Next Article in Journal
Towards Solving the Beach Litter Problem: Ecosystem Service Assessments at North African Coasts
Previous Article in Journal
Depth and Width of Collaborative Innovation Networks and High-Quality Development
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Sustainability
Volume 16
Issue 14
10.3390/su16145910
sustainability-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

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

Obtaining Zeolites from Natural Materials of Volcanic Origin for Application in Catalytic Pyrolysis for the Sustainable Chemical Recycling of Polymers

by
Angel Gabriel Valencia-Huaman
1,
Sandro Henry Fuentes-Mamani
1,
Luis Fernando Mamani-De La Cruz
1,
Francisco Velasco
2,
Rossibel Churata
3,
Alejandro Silva-Vela
3,
Jose Mamani-Quispe
1 and
Jonathan Almirón
1,*
1
Escuela Profesional de Ingeniería Ambiental, Facultad de Ingeniería de Procesos, Universidad Nacional de San Agustín de Arequipa, Calle Santa Catalina Nro. 117 Cercado, Arequipa 04001, Peru
2
Materials Science and Engineering Department, IAAB, Universidad Carlos III de Madrid, 28005 Madrid, Spain
3
Escuela Profesional de Ingeniería de Materiales, Facultad de Ingeniería de Procesos, Universidad Nacional de San Agustín de Arequipa, Calle Santa Catalina Nro. 117 Cercado, Arequipa 04001, Peru
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(14), 5910; https://doi.org/10.3390/su16145910
Submission received: 7 May 2024 / Revised: 23 June 2024 / Accepted: 2 July 2024 / Published: 11 July 2024
Browse Figures
Versions Notes

Abstract

:
The present investigation studies the use of three natural precursors of volcanic origin (pozzolana, ignimbrite and pumice) in the synthesis of low-cost and environmentally friendly zeolites. The developed zeolites were evaluated as sustainable catalysts for the catalytic pyrolysis process in the chemical recycling of polypropylene. A zeolite was synthesized from each precursor. The hydrothermal treatment was performed with NaOH (3M) at 160 °C for 72 h and NH4Cl (1M) was added to convert it into proton form. The synthesized zeolites were characterized by FTIR, XRD, SEM and BET. The evaluation of the catalytic ability of the obtained zeolites was carried out with polypropylene mixed with a 4, 6 and 8 wt.% catalyst in a ceramic crucible. Pyrolysis was always carried out at 450 °C and for 30 min in a tubular furnace with a continuous flow rate of 250 L·min−1 of gaseous nitrogen. The gases generated were captured in the cooling system. The characterized zeolites show a resemblance to the ZSM-5 commercial zeolite, especially for the ignimbrite and pozzolan zeolites. Likewise, in pyrolysis, liquid products, gases and waxes were obtained. As the amount of catalyst was increased (from 4 to 8%), the yield of the desired liquid–gas products was also increased. The synthesized zeolites showed similar pyrolytic characteristics to ZSM-5, although they did not reach the same pyrolytic efficiency. Zeolites improved the pyrolysis products, especially at 8 wt.%, when compared to thermal pyrolysis. This study highlights the potential of the developed zeolite catalysts to efficiently convert PP into valuable light olefins, advancing sustainable polyolefin recycling technologies.

1. Introduction

Southern Peru is located in the central volcanic zone of the Andes, part of the Pacific Ring of Fire. This region has witnessed a large number of volcanic phenomena, with large emissions of volcanic material throughout history [1]. Depending on the specific formation and cooling conditions during volcanic activity, different volcanic materials can form (ignimbrite, pumice, pozzolana, obsidian, etc.). These materials present optimal properties in terms of their chemical stability, thermal stability, hardness, etc., and, thanks to their high Si and Al proportions [2], they show characteristics that make them valid as precursors for the formation of geopolymers [3] or synthetic zeolites [4,5].
Synthetic zeolites are solid minerals composed of Si, Al and O in high proportions, with well-organized three-dimensional structures. They act as a selective molecular sieve [6,7] in terms of the type, size and polarity of the molecule [8], taking advantage of the acid sites. This enhances their applicability to different needs in industry and science. Moreover, the synthesis conditions (concentration, temperature and time) [9] can be easily controlled. The current specialized routes (seed-assisted synthesis, microwave, sonic, etc.) are efficient for the synthesis of zeolites, such as the synthesis of Soconi Mobile Zeolite (ZSM) [10,11,12], which is widely used at an industrial scale. However, ZSM synthesis requires immense logistics and a considerable energy demand, and presents difficulties in terms of its scalability to the industry. In contrast, the conventional route used in this research has a low cost, takes advantage of the abundance and properties of sustainable natural precursors, can be easily replicated and can be assisted through the use of an organic template as a directing agent to control the formation of the desired structure. Nevertheless, all of these methods involve hydrothermal conditions, that promote nucleation processes, changes in intermediate phases and selective crystallization [8].
In 2022, the zeolite market reached a production of 2.1 Mt, projecting an evolution rate of 2.3% by 2028. Expected market demand will be satisfied with new industrial methodologies [6] since the flexibility of their application covers many fields of study. The research of Zaarour et al. found photovoltaic and antimicrobial applications that could increase the efficiency of zeolites after doping with cation Ag [9]. Williams et al. gathered information on the potential applications of zeolites [13]. One of their very common applications is in environmental treatment, taking advantage of the size of the pore for the absorption of metals such as Pb+2, in which good results were obtained with the NaP1 zeolite and Sodalite [14]; on the other hand, the use of pumice stone as a precursor served to synthesize NaP1 zeolite and Phyllipsite, which also obtained optimal results for environmental remediation [4,13,15] and improvements in agricultural soil as a water retainer [16].
In addition to the aforementioned studies, zeolites are often used as heterogeneous catalysts by the catalytic cracking industry due to their potential ability to chemically recycle petroleum-based polymers into functional monomers (depolymerization) [17,18,19]. Different catalysts in catalytic pyrolysis and the gasification of waste plastics are used to improve product selectivity. The selection of the appropriate catalyst for the decomposition of waste plastics can improve the conversion rate and promote high yields of gaseous products and syngas [20]. The catalytic effect of ZSM-5 (MFI type; 10-membered rings; constructed from a pentasyl unit) and zeolite-y (FAU type; 12-membered rings; constructed from a sodalite unit) catalysts has been extensively studied. It has been identified that structural changes in zeolite catalysts can increase the yield of valuable products, isomerize the main carbon structure and decompose heavy compounds and convert them into aromatics [21]. Research conducted on catalytic cracking by Zang et al., with low-density polyethylene (LDPE) and the synthesized zeolite ZSM-5, evidenced a better performance for oils and a clear pyrolysis temperature decrease of more than 50 °C [22]. Furthermore, the acid-active sites generate compounds of a lower molecular mass [23]. There is also polypropylene (PP), a similar polymer with exceptional chemical resistance and the ability to withstand high temperatures, which is widely used in domestic and industrial activities (containers, plastic bags, packaging, pieces of machinery, etc.). Together with PE, up to 2021, plastic producing industries represented 76% of plastic production in Peru, with the construction, commerce, beverage and chemical products manufacturing industries serving as the target markets [24].
Santoso et al. activated a natural zeolite, abundant in the mordenite phase, for the pyrolysis of PP and LDPE, obtaining mostly alkanes, alkenes and phenols [25]. Paula et al. worked with mordenite, ZSM-5 and their alkali modifications for the pyrolysis of PP, PS and PE mixed plastics, obtaining more aromatic and light fraction compounds for the modified mordenite and a higher liquid fraction for the modified ZSM-5 [26]. Wang et al. worked with PP to obtain abundant C3–C5 alkenes after its thermal pyrolysis, together with benzene, toluene and xylene (BTX) at a temperature of 300 °C using the HZSM-5 zeolite [27].
This study presents an application of the catalytic pyrolysis of polypropylene to obtain the polymer precursor raw materials using synthetic zeolites prepared from natural precursors (pozzolana, pumice and ignimbrite). Those precursors were chosen as they are abundant in the southern Peruvian regions, being cheap and with suitable compositions for this application. The zeolitization of these precursors will improve the catalytic activity (cracking) and optimize chemical recycling alternatives for polymers in the country.

2. Materials and Methods

2.1. Materials

The zeolites were synthesized from three precursor materials such as pozzolana (PO), pumice (PU) and ignimbrite (IG), which were collected from different areas of the province of Arequipa (Peru). These 3 materials are abundant in the area. Composition of each precursor may change among different locations and it should be checked if a scalable process would be developed.
The collected precursor materials were initially conditioned by removing impurities (plant debris and rocks), then dried, crushed and subsequently ground in a ball mill. Then, they were sieved to obtain fine particles, using a sieve of mesh N°. 140 (106 μm). The raw material obtained after sieving was characterized by X-ray fluorescence (XRF), using a Rigaku NEX QC + QuantEZ dispersive fluorescence equipment (Austin, TX, USA). Table 1 shows the results obtained, with the three precursors having more than 87% silicon and aluminum oxides in their composition, which are the basic components for the synthesis of zeolites.
All chemicals and reagents were used of analytical quality without further purification. The materials used included NaOH (Scharlau, Barcelona, Spain), sodium silicate (Na2SiO3) from Scharlab (Barcelona, Spain), tetrapropylammonium bromide (TPABr) at 98% purity (Sigma-Aldrich, Bangalore, India), concentrated sulfuric acid (H2SO4) and NH4Cl from CV avantor (Ecatepec, Mexico), and commercial zeolite (ZSM-5) from Zeolyst International (Kansas City, MO, USA).

2.2. Zeolite Synthesis

For the synthesis of the different zeolites, the procedure performed by Vichapund et al. [28] and Soongprasit et al. [29] was followed, with certain modifications. In total, 12 g of each precursor were mixed with 100 mL of NaOH (3M) solution and stirred under a reflux condition at 60 °C for 3 h to form a mixed solution of silicate and aluminate [29]. Then, over a period of 10 min at room temperature and under stirring, 31.9 g of Na2SiO3 was added. Subsequently, 18.93 g of TPABr was added, fractionating the application to 0.42 g·min−1 and then agitated for 3 h at room temperature. After agitation, the pH of the gel obtained was reduced to 11 with H2SO4, subjected to hydrothermal treatment in a Teflon-coated stainless steel autoclave at 160 °C for 72 h and then left to cool at room temperature overnight. Material was then washed and filtered until a pH < 9 was reached, and then it was dried in an oven at 100 °C for 24 h. To remove the organic fraction of TPABr, it was then calcinated in a tubular furnace at 540 °C for 5 h. With the intention of obtaining an acidified zeolite [28], the cooled product of the previous step was mixed with NH4Cl (1M), in the following relation: 30 mL of NH4Cl for each gram of product. The obtained solution was subjected to reflux at 50 °C for 4 h; then, filtration and washing were carried out in order to remove the chloride ions. The whole procedure was repeated, extending the stirring time to 6 h in this phase. To obtain final zeolites, the material was dried at 100 °C for one night and then calcinated at 540 °C for 5 h. The 3 zeolites obtained this way are labeled as HZ-PO (pozzolana zeolite), HZ-IG (ignimbrite zeolite) and HZ-PU (pumice zeolite) throughout the text.
The commercial zeolite (ZSM-5), the powdered precursor materials (PO, IG and PU) and the products obtained from the synthesis (HZ-PO, HZ-IG and HZ-PU) were subjected to Fourier Transform Infrared (FTIR) analysis, which was performed on a Perkin Elmer Frontier FT-IR/NIR model (Waltham, MA, USA), within a scanning range of 4000–650 cm−1. In addition, in order to identify and characterize the crystalline phases, X-ray diffraction (XRD) tests were performed using a Rigaku Miniflex 600 X-ray diffractometer (Tokyo, Japan), which involved a source of radiation CuKα, measuring at 40 kV and 15 mA, in the 2θ range of 3–90°. The morphological characteristics of the materials were analyzed using a Hitachi SU8230 scanning electron microscope (Hitachi High-Tech, Tokyo, Japan), with backscattered electrons (BSE), with image magnifications of 20,000× and 25,000×.

2.3. Catalytic Pyrolysis

Catalytic pyrolysis was performed on 5707N commercial polypropylene (PP) from SABIC (Ningbo, China) and was carried out in a 1 m long, 6 cm diameter quartz tube coupled to a horizontal tube furnace. The pyrolysis conditions were a temperature of 450 °C and 30 min. For each sample, catalytic pyrolysis was replicated three times, varying the zeolite amount at 4, 6 and 8 wt.% in relation to the PP. N2 was used, at a flow rate of 250 L·min−1, in order to have the chamber free of oxygen and avoid combustion reactions. The sample was placed in a rectangular ceramic crucible containing PP mixed with the synthesized zeolite. The sample was introduced into the quartz tube for 30 min and the nitrogen flow was maintained. The gases generated were captured in the cooling system consisting of a gas trap immersed in liquid nitrogen. A fraction of the gases was condensed in the traps and the fraction of non-condensed gases was released. After the pyrolysis time had elapsed, the sample was removed to cool to room temperature and, finally, the products generated were classified into three groups: liquid products, gaseous products and residues. Then, the liquid fraction was characterized by Fourier Transform Infrared (FTIR), on a model machine the Perkin Elmer Frontier FT-IR/NIR model, within a scanning range of 4000–650 cm−1.

3. Results

3.1. FTIR in Precursors and Synthesized Zeolites

The results of the characterization of the precursor materials, the synthesized zeolites and the commercial zeolite ZSM-5 are presented in Figure 1 within the range of the spectrum of 4500–650 cm−1. The spectra show prominent features attributed to silica and wastewater. Table 2 summarizes the band peaks presented in all materials.
Band spectra in the range 1700–650 cm−1 were magnified and superimposed in Figure 2 to differentiate the shift of the bands and the increase in the intensity of the peaks. The spectra of the precursor materials observed in the bands of the 1007 and 996 cm−1 (Figure 1 and Figure 2) correspond to the asymmetrical stretching vibrations of the T-O (T = Si or Al), as reported in other studies, being approximations [30] or within the range [31]. This would indicate the high concentration of silicon and aluminum, fundamental for the formation of zeolites, corroborating the XRF analysis (Table 1).
The band range between 1200 and 650 cm−1, which is shown in Figure 1 and Figure 2, relates to Si-O-T vibrations, taking place in the tetrahedral TO4 mode for the synthesized zeolites [32]. The peaks of higher intensity in the synthesized zeolites located within the band range of 1075–1024 cm−1 are related to the internal asymmetric stretching vibrations of the Si-O-T. In addition, these peaks (in the case of HZ-PO, HZ-IG and ZSM-5) are accompanied by shoulders in the 1210, 1219 and 1222 cm−1 bands, respectively, corresponding to the external asymmetric stretching vibrations of structures containing four five-membered ring chains arranged around a double screw axis [33]. The peaks in the range of 784–790 cm−1 found in ZSM-5, HZ-IG, HZ-PU and HZ-PO zeolites correspond to the external symmetrical stretching vibrations of Si-O-T [34], as reported by Dey [35] for the ZSM-5 zeolites obtained from rice husk ash. The presence of peaks near the 1220, 1080 and 790 cm−1 bands represents the formation of ZSM-5 type zeolites [33,35,36], with HZ-IG and HZ-PO zeolites showing the greatest similarity and which would represent the greatest success in the synthesis of this type of zeolites.
The presence of peaks in the band range 1618–1632 cm−1 in the synthesized zeolites and ZSM-5 is related to the H-O-H stretching and bending vibrations, which correspond to the water absorbed in the structure [30,37,38]. This could have occurred in the synthesis process, specifically in the washing stage, and its low intensity would indicate a small presence of water since most of it was removed in the drying and calcination processes.
The presence of water in the structure can modify the zeolite skeleton upon temperature increase, causing hydrolysis of Si-O-Al bonds and removal of Al by dehydroxylation [39]. The removal of aluminum would lead to an increase in the Si/Al ratio and, consequently, to an increase in zeolite acidity.

3.2. XRD

Figure 3 shows the XRD patterns of the precursor minerals. The peaks that appear in the PO precursor are mainly crystalline phases of anorthoclase, muscovite and albite; in the IG precursor, the main crystalline phase is also anorthoclase, followed by cristobalite and albite. On the other hand, the main crystalline phase in PU is pyrite, followed by tremolite and anorthoclase. In the study by Vichaphund et al. [28] to synthesize zeolites from a fly ash precursor, quartz was the main crystalline phase. Although the three selected precursors used for zeolite synthesis have differences, they share in common that their crystalline phases present mainly silicon and aluminum. Anorthoclase is the crystalline phase that exists in the greatest amount of the three precursors studied. It is a feldspar consisting of aluminum silicates combined with varying percentages of potassium, sodium and calcium [40,41]. Likewise, from the precursor patterns shown in Figure 3, it can also be noted that the peaks are mainly located between the angles 15° and 40° (2θ). The presence of the open halo, especially in PU and PO, would also indicate the presence of thermodynamically metastable amorphous aluminosilicate structures with high pozzolanic activity [3]. Considering the above, positive results can be expected for obtaining zeolites since the basis of the synthesis consists of using the characteristics of silicon and aluminum, which easily dissolve in an alkaline solution [4]. Furthermore, this assumption is also supported by the studies of Rajakrishnamoorthy et al. [42] and Verrecchia et al. [43], to obtain ZSM-5 and NaX zeolites, respectively, from fly ash, showing both of them XRD patterns with crystalline phases of silicon and aluminum, whose peaks were also in the range of 15°–40° (2θ).
It can also be seen in Figure 3 that, among studied precursors, IG presents peaks of greater intensity, followed by PO and, with less intensity, PU. The latter presents more amorphous phases, resulting in the precursor with the lowest crystallinity [44]. This is also confirmed in the study by Wu et al. [4], showing that amorphous phases were predominant in the XRD pattern of pumice, with no evident peak, but a broad one from 10° to 40° (2θ).
Figure 4 shows the XRD patterns of the synthesized zeolites and the commercial ZSM-5. It can be observed that the intensity of the anorthoclase and the other crystalline phases have decreased since those peaks are no longer visually prominent. Instead, new peaks, with higher intensity, appear. Likewise, the HZ-PO shows a greater reduction in the anorthoclase intensity; on the other hand, for the HZ-IG and HZ-PU, this peak is also reduced, but it is still maintained. This reduction in the initial crystalline phases may be due to the dissolution of the precursors with an alkaline solution, which contributes to the increase in silicate and aluminate solutions present in the HZ-IG and HZ-PU [28]. The assumption is supported by the results of the study by Ojha et al. [45], where a reduction in quartz and mullite intensity after the synthesis process using NaOH was also observed.
On the other hand, the XRD patterns of the three synthesized zeolites show the appearance of peaks between 7° and 9° and between 22° and 25° (2θ), similar to the peaks presented by the commercial zeolite used in the present study. Those peaks are characteristic of the presence of ZSM-5 zeolite structures [31,46], and these ranges are shaded in Figure 4. Likewise, Soongprasit et al. [29] found XRD peaks at the same 2θ range (assigned to JCPDS 44-0003). However, Yu et al. [47] found XRD peaks of their synthesized zeolites located at those mentioned ranges and argued that they correspond to the characteristic peaks of the MFI (inverted mordenite framework) structure type of HZSM-5, indicating the formation of HZSM-5. This is supported by Zang et al. [22] and Rajaei et al. [48]. Thus, everything would indicate that, in the present study, it has been possible to synthesize zeolites of the HZSM-5 type, which is the protonated ZSM-5 zeolite.
According to Figure 4 and considering the shaded ranges, it is confirmed that, after the synthesis process, new crystalline phases corresponding to zeolite HZSM-5 have formed, which are not observed in the XRD patterns of the precursors. These results are due to the specific synthesis process of the precursors: they are placed in a NaOH solution which destroys the original structure and, when heated, a new mineral phase is formed by crystallization [4]. Finally, using NH4Cl resulted in the zeolite acquiring that acidic character, which is known as the ion exchange method and was similarly used by Rajaei et al. [48] to protonate ZSM-5 but making use of NH4NO3.
In Figure 4, it can be observed that the HZ-PO zeolite presents peaks of higher intensity, followed by HZ-IG, and HZ-PU showing the lowest intensity, which would indicate that the synthesized HZ-PO zeolite is the one that presents higher crystallinity [31] and the one that is closer to the commercial zeolite. This result shows that the used synthesis suits PO the best, while it scarcely performs on PU. The fact that crystalline phases of greater intensity were obtained in PO and IG could be due to the fact that they presented in their chemical composition a greater amount of Al2O3, since according to the study of Shigemoto et al. [49], Na-A zeolites were obtained that increased their crystallinity with the increase in the added NaAlO2 content. From this result, it can be assumed that the type of precursor influences the results of zeolite synthesis. In general, it can be clearly seen that the zeolites synthesized show higher crystallinity and less amorphous phases than their precursors.

3.3. SEM Analysis

The SEM images of the natural precursors and the synthesized zeolites are shown in Figure 5. The amorphous structures are evident, with the presence of flattened layers and irregular crystals of different sizes for the precursors (PO (Figure 5A), IG (Figure 5B) and PU (Figure 5C)). After the alkaline hydrothermal synthesis process, those mineral precursors formed ordered structures according to their silica-alumina proportions [50,51]. This can be seen for HZ-PO (Figure 5D), which had pozzolan as a precursor and presented abundant consolidated structures with an elongated hexagonal morphology of different sizes (between 2 and 3 µm). This form is typical for MFI (mobile five-membered ring)-, TON (Theta One Niner)- and MTT (Movil to TUN)-type structures. Those acicular crystalline aggregates (rods) are also similar to ZSM-5 and ZSM-22 [52]. Kocirik et al. found the same mean MFI pattern for Silicalica-1, which shares structure with ZSM-5, according to the International Zeolite Association (IZA) [53]. Verboekend et al. and Sousa et al. found that the intergrown phases between ZSM-5 and ZSM-22 by desilication had an influence on the formation of phases under simple synthesis conditions [54,55], since the structure of ZSM-22 and ZSM-23 zeolites, when having a longer duration in time in its crystallization phase, favors the formation of the mineral cristobalite and broadens the synthetic range for ZSM-5 [56,57]. For HZ-IG zeolite (Figure 5E), which had ignimbrite as a precursor, it fared relatively better. Although it presented a considerable amount of amorphous material in the form of grains, the zeolitized section had a hexagonal morphology (coffins) of approximately 1 µm, typical of ZSM-5 zeolite as mentioned in the study of Krisnandi et al. [31]. This type of zeolite was also synthesized by Yu et al. establishing a hierarchical HZSM-5 mesopore between 2 and 6 µm [47]. On the contrary, the zeolite HZ-PU (Figure 5F), which had pumice with a very evident vitreous form as a precursor, did not zeolitize in its totality in consolidated structures and formed very few elongated hexagonal structures of approximately 2 µm typical of the zeolites ZSM-5 and ZSM-22. Quite amorphous material remains in the shape of columns similar to its precursor. The previous results were compared with the SEM images of the commercial zeolite ZSM-5 (Figure 5G) which presented the typical coffin shape, a hexagonal morphology of approximately 120 nm in size; comparable results found by Zang et al. with a mean size of 40 nm confirmed the presence of MFI type zeolites [22].

3.4. BET Analysis

Table 3 summarizes the textural characteristics obtained by the Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods. As can be observed, the HZ-PO zeolite is the one that presents a higher specific surface area, but a smaller pore diameter. For the HZ-PU zeolite, the opposite occurs: a lower specific surface area, a larger pore diameter and additionally smaller micropore area and volume compared to the others.
The HZ-PO and HZ-IG zeolites present a high specific surface area while HZ-PU has a moderate one. All zeolites have a relatively low porosity (low pore volume), with mesopores predominating. Compared to the textural properties found in other research about the synthesis of ZSM-5 zeolites, it was found that the specific surface area and pore diameter range from 329 m2/g and 3.7 nm [29] to 453 m2/g and 3.3 nm [28], which makes a considerable difference to those synthesized in this research.

3.5. Pyrolysis Products

Figure 6 shows the distribution of the products obtained after the pyrolysis of PP using three different amounts (4, 6 and 8 wt.%) of the synthesized zeolites, as well as the products using the ZSM-5 commercial zeolite and the products obtained after a conventional thermal pyrolysis process.
Thermal pyrolysis (when no catalyst is used) produces a high amount of wax, and hence low percentages of liquid and gas. The use of zeolites varies the distribution, helping in some cases to obtain better products. However, it can be seen that the use of zeolites at 4% by weight does not change very much the obtained products when compared to those of thermal pyrolysis, since even slightly more wax is produced with HZ-IG and HZ-PU.
In all cases (thermal and catalytic pyrolysis), the amount of solids (Char) produced is always below 0.5%, without any noticeable difference among studied conditions. The fact that synthesized catalysts do not promote the formation of greater amounts of char is positive.
Increasing the proportion of zeolite from 4 to 8% decreases the amount of wax, indicating a better performance of zeolites when increasing the amount of catalyst. The maximum yield for liquid products is obtained for 8% of HZ-PO. In the case of HZ-PU, the amount of liquids is similar for the three percentages, although slightly higher for 4%. In the case of gases, the maximum yield for HZ-IG and HZ-PU is obtained for 8% addition, while the maximum yield for HZ-PO is 6%. Considering together the amount of gas and liquid produced and these being the main products to be obtained, it could be said that, in general, the best results are obtained for 8% of zeolite. Taking, then, into account that 8% of zeolite is necessary to obtain better pyrolysis products, HZ-PU stands out among the three synthetic zeolites, followed by HZ-IG.
However, although the three synthesized zeolites improve the results of the pyrolysis products when compared to thermal decomposition, they did not reach the efficiency of the commercial ZSM-5 zeolite, which shows higher percentages of liquid and gas with very little presence of wax. This may be due to the fact that the same textual characteristics of porosity and surface area of a ZSM-5 were not obtained [29].
This is supported by the study of Wong et al. [58] about PP pyrolysis with ZSM-5, obtaining up to 75.2% by weight of gas, up to 35.9% by weight of liquid and a low percentage of wax, similar to the majority of tests carried out. On the other hand, Zhou et al. [59] obtained good results when using ZSM-5 on polypropylene, where more liquid than gas was generated, which may be due to the different microwave-assisted pyrolysis methods.

3.6. Analysis of Pyrolysis Liquid Products

Qualitatively, the three FTIR spectra of the liquid products of pyrolysis with the synthesized zeolites present similar characteristic bands, with slight differences, as can be seen in Figure 7. The assignment of bands is indicated in Table 4.
The analysis reveals that the composition of the oils is largely dominated by paraffins followed by olefins. There is little presence of aromatics, and this can be explained by the absence of aromatic rings in the polymer main chain. Similar results were reported by Panda et al. [60] after the individual pyrolysis of PP. On the other hand, Miandad et al. [61] reported a composition of kerosenes, olefins, aldehydes and aromatics, being this a very complex composite composition. The result of the latter study may be due to the type of pyrolysis, which was exclusively thermal. Also, Tekin et al. [62] obtained similar results, although with a reduction in olefinic compounds due to the use of the AlCl3 basic salt catalyst.
Figure 7 shows the disappearance of the characteristic peaks of the aromatics (795 and 694 cm−1) and the reduction in the intensity of the 728 cm−1 band in the spectrum of the HZ-PU (8%) zeolite product, which would indicate that this zeolite tends to produce compounds clearly from the alkane and alkene family.

4. Conclusions

It was possible to synthesize zeolites similar to commercial ZSM-5. Probably, they are found in a protonated form (as HZSM-5) due to the use of NH4Cl during the synthesis. The precursors considered were favorable for their high content of aluminosilicates, fundamental for the formation of zeolites, resulting in synthesis success, particularly for the IG and PO precursors, according to XRD and FTIR.
The SEM analysis indicates that the shapes obtained after the hydrothermal synthesis process are typical of the MFI structures for HZ-IG (ignimbrite), which has the greatest similarity to the ZSM-5 zeolite, followed by HZ-PO (pozzolana) and finally HZ-PU (pumice) with a higher amorphous index. According to the BET analysis, zeolites formed with ignimbrite and pozzolana precursors were the ones that obtained the highest specific surface area, and due to their pore size, they are considered mesopores and are very comparable to ZSM-5.
According to the results obtained from pyrolysis, regardless of whether it is thermal or catalytic, the production of solids was minimal. When using the catalyst, it was evidenced that wax production was lower than in thermal pyrolysis, except when working at 4% with HZ-PU and HZ-IG. With respect to the amount of zeolite, it was concluded that 8% of zeolite decreased the amount of wax and increased the production of liquid-gas, for all the zeolites used. The highest liquid production was 29.42% and 52.91% in gas with 8% of HZ-PU. However, these results are slightly insufficient in relation to the results achieved by ZSM-5 which had a minimum presence of waxes and higher percentages of liquid and gas, which indicates a better cracking of the polymer. The closest to this result is the HZ-PU and, in general, the use of these zeolites synthesized improved the production of liquids and gases.

Author Contributions

Conceptualization, S.H.F.-M., A.G.V.-H. and L.F.M.-D.L.C.; methodology, S.H.F.-M., A.G.V.-H. and L.F.M.-D.L.C.; software, S.H.F.-M., A.G.V.-H. and L.F.M.-D.L.C.; validation, J.A., R.C. and F.V.; formal analysis, J.A.; investigation, S.H.F.-M., A.G.V.-H. and L.F.M.-D.L.C.; resources, J.A., R.C., A.S.-V. and J.M.-Q.; data curation, R.C.; writing—original draft preparation, S.H.F.-M., A.G.V.-H. and L.F.M.-D.L.C.; writing—review and editing, J.A., R.C. and F.V.; visualization, R.C. and F.V.; supervision, J.A.; project administration, J.A.; funding acquisition, J.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research was financed by the Universidad Nacional de San Agustín de Arequipa-Perú with the project: “Obtención de Zeolitas a partir de Materiales Naturales de Origen Volcánico para Aplicación en Pirólisis Catalítica para el Reciclaje Químico Sostenible de Polímeros” (contract number: IBA-IB-39-2020-UNSA).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Acknowledgments

The authors thank the National University of San Agustín de Arequipa through Contract N°IBA-IB-39-2020-UNSA for its funding of this research.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.

References

  1. Ingemmet. ¿Por qué en Perú no son frecuentes las erupciones con flujos de lava? Ingemmet. Available online: https://www.gob.pe/institucion/ingemmet/noticias/494029-por-que-en-peru-no-son-frecuentes-las-erupciones-con-flujos-de-lava (accessed on 13 June 2023).
  2. Zeyad, A.M.; Almalki, A. Role of particle size of natural pozzolanic materials of volcanic pumice: Flow properties, strength, and permeability. Arab. J. Geosci. 2021, 14, 107. [Google Scholar] [CrossRef]
  3. Churata, R.; Almirón, J.; Vargas, M.; Tupayachy-Quispe, D.; Torres-Almirón, J.; Ortiz-Valdivia, Y.; Velasco, F. Study of Geopolymer Composites Based on Volcanic Ash, Fly Ash, Pozzolan, Metakaolin and Mining Tailing. Buildings 2022, 12, 1118. [Google Scholar] [CrossRef]
  4. Wu, T.-L.; Chen, Y.-H.; Hsu, W.-D. Phase transition pathway of hydrothermal zeolite synthesis. Phys. Chem. Miner. 2021, 48, 1. [Google Scholar] [CrossRef]
  5. Lima, R.C.; Bieseki, L.; Melguizo, P.V.; Pergher, S.B.C. Zeolite Eco-friendly Synthesis. In Engineering Materials; Springer Science and Business Media B.V.: Berlin/Heidelberg, Germany, 2019; pp. 65–91. [Google Scholar] [CrossRef]
  6. Research and Markets. Zeolite Market: Global Industry Trends, Share, Size, Growth, Opportunity and Forecast 2023–2028. Research and Markets. Available online: https://www.researchandmarkets.com/reports/5820578/zeolite-market-global-industry-trends-share?utm_code=fxhbx3&utm_exec=joca220prd#product--toc (accessed on 13 June 2023).
  7. Yoldi, M.; Fuentes-Ordoñez, E.; Korili, S.; Gil, A. Zeolite synthesis from industrial wastes. Microporous Mesoporous Mater. 2019, 287, 183–191. [Google Scholar] [CrossRef]
  8. Gao, S.; Peng, H.; Song, B.; Zhang, J.; Wu, W.; Vaughan, J.; Zardo, P.; Vogrin, J.; Tulloch, S.; Zhu, Z. Synthesis of zeolites from low-cost feeds and its sustainable environmental applications. J. Environ. Chem. Eng. 2023, 11, 108995. [Google Scholar] [CrossRef]
  9. Zaarour, M.; Dong, B.; Naydenova, I.; Retoux, R.; Mintova, S. Progress in zeolite synthesis promotes advanced applications. Microporous Mesoporous Mater. 2014, 189, 11–21. [Google Scholar] [CrossRef]
  10. Jain, R.; Mallette, A.J.; Rimer, J.D. Controlling Nucleation Pathways in Zeolite Crystallization: Seeding Conceptual Methodologies for Advanced Materials Design. J. Am. Chem. Soc. 2021, 143, 21446–21460. [Google Scholar] [CrossRef] [PubMed]
  11. Martínez, C.; Corma, A. Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes. Coord. Chem. Rev. 2011, 255, 1558–1580. [Google Scholar] [CrossRef]
  12. Kamimura, Y.; Iyoki, K.; Elangovan, S.P.; Itabashi, K.; Shimojima, A.; Okubo, T. OSDA-free synthesis of MTW-type zeolite from sodium aluminosilicate gels with zeolite beta seeds. Microporous Mesoporous Mater. 2012, 163, 282–290. [Google Scholar] [CrossRef]
  13. Williams, C.D. Application of Zeolites to Environmental Remediation. In Urban Pollution; John Wiley & Sons, Ltd.: Chichester, UK, 2018; pp. 249–258. [Google Scholar] [CrossRef]
  14. Scott, J.; Guang, D.; Naeramitmarnsuk, K.; Thabuot, M.; Amal, R. Zeolite synthesis from coal fly ash for the removal of lead ions from aqueous solution. J. Chem. Technol. Biotechnol. 2002, 77, 63–69. [Google Scholar] [CrossRef]
  15. Wen, J.; Dong, H.; Zeng, G. Application of zeolite in removing salinity/sodicity from wastewater: A review of mechanisms, challenges and opportunities. J. Clean. Prod. 2018, 197, 1435–1446. [Google Scholar] [CrossRef]
  16. Cataldo, E.; Salvi, L.; Paoli, F.; Fucile, M.; Masciandaro, G.; Manzi, D.; Masini, C.M.; Mattii, G.B. Application of Zeolites in Agriculture and Other Potential Uses: A Review. Agronomy 2021, 11, 1547. [Google Scholar] [CrossRef]
  17. Datta, J.; Kopczyńska, P. From polymer waste to potential main industrial products: Actual state of recycling and recovering. Crit. Rev. Environ. Sci. Technol. 2016, 46, 905–946. [Google Scholar] [CrossRef]
  18. Jones, H.; Saffar, F.; Koutsos, V.; Ray, D. Polyolefins and Polyethylene Terephthalate Package Wastes: Recycling and Use in Composites. Energies 2021, 14, 7306. [Google Scholar] [CrossRef]
  19. Almirón, J.; Huaman, A.V.; Mamani, S.F.; De La Cruz, L.M. A review of the interaction of natural and synthetic zeolites in the pyrolysis of plastics. In Proceedings of the 20th LACCEI International Multi-Conference for Engineering, Education and Technology: “Education, Research and Leadership in Post-Pandemic Engineering: Resilient, Inclusive and Sustainable Actions, Boca Raton, FL, USA, 18–22 July 2022; Latin American and Caribbean Consortium of Engineering Institutions: Arequipa, Peru, 2022. [Google Scholar] [CrossRef]
  20. Al-Asadi, M.; Miskolczi, N.; Eller, Z. Pyrolysis-gasification of wastes plastics for syngas production using metal modified zeolite catalysts under different ratio of nitrogen/oxygen. J. Clean. Prod. 2020, 271, 122186. [Google Scholar] [CrossRef]
  21. Miskolczi, N.; Juzsakova, T.; Sója, J. Preparation and application of metal loaded ZSM-5 and y-zeolite catalysts for thermo-catalytic pyrolysis of real end of life vehicle plastics waste. J. Energy Inst. 2019, 92, 118–127. [Google Scholar] [CrossRef]
  22. Zang, Y.; Wang, J.; Gu, J.; Qu, J.; Gao, F.; Li, M. Cost-effective synthesis of hierarchical HZSM-5 with a high Si/TPA+ ratio for enhanced catalytic cracking of polyethylene. J. Solid State Chem. 2020, 291, 121643. [Google Scholar] [CrossRef]
  23. Lima, R.B.; Neto, M.M.; Oliveira, D.S.; Santos, A.G.; Souza, L.D.; Caldeira, V.P. Obtainment of hierarchical ZSM-5 zeolites by alkaline treatment for the polyethylene catalytic cracking. Adv. Powder Technol. 2021, 32, 515–523. [Google Scholar] [CrossRef]
  24. Instituto Nacional de Estadistica Informatica (INEI). Industria del Plástico en el Perú. INEI. Available online: https://www.inei.gob.pe/media/MenuRecursivo/boletines/industria-plastico-peru.pdf (accessed on 4 April 2024).
  25. Santoso, A.; Sholikhah, A.; Sumari, S.; Asrori, M.R.; Wijaya, A.R.; Retnosari, R.; Rachman, I.B. Effect of Active Zeolite in the Pyrolysis of Polypropylene and Low Density Polyethylene Types of Plastic Waste. J. Renew. Mater. 2022, 10, 2781–2789. [Google Scholar] [CrossRef]
  26. Paula, T.P.; Marques, M.D.F.V.; Marques, M.R.D.C.; Oliveira, M.S.; Monteiro, S.N. Thermal and Catalytic Pyrolysis of Urban Plastic Waste: Modified Mordenite and ZSM-5 Zeolites. Chemistry 2022, 4, 297–315. [Google Scholar] [CrossRef]
  27. Wang, Y.; Huang, Q.; Zhou, Z.; Yang, J.; Qi, F.; Pan, Y. Online Study on the Pyrolysis of Polypropylene over the HZSM-5 Zeolite with Photoionization Time-of-Flight Mass Spectrometry. Energy Fuels 2015, 29, 1090–1098. [Google Scholar] [CrossRef]
  28. Vichaphund, S.; Aht-Ong, D.; Sricharoenchaikul, V.; Atong, D. Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste. Environ. Technol. 2014, 35, 2254–2261. [Google Scholar] [CrossRef] [PubMed]
  29. Soongprasit, K.; Sricharoenchaikul, V.; Atong, D. Pyrolysis of Millettia (Pongamia) pinnata waste for bio-oil production using a fly ash derived ZSM-5 catalyst. J. Anal. Appl. Pyrolysis 2019, 139, 239–249. [Google Scholar] [CrossRef]
  30. Gollakota, A.R.; Volli, V.; Munagapati, V.S.; Wen, J.-C.; Shu, C.-M. Synthesis of novel ZSM-22 zeolite from Taiwanese coal fly ash for the selective separation of Rhodamine 6G. J. Mater. Res. Technol. 2020, 9, 15381–15393. [Google Scholar] [CrossRef]
  31. Krisnandi, Y.K.; Yanti, F.M.; Murti, S.D.S. Synthesis of ZSM-5 zeolite from coal fly ash and rice husk: Characterization and application for partial oxidation of methane to methanol. IOP Conf. Ser. Mater. Sci. Eng. 2017, 188, 012031. [Google Scholar] [CrossRef]
  32. Wojciechowska, K.M.; Król, M.; Bajda, T.; Mozgawa, W. Sorption of Heavy Metal Cations on Mesoporous ZSM-5 and Mordenite Zeolites. Materials 2019, 12, 3271. [Google Scholar] [CrossRef] [PubMed]
  33. Frantz, T.S.; Ruiz, W.A.; da Rosa, C.A.; Mortola, V.B. Synthesis of ZSM-5 with high sodium content for CO2 adsorption. Microporous Mesoporous Mater. 2016, 222, 209–217. [Google Scholar] [CrossRef]
  34. Szostak, R. Molecular Sieves; Springer: Dordrecht, The Netherlands, 1989. [Google Scholar] [CrossRef]
  35. Dey, K.P.; Ghosh, S.; Naskar, M.K. Organic template-free synthesis of ZSM-5 zeolite particles using rice husk ash as silica source. Ceram. Int. 2013, 39, 2153–2157. [Google Scholar] [CrossRef]
  36. Kim, D.J.; Chung, H.S. Synthesis and characterization of ZSM-5 zeolite from serpentine. Appl. Clay Sci. 2003, 24, 69–77. [Google Scholar] [CrossRef]
  37. Liang, G.; Li, Y.; Yang, C.; Hu, X.; Li, Q.; Zhao, W. Synthesis of ZSM-5 zeolites from biomass power plant ash for removal of ionic dyes from aqueous solution: Equilibrium isotherm, kinetic and thermodynamic analysis. RSC Adv. 2021, 11, 22365–22375. [Google Scholar] [CrossRef]
  38. Luo, W.; Yang, X.; Wang, Z.; Huang, W.; Chen, J.; Jiang, W.; Wang, L.; Cheng, X.; Deng, Y.; Zhao, D. Synthesis of ZSM-5 aggregates made of zeolite nanocrystals through a simple solvent-free method. Microporous Mesoporous Mater. 2017, 243, 112–118. [Google Scholar] [CrossRef]
  39. Erofeev, V.I.; Adyaeva, L.V.; Ryabova, N.V. Effect of High-Temperature Steam Treatment of High-Silica Zeolites of the ZSM-5 Type on Their Acidity and Selectivity of Formation of Lower Olefins from Straight-Run Naphthas. Russ. J. Appl. Chem. 2003, 76, 95–98. [Google Scholar] [CrossRef]
  40. Klima, K.; Schollbach, K.; Brouwers, H.; Yu, Q. Enhancing the thermal performance of Class F fly ash-based geopolymer by sodalite. Constr. Build. Mater. 2022, 314, 125574. [Google Scholar] [CrossRef]
  41. Cruz Sánchez, E.; Torres, M.E.; Diaz, C.; Saito, F. Effects of grinding of the feldspar in the sintering using a planetary ball mill. J. Am. Acad. Dermatol. 2004, 152, 284–290. [Google Scholar] [CrossRef]
  42. Rajakrishnamoorthy, P.; Karthikeyan, D.; Saravanan, C. Emission reduction technique applied in SI engines exhaust by using zsm5 zeolite as catalysts synthesized from coal fly ash. Mater. Today Proc. 2020, 22, 499–506. [Google Scholar] [CrossRef]
  43. Verrecchia, G.; Cafiero, L.; de Caprariis, B.; Dell’Era, A.; Pettiti, I.; Tuffi, R.; Scarsella, M. Study of the parameters of zeolites synthesis from coal fly ash in order to optimize their CO2 adsorption. Fuel 2020, 276, 118041. [Google Scholar] [CrossRef]
  44. Almirón, J.; Vargas, M.; Tupayachy-Quispe, D.; Duquesne, S.; Roudet, F.; Silva-Vela, A. Influence of the Process of Synthesis of Zeolites from Volcanic Ash in Its Synergistic Action as a Flame-Retardant for Polypropylene Composites. Buildings 2021, 12, 24. [Google Scholar] [CrossRef]
  45. Ojha, K.; Pradhan, N.C.; Samanta, A.N. Zeolite from fly ash: Synthesis and characterization. Bull. Mater. Sci. 2004, 27, 555–564. [Google Scholar] [CrossRef]
  46. Ramadhani, A.N.; Abdullah, I.; Krisnandi, Y.K. Effect of Physicochemical Properties of Co and Mo Modified Natural Sourced Hierarchical ZSM-5 Zeolite Catalysts on Vanillin and Phenol Production from Diphenyl Ether. Bull. Chem. React. Eng. Catal. 2022, 17, 225–239. [Google Scholar] [CrossRef]
  47. Yu, D.; Chen, W.; Zhang, S.; Chilivery, R.; Li, F.; Lu, X.; Song, Y.; Fang, Y. Synthesis of HZSM-5 zeolites with excellent DME aromatization properties by orthogonal test. Phosphorus Sulfur Silicon Relat. Elem. 2020, 195, 464–473. [Google Scholar] [CrossRef]
  48. Rajaei, H.; Esmaeilzadeh, F.; Mowla, D. Synthesis and Characterization of Nano-Sized Pt/HZSM–5 Catalyst for Application in the Xylene Isomerization Process. Catal. Lett. 2022, 152, 139–150. [Google Scholar] [CrossRef]
  49. Shigemoto, N.; Hayashi, H.; Miyaura, K. Selective formation of Na-X zeolite from coal fly ash by fusion with sodium hydroxide prior to hydrothermal reaction. J. Mater. Sci. 1993, 28, 4781–4786. [Google Scholar] [CrossRef]
  50. Zhang, K.; Van Dyk, L.; He, D.; Deng, J.; Liu, S.; Zhao, H. Synthesis of zeolite from fly ash and its adsorption of phosphorus in wastewater. Green Process. Synth. 2021, 10, 349–360. [Google Scholar] [CrossRef]
  51. Murayama, N.; Yamamoto, H.; Shibata, J. Mechanism of zeolite synthesis from coal fly ash by alkali hydrothermal reaction. Int. J. Miner. Process. 2002, 64, 1–17. [Google Scholar] [CrossRef]
  52. Dai, S.; Tan, Y.; Yang, Y.; Zhu, L.; Liu, B.; Du, Y.; Cao, X. Organotemplate-free synthesis of Al-rich ZSM-35 and ZSM-22 zeolites with the addition of ZSM-57 zeolite seeds. CrystEngComm 2022, 24, 6987–6995. [Google Scholar] [CrossRef]
  53. Kocirik, M.; Kornatowski, J.; Masařík, V.; Novák, P.; Zikánová, A.; Maixner, J.; Kočřé, M. Investigation of sorption and transport of sorbate molecules in crystals of MFI structure type by iodine indicator technique. Microporous Mesoporous Mater. 1998, 23, 295–308. [Google Scholar] [CrossRef]
  54. Verboekend, D.; Chabaneix, A.M.; Thomas, K.; Gilson, J.-P.; Pérez-Ramírez, J. Mesoporous ZSM-22 zeolite obtained by desilication: Peculiarities associated with crystal morphology and aluminium distribution. CrystEngComm 2011, 13, 3408–3416. [Google Scholar] [CrossRef]
  55. Sousa, L.V.; Silva, A.O.; Silva, B.J.; Teixeira, C.M.; Arcanjo, A.P.; Frety, R.; Pacheco, J.G. Fast synthesis of ZSM-22 zeolite by the seed-assisted method of crystallization with methanol. Microporous Mesoporous Mater. 2017, 254, 192–200. [Google Scholar] [CrossRef]
  56. Munusamy, K.; Das, R.; Ghosh, S.; Kumar, S.K.; Pai, S.; Newalkar, B. Synthesis, characterization and hydroisomerization activity of ZSM-22/23 intergrowth zeolite. Microporous Mesoporous Mater. 2018, 266, 141–148. [Google Scholar] [CrossRef]
  57. Song, C.-Y.; Meng, J.-P.; Li, C.; Zeyaodong, P.; Liang, C.-H. Synthesis of ZSM-22/ZSM-23 intergrowth zeolite as the catalyst support for hydroisomerization of n-hexadecane. J. Fuel Chem. Technol. 2021, 49, 712–725. [Google Scholar] [CrossRef]
  58. Wong, S.L.; Armenise, S.; Nyakuma, B.B.; Bogush, A.; Towers, S.; Lee, C.H.; Wong, K.Y.; Lee, T.H.; Rebrov, E.; Muñoz, M. Plastic pyrolysis over HZSM-5 zeolite and fluid catalytic cracking catalyst under ultra-fast heating. J. Anal. Appl. Pyrolysis 2023, 169, 105793. [Google Scholar] [CrossRef]
  59. Zhou, N.; Dai, L.; Lv, Y.; Li, H.; Deng, W.; Guo, F.; Chen, P.; Lei, H.; Ruan, R. Catalytic pyrolysis of plastic wastes in a continuous microwave assisted pyrolysis system for fuel production. Chem. Eng. J. 2021, 418, 129412. [Google Scholar] [CrossRef]
  60. Panda, A.K.; Singh, R.K. Experimental Optimization of Process for the Thermo-catalytic Degradation of Waste Polypropylene to Liquid Fuel. Adv. Energy Eng. 2013, 1, 74–84. [Google Scholar]
  61. Miandad, R.; Barakat, M.; Aburiazaiza, A.S.; Rehan, M.; Ismail, I.; Nizami, A. Effect of plastic waste types on pyrolysis liquid oil. Int. Biodeterior. Biodegrad. 2017, 119, 239–252. [Google Scholar] [CrossRef]
  62. Tekin, K.; Akalın, M.K.; Kadı, Ç.; Karagöz, S. Catalytic degradation of waste polypropylene by pyrolysis. J. Energy Inst. 2012, 85, 150–155. [Google Scholar] [CrossRef]
Sustainability 16 05910 g001
Figure 1. FTIR of precursor materials (PO, IG, PU), synthesized zeolites (HZ-PO, HZ-IG, HZ-PU) and commercial ZSM-5.
Figure 1. FTIR of precursor materials (PO, IG, PU), synthesized zeolites (HZ-PO, HZ-IG, HZ-PU) and commercial ZSM-5.
Sustainability 16 05910 g001
Sustainability 16 05910 g002
Figure 2. FTIR transmittance spectra, in the range of band 1700–650 cm−1.
Figure 2. FTIR transmittance spectra, in the range of band 1700–650 cm−1.
Sustainability 16 05910 g002
Sustainability 16 05910 g003
Figure 3. XRD patterns of PO, IG and PU mineral precursors, and main crystalline phases found.
Figure 3. XRD patterns of PO, IG and PU mineral precursors, and main crystalline phases found.
Sustainability 16 05910 g003
Sustainability 16 05910 g004
Figure 4. XRD patterns of synthesized zeolites HZ-PO, HZ-IG y HZ-PU.
Figure 4. XRD patterns of synthesized zeolites HZ-PO, HZ-IG y HZ-PU.
Sustainability 16 05910 g004
Sustainability 16 05910 g005
Figure 5. SEM images of natural precursors: (A) pozzolana PO, (B) ignimbrite IG, (C) pumice, PU; synthesized zeolites (D) HZ-PO, (E) HZ-IG, (F) HZ-PU and (G) ZSM-5.
Figure 5. SEM images of natural precursors: (A) pozzolana PO, (B) ignimbrite IG, (C) pumice, PU; synthesized zeolites (D) HZ-PO, (E) HZ-IG, (F) HZ-PU and (G) ZSM-5.
Sustainability 16 05910 g005
Sustainability 16 05910 g006
Figure 6. Percentage of pyrolysis products by using synthesized zeolites, commercial zeolite and thermal pyrolysis.
Figure 6. Percentage of pyrolysis products by using synthesized zeolites, commercial zeolite and thermal pyrolysis.
Sustainability 16 05910 g006
Sustainability 16 05910 g007
Figure 7. FTIR transmittance spectra of pyrolysis oils from PP with 8% zeolites.
Figure 7. FTIR transmittance spectra of pyrolysis oils from PP with 8% zeolites.
Sustainability 16 05910 g007
Table 1. Chemical composition of pozzolan, pumice and ignimbrite.
Table 1. Chemical composition of pozzolan, pumice and ignimbrite.
OxidePO (%)PU (%)IG (%)
SiO277.9078.6067.60
Al2O315.1014.8020.30
K2O3.653.492.29
Fe2O31.331.354.43
CaO1.301.144.22
TiO20.250.230.60
Others0.470.390.56
Table 2. Characteristic FTIR bands of the synthesized zeolites, where T is Si or Al.
Table 2. Characteristic FTIR bands of the synthesized zeolites, where T is Si or Al.
Material/ZeoliteBending Stretching
H-O-H		Asymmetric Stretching
Si-O-T		Symmetric Stretching
Si-O-T
cm−1cm−1cm−1cm−1
PO-1007780724
IG-1007792729
PU-996-705
HZ-PO16291052785-
HZ-IG16261065793-
HZ-PU16301024787722
ZSM-516201075798-
Table 3. Textural properties of the synthesized zeolites.
Table 3. Textural properties of the synthesized zeolites.
ZeoliteSurface Specific AreaMicropore AreaMicropore VolumePore Diameter
m2/gm2/gcm3/gnm
HZ-PO2291440.0763.8
HZ-IG2051470.0764.8
HZ-PU1561010.0535.8
Table 4. Functional groups from FTIR spectra of PP pyrolysis oils.
Table 4. Functional groups from FTIR spectra of PP pyrolysis oils.
Bands (cm−1)BondFunctional Group
2957Asymmetric C-H stretching of CH3Methyl-alkanes
2925, 2924Asymmetric C-H stretching of CH3Methyl-alkanes
2872, 2871Symmetric stretching C-H of CH3Methyl-alkanes
1650Stretching C=CAlkenes
1458, 1457Asymmetric bending C-H of CH3; flexion in the plane C-H (scissoring) of CH2Methyl and methylene Alkanes
1378Symmetric C-H bending of CH3Methyl-alkanes
967, 966C-H bendingAlkenes
888Flexion out of the C-H planeAlkenes
795Flexion out of the C-H planeAromatics
728Bending in the plane C-H (rolling) of CH2Methyl-alkanes
694Flexion out of the C-H planeAromatics
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Valencia-Huaman, A.G.; Fuentes-Mamani, S.H.; Mamani-De La Cruz, L.F.; Velasco, F.; Churata, R.; Silva-Vela, A.; Mamani-Quispe, J.; Almirón, J. Obtaining Zeolites from Natural Materials of Volcanic Origin for Application in Catalytic Pyrolysis for the Sustainable Chemical Recycling of Polymers. Sustainability 2024, 16, 5910. https://doi.org/10.3390/su16145910

AMA Style

Valencia-Huaman AG, Fuentes-Mamani SH, Mamani-De La Cruz LF, Velasco F, Churata R, Silva-Vela A, Mamani-Quispe J, Almirón J. Obtaining Zeolites from Natural Materials of Volcanic Origin for Application in Catalytic Pyrolysis for the Sustainable Chemical Recycling of Polymers. Sustainability. 2024; 16(14):5910. https://doi.org/10.3390/su16145910

Chicago/Turabian Style

Valencia-Huaman, Angel Gabriel, Sandro Henry Fuentes-Mamani, Luis Fernando Mamani-De La Cruz, Francisco Velasco, Rossibel Churata, Alejandro Silva-Vela, Jose Mamani-Quispe, and Jonathan Almirón. 2024. "Obtaining Zeolites from Natural Materials of Volcanic Origin for Application in Catalytic Pyrolysis for the Sustainable Chemical Recycling of Polymers" Sustainability 16, no. 14: 5910. https://doi.org/10.3390/su16145910

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

Article Metrics

Back to TopTop