Friedel–Crafts acylation of anisole over hybrid zeolitic-mesostructured materials

Serrano, David; García, Rafael A.; Otero, D.

doi:10.1016/j.apcata.2009.02.013

Cited by 45 publications

(18 citation statements)

References 26 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 Catalysissupporting

confidence: 51%

“…[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 Catalysissupporting

confidence: 51%

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

“…[5] The benefits of hierarchical zeolites have been reported in a wide range of catalyzed reactions, such as aromatization, [6] isomerization, [6,7] oligomerization, [8] esterification, [7] alkylation, [9] acylation, [10] cracking, [7] pyrolysis, [11] methanol conversion, [12] and selective oxidation. [13] In particular, the controlled extraction of framework silicon in existing zeolites, referred to as desilication or base leaching, is a topdown approach to prepare hierarchical porous zeolites.…”

Section: Introductionmentioning

confidence: 99%

Hierarchical ZSM‐5 Zeolites in Shape‐Selective Xylene Isomerization: Role of Mesoporosity and Acid Site Speciation

Fernandéz¹,

Stan²,

Gilson³

et al. 2010

Chemistry A European J

254

185

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The isomerization of o-xylene, a prototypical example of shape-selective catalysis by zeolites, was investigated on hierarchical porous ZSM-5. Extensive intracrystalline mesoporosity in ZSM-5 was introduced by controlled silicon leaching with NaOH. In addition to the development of secondary porosity, the treatment also induced substantial aluminum redistribution, increasing the density of Lewis acid sites located at the external surface of the crystals. However, the strength of the remaining Brønsted sites was not changed. The mesoporous zeolite displayed a higher o-xylene conversion than its parent, owing to the reduced diffusion limitations. However, the selectivity to p-xylene decreased, and fast deactivation due to coking occurred. This is mainly due to the deleterious effect of acidity at the substantially increased external surface and near the pore mouths. A consecutive mild HCl washing of the hierarchical zeolite proved effective to increase the p-xylene selectivity and reduce the deactivation rate. The HCl-washed hierarchical ZSM-5 displayed an approximately twofold increase in p-xylene yield compared to the purely microporous zeolite. The reaction was followed by operando infrared spectroscopy to simultaneously monitor the catalytic performance and the buildup of carbonaceous deposits on the surface. Our results show that the interplay between activity, selectivity, and stability in modified zeolites can be optimized by relatively simple post-synthesis treatments, such as base leaching (introduction of mesoporosity) and acid washing (surface acidity modification).

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“…Due to the presence of medium and strong acid sites, as well as transport mesopores, they exhibit high catalytic activity and stability in the process of cracking [4] and conversion of bulk molecules of organic substances with larger kinetic diameter than zeolite micropores (0.3-1.5 nm), including the processes of alkylation [5], acylation [6], aldol condensation [7], etherification [8].…”

Section: Introductionmentioning

confidence: 99%

“…Using of bifunctional polyammonium surfactants «Gemini-type surfactants» as structure directing agents (templates) with two or more quaternary nitrogen atoms (promoting the zeolite formation) connected with C 3 -C 6 alkyl bridges, as well as with one or two terminal hydrophobic (C 16 -C 22 ) alkyl groups limiting the growth of zeolite crystals and forming a mesostructure is one of the most promising and original approaches for obtaining of micro-mesoporous materials of zeolite type [9,10]. Using this method the analogues of a number of known zeolites (MFI, BEA, MOR, FAU and others) with so-called hierarchical porosity, different morphology (nanoparticles [11], nanolayers [9], nanorods [12]), structural and sorption characteristics inherent to zeolites and mesoporous molecular sieves (MMS), in particular-significant predominance of relatively large mesopores with diameter of 5-15 nm [11,13] and high (up to 0.6) accessibility index of acid sites for large molecules of organic substances [11,14] were obtained.…”

Section: Introductionmentioning

confidence: 99%

Two-stage dual template alkali metal-free synthesis of micro-mesoporous aluminosilicates based on ZSM-5 zeolite precursors

et al. 2016

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Carrying out the dual template synthesis (in the presence of molecular and micellar templates) in the alkali metal-free reaction media (pH 11.7-12) at a relatively lowtemperature hydrothermal treatment (100-120°C, duration 3-5 days) allowed to obtain micro-mesoporous aluminosilicates combining the properties of zeolite ZSM-5 and mesoporous molecular sieve AlSi-MCM-41. X-ray amorphous sol-precursors of ZSM-5 zeolite obtained by preliminary hydrothermal treatment of alkali metal-free reaction mixture at 160°C and containing secondary building units of zeolite were used as initial substances for synthesis of micro-mesoporous aluminosilicates. During the joint formation of the structure of zeolite and mesoporous molecular sieve in one reaction mixture and in contiguous conditions close to optimal for their individual formation, composites zeolite/mesoporous molecular sieve were formed. The structural and sorption characteristics and acidity of the obtained composites differ from mechanical mixture of two phases. X-ray amorphous micro-mesoporous aluminosilicate with secondary building units and precursors of ZSM-5 in mesostructure is characterized by higher concentration and strength of Brønsted and Lewis acid sites as well as a higher catalytic activity in the reaction of cracking of cumene compared to AlSi-MCM-41 of similar composition. This aluminosilicate also exhibits a higher total selectivity toward the major products of reaction, in comparison with ZSM-5.Keywords Micro-mesoporous aluminosilicates Á Dual template alkali metal-free synthesis Á Zeolite ZSM-5 precursors Á The degree of zeolitization Á Structure and sorption properties Á Acidity Á Catalytic cracking of cumene

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Friedel–Crafts acylation of anisole over hybrid zeolitic-mesostructured materials

Cited by 45 publications

References 26 publications

Zeolite Catalysts with Tunable Hierarchy Factor by Pore‐Growth Moderators

Zeolite Catalysts with Tunable Hierarchy Factor by Pore‐Growth Moderators

Hierarchical ZSM‐5 Zeolites in Shape‐Selective Xylene Isomerization: Role of Mesoporosity and Acid Site Speciation

Two-stage dual template alkali metal-free synthesis of micro-mesoporous aluminosilicates based on ZSM-5 zeolite precursors

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