# A Novel Process for the Preparation of Binder-Free Zeolite Beads (LTA-5A) via Photopolymerization Applied in CO2 Adsorption Field

Yijun Zhang, Ludovic Josien, Cyril Vaulot, Angélique Simon-Masseron, Jacques Lalevée

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Yijun Zhang, Ludovic Josien, Cyril Vaulot, Angélique Simon-Masseron, Jacques Lalevée. A Novel Process for the Preparation of Binder-Free Zeolite Beads (LTA-5A) via Photopolymerization Applied in CO2 Adsorption Field. 2023. [hal-04102584](https://hal.science/hal-04102584)

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# A Novel Process for the Preparation of Binder-Free Zeolite Beads (LTA-5A) via Photopolymerization Applied in CO₂ Adsorption Field

Yijun Zhang†,‡, Ludovic Josien†,‡, Cyril Vaulot†,‡, Angélique Simon-Masseron†,‡*, and
Jacques Lalevée†,‡*

† Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100 Mulhouse, France

‡ Université de Strasbourg, France

**Yijun Zhang**, Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100 Mulhouse, France; Université de Strasbourg, 67081 Strasbourg, France

**Ludovic Josien**, Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100 Mulhouse, France; Université de Strasbourg, 67081 Strasbourg, France

**Cyril Vaulot**, Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100 Mulhouse, France; Université de Strasbourg, 67081 Strasbourg, France

*Corresponding author:

**Angélique Simon-Masseron**, Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100 Mulhouse, France; Université de Strasbourg, 67081 Strasbourg, France. E-mail : angelique.simon-masseron@uha.fr

**Jacques Lalevée**, Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100 Mulhouse, France; Université de Strasbourg, 67081 Strasbourg, Franc. E-mail : jacques.lalevee@uha.fr

**Keywords:** Binder-free zeolite beads, High-speed mixing, Photopolymerization, Calcination, CO₂ adsorption.

## Abstract

The increasing CO₂ concentration in the atmosphere has a severe influence on both the environment and human health, resulting in global warming. According to the high adsorption capacity for CO₂ removal, zeolites play as an important role for CO₂ capture and sequestration. However, its powdery form limits their use in adsorption applications. When binding agents are used, the zeolite porosity is partially occluded which compromises the CO₂ adsorption capacity severely. How to prepare binder-free zeolite beads with a certain structure strength and how to keep the high surface area and porosity are a great challenge. In this work, LTA-5A beads composites (80 wt%) were prepared *via* cationic photopolymerization and then calcination was
performed to remove organic part to obtain LTA-5A beads with different sizes (< 1.0 mm, 1.0-2.0 mm and 2.0-3.0 mm). These beads (0.1 g) are characterized by good mechanical strength without any binder (partial bead fragmentation under 200 g-load) with a preserved zeolite porosity. This method allowed us to exploit the zeolite beads reaching a high specific surface area (586-688 m².g⁻¹) and good CO₂ adsorption capacity (4.5-4.9 mmol.g⁻¹). These values were higher than those of commercial LTA-5A beads (515 m².g⁻¹ and 3.8 mmol.g⁻¹ respectively), which is in agreement with their binder-free structure.

# 1. Introduction

During the past 150 years, the carbon dioxide (CO₂) concentration in the atmosphere has increased from 250 ppm to 418 ppm, which is mainly from anthropic activities, recognized one of the main causes of global warming problem.[1] Regulating the CO₂ emissions and capturing CO₂ from the environment are the main effective methods to ameliorate this problem. According on this purpose, different types of adsorbents have been developed, such as zeolite,[2, 3] activated carbons,[4, 5] metal-organic frameworks,[6-8] graphene oxide.[9-11]

As a class of microporous crystalline aluminosilicate materials, zeolites are widely used in gas adsorption or separation field, such as the sorption of CO₂ and H₂O, the separation of CO₂ from CO₂/CH₄/N₂ mixtures.[12, 13] They also are widely employed for the adsorption of toxic matters from water (metal ions, dyes, phenolic components).[14, 15] They consist of crystalline particles having size in the range of several nanometers to few micrometers, which is unsuitable for column filling and their use in continuous flow.[14] In order to be used as industrial adsorbents, zeolites in powder form need to be transformed into zeolitic objects (most common shape: beads and pellets) as a bulk material to avoid a high-pressure drop in cyclic adsorption processes.[16] The conventional ways to prepare zeolitic objects are to mix zeolite powder and inorganic binders together, such as e.g. kaolin,[17, 18] and to extrude pellets of desired sizes[19] or to mix powder and binder in a kneader-mixer where beads of different size are formed.[19] However, zeolitic objects normally have a binder content of approximately 20%, which decreases the adsorption capacity or catalytic performance of the material.[20] Hence, how to develop the synthesis of binder-free zeolite beads is an interesting researching area.[12, 21] In order to overcome this issue, many types of binder-free zeolite beads/pellets have been developed, and the binder is itself transformed into zeolite matter during hydrothermal conversion.[22] Compared to the conventional material containing binders, these binder-free zeolite beads or pellets have an increased adsorption capacity.[18, 23-25] At the same time, aluminosilicate beads also can be prepared by ion exchange of aluminosilicate species into ion exchange resins followed by combustion of the organic resin, which also can be seen as binder-
free beads.[26] In addition, the other method is to obtain structured objects with amorphous aluminosilicate extrudates through hydrothermal synthesis and calcination treatment.[27]

The use of organic binder is the other efficient approach to prepare zeolitic objects, which can help to avoid reducing the volumetric efficiency as inorganic binders causing clogging of microporous particle surface and therefore lower the mass transfer rate.[28] Normally, this way to prepare zeolitic objects is to mix zeolite powder and organic binder (polymer, such as chitosan,[16, 29] alginate,[30] methyl cellulose,[19] polyvinyl alcohol,[31] etc) homogenously to obtain formulations and to prepare 3D composite based on the cross-link between zeolite and organic part firstly. Then, depending on whether the presence of organic part affects the porosity of zeolite, the calcination step is considered or not to remove the organic part. By this method, zeolite characteristics can be well preserved for gas adsorption or removal of heavy metals from wastewater.[31-33] Luzzi et al reported their work about zeolite 13X/chitosan aerogel beads for CO₂ capture.[16] Their prepared beads composites containing 90 wt% 13X zeolite by the phase inversion process. These beads had a high specific surface area (561 m².g⁻¹) and good CO₂ capture (4.23 mmol.g⁻¹ at 1000 mbar). Isawi successfully prepared nanocomposite beads containing natural zeolite/polyvinyl alcohol/sodium alginate for removal of some heavy metals from wastewater.[31] The natural zeolite consists of 1% silicon oxide, 2.6% zeolite SSZ-73, 81.1% clinoptilolite and 15.3% donpeacorite. The beads were able to eliminate 60-99.8% of heavy ions from the natural wastewater samples collected from 10th Ramadan City, Cairo, Egypt, which contain Al³⁺, Fe³⁺, Cr³⁺, Co²⁺, Cd²⁺, Zn²⁺, Mn²⁺, Ni²⁺, Cu²⁺, Li²⁺, Sr²⁺, Si²⁺, V²⁺, and Pb²⁺.

However, during the preparation of zeolite beads or other shapes, organic binders, zeolite or any other co-binders should be mixed in different types of solvent (such as an acid/alkaline based solvent (acetic acid, NaOH),[16, 33, 34] salt based solvent (CaCl₂)[30, 33] or water together. Then, sample drying processes must be performed on these beads, including by freeze drying or by heating in oven.[16, 33] This indicates that the process of preparing these samples can be complex and time consuming. Hence, it is of significance to propose a simple and direct method for preparing binder-free zeolite beads.

One efficient way to implement this idea is the use of photopolymerization for zeolitic objects preparation, according on the unique advantages of photopolymerization, such as excellent spatial and temporal control, high production rate, mild reaction conditions (absence of organic solvents as volatile compounds (VOCs), and low-cost and safe irradiation source). In our previous work, we have successfully prepared LTA-5A zeolite based composites (zeolite content at 80-95 wt%) with polyethylene glycol diacrylate (PEGDA; Mw ~ 610 g.mol⁻¹) via
radical photopolymerization.[13] Then calcination (600 °C and 700 °C) was performed on these composites to prepare zeolitic objects. The calcinated zeolite materials kept porosity and have good CO₂ adsorption capacity. However, this work was carried out with the presence of solvent toluene to prepare zeolite composites, which is not environmentally friendly. Therefore, proposing a new way to elaborate zeolitic objects without solvent and binder after calcination is a very interesting challenge for zeolitic objects manufacturing.

In this study, we proposed a new approach to prepare zeolite beads for CO₂ adsorption application. Millimeter-sized composite beads with different diameters were obtained through high-speed mixing combined with epoxy cationic photopolymerization processes in a mild condition (room temperature, LED@405nm, and absence of solvent). After calcination treatment at 600 °C for 30 min, white beads were obtained. These beads properties were characterized in detail by different techniques: i) scanning electron microscope (SEM) was used to observe the surface of the calcinated beads and their core, ii) N₂ adsorption-desorption to determine the textural properties of beads and iii) CO₂ adsorption tests were performed to estimate the adsorption capacity of calcinated beads. In order to see the structure strength of calcinated beads, compression tests with different weights were also performed.

## 2. Results and Discussion

The sample preparation process is schematized in **Scheme 1** and the details are reported in Experimental Section. As shown in **Scheme 1.a**, two types of photopolymerization mechanism (i.e. free radical polymerization for acrylate and cationic polymerization for EPOX) are presented respectively. As shown in **Scheme 1.b**, during the high-speed mixing process, the liquid-powder two phases (monomer-zeolite powder) are in full contact to form lots of small beads quickly, which can grow into large beads layer-by-layer. Monomer acts as organic binder to bind zeolite powder layer by layer to form beads. After photopolymerization and calcination processes, the organic binder (polymer generated through polymerization) was removed and these beads retained the spherical shape. Compared to our previous works,[13, 35] the method in this work can successfully prepare composite beads without any solvent, which is more environmentally friendly, and then binder-free beads can be obtained directly after calcination process and used for CO₂ adsorption.
<figure><img src="image_2.png" /><figcaption>Cationic Polymerization</figcaption></figure>

<figure><img src="image_3.png" /><figcaption>b</figcaption></figure>

<figure><img src="image_4.png" /></figure>

**Scheme 1.** Schematic representation for (a) polymerization reactions and (b) zeolite beads preparation by high-speed mixing/photopolymerization/calcination steps.

**2.1 LTA-5A Beads Composite Preparation**

EPOX monomer was used as organic binder firstly to prepare bead composites with different mixing rate from 500 rpm to 2000 rpm. As shown in **Figure 1.a**, when the mixing rate was set at 500 rpm, few beads were obtained after 3 batches. As shown in **Figure 1.c**, when the mixing rate was increased to 1000 rpm, the number of beads increased after 3 batches (1st, 2nd and 3rd). As the mixing rate was set at 1500 rpm, the number of beads was less than that prepared at 1000 rpm, but these beads have more uniform size and their shape is spherical (see **Figure 1.d**). However, when the mixing rate was 2000 rpm, no beads were successfully prepared, as shown in **Figure 1.b**. Therefore, mixing rates have significant influences on beads preparation, because high-speed mixing rate (1000 or 1500 rpm) can make monomer and zeolite dispersed homogenously under the effect of strong centrifugal force and beads were formed rapidly. However, when the mixing rate is too high, such as 2000 rpm, monomer was too quickly dispersed compared to zeolite powder which prevented the beads formation.

PEGDA has also been used as organic binder. Few beads were observed at 1500 rpm (see **Figure 1.e**). When the mixing rate was 1000 rpm (see **Figure 1.f**), more beads could be prepared, but their size were not yet uniform. This could be explained by the low viscosity of
PEGDA, which makes it negative to be used as binder to crosslink zeolite powder to obtain beads like EPOX.

Based on above discussion, EPOX based formulation at 1500 rpm is more efficient for beads preparation, according the uniform beads size; cationic polymerization is also found more adapted for bead formation. The weight yield in beads formation (all sizes) is 85%. It's detailed according to the beads size in **Table 1**. In our previous work, when a formulation containing 80 wt% zeolite was selected, the structured objects could not be obtained with the absence of organic solvent toluene, and after these objects should be placed at 50 °C oven overnight for solvent evaporation. Here, bead composites can be obtained directly after photopolymerization, without solvent, and solvent evaporation process also can be omitted.

<figure><img src="image_5.png" /><figcaption>**Figure 1.** Photocured LTA-5A beads containing EPOX or PEGDA prepared at different mixing rates: (a) EPOX at 500 rpm, (b) EPOX at 2000 rpm, (c) EPOX at 1000 rpm, and (d) EPOX at 1500 rpm, (e) PEGDA at 1500 rpm, and (f) PEGDA at 1000 rpm.</figcaption></figure>

<caption>**Table 1.** The yield of beads with different diameters.ª</caption>
<table><thead><tr><td>Diameter (mm)</td><td>Yield (wt%)</td></tr></thead><tbody><tr><td>0-1.0</td><td>25.2</td></tr><tr><td>1.0-2.0</td><td>39.9</td></tr><tr><td>2.0-3.0</td><td>19.9</td></tr><tr><td>Unformed part</td><td>15.0</td></tr></tbody></table>

a) These beads were obtained (80wt% LTA-5A, 20wt% EPOX) at 1500 rpm after 3 batches.

## 2.2 Thermal Property of LTA-5A Beads Composites

In order to ascertain the LTA-5A content (ZC) of composite beads, TGA experiments were performed on composite beads from three batches. As shown in **Figure 2**, TGA were carried out on LTA-5A powder, pure EPOX based polymer and composite beads obtained at 1500 rpm. The weight loss observed for LTA-5A at T < 350°C (WL1, weight loss from 30-350 °C) is related to water desorption (physisorbed water). EPOX polymer degrades in two steps, at 30-350 °C (WL1) and 350-600 °C (WL2, weight loss from 350-600 °C). After TGA process, the LTA-5A powder and EPOX polymer lost around 18.1 wt% and 98.6 % respectively.

Composite beads (mixture of 1st, 2nd and 3rd batch) are logically associated to weight losses from zeolite and EPOX polymer. They have a similar residual weight (RW, 67.3 wt%, 68.1 wt% and 65.6 wt%, respectively) which no longer changes after 500 °C. As reported in **Table 2** taking into account the hydration rate of zeolite, ZC in each batch was around 80 wt%. It means that after high-speed mixing and photopolymerization processes, beads composition is similar whatever the size. However, the first and second weight losses values depend on the batch: the first decreases while the second increases with the batch number. It can be related to the beads size of batch 1st, 2nd and 3rd which correspond to 2.5-3.0 mm, 1.0-2.5 mm and less than 1 mm (0-1 mm) respectively. Because of the high heating rate (10 °C.min⁻¹), water desorption takes more time in bigger beads because of diffusion. Thus, water desorption has not finished when the polymer begins to decompose which induces increasing of the second weight loss. In addition, two Tmax values corresponding to polymer decomposition process are observed: they are all associated to temperature range of ca.230-260 °C and 400-410 °C (**Figure 2.b**). Therefore, the method proposed in this work can help to prepare composites beads with different sizes and LTA-5A content also can be controlled at 80 wt%.
<figure><img src="image_6.png" /><figcaption>**Figure 2.** (a) TGA and (b) DTG (derivative of TGA) curves for LTA-5A powder, EPOX polymer and LTA-5A filled composite beads. Composites beads (80wt% LTA-5A, 20wt% EPOX) were prepared at 1500 rpm.</figcaption></figure>

<table><caption>**Table 2.** Weight loss values highlighted by TGA for LTA-5A, EPOX polymer and LTA-5A filled composite beads.<sup>a</sup></caption><thead><tr><th></th><th>LTA-5A</th><th>EPOX<br>Polymer</th><th>Composite<br>Beads-1<sup>st</sup></th><th>Composite<br>Beads-2<sup>nd</sup></th><th>Composite<br>Beads-3<sup>rd</sup></th></tr></thead><tbody><tr><td>T max (°C)</td><td>/</td><td>290, 368,<br>404</td><td>246, 410</td><td>254, 405</td><td>236, 404</td></tr><tr><td>WL1 (wt%)<br>(30-350 °C)<sup>b</sup></td><td>17.0</td><td>14.4</td><td>7.21</td><td>10.1</td><td>16.8</td></tr><tr><td>WL2 (wt%)<br>(350-600 °C)<sup>c</sup></td><td>1.1</td><td>84.2</td><td>25.6</td><td>21.8</td><td>17.6</td></tr><tr><td>RW (wt%)<sup>d</sup></td><td>81.9</td><td>1.4</td><td>67.3</td><td>68.1</td><td>65.6</td></tr><tr><td>ZC (wt%)<sup>e</sup></td><td>/</td><td>/</td><td>81.8</td><td>82.8</td><td>79.7</td></tr></tbody></table>

<footnote><sup>a)</sup> Composites beads (80wt% LTA-5A, 20wt% EPOX) were prepared at 1500 rpm</footnote>

<footnote><sup>b)</sup> WL1: weight loss from 30-350 °C</footnote>

<footnote><sup>c)</sup> WL2: weight loss from 350-600 °C</footnote>

<footnote><sup>d)</sup> RW: residual weight after TGA</footnote>

<footnote><sup>e)</sup> ZC: calculated zeolite content of sample</footnote>
## 2.3 Load Bearing Experiment

After calcination, in order to evaluate the structure strength of these beads, load bearing experiments were performed on calcined beads (0.1 g) by using weights (100 g and 200 g). All calcined beads can keep the geometry shape and structure when a 100 g weight was placed on the beads (Figure S1). But when the test was continuously performed with a 200 g weight, different results were observed. As shown in Figure 3.a, Calcined Beads@2.0-3.0mm can stand the 200 g weight without breaks, which means these beads have stable structure. When a 200 g weights was placed on Calcined Beads@1.0-2.0mm (Figure 3.b), some beads broke, as highlighted in red circle. When the same test was performed on Calcined Beads@0-1.0mm, it can be observed that many of these beads were broken as highlighted in red circle in Figure 3.c. It is obvious to observe that more and more beads can be broken with the decreased bead size, which indicates that the structure strength could be affected by the bead sizes. It could be related to the layer-by-layer process for bead formation, because when the more layers are formed, the more stable the structure would be. But it's interesting to note that a small proportion of beads was fragmented, which means that these binder-free beads able to withstand a certain mechanical strength. The same experiment was also performed on commercial LTA-5A beads, and they could keep the structure without breaks, which means commercial beads have a good loading bearing ability.
<figure><img src="image_7.png" /><figcaption>**Figure 3.** Load bearing tests (with 200 g) on calcined zeolite beads: (a) Calcined Beads@2.0-3.0mm, (b) Calcined Beads@1.0-2.0mm, (c) Calcined Beads@0-1.0mm and (d) commercial LTA-5A Beads.</figcaption></figure>

**2.4 X-ray diffraction and X-ray fluorescence**

After calcination, these calcined zeolite beads with different sizes were characterized by XRD to control the stability of the zeolite structure. As shown in **Figure S2**, the XRD patterns of these calcined zeolite beads were similar to that of LTA-5A powder, in agreement with the
literature (ICDD 04-017-3644). This indicates that the calcination process did not have a
significant effect on zeolite structure.

X-ray fluorescence was performed on LTA-5A powder and Calcined Beads@2.0-3.0mm, Calcined Beads@1.0-2.0mm (see **Table S2**). Compared to LTA-5A powder, the change of the Si/Al ratio and Na/Al ratio for Calcined Beads@2.0-3.0mm, Calcined Beads@1.0-2.0mm is not significant, which means photopolymerization and calcination treatment do not have obvious influence on zeolite.

**2.5 N₂ sorption and CO₂ adsorption**

N₂ sorption measurements were performed to evaluate the textural properties of calcined zeolite beads. As shown in **Figure 4.a**, isotherms of LTA-5A powder, calcined LTA-5A powder calcined beads are type I characteristic of microporous solids. Compared to LTA-5A powder, a similar microporous surface area ($S_{Micro}$) of calcined LTA-5A powder, which means the calcination process does not have an obvious influence on the zeolite textural properties (see **Figure 4.a** and **Table 3**). At the same time, the calcined beads have lower BET surface area ($S_{BET}$) and microporous volume ($V_{Micro}$) than LTA-5A powder (especially Calcined Beads@1.0-2.0mm and Calcined Beads@2.0-3.0mm), and the micropore size at 0-1 nm also have an obvious decline tendency (see **Figure 4.c**), which could be explained by the low residual carbon formed during calcination partially blocking the micropores, and crystal agglomerates. Because when the beads with larger size are prepared, the crystal aggregation could be more obvious, which results in the decreasing textural properties. Interestingly, as shown in **Figure 4.d**, mesopores (diameter 3.4 nm) from interparticle porosity can be observed on Calcined Beads@1.0-2.0mm and Calcined Beads@2.0-3.0mm, and compared to our calcined beads, LTA-5A commercial beads have lower BET surface area and microporous volume and bigger mesopores (23 nm). In addition, no mesopores can be observed for calcined LTA-5A powder. The ratio of Si/Al of LTA-5A commercial beads is 1.3, which is higher than that of LTA-5A powder (Si/Al=0.9), which indicates inorganic binder was used for LTA-5A commercial beads preparation, resulting in the presence of mesopores and the lower $S_{BET}$. Therefore, these results indicate that the calcined zeolite beads could be used as adsorbents, depending on their interesting microporous volumes.

The CO₂ adsorption isotherms are shown in **Figure 4.b**, and adsorption capacities (mmol.g⁻¹) are listed in **Table 3**. The measured CO₂ uptakes (at p/p⁰ = 0.030) of LTA-5A powder, calcined beads (0-1.0 mm, 1.0-2.0 mm, and 2.0-3.0 mm), and commercial beads are 115, 109, 100, 102 and 87.4 cm³.g⁻¹, respectively. The values for the calcined beads are 5-8% lower than that of LTA-5A powder, but 14-24% higher than that of commercial beads. This could be
explained by the presence of low residual carbon which would partially block access to micropores in calcined beads, and by the presence of inorganic binder in the commercial product. In addition, compared to the CO2 adsorption capacity values of zeolite beads from other references listed in **Table 4**, zeolite beads in this work have a comparable CO2 adsorption capacity. Therefore, the calcined beads in this work can be used as adsorbent for CO2 adsorption.

<figure><img src="image_8.png" /><figcaption>**Figure 4.** (a) N₂ adsorption-desorption isotherms, (b) CO₂ adsorption isotherms for LTA-5A powder, zeolite beads with different sizes, and commercial LTA-5A beads, (c) pore size distributions (micropore) of LTA-5A powder, calcined LTA-5A powder, various calcined beads and commercial beads (DFT plot) and (d) pore size distributions (mesopore) of various calcined beads and commercial beads (BJH plot).</figcaption></figure>

<caption>**Table 3.** Textural properties of LTA-5A powder, calcined beads with different diameter and LTA-5A commercial beads after N₂ adsorption-desorption and CO₂ adsorption.</caption>
<table><caption>Table 4. CO₂ adsorption capacity of different zeolite beads.</caption><thead><tr><th></th><th>S<sub>BET</sub><br>(m<sup>2</sup>.g<sup>-1</sup>)</th><th>S<sub>Micro</sub><br>(m<sup>2</sup>.g<sup>-1</sup>)</th><th>S<sub>External</sub><br>(m<sup>2</sup>.g<sup>-1</sup>)</th><th>Mesopore<br>diameter<br>(nm)</th><th>V<sub>Micro</sub><br>(cm<sup>3</sup>.g<sup>-1</sup>)</th><th>CO<sub>2</sub><br>quantity<br>adsorbed<br>(cm<sup>3</sup>.g<sup>-1</sup>)</th><th>CO<sub>2</sub><br>quantity<br>adsorbed<br>(mmol.g<sup>-1</sup>)</th></tr></thead><tbody><tr><td>LTA-5A<br>Powder</td><td>706</td><td>664</td><td>42</td><td>/</td><td>0.25</td><td>115</td><td>5.1</td></tr><tr><td>Calcined<br>LTA-5A<br>Powder</td><td>670</td><td>661</td><td>9</td><td>/</td><td>0.26</td><td>/</td><td>/</td></tr><tr><td>Calcined<br>Beads@0-1.0mm</td><td>688</td><td>674</td><td>14</td><td>/</td><td>0.25</td><td>109</td><td>4.9</td></tr><tr><td>Calcined<br>Beads@1.0<br>-2.0mm</td><td>648</td><td>603</td><td>45</td><td>3.4</td><td>0.22</td><td>100</td><td>4.4</td></tr><tr><td>Calcined<br>Beads@2.0<br>-3.0mm</td><td>586</td><td>549</td><td>37</td><td>3.4</td><td>0.20</td><td>102</td><td>4.5</td></tr><tr><td>Commercial<br>1 Beads<br>(2.4-4.8<br>mm)</td><td>515</td><td>431</td><td>84</td><td>23</td><td>0.17</td><td>87.4</td><td>3.8</td></tr></tbody></table>

<table><thead><tr><th></th><th>Temperature<br>(K)</th><th>Pressure</th><th>CO<sub>2</sub> adsorption<br>capacity (mmol.g<sup>-1</sup>)</th><th>Reference</th></tr></thead><tbody><tr><td>Commercial binder-<br>free 4A zeolite<br>beads a</td><td>313</td><td>350 KPa</td><td>4.65</td><td>[12]</td></tr><tr><td>Binderless beads of<br>13X zeolite</td><td>313</td><td>405.3 KPa</td><td>&gt;5.0</td><td>[23]</td></tr><tr><td>Zeolite<br>13X/chitosan<br>aerogel beads</td><td>273</td><td>100 KPa</td><td>4.23</td><td>[16]</td></tr><tr><td rowspan="3">Commercial zeolite<br>5A beads</td><td>248</td><td>6.28 KPa</td><td>4.64</td><td rowspan="3">[36]</td></tr><tr><td>273</td><td>28.3 KPa</td><td>4.55</td></tr><tr><td>298</td><td>40.0 KPa</td><td>4.00</td></tr></tbody></table>
<table><tbody><tr><td rowspan="3">Commercial zeolite<br>13X beads</td><td>248</td><td>9.37 KPa</td><td>5.09</td><td rowspan="3">[36]</td></tr><tr><td>273</td><td>19.1 KPa</td><td>4.51</td></tr><tr><td>298</td><td>30.5 KPa</td><td>3.85</td></tr><tr><td>Calcinated<br>Beads@0-1.0mm</td><td>273</td><td>105 KPa</td><td>4.9</td><td rowspan="4">This work</td></tr><tr><td>Calcinated<br>Beads@1.0-2.0mm</td><td>273</td><td>105 KPa</td><td>4.4</td></tr><tr><td>Calcinated<br>Beads@2.0-3.0mm</td><td>273</td><td>105 KPa</td><td>4.5</td></tr><tr><td>LTA 5A<br>Commercial Beads</td><td>273</td><td>105 KPa</td><td>3.8</td></tr></tbody></table>

a) CO₂ adsorption was carried out on commercial binder-free 4A zeolite beads on Fixed bed.

## 2.6 Scanning Electron Microscope

Scanning Electron Microscope (SEM) analyses were performed to characterize beads surface and core (see **Figure 5**). As shown in **Figure 5.c**, a spheroidal shape can be observed from calcinated beads, and the surface is flat without roughness. This demonstrates the process of high-rate mixing is favorable to form spheroidal beads and calcination process did not have an obvious damage on surface structure. On the cross-section view (**Figure 5.a, 5.b and 5.d**), significant layers can be observed, which indicates a layer-by-layer process to manufacture beads was performed during high-rate mixing process. As shown in **Figure 5.e**, LTA-5A crystals kept easily recognizable well-shaped cubic morphology after photopolymerization and calcination processes.
<figure><img src="image_9.png" /><figcaption>**Figure 5.** SEM images for Calcined Beads@1.0-2.0mm: (a) and (b) Cross-section, and (c) Surface; Calcined Beads@2.0-3.0mm: (d) and (e) SEM images of cross-section Beads@2.0-3.0mm.</figcaption></figure>

**3. Conclusion**

Zeolite LTA-5A powder was successfully transformed into zeolite beads composites (zeolite content 80 wt%) by consecutive high-speed mixing and photopolymerization steps, and then zeolite beads were obtained *via* calcination process. According to the thermal stability of LTA-5A zeolite, calcination process did not have significant influence on zeolite crystal structure and calcined beads had a good structure strength (partial bead fragmentation (0.1 g beads) under 200 g-load). Besides providing mechanical strength, calcined beads also had good CO₂ adsorption capacity (4.5-4.9 mmol.g⁻¹), higher than commercial LTA-5A beads (3.8 mmol.g⁻¹). Therefore, this work can help to provide a new way to prepare binder-free zeolite beads for many applications.
# 4. Experimental Section

## 4.1 Chemical Compounds

The resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (Uvacure 1500, EPOX), and poly(ethylene glycol) diacrylate (PEGDA, Mw ~ 610 g.mol⁻¹) were purchased from Allnex and Sartomer (SR610) respectively. The photoinitiating system consisted of 2-isopropylthioxanthone (ITX) and bis(4-tertbutylphenyl)iodonium hexafluorophosphate (Iod), which were both obtained from Lambson Ltd (Wetherby, United Kingdom). The photoinitiator 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (BDMK) was purchased from Sigma-Aldrich. The LTA-5A zeolite powder and the commercial zeolite beads were from Union Carbide and Acros Organics respectively. These organic compounds are presented in Scheme S1 and the characteristics of LTA-5A zeolite (powder and beads) were reported in Table S1.

## 4.2 Preparation of Zeolite Beads

Firstly, ITX/Iod/EPOX1500 or BDMK/PEGDA were added into a non-transparent bottle and were mixed homogenously in Speedmixer (DAC 150.1FVZ-K) with a speed at 1000-1500 rpm. Secondly, zeolite powder was added into the bottle firstly and the monomer liquid mixture was dropped on the surface of zeolite powder after. Zeolite powder and monomer liquid mixture were mixed together to form composite beads with speed at 500-2000 rpm for 5 min. During this step, many intact uncured beads were formed, and the surplus mixture deposited on the bottom of the bottle formed a block. After being weighed, the surplus part was mixed again to form more beads. This step should be carried out for three times to prepare three batches of beads with different sizes, and these beads were defined as composite beads-1st, composite beads-2nd and composite beads-3rd respectively. In a LED-curing box, these uncured beads were placed vertically under the near-UV light (LED@405nm, 4500 mA for 1 min) to obtain cured composite beads.

After photopolymerization, all cured composite beads (1st, 2nd and 3rd) were mixed together and then calcination was carried out on the mixed cured composite beads at 600 °C under air for 30 min in the Muffle Furnace (heating rate at 1 °C.min⁻¹, under air) to remove organic compounds to obtain calcined beads. According to their different sizes, calcined beads were sieved to obtain three categories: 0-1.0 mm, 1.0-2.0 mm and 2.0-3.0 mm and referenced as Calcinated Beads@0-1.0mm, Calcinated Beads@1.0-2.0mm, and Calcinated Beads@2.0-3.0mm respectively.

## 4.3 Material Characterization
Thermogravimetric analyses (TGA) were carried out using a thermal analyzer (METTLER-TOLEDO TGA/DSC 3+) by heating from 30 to 600 °C under nitrogen atmosphere (N₂ flow rate: 100 mL.min⁻¹, heating rate: 10 °C.min⁻¹). Zeolite crystalline structures were identified by X-ray diffraction (XRD) measurements using a PANalytical MPD X'Pert Pro diffractometer operating with Cu Kα radiation (Kα = 0.15418 nm) equipped with an PIXcel real-time multiple strip detector (active length = 3.347° (2θ)). The powder patterns were collected at 295 K in the range 3 < 2θ < 70, step = 0.013° (2θ), time/step = 220 s. Elemental analyses were performed by X-Ray fluorescence spectrometry (XRF) on a PANalytical Zetium (4 kW) spectrometer. Samples were mixed with boric acid and pressed into pellets of 13 mm diameter with 5 tons of pressure before the analysis. Zeolite crystal size and morphology, and their corresponding were investigated by scanning electron microscope (SEM) with a JEOL JSM-7900F microscope.

## 4.4 N₂ Adsorption Measurements

Nitrogen (N₂) adsorption-desorption isotherms were performed at -196 °C with a Micromeritics ASAP 2420 Instrument on calcined beads. Before each measurement, the samples were outgassed to a residual pressure of less than 0.8 Pa at 90 °C for 1 h and 300 °C for 15 h. Specific surface areas were calculated according to the Brunauer-Emmett-Teller (BET) method (0.01 < *p*/*p*° < 0.03). Microporous volume (Vₘicro) and microporous surface area (Sₘicro) were calculated using the *t*-plot method. The external surface (S<sub>ext</sub>) was obtained by subtracting Sₘicro from the total surface. Micropore size distributions and Mesopore size distributions were calculated by the DFT method and the BJH (Barrett-Joyner-Halenda) method on the desorption branch of the isotherm respectively.

## 4.5 CO₂ Adsorption Measurements

The CO₂ adsorption capacity of the composites after thermal treatments has been achieved at 0 °C with a Micromeritics ASAP 2420 Instrument under 105 KPa. Before each measurement, the samples were outgassed to a residual pressure of less than 0.8 Pa at 90 °C for 1 h and 300 °C for 15 h.

## Supporting Information

Supporting Information is available from the Wiley Online Library or from the author.

## Acknowledgments

Authors wish to acknowledge the financial support from the Region Grand Est (France) for the grant "MIPPI-4D".
**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.

**Notes**

Any additional relevant notes should be placed here.

**Author Contributions**

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

**Abbreviations**

VOCs, volatile compounds; PEGDA, polyethylene glycol diacrylate; EPOX, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; ITX, 2-isopropylthioxanthone; Iod, bis(4-tert-butylphenyl) iodonium hexafluorophosphate; BDMK, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone; TGA, thermogravimetric analyses; WL1, weight loss from 30-350 °C; WL2, weight loss from 350-600 °C; ZC, LTA-5A content; RW, residual weight; SEM, scanning electron microscope; XRD, X-ray diffraction; N₂, nitrogen; CO₂, carbon dioxide; V<sub>micro</sub>, microporous volume; S<sub>micro</sub>, microporous surface area; S<sub>ext</sub>, external surface; S<sub>BET</sub>, specific surface area, BET, Brunauer-Emmett-Teller; BJH, Barrett-Joyner-Halenda; DFT, Density Functional Theory.
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Table of contents

A novel process for binder free zeolite beads preparation was proposed. These beads were formed through i) high-speed physical mixing of monomer and zeolite powder, ii) photopolymerization and iii) calcination. Finally, these beads had a good performance for CO2 adsorption.

<figure><img src="image_10.png" /></figure>