Direct Observation of Nanorange Ordered Microporosity within Mesoporous Molecular Sieves

Li, Jun; Zhang, Xiaodan; Han, Yu; Xiao, Feng‐Shou

doi:10.1021/cm0103951

Cited by 78 publications

(70 citation statements)

References 24 publications

(58 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We suggest that these mesostructural patterns may result from the special properties of the fluorocarbon-hydrocarbon surfactant mixtures at high temperature and are currently under investigation in our laboratory. Moreover, unlike most ordered mesoporous materials that are extremely vulnerable to heating and electron radiation, [23] JLU-20 is not damaged even under relatively strong current density for a long time (over 30 min). This is another indication that JLU-20 possesses unusual stability.…”

Section: Transmission Electron Microscopy (Tem)mentioning

confidence: 99%

High‐Temperature Synthesis of Stable Ordered Mesoporous Silica Materials by Using Fluorocarbon–Hydrocarbon Surfactant Mixtures

Han

Song

et al. 2004

Chemistry A European J

View full text Add to dashboard Cite

Highly ordered hexagonal mesoporous silica materials (JLU-20) with uniform pore sizes have been successfully synthesized at high temperature (150-220 degrees C) by using fluorocarbon-hydrocarbon surfactant mixtures. The fluorocarbon-hydrocarbon surfactant mixtures combine the advantages of both stable fluorocarbon surfactants and ordered hydrocarbon surfactants, giving ordered and stable mixed micelles at high temperature (150-220 degrees C). Mesoporous JLU-20 shows extraordinary stability towards hydrothermal treatment (100 % steam at 800 degrees C for 2 h or boiling water for 80 h), thermal treatment (calcination at 1000 degrees C for 4 h), and toward mechanical treatment (compressed at 740 MPa). Transmission electron microscopy images of JLU-20 show well-ordered hexagonal arrays of mesopores with one-dimensional (1D) channels and further confirm that JLU-20 has a two-dimensional (2D) hexagonal (P6 mm) mesostructure. 29Si HR MAS NMR spectra of as-synthesized JLU-20 shows that JLU-20 is primarily made up of fully condensed Q4 silica units (delta=-112 ppm) with a small contribution from incompletely cross-linked Q3 (delta=-102 ppm) as deduced from the very high Q4/Q3 ratio of 6.5, indicating that the mesoporous walls of JLU-20 are fully condensed. Such unique structural features should be directly attributed to the high-temperature synthesis, which is responsible for the observed high thermal, hydrothermal, and mechanical stability of the mesoporous silica materials with well-ordered hexagonal symmetry. Furthermore, the concept of "high-temperature synthesis" is successfully extended to the preparation of three-dimensional (3D) cubic mesoporous silica materials by the assistance of a fluorocarbon surfactant as a co-template. The obtained material, designated JLU-21, has a well-ordered cubic Im3m mesostructure with fully condensed pore walls and shows unusually high hydrothermal stability, as compared with conventional cubic mesoporous silica materials such as SBA-16.

show abstract

Section: Transmission Electron Microscopy (Tem)mentioning

confidence: 99%

High‐Temperature Synthesis of Stable Ordered Mesoporous Silica Materials by Using Fluorocarbon–Hydrocarbon Surfactant Mixtures

Han

Song

et al. 2004

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…However, M41S materials generally exhibit weak acidity and low hydrothermal stability due to their amorphous frameworks. As a consequence, new synthesis strategies have been developed to obtain materials which com-bine the advantages of mesoporous materials and those of zeolites [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. For example, Corma et al [21] reported a post-synthesis dealumination process via steaming or acid leaching on full-grown zeolites.…”

Section: Introductionmentioning

confidence: 99%

“…Over the last couple of years, several simple and reliable approaches have been developed to form micro/mesoporous combined materials using zeolite nanoparticles or zeolite seeds as the silica source [31][32][33][34][35][36]. However, most of the published reports on composite catalysts have focused on one-dimensional materials (such as MCM-41 or SBA-15) as the mesostructured component, although three-dimensional materials, such as cubic MCM-48, are more interesting from the viewpoint of catalysis due to the interwoven pore system, which allows the sufficient diffusion of reactants within the pores, subsequently leading to a better catalytic performance [37].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of Pd/ZSM-5/MCM-48 biporous catalysts with superior activity for benzene oxidation

Cheng

et al. 2010

Applied Catalysis A: General

View full text Add to dashboard Cite

a b s t r a c t ZSM-5/MCM-48 composite materials with different acidities and enhanced thermal stability have been synthesized via a simple and reliable in situ overgrowth method. The as-prepared biporous materials and the Pd-impregnated catalysts were systematically investigated by various techniques, including XRD, ICP-OES, N 2 adsorption/desorption, H 2 chemisorption, SEM, TEM/HRTEM, FT-IR, 27 Al MAS NMR, NH 3 -TPD, H 2 -TPR and XPS. The characterization results reveal that all composite catalysts exhibit high surface area, large pore volume and long pore diameter. The quantity of acid sites increases as the ZSM-5 additive amount increases, and Al atoms are in the tetrahedral coordination positions in composite materials. The activity tests demonstrate that all the Pd-loaded catalysts are active in the total elimination of benzene, while the catalytic activity values of Pd-loaded ZSM-5/MCM-48 composite catalysts are much higher than those of Pd/ZSM-5 or Pd/MCM-48 alone. Both Pd 0 and Pd 2+ are responsible for the oxidation reaction, and the catalytic activities are primarily related to the support acidity and the Pd dispersion. In addition, the stability of the composite catalysts also improves with an appropriate amount of ZSM-5 additives in MCM-48. This research shows that the novel Pd-loaded composite catalysts are promising materials in the elimination of VOCs.

show abstract

“…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%

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

Ingram¹,

Mitchell²

2006

View full text Add to dashboard Cite

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

show abstract

Direct Observation of Nanorange Ordered Microporosity within Mesoporous Molecular Sieves

Cited by 78 publications

References 24 publications

High‐Temperature Synthesis of Stable Ordered Mesoporous Silica Materials by Using Fluorocarbon–Hydrocarbon Surfactant Mixtures

High‐Temperature Synthesis of Stable Ordered Mesoporous Silica Materials by Using Fluorocarbon–Hydrocarbon Surfactant Mixtures

Synthesis and characterization of Pd/ZSM-5/MCM-48 biporous catalysts with superior activity for benzene oxidation

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

Contact Info

Product

Resources

About