Hierarchical Mesoporosity Surpasses Acidity Reduction For Mitigating Coke Deactivation: Comparative Study Of Desilicated And Dealuminated HY Zeolites In Aromatic Alkylation
DOI:
https://doi.org/10.29284/wf9fks33Keywords:
HY zeolite, post-synthesis modification, dealumination, desilication, hierarchical zeolite.Abstract
Liquid-phase aromatic alkylation over HY zeolites offers an efficient route to alkylated aromatics. Secondary oligomerization and polyalkylation during reaction generate heavy hydrocarbon species that accumulate as coke within the pore network and on Brønsted acid sites, reduce site accessibility, and shorten time-on-stream stability. Post-synthesis modification that tunes acidity or introduces hierarchical porosity remains necessary to lessen deactivation and improve catalytic durability. The study examines freshly prepared HY alongside dealuminated and desilicated HY in liquid-phase alkylation of toluene with 1-octene, with a focus on catalytic activity, stability, and coke deposition behavior. Hydrothermal synthesis of Na-Y was used to prepare the parent HY zeolite, which was then subjected to double ammonium ion exchange and activated by heating. Desilicated HY showed enhanced crystallinity and a high specific surface area (700.5 m² g-¹) and maintained the total pore volume (0.344 cm³ g-¹), with the microporous FAU framework largely intact. Dealuminated HY, in contrast, exhibited partial framework degradation, a decreased surface area (538.8 m² g-¹), and a higher Si/Al ratio of 5.3.
Optimized testing in a batch reactor (toluene:1-octene molar ratio of 10:1, 110 °C, and 350 mg catalyst) showed that desilicated HY achieved the highest 1-octene conversion (92%) and maintained high stability over 300 min on stream. Post-reaction TGA and CHNS results indicated that desilicated HY contained the lowest coke content (6.83 wt.%), a decrease of about 54% compared with fresh HY (12.62 wt.%). Enhanced diffusion of bulky intermediates through hierarchical mesopores inhibited secondary polymerization and reduced the formation of hard coke. The findings indicate that controlled desilication is more effective in reducing catalyst deactivation in alkylation reactions involving bulky intermediates than acidity reduction through dealumination.
References
1. Sohn, S. and P. Do, Linear Alkylbenzenes: An Overview of the Commercial HF and Detal™ Process Unit Alkylation Technology (Case Study), in Industrial Arene Chemistry. 2023. p. 729-745.
2. Al-Sultani, S.H., et al., Sustainable Liquid-Phase Alkylation of Toluene Using Zeolitic Catalysts: A Comparative Evaluation of Al-Rich Y and Si-Rich Beta Zeolites for Industrial Green Chemistry to Support Sustainable Development Goals (SDGs). 2025. 6(2): p. 24 %J ASEAN Journal of Science and Engineering.
3. Rueping, M. and B.J. Nachtsheim, A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis. Beilstein Journal of Organic Chemistry, 2010. 6.
4. Pan, A., et al., Synergistic Brønsted/Lewis acid catalyzed aromatic alkylation with unactivated tertiary alcohols or di-tert-butylperoxide to synthesize quaternary carbon centers. Chemical Science, 2022. 13(12): p. 3539-3548.
5. Al-Sultani, S.H., A. Al-Shathr, and B.Y. Al-Zaidi, Toluene Alkylation Reactions over Y-Type Zeolite Catalysts: An Experimental and Kinetic Study. 2024. 5(4): p. 1042-1065.
6. Armor, J.N., A history of industrial catalysis. Catalysis Today, 2011. 163(1): p. 3-9.
7. Khalil, M., et al., Experimental and Kinetic Study of the Catalytic Behavior of Sulfate-Treated Nanostructured Bifunctional Zirconium Oxide Catalysts in n-Heptane Hydroisomerization Reactions. 2023. 7(6): p. 115.
8. Al-Sultani, S.H., A. Al-Shathr, and B.Y. Al-Zaidi, Aromatics Alkylated with Olefins Utilizing Zeolites as Heterogeneous Catalysts: A Review. 2024. 5(4): p. 900-927.
9. Guisnet, M., “Coke” molecules trapped in the micropores of zeolites as active species in hydrocarbon transformations. Journal of Molecular Catalysis A: Chemical, 2002. 182–183: p. 367-382.
10. Chen, F.-J. and J. Yu, Discovery of Stable Extra-large Pore Zeolites Based on Rational Design of Structure-directing Agents. Accounts of Chemical Research, 2025. 58(15): p. 2402-2414.
11. Al-Shathr, A., et al., Experimental and kinetic studies of the advantages of coke accumulation over Beta and Mordenite catalysts according to the pore mouth catalysis hypothesis. Catalysis Communications, 2023. 181: p. 106718.
12. Waqas, M., et al., Mesostructured bimetallic MFI zeolite for efficient aromatization of light naphtha to BTX aromatics. Journal of Porous Materials, 2025.
13. Quintana-Gómez, L., et al., “Reverse combustion” of carbon dioxide in water: The influence of reaction conditions. Frontiers in Energy Research, 2022. 10: p. 917943.
14. Al-Shathr, A., et al., Investigation of toluene alkylation with hept-1-ene over fresh and modified h-beta catalysts according to apparent activation energy values. South African Journal of Chemical Engineering, 2025. 54: p. 114-132.
15. Roth, W.J., et al., Top-down engineering of zeolite porosity. Chemical Society Reviews, 2025. 54(16): p. 7484-7560.
16. Hijazi, N., et al., Chemical engineering of zeolites: alleviating transport limitations through hierarchical design and shaping. Chemical Society Reviews, 2025. 54(13): p. 6335-6384.
17. Guo, X., et al., Enhancing Atomic Layer Deposition Efficiency of the Classical Medium-Pore ZSM-5 Zeolite by an Artful Alkali-Etching Technique for Boosting NH3-SCR Behaviors. Environmental Science & Technology, 2026. 60(2): p. 2245-2254.
18. Miyashita, K., et al., Quantitative Estimation of Effective Brønsted Acid Sites of Silica-Supported H4SiW12O40 Heteropoly Acid for Adsorption of Various Molecules. Langmuir, 2025. 41(2): p. 1491-1501.
19. Corma, A., From Microporous to Mesoporous Molecular Sieve Materials and Their Use in Catalysis. Chemical Reviews, 1997. 97(6): p. 2373-2420.
20. Cui, J.-W., et al., Engineering Hierarchy to Porous Organic Cages for Biomimetic Catalytic Applications. Accounts of Materials Research, 2025. 6(4): p. 484-498.
21. Patra, K., et al., Harnessing Advanced Porous Materials, Covalent Organic Frameworks, and Porous Organic Polymers as Next-Generation Porous Frameworks for Targeted Removal of Emerging Water Contaminants. ACS Applied Engineering Materials, 2025. 3(5): p. 1130-1165.
22. Wang, H., Q. Wu, and F.-S. Xiao, Design of zeolite-based catalysts by Le Chatelier's principle. Applied Catalysis B: Environment and Energy, 2025. 379: p. 125671.
23. Zhu, Z., et al., The roles of acidity and structure of zeolite for catalyzing toluene alkylation with methanol to xylene. Microporous and Mesoporous Materials, 2006. 88(1): p. 16-21.
24. Degnan, T.F., Applications of zeolites in petroleum refining. Topics in Catalysis, 2000. 13(4): p. 349-356.
25. Guisnet, M., L. Costa, and F.R. Ribeiro, Prevention of zeolite deactivation by coking. Journal of Molecular Catalysis A: Chemical, 2009. 305(1–2): p. 69-83.
26. Tao, Y., et al., Mesopore-Modified Zeolites: Preparation, Characterization, and Applications. Chemical Reviews, 2006. 106(3): p. 896-910.
27. Jiang, J., J. Yu, and A. Corma, Extra-Large-Pore Zeolites: Bridging the Gap between Micro and Mesoporous Structures. 2010. 49(18): p. 3120-3145.
28. Derouane, E.G., et al., The Acidity of Zeolites: Concepts, Measurements and Relation to Catalysis: A Review on Experimental and Theoretical Methods for the Study of Zeolite Acidity. Catalysis Reviews, 2013. 55(4): p. 454-515.
29. Blatter, F. and E. Schumacher, The preparation of pure zeolite NaY and its conversion to high-silica faujasite: An experiment for laboratory courses in inorganic chemistry. Journal of Chemical Education, 1990. 67(6): p. 519.
30. Martínez, C. and A. Corma, Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes. Coordination Chemistry Reviews, 2011. 255(13): p. 1558-1580.
31. Pérez-Ramírez, J., et al., Hierarchical zeolites: enhanced utilisation of microporous crystals in catalysis by advances in materials design. Chemical Society Reviews, 2008. 37(11): p. 2530-2542.
32. Zhu, T., et al. Synthesis and Applications of Zeolite-Encapsulated Metal Catalysts. Catalysts, 2025. 15, DOI: 10.3390/catal15090836.
33. Kim, D.W., D.S. Choi, and J.B. Joo, Synthesis of hierarchical zeolites for enhanced catalytic cracking performance toward larger hydrocarbon molecules. Advances in Industrial and Engineering Chemistry, 2025. 1(1): p. 30.
34. Serrano, D.P., J.M. Escola, and P. Pizarro, Synthesis strategies in the search for hierarchical zeolites. Chemical Society Reviews, 2013. 42(9): p. 4004-4035.
35. Svelle, S., et al., How defects and crystal morphology control the effects of desilication. Catalysis Today, 2011. 168(1): p. 38-47.
36. Wei, Y., et al. Tailoring and visualizing the pore architecture of hierarchical zeolites. 2015. DOI: 10.1039/C5CS00155B.
37. Martins, A., et al., Zeolites and Related Materials as Catalyst Supports for Hydrocarbon Oxidation Reactions. 2022. 12(2): p. 154.
38. Maschmeyer, T. and L. van de Water, An Overview of Zeolite, Zeotype and Mesoporous Solids Chemistry: Design, Synthesis and Catalytic Properties, in Catalysts for Fine Chemical Synthesis. 2006. p. 1-38.
39. Groen, J.C., Mesoporous Zeolites Obtained by Desilication. 2007, Netherlands: Ponsen & Looijen B.V.
40. Dědeček, J., Z. Sobalík, and B. Wichterlová, Siting and Distribution of Framework Aluminium Atoms in Silicon-Rich Zeolites and Impact on Catalysis. Catalysis Reviews, 2012. 54(2): p. 135-223.
41. Lutz, W. Zeolite Y: Synthesis, Modification, and Properties—A Case Revisited. Hindawi Publishing Corporation 2014 [cited 2014; 1-20]. Available from: http://www.hindawi.com/journals/amse/2014/724248/
42. Groen, J.C., et al., Mechanism of hierarchical porosity development in MFI zeolites by desilication: the role of aluminium as a pore-directing agent. Chemistry, 2005. 11(17): p. 4983-94.
43. Bian, Y., et al., Nanosheet zeolites: controlled synthesis, characterization, and advanced catalysis applications. Materials Horizons, 2025. 12(18): p. 7133-7159.
44. Lee, H., et al., Unveiling the Catalytic Superiority of Ti-MWW Zeolite for Sustainable Lactide Production from Methyl Lactate. ACS Omega, 2025. 10(50): p. 62134-62144.
45. Sarkar, S., et al., The multifaceted role of zeolites in modern agriculture and environmental management. Journal of Plant Nutrition, 2025. 48(20): p. 3589-3616.
46. Verboekend, D. and J. Pérez-Ramírez, Design of hierarchical zeolite catalysts by desilication. Catalysis Science & Technology, 2011. 1: p. 841-1084.
47. Silaghi, M.-C., C. Chizallet, and P. Raybaud, Challenges on molecular aspects of dealumination and desilication of zeolites. Microporous and Mesoporous Materials, 2014. 191: p. 82-96.
48. Talebian-Kiakalaieh, A. and S. Tarighi, Synthesis of hierarchical Y and ZSM-5 zeolites using post-treatment approach to maximize catalytic cracking performance. Journal of Industrial and Engineering Chemistry, 2020. 88: p. 167-177.
49. Da, Z., P. Magnoux, and M. Guisnet, Liquid phase alkylation of toluene with 1-heptene over a HFAU zeolite: evidence for transalkylation between toluene and non-desorbed products. Applied Catalysis A: General, 1999. 182(2): p. 407-411.
50. Čejka, J. and B. Wichterlová, ACID-CATALYZED SYNTHESIS OF MONO- AND DIALKYL BENZENES OVER ZEOLITES: ACTIVE SITES, ZEOLITE TOPOLOGY, AND REACTION MECHANISMS. Catalysis Reviews, 2002. 44(3): p. 375-421.
51. Ponomareva, O.A., et al., Benzene alkylation with dodecene-1 over micro-mesoporous molecular sieves. Petroleum Chemistry, 2010. 50(6): p. 427-436.
52. Kim, M.-R. and S. Kim, Enhanced Catalytic Oxidation of Toluene over Hierarchical Pt/Y Zeolite. 2022. 12(6): p. 622.
53. Ahmed, R., C.M. Sinnathambi, and D. Subbarao, Kinetics of De-coking of Spent Reforming Catalyst. Journal of Applied Sciences, 2011. 11: p. 1225-1230.
54. Bauer, F. and H.G. Karge, Characterization of Coke on Zeolites, in Characterization II, H.G. Karge and J. Weitkamp, Editors. 2007, Springer Berlin Heidelberg: Berlin, Heidelberg. p. 249-364.
55. Cerqueira, H.S., et al., Coke formation and coke profiles during the transformation of various reactants at 450°C over a USHY zeolite. Applied Catalysis A: General, 2001. 208(1): p. 359-367.
56. Dong, H.-j. and L. Shi, Alkylation of Toluene with t-Butyl Alcohol over Zeolite Catalysts. Industrial & Engineering Chemistry Research, 2010. 49(5): p. 2091-2095.
57. Ma, H., et al., Metal-Modified Zeolites for Catalytic Dehydration of Bioethanol to Ethylene: Mechanisms, Preparation, and Performance. 2025. 15(8): p. 791.
58. Magnoux, P., et al., Influence of the acidity and of the pore structure of zeolites on the alkylation of toluene by 1-heptene, in Studies in Surface Science and Catalysis, A.B. H.U. Blaser and R. Prins, Editors. 1997, Elsevier. p. 107-114.
59. Lovás, P., et al., Preparation of an active and regenerable catalyst for liquid-phase alkylation of toluene with 1-decene. Applied Catalysis A: General, 2014. 475: p. 341-346.
60. Pérez-Pariente, J., M. Sanchez-Sanchez, and J. Pliego, Post-Synthesis Surfactant-Induced Mesoporosity in Zeolite Crystals: State-of-the-Art, Open Questions and Perspectives. 2025. p. 315-358.
61. Rutkowska, M. and L. Chmielarz, Application of Mesoporous/Hierarchical Zeolites as Catalysts for the Conversion of Nitrogen Pollutants: A Review. 2024. 14(5): p. 290.
62. Bekele, B.T. and R. Gounder, Extra-Framework Aluminum Moieties Occluded within Zeolite Micropores Strengthen Dispersive Stabilization of Confined Alkanes and Carbocationic Transition States. ACS Catalysis, 2025. 15(24): p. 21100-21114.
63. Zhu, X., et al., Constructing Hierarchical Zeolites with Highly Complete Framework via Controlled Desilication. 2024. 63(50): p. e202411446.
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