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

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

Ce-modified zeolite BEA catalysts for the trichloroethylene oxidation. The role of the different and necessary active sites

[EN] This paper reports the activity of different Ce-BEA zeolites for the catalytic oxidation of trichloroethylene and it is focused on determining the nature of the catalyst active sites. The study was made by using a microporous zeolite BEA, two types of desilicated BEA zeolites and mildly steamed desilicated BEA zeolites. The catalysts were prepared by introducing Ce to the zeolites with incipient wetness impregnation and their structural, textural, and acidic properties were established. The evolution of TCE conversion was correlated with the physicochemical properties of the zeolites. It is shown that highly developed mesopore surface area, well-dispersed cerium species and a high number of Bronsted sites results in the highest activity. The activity and selectivity of the Ce-loaded zeolites were found to be dependent on the number of high strength Bronsted acid centres. The hierarchical materials with a higher density of hydroxyls showed higher yields to HCl while the formation of chlorine was prevented.The work was financed by the Grant No. 2015/18/E/ST4/00191 from the National Science Centre, Poland. J.M-T. and A.E.P thank Spanish Governmentthrough "Severo Ochoa" SEV-2016-0683, RTI2018-099668-B-C21, RTI2018-101784-B-I00 and the Fundacion Ramon Arecesthrough a research contract of the "Life and Materials Science" program.Golabek, K.; Palomares Gimeno, AE.; Martínez-Triguero, J.; Tarach, KA.; Kruczala, K.; Girman, V.; Góra-Marek, K. (2019). Ce-modified zeolite BEA catalysts for the trichloroethylene oxidation. The role of the different and necessary active sites. Applied Catalysis B Environmental. 259:1-12. https://doi.org/10.1016/j.apcatb.2019.11802211225

Advanced oxidation process for coke removal:A systematic study of hydrogen peroxide and OH-derived-Fenton radicals of a fouled zeolite

The regeneration process of a fouled catalyst typically involves treatments at high temperature which often cause irreversible damages on the catalyst’s properties. In this work, Fenton chemistry-derived •OH species, and H2O2, are proposed as oxidizing agents to reactivate a porous catalyst at mild conditions, below 100 °C. The chosen catalyst is a microporous ZSM-5 zeolite, which is a challenging candidate due to the mass transfer limitations with possible recombination of the hydroxyl radicals; thereby being an obstacle to oxidize organics occluded in the micropores. The organics deposition over a ZSM-5 zeolite during the D-glucose dehydration reaction was confirmed by a number of characterization techniques, which revealed a considerable decrease in the surface area, pore volume and acid site density in the fouled catalyst. By properly selecting the regeneration conditions, reactivation via Fenton or H2O2 was highly effective in terms of removal of the organics as well as recovery of the initial catalytic activity. The properties of the H2O2 treated-zeolite, the optimal treatment in this case study, were preserved with similar structural and textural features and improved acidity. Hot water extraction was ineffective to remove the humins from ZSM-5. Mechanistically, the presence of Fe impurities in the zeolite structure did not allow to discriminate between a homo, heterogeneous, or a direct H2O2 pathway, or a combination of them. The exhibited conversion by the regenerated zeolite was comparable to that of the fresh one

Opening up ZSM-5 Hierarchical Zeolite’s Porosity through Sequential Treatments for Improved Low-Density Polyethylene Cracking

An adequately tuned acid wash of hierarchical ZSM-5 zeolites offers a levelling up in the catalytic cracking of low-density polyethylene. Identification of crucial and limiting factors governing the activity of the zeolite was extended with studies about the accessibility of acid sites, nature of the realuminated layer and role of Lewis acid sites. The sequential treatment of a ZSM-5 zeolite offered enhanced activity in low-density polyethylene (LDPE) cracking at low and high conversions, as confirmed by a decrease in the temperatures needed to reach 20% and 80% conversion (T20 and T80, respectively). A linear dependence of the T80 on the coupled IHF (indexed hierarchy factor) and AFB (accessibility factor) highlighted the importance of the textural and acidic parameters in the catalytic cracking of LDPE. Operando FT-IR-GC studies confirmed a higher fraction of short-chain hydrocarbons (C3–C5) in the product distribution of hierarchical catalysts resulting from the effective polymer cracking in easily accessible pores

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

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

Process Intensification of Mesoporous Material's Synthesis by Microwave-Assisted Surfactant Removal

Mesoporous materials are of vital importance for use in separation, adsorption, and catalysis. The first step in their preparation consists of synthesizing an organic-inorganic hybrid in which a structuring directing agent (SDA, normally a surfactant) is used to provide the desired porosity. The most common method to eliminate the SDA, and generate the porosity, is high-Temperature calcination. Such a process is energy-intensive and slow. In this study, we investigated alternative nonthermal surfactant removal methods on a soft MCM-41 material, aiming at reducing the processing time and temperature, while maximizing the material's properties. The choice of a soft MCM-41 is critical since it is hydrothermally unstable, whereas the SDA removal is troublesome. Microwave processing yielded outstanding performance in terms of surfactant removal, structural preservation, and textural features; the surfactant was fully removed, the hexagonal structure was preserved, and the surface was highly rich in Si-OH groups. It is suggested that H2O2 is the dominant oxidant. In terms of the process features, the processing time is significantly reduced, 14 h (calcination) versus 5 min (microwaves), and the applied temperature is much lower. The energy savings were estimated to be 72% lower as compared to calcination; therefore, this approach contributes to the process intensification of a very relevant material's production. </p

Three-dimensional organization of pyrrolo[3,2-b]pyrrole-based triazine framework using nanostructural spherical carbon: enhancing electrochemical performance of materials for supercapacitors

Abstract Covalent triazine-based frameworks have attracted much interest recently due to their high surface area and excellent thermal and electrochemical stabilities. This study shows that covalently immobilizing triazine-based structures on spherical carbon nanostructures results in the organization of micro- and mesopores in a three-dimensional manner. We selected the nitrile-functionalized pyrrolo[3,2-b]pyrrole unit to form triazine rings to construct a covalent organic framework. Combining spherical carbon nanostructures with the triazine framework produced a material with unique physicochemical properties, exhibiting the highest specific capacitance value of 638 F g−1 in aqueous acidic solutions. This phenomenon is attributed to many factors. The material exhibits a large surface area, a high content of micropores, a high content of graphitic N, and N-sites with basicity and semi-crystalline character. Thanks to the high structural organization and reproducibility, and remarkably high specific capacitance, these systems are promising materials for use in electrochemistry. For the first time, hybrid systems containing triazine-based frameworks and carbon nano-onions were used as electrodes for supercapacitors

Zeolite-driven Ag species during redox treatments and catalytic implications for SCO of NH3NH_3

[EN] Supported silver species are among the most promising catalysts for the depletion of ammonia emission by selective catalytic oxidation (NH3-SCO). Here, an investigation on the influence of small pore CHA and RHO zeolite structures on the silver species formed and their catalytic activity for the NH3-SCO reaction has been conducted. To this end, AgRHO(4) and AgCHA(4) zeolites with similar Si/Al molar ratios (approximate to 4) and silver content (similar to 15 wt%, Ag/Al approximate to 0.6), and AgCHA(2) with Si/Al approximate to 2 and higher silver loading, while maintaining the Ag/Al ratio (similar to 26 wt%, Ag/Al approximate to 0.6), have been submitted to different treatments and characterized by using a large variety of techniques (XRD, UV-Vis, Ag-109 NMR, in situ XAS and operando FT-IR). The reduction of the AgCHA and AgRHO zeolites at low temperature (100-200 degrees C) produces silver clusters, which remain in the AgRHO zeolite when the temperature is increased to 400 degrees C. However, the silver species in the AgCHA zeolites evolve to nanoparticles (NPs) at 400 degrees C under H-2. The catalytic tests show that metal particles are the active sites while silver clusters are inactive for the NH3-SCO reaction. Also, there are important differences in the stability of the reduced Ag species under oxidizing or under reaction conditions at 400 degrees C. Metal NPs are partially redispersed and oxidized to (Ag)(n)(+), while silver clusters are completely oxidized to Ag+. Our results indicate that silver clusters are stabilized in the RHO-type and not in the CHA-type zeolite, and thus they display very different catalytic activities for the NH3-SCO reaction.The authors acknowledge grant RTI2018-101784-B-I00 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe". Also, the project SEV-2016-0683 funded by MCIN/AEI/10.13039/501100011033 is acknowledged. The project Prometeo/2021/077, Conselleria de Educacion, Cultura y Deporte de la Generalitat Valenciana is also acknowledged. K. G.-M. acknowledges Grant No. 2015/18/E/ST4/00191 from the National Science Centre, Poland. K. T. acknowledges the scholarship within the Bekker Programme (PPN/BEK/2018/1/00406) from the Polish National Agency for Academic Exchange. C. W. Lopes (Science without Frontiers -Process no. 13191/13-6) thanks Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior -Brasil (CAPES - Finance Code 001) for the predoctoral fellowship. J. Martinez-Ortigosa (SEV-20120267-02) acknowledges the Severo Ochoa Program for a predoctoral fellowship. We gratefully acknowledge the ALBA synchrotron for allocating beamtime (proposals 2016021665 and 2017032119), CLAESS beamline staff, and particularly Carlo Marini for their help and technical support during our experiment.W. Lopes, C.; Martinez-Ortigosa, J.; Góra-Marek, K.; Tarach, K.; Vidal Moya, JA.; Palomares Gimeno, AE.; Agostini, G.... (2021). Zeolite-driven Ag species during redox treatments and catalytic implications for SCO of NH3. Journal of Materials Chemistry A. 9(48):27448-27458. https://doi.org/10.1039/d1ta09625g274482745894

Zeolite-driven Ag species during redox treatments and catalytic implications for SCO of NH3

Supported silver species are among the most promising catalysts for the depletion of ammonia emission by selective catalytic oxidation (NH-SCO). Here, an investigation on the influence of small pore CHA and RHO zeolite structures on the silver species formed and their catalytic activity for the NH-SCO reaction has been conducted. To this end, AgRHO(4) and AgCHA(4) zeolites with similar Si/Al molar ratios (≈ 4) and silver content (∼15 wt%, Ag/Al ≈ 0.6), and AgCHA(2) with Si/Al ≈ 2 and higher silver loading, while maintaining the Ag/Al ratio (∼26 wt%, Ag/Al ≈ 0.6), have been submitted to different treatments and characterized by using a large variety of techniques (XRD, UV-Vis,Ag NMR,in situXAS andoperandoFT-IR). The reduction of the AgCHA and AgRHO zeolites at low temperature (100-200 °C) produces silver clusters, which remain in the AgRHO zeolite when the temperature is increased to 400 °C. However, the silver species in the AgCHA zeolites evolve to nanoparticles (NPs) at 400 °C under H. The catalytic tests show that metal particles are the active sites while silver clusters are inactive for the NH-SCO reaction. Also, there are important differences in the stability of the reduced Ag species under oxidizing or under reaction conditions at 400 °C. Metal NPs are partially redispersed and oxidized to (Ag), while silver clusters are completely oxidized to Ag. Our results indicate that silver clusters are stabilized in the RHO-type and not in the CHA-type zeolite, and thus they display very different catalytic activities for the NH-SCO reaction.The authors acknowledge grant RTI2018-101784-B-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. Also, the project SEV-2016-0683 funded by MCIN/AEI/10.13039/501100011033 is acknowledged. The project Prometeo/2021/077, Conselleria de Educación, Cultura y Deporte de la Generalitat Valenciana is also acknowledged. K. G.-M. acknowledges Grant No. 2015/18/E/ST4/00191 from the National Science Centre, Poland. K. T. acknowledges the scholarship within the Bekker Programme (PPN/BEK/2018/1/00406) from the Polish National Agency for Academic Exchange. C. W. Lopes (Science without Frontiers – Process no. 13191/13-6) thanks Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES – Finance Code 001) for the predoctoral fellowship. J. Martínez-Ortigosa (SEV-2012-0267-02) acknowledges the Severo Ochoa Program for a predoctoral fellowship. We gratefully acknowledge the ALBA synchrotron for allocating beamtime (proposals 2016021665 and 2017032119), CLÆSS beamline staff, and particularly Carlo Marini for their help and technical support during our experimen