Synthesis and characterization of mesoporous mordenite

Li, Xianfeng; Prins, R.; Bokhoven, Jeroen A. van

doi:10.1016/j.jcat.2009.01.001

Cited by 198 publications

(127 citation statements)

References 37 publications

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“…The hierarchical zeolites desilicated in the presence of quaternary ammonium cations are superior since their transport efficiency is equivalent to that of QA 0 and, additionally, a higher number of active Brønsted sites are available because of their higher micropore volume. This result stresses the huge improvement margin of hierarchical zeolites reported in the literature, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] as they have not been subjected to optimization. The EB selectivity was higher in the QA x samples (>97%) than in the parent zeolite (90%).…”

Section: Transport and Catalysismentioning

confidence: 60%

“…[5] Enhanced accessibility [8,9] and diffusion [10][11][12][13] of probe molecules were quantified in these hierachical zeolites in comparison with their purely microporous counterparts. The improved molecular transit in the hybrid micro-/mesoporous material had beneficial effects on the activity, selectivity, and/or stability in a wide range of catalyzed reactions, for instance, aromatization, [14] isomerization, [14,15] oligomerization, [16] esterification, [15,17] alkylation, [13,18,19] acylation, [20] cracking, [15,17] pyrolysis, [21,22] methanol conversions, [23,24] selective oxidation, [25] hydrodesulfurization, [26] and in the synthesis of relatively bulky molecules for the pharmaceutical, fragrance, and agrochemical industries. [27] An assorted variety of methods (bottom-up or top-down, template-assisted or not) are presently available to prepare hierarchical porous zeolites in the form of nanosized crystals, [28] composites, [29] and mesoporous crystals.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Zeolite Catalysts with Tunable Hierarchy Factor by Pore‐Growth Moderators

Pérez‐Ramírez

Verboekend

Bonilla

et al. 2009

Adv Funct Materials

472

221

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The design of hierarchical zeolite catalysts is attempted through the maximization of the hierarchy factor (HF); that is, by enhancing the mesopore surface area without severe penalization of the micropore volume. For this purpose, a novel desilication variant involving NaOH treatment of ZSM‐5 in the presence of quaternary ammonium cations is developed. The organic cation (TPA+ or TBA+) acts as a pore‐growth moderator in the crystal by OH−‐assisted silicon extraction, largely protecting the zeolite crystal during the demetallation process. The protective effect is not seen when using cations that are able to enter the micropores, such as TMA+ Engineering the pore structure at the micro‐ and mesolevel is essential to optimize transport properties and catalytic performance, as demonstrated in the benzene alkylation with ethylene, a representative mass‐transfer limited reaction. The hierarchy factor is an appropriate tool to classify hierarchically structured materials. The latter point is of wide interest to the scientific community as it not only embraces mesoporous zeolites obtained by desilication methods but it also enables to quantitatively compare and correlate various materials obtained by different synthetic methodologies.

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Section: Transport and Catalysismentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Zeolite Catalysts with Tunable Hierarchy Factor by Pore‐Growth Moderators

Pérez‐Ramírez

Verboekend

Bonilla

et al. 2009

Adv Funct Materials

472

221

View full text Add to dashboard Cite

show abstract

“…8) is a frequently employed test reaction in the liquid phase. 35,36,38,39 Due to the presence of bulky intermediates or substrates, the additional (meso-)porosity is expected to boost the performance of the zeolite-based catalyst. The improved performance of the hierarchical zeolites compared to the respective parent materials is ascribed to the introduced mesoporosity, facilitating the transport to the active sites.…”

Section: Friedel-crafts-alkylation Of Aromaticsmentioning

confidence: 99%

Catalytic test reactions for the evaluation of hierarchical zeolites

2016

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Catalytic test reactions for the evaluation of hierarchical zeolitesStudies on the synthesis, characterization and catalytic performance of hierarchical zeolites and related porous materials are currently revitalizing the mature field of zeolite research. This review discusses the challenges in evaluating the catalytic performance of a hierarchical zeolite catalyst compared to its parent zeolite. zeolites and the facilitated access and transport in the additional meso-or macropore system. In this tutorial review, we discuss several test reactions that have been explored to show the benefit of the hierarchical pore system with respect to their suitability to prove the positive effects of hierarchical porous zeolites. It is important to note that positive effects on activity, stability and less frequently selectivity observed for hierarchically structured catalysts not necessarily are only a consequence of the additional meso-or macropores but also the number, strength and location of active sites as well as defects and impurities. With regard to these aspects, the test reaction has to be chosen carefully and potential changes in the chemistry of the catalyst have to be considered as well. In addition to the determination of conversion, yield and selectivity, we will show that the calculation of the activation energy and the determination of the Thiele modulus and the effectiveness factor are good indicators of the presence or absence of diffusion limitations in hierarchical zeolites compared to their parent materials. Key learning pointsHierarchical zeolites are an emerging technology in the mature field of industrial catalysts. Several test reactions are suggested to prove the advantage of their hierarchical structure. In addition to an increase in activity and selectivity suppression of coke formation is often observed. Concept of the Thiele modulus and the effectiveness factor is required to judge the presence of diffusion limitations in hierarchical catalysts.

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“…Usually, this behavior is assigned to improved mass transfer due to the introduction of a secondary mesoporous network of inter-or intra-crystalline nature. Indeed, hierarchically porous zeolites offer enhanced accessibility and transport of molecules to and from the active sites [5][6][7][8], therefore enhancing catalyst effectiveness [1][2][3][4]9]. It is of utmost importance to be able to characterise and to guarantee good pore connectivity in order to take benefits from those advantages [10][11][12][13].…”

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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Synthesis and characterization of mesoporous mordenite

Cited by 198 publications

References 37 publications

Zeolite Catalysts with Tunable Hierarchy Factor by Pore‐Growth Moderators

Zeolite Catalysts with Tunable Hierarchy Factor by Pore‐Growth Moderators

Catalytic test reactions for the evaluation of hierarchical zeolites

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

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