Assembly of Hydrothermally Stable Aluminosilicate Foams and Large-Pore Hexagonal Mesostructures from Zeolite Seeds under Strongly Acidic Conditions

Liu, Yu; Pinnavaia, Thomas J.

doi:10.1021/cm0109544

Cited by 191 publications

(92 citation statements)

References 8 publications

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“…After then, multi-step synthesis strategies for assembling preformed zeolite seeds into a mesoporous structure were proposed in order to prevent the separate formation of zeolite and mesoporous silica [61][62][63][64]. In a modified method, Naik et al performed steam-assisted crystallization (i.e., dry-gel synthesis) of zeolite seeds that were preassembled by surfactants [65].…”

Section: Soft-templating Routementioning

confidence: 99%

Hierarchically Nanoporous Zeolites and Their Heterogeneous Catalysis: Current Status and Future Perspectives

Somorjai

2014

Catal Lett

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The research field of hierarchically nanoporous zeolites has been growing at an enormous pace over the past decades. Hierarchically nanoporous zeolites have versatile structural properties such as high surface area and large pore volume that can alleviate diffusional limitations of conventional zeolites with solely microporous framework. In this review, various synthesis strategies to hierarchically nanoporous zeolites and their structural advantages in catalytic reactions will be reviewed. In the first part, many novel synthetic approaches for hierarchically nanoporous zeolites such as post-demetallation, softtemplating, hard-templating, and dual-pore-generating surfactant-directed methods will be introduced. In the second part, catalytic applications of hierarchically nanoporous zeolites on various chemical reactions involving isomerization, cracking, alkylation and oxidation will be discussed. The present comprehensive review will provide future opportunities and perspectives on the research of hierarchically nanoporous zeolites including their applications to catalytic reactions.

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Section: Soft-templating Routementioning

confidence: 99%

Hierarchically Nanoporous Zeolites and Their Heterogeneous Catalysis: Current Status and Future Perspectives

Somorjai

2014

Catal Lett

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“…Pore wall thickness in the samples ranged between 4.3 and 5.4 nm which are also close to the value observed above and reported for the parent SBA-15. 18 The sizes of subunits in zeolite precursors are reported to be in the range of 1-3 nm. It is therefore conceivable that these subunits can be accommodated within the SBA-15 porewalls of the dimensions observed.…”

Section: Methodsmentioning

confidence: 99%

“…In addition to basic and neutral conditions, the seeding concept was extended to incorporating FAU, ZSM-5, Beta, and silicalite (an all-silica member of MFI family) structural subunits in the pore walls of SBA-15 by adding the respective zeolite precursor into SBA-15 synthesis mixtures under acidic conditions. [18][19][20][21][22] In the case of Al-SBA-15 synthesis from zeolite Y precursor, results reported by Pinnavaia and coworkers indicate that strong acidic conditions (pH <2) should be avoided, and mild acid conditions (pH 4-6.5) was necessary to prevent the decomposition of the zeolite Y precursor and the solublization of Al. 18 The resulting materials obtained by these researchers had low surface areas (< 650 m 2 /g), but showed significant steam stability compared to the parent SBA-15, and good activity for acid catalyzed cumene conversion.…”

Section: Iv-1 Backgroundmentioning

confidence: 99%

“…[18][19][20][21][22] In the case of Al-SBA-15 synthesis from zeolite Y precursor, results reported by Pinnavaia and coworkers indicate that strong acidic conditions (pH <2) should be avoided, and mild acid conditions (pH 4-6.5) was necessary to prevent the decomposition of the zeolite Y precursor and the solublization of Al. 18 The resulting materials obtained by these researchers had low surface areas (< 650 m 2 /g), but showed significant steam stability compared to the parent SBA-15, and good activity for acid catalyzed cumene conversion. In this communication, we report that by using an alternative strategy to synthesize the seed precursor and combining the reactants, Al-SBA-15 catalysts were produced with higher surface areas, and the Al was stabilized in total tetrahedral coordination upon high temperature calcinations.…”

Section: Iv-1 Backgroundmentioning

confidence: 99%

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Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

Ingram¹,

Mitchell²

2006

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Al-SBA-15 mesoporous catalysts with strong Brönsted acid sites and Al stabilized in a totally tetrahedral coordination was synthesized from the addition of hydrothermally aged zeolite Y precursor to SBA-15 synthesis mixture under mildly acidic condition of pH 5.5. The materials possessed surface areas between 690 and 850 m 2 /g, pore sizes ranging from 5.6 to 7.5 nm and pore volumes up 1.03 cm 3 , which were comparable to parent SBA-15 synthesized under similar conditions. Up to 2 wt. % Al was present in the most aluminated sample that was investigated, and the Al remained stable in totally tetrahedral coordination, even after calcination at 550˚C.The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. The catalyst's activity was not affected by the aging time of the precursor for up to the 24 hr aging time investigated. This method of introducing Al and maintaining it in a total tetrahedral coordination is very effective, in comparison to other direct and post synthesis alumination methods reported. The catalytic performance of the zeolite Y/SBA-15 composite materials will be compared with that of pure SBA-15. The catalysts will then be evaluated for the conversion of heavy petroleum feedstocks.3 Table of Contents I ABSTRACT 2

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“…Several research groups have attempted to use tiny zeolite precursors or secondary building units of synthetic zeolites as starting materials for the preparation of mesoporous materials [3][4][5][6][7][8][9]. Mesoporous materials with moderate acidic properties originated from zeolite precursors have been synthesized from nanoclusters of zeolite Y, zeolite Beta and ZSM-5 [3][4][5][6]9]. Synthesis of hydrothermally stable mesoporous molecular sieves from zeolite mordenite and zeolite L were also reported [7,8].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of MCM-41 with Zeolite-P from Natural Clinoptilolite for Silica-alumina Source Under Hydrothermal Conditions in Alkaline Media

Shindo

Nagai

Ikeuchi

et al. 2011

Int.J.Soc.Mater.Eng.Resour.

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Mesoporous molecular sieve MCM-41 and zeolite-P were synthesized from natural clinoptilolite zeolite and cetyltrimethylammonium bromide under hydrothermal conditions in alkaline media. The formation path of MCM-41 and zeolite-P from natural clinoptilolite was investigated using XRD, TG, SEM, and FT-IR for the samples obtained in the course of the synthesis. XRD and TG results exhibited that in the first stage where the mixture of clinoptilolite and cetyltrimethylammonium bromide was treated in alkaline media at ambient temperature, crystal structure of clinoptilolite did not change significantly. In the second stage where the mixture was subsequently treated under hydrothermal conditions, dissolution of clinoptilolite and formation of zeolite-P were observed, while mesophase with 2d hexagonal structure of MCM-41 was not detected. In the third stage, mesostructure with 2d hexagonal symmetry was gradually formed by the adjustment of pH of the reaction mixture between 10.5 and 8.5. Structural integrity of 2d hexagonal assembly of as-synthesized MCM-41 was improved by controlling pH of the reaction mixture to 8.5 followed by the hydrothermal treatment. In contrast, the structure of zeolite-P was not affected by these treatments. SEM images of the samples showed that small particles of MCM-41 were mainly formed on the surface of the zeolite-P particles and agglomerated to larger grains. Judging from the results of XRD patterns and FT-IR spectra of the samples, it is indicated that smaller crystallites or building units of clinoptilolite that were X-ray amorphous and IR detectable were probably incorporated in the pore walls of MCM-41.

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Assembly of Hydrothermally Stable Aluminosilicate Foams and Large-Pore Hexagonal Mesostructures from Zeolite Seeds under Strongly Acidic Conditions

Cited by 191 publications

References 8 publications

Hierarchically Nanoporous Zeolites and Their Heterogeneous Catalysis: Current Status and Future Perspectives

Hierarchically Nanoporous Zeolites and Their Heterogeneous Catalysis: Current Status and Future Perspectives

Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

Synthesis of MCM-41 with Zeolite-P from Natural Clinoptilolite for Silica-alumina Source Under Hydrothermal Conditions in Alkaline Media

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