9% La-BEA,La-BEA, SSZ-13, ZSM-5, and 2% La-BEA loaded with toluene. Panel ((AA)) seriesseries ofof BEA BEA and and HSSZ-13 HSSZ-13 samples. samples. Panel Panel (B )(B enlargement) enlargement of theof the diffraction diffraction patterns patterns for thefor zeolitethe zeolite BEA BEAsamples. samples. Panel Panel (C) comparison (C) comparison of the of main the main reﬂection reflection of the of patterns the patter ofns the of 2%the La-BEA 2% La-BEA and toluene-loadedand toluene-loaded 2% La-BEA2% La- BEAsamples. samples. Panel Panel (D) ZSM-5 (D) ZSM-5 and 2%and La-ZSM-5 2% La-ZSM-5 samples. samples.

FigureFigure 12D presents compares the the NH XRD3-TPD patterns profiles for the for ZSM-5 different and 2.5%adsorbents. La-ZSM-5 Detailed samples. infor- The mationincorporation on the ofdeconvolutions La into ZSM-5 of results the profile in a similarcan be characteristicfound in Figures to the A4 La-BEA and A5 samples.and the amountThe intensity of desorbed of the diffractionNH3 and peak peaks desorption for La-ZSM-5 temperatures is slightly are lower summarized than that forin Table pristine 2. TheZSM-5. desorption Moreover, profiles the diffractionfor the parent peaks H- forBEA the and 2.5% H-ZSM-5 La-ZSM-5 samples sample show are two also overlap- slightly pingshifted peaks to higher at approximately diffraction angles 210–220 than °C those (low-temperature for ZSM-5 due todesorption contraction peak, of the LTP) unit and cell 420–450(Figure A2°C). (high-temperature desorption peak, HTP), corresponding to weak and strong acid sites,Figure respectively2 presents the [44]. NH The3-TPD NH profiles3-TPD profile for different for H-SSZ-13 adsorbents. shows Detailed the LTP information at 195 °C andon the the deconvolutions HTP at 458 °C. The of the amount profile of can acid be sites found is approximately in Figures A4 and599, A5755, and and the 1289 amount µmol NHof desorbed3/g for H-SSZ-13, NH3 and H-BEA, peak desorption and H-ZSM-5, temperatures respectively. are summarized Both the peak in temperature Table2. The des-and theorption total profilesnumber for of theacid parent sites for H-BEA these and parent H-ZSM-5 zeolites samples are similar show to two those overlapping reported in peaks the ◦ ◦ literatureat approximately [45–47]. Impregnation 210–220 C (low-temperature of La leads to a decrease desorption in the peak, intensity LTP) of and both420–450 LTP andC (high-temperature desorption peak, HTP), corresponding to weak and strong acid sites, ◦ respectively [44]. The NH3-TPD profile for H-SSZ-13 shows the LTP at 195 C and the ◦ HTP at 458 C. The amount of acid sites is approximately 599, 755, and 1289 µmol NH3/g for H-SSZ-13, H-BEA, and H-ZSM-5, respectively. Both the peak temperature and the total number of acid sites for these parent zeolites are similar to those reported in the literature [45–47]. Impregnation of La leads to a decrease in the intensity of both LTP and HTP for 2%La-ZSM-5 and 2%La-BEA, indicating a decrease in the total number of acid sites (Figure2). As a result, both 2% La-BEA and 2%La-ZSM-5 show lower total acidity Catalysts 2021, 11, 635 5 of 22

Catalysts 2021, 11, 635 5 of 21 HTP for 2%La-ZSM-5 and 2%La-BEA, indicating a decrease in the total number of acid sites (Figure 2). As a result, both 2% La-BEA and 2%La-ZSM-5 show lower total acidity thanthan the the respective respective parent parent zeolite zeolite (Table (Table 2).2 ).For For the the La-BEA La-BEA samples, samples, a further a further increase increase in Lain loading La loading also also leads leads to a to decrease a decrease in intotal total acidity. acidity. Deng Deng et etal. al. have have reported reported a asimilar similar trendtrend for for the the incorporation incorporation of of La La into into zeolite zeolite Y Y [40]. [40]. Our Our NH NH3-TPD3-TPD data data do do not not allow allow us us to to discussdiscuss more more the the distribution distribution of of Brønsted Brønsted and and Le Lewiswis acid acid sites. sites. However, However, Ivanov Ivanov et et al. al. [25] [25 ] foundfound that that the the addition addition of of 5% 5% La La into into H-ZSM- H-ZSM-55 resulted resulted in in a adecrease decrease in in the the number number of of BrønstedBrønsted and and Lewis Lewis acid acid sites sites but but also also in in the the formation formation of of new new sites sites related related to to La, La, e.g., e.g., + + LaO(OH)LaO(OH) and and La(OH) La(OH)2 2. .

1000 2500 B 700 A o 700 210 C o 450 C H-ZSM-5 800 o H-BEA 600 2000 220 C 2% La-ZSM-5 600 o 2% La-BEA 445 C H-SSZ-13 C) C) 6% La-BEA Temperature o o o o 420 C 500 219 C 500 600 360 oC 9% La-BEA 1500 Temperature 400 400 195 oC 400 1000 concentration (ppm) o ( Temperature concentration (ppm)

3 Temperature ( 300

3 300 458 C NH NH 200 500 200 200

0 100 0 100 340 360 380 400 420 340 360 380 400 420 Time (min) Time (min)

Figure 2. NH3-TPD profiles for (A) H-BEA, 2%La-BEA, 6%La-BEA and 9%La-BEA, and (B) H-ZSM-5, 2% La-ZSM-5 Figureand H-SSZ-13. 2. NH3-TPD profiles for (A) H-BEA, 2%La-BEA, 6%La-BEA and 9%La-BEA, and (B) H-ZSM-5, 2% La-ZSM-5 and H-SSZ-13. Table 2. Comparison of acidity for different samples from NH3-TPD measurements. Table 2. Comparison of acidity for different samples from NH3-TPD measurements. H-BEA 2% La-BEA 6% La-BEA 9% La-BEA 2% La-ZSM-5 H-ZSM-5 H-SSZ-13 H-BEA 2% La-BEA 6% La-BEA 9% La-BEA 2% La-ZSM-5 H-ZSM-5 H-SSZ-13 Total acidity (µmol NH3/g) 755 615 592 506 1093 1289 599 ◦ Low-temperatureTotal acidity peak(µmol (LTP) NH ( 3/g)C) 213755 211615 211592 210506 2191093 1289 220 599 195 ◦ High-temperatureLow-temperature peak peak (HTP) (LTP) ( C) (°C) 420 213 380 211 370 211 348 210 445 219 450 220 195 458 Percentage of LTP area (%) * 21 19 20 22 43 43 31 High-temperaturePercentage of HTP peak area (%)(HTP) * (°C) 79 420 81 380 80 370 78 348 57 445 45057 458 69 Percentage of LTP area (%) * 21 19 20 22 43 43 31 * Detailed information on the deconvolution of the peaks can be found in Figures A4 and A5. Percentage of HTP area (%) * 79 81 80 78 57 57 69 * Detailed information on the deconvolution of the peaks can be found in Figures A4 and A5. 2.2. HC Storage for La-Promoted Zeolites 2.2. HCThe Storage goal offor an La-Promoted HC-trapping Zeolites system is to delay the desorption of hydrocarbons released during the warm-up period after a cold-start of the engine in order to oxidize them until the The goal of an HC-trapping system is to delay the desorption of hydrocarbons re- catalytic converter reaches the light-off temperature. One efficient method to measure this leased during the warm-up period after a cold-start of the engine in order to oxidize them is temperature-programmed desorption of hydrocarbons. This study focuses on lanthanum until the catalytic converter reaches the light-off temperature. One efficient method to supported on conventional zeolites, such as H-BEA and H-ZSM-5. However, since La is a measure this is temperature-programmed desorption of hydrocarbons. This study focuses quite large atom, 3.9 Å in diameter, and the diameter of the eight-membered ring of SSZ-13 on lanthanum supported on conventional zeolites, such as H-BEA and H-ZSM-5. How- is 3.7 Å in diameter, no attempt to impregnate SSZ-13 with La was made. Instead, SSZ-13 ever, since La is a quite large atom, 3.9 Å in diameter, and the diameter of the eight-mem- was investigated only in the hydrogen form. bered ring of SSZ-13 is 3.7 Å in diameter, no attempt to impregnate SSZ-13 with La was Four TPD experiments were performed for eight different samples, and three different made. Instead, SSZ-13 was investigated only in the hydrogen form. types of hydrocarbons were measured. Toluene was chosen since it is a common aromate Four TPD experiments were performed for eight different samples, and three differ- in the exhaust during the cold-start period. Further, one alkene and one alkane were used, enti.e., types propene of hydrocarbons and propane, were to examine measured. the differencesToluene was when chosen a double since bondit is a is common present. aro- Each mate in the exhaust during the cold-start period. Further, one alkene and one alkane were TPD experiment was performed in the presence of 5 vol.% H2O in the feed since water used,always i.e., is propene present inand real propane, applications to examine of HC trapping.the differences Before when each TPD,a double the samplesbond is pre- were sent. Each TPD experiment was performed◦ in the presence of 5 vol.% H◦ 2O in the feed since pre-oxidized in 10 vol.% O2 at 400 C for 20 min and cooled to 80 C in the presence of water always is present in real applications of HC trapping. Before each TPD, the samples H2O and O2. The HC exposure phase was 60 min, followed by flushing the sample in Ar werefor 20pre-oxidized min, and finally, in 10 vol.% a temperature O2 at 400 ramp°C for was 20 min performed and cooled at a rateto 80 of °C 20 in◦ Cthe min presence−1. The ofadsorption H2O and O of2. tolueneThe HC onto exposure the H-BEA phase zeolite was 60 framework min, followed has been by flushing shown inthe our sample previous in work to be uninhibited by water due to its low dependency on interaction with Brønsted

Catalysts 2021, 11, 635 6 of 22

Ar for 20 min, and finally, a temperature ramp was performed at a rate of 20 °C min−1. The adsorption of toluene onto the H-BEA zeolite framework has been shown in our previous work to be uninhibited by water due to its low dependency on interaction with Brønsted acid sites [33]. However, the trapping of propene is strongly affected by the presence of water. Figure 3A shows the desorption profiles for toluene in the presence of water (wet- toluene TPD) for four samples, i.e., H-BEA and H-BEA promoted with different amounts of La (2, 6, and 9%). Higher desorption quantities were observed for the pure H-BEA and 2% La-BEA samples than for the samples containing higher La loading (6 and 9%). Nota- bly, the 2% La-BEA sample had about a 7% higher storage capacity than the H-BEA sample, which is in line with our previous study [33]. Interestingly, the binding strength of toluene increased when 2% La was incorporated into BEA, resulting in a shift in the desorption maximum temperature of approximately 15 °C. However, when further increasing the amount of La, the adsorption/desorption capacity decreased, as can be seen for the 6% La-BEA and 9% La-BEA samples. It should be noted that of the examined three La loadings, 2% La gave the best results, however, to find an optimum La loading, more concentrations should be examined. Figure 3B shows the desorption profiles of toluene for the ZSM-5, SSZ-13, and 2% La- ZSM-5 samples. The profile for SSZ-13 is flat without any toluene desorption, indicating that toluene is not trapped by SSZ-13. This is likely due to the narrow pore size of the zeolite, which may hinder larger molecules, such as toluene, from entering the cages of Catalysts 2021, 11, 635 the zeolite. A lower toluene desorption amount was found for samples containing ZSM-56 of 21 compared to BEA samples. Again, the reason is suggested to be the smaller pore size of ZSM-5, which is a medium-pore-sized zeolite with 10-membered rings, compared with BEA, which is a large-pore-sized zeolite with 12-membered rings. However, one ad- acidvantage sites with [33]. H-ZSM-5 However, compared the trapping to H-BEA of propene is that isthe strongly binding affected strength by of thethe presencetoluene is ofhigher, water. resulting in a shift in the desorption maximum temperature from 150 to 175 °C for Figure3A shows the desorption proﬁles for toluene in the presence of water (wet- the H-ZSM-5 sample compared to the H-BEA sample. Our results for H-ZSM-5 are in good toluene TPD) for four samples, i.e., H-BEA and H-BEA promoted with different amounts agreement with the study by Serra et al. [48], in which the authors reported a maximum of La (2, 6, and 9%). Higher desorption quantities were observed for the pure H-BEA and temperature of 175 °C for the desorption of toluene for a sample of H-ZSM-5 with a 2% La-BEA samples than for the samples containing higher La loading (6 and 9%). Notably, SiO2/Al2O3-ratio of 20. Moreover, we observed that the toluene storage capacity decreased the 2% La-BEA sample had about a 7% higher storage capacity than the H-BEA sample, when the ZSM-5 sample was impregnated with La, which could be suggested to be due which is in line with our previous study [33]. Interestingly, the binding strength of toluene to the reduced free-pore volume (as shown in Table 1) resulting in fewer sites for toluene increased when 2% La was incorporated into BEA, resulting in a shift in the desorption adsorption. This would imply that at a certain loading of La in the zeolite BEA sample, maximum temperature of approximately 15 ◦C. However, when further increasing the the channels are also partially blocked, which results in a decrease of the pore volume for amount of La, the adsorption/desorption capacity decreased, as can be seen for the 6% the adsorption of toluene. A combined sample with a mixture of ZSM-5 and 2% La-BEA La-BEA and 9% La-BEA samples. It should be noted that of the examined three La loadings, was also studied and it gave larger desorption than the H-ZSM-5, but smaller amounts 2% La gave the best results, however, to ﬁnd an optimum La loading, more concentrations shouldthan the be 2% examined. La-BEA sample, which is expected.

1750 1750 B H-BEA A 1500 2% La-BEA 1500

1250 1250 6% La-BEA 1000 1000 H-ZSM-5 + 2% La-BEA 750 9% La-BEA 750 2% La-ZSM-5 Toluene (ppm)

Toluene (ppm) Toluene H-ZSM-5 500 500 H-SSZ-13

250 250

0 0 100 150 200 250 300 100 150 200 250 300 Temperature of Desorption (°C) Temperature of Desorption (°C) FigureFigure 3. 3.Wet-toluene Wet-toluene TPD TPD experiments experiments where where toluene toluene desorption desorption is is plotted plotted versus versus the the temperature temperature for for ( A(A)) H-BEA, H-BEA, 2% 2% La-BEA,La-BEA, 6% 6% La-BEA, La-BEA, and and 9% 9% La-BEA; La-BEA; and and for for (B (B) SSZ-13,) SSZ-13, ZSM-5, ZSM-5, 2% 2% La-BEA, La-BEA, and and ZSM-5 ZSM-5 + + 2% 2% La-BEA. La-BEA.

Figure3B shows the desorption profiles of toluene for the ZSM-5, SSZ-13, and 2% La-ZSM-5 samples. The profile for SSZ-13 is flat without any toluene desorption, indicating

that toluene is not trapped by SSZ-13. This is likely due to the narrow pore size of the zeolite, which may hinder larger molecules, such as toluene, from entering the cages of the zeolite. A lower toluene desorption amount was found for samples containing ZSM-5 compared to BEA samples. Again, the reason is suggested to be the smaller pore size of ZSM-5, which is a medium-pore-sized zeolite with 10-membered rings, compared with BEA, which is a large-pore-sized zeolite with 12-membered rings. However, one advantage with H-ZSM-5 compared to H-BEA is that the binding strength of the toluene is higher, resulting in a shift in the desorption maximum temperature from 150 to 175 ◦C for the H-ZSM-5 sample compared to the H-BEA sample. Our results for H-ZSM-5 are in good agreement with the study by Serra et al. [48], in which the authors reported a maximum temperature of 175 ◦C for the desorption of toluene for a sample of H-ZSM-5 with a SiO2/Al2O3-ratio of 20. Moreover, we observed that the toluene storage capacity decreased when the ZSM-5 sample was impregnated with La, which could be suggested to be due to the reduced free-pore volume (as shown in Table1) resulting in fewer sites for toluene adsorption. This would imply that at a certain loading of La in the zeolite BEA sample, the channels are also partially blocked, which results in a decrease of the pore volume for the adsorption of toluene. A combined sample with a mixture of ZSM-5 and 2% La-BEA was also studied and it gave larger desorption than the H-ZSM-5, but smaller amounts than the 2% La-BEA sample, which is expected. To summarize, low loadings of La for zeolite BEA have a positive effect on both the amount and the binding strength of toluene. However, a blocking effect was found for Catalysts 2021, 11, 635 7 of 22

Catalysts 2021, 11, 635 7 of 21

To summarize, low loadings of La for zeolite BEA have a positive effect on both the amount and the binding strength of toluene. However, a blocking effect was found for higherhigher loadingsloadings (for(for 6%6% La-BEALa-BEA andand 9%9% La-BEA),La-BEA), andand thethe additionaddition ofof LaLa hashas aa clearclear effecteffect onon thethe structurestructure ofof thesethese samples,samples,as asfound foundby byXRD XRD(Figure (Figure1 B).1B). FigureFigure4 4 shows shows the the desorption desorption proﬁles profiles of of propene propene during during wet-propene wet-propene TPD TPD for for the the eighteight samples.samples. NoteNote thatthat aa minorminor amountamount ofof propanepropane waswas alsoalso detecteddetected duringduring thethe desorp-desorp- tiontion ofof propenepropene forfor somesome samples,samples, whichwhich couldcould bebe duedue toto minorminor residuesresidues ofof propanepropane fromfrom thethe cyclingcycling experimentexperiment before.before. TheThe resultsresults showshow thethe onlyonlyminor minor formation formation of of propane. propane.In In contrastcontrast toto thethe correspondingcorresponding toluenetoluene TPDTPD experiment,experiment, thethe BEABEA zeolitezeolite samplesample exhibitedexhibited onlyonly aa smallsmall capacitycapacity forfor propenepropene adsorption.adsorption. ThisThis isis inin agreementagreement withwith previousprevious studiesstudies wherewhere BEABEA samplessamples werewere examinedexamined asas HCHC trapstraps forfor thethe adsorptionadsorption ofof smallsmall hydrocarbons, especiallyespecially duringduring wetwet conditionsconditions [[26,33].26,33]. TheThe samplessamples containingcontaining ZSM-5ZSM-5 appearedappeared to to havehave thethe highesthighest storagestorage capacitycapacity forfor propene.propene. Moreover,Moreover, thethe H-SSZ-13H-SSZ-13 samplesample hadhad aa higherhigher ◦ temperaturetemperature ofof desorption,desorption, wherewhere thethe desorptiondesorption maximummaximum waswas 137 137 °CC forfor thethe H-ZSM-5H-ZSM-5 ◦ samplesample and 168 168 °CC for for the the H-SSZ-13 H-SSZ-13 sample. sample. Interestingly, Interestingly, the the2% La-ZSM-5 2% La-ZSM-5 and the and com- the combinedbined samples samples of 2% of La-BEA 2% La-BEA and andH-ZSM-5 H-ZSM-5 performed performed better better than thanH-ZSM-5 H-ZSM-5 alone. alone. Fur- Furthermore,thermore, it appears it appears that that La Laalso also contributes contributes to tothe the adsorption adsorption of of propene, propene, resulting resulting in in a adoubled doubled amount amount of of propene propene desorbed desorbed when when 2% La waswas incorporatedincorporated intointo ZSM-5.ZSM-5. ThisThis could be related to the formation of new types of acid sites, LaO(OH) and La(OH) +. could be related to the formation of new types of acid sites, LaO(OH) and La(OH)22+.

90 90 A Dashed Propane B Dashed Propane 80 Solid Propene 80 Solid Propene 70 70 2% La-ZSM-5 H-ZSM-5 + 2% La-BEA 60 60 H-ZSM-5 50 50 H-SSZ-13 40 40 30 9% La-BEA 30 6% La-BEA Gas conc. (ppm) Gas conc. (ppm) Gas conc. H-BEA 20 2% La-BEA 20 10 10 0 0 100 150 200 250 300 350 100 150 200 250 300 350 Temperature of Desorption (°C) Temperature of Desorption (°C)

FigureFigure 4. 4.Wet-propene Wet-propene TPD TPD experiments experiments wherewhere propene propene and and propane propane desorption desorption areare plotted plotted versusversus thethe temperaturetemperature forfor (A(A)) H-BEA, H-BEA, 2% 2% La-BEA, La-BEA, 6% 6% La-BEA, La-BEA, and and 9% 9% La-BEA; La-BEA; and and ( B(B)) SSZ-13, SSZ-13, ZSM-5, ZSM-5, 2% 2% La-BEA, La-BEA, and and ZSM-5 ZSM-5 + + 2% 2% La-BEA. La-BEA.

TheThe desorptiondesorption profilesprofiles ofof propanepropane duringduring wet-propanewet-propane TPDTPD areare shownshown in FigureFigure5 5.. SimilarSimilar toto thethe propene-TPDpropene-TPD profiles,profiles, itit waswas foundfound thatthat samplessamples basedbased onon zeolitezeolite BEABEA showedshowed aa substantiallysubstantially lowerlower amountamount ofof propanepropane desorbeddesorbed thanthan thethe samplessamples withwith zeolitezeolite H-ZSM-5H-ZSM-5 andand H-SSZ-13.H-SSZ-13. ItIt waswas observedobserved thatthat thethe samplesample containingcontaining H-SSZ-13H-SSZ-13 adsorbedadsorbed significantlysignificantly more more propane propane than than the the other other samples samples and and in a quantityin a quantity similar similar to the to adsorbed the ad- propene.sorbed propene. The higher The propene higher propene and propane and propane storage capacitystorage capacity of zeolite of SSZ-13 zeoliteand SSZ-13 ZSM-5, and which have a smaller pore size than zeolite beta, is likely due to the fact that they hinder ZSM-5, which have a smaller pore size than zeolite beta, is likely due to the fact that they the small molecules from desorption compared to large pore beta. For ZSM-5 and the hinder the small molecules from desorption compared to large pore beta. For ZSM-5 and BEA-containing samples, the desorption of propene dominated during the propane TPD, the BEA-containing samples, the desorption of propene dominated during the propane and the profiles of propene desorption are indicated by the dashed lines in Figure5.A TPD, and the profiles of propene desorption are indicated by the dashed lines in Figure 5. dehydrogenation of propane to propene occurred in the H-SSZ-13 sample but not to the A dehydrogenation of propane to propene occurred in the H-SSZ-13 sample but not to the same extent as for the other samples, and propane release dominated (Figure4B). The same extent as for the other samples, and propane release dominated (Figure 4B). The conversion of propane into propene in the zeolite BEA and ZSM-5 samples is related to the conversion of propane into propene in the zeolite BEA and ZSM-5 samples is related to acidity of the materials. It has been proposed that the Lewis acid sites are beneficial for the the acidity of the materials. It has been proposed that the Lewis acid sites are beneficial dehydrogenation reaction while the Brønsted acid sites are responsible for the cracking for the dehydrogenation reaction while the Brønsted acid sites are responsible for the reaction of propane in zeolite beta [49]. Note that besides the dehydrogenation reaction, the cracking reaction of propane in zeolite beta [49]. Note that besides the dehydrogenation cracking of propane and the derived product (e.g., propene) could not be discarded. For example,reaction, thethe crackingcracking of of propene propane and and dodecane the derived in zeolite product BEA (e.g., during propene) TPD has could previously not be

Catalysts 2021, 11, 635 8 of 22

Catalysts 2021, 11, 635 8 of 21

discarded. For example, the cracking of propene and dodecane in zeolite BEA during TPD has previously been reported [32,50]. Westermann et al. [11] have suggested that this pro- cessbeen is reported associated [32 ,50with]. Westermann Brønsted acid et al.sites [11 ]for have zeolite suggested HY with that different this process Si/Al-ratios is associated for hydrocarbonwith Brønsted traps. acid sites for zeolite HY with different Si/Al-ratios for hydrocarbon traps.

40 40 Solid Propane Solid Propane A B H-SSZ-13 35 Dashed Propene 35 Dashed Propene 30 30 2% La-ZSM-5 25 25 H-ZSM-5 + 2% La-BEA H-ZSM-5 20 20 9% La-BEA 15 H-BEA 6% La-BEA 15 Gas conc. (ppm) conc. Gas 2% La-BEA Gas conc. (ppm) 10 10 5 5 0 0 100 150 200 250 300 350 100 150 200 250 300 350 Temperature of Desorption (°C) Temperature of Desorption (°C) FigureFigure 5. 5. Wet-propaneWet-propane TPD experiments wherewhere the the desorption desorption of of propene propene and and propane propane is is plotted plotted against against the the temperature temperature for for(A) ( H-BEA,A) H-BEA, 2% La-BEA,2% La-BEA, 6% La-BEA, 6% La-BEA, and 9%and La-BEA 9% La-BEA samples; samples; and (B and) SSZ-13, (B) SSZ-13, ZSM-5, ZSM-5, 2% La-BEA, 2% La-BEA, and ZSM-5 and + ZSM-5 2.5% La-BEA. + 2.5% La-BEA. Figure6 shows a combined wet-HC TPD experiment with toluene, propene, and propaneFigure for 6 allshows eight a samples.combined Panels wet-HC A andTPD B experiment show the desorption with toluene, of toluene, propene, and and Panels pro- paneC and for D all show eight the samples. desorption Panels of propene A and B and show propane, the desorption respectively. of toluene, It can be and observed Panels inC andFigure D 6showA,B thatthe thedesorption desorption of propene profiles andand quantitiespropane, respectively. of desorbed tolueneIt can be are observed preserved in Figurecompared 6A,B to that the the corresponding desorption profiles desorption and profiles quantities for theof desorbed single toluene toluene TPD are experiment preserved compared(see Figure to2 ).the Azambre corresponding et al. have desorption performed prof mixediles for HC the TPDssingle that toluene contained TPD experiment a mixture (seeof propene, Figure 2). toluene, Azambre and et al. decane have [performed19]. The authors mixed HC observed TPDs that competitive contained adsorption, a mixture ofwhere propene, over time,toluene, larger and molecules decane [19]. replaced The smallerauthors ones observed during competitive the exposure adsorption, phase due whereto a stronger over time, interaction larger molecules with the replaced zeolite framework. smaller ones This during may the be exposure one explanation phase due for tothe a stronger preservation interaction of the toluenewith the desorptionzeolite framework. profile found This may in the be presentone explanation study. Another for the preservationexplanation isof suggestedthe toluene to desorption be low competition profile found for storagein the present sites among study. tolueneAnother and expla- the nationother twois suggested HC components, to be low which competition would result for storage in a preserved sites among toluene toluene desorption and the profile. other two HCFigure components,6B,D shows which some would changes result in in the a samplespreserved containing toluene desorption ZSM-5. The profile. desorbed amountFigure of propene6B,D shows is higher some comparedchanges in to the that samples for propane. containing Interestingly, ZSM-5. The the desorbed presence amountof toluene of propene and propene is higher in the compared feed during to that the for exposure propane. phase Interestingly, resulted the ina presence significant of tolueneincrease and in adsorption propene in and the desorptionfeed during of the propane. exposure A possible phase resulted explanation in a significant for this can in- be creasethat propane in adsorption is hydrophobic, and desorption and with of thepropane. confinement A possible of toluene explanation in the zeolite for this structure, can be thatthe numberpropane ofis possiblehydrophobic, sites forand propane with the to conf interactinement with of increases. toluene in This the zeolite effect was structure, found theto benumber strongest of possible for the sites mixed for ZSM-5propane + to 2% in La-BEAteract with samples. increases. This This might effect be was related found to toselective be strongest adsorption for the capacity mixed ZSM-5 of each + material2% La-BEA in thesamples. mixture, This for might example, be related zeolite to BEA selec- is tivemore adsorption selective capacity towards of toluene each material adsorption in the while mixture, zeolite for ZSM-5 example, prefers zeolite to storeBEA is smaller more selectiveHC components. towards Bothtoluene propane adsorption and propene while desorbedzeolite ZSM-5 for the prefers H-SSZ-13 to store sample smaller in an evenHC components.distribution, Both although propane the quantityand propene was lowerdesorb thaned for for the the H-SSZ-13 corresponding sample propane in an even TPD distribution,and propene although TPD experiments. the quantity This was finding lower suggeststhan for thatthe corresponding propene and propane propane in TPD the andH-SSZ-13 propene sample TPD competeexperiments. for storage This finding sites, likely suggests due tothat steric propene hindrance and propane in the small in the pores. H- The results from the four HC TPD experiments shown in Figures3–6 have been SSZ-13 sample compete for storage sites, likely due to steric hindrance in the small pores. integrated and presented as bars in Figure7. H-BEA, 2% La-BEA, 6% La-BEA, and 9% La-BEA samples are shown in Panels A, C, and E, and the remaining samples are shown in Panels B, D, and F. The desorption of toluene was unaffected by the presence of propene and propane, which is clearly seen in the quantified desorption data (Figure7). As seen in Figure7A,B, the samples with BEA stored toluene better than ZSM-5, with an increase of about two times, and SSZ-13 was found to have a negligible storage ability. Figure7F shows that the desorption of propane was enhanced by the presence of toluene, especially for the samples containing ZSM-5. For example, propane desorption increased by as much as four times for the H-ZSM-5 sample when propene and toluene were included during

Catalysts 2021, 11, 635 9 of 21

the adsorption phase, which agrees well with the study by Czaplewski et al. [51]. Even though there was a decrease in propene adsorption/desorption for the complete HC mix for most of the samples (Figure7D), this is not sufﬁcient to explain the increase in the desorption of propane shown in Figure7F. Thus, it is clear that the presence of toluene results in enhanced total amount of HC trapped. Moreover, Westermann et al. [11] studied the effect of the presence of three components (propene, toluene, and decane) during HC TPD and compared the capacities of different zeolites in dry conditions. They found that Catalysts 2021, 11, 635 9 of 22 the adsorption capacity of toluene at saturation for zeolite BEA was around 0.2 mmol per gram catalyst, which agrees well with our results in Figure7A.

1750 1750 A H-BEA B 1500 2% La-BEA 1500

1250 6% La-BEA 1250

1000 1000 H-ZSM-5 + 2% La-BEA 750 9% La-BEA 750 2% La-ZSM-5 H-ZSM-5 Toluene (ppm) Toluene (ppm) Toluene 500 500 H-SSZ-13

250 250

0 0 100 150 200 250 300 100 150 200 250 300 Temperature of Desorption (°C) Temperature of Desorption (°C) 60 Dashed Propane 60 Dashed Propane C Solid Propene D 50 H-ZSM-5 Solid Propene 50 H-ZSM-5 + 2% La-BEA

40 40 2% La-ZSM-5

30 9% La-BEA 30 H-SSZ-13 20 6% La-BEA H-BEA 2% La-BEA 20 Gas conc. (ppm) Gas conc. (ppm) 10 10

0 100 150 200 250 300 350 0 100 150 200 250 300 350 Temperature of Desorption (°C) Temperature of Desorption (°C)

Figure 6. Combined HC TPD experiments where toluene ( A,,B),), and propene and propane ( C,D) desorption are plotted versus temperature for ( A,C) H-BEA, 2% La-BEA, 6% La-BEA, and 9% 9% La-BEA, La-BEA, and and for for ( (BB,,DD)) SSZ-13, SSZ-13, ZSM-5, ZSM-5, 2% 2% La-BEA, La-BEA, and ZSM-5 + 2% 2% La-BEA. La-BEA.

TheIn-situ results DRIFTS from was the four used HC to measureTPD experime the surfacents shown species in Figures during 3–6 toluene have TPD. been Priorinte- ◦ gratedto the and TPD presented experiment, as bars all samplesin Figure were7. H-BEA, pre-oxidized 2% La-BEA, at 400 6% La-BEA,C with 10and vol.% 9% La-BEA O2 for ◦ samples20 min andare shown cooled in to Panels 80 C inA, theC, and presence E, and ofthe O remaining2. This was samples followed are by shown a dry-toluene in Panels ◦ B,exposure D, and phaseF. The at desorption 80 C for 60 of min toluene and thenwas coolingunaffected to room by the temperature. presence of The propene reason and for propane,dry-toluene which exposure is clearly instead seen of in wet the was quantifi due toed the desorption ﬁndings indata the (F previousigure 7). study As seen where in Figurethe adsorption 7A,B, the of samples toluene with was unaffectedBEA stored by tolu waterene duringbetter than adsorption ZSM-5, and with desorption. an increase The of abouttoluene two exposure times, stepand wasSSZ-13 performed was found in the to samehave ﬂowa negligible reactor asstorage for the ability. HC-TPDs Figure shown 7F showsin Figures that3 –the6. Thereafter,desorption theof propane temperature was wasenhanced decreased, by the and presence coating of with toluene, the adsorbents especially forwas the scraped samples off containing from the monolith ZSM-5. For substrates example, and propane studied desorption by in-situ increased DRIFTS. by Two as much TPDs were performed in the DRIFTS cell. First, a toluene TPD was conducted, where the changes as four times for the H-ZSM-5 sample when propene and toluene were included during in surface species were measured at different temperatures, thereafter, the samples were the adsorption phase, which agrees well with the study by Czaplewski et al. [51]. Even oxidized in 10 vol.% O for 30 min at 400 ◦C in and then cooled to 80 ◦C in presence of O . though there was a decrease2 in propene adsorption/desorption for the complete HC mix2 for most of the samples (Figure 7D), this is not sufficient to explain the increase in the desorption of propane shown in Figure 7F. Thus, it is clear that the presence of toluene results in enhanced total amount of HC trapped. Moreover, Westermann et al. [11] studied the effect of the presence of three components (propene, toluene, and decane) during HC TPD and compared the capacities of different zeolites in dry conditions. They found that the adsorption capacity of toluene at saturation for zeolite BEA was around 0.2 mmol per gram catalyst, which agrees well with our results in Figure 7A.

Catalysts 2021, 11, 635 10 of 21

Catalysts 2021, 11, 635 10 of 22 After oxidation, a second TPD was performed, which was later subtracted from the ﬁrst one to remove background signals.

0.3 0.3 A Toluene-TPD B Toluene-TPD 3xHC-TPD 3xHC-TPD

0.2 0.2

0.1 0.1 Toluene desorption (mmol / g-cat) / (mmol desorption Toluene Toluene desorption (mmol / g-cat) / (mmol desorption Toluene

0.0 0.0 (6% La-BEA) (9% La-BEA) (H-BEA) (2% La-BEA) (H-SSZ-13) (H-ZSM-5) (2% La-ZSM-5) (H-ZSM-5) + (2% La-BEA) 0.008 0.008 Propen-TPD Propen-TPD D C Propane-TPD Propane-TPD 3xHC-TPD 3xHC-TPD 0.006 0.006

0.004 0.004

0.002 0.002 Propene desorption (mmol / g-cat) / (mmol desorption Propene Propene desorption (mmol / g-cat) / (mmol desorption Propene 0.000 0.000 (H-SSZ-13) (H-ZSM-5) (2% La-ZSM-5) (H-ZSM-5) + (H-BEA) (2% La-BEA) (6% La-BEA) (9% La-BEA) (2% La-BEA) 0.008 0.008 Propen-TPD F Propen-TPD E 0.007 Propane-TPD 0.007 Propane-TPD 3xHC-TPD 3xHC-TPD 0.006 0.006

0.005 0.005

0.004 0.004

0.003 0.003

0.002 0.002

0.001

0.001 g-cat) / (mmol desorption Propane Propane desorption (mmol / g-cat) / (mmol desorption Propane 0.000 0.000 (2% La-ZSM-5) (H-ZSM-5) + (2% La-BEA) (6% La-BEA) (9% La-BEA) (H-SSZ-13) (H-ZSM-5) (H-BEA) (2% La-BEA) Figure 7. IntegratedIntegrated results results from from Figures Figures 22–5–5 wherewhere eacheach barbar representsrepresents the desorbed quantity from each TPD experiment. Panels ( A,,B) are a quantificationquantification of desorbed toluene; panels ( C,,D) are a quantificationquantification of desorbed propene; and panels (E,F) are a quantificationquantification of desorbed propane.propane.

In-situThe results DRIFTS from was in-situ used DRIFTS to measure experiments the surface are species shown induring Figures toluene8 and9 TPD.. Five Prior peaks to thein the TPD high experiment, wavenumber all samples range are were strongly pre-oxidized associated at 400 with °C adsorbed with 10 vol.% toluene. O2 for The 20 three min −1 andbands cooled at 3090, to 80 3063, °C in and the 3030 presence cm ofare O assigned2. This was to followed the stretching by a dry-toluene vibrations of exposure the C-H phasebond ofat the80 °C phenyl-group for 60 min and while then the cooling two bands to room at 2925 temperature. and 2873 cmThe− 1reasonare assigned for dry-tolu- to the eneasymmetric exposure and instead symmetric of wet stretchingwas due to vibrations the findings of the in methylthe previous group, study respectively where the [52 ,ad-53]. sorptionAs the temperature of toluene was increased, unaffected negative by water peaks during started adsorption to grow due and to desorption,desorption. and The it tolu- was eneobserved exposure that step the negativewas performed peaks ofin samplesthe same with flow a reactor high La as loading for the increased HC-TPDs faster shown than in Figures 3–6. Thereafter, the temperature was decreased, and coating with the adsorbents was scraped off from the monolith substrates and studied by in-situ DRIFTS. Two TPDs were performed in the DRIFTS cell. First, a toluene TPD was conducted, where the

Catalysts 2021, 11, 635 11 of 21

those for the H-BEA and 2% La-BEA samples, meaning that toluene desorbed faster from the high-loaded BEA samples. A broad peak around 3600 cm−1 was observed in the spectra of all samples at 80 ◦C (Figures8A and9A), which possibly can be assigned to hydrogen bonds of adsorbed water [54] because the samples were exposed to air during the transfer from the ﬂow reactor to the DRIFTS cell. The adsorbed water desorbed from the samples when the temperature was increased, and as a result, this broad peak disappeared from the spectra at 150, 250, and 350 ◦C (Figure8C,E,G and Figure9C,E,G). There were four peaks at the end of the high wavenumber range, 3780, 3736, 3664, and 3616 cm−1. The band around 3780 cm−1 is attributed to the very high frequency (VHF) band, which has been reported for H-BEA and delaminated ZSM-5. The peaks at 3780 and 3664 cm−1 are generally assigned to AlOH groups, namely extraframework or partially hydrolyzed alumina species [55,56]. Catalysts 2021, 11, 635 The peak at 3736 cm−1 is attributed to terminal silanols while the peak at 3616 cm12 −of1 22is

assigned to Brønsted acid sites (Si-O-Al(O-H)-O-Si) of the zeolites [56–58].

80°C A 80°C B 3736 3780 1583 9% La-BEA 1497 1620 1180 1310 2873 1275 3063 3030 2925 9% La-BEA 3090 6% La-BEA 1602 6% La-BEA 2% La-BEA

2% La-BEA H-BEA Absorbance (a.u.) Absorbance (a.u.) Absorbance H-BEA

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 1 1 Wavenumber (cm‾ ) Wavenumber (cm‾ ) 150°C C 150°C D 3736 3780 1497

9% La-BEA 1583 1275 1604 1635 1180 2873 3063 3030 2923 3090 9% La-BEA 6% La-BEA 6% La-BEA 2% La-BEA

2% La-BEA Absorbance (a.u.) H-BEA Absorbance(a.u.)

H-BEA

2000 1800 1600 1400 1200 1000 4000 3800 3600 3400 3200 3000 2800 1 1 Wavenumber (cm‾ ) Wavenumber (cm‾ ) 250°C E 250°C F 3736 3780 1583 1497 1604 9% La-BEA 1635 1275 1180 2873 3063 3030 2923 9% La-BEA 3090 6% La-BEA 6% La-BEA 2% La-BEA

2% La-BEA Absorbance(a.u.)

Absorbance (a.u.) Absorbance H-BEA

H-BEA

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 1 1 Wavenumber (cm‾ ) Wavenumber (cm‾ ) 350°C G Figure 8. Cont. 350°C H 3736 3780 1583 1604 1497 2873 9% La-BEA 1640 1275 1180 3063 3030 2923 9% La-BEA 3090

6% La-BEA 6% La-BEA 2% La-BEA

2% La-BEA Absorbance (a.u.) Absorbance

Absorbance (a.u.) Absorbance H-BEA H-BEA

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 1 Wavenumber (cm‾1) Wavenumber (cm‾ ) Figure 8. DRIFTS spectra during dry-toluene TPD experiments for H-BEA, 2%La-BEA, 6%La-BEA, and 9%La-BEA. The DRIFT spectra were recorded isothermally at different temperatures in Ar: (A) and (B) 80°C, (C) and (D) 150°C, (E) and (F) 250 °C and (G) and (H) 350 °C.

Catalysts 2021, 11, 635 12 of 22

80°C A 80°C B 3736 3780 1583 9% La-BEA 1497 1620 1180 1310 2873 1275 3063 3030 2925 9% La-BEA 3090 6% La-BEA 1602 6% La-BEA 2% La-BEA

2% La-BEA H-BEA Absorbance (a.u.) Absorbance (a.u.) Absorbance H-BEA

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 1 1 Wavenumber (cm‾ ) Wavenumber (cm‾ ) 150°C C 150°C D 3736 3780 1497

9% La-BEA 1583 1275 1604 1635 1180 2873 3063 3030 2923 3090 9% La-BEA 6% La-BEA 6% La-BEA 2% La-BEA

2% La-BEA Absorbance (a.u.) H-BEA Absorbance(a.u.)

H-BEA

2% La-BEA Absorbance(a.u.)

Absorbance (a.u.) Absorbance H-BEA Catalysts 2021 11 , , 635 H-BEA 12 of 21

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 1 1 Wavenumber (cm‾ ) Wavenumber (cm‾ ) 350°C G 350°C H 3736 3780 1583 1604 1497 2873 9% La-BEA 1640 1275 1180 3063 3030 2923 9% La-BEA 3090

6% La-BEA 6% La-BEA 2% La-BEA

2% La-BEA Absorbance (a.u.) Absorbance

Absorbance (a.u.) Absorbance H-BEA H-BEA

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 1 Wavenumber (cm‾1) Wavenumber (cm‾ ) Figure 8. DRIFTS spectra during dry-toluene TPD experiments for H-BEA, 2%La-BEA, 6%La-BEA, and 9%La-BEA. The ◦ ◦ ◦ DRIFTCatalysts spectra 2021 ,were were11, 635 recorded recorded isothermally isothermally at at different different temp temperatureseratures in in Ar: Ar: (A) (A and,B) 80(B)C, 80°C, (C,D (C)) 150 andC, (D) (E ,150°C,F) 25013 of (E) 22C and

((F)G, H250) 350 °C ◦andC. (G) and (H) 350 °C.

80°C A 80°C B 3736 3664

3780

2% La-BEA 1583 1620 1497 1180 1275 2873 3063 3030 3090 2925 ZSM-5 +

2% La-BEA 2% La-BEA 1310

2% La-ZSM-5 ZSM-5 + 2% La-BEA

2% La-ZSM-5 Absorbance (a.u.) Absorbance Absorbance (a.u.) Absorbance ZSM-5 ZSM-5

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 Wavenumber (cm‾1) Wavenumber (cm‾1)

150°C 150°C C D

3736 2% La-BEA 3780 3664 1497 1583 3616 1275 1310 1604 1180 1620 2873 3063 3030 2925 3090

2% La-BEA ZSM-5 + 2% La-BEA ZSM-5 + 2% La-BEA

2% La-ZSM-5 2% La-ZSM-5 Absorbance (a.u.) Absorbance

Absorbance (a.u.) Absorbance ZSM-5 ZSM-5

2000 1800 1600 1400 1200 1000 4000 3800 3600 3400 3200 3000 2800 1 Wavenumber (cm‾1) Wavenumber (cm‾ )

250°C E 250°C F 3736 3664 3780 3616 1275 1310 1180 1497 1583

2873 2% La-BEA 1604 1620 3063 3030 2925 3090

2% La-BEA ZSM-5 + 2% La-BEA

ZSM-5 + 2% La-BEA 2% La-ZSM-5

Absorbance (a.u.) Absorbance 2% La-ZSM-5 Absorbance (a.u.) Absorbance ZSM-5 ZSM-5

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 Wavenumber (cm‾1) 1 Wavenumber (cm‾ ) Figure 9. Cont.

Catalysts 2021, 11, 635 13 of 21 Catalysts 2021, 11, 635 14 of 22

350°C G 350°C

3736 H 3664 3780 3616 2873 1275 1310 1180 1583 1497 3063 3030 3090 2925 2% La-BEA 1604 1620 ZSM-5 + 2% La-BEA 2% La-BEA

ZSM-5 + 2% La-BEA 2% La-ZSM-5

Absorbance (a.u.) Absorbance 2% La-ZSM-5

Absorbance (a.u.) Absorbance ZSM-5 ZSM-5

4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 1 Wavenumber (cm‾ ) Wavenumber (cm‾1)

Figure 9.FigureDRIFTS 9. DRIFTS spectra spectra during during dry-toluene dry-toluene TPD TPD experiments experiments for for H-ZSM-5, H-ZSM-5, 2%La-ZSM-5, 2%La-ZSM-5, 2%La-BEA, 2%La-BEA, and a mixture and a of mixture of 2%La-ZSM-52%La-ZSM-5 and 2%-BEA. and 2%-BEA. The DRIFTThe DRIFT spectra spectra were were recordedrecorded isothermally isothermally at different at different temperatures temperatures in Ar: (A in) and Ar: ( (BA) ,B) 80◦C, 80°C, (C) and (D) 150°C, (E) and (F) 250 °C and (G) and (H) 350 °C. (C,D) 150◦C, (E,F) 250 ◦C and (G,H) 350 ◦C. 3. Materials and Methods −1 3.1.Three Sample peaks Preparation at 1602, 1497, and 1275 cm in the low wavenumber region are strongly associated with toluene. The peaks 1602 and 1497 cm−1 are assigned to the in-plane skeletal Three different zeolites were used in the present study: ZSM-5 (CBV2314, theoretical vibration of the phenyl group, and the peak at 1275 cm−1 is assigned to the symmetric SiO2/Al2O3-molar ratio of 23, NH4+-form), BEA (CP814E, theoretical SiO2/Al2O3 -molar ra- −1 vibrationstio of 25, of NH C-C4+-form), [54,59 and,60]. SSZ-13 Peaks (theoretical at 1602 and SiO 14972/Al2O cm3 -molarcould ratio be of observed25, H+-form). for Ze- all samples − witholite the ZSM-5 ability and to adsorbBEA were toluene. purchased A peakfrom atZeolyst 1275 International cm 1 was found(Conshohocken, for samples Penn- containing BEA.sylvania, The samples United States), containing and SSZ-13 ZSM-5 was did synthesized not have using a peak a procedure similar to reported the peak in our for the BEA samplesprevious in thiswork region [61]. All but supports at a higher in a form wavenumber. of fine powder Itwere is reasonablecalcined at 550 to °C assume for 2 h that this + + peak,to locatedtransform at from 1310 NH cm4 -− to1, H is-form. also related Four samples to the with symmetric different vibrationsweight loadings of C-C. of La, The peaks namely 2.5% La-ZSM-5, 2% La-BEA,−1 6% La-BEA, and 9% La-BEA were prepared using occurringincipient around wetness 1620–1640 impregnation. cm A solutionare assumed containing to a be given associated amount of with the theprecursor desorption of waterLa(NO on the3)3 .7H surface2O was of thoroughly the zeolite mixed [52,54 with]. Samples the support containing material. The La ormixture ZSM-5 was showed then a dual −1 peakdried at around at 120 °C 1583 for 24 cm h followed. In a comparison by calcination of at toluene-TPD550 °C for 2 h with for H-ZSM-5a heating rate and of Ag-ZSM-5,5 Liu°C et al.min observed−1. One sample a peak consisted in this of a region physical due mixture to the of incorporationthe 2% La-BEA sample of silver and ions the into the poresH-ZSM-5 of ZSM-5, zeolite which in an was equal assigned weight ratio. to Ag Zeolite+-phenyl H-SSZ-13 [24]. was This used extra without peak La was doping. also observed in our previousThe powder study, samples where were a then similar coated experiment onto honeycomb-shaped was conducted cordierite with monolith various HC-trap substrates (400 cpsi, diameter of 21 mm and length of 20 mm) using a dip-coating proce- materials (La-BEA included) [33]. dure with Boehmite (Sasol Dispersal P2, Sandton, South Africa) as a binder. Detailed in- formationFigure A6 on shows the coating that procedure no characteristic can be found toluene-related elsewhere [33]. peaks are visible for the H-SSZ- 13 sample at 80 ◦C. The result is consistent with the results for the TPD experiments shown in Figure3.2. Material3, with Characterization no adsorption/desorption of toluene for the H-SSZ-13 sample. This is related toThe the elemental small pore composition size for of H-SSZ-13, all materials which was measured sterically using hinders Inductively the adsorption Coupled of larger molecules.Plasma Sector Figure Field8B showsMass Spectrometry that toluene (ICP desorbed-SFMS), which from was the performed 6% La-BEA by ALS and Scan- 9% La-BEA samplesdinavia at AB. low temperatures, as indicated by the growth of the negative desorption peaks located atX-ray 1497 diffraction and 1275 measurements cm−1. These were results performed are consistent using a Siemens with D5000 the TPD diffractom- data (Figure3), eter (Siemens, Aubrey, TX, USA) operating at 40 kV and 40 mA. The diffractograms were in which the desorption of toluene was shifted towards higher temperatures for the 2% collected at 2θ-intervals of 10–80° with a 2θ-increase of 0.03° per second. La-BEAN sample2 physisorption compared measurements to the 6% were La-BEA perfor andmed 9% using La-BEA a TriStar samples. 3000 gas Inadsorption the high-loaded samples,analyzer La (Micromeritics, might block Norcross, the access GA, of USA). HC to Prior zeolite to each pores. measurement, Additionally, approximately La can provide + new0.1 acid g of sites powder such sample as LaO(OH) was degassed and at La(OH) 250 °C for2 , 16 improving h. The specific the surface interaction areas were with toluene. Thesecalculated factors from could the beBrunauer–Emmett–Teller reasons for the increased (BET) method toluene while adsorption the microporous capacity sur- of the 2% La-BEAface area sample. and micropore volume were determined using the t-plot method. The total pore volume was calculated at the relative pressure point of p/p0 = 0.97. 3. MaterialsNH3-TPD and measurements Methods were performed using a calorimeter (Sensys DSC, SETA- RAM instrument, Cranbury, NJ, USA). Powder samples were pelletized and sieved to 3.1. Sample Preparation Three different zeolites were used in the present study: ZSM-5 (CBV2314, theoretical + SiO2/Al2O3-molar ratio of 23, NH4 -form), BEA (CP814E, theoretical SiO2/Al2O3 -molar + + ratio of 25, NH4 -form), and SSZ-13 (theoretical SiO2/Al2O3 -molar ratio of 25, H -form). Zeolite ZSM-5 and BEA were purchased from Zeolyst International (Conshohocken, Penn- sylvania, United States), and SSZ-13 was synthesized using a procedure reported in our previous work [61]. All supports in a form of ﬁne powder were calcined at 550 ◦C for 2 h + + to transform from NH4 - to H -form. Four samples with different weight loadings of La, Catalysts 2021, 11, 635 14 of 21

namely 2.5% La-ZSM-5, 2% La-BEA, 6% La-BEA, and 9% La-BEA were prepared using incipient wetness impregnation. A solution containing a given amount of the precursor La(NO3)3.7H2O was thoroughly mixed with the support material. The mixture was then dried at 120 ◦C for 24 h followed by calcination at 550 ◦C for 2 h with a heating rate of 5 ◦C min−1. One sample consisted of a physical mixture of the 2% La-BEA sample and the H-ZSM-5 zeolite in an equal weight ratio. Zeolite H-SSZ-13 was used without La doping. The powder samples were then coated onto honeycomb-shaped cordierite monolith substrates (400 cpsi, diameter of 21 mm and length of 20 mm) using a dip-coating procedure with Boehmite (Sasol Dispersal P2, Sandton, South Africa) as a binder. Detailed information on the coating procedure can be found elsewhere [33].

3.2. Material Characterization The elemental composition of all materials was measured using Inductively Cou- pled Plasma Sector Field Mass Spectrometry (ICP-SFMS), which was performed by ALS Scandinavia AB. X-ray diffraction measurements were performed using a Siemens D5000 diffractometer (Siemens, Aubrey, TX, USA) operating at 40 kV and 40 mA. The diffractograms were collected at 2θ-intervals of 10–80◦ with a 2θ-increase of 0.03◦ per second. N2 physisorption measurements were performed using a TriStar 3000 gas adsorption analyzer (Micromeritics, Norcross, GA, USA). Prior to each measurement, approximately 0.1 g of powder sample was degassed at 250 ◦C for 16 h. The specific surface areas were calculated from the Brunauer–Emmett–Teller (BET) method while the microporous surface area and micropore volume were determined using the t-plot method. The total pore volume was calculated at the relative pressure point of p/p0 = 0.97. NH3-TPD measurements were performed using a calorimeter (Sensys DSC, SETARAM instrument, Cranbury, NJ, USA). Powder samples were pelletized and sieved to collect a fraction of particle sizes from 180 to 250 µm. Prior to each analysis, approximately 30 mg of material was pretreated at 300 ◦C for 30 min in Ar and then cooled to 100 ◦C. After that, −1 a flow of 20 mL min containing 2000 ppm NH3 balanced in Ar was introduced into the reactor for 90 min. This duration was sufficient to saturate the sample with NH3. The sample was then flushed with Ar for 60 min to remove physisorbed NH3. Temperature- programmed desorption measurements were performed by increasing the temperature from 100 to 700 ◦C (heating rate 10 ◦C min−1). The mass number, m/z = 17, was recorded to follow the desorption of NH3 using a mass spectrometer (HPR-20 QIC, Hidden analytical, Warrington, UK).

collect a fraction of particle sizes from 180 to 250 µm. Prior to each analysis, approximately 30 mg of material was pretreated at 300 °C for 30 min in Ar and then cooled to 100 °C. After that, a flow of 20 mL min−1 containing 2000 ppm NH3 balanced in Ar was introduced into the reactor for 90 min. This duration was sufficient to saturate the sample with NH3. The sample was then flushed with Ar for 60 min to remove physisorbed NH3. Tempera- ture-programmed desorption measurements were performed by increasing the temperature from 100 to 700 °C (heating rate 10 °C min−1). The mass number, m/z = 17, was recorded to follow the desorption of NH3 using a mass spectrometer (HPR-20 QIC, Hidden analytical, Warrington, UK).

3.3. Adsorption and Desorption of Hydrocarbons The coated monolith sample (diameter of 21 mm and length of 20 mm) was wrapped in a thin layer of quartz wool (less than 1 mm) and placed inside a quartz tube (22 mm in diameter and 750 mm in length). Two thermocouples were inserted into the monolith; one in the middle of the monolith to measure the temperature of the sample, and another measured the reactor temperature at approximately 20 mm in front of the monolith sample. The reactor was surrounded by a heating coil, which was subsequently covered with a layer of insulation. Dosage and volumetric flow of gases were controlled using mass flow controllers and a controlled evaporator mixing (CEM) system provided by Bronk- horst (Bethlehem, PA, USA). Gas compositions were analyzed using an MKS Multigas 2030 FTIR spectrometer (MKS Instruments, Andover, MA, USA). The adsorption and TPD experiments for each sample were performed in four sequential cycles including three cycles with a single gas component (toluene, propane, and Catalysts 2021, 11, 635 propene) and a mixture of those three gases. Each cycle includes an exposure step and a 15 of 21 subsequent desorption step. An overview of the tests is shown in Scheme 1. The sample was firstly degreened in 10 vol.% O2 and 5 vol.% H2O at 600 °C for 2 h and then cooled to 80 °C in 10 vol.% O2. The sample was then exposed to a gas flow of 1200 mL min−1 con- cycle. After that, the sample was flushed for 20 min in a flow of 600 mL min−1 containing taining 1000 ppm toluene and 5 vol.% H2O/Ar during the adsorption step of the first cycle. 5After vol.% that, H2 theO/Ar. sample The was desorption flushed for step 20 min was in performeda flow of 600by mL heating min−1 containing the sample 5 vol.% from 80 to ◦ ◦ −1 400H2O/Ar.C with The adesorption rate of 20 stepC was min performedin the sameby heating flow the as sample the flushing from 80 step. to 400 A °C low with flow rate ina rate the of desorption 20 °C min−1 stepin the was same selected flow as the to flushing facilitate step. the A analysislow flow rate of the in the hydrocarbons desorption with lowstep concentrations. was selected to facilitate the analysis of the hydrocarbons with low concentrations.

SchemeScheme 1. Overview 1. Overview of of experimental experimental design of of sequential sequential tests tests for for each each sample. sample. Note Notethat all that cycles all cycles(cycles (cycles1–4) were 1–4) were conducted in the presence of 5 vol% H2O. conducted in the presence of 5 vol% H2O. 3.4. In-situ DRIFTS (Diffuse Reflectance inFrared Fourier Transform Spectroscopy) 3.4. In-Situ DRIFTS (Diffuse Reflectance in Frared Fourier Transform Spectroscopy) To evaluate the interaction of toluene and the zeolite samples, DRIFTS measurements wereTo performed evaluate using the interaction a VERTEX of70 toluenespectrom andeter the(Bruker, zeolite Billerica, samples, MA, DRIFTS USA) equipped measurements werewith performeda liquid-nitrogen-cooled using a VERTEX mercury 70 spectrometercadmium telluride (Bruker, detector, Billerica, a Praying MA, Mantis USA) equippedTM withdiffuse a liquid-nitrogen-cooled reflectance accessory, and mercury a stainless-steel cadmium reaction telluride chamber detector, (Harrick a Praying Scientific Mantis TM diffuseProducts reflectance Inc., Pleasantville, accessory, NY, and USA). a stainless-steelSpectra were measured reaction between chamber 4000–500 (Harrick cm Scientific−1 Productswith a resolution Inc., Pleasantville, of 4 cm−1. The NY, second USA). fresh Spectra monolith were of each measured samplebetween was loaded 4000–500 in the cm−1 withflow areactor resolution and the of degreening 4 cm−1. The and secondexposure fresh step monolithof toluene ofwere each performed sample with was the loaded in thesame flow as reactorthe first andcycle thedescribed degreening in Section and 3.3 exposure but without step water. of toluene This selection were performed was to with simplify the experiment because it had been observed that water did not affect the ad- the same as the first cycle described in Section 3.3 but without water. This selection was to simplify the experiment because it had been observed that water did not affect the adsorption of toluene. After that, the powder of the washcoat was removed from the monolith and used for in-situ DRIFT experiments. The powder sample was loaded into

a cell and a ﬂow of Ar (100 mL min−1) was introduced. The temperature of the cell was initially set up at 80 ◦C and increased stepwise to 150, 200, 250, 300, and 350 ◦C. Data on the desorbed surface species were collected during the temperature steps. After that, ◦ the sample was oxidized at 400 C in 10 vol.% O2 for 20 min to remove any residual hydrocarbons, and subsequently, cooled to 80 ◦C in Ar. The second stepwise temperature increase was performed with the same procedure described for data collection so that the background at each respective temperature of the measurements (80, 150, 200, 250, 300, and 350 ◦C) was recorded.

4. Conclusions In the present work, we studied the effects of La and zeolite structure on hydrocarbon storage and desorption for HC traps. Adsorption and desorption of both single and multiple HC components were performed by the TPD experiments. The desorption characteristics of toluene during the desorption were also investigated using in-situ DRIFTS. The zeolites used were BEA, ZSM-5, and SSZ-13. The 2% La-BEA sample exhibited a 7% increase in toluene storage/release and 15 ◦C higher desorption temperature than the H-BEA zeolite. However, higher loadings of La (6 and 9%) resulted in a decrease in HC storage/release, as was found in the HC TPD experiments. This is suggested to be caused by the steric hindrance induced by La. Shifts in the XRD measurements conﬁrmed a large interaction between La and BEA. Zeolite SSZ-13 was unable to adsorb toluene due to the small pore size of the zeolite structure. In experiments with toluene, propene, and propane present at the same time in the storage step of HC TPD, it was found that propane desorbed from the ZSM-5 samples at a higher temperature and at higher concentrations (about four times higher) than propane alone (and H2O). This indicates that interactions occurred between the different HC components that increased propane storage and, at the same time, increased the binding strength of propane. The in situ DRIFTS measurements conﬁrmed that SSZ-13 did not trap toluene, as was found in the HC TPDs. In situ DRIFTS Catalysts 2021, 11, 635 16 of 21

data suggested that toluene was released faster for high La loading (6% La-BEA and 9% La-BEA) than for 2% La-BEA sample during the desorption process.

Author Contributions: Conceptualization, R.J., M.S., and L.O.; Data curation, R.J., P.H.H., and A.W.; Formal analysis, R.J., P.H.H., and A.W.; Methodology, R.J., M.S., and L.O.; Supervision, M.S. and L.O.; Writing—original draft, R.J.; Writing—review and editing, P.H.H., A.W., M.S. and L.O. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Competence Centre for Catalysis, which is hosted by Chalmers University of Technology and ﬁnancially supported by the Swedish Energy Agency, Chalmers and the member companies AB Volvo, ECAPS AB, Johnson Matthey AB, Preem AB, Scania Catalysts 2021, 11, 635 CV AB and Umicore Denmark ApS. 17 of 22

Acknowledgments: This work has been performed within the Competence Centre for Catalysis, which is hosted by Chalmers University of Technology and financially supported by the Swedish AppendixEnergy Agency, A Chalmers and the member companies AB Volvo, ECAPS AB, Johnson Matthey AB, Preem AB, Scania CV AB and Umicore Denmark ApS. Catalysts 2021, 11, 635 17 of 22 Conflicts of Interest: The authors declare no conflict of interest.

Appendix A Appendix A

FigureFigure A1. A1.X-ray X-ray diffractograms diffractograms of H-BEA andof H-BEA La-BEA with and different La-BEA loadings with different of La. loadings ofof La.La.

Intensity(a.u.) 2% La-ZSM-5

Intensity(a.u.) H-ZSM-52% La-ZSM-5

23 24 25 26 27 θ ( ) 2 Degree H-ZSM-5 Figure A2. Enlargement of the X-ray diffractograms for H-ZSM-5 and 2% La-ZSM-5. 23 24 25 26 27 θ ( ) 2 Degree Figure A2. Enlargement of the X-ray diffractograms for H-ZSM-5 and 2% La-ZSM-5.

Catalysts 20212021,, 1111,, 635635 1817 of of 2122 Catalysts 2021, 11, 635 18 of 22

250 A 250 B 400 A B

1 400 1

1 H-BEA 1

g‾ 200 g‾

3 H-BEA 3 g‾ 2% La-BEA 200 g‾ 3

2% La-BEA 3 300 6% La-BEA H-ZSM-5 300 6%9% La-BEALa-BEA H-ZSM-52% La-ZSM-5 9% La-BEA 150 2% La-ZSM-5 150 H-SSZ-13 H-SSZ-13 200 200 100 100 adsorbed amount / cm

100 adsorbed amount / cm 2 2 adsorbed amount / cm 50 100 adsorbed amount / cm N 2 N 2 50 N N

0 0 0 0.0 0.2 0.4 0.6 0.8 1.0 0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 Relative pressure / p/p o Relative pressure / p/po Relative pressure / p/po Relative pressure / p/p o Figure A3.A3. N22 adsorption-desorption isotherms isotherms for for ( A)) H-BEA H-BEA and and La-BEA with different La loading, and ( B) H-SSZ-13, Figure A3. N2 adsorption-desorption isotherms for (A) H-BEA and La-BEA with different La loading, and (B) H-SSZ-13, H-ZSM-5 and La-ZSM-5. H-ZSM-5 and La-ZSM-5.

Figure A4. Deconvolution of the NH3-TPD profiles for (A) H-BEA, (B) 2% La-BEA, (C) 6%La-BEA and (D) 9% La-BEA. Figure A4. Deconvolution of the NH 3-TPD-TPD profiles proﬁles for for ( (A)) H-BEA, H-BEA, ( (B)) 2% 2% La-BEA, La-BEA, ( C) 6%La-BEA and ( D) 9% La-BEA.

Catalysts 2021, 11, 635 18 of 21 Catalysts 2021, 11, 635 19 of 22 Catalysts 2021, 11, 635 19 of 22

Figure A5. Deconvolution of the the NH NH33-TPD-TPD profiles proﬁles for for (A (A) )H-ZSM-5, H-ZSM-5, (B (B) )2% 2% La-ZSM-5 La-ZSM-5 and and (C (C) )H- H- Figure A5. Deconvolution of the NH3-TPD profiles for (A) H-ZSM-5, (B) 2% La-ZSM-5 and (C) H- SSZ-13. SSZ-13.

A o B

3755 350 C 3800 3688 A o B

3755 350 C 1620 3800 3688 1180 1620 1180

250 oC 250 oC 1315 1315 350 oC 350 oC 150 oC 150 oC o

Absorbance (a.u.) 250 o C (a.u.) Absorbance

Absorbance (a.u.) 250 C (a.u.) Absorbance

150 oC 80 oC 150 oC 80 oC 80 oC 80 oC 4000 3800 3600 3400 3200 3000 2800 2000 1800 1600 1400 1200 1000 4000 3800 3600 3400 32001 3000 2800 2000 1800Wavenumber 1600 1400 (cm‾1) 1200 1000 Wavenumber (cm‾1 ) 1 Wavenumber (cm‾ ) Wavenumber (cm‾ ) Figure A6. DRIFTS spectra during dry-toluene TPD experiments for H-SSZ-13: (A) High wave number and (B) low wave Figure A6. DRIFTS spectra during dry-toluen dry-toluenee TPD experiments for H-SSZ-13: ( A)) High High wave wave number and ( B) low wave number. A stepwise measurement from 80–350 °C with only Ar present in the gas feed. number. A stepwise measurement from 80–350 ◦°CC with only Ar presentpresent in the gas feed. References References 1. Park, J.-H.; Park, S.J.; Nam, I.-S.; Yeo, G.K.; Kil, J.K.; Youn, Y.K. A fast and quantitative assay for developing zeolite-type hydro- 1. Park, J.-H.; Park, S.J.; Nam, I.-S.; Yeo, G.K.; Kil, J.K.; Youn, Y.K. A fast and quantitative assay for developing zeolite-type hydrocarbon trap catalyst. Microporous Mesoporous Mater. 2007, 101, 264–270, doi:10.1016/j.micromeso.2006.11.003. carbon trap catalyst. Microporous Mesoporous Mater. 2007, 101, 264–270, doi:10.1016/j.micromeso.2006.11.003.

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