Hydrothermal stability and catalytic performance of desilicated highly siliceous zeolites ZSM-5

Highly siliceous zeolites, namely MFI type have attracted the great attention due to their higher hydrothermal stability, higher selectivity to organic compounds, and often better catalytic properties in comparison with Al-rich zeolites. The native zeolite (Si/Al = 164) and its desilicated analogues were deeply characterized with regard to their structural and textural properties by X-ray diffraction, low temperature adsorption of nitrogen and solid-state Al-27 MAS NMR. Their acidic properties were evaluated in quantitative IR studies. Finally, the catalytic performance of desilicated zeolites ZSM-5 was evaluated in the cracking of n-decane, 1,3,5-tri-iso-propylbenzene and vacuum gas oil. In this article, it is shown that high silica zeolites prepared by NaOH and NaOH&TBAOH leaching presented good hydrothermal stability with only slightly lower resistance when comparing to native steamed zeolite. The mesoporosity was preserved after the steaming treatment. The influence of the generated mesoporosity on the higher activity was evidenced in both 1,3,5-tri-isopropylbenzene and diesel oil cracking of steamed hierarchical zeolites. In spite of their lowered acidity, the mesopores system benefited the diffusion of the bulky molecule and finally provided higher activity of hierarchical zeolites. (C) 2016 Elsevier Inc. All rights reserved.This work was financed by Grant No. 2015/18/E/ST4/00191 from the National Science Centre - Poland. F. Rey and J. Martinez-Triguero thank for the support of the Spanish Government-MINECO through "Severo Ochoa" (SEV 2012-0267), MAT2015-71842-P and CTQ2015-68951-C3-1-R.Tarach, KA.; Martínez-Triguero, J.; Rey Garcia, F.; Góra-Marek, K. (2016). Hydrothermal stability and catalytic performance of desilicated highly siliceous zeolites ZSM-5. Journal of Catalysis. 339:256-259. https://doi.org/10.1016/j.jcat.2016.04.023S25625933

Charge-separation driven mechanism via acylium ion intermediate migration during catalytic carbonylation in mordenite zeolite

By employing ab initio molecular dynamic simulations, solid-state NMR spectroscopy, and two-dimensional correlation analysis of rapid scan Fourier transform infrared spectroscopy data, a new pathway is proposed for the formation of methyl acetate (MA) via the acylium ion (i.e.,CH(3) − C ≡ O(+)) in 12-membered ring (MR) channel of mordenite by an integrated reaction/diffusion kinetics model, and this route is kinetically and thermodynamically more favorable than the traditional viewpoint in 8MR channel. From perspective of the complete catalytic cycle, the separation of these two reaction zones, i.e., the C-C bond coupling in 8MR channel and MA formation in 12MR channel, effectively avoids aggregation of highly active acetyl species or ketene, thereby reducing undesired carbon deposit production. The synergistic effect of different channels appears to account for the high carbonylation activity in mordenite that has thus far not been fully explained, and this paradigm may rationalize the observed catalytic activity of other reactions

Polypropylene cracking on embryonic and ZSM-5 catalysts : an operando study

International audienceA series of ZSM-5 zeolites (embryonic, microporous, hierarchical) is studied in the catalytic cracking of polypropylene in the framework of its chemical recycling. Two important zeolite features impact their catalytic performances and allow their design as efficient catalysts: porosity and acidity. They also play a key role in catalyst deactivation and regeneration. A detailed thermogravimetric and spectroscopic (operando FT-IR) analysis of the reaction, including catalyst coking and regeneration, shows the emergence of rules to design fit-for-purpose catalysts to be used in existing or grass-roots FCC units

Hierarchical zeolites TNU-9 and IM-5 as the catalysts for cracking processes

[EN] The 10-ring zeolites TNU-9 and IM-5 were obtained by a desilication and evaluated in series of acid-catalysed cracking reactions. n-Decane and 1,3,5-tri-iso-propylbenzene cracking were performed as model reactions, while vacuum gas oil, polypropylene and polyethylene were cracked into add-value lower molecular weight chemicals. The catalytic performance improvement of hierarchical zeolites was rationalized by deep acid sites characterization in situ FT-IR studies of pyridine, carbon monoxide and 2,6-di-tert-butylpyridine sorption. Further, operando FT-IR-GC studies supported by 2D COS (two-dimensional correlation) analysis provided insight into cracking and coking of catalysts during polypropylene and polyethylene decomposition. It was found that NaOH-derived catalysts ensure the most upsurged acidity, in terms of number and accessibility of the sites, and then with better performance. In VGO cracking the connected mesopores added post-synthesis increased yields to propylene and middle distillates and lowered coke production. A bigger share of iso-olefins was observed both in VGO and polyolefins cracking products.KGM acknowledges the Grant No 2021/43/B/ST4/00307 form National Science Center, Poland. KAT acknowledges the Grant No 2020/37/B/ST4/01215 form National Science Center, Poland. For the purpose of Open Access, the author has applied a CC-BY public copyright licence to any Author Accepted Manuscript (AAM) version arising from this submission. JMT acknowledges the Grant MFA/2022/016 from Advanced Materials program supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17. I1) and by Generalitat Valenciana. The study was carried out using research infrastructure purchased with the funds of the European Union in the framework of the Smart Growth Operational Program, Measure 4.2; Grant No. POIR.04.02.00-00-D001/20-00, "ATOMIN 2.0-ATOMic scale science for the INnovative economy". The open-access publication of this article has been supported by a grant from the Faculty of Chemistry under the Strategic Programme Excellence Initiative at Jagiellonian University.Tarach, KA.; Martínez-Triguero, J.; Valencia Valencia, S.; Wojciechowska, K.; Rey Garcia, F.; Góra-Marek, K. (2023). Hierarchical zeolites TNU-9 and IM-5 as the catalysts for cracking processes. Applied Catalysis B Environmental. 338. https://doi.org/10.1016/j.apcatb.2023.12306633