Optimization of Low-Temperature Catalytic Cracking of Polyolefin Waste in Open-Batch Reactors Using Zeolite Beta with Controlled Intrinsic Properties

Optimization of Low-Temperature Catalytic Cracking of Polyolefin Waste in Open-Batch Reactors Using Zeolite Beta with Controlled Intrinsic Properties | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Optimization of Low-Temperature Catalytic Cracking of Polyolefin Waste in Open-Batch Reactors Using Zeolite Beta with Controlled Intrinsic Properties Jong Hun Kang, Hankyeul Kang, Junghwa Yoon, Ki Hyuk Kang, Insoo Ro, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3999029/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Mar, 2025 Read the published version in Communications Engineering → Version 1 posted You are reading this latest preprint version Abstract Environmental problems are worsening due to the complexity in managing plastic waste. Chemical recycling emerges as a pivotal technology that can suppress additional carbon introduction into the carbon cycle and provide petroleum alternatives for current petrochemical processes, leading to value-added products. The utilization of zeolites can significantly reduce energy consumption by lowering the operation temperature required for pyrolysis. Here, we demonstrate low-temperature catalytic cracking of polyethylene (PE) utilizing an open-batch reactor configuration and *BEA-type zeolite catalysts, maximizing the liquid product selectivity. With the optimized open-batch setup and zeolite properties, high PE conversion (~ 80%) and liquid selectivity (~ 70%) were achieved at a low temperature of 330°C, effectively reducing the irreversible coke formation. We systematically explored the effects of aluminum (Al) site density and zeolite crystal size, revealing that zeolite crystal size is another critical factor determining the liquid production from PE due to its reactant shape selectivity. This work not only demonstrates that an effective combination and optimization of reactor and catalysts can enhance the overall catalytic activity but also offers insights into designing catalysis systems for the catalytic recycling of polyolefin wastes. Physical sciences/Engineering/Chemical engineering Physical sciences/Chemistry/Catalysis/Heterogeneous catalysis Physical sciences/Chemistry/Chemical engineering Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Plastics have emerged as pivotal materials that buttress current human civilizations, assuming an irreplaceable role in maintaining human well-being. Consequently, the production of plastics has been experiencing significant global growth, primarily driven by the versatility and extensive applicability of polymer-based products across various sectors of industry, encompassing automotive, construction, electronics, aerospace, and packaging. 1 As a result, in 2015, an estimated 6,300 MT of plastic waste had been generated, posing a formidable environmental challenge these days. 2 – 4 Additionally, the utilization and subsequent disposal of single-use plastics contribute to the prospection of additional carbons for make-up inputs, primarily from oil reserves. Within this context, plastic recycling assumes significant importance, as it serves not only to mitigate immediate environmental threats but also plays a crucial role in achieving carbon neutrality by curbing additional fossils into the carbon cycle. Chemical recycling, comprising both conventional and innovative technologies aimed at converting plastic waste into value-added chemicals, encompassing monomers, aromatics, and olefins, has attracted substantial interest from the scientific and engineering communities. This interest majorly stems from its capability to leverage existing chemical processes, keeping the carbon quantity in circulation. 5 – 7 Polyolefin wastes, including polyethylene (PE) and polypropylene (PP), have gained significant attention in the field of chemical recycling of plastic waste due to their prevalence, comprising over 50% of the global plastic waste stream. 8 The polyolefin polymer backbone comprises of C-C bonds, necessitating controlled cleavage to yield liquid hydrocarbons suitable for use as feedstocks in downstream processes. These subsequent processes may encompass traditional processes, such as the fluidized catalytic cracking preceded by hydrotreatment, as well as innovative technologies such as the plasma gasification, which yields ethylene and acetylene under arc discharge. 9 In this context, it is essential to prioritize the optimization of liquid hydrocarbon yield with controlled selectivity distribution to meet the downstream process requirements, thereby enhancing overall operational efficiency. Many technologies have been developed and utilized for the conversion of polyolefin waste into a spectrum of hydrocarbons, spanning from light olefins to wax. 10 – 12 Pyrolysis, conducted at high temperatures ranging from 450–600°C in an inert atmosphere, entails thermal cleavage of the main backbone of polyolefins. 13 Although the pyrolysis process has the highest technological maturity, it presents several challenges, including high energy consumption resulting from high temperature conditions. 14 – 16 To tackle these challenges, hydrogenolysis 17 – 20 and alkane tandem metathesis 21 , 22 at low temperature (200–250°C) have been suggested and widely studied as alternative processes. However, the cost viability of these approaches is hindered by the requirement for high-pressure hydrogen and/or the utilization of platinum group metal catalysts like Pt or Ru. Catalytic cracking process efficiently decomposes polyolefins at lower temperatures than pyrolysis, employing a solid acid catalyst. Extensive research has focused on reducing energy consumption and carbon deposition in the reactor. 23 – 27 Zeolites, common microporous solid acid catalysts, reduce the activation energy necessary for breaking C-C bond chains of polyolefins through mechanisms such as the ß-scission and protonolysis over their Brønsted acid sites. 28 The final distribution of products is primarily determined by the shape selectivity of the micropore structures of zeolites. 28 – 31 Among various commercialized zeolites, zeolite beta, with 12-membered-ring (12MR) micropores measuring 7–8 Å in pore opening and interconnected channels in three dimensions, is recognized for its high selectivity in producing liquid products (C 5–30 ) in the catalytic cracking of polyolefin. 32 – 34 Furthermore, zeolite beta serves as an ideal platform for investigating the correlation between catalytic performance and intrinsic properties of zeolites, including crystal sizes and Si/Al ratios, as modification of these properties through hydrothermal synthesis has extensively studied. 35 , 36 While zeolite have been commonly considered as capable of reducing the operation temperature of pyrolysis under non-hydrogen conditions, the catalytic cracking of polyolefins using zeolites has primarily been investigated within a temperature range exceeding 380°C. 8 , 33 , 37 , 38 In this study, we demonstrate the potential to further reduce the operating temperature of catalytic cracking of PE (namely, 330°C) while maintaining polyolefin conversion above 80% and liquid selectivity exceeding 70%, through appropriate control of the intrinsic properties of zeolite beta, in conjunction with the optimization of reactor design and associated process parameters. A series of zeolite beta catalyst samples were synthesized, with control over parameters including Si/Al ratio and crystal size, specifically the external surface area. Under the optimized condition at 330°C, the correlation between catalytic performance and intrinsic properties of zeolites were established. Figure 1 presents schematic illustrations that encapsulate the central concept of this study. Results and Discussions Catalytic cracking process optimization The structure and operation modes of batch reactors containing a PE/catalyst slurry during catalytic contact are crucial for improving the conversion and product distribution in low-temperature PE catalytic cracking. The reactor used for this work could operate in either closed-batch or open-batch mode by simply closing or opening the downstream valve that connects to the condenser/collector units as shown in Fig. 1 (a) and Supplementary Fig. 3. The primary purpose of catalytic decomposition of PE is to obtain liquid hydrocarbon products suitable for further processing in downstream processes. Typically, an improved liquid selectivity can be achieved by minimizing excessive contact between zeolite and hydrocarbon species (Fig. 1 (b)). This approach helps to prevent irreversible coke formation and evolution of gas species from over-cracking. Indeed, employing a selected *BEA-type zeolite catalyst (S-BEA-30, see below for the sample information), an open-batch configuration at 330°C resulted in higher conversion and liquid selectivity (45.1% and 62.3%, respectively) than the conventional closed-batch configuration (38.3% and 44.9%, respectively), by allowing the evaporated products to escape the reactor (Fig. 2 (a)). The over-cracking, which produces uncrackable solid phase that deactivates the catalysis, is significantly reduced in an open-batch configuration compared to a closed-batch configuration as shown in Supplementary Fig. 4. The inert-gas flow rate is a crucial parameter influencing the conversion and liquid selectivity in the open-batch catalytic cracking of PE. Figure 2 (b) demonstrates that increasing the inert-gas flow rate shifts the selectivity distribution towards heavier products, suggesting fewer catalytic scissions in PE chains due to reduced contact time. The PE conversion increases monotonously with the inert-gas flow rate, while liquid selectivity showed an optimum at 10 mL/min in our reactor setup, which was adopted as the standard reaction condition for subsequent experiments. These results highlight the significance of the reactor design and operation modes in the catalytic PE decomposition into liquid hydrocarbons. Obviously, temperature is a key parameter affecting the rate of catalytic scissions of the main backbone of PE chains. At the optimized inert-gas flow rate of 10 mL/min with the selected zeolite catalyst (S-BEA-30), the conversion of PE is dramatically influenced by the operation temperature as depicted in Fig. 2 (c). A high conversion of 98.3% was observed at 390°C, near the typical temperature range of the conventional pyrolysis process. Conversely, at the low limit of 260°C, the conversion was low, under 20%, even with the zeolite catalyst. The selectivity towards light C 5 and C 6 liquid hydrocarbons was noticeably low at 260°C, implying sluggish scission of C-C backbones of linear hydrocarbons (Fig. 2 (d)). In this work, we evaluated various zeolite catalysts at 330°C, achieving acceptably high conversion and high liquid selectivity, highlighting disparities among samples. The use of zeolites greatly enhances the conversion of PE at low temperatures by accelerating C-C bond scission, catalyzed by Brønsted acid sites that promote the carbenium or carbonium mechanisms. 28 In absence of zeolites, just a 0.2% PE conversion was observed at 330°C. To evaluate the effect of zeolite topologies, several commercially available zeolites, including ZSM-5 (MFI), zeolite beta (*BEA), and zeolite Y (FAU) were examined (Fig. 2 (e)). These zeolites achieved PE conversions ranging from 20–80% at the same temperature. Details on the tested commercial zeolites are provided in the Supplementary Information. All zeolites demonstrated significant isomerization, as indicated by the complexity of the resulting gas chromatograph (GC) profiles (see Supplementary Fig. 5). Among the tested commercial zeolites, ZSM-5 having micropores limited by 10MR pore openings, exhibited the highest conversion, but its liquid selectivity was lower than that of zeolite beta due to its high gas selectivity as depicted in Fig. 2 (f), which originated from its narrow pore system. ZSM-5 also tended to produce lighter liquid products than the other two frameworks (Fig. 2 (g)). The GC-MS analysis revealed that it produced aromatic compounds as major products due to the 10MR shape selectivity of the MFI framework (Supplementary Fig. 5). Conversely, the zeolite Y samples of 12MR pore openings showed relatively low PE conversions, potentially due to their weak acid site strength. 39 The zeolite beta sample of 12MR pore openings achieved a PE conversion comparable to ZSM-5 with the highest liquid selectivity, and aliphatic compounds were detected as major products. In this work, the effects of the intrinsic properties of zeolite on the *BEA framework were investigated. The synthesis of *BEA-type zeolites, which has been extensively studied for decades, 35 , 40 , 41 offers great synthetic flexibility in terms of Si/Al ratios and crystal sizes. Intrinsic properties-controlled beta zeolite catalytic cracking of LDPE The catalytic cracking of PE using the prepared *BEA-type zeolites was tested in an open-batch configuration under optimal conditions (10 mL N 2 /min, 330°C, 2 hours) as previously discussed. Figures 4 (a–c) show the conversion and liquid selectivity, achieved with the *BEA-type zeolites listed in Table 1. The framework Al sites primarily act as Brønsted acid sites in zeolites, serving as active sites for the catalytic cracking of long-chain hydrocarbons. 28 Thus, the decrease in Si/Al ratios led to an increase in the PE conversion across all sample series, indicating enhanced apparent catalytic activity. Crystal size also played a crucial role in the PE conversion. The S-series samples, with higher specific external surface area values (Table 1), showed higher PE conversions than the L-series samples. A similar trend was observed in liquid selectivity (Fig. 4 (b)). Al sites can be located within either the micropores or external surfaces of the zeolite samples. The catalytic conversion of PE over *BEA-type zeolites may occur in two steps: bulky molecule scission at the external surface acid sites, followed by additional scission of smaller molecules within the micropores. We think that the molecular weight distribution of liquid products primarily depends on the spatial distributions of these acid sites as shown in Fig. 4 (e). The S-BEA-10 sample having the most Al sites and the highest external surface area showed a high PE conversion (~ 80%) and liquid selectivity (~ 70%) at a low temperature of 330°C. This result offers experimental evidence that reducing crystal size also significantly enhances the PE conversion and liquid selectivity by facilitating the external scission process of polymer chains. Further analysis on the conversion and liquid selectivity is provided in the Supplementary Information. The simulated distillation (SIMDIS) results confirmed that over 99% of the liquid portion comprises hydrocarbons in the range from C 5 to C 30 (Supplementary Fig. 10 and Table 3). Figure 4 (d) illustrates the hydrocarbon distribution in liquid products from the catalytic cracking of PE over L-BEA-10, M-BEA-10, and S-BEA-10, which have similar Si/Al ratios but vary in crystal sizes. L-BEA-10 and M-BEA-10 predominantly yielded hydrocarbons in the gasoline (C 5–10 ) range, whereas S-BEA-10 yielded heavier products under the same reaction conditions. Considering the total number of Al sites is similar across the three samples, it suggests that L-BEA-10 and M-BEA-10 have more micropore Al sites than S-BEA-10, providing a greater extents of secondary scission to lighter products. This serves as an example of the reactant shape selectivity. The spent catalysts were recovered as entangled chunks mixed with residues, including deposited coke species. The SIMDIS analysis of the Soxhlet extract, using toluene as the solvent, revealed a minimal composition of remaining product-range (C 5 –C 30 ) hydrocarbons in the solid phase (Supplementary Fig. 9 and Table 3). The spent catalysts should be recoverable and reusable from the remaining solid phase. However, mechanical separation of inorganic catalyst components from the mixture was unsuccessful due to the polymeric organic components remaining in the solid phase, showing a sturdy texture at room temperature. To assess catalyst reusability, a new PE feed of the same amount was directly added to the spent mixture for a second run. The conversion and liquid selectivity in the second run decreased compared to the first, from 78–67% and from 68–54%, respectively (Fig. 5 (a)). However, the product distribution of the liquid product within the range from C 5 to C 15 remained almost unchanged, as shown in Fig. 5 (b), indicating that coke-induced deactivation primarily influenced the external surfaces of zeolite rather than the micropores. The zeolite catalysts could be separated by removing the residue through air calcination. The regenerated catalyst was found to have physical properties very similar to those of the virgin catalyst, as confirmed by PXRD, SEM, EDS, and BET analyses (Supplementary Fig. 12). Consequently, in the catalytic cracking of PE using the regenerated catalyst, both the conversion and liquid selectivity were almost identical (Figs. 5 (c–d)). Finally, the optimized 330°C open-batch reaction conditions were applied to an actual post-consumer PE waste sample collected from a local recycling center, and it was confirmed that the resulting PE conversion and liquid selectivity were similar to those observed with the virgin PE model feed, as illustrated in Supplementary Fig. 13. Conventionally, the catalytic cracking of polyolefins using zeolite catalysts have adopted operation temperatures higher than 380°C. 33 , 43 , 44 This work demonstrates the temperature can be greatly reduced to 330°C while maintaining high PE conversion and liquid selectivity, provided the reactor configuration and catalysts are adequately optimized. The open-batch configuration effectively prevents over-cracking or excess coke formation by properly regulating the contact between the feed molecules and the zeolites, removing the distillates to the gas phase. Proper selection of inert-gas flow rate, which further regulates the contact time, can further enhance the PE conversion and liquid selectivity. Among the tested commercial zeolites, zeolite beta having the *BEA topology exhibited excellent acid site strength, ensuring high conversion of PE even at low temperature and an adequate shape selectivity towards aliphatic liquid products. Along with the Al content of zeolites, the crystal size was confirmed as a crucial factor determining the PE conversion and liquid phase selectivity. Reducing the crystal size ensures high liquid selectivity regardless of the Al content by enhancing the chain scission on the external surfaces of zeolites. This work not only highlights the potential for the low-temperature catalytic cracking of PE using zeolite catalysts but also provides insights into other plastic waste chemical recycling technologies in terms of selection of catalysts. 45 Methods Synthesis of *BEA-type zeolites All *BEA-type zeolites presented in this work were synthesized using conventional hydrothermal methods, recipes that are modifications of the previously reported methods in the literature. 36 , 40 , 41 Initially, Al sources, OSDA(TEAOH), mineralizers, and water were mixed to achieve a desired gel composition in 40 mL PTFE liners. Subsequently, Si sources were added, ensuring complete dispersion and homogenization by subsequent stirring. The general gel composition can described as 1.0 SiO 2 : x Al : y TEAOH : z (NH 4 F or NaOH) : w H 2 O. x determines the Al content, while y , z , and w depend on the different sample series yielding different crystal sizes. Additional aging steps can be added depending on the sample series. The PTFE liners charged with gels were clad in steel autoclaves and transferred to a convection oven preheated to the desired temperature, which could be rotating or static. The progress of crystallization was tracked by analyzing PXRD patterns of aliquots collected every 3–7 days. Following crystallization, the products were thoroughly rinsed with distilled water and acetone and calcined at 580°C for 6 hours. The resultant *BEA-type zeolites were then converted into their H-forms through ion exchange with ammonium nitrate (NH 4 NO 3 ) and subsequent calcination at 580°C for 6 hours. The details of the preparations of the three series of samples (L-, M-, and S-series), including specified gel compositions, are provided in the Supplementary Information, together with the characterizations of the resulting zeolites. Open-batch catalytic cracking process of PE Polyolefin catalytic cracking was conducted using open-batch reactive distillation setup in a stirring batch reactor (CheMReSys, R-201) with custom modifications to allow an inert gas flow. Initially, 1 g of zeolite catalyst and 10 g of model feed PE (LDPE, melt index 25 g/10 min at 190°C/2.16 kg, Sigma-Aldrich) were placed in a 75 mL stainless steel liner and sealed within the stirring reactor. The line connected to the reactor was heated to 330°C during the operation with heating tapes to minimize condensation and residue within tubing and fitting. The reaction was performed for 2 hours at a bulk temperature of 330°C with stirring at 200 rpm. Simultaneously, inert gas (N 2 ) flowed at a desired rate. The liquid product was collected via a condensation device connected to a cold constant-temperature circulation column set at -15°C, comprising two stages to minimize the process loss. The gaseous product was collected in a gas sampling bag connected to the end of the reactive distillation setup and analyzed using a GC-FID. The details of quantification methods and reactor structure/operation modes are provided in the Supplementary Information. Characterizations Powder X-ray diffraction (XRD) patterns were obtained with a SMARTLAB instrument (Rigaku, Japan). Scanning electron microscopy (SEM) images and elemental compositions of the zeolites were analyzed using a JSM-7800F Prime microscope equipped with an energy-dispersive spectroscopy (EDS) unit. N 2 physisorption (77 K) isotherms were measured using a BELSORP MINI X sorption analyzer. Prior to measurements, samples underwent a 3-hour degassing step at 300°C using a BELPREP VAC II instrument (MicrotracBEL, Japan). Raman spectra of solid samples were recorded with a DXR2xi instrument (Thermo Fisher Scientific, USA). The selectivity distributions of liquid products were determined using a ChroZen gas chromatography-flame ionization detector (GC-FID, Youngin, Korea), and product identification was carried out with a TSQ 3000 Evo gas chromatography-mass spectrometry (GC-MS) system (Thermo Fisher Scientific, USA) based on the NIST library. Declarations Acknowledgements This research was supported by Korea Institute of Industrial Technology (KITECH) through the Korea Environmental Industry & Technology Institute (KEITI) funded by the Ministry of Environment (ARQ202209004001). Author contributions H.K. contributed to zeolite synthesis, catalytic cracking, data collection, and drafting the original manuscript. J.Y. contributed to zeolite synthesis, reactor design, and data collection. K.H.K. contributed to SIMDIS data collection. K.H.K., I.R., and S.J. contributed to developing ideas for experimental designs. S.J. contributed to funding acquisition, project administration, and procuring post-consumer PE waste. J.H.K. contributed to reactor design, supervision, and both writing and reviewing the manuscript. Competing interests The authors declare no competing financial interest. Supplementary information Commercial zeolite information, details of reactor operation modes, details of zeolite synthesis, characterization of zeolites, and supplementary analyses on catalytic reactions. References Chang, C.-F. & Rangarajan, S. Machine Learning and Informatics Based Elucidation of Reaction Pathways for Upcycling Model Polyolefin to Aromatics. J. Phys. Chem. A 127, 2958–2966 (2023). Cressey, D. Bottles, bags, ropes and toothbrushes: the struggle to track ocean plastics. Nature 536, 263–265 (2016). Geyer, R., Jambeck, J. R. & Law, K. L. Production, use, and fate of all plastics ever made. Sci. Adv. 3, e1700782 (2017). Joshi, C., Browning, S. & Seay, J. Combating plastic waste via Trash to Tank. Nat. 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Role of Bifunctional Ru/Acid Catalysts in the Selective Hydrocracking of Polyethylene and Polypropylene Waste to Liquid Hydrocarbons. ACS Catal. 12, 13969–13979 (2022). Tables Table 1 . Physical properties of the intrinsic properties-controlled beta zeolites. Entry Sample Crystal size (nm) Si/Al † S BET (m 2 /g) ‡ V mic (cc/g) ‡ S Ext (m 2 /g) ‡ V meso (cc/g) ‡ 1 L-BEA-10 650 9.6 575 0.239 88 0.206 2 L-BEA-15 950 16.8 495 0.216 48 0.122 3 L-BEA-20 1510 21.0 472 0.218 24 0.047 4 L-BEA-30 1710 26.1 424 0.186 43 0.053 5 M-BEA-10 170 8.7 589 0.220 138 0.728 6 M-BEA-20 130 19.7 569 0.253 48 0.601 7 S-BEA-10 30 11.4 634 0.226 192 0.971 8 S-BEA-20 80 18.9 612 0.263 99 0.644 9 S-BEA-30 110 28.7 616 0.264 96 0.650 10 S-BEA-50 140 48.1 584 0.253 87 0.596 † Characterized by EDS; ‡ Characterized based on the N 2 adsorption isotherms obtained at 77 K. Micropore volumes (V mic ) were estimated based on the V-t method. Mesoporous volumes (V meso ) were estimated based on the Barrett-Joyner-Halenda (BJH) model. Additional Declarations There is NO Competing Interest. Supplementary Files HKangetalConsumerWasteValorSI.docx Cite Share Download PDF Status: Published Journal Publication published 24 Mar, 2025 Read the published version in Communications Engineering → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3999029","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":279255803,"identity":"e2947088-b29c-45f3-9542-e3fa1db2b20c","order_by":0,"name":"Jong Hun Kang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7UlEQVRIiWNgGAWjYBACxgYGBmYgbQBiP4AKMhOthdmAKC0wFSDVbBJEaWFu7z38urDtjjH/7PZrlT93HGbgbz/AbFyBz2E959KsZ7Y9M5O4c6bsNu+ZwwwSZxKYE8/g0zIjx8yYt+2wDcONnLTbjG2HGRhuMDAfbCBGizxQS+FPoBZ5IrQYPwZqMTO4kX6MAchgMABqScSrpeeMGTPPucPGhjdymKV529J5DM8kNhvi02LY3mP8mafssOG8G+kPP/5ss5aTO374sCReLQ3w6OABxyQPJHrxAHlg1HyAMNkf4FU5CkbBKBgFIxcAALy+Tjv37tp+AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-4197-9070","institution":"Seoul National University","correspondingAuthor":true,"prefix":"","firstName":"Jong","middleName":"Hun","lastName":"Kang","suffix":""},{"id":279255804,"identity":"4b46b840-40e1-4819-90c4-935ac9e8a841","order_by":1,"name":"Hankyeul Kang","email":"","orcid":"https://orcid.org/0009-0006-4097-1516","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Hankyeul","middleName":"","lastName":"Kang","suffix":""},{"id":279255805,"identity":"1f3c5af4-930c-4e79-aa2f-43addff9f33b","order_by":2,"name":"Junghwa Yoon","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Junghwa","middleName":"","lastName":"Yoon","suffix":""},{"id":279255806,"identity":"909ca192-a47c-4551-8731-0557b3e3de3f","order_by":3,"name":"Ki Hyuk Kang","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Ki","middleName":"Hyuk","lastName":"Kang","suffix":""},{"id":279255807,"identity":"e42c72bc-93d2-4443-a9d0-bd0d652f60db","order_by":4,"name":"Insoo Ro","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Insoo","middleName":"","lastName":"Ro","suffix":""},{"id":279255808,"identity":"8da97e33-b503-4913-843b-363b02833d36","order_by":5,"name":"Soohwa Jeong","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Soohwa","middleName":"","lastName":"Jeong","suffix":""}],"badges":[],"createdAt":"2024-02-29 08:25:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3999029/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3999029/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s44172-025-00392-8","type":"published","date":"2025-03-24T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":52794604,"identity":"a48d20b1-1f1f-4822-b4ab-97811a82d5e5","added_by":"auto","created_at":"2024-03-15 21:01:10","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2312607,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic summary of the reactor design and mechanism in this work\u003c/strong\u003e: (a) *BEA-type zeolites with varying Al contents and crystal sizes in an open-batch reactor setup and (b) the open-batch configuration with an inert gas flow facilitating liquid product recovery and preventing over-cracking that reduces liquid selectivity through reactive distillation.\u003c/p\u003e","description":"","filename":"HKangetalConsumerWasteValorFigure1CMYK.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3999029/v1/7fb12a8a9c5be595b070da8d.jpg"},{"id":52794608,"identity":"ffdf98c5-61ba-4b57-b292-adaa0701443e","added_by":"auto","created_at":"2024-03-15 21:01:11","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":3413198,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptimization of the open-batch reactor configuration and types of zeolite catalysts for the low-temperature open-batch catalytic cracking of PE:\u003c/strong\u003e (a) PE conversion, liquid selectivity, and (b) liquid product selectivity distributions with varied open-batch reactor configurations. (c) PE conversion, liquid selectivity, and (d) liquid product selectivity distributions with varied operation temperatures. (e) structures of commercial zeolites demonstrated in this work. (f) PE conversion, liquid selectivity, and (g) liquid product selectivity distributions from various commercial zeolites.\u003c/p\u003e","description":"","filename":"HKangetalConsumerWasteValorFigure2CMYK.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3999029/v1/4ca9bbcfc46357d66bfcffef.jpg"},{"id":52794610,"identity":"d9e184cb-f695-47d1-8bf4-6e15e8d20abd","added_by":"auto","created_at":"2024-03-15 21:01:13","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1215459,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eRelation between the Al content and crystal size of the resulting *BEA-type zeolite. (\u003c/strong\u003ea) Schematic summary of intrinsic properties-controlled beta zeolite, scanning electron microscope images of synthesized beta zeolite with Si/Al 10: (b) L-BEA-10, (c) M-BEA-10, and (d) S-BEA-10.\u003c/p\u003e","description":"","filename":"HKangetalConsumerWasteValorFigure3CMYK.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3999029/v1/55467a0628aa9f5375eb803a.jpg"},{"id":52794606,"identity":"c9e7fdfd-1e95-4bb1-ba18-b14025758ea4","added_by":"auto","created_at":"2024-03-15 21:01:11","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1980892,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIntrinsic properties-controlled beta zeolite catalytic cracking of LDPE at 330 °C, 2 h, 10 ml N\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e/min:\u003c/strong\u003e (a) Conversion, (b) liquid selectivity, (c) liquid selectivity by conversion, (d) hydrocarbon distribution in liquid products, and (e) schematic description for the relation between acid site distribution and liquid product molecular weight.\u003c/p\u003e","description":"","filename":"HKangetalConsumerWasteValorFigure4CMYK.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3999029/v1/6fe75a2536fb42127949d13b.jpg"},{"id":52794607,"identity":"29a9edac-e7a1-4a9a-a3bc-bfa5d543e3f9","added_by":"auto","created_at":"2024-03-15 21:01:11","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1654406,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCatalytic cracking to evaluate reusability and regenerability of deactivated zeolite beta (S-BEA-10) at 330 °C, 2 h, 10 ml N\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e/min. Continuous secondary reaction compared to the first reaction:\u003c/strong\u003e (a) conversion and liquid selectivity, (b) hydrocarbon distribution in liquid products; Regenerated beta zeolite catalytic cracking compared to the virgin beta zeolite: (c) conversion, (d) hydrocarbon distribution in liquid products.\u003c/p\u003e","description":"","filename":"HKangetalConsumerWasteValorFigure5CMYK.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3999029/v1/cb4e30168b32d387e8d6cb7a.jpg"},{"id":79159872,"identity":"4e726e67-b408-468e-8ec5-ee22025607fc","added_by":"auto","created_at":"2025-03-25 07:10:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":15594613,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3999029/v1/3bfcd444-f773-4afd-bc88-0e4f9b102636.pdf"},{"id":52794609,"identity":"a544b5aa-8d1f-4be4-ad07-079e8e4add10","added_by":"auto","created_at":"2024-03-15 21:01:11","extension":"docx","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":5086851,"visible":true,"origin":"","legend":"","description":"","filename":"HKangetalConsumerWasteValorSI.docx","url":"https://assets-eu.researchsquare.com/files/rs-3999029/v1/d1cd39afcfa6228a7449a885.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Optimization of Low-Temperature Catalytic Cracking of Polyolefin Waste in Open-Batch Reactors Using Zeolite Beta with Controlled Intrinsic Properties","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePlastics have emerged as pivotal materials that buttress current human civilizations, assuming an irreplaceable role in maintaining human well-being. Consequently, the production of plastics has been experiencing significant global growth, primarily driven by the versatility and extensive applicability of polymer-based products across various sectors of industry, encompassing automotive, construction, electronics, aerospace, and packaging.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e As a result, in 2015, an estimated 6,300 MT of plastic waste had been generated, posing a formidable environmental challenge these days.\u003csup\u003e\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e Additionally, the utilization and subsequent disposal of single-use plastics contribute to the prospection of additional carbons for make-up inputs, primarily from oil reserves. Within this context, plastic recycling assumes significant importance, as it serves not only to mitigate immediate environmental threats but also plays a crucial role in achieving carbon neutrality by curbing additional fossils into the carbon cycle. Chemical recycling, comprising both conventional and innovative technologies aimed at converting plastic waste into value-added chemicals, encompassing monomers, aromatics, and olefins, has attracted substantial interest from the scientific and engineering communities. This interest majorly stems from its capability to leverage existing chemical processes, keeping the carbon quantity in circulation.\u003csup\u003e\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003ePolyolefin wastes, including polyethylene (PE) and polypropylene (PP), have gained significant attention in the field of chemical recycling of plastic waste due to their prevalence, comprising over 50% of the global plastic waste stream.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e The polyolefin polymer backbone comprises of C-C bonds, necessitating controlled cleavage to yield liquid hydrocarbons suitable for use as feedstocks in downstream processes. These subsequent processes may encompass traditional processes, such as the fluidized catalytic cracking preceded by hydrotreatment, as well as innovative technologies such as the plasma gasification, which yields ethylene and acetylene under arc discharge.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e In this context, it is essential to prioritize the optimization of liquid hydrocarbon yield with controlled selectivity distribution to meet the downstream process requirements, thereby enhancing overall operational efficiency. Many technologies have been developed and utilized for the conversion of polyolefin waste into a spectrum of hydrocarbons, spanning from light olefins to wax.\u003csup\u003e\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e Pyrolysis, conducted at high temperatures ranging from 450\u0026ndash;600\u0026deg;C in an inert atmosphere, entails thermal cleavage of the main backbone of polyolefins.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e Although the pyrolysis process has the highest technological maturity, it presents several challenges, including high energy consumption resulting from high temperature conditions.\u003csup\u003e\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e To tackle these challenges, hydrogenolysis\u003csup\u003e\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e and alkane tandem metathesis\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e at low temperature (200\u0026ndash;250\u0026deg;C) have been suggested and widely studied as alternative processes. However, the cost viability of these approaches is hindered by the requirement for high-pressure hydrogen and/or the utilization of platinum group metal catalysts like Pt or Ru.\u003c/p\u003e \u003cp\u003eCatalytic cracking process efficiently decomposes polyolefins at lower temperatures than pyrolysis, employing a solid acid catalyst. Extensive research has focused on reducing energy consumption and carbon deposition in the reactor.\u003csup\u003e\u003cspan additionalcitationids=\"CR24 CR25 CR26\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e Zeolites, common microporous solid acid catalysts, reduce the activation energy necessary for breaking C-C bond chains of polyolefins through mechanisms such as the \u0026szlig;-scission and protonolysis over their Br\u0026oslash;nsted acid sites.\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e The final distribution of products is primarily determined by the shape selectivity of the micropore structures of zeolites.\u003csup\u003e\u003cspan additionalcitationids=\"CR29 CR30\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e Among various commercialized zeolites, zeolite beta, with 12-membered-ring (12MR) micropores measuring 7\u0026ndash;8 \u0026Aring; in pore opening and interconnected channels in three dimensions, is recognized for its high selectivity in producing liquid products (C\u003csub\u003e5\u0026ndash;30\u003c/sub\u003e) in the catalytic cracking of polyolefin.\u003csup\u003e\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e Furthermore, zeolite beta serves as an ideal platform for investigating the correlation between catalytic performance and intrinsic properties of zeolites, including crystal sizes and Si/Al ratios, as modification of these properties through hydrothermal synthesis has extensively studied.\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eWhile zeolite have been commonly considered as capable of reducing the operation temperature of pyrolysis under non-hydrogen conditions, the catalytic cracking of polyolefins using zeolites has primarily been investigated within a temperature range exceeding 380\u0026deg;C.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e In this study, we demonstrate the potential to further reduce the operating temperature of catalytic cracking of PE (namely, 330\u0026deg;C) while maintaining polyolefin conversion above 80% and liquid selectivity exceeding 70%, through appropriate control of the intrinsic properties of zeolite beta, in conjunction with the optimization of reactor design and associated process parameters. A series of zeolite beta catalyst samples were synthesized, with control over parameters including Si/Al ratio and crystal size, specifically the external surface area. Under the optimized condition at 330\u0026deg;C, the correlation between catalytic performance and intrinsic properties of zeolites were established. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents schematic illustrations that encapsulate the central concept of this study.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results and Discussions","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eCatalytic cracking process optimization\u003c/h2\u003e \u003cp\u003eThe structure and operation modes of batch reactors containing a PE/catalyst slurry during catalytic contact are crucial for improving the conversion and product distribution in low-temperature PE catalytic cracking. The reactor used for this work could operate in either closed-batch or open-batch mode by simply closing or opening the downstream valve that connects to the condenser/collector units as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a) and Supplementary Fig.\u0026nbsp;3. The primary purpose of catalytic decomposition of PE is to obtain liquid hydrocarbon products suitable for further processing in downstream processes. Typically, an improved liquid selectivity can be achieved by minimizing excessive contact between zeolite and hydrocarbon species (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b)). This approach helps to prevent irreversible coke formation and evolution of gas species from over-cracking. Indeed, employing a selected *BEA-type zeolite catalyst (S-BEA-30, see below for the sample information), an open-batch configuration at 330\u0026deg;C resulted in higher conversion and liquid selectivity (45.1% and 62.3%, respectively) than the conventional closed-batch configuration (38.3% and 44.9%, respectively), by allowing the evaporated products to escape the reactor (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a)). The over-cracking, which produces uncrackable solid phase that deactivates the catalysis, is significantly reduced in an open-batch configuration compared to a closed-batch configuration as shown in Supplementary Fig.\u0026nbsp;4.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe inert-gas flow rate is a crucial parameter influencing the conversion and liquid selectivity in the open-batch catalytic cracking of PE. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b) demonstrates that increasing the inert-gas flow rate shifts the selectivity distribution towards heavier products, suggesting fewer catalytic scissions in PE chains due to reduced contact time. The PE conversion increases monotonously with the inert-gas flow rate, while liquid selectivity showed an optimum at 10 mL/min in our reactor setup, which was adopted as the standard reaction condition for subsequent experiments. These results highlight the significance of the reactor design and operation modes in the catalytic PE decomposition into liquid hydrocarbons. Obviously, temperature is a key parameter affecting the rate of catalytic scissions of the main backbone of PE chains. At the optimized inert-gas flow rate of 10 mL/min with the selected zeolite catalyst (S-BEA-30), the conversion of PE is dramatically influenced by the operation temperature as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c). A high conversion of 98.3% was observed at 390\u0026deg;C, near the typical temperature range of the conventional pyrolysis process. Conversely, at the low limit of 260\u0026deg;C, the conversion was low, under 20%, even with the zeolite catalyst. The selectivity towards light C\u003csub\u003e5\u003c/sub\u003e and C\u003csub\u003e6\u003c/sub\u003e liquid hydrocarbons was noticeably low at 260\u0026deg;C, implying sluggish scission of C-C backbones of linear hydrocarbons (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(d)). In this work, we evaluated various zeolite catalysts at 330\u0026deg;C, achieving acceptably high conversion and high liquid selectivity, highlighting disparities among samples.\u003c/p\u003e \u003cp\u003eThe use of zeolites greatly enhances the conversion of PE at low temperatures by accelerating C-C bond scission, catalyzed by Br\u0026oslash;nsted acid sites that promote the carbenium or carbonium mechanisms.\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e In absence of zeolites, just a 0.2% PE conversion was observed at 330\u0026deg;C. To evaluate the effect of zeolite topologies, several commercially available zeolites, including ZSM-5 (MFI), zeolite beta (*BEA), and zeolite Y (FAU) were examined (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(e)). These zeolites achieved PE conversions ranging from 20\u0026ndash;80% at the same temperature. Details on the tested commercial zeolites are provided in the Supplementary Information. All zeolites demonstrated significant isomerization, as indicated by the complexity of the resulting gas chromatograph (GC) profiles (see Supplementary Fig.\u0026nbsp;5). Among the tested commercial zeolites, ZSM-5 having micropores limited by 10MR pore openings, exhibited the highest conversion, but its liquid selectivity was lower than that of zeolite beta due to its high gas selectivity as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(f), which originated from its narrow pore system. ZSM-5 also tended to produce lighter liquid products than the other two frameworks (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(g)). The GC-MS analysis revealed that it produced aromatic compounds as major products due to the 10MR shape selectivity of the MFI framework (Supplementary Fig.\u0026nbsp;5). Conversely, the zeolite Y samples of 12MR pore openings showed relatively low PE conversions, potentially due to their weak acid site strength.\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e The zeolite beta sample of 12MR pore openings achieved a PE conversion comparable to ZSM-5 with the highest liquid selectivity, and aliphatic compounds were detected as major products. In this work, the effects of the intrinsic properties of zeolite on the *BEA framework were investigated. The synthesis of *BEA-type zeolites, which has been extensively studied for decades,\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e offers great synthetic flexibility in terms of Si/Al ratios and crystal sizes.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eIntrinsic properties-controlled beta zeolite catalytic cracking of LDPE\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe catalytic cracking of PE using the prepared *BEA-type zeolites was tested in an open-batch configuration under optimal conditions (10 mL N\u003csub\u003e2\u003c/sub\u003e/min, 330\u0026deg;C, 2 hours) as previously discussed. Figures\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a\u0026ndash;c) show the conversion and liquid selectivity, achieved with the *BEA-type zeolites listed in Table\u0026nbsp;1. The framework Al sites primarily act as Br\u0026oslash;nsted acid sites in zeolites, serving as active sites for the catalytic cracking of long-chain hydrocarbons.\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e Thus, the decrease in Si/Al ratios led to an increase in the PE conversion across all sample series, indicating enhanced apparent catalytic activity. Crystal size also played a crucial role in the PE conversion. The S-series samples, with higher specific external surface area values (Table\u0026nbsp;1), showed higher PE conversions than the L-series samples. A similar trend was observed in liquid selectivity (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b)). Al sites can be located within either the micropores or external surfaces of the zeolite samples. The catalytic conversion of PE over *BEA-type zeolites may occur in two steps: bulky molecule scission at the external surface acid sites, followed by additional scission of smaller molecules within the micropores. We think that the molecular weight distribution of liquid products primarily depends on the spatial distributions of these acid sites as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(e). The S-BEA-10 sample having the most Al sites and the highest external surface area showed a high PE conversion (~\u0026thinsp;80%) and liquid selectivity (~\u0026thinsp;70%) at a low temperature of 330\u0026deg;C. This result offers experimental evidence that reducing crystal size also significantly enhances the PE conversion and liquid selectivity by facilitating the external scission process of polymer chains. Further analysis on the conversion and liquid selectivity is provided in the Supplementary Information.\u003c/p\u003e \u003cp\u003eThe simulated distillation (SIMDIS) results confirmed that over 99% of the liquid portion comprises hydrocarbons in the range from C\u003csub\u003e5\u003c/sub\u003e to C\u003csub\u003e30\u003c/sub\u003e (Supplementary Fig.\u0026nbsp;10 and Table\u0026nbsp;3). Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(d) illustrates the hydrocarbon distribution in liquid products from the catalytic cracking of PE over L-BEA-10, M-BEA-10, and S-BEA-10, which have similar Si/Al ratios but vary in crystal sizes. L-BEA-10 and M-BEA-10 predominantly yielded hydrocarbons in the gasoline (C\u003csub\u003e5\u0026ndash;10\u003c/sub\u003e) range, whereas S-BEA-10 yielded heavier products under the same reaction conditions. Considering the total number of Al sites is similar across the three samples, it suggests that L-BEA-10 and M-BEA-10 have more micropore Al sites than S-BEA-10, providing a greater extents of secondary scission to lighter products. This serves as an example of the reactant shape selectivity.\u003c/p\u003e \u003cp\u003eThe spent catalysts were recovered as entangled chunks mixed with residues, including deposited coke species. The SIMDIS analysis of the Soxhlet extract, using toluene as the solvent, revealed a minimal composition of remaining product-range (C\u003csub\u003e5\u003c/sub\u003e\u0026ndash;C\u003csub\u003e30\u003c/sub\u003e) hydrocarbons in the solid phase (Supplementary Fig.\u0026nbsp;9 and Table\u0026nbsp;3). The spent catalysts should be recoverable and reusable from the remaining solid phase. However, mechanical separation of inorganic catalyst components from the mixture was unsuccessful due to the polymeric organic components remaining in the solid phase, showing a sturdy texture at room temperature. To assess catalyst reusability, a new PE feed of the same amount was directly added to the spent mixture for a second run. The conversion and liquid selectivity in the second run decreased compared to the first, from 78\u0026ndash;67% and from 68\u0026ndash;54%, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a)). However, the product distribution of the liquid product within the range from C\u003csub\u003e5\u003c/sub\u003e to C\u003csub\u003e15\u003c/sub\u003e remained almost unchanged, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b), indicating that coke-induced deactivation primarily influenced the external surfaces of zeolite rather than the micropores. The zeolite catalysts could be separated by removing the residue through air calcination. The regenerated catalyst was found to have physical properties very similar to those of the virgin catalyst, as confirmed by PXRD, SEM, EDS, and BET analyses (Supplementary Fig.\u0026nbsp;12). Consequently, in the catalytic cracking of PE using the regenerated catalyst, both the conversion and liquid selectivity were almost identical (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c\u0026ndash;d)). Finally, the optimized 330\u0026deg;C open-batch reaction conditions were applied to an actual post-consumer PE waste sample collected from a local recycling center, and it was confirmed that the resulting PE conversion and liquid selectivity were similar to those observed with the virgin PE model feed, as illustrated in Supplementary Fig.\u0026nbsp;13.\u003c/p\u003e \u003cp\u003eConventionally, the catalytic cracking of polyolefins using zeolite catalysts have adopted operation temperatures higher than 380\u0026deg;C.\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e This work demonstrates the temperature can be greatly reduced to 330\u0026deg;C while maintaining high PE conversion and liquid selectivity, provided the reactor configuration and catalysts are adequately optimized. The open-batch configuration effectively prevents over-cracking or excess coke formation by properly regulating the contact between the feed molecules and the zeolites, removing the distillates to the gas phase. Proper selection of inert-gas flow rate, which further regulates the contact time, can further enhance the PE conversion and liquid selectivity. Among the tested commercial zeolites, zeolite beta having the *BEA topology exhibited excellent acid site strength, ensuring high conversion of PE even at low temperature and an adequate shape selectivity towards aliphatic liquid products. Along with the Al content of zeolites, the crystal size was confirmed as a crucial factor determining the PE conversion and liquid phase selectivity. Reducing the crystal size ensures high liquid selectivity regardless of the Al content by enhancing the chain scission on the external surfaces of zeolites. This work not only highlights the potential for the low-temperature catalytic cracking of PE using zeolite catalysts but also provides insights into other plastic waste chemical recycling technologies in terms of selection of catalysts.\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eSynthesis of *BEA-type zeolites\u003c/h2\u003e \u003cp\u003eAll *BEA-type zeolites presented in this work were synthesized using conventional hydrothermal methods, recipes that are modifications of the previously reported methods in the literature.\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e Initially, Al sources, OSDA(TEAOH), mineralizers, and water were mixed to achieve a desired gel composition in 40 mL PTFE liners. Subsequently, Si sources were added, ensuring complete dispersion and homogenization by subsequent stirring. The general gel composition can described as 1.0 SiO\u003csub\u003e2\u003c/sub\u003e : \u003cem\u003ex\u003c/em\u003e Al : \u003cem\u003ey\u003c/em\u003e TEAOH : \u003cem\u003ez\u003c/em\u003e (NH\u003csub\u003e4\u003c/sub\u003eF or NaOH) : \u003cem\u003ew\u003c/em\u003e H\u003csub\u003e2\u003c/sub\u003eO. \u003cem\u003ex\u003c/em\u003e determines the Al content, while \u003cem\u003ey\u003c/em\u003e, \u003cem\u003ez\u003c/em\u003e, and \u003cem\u003ew\u003c/em\u003e depend on the different sample series yielding different crystal sizes. Additional aging steps can be added depending on the sample series. The PTFE liners charged with gels were clad in steel autoclaves and transferred to a convection oven preheated to the desired temperature, which could be rotating or static. The progress of crystallization was tracked by analyzing PXRD patterns of aliquots collected every 3\u0026ndash;7 days. Following crystallization, the products were thoroughly rinsed with distilled water and acetone and calcined at 580\u0026deg;C for 6 hours. The resultant *BEA-type zeolites were then converted into their H-forms through ion exchange with ammonium nitrate (NH\u003csub\u003e4\u003c/sub\u003eNO\u003csub\u003e3\u003c/sub\u003e) and subsequent calcination at 580\u0026deg;C for 6 hours. The details of the preparations of the three series of samples (L-, M-, and S-series), including specified gel compositions, are provided in the Supplementary Information, together with the characterizations of the resulting zeolites.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eOpen-batch catalytic cracking process of PE\u003c/h2\u003e \u003cp\u003ePolyolefin catalytic cracking was conducted using open-batch reactive distillation setup in a stirring batch reactor (CheMReSys, R-201) with custom modifications to allow an inert gas flow. Initially, 1 g of zeolite catalyst and 10 g of model feed PE (LDPE, melt index 25 g/10 min at 190\u0026deg;C/2.16 kg, Sigma-Aldrich) were placed in a 75 mL stainless steel liner and sealed within the stirring reactor. The line connected to the reactor was heated to 330\u0026deg;C during the operation with heating tapes to minimize condensation and residue within tubing and fitting. The reaction was performed for 2 hours at a bulk temperature of 330\u0026deg;C with stirring at 200 rpm. Simultaneously, inert gas (N\u003csub\u003e2\u003c/sub\u003e) flowed at a desired rate. The liquid product was collected via a condensation device connected to a cold constant-temperature circulation column set at -15\u0026deg;C, comprising two stages to minimize the process loss. The gaseous product was collected in a gas sampling bag connected to the end of the reactive distillation setup and analyzed using a GC-FID. The details of quantification methods and reactor structure/operation modes are provided in the Supplementary Information.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCharacterizations\u003c/h2\u003e \u003cp\u003ePowder X-ray diffraction (XRD) patterns were obtained with a SMARTLAB instrument (Rigaku, Japan). Scanning electron microscopy (SEM) images and elemental compositions of the zeolites were analyzed using a JSM-7800F Prime microscope equipped with an energy-dispersive spectroscopy (EDS) unit. N\u003csub\u003e2\u003c/sub\u003e physisorption (77 K) isotherms were measured using a BELSORP MINI X sorption analyzer. Prior to measurements, samples underwent a 3-hour degassing step at 300\u0026deg;C using a BELPREP VAC II instrument (MicrotracBEL, Japan). Raman spectra of solid samples were recorded with a DXR2xi instrument (Thermo Fisher Scientific, USA). The selectivity distributions of liquid products were determined using a ChroZen gas chromatography-flame ionization detector (GC-FID, Youngin, Korea), and product identification was carried out with a TSQ 3000 Evo gas chromatography-mass spectrometry (GC-MS) system (Thermo Fisher Scientific, USA) based on the NIST library.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThis research was supported by Korea Institute of Industrial Technology (KITECH) through the Korea Environmental Industry \u0026amp; Technology Institute (KEITI) funded by the Ministry of Environment (ARQ202209004001).\u003c/p\u003e\n\u003cp\u003eAuthor\u0026nbsp;contributions\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eH.K. contributed to zeolite synthesis, catalytic cracking, data collection, and drafting the original manuscript. J.Y. contributed to zeolite synthesis, reactor design, and data collection. K.H.K. contributed to SIMDIS data collection. K.H.K., I.R., and S.J. contributed to developing ideas for experimental designs. S.J. contributed to funding acquisition, project administration, and procuring post-consumer PE waste. J.H.K. contributed to reactor design, supervision, and both writing and reviewing the manuscript.\u003c/p\u003e\n\u003cp\u003eCompeting\u0026nbsp;interests\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interest.\u003c/p\u003e\n\u003cp\u003eSupplementary\u0026nbsp;information\u003c/p\u003e\n\u003cp\u003eCommercial zeolite information, details of reactor operation modes, details of zeolite synthesis, characterization of zeolites, and supplementary analyses on catalytic reactions.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChang, C.-F. \u0026amp; Rangarajan, S. Machine Learning and Informatics Based Elucidation of Reaction Pathways for Upcycling Model Polyolefin to Aromatics. J. Phys. 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Hydrogen Energy 36, 2904\u0026ndash;2935 (2011).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin, Q.-F. \u003cem\u003eet al.\u003c/em\u003e A stable aluminosilicate zeolite with intersecting three-dimensional extra-large pores. Science 374, 1605\u0026ndash;1608 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGaca, P., Drzewiecka, M., Kaleta, W., Kozubek, H. \u0026amp; Nowińska, K. Catalytic Degradation of Polyethylene over Mesoporous Molecular Sieve MCM-41 Modified with Heteropoly Compounds. Pol. J. Environ. Stud. 17 (2008).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSerrano, D. P., Aguado, J. \u0026amp; Escola, J. M. Catalytic cracking of a polyolefin mixture over different acid solid catalysts. Ind. Eng. Chem. Res. 39, 1177\u0026ndash;1184 (2000).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark, J. W., Kim, J.-H. \u0026amp; Seo, G. The effect of pore shape on the catalytic performance of zeolites in the liquid-phase degradation of HDPE. Polym. Degrad. Stab. 76, 495\u0026ndash;501 (2002).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCamblor, M., Mifsud, A. \u0026amp; P\u0026eacute;rez-Pariente, J. Influence of the synthesis conditions on the crystallization of zeolite Beta. Zeolites 11, 792\u0026ndash;797 (1991).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMintova, S. \u003cem\u003eet al.\u003c/em\u003e Variation of the Si/Al ratio in nanosized zeolite Beta crystals. Microporous Mesoporous Mater. 90, 237\u0026ndash;245 (2006).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCaldeira, V. P. \u003cem\u003eet al.\u003c/em\u003e Properties of hierarchical Beta zeolites prepared from protozeolitic nanounits for the catalytic cracking of high density polyethylene. Appl. Catal. A: Gen. 531, 187\u0026ndash;196 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePeral, A. \u003cem\u003eet al.\u003c/em\u003e Bidimensional ZSM-5 zeolites probed as catalysts for polyethylene cracking. Catal. Sci. Technol 6, 2754\u0026ndash;2765 (2016).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSandoval-D\u0026iacute;az, L.-E., Gonz\u0026aacute;lez-Amaya, J.-A. \u0026amp; Trujillo, C.-A. General aspects of zeolite acidity characterization. Microporous Mesoporous Mater. 215, 229\u0026ndash;243 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJon, H., Lu, B., Oumi, Y., Itabashi, K. \u0026amp; Sano, T. Synthesis and thermal stability of beta zeolite using ammonium fluoride. Microporous Mesoporous Mater. 89, 88\u0026ndash;95 (2006).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXie, B. \u003cem\u003eet al.\u003c/em\u003e Organotemplate-Free and Fast Route for Synthesizing Beta Zeolite. Chem. Mater. 20, 4533\u0026ndash;4535 (2008).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXia, Q.-H., Shen, S.-C., Song, J., Kawi, S. \u0026amp; Hidajat, K. Structure, morphology, and catalytic activity of β zeolite synthesized in a fluoride medium for asymmetric hydrogenation. J. Catal. 219, 74\u0026ndash;84 (2003).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eL\u0026oacute;pez, A., de Marco, I., Caballero, B. M., Adrados, A. \u0026amp; Laresgoiti, M. F. Deactivation and regeneration of ZSM-5 zeolite in catalytic pyrolysis of plastic wastes. Waste Manage. (Oxford) 31, 1852\u0026ndash;1858 (2011).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWilliams, P. T. \u0026amp; Brindle, A. J. Catalytic pyrolysis of tyres: influence of catalyst temperature. Fuel 81, 2425\u0026ndash;2434 (2002).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRorrer, J. E. \u003cem\u003eet al.\u003c/em\u003e Role of Bifunctional Ru/Acid Catalysts in the Selective Hydrocracking of Polyethylene and Polypropylene Waste to Liquid Hydrocarbons. ACS Catal. 12, 13969\u0026ndash;13979 (2022).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e. \u003cstrong\u003ePhysical properties of the intrinsic properties-controlled beta zeolites.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"674\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003eEntry\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003eCrystal size (nm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003eSi/Al\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003eS\u003csub\u003eBET\u003c/sub\u003e (m\u003csup\u003e2\u003c/sup\u003e/g)\u003csup\u003e\u0026Dagger;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003eV\u003csub\u003emic\u003c/sub\u003e (cc/g)\u003csup\u003e\u0026Dagger;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003eS\u003csub\u003eExt\u003c/sub\u003e (m\u003csup\u003e2\u003c/sup\u003e/g)\u003csup\u003e\u0026Dagger;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003eV\u003csub\u003emeso\u003c/sub\u003e (cc/g)\u003csup\u003e\u0026Dagger;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eL-BEA-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e650\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e9.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e575\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.239\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.206\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eL-BEA-15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e950\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e16.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e495\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.122\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eL-BEA-20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e1510\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e21.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e472\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.218\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.047\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eL-BEA-30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e1710\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e26.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e424\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.186\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.053\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eM-BEA-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e8.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e589\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.220\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e138\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.728\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eM-BEA-20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e130\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e19.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e569\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.253\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.601\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eS-BEA-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e11.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e634\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.226\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e192\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.971\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eS-BEA-20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e18.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e612\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.263\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.644\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eS-BEA-30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e110\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e28.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e616\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.264\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.650\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"6.25%\" valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.416666666666666%\" valign=\"top\"\u003e\n \u003cp\u003eS-BEA-50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.625%\" valign=\"top\"\u003e\n \u003cp\u003e140\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.375%\" valign=\"top\"\u003e\n \u003cp\u003e48.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e584\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.253\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\" valign=\"top\"\u003e\n \u003cp\u003e0.596\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp;\u003csup\u003e\u0026dagger;\u003c/sup\u003eCharacterized by EDS; \u003csup\u003e\u0026Dagger;\u003c/sup\u003eCharacterized based on the N\u003csub\u003e2\u003c/sub\u003e adsorption isotherms obtained at 77 K. Micropore volumes (V\u003csub\u003emic\u003c/sub\u003e) were estimated based on the V-t method. Mesoporous volumes (V\u003csub\u003emeso\u003c/sub\u003e) were estimated based on the Barrett-Joyner-Halenda (BJH) model.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-3999029/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3999029/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEnvironmental problems are worsening due to the complexity in managing plastic waste. Chemical recycling emerges as a pivotal technology that can suppress additional carbon introduction into the carbon cycle and provide petroleum alternatives for current petrochemical processes, leading to value-added products. The utilization of zeolites can significantly reduce energy consumption by lowering the operation temperature required for pyrolysis. Here, we demonstrate low-temperature catalytic cracking of polyethylene (PE) utilizing an open-batch reactor configuration and *BEA-type zeolite catalysts, maximizing the liquid product selectivity. With the optimized open-batch setup and zeolite properties, high PE conversion (~\u0026thinsp;80%) and liquid selectivity (~\u0026thinsp;70%) were achieved at a low temperature of 330\u0026deg;C, effectively reducing the irreversible coke formation. We systematically explored the effects of aluminum (Al) site density and zeolite crystal size, revealing that zeolite crystal size is another critical factor determining the liquid production from PE due to its reactant shape selectivity. This work not only demonstrates that an effective combination and optimization of reactor and catalysts can enhance the overall catalytic activity but also offers insights into designing catalysis systems for the catalytic recycling of polyolefin wastes.\u003c/p\u003e","manuscriptTitle":"Optimization of Low-Temperature Catalytic Cracking of Polyolefin Waste in Open-Batch Reactors Using Zeolite Beta with Controlled Intrinsic Properties","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-15 21:01:06","doi":"10.21203/rs.3.rs-3999029/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-engineering","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commseng","sideBox":"Learn more about [Communications Engineering](http://link.springer.com/journal/44172)","snPcode":"44172","submissionUrl":"https://mts-commseng.nature.com/cgi-bin/main.plex","title":"Communications Engineering","twitterHandle":"@commseng","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f48d1b6d-2ba4-44b4-b8a2-366b9c428e6c","owner":[],"postedDate":"March 15th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":29410362,"name":"Physical sciences/Engineering/Chemical engineering"},{"id":29410363,"name":"Physical sciences/Chemistry/Catalysis/Heterogeneous catalysis"},{"id":29410364,"name":"Physical sciences/Chemistry/Chemical engineering"}],"tags":[],"updatedAt":"2025-03-25T07:10:41+00:00","versionOfRecord":{"articleIdentity":"rs-3999029","link":"https://doi.org/10.1038/s44172-025-00392-8","journal":{"identity":"communications-engineering","isVorOnly":false,"title":"Communications Engineering"},"publishedOn":"2025-03-24 04:00:00","publishedOnDateReadable":"March 24th, 2025"},"versionCreatedAt":"2024-03-15 21:01:06","video":"","vorDoi":"10.1038/s44172-025-00392-8","vorDoiUrl":"https://doi.org/10.1038/s44172-025-00392-8","workflowStages":[]},"version":"v1","identity":"rs-3999029","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3999029","identity":"rs-3999029","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}