Overgrowth of mesoporous MCM-41 on faujasite

Kloetstra, K. R.; Zandbergen, H.W.; Jansen, J.C.; Bekkum, H. van

doi:10.1016/0927-6513(96)00036-3

Cited by 173 publications

(103 citation statements)

References 17 publications

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“…[ 23 ] In the primary method, the zeolite crystallization can take place either on the external surface [49][50][51][52] of a surfactant assembly or inside. [ 53 , 54 ] Moreover, the secondary methods include the use of surfactants to mediate the assembly of zeolite seeds into mesoporous structures, [ 55 , 56 ] coating zeolite crystals with a thin layer of mesopores with the help of surfactants, [57][58][59] and application of surfactants to swell and exfoliate layered zeolite precursors into delaminated zeolites. [ 60 , 61 ] In addition, methods concerning the synthesis of microporous/mesoporous hierarchical structures using organosilane surfactants containing a hydrophobic tail and a hydrophilic head (structured like a molecular template) also fall under this category.…”

Section: B)mentioning

confidence: 99%

Zeolitic Materials with Hierarchical Porous Structures

et al. 2011

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During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented.

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Section: B)mentioning

confidence: 99%

Zeolitic Materials with Hierarchical Porous Structures

et al. 2011

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“…A primeira metodologia relacionada à obtenção de zeólitas com estrutura hierárquica de poros, por moldagem supramolecular, foi desenvolvida por Kloetstra e colaboradores, 70 que prepararam peneiras moleculares com distribuição de poros bimodal, combinando microporos e mesoporos. O método consistiu na preparação de materiais compósitos micro e mesoporosos através da cristalização simultânea da zeólita FAU e da MCM-41 ou através da deposição de MCM-41 sobre cristais da zeólita FAU.…”

Section: Zeólitas Com Estrutura Hierárquica De Poros Preparadas Via Munclassified

Zeólitas hierarquicamente estruturadas

Grecco¹,

Rangel²,

Urquieta‐González³

2013

Quím. Nova

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Recebido em 5/3/12; aceito em 3/7/12; publicado na web em 26/11/12 HIERARCHICALLY STRUCTURED ZEOLITES. This review presents the main characteristics and properties of microporous (zeolites) and ordered mesoporous materials, focusing on structural aspects and preparation. In addition, their use as heterogeneous catalysts are also discussed, with emphasis on their advantages and disadvantages. Due to difficulty in application of zeolites in the conversion of bulky molecules, the most relevant strategies of synthesis for the preparation of zeolitic materials with hierarchical pore structure was also analyzed, which allow this limitation to be overcome.Keywords: synthesis of zeolites; mesoporous materials; hierarchical porous structure. INTRODUÇÃOAs zeólitas, materiais cristalinos microporosos, têm se consolidado ao longo da segunda metade do século XX e nesta primeira década do século XXI como importantes catalisadores em processos das indústrias de refino de petróleo, química e petroquímica, assim como no controle ambiental.1 Esse amplo espectro de aplicações está relacionado às propriedades físicas e químicas desses materiais, que podem ser controladas durante a sua preparação, visando uma aplicação específica. Além de seu particular sistema de microporos, as zeólitas apresentam propriedades específicas, que as diferenciam de outros materiais, tais como acidez ou basicidade superficial e capacidade de troca iônica.2 Entretanto, apesar dessas propriedades desejáveis, a presença apenas de microporos nas zeólitas impõe limitações à difusão de reagentes ou produtos volumosos. Embora a limitação difusional seja usada, em alguns casos, para controlar beneficamente a seletividade a um determinado produto da reação catalítica, a difusividade relativamente baixa de moléculas volumosas, nos microporos da zeólita, limita a taxa de reação, devido ao transporte mais lento dos reagentes e produtos, ocasionando um maior tempo de residência e, como consequência, favorecendo a ocorrência de reações indesejáveis.3 Em processos envolvendo hidrocarbonetos, a limitação difusional contribui para a formação do coque, que provoca a desativação da zeólita por obstrução dos canais ou envenenamentos dos sítios ativos. 4 Com a expectativa de superar as limitações difusionais, no fim da década de 80 se deu início à busca por materiais contendo mesoporos, que resultou na síntese de materiais mesoporosos ordenados no início dos anos 90.5-8 Diversas peneiras moleculares mesoporosas com tamanho de poros ajustável têm sido desenvolvidas, apresentando emprego potencial em reações catalíticas. Entretanto, comparado às zeólitas, esses materiais mesoporosos possuem acidez e estabilidade hidrotérmica mais baixas, o que limita as suas aplicações catalíticas. Assim, esforços consideráveis têm sido dedicados ao desenvolvimento de materiais zeolíticos com estrutura hierárquica de poros, que combinam as propriedades intrínsecas das zeólitas com a facilidade de difusão resultante da geração de mesoporosidade.Um número significativo de procedimentos experime...

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“…It has been recognized that hierarchical pore structure that combines the advantages of both mesoporous materials and microporous zeolites can offer attractive features and circumvent the problems aforementioned. 9,10 There have been several successful examples regarding the synthesis of such hierarchical porous materials, such as by compositing mesoporous materials with zeolites 11,12 and by creating mesoporosity in zeolite crystals. 13,14 Nevertheless, the diffusion path length in the micropore channels of these composite materials is still quite long for diffusion-limited reactions, 15 because of the bulky and separate nature of microporous zeolites in these composite materials.…”

Section: Introductionmentioning

confidence: 99%

Bimodal micro‐mesoporous aluminosilicates for heavy oil cracking: Porosity tuning and catalytic properties

et al. 2008

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in Wiley InterScience (www.interscience.wiley.com).Through a two-step synthesis procedure, bimodal micro-mesoporous aluminosilicates, denoted as B-MASs, were synthesized by assembling preformed zeolite Y nanoclusters using a triblock polymer as template. By controlling the aging conditions of preformed zeolite nanoclusters the porosity of the B-MASs was suitably tuned. The characterization results showed that the pore walls of the mesoporous phase in the B-MASs consist of zeolite Y nanoclusters and the microporosity of the B-MASs is inherited from the incorporated nanoclusters. It was suggested that more incorporation of the well-developed zeolite nanoclusters accounts for the increasing microporosity of the B-MASs with the increasing aging temperature of the preformed zeolite nanoclusters. The incorporated nanoclusters have much shorter pore channels and mainly contribute weak Lewis acid sites to the B-MASs. The resulting bimodal micro-mesoporous materials B-MASs with mutually connected mesopores and shorter micropores showed superior catalytic properties when used for cracking heavy crude oil.

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Overgrowth of mesoporous MCM-41 on faujasite

Cited by 173 publications

References 17 publications

Zeolitic Materials with Hierarchical Porous Structures

Zeolitic Materials with Hierarchical Porous Structures

Zeólitas hierarquicamente estruturadas

Bimodal micro‐mesoporous aluminosilicates for heavy oil cracking: Porosity tuning and catalytic properties

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