Insights to Achieve a Better Control of Silicon-Aluminum Ratio and ZSM-5 Zeolite Crystal Morphology through the Assistance of Biomass

Silva, Alessandra V.; Miranda, Leandro S. M.; Nele, Márcio; Louis, Benoît; Pereira, Marcelo Maciel

doi:10.3390/catal6020030

Cited by 16 publications

(10 citation statements)

References 35 publications

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“…Interparticle variations in Brønsted acidity can account for the variation in catalytic performance they however do not explain the differences in crystal appearance in SEM. The observed surface roughness could be an indication of particle imperfections and the presence of defects and extra‐framework porosity . To visualize the extra‐framework porosity with the same amount of detail, we specifically stained the accessible pore‐mouths of the straight microporous ZSM‐5 channels using a large fluorescent molecule, that is, 4‐(4‐diethylaminostyryl)‐ N ‐methylpyridinium iodide (DAMPI) .…”

Section: Figurementioning

confidence: 77%

“…Shown in Figure S1 (Supporting Information) is a magnified view on the three types of crystals. Such large differences in catalytic activity can be explained by either a variation in acid site density and strength or by differences in accessibility of acid sites for example, owing to the presence of extra‐framework porosity, which induces surface roughness …”

Section: Figurementioning

confidence: 98%

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Assessing Inter and Intra‐particle Heterogeneity in Alumina‐poor H‐ZSM‐5 Zeolites

et al. 2017

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We reveal the presence of significant variations in Brønsted catalytic activity within and between individual H-ZSM-5 zeolite crystals. Fluorescence microscopy in combinationw ith a fluorogenic probe was used to resolve the catalytic activity at the nanoscale. The observed variations in catalytic activity could be directly linked to structural parameters and crystal morphology observed in scanninge lectron microscopy and by specifically stainingc rystal defects. The obtained resultsa re directly comparedw ith ensemblea veraged information from techniques such as pyridine IR spectroscopy and nitrogen physisorption, typically used to characterize acid zeolites. The inter-and intra-particle heterogeneities resolved by the employed fluorescence approach remainu naddressed by bulk characterization. Our experimental resultsr elate the heterogeneous catalytic activity to variation in both the Si/Al ratio and mesoporosity inducedd uring the zeolite synthesis.The preparation of zeolite-based industrial catalysts usually involves mixingt he zeolitesw ith silicaa nd or aluminab inders in order to dilute the zeolite properties and to obtain the desired throughput. [1][2][3] During this process it is assumed that the zeolite crystalsthemselves are homogeneous in nature, [2,4,5] that is, only small variations in properties between the zeolite crystals in ab atch exist. However,i fthis assumption is wrong and large variations in, for example, acid site density are present, parts of the shaped catalystc ould become more active than others,r esulting in undesired coke formation and thus al oss in catalystactivity and lifetime. [4,6,7] Twop arameters impacting catalyst activity are the number and strength of acid sites present in az eolite. These are directly relatedt ot he framework Al content, [8,9] hence Al determination is often used to assess zeolite acidity.S everalt echniques can be used to determine the Si/Al ratio, yielding powder averaged information, for example, elemental analysisu sing inductive coupled plasma (ICP), [10,11] magic angle spinning (MAS) 29 Si and 27 Al NMR, [8,12] laser induced break down spectroscopy (LIBS), [13] X-ray photon electron spectroscopy (XPS) [12,14] and time of flight-secondary ion mass spectrometry (TOF-SIMS). [15,16] All of theset echniques lead to the determination of the 'bulk" scale acidity and some are even able to obtain single crystal information given that crystal sizes and aluminum content are sufficiently large; [17] for example, single crystal X-ray diffraction [17,18] and energy dispersive X-ray spectroscopy (EDX) coupled to electron microscopy potentially with focused-ion-beam milling. [14,19] In summary,t he acidic properties of zeolitesa re often deduced indirectly from the aluminum content.F urther,n oi nformation regarding site accessibility is obtained in these results. Direct measurements of acid site density and strengtha re possible via temperature programmed desorption (TPD) [8,14,20] and infrared- [2,21,22] or Raman spectroscopy [23] using basic probe molecules such...

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Section: Figurementioning

confidence: 77%

Section: Figurementioning

confidence: 98%

Assessing Inter and Intra‐particle Heterogeneity in Alumina‐poor H‐ZSM‐5 Zeolites

et al. 2017

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“…For example, Che et al investigated three pure polysaccharides (starch, sucrose, and cellulose) to increase the mesopore volume in hierarchical ZSM-5 for catalytic biomass pyrolysis . Pretreated biomass and functionalized biopolymer were also found to be capable of directing unprecedented nanostructures and properties in hierarchical ZSM-5. , Such attempts to introduce a new template are impactful because the properties of the template are closely linked to the physicochemical characteristics in the synthesized zeolite . Concurrently, further studies on the relationships between physicochemical characteristics and catalyst performance are required for using the hierarchical ZSM-5 reassembled with potential green templates in catalytic co-pyrolysis.…”

Section: Introductionmentioning

confidence: 99%

Lignin-Mediated Preparation of Hierarchical ZSM-5 Catalysts and Their Effects in the Catalytic Co-pyrolysis of Softwood Biomass and Low-Density Polyethylene Mixtures

Lei

Zhao

Villota

et al. 2021

ACS Sustainable Chem. Eng.

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Biomass-mediated modification in zeolite synthesis has outstanding potential in directing new porous structures and improved catalyst properties. This study reports the preparation of hierarchical ZSM-5 catalysts by a successive treatment of desilication and lignin-mediated reassembly. The changes in physicochemical properties of the hierarchical ZSM-5 including crystallinity, porosity, acidity, and morphology were characterized by foreseeing the application of lignin as a green template. The hierarchical pore system containing moderately strengthened acidity was directed with 1 wt % lignin addition, which attained more desirable products and less solid residue than the microporous ZSM-5. The catalytic conversion of biomass and plastic feedstocks was performed using analytical and bench-scale reactor systems to evaluate desired mixtures and product distribution. It was found that the surface and intracrystalline mesopores in hierarchical ZSM-5 were beneficial for the conversion of macromolecules, such as aromatic oxygenates and long-chain hydrocarbons. While the plastic-derived olefins synergistically interacted with the biomass derivatives within the pyrolytic vapor, the hierarchical structure extended reactant accessibility from the catalyst surface into the microporous channels and internal acid sites.

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“…Indeed, ingenious organic templates (typically cationic surfactants) render these syntheses not yet applicable for large-scale industry [34]. There are, however, tendencies to replace these expensive templates by bio-sourced cheaper mesoporogens [35,36]. Thus, it remains interesting to explore and compare both routes.…”

Section: Introductionmentioning

confidence: 99%

Mesoporous ZSM-5 Zeolites in Acid Catalysis: Top-Down vs. Bottom-Up Approach

et al. 2017

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Abstract:A top-down desilication of Al-rich ZSM-5 zeolites and a bottom-up mesopores creating method were evaluated in this study. Three liquid-solid and one gas-solid heterogeneously-catalysed reactions were chosen to establish relationships between zeolites textural properties and their catalytic behavior in acid-catalysed model reactions that are influenced by shape selectivity: Diels-Alder cyclization between isoprene and methylacrylate, Methanol-to-Olefins (MTO) reaction, chlorination of iodobenzene with trichloroisocyanuric acid (TCCA), and Friedel-Crafts acylation of anisole by carboxylic acids with differing sizes. It is found amongst others that no optimal mesoporosity for all the different reactions can be easily obtained, but depending on the chosen application, a specific treatment has to be set to achieve high activity/selectivity and stability.

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Insights to Achieve a Better Control of Silicon-Aluminum Ratio and ZSM-5 Zeolite Crystal Morphology through the Assistance of Biomass

Cited by 16 publications

References 35 publications

Assessing Inter and Intra‐particle Heterogeneity in Alumina‐poor H‐ZSM‐5 Zeolites

Assessing Inter and Intra‐particle Heterogeneity in Alumina‐poor H‐ZSM‐5 Zeolites

Lignin-Mediated Preparation of Hierarchical ZSM-5 Catalysts and Their Effects in the Catalytic Co-pyrolysis of Softwood Biomass and Low-Density Polyethylene Mixtures

Mesoporous ZSM-5 Zeolites in Acid Catalysis: Top-Down vs. Bottom-Up Approach

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