Novel hydrotalcite-zeolite composites as precursors for catalysis

Novel hydrotalcite-zeolite composites as precursors for catalysis | 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 Research Article Novel hydrotalcite-zeolite composites as precursors for catalysis Sylwia Górecka, Kateřina Pacultová, Kateřina Karásková, Kamil Górecki, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8045449/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this study, novel Cu-based hydrotalcite-zeolite composites were prepared and studied as potential catalyst precursors. The hydrotalcite phase was formed on zeolite supports with different Si/Al ratios under standard co-precipitation conditions. The zeolite structure remained intact, with only slight changes in acidity for Al-containing samples . The hydrotalcite layers were composed of copper, magnesium and aluminium cations, while the carbonate anions were used as interlayer anions. The composites showed good structural and thermal stability with adjustable acidity, making them promising materials for catalytic applications such as NH₃-SCO. Environmental Chemistry zeolite hydrotalcites mixed metal oxides composite catalysts 1. Introduction Contemporary catalysis requires materials that combine high activity and selectivity with minimal generation of secondary pollutants. Transition metal oxides, ex. copper oxides are reported to be efficient in numerous processes [ 1 , 2 ], such as selective catalytic reduction of nitric oxide (NO x SCR) [ 3 – 5 ]. The performance of these catalysts is strongly influenced by their composition, structural properties and dispersion of active phases. Our scientific interest related to copper-based catalysts includes the potential application of these materials in ammonia oxidation process (NH 3 -SCO), a process that allows conversion of ammonia into environmentally friendly nitrogen (N 2 ) [ 6 ]. A key challenge in NH₃-SCO is to achieve high activity and N₂ selectivity below 400°C. Our previous studies demonstrated that CuO supported on Mg–Al oxides shows promising performance, with selectivity strongly depending on the dispersion of CuO species [ 7 – 11 ]. Increasing copper loading enhances NH 3 conversion; however, it also promotes formation of bulk-like CuO. To address these issues, we designed catalysts that couple Cu-MMOs with zeolite supports. MMOs allow tuning of surface and catalytic properties by varying composition and loading, but their performance is sensitive to metal dispersion and synthesis method [ 12 ]. Zeolites, on the other hand, are characterized by a well-defined, highly developed porous structure, and exhibit higher specific surface area (270–350 m 2 /g) [ 5 , 13 , 14 ] in comparison with mixed metal oxides (15–150 m 2 /g) [ 7 , 8 ]. However, post-synthetic modifications, such as impregnation, can lead to pore blockage, reducing the accessibility of active sites and alter the acidic properties of zeolite framework [ 15 , 16 ]. Our approach is to employ zeolites as structural supports to enhance the dispersion of MMOs, improve catalytic performance, and mitigate their typical limitations such as low surface area and pore blockage. By integrating both components into a composite system, we aim to combine the advantages of each — tunable metal loading from MMOs and high surface area with developed porosity from zeolites — while minimizing their individual drawbacks, particularly the formation of bulk-like MMO species. As the precursors of mixed metal oxides, we have selected hydrotalcite-like materials (HT), which can incorporate various di- and tri-valent cations in different ratios (typically M 3+ /(M 2+ + M 3+ ) = 0.15–0.33 [ 17 ]). As the support material, we have selected zeolite structure with varying Si/Al. The calcination of HTs on zeolite structure is expected to result in homogenous dispersion of oxides across the zeolite surface. Our primary goal is to maximize the exposure of MMO active sites while preserving the structural integrity of the zeolite framework and obtain the catalysts of high surface area and well dispersed active sites. Combining hydrotalcites with other types of materials offers broad opportunities for tailoring their properties. The successful synthesis of composites and hybrid HT materials combined with biochar [ 18 ], hydroxyapatite [ 19 ], melanin [ 20 ] and zeolites [ 21 ] has been reported, highlighting the potential of integrating different components into advanced material structures. The synthesis procedure of new composites should cover the following aspects: Determination of the zeolite stability under the hydrotalcite synthesis conditions. Confirming of the hydrotalcite phase formation on the zeolite support. Evaluating thermal stability to identify the optimal calcination temperature. Characterizing the materials to verify the desired structure and active phases. 2. Material and methods Cu–Mg–Al mixed metal oxides (MMOs) will be obtained by calcining hydrotalcite-like precursors deposited on zeolite via one-pot synthesis, where Cu acts as the active phase and Mg and Al serve as structural promoters. There will be two series of samples, first with weight ratio CuHT:Zeolit 1:1 and second with weight ratio CuHT:Zeolit 2:1. 2.1. Chemicals The zeolite materials were purchased from Zeolyst International, USA. The copper nitrate (Cu(NO 3 ) 2 ∙3H 2 O; purity 99%), magnesium nitrate (Mg(NO 3 ) 2 ∙6H 2 O, purity 99%), aluminium nitrate (Al(NO 3 ) 3 ∙9H 2 O, purity 98%), sodium carbonate (Na 2 CO 3 , purity 99%) and sodium hydroxide (NaOH, purity 98%) were purchased from Penta Chemicals, the Czech Republic. 2.2. Zeolite support stability The stability of each zeolite under HT synthesis conditions was tested by measuring pH changes every 5 min during the first 30 min and every 15 min thereafter throughout the stirring period. 2.3. Synthesis of MMO precursor The hydrotalcite precursor was prepared under the standard synthesis conditions described in our previous works [ 7 ], however in current case the synthesis was performed as one pot synthesis in the presence of the zeolite support. 2.4. Materials characterisation The X-ray diffraction (XRD) was performed using Rigaku SmartLab. The NH 3 temperature programmed desorption (NH 3 -TPD) was performed with use of AutoChemII 2920 (Micromeritics) connected on-line with a quadrupole mass spectrometer HPR-20EGA (Hiden Analytical). The chemical composition of samples was determined with the use of X-ray fluorescence spectroscopy (XRF, Spectro, Xepos, Ametek). The thermogravimetric measurements coupled with mass spectroscopy analysis (TG-MS) were made using SetSys Evolution (Setaram) with analysis of evolved gases using mass spectrometer QMG 700 (Pfeiffer). Low-temperature nitrogen adsorption was performed in a 3Flex Micromeritics sorptometer at temperature of -196°C. Scanning electron microscopy (SEM) was performed with use of Vega 4, Tescan. Temperature programmed reduction with use of hydrogen (H 2 -TPR) was performed in an AutoChem II 2920 Micromeritics apparatus with the thermal conductivity detection (TCD). 3. Results 3.1. Stability of ZSM-5 materials Previous studies on the desilication process [ 22 – 24 ] indicate that hydrothermal treatment of zeolites in NaOH solution at temperatures up to 100°C can alter the Si/Al ratio and framework structure. These conditions are similar to those used for hydrotalcite synthesis [ 7 , 10 , 25 ]. Since maintaining the integrity of zeolite structure is crucial, the stability of the zeolite under hydrothermal conditions was evaluated by examining its phase composition and acidity changes. The zeolite structure after 30, 60 and 90 min of hydrothermal treatment was without significant changes. 3.2. Characterisation of hydrotalcite-zeolites composites Composite materials were prepared by synthesizing Cu–MgAl hydrotalcite (Cu = 5 mol%, Mg = 62 mol%, Al = 33 mol%) in the presence of zeolites with varying Si/Al ratios. The unsupported Cu–MgAl hydrotalcite served as a reference for structure validation. This composition was selected based on previous studies identifying it as an effective precursor for active and selective NH₃-SCO catalysts [ 9 , 10 , 26 ]. The analysis of chemical composition confirms that the calculated weight ratio of HT and zeolite as well as the M 3+ /(M 2+ +M 3+ ) ratio are in line with the intended values. Brief comparison of the reference and composite diffractograms indicates that hydrotalcite deposition does not cause the collapse of the zeolite framework. 3.3. Characterisation of calcined composites The characterisation techniques showed that synthesis of composites of different CuHT:Zeolite ratio is possible and does not influence the structure of support. All samples were calcined at temperature range 200–900°C (with 100°C step). Surface area and porosity evolution The specific surface areas of the samples varied in the ranges of 138–235 m 2 /g and 265–335 m 2 /g, respectively, depending on the calcination temperature and type of used zeolite support. Surface area initially increased with temperature due to HT decomposition and MgO formation, but at ≥ 700°C it decreased as a result of mixed metal oxide phase development. Samples with weight ratio CuHT:zeolite 2:1 exhibited type IV isotherms with H4 hysteresis loops, typical of micro–mesoporous materials [ 27 , 28 ]. Morphology analysis of calcined materials SEM analysis was performed to investigate the microstructure and morphological evolution of the samples as a function of calcination temperature, providing insights into the structural changes induced by thermal treatment. The EDS maps of elements distribution revealed that the copper is homogenously dispersed over the samples surface, without formation of any visible aggregates, despite the calcination temperature. Reducibility of Cu species The H₂-TPR analysis revealed temperature-dependent reduction behavior of copper species, reflecting variations in their dispersion, oxidation state, and interaction with the support. Changes in reduction profiles indicated strong metal–support interactions that influence the stability and reducibility of Cu species. Overall, the results confirmed the predominant presence of oxide-type copper species and demonstrated that thermal treatment significantly affects their redox properties.. 4. Conclusion The study aimed to develop Cu-containing hydrotalcite–zeolite composites (CuHT:Zeolite) through one-pot synthesis and to explore their potential as catalyst precursors. Building on previous findings that emphasized the role of CuO dispersion in ammonia oxidation, the work focused on achieving highly dispersed Cu oxide species supported on high-surface-area zeolites. The results confirm that the synthesis of composite is possible under the standard conditions of hydrotalcite synthesis. Simultaneously, no decomposition or zeolite framework integrity was observed. The XRD measurements of as-synthesized materials confirm formation of hydrotalcite-like materials on the zeolite supports. The subsequent thermal treatment of compounds resulted in an in-situ transformation of hydrotalcites into mixed metal oxides (MMO), while zeolite supports show high stability up to 800°C. Textural characterization revealed that the optimal calcination temperature for achieving the highest specific surface area ( S BET ) and porosity is in the range of 500–600°C. Higher temperatures led to progressive loss of surface area due to increased crystallinity and pore collapse. This study demonstrates the potential of CuHT:zeolite composites for NH₃-SCO catalysis. Future work should evaluate their performance and durability under reaction conditions and explore the applicability of this synthesis approach to other zeolite-based systems. Additionally, the approach developed here could be extended to other zeolite structures to further tailor material properties for specific catalytic applications. Declarations Authors Contribution: Sylwia Górecka – Conceptualization, Investigation, Methodology, Visualisation, Writing – original draft, Writing – review and editing, Kateřina Pacultová – Writing – review and editing, Kateřina Karásková – Investigation, Kamil Górecki – Investigation, Kateřina Kupková – Investigation, Eva Kinnertová – Investigation, Methodology, Antonio Eduardo Palomares Gimeno – Supervision, Writing – review and editing, Lucie Obalová – Writing – review and editing, Project administration. Funding: The work was supported by the OP JAK project "INOVO!!!", No. CZ.02.01.01/00/23_021/0008588 supported by the Ministry of Education, Youth and Sports and co-financed by the European Union. Experimental results were accomplished by using Large Research Infrastructure ENREGAT supported by the Ministry of Education, Youth and Sports of the Czech Republic under project No. LM2023056. 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09:04:03","extension":"html","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":77741,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8045449/v1/485ceebbf2b63730682a7b07.html"},{"id":95526594,"identity":"bbe9e92c-c6e8-44b1-b534-1946bb0462f3","added_by":"auto","created_at":"2025-11-10 10:07:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":583418,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8045449/v1/02873fec-f9a4-49d6-9f14-4e917268ac70.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eNovel hydrotalcite-zeolite composites as precursors for catalysis\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eContemporary catalysis requires materials that combine high activity and selectivity with minimal generation of secondary pollutants. Transition metal oxides, ex. copper oxides are reported to be efficient in numerous processes [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], such as selective catalytic reduction of nitric oxide (NO\u003csub\u003ex\u003c/sub\u003e SCR) [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The performance of these catalysts is strongly influenced by their composition, structural properties and dispersion of active phases. Our scientific interest related to copper-based catalysts includes the potential application of these materials in ammonia oxidation process (NH\u003csub\u003e3\u003c/sub\u003e-SCO), a process that allows conversion of ammonia into environmentally friendly nitrogen (N\u003csub\u003e2\u003c/sub\u003e) [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. A key challenge in NH₃-SCO is to achieve high activity and N₂ selectivity below 400\u0026deg;C. Our previous studies demonstrated that CuO supported on Mg\u0026ndash;Al oxides shows promising performance, with selectivity strongly depending on the dispersion of CuO species [\u003cspan additionalcitationids=\"CR8 CR9 CR10\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Increasing copper loading enhances NH\u003csub\u003e3\u003c/sub\u003e conversion; however, it also promotes formation of bulk-like CuO.\u003c/p\u003e\u003cp\u003eTo address these issues, we designed catalysts that couple Cu-MMOs with zeolite supports. MMOs allow tuning of surface and catalytic properties by varying composition and loading, but their performance is sensitive to metal dispersion and synthesis method [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Zeolites, on the other hand, are characterized by a well-defined, highly developed porous structure, and exhibit higher specific surface area (270\u0026ndash;350 m\u003csup\u003e2\u003c/sup\u003e/g) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] in comparison with mixed metal oxides (15\u0026ndash;150 m\u003csup\u003e2\u003c/sup\u003e/g) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, post-synthetic modifications, such as impregnation, can lead to pore blockage, reducing the accessibility of active sites and alter the acidic properties of zeolite framework [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Our approach is to employ zeolites as structural supports to enhance the dispersion of MMOs, improve catalytic performance, and mitigate their typical limitations such as low surface area and pore blockage. By integrating both components into a composite system, we aim to combine the advantages of each \u0026mdash; tunable metal loading from MMOs and high surface area with developed porosity from zeolites \u0026mdash; while minimizing their individual drawbacks, particularly the formation of bulk-like MMO species.\u003c/p\u003e\u003cp\u003eAs the precursors of mixed metal oxides, we have selected hydrotalcite-like materials (HT), which can incorporate various di- and tri-valent cations in different ratios (typically M\u003csup\u003e3+\u003c/sup\u003e/(M\u003csup\u003e2+\u003c/sup\u003e + M\u003csup\u003e3+\u003c/sup\u003e)\u0026thinsp;=\u0026thinsp;0.15\u0026ndash;0.33 [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]). As the support material, we have selected zeolite structure with varying Si/Al. The calcination of HTs on zeolite structure is expected to result in homogenous dispersion of oxides across the zeolite surface. Our primary goal is to maximize the exposure of MMO active sites while preserving the structural integrity of the zeolite framework and obtain the catalysts of high surface area and well dispersed active sites.\u003c/p\u003e\u003cp\u003eCombining hydrotalcites with other types of materials offers broad opportunities for tailoring their properties. The successful synthesis of composites and hybrid HT materials combined with biochar [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], hydroxyapatite [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], melanin [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] and zeolites [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] has been reported, highlighting the potential of integrating different components into advanced material structures.\u003c/p\u003e\u003cp\u003eThe synthesis procedure of new composites should cover the following aspects:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eDetermination of the zeolite stability under the hydrotalcite synthesis conditions.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eConfirming of the hydrotalcite phase formation on the zeolite support.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eEvaluating thermal stability to identify the optimal calcination temperature.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eCharacterizing the materials to verify the desired structure and active phases.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"2. Material and methods","content":"\u003cp\u003eCu\u0026ndash;Mg\u0026ndash;Al mixed metal oxides (MMOs) will be obtained by calcining hydrotalcite-like precursors deposited on zeolite via one-pot synthesis, where Cu acts as the active phase and Mg and Al serve as structural promoters. There will be two series of samples, first with weight ratio CuHT:Zeolit 1:1 and second with weight ratio CuHT:Zeolit 2:1.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Chemicals\u003c/h2\u003e\u003cp\u003eThe zeolite materials were purchased from Zeolyst International, USA. The copper nitrate (Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e∙3H\u003csub\u003e2\u003c/sub\u003eO; purity 99%), magnesium nitrate (Mg(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e∙6H\u003csub\u003e2\u003c/sub\u003eO, purity 99%), aluminium nitrate (Al(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e∙9H\u003csub\u003e2\u003c/sub\u003eO, purity 98%), sodium carbonate (Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, purity 99%) and sodium hydroxide (NaOH, purity 98%) were purchased from Penta Chemicals, the Czech Republic.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Zeolite support stability\u003c/h2\u003e\u003cp\u003eThe stability of each zeolite under HT synthesis conditions was tested by measuring pH changes every 5 min during the first 30 min and every 15 min thereafter throughout the stirring period.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Synthesis of MMO precursor\u003c/h2\u003e\u003cp\u003eThe hydrotalcite precursor was prepared under the standard synthesis conditions described in our previous works [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], however in current case the synthesis was performed as one pot synthesis in the presence of the zeolite support.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Materials characterisation\u003c/h2\u003e\u003cp\u003e\u003cem\u003eThe X-ray diffraction\u003c/em\u003e (XRD) was performed using Rigaku SmartLab. \u003cem\u003eThe NH\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e \u003cem\u003etemperature programmed desorption\u003c/em\u003e (NH\u003csub\u003e3\u003c/sub\u003e-TPD) was performed with use of AutoChemII 2920 (Micromeritics) connected on-line with a quadrupole mass spectrometer HPR-20EGA (Hiden Analytical). \u003cem\u003eThe chemical composition\u003c/em\u003e of samples was determined with the use of X-ray fluorescence spectroscopy (XRF, Spectro, Xepos, Ametek). \u003cem\u003eThe thermogravimetric measurements coupled with mass spectroscopy analysis\u003c/em\u003e (TG-MS) were made using SetSys Evolution (Setaram) with analysis of evolved gases using mass spectrometer QMG 700 (Pfeiffer). \u003cem\u003eLow-temperature nitrogen adsorption\u003c/em\u003e was performed in a 3Flex Micromeritics sorptometer at temperature of -196\u0026deg;C. \u003cem\u003eScanning electron microscopy\u003c/em\u003e (SEM) was performed with use of Vega 4, Tescan. \u003cem\u003eTemperature programmed reduction with use of hydrogen\u003c/em\u003e (H\u003csub\u003e2\u003c/sub\u003e-TPR) was performed in an AutoChem II 2920 Micromeritics apparatus with the thermal conductivity detection (TCD).\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Stability of ZSM-5 materials\u003c/h2\u003e\u003cp\u003ePrevious studies on the desilication process [\u003cspan additionalcitationids=\"CR23\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] indicate that hydrothermal treatment of zeolites in NaOH solution at temperatures up to 100\u0026deg;C can alter the Si/Al ratio and framework structure. These conditions are similar to those used for hydrotalcite synthesis [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Since maintaining the integrity of zeolite structure is crucial, the stability of the zeolite under hydrothermal conditions was evaluated by examining its phase composition and acidity changes. The zeolite structure after 30, 60 and 90 min of hydrothermal treatment was without significant changes.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Characterisation of hydrotalcite-zeolites composites\u003c/h2\u003e\u003cp\u003eComposite materials were prepared by synthesizing Cu\u0026ndash;MgAl hydrotalcite (Cu\u0026thinsp;=\u0026thinsp;5 mol%, Mg\u0026thinsp;=\u0026thinsp;62 mol%, Al\u0026thinsp;=\u0026thinsp;33 mol%) in the presence of zeolites with varying Si/Al ratios. The unsupported Cu\u0026ndash;MgAl hydrotalcite served as a reference for structure validation. This composition was selected based on previous studies identifying it as an effective precursor for active and selective NH₃-SCO catalysts [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The analysis of chemical composition confirms that the calculated weight ratio of HT and zeolite as well as the M\u003csup\u003e3+\u003c/sup\u003e/(M\u003csup\u003e2+\u003c/sup\u003e+M\u003csup\u003e3+\u003c/sup\u003e) ratio are in line with the intended values.\u003c/p\u003e\u003cp\u003eBrief comparison of the reference and composite diffractograms indicates that hydrotalcite deposition does not cause the collapse of the zeolite framework.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Characterisation of calcined composites\u003c/h2\u003e\u003cp\u003eThe characterisation techniques showed that synthesis of composites of different CuHT:Zeolite ratio is possible and does not influence the structure of support. All samples were calcined at temperature range 200\u0026ndash;900\u0026deg;C (with 100\u0026deg;C step).\u003c/p\u003e\u003cp\u003e\u003cb\u003eSurface area and porosity evolution\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe specific surface areas of the samples varied in the ranges of 138\u0026ndash;235 m\u003csup\u003e2\u003c/sup\u003e/g and 265\u0026ndash;335 m\u003csup\u003e2\u003c/sup\u003e/g, respectively, depending on the calcination temperature and type of used zeolite support. Surface area initially increased with temperature due to HT decomposition and MgO formation, but at \u0026ge;\u0026thinsp;700\u0026deg;C it decreased as a result of mixed metal oxide phase development. Samples with weight ratio CuHT:zeolite 2:1 exhibited type IV isotherms with H4 hysteresis loops, typical of micro\u0026ndash;mesoporous materials [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eMorphology analysis of calcined materials\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSEM analysis was performed to investigate the microstructure and morphological evolution of the samples as a function of calcination temperature, providing insights into the structural changes induced by thermal treatment. The EDS maps of elements distribution revealed that the copper is homogenously dispersed over the samples surface, without formation of any visible aggregates, despite the calcination temperature.\u003c/p\u003e\u003cp\u003e\u003cb\u003eReducibility of Cu species\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe H₂-TPR analysis revealed temperature-dependent reduction behavior of copper species, reflecting variations in their dispersion, oxidation state, and interaction with the support. Changes in reduction profiles indicated strong metal\u0026ndash;support interactions that influence the stability and reducibility of Cu species. Overall, the results confirmed the predominant presence of oxide-type copper species and demonstrated that thermal treatment significantly affects their redox properties..\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThe study aimed to develop Cu-containing hydrotalcite\u0026ndash;zeolite composites (CuHT:Zeolite) through one-pot synthesis and to explore their potential as catalyst precursors. Building on previous findings that emphasized the role of CuO dispersion in ammonia oxidation, the work focused on achieving highly dispersed Cu oxide species supported on high-surface-area zeolites.\u003c/p\u003e\u003cp\u003eThe results confirm that the synthesis of composite is possible under the standard conditions of hydrotalcite synthesis. Simultaneously, no decomposition or zeolite framework integrity was observed.\u003c/p\u003e\u003cp\u003eThe XRD measurements of as-synthesized materials confirm formation of hydrotalcite-like materials on the zeolite supports. The subsequent thermal treatment of compounds resulted in an \u003cem\u003ein-situ\u003c/em\u003e transformation of hydrotalcites into mixed metal oxides (MMO), while zeolite supports show high stability up to 800\u0026deg;C.\u003c/p\u003e\u003cp\u003eTextural characterization revealed that the optimal calcination temperature for achieving the highest specific surface area (\u003cem\u003eS\u003c/em\u003e\u003csub\u003eBET\u003c/sub\u003e) and porosity is in the range of 500\u0026ndash;600\u0026deg;C. Higher temperatures led to progressive loss of surface area due to increased crystallinity and pore collapse.\u003c/p\u003e\u003cp\u003eThis study demonstrates the potential of CuHT:zeolite composites for NH₃-SCO catalysis. Future work should evaluate their performance and durability under reaction conditions and explore the applicability of this synthesis approach to other zeolite-based systems. Additionally, the approach developed here could be extended to other zeolite structures to further tailor material properties for specific catalytic applications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthors Contribution: Sylwia Górecka\u003c/strong\u003e – Conceptualization, Investigation, Methodology, Visualisation, Writing – original draft, Writing – review and editing, \u003cstrong\u003eKateřina Pacultová\u003c/strong\u003e – Writing – review and editing, \u003cstrong\u003eKateřina Karásková\u003c/strong\u003e – Investigation, \u003cstrong\u003eKamil Górecki\u003c/strong\u003e – Investigation, \u003cstrong\u003eKateřina Kupková\u003c/strong\u003e– Investigation, \u003cstrong\u003eEva Kinnertová\u003c/strong\u003e– Investigation, Methodology, \u003cstrong\u003eAntonio Eduardo Palomares Gimeno\u003c/strong\u003e – Supervision, Writing – review and editing, \u003cstrong\u003eLucie Obalová\u003c/strong\u003e– Writing – review and editing, Project administration.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe work was supported by the OP JAK project \"INOVO!!!\", No. CZ.02.01.01/00/23_021/0008588 supported by the Ministry of Education, Youth and Sports and co-financed by the European Union.\u003c/p\u003e\n\u003cp\u003eExperimental results were accomplished by using Large Research Infrastructure ENREGAT supported by the Ministry of Education, Youth and Sports of the Czech Republic under project No. LM2023056.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e Authors are grateful to Lenka Matějová and Ivana Troppová for nitrogen physisorption measurements.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interests:\u003c/strong\u003e The authors declare no conflict 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.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability:\u0026nbsp;\u003c/strong\u003eOpen research data will be available on Zenodo in the final version of the paper.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eM.S. Kamal, S.A. Razzak, M.M. Hossain, Catalytic oxidation of volatile organic compounds (VOCs) - A review, Atmos Environ 140 (2016) 117\u0026ndash;134. https://doi.org/10.1016/j.atmosenv.2016.05.031.\u003c/li\u003e\n \u003cli\u003eD. Delimaris, T. Ioannides, VOC oxidation over CuO-CeO2 catalysts prepared by a combustion method, Appl Catal B 89 (2009) 295\u0026ndash;302. https://doi.org/10.1016/j.apcatb.2009.02.003.\u003c/li\u003e\n \u003cli\u003eA. Łącz, P. Gw\u0026oacute;źdź, A. Mizera, S. G\u0026oacute;recka, K. Pacultov\u0026aacute;, L. 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Thommes, Progress in the Physisorption Characterization of Nanoporous Gas Storage Materials, Engineering 4 (2018) 559\u0026ndash;566. https://doi.org/10.1016/j.eng.2018.06.001.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Technical University of Ostrava","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"zeolite, hydrotalcites, mixed metal oxides, composite catalysts","lastPublishedDoi":"10.21203/rs.3.rs-8045449/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8045449/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003eIn this study, novel Cu-based hydrotalcite-zeolite composites were prepared and studied as potential catalyst precursors. The hydrotalcite phase was formed on zeolite supports with different Si/Al ratios under standard co-precipitation conditions. The zeolite structure remained intact, with only slight changes in acidity for Al-containing samples\u003c/em\u003e.\u003cem\u003e The hydrotalcite layers were composed of copper, magnesium and aluminium cations, while the carbonate anions were used as interlayer anions.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eThe composites showed good structural and thermal stability with adjustable acidity, making them promising materials for catalytic applications such as NH₃-SCO.\u003c/em\u003e\u003c/p\u003e","manuscriptTitle":"Novel hydrotalcite-zeolite composites as precursors for catalysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-07 09:03:58","doi":"10.21203/rs.3.rs-8045449/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d5ce8537-1654-4764-88cf-f7411fc69fd0","owner":[],"postedDate":"November 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":57532864,"name":"Environmental Chemistry"}],"tags":[],"updatedAt":"2025-11-07T09:03:58+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-07 09:03:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8045449","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8045449","identity":"rs-8045449","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}