Structure of MCM-48 Revealed by Transmission Electron Microscopy

Alfredsson, Viveka; Anderson, Michael W.

doi:10.1021/cm950568k

Cited by 248 publications

(191 citation statements)

References 19 publications

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“…In case of siliceous MCM-48 sample (Fig. 1a), strong reflections observed in between 2θ = 2 to 3° in addition to several weak reflection in the range of 2θ = 3 to 7° indicates the formation of ordered mesoporous structure [27]. Similar patterns in the small angle XRD patterns were noticed after incorporation with cobalt ( Fig.…”

Section: Methodssupporting

confidence: 70%

Catalytic Conversion of Lignin: Studies on Oxidation of Lignin Model Phenolic Monomer over CoMCM-41 and CoMCM-48 Catalysts

Sadual¹,

Badamali²

2018

Asian J. Chem.

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INTRODUCTIONLignin is an integral component of plants and is most abundant aromatic biopolymer in earth which can serve as a renewable resource of chemical feedstock. It is suggested that catalytic oxidation of lignin or lignin derived fragments is interesting as it is expected to yield functionalized chemicals which can be employed in fine chemical synthesis [1]. In this subject, several reports have been appeared in literature largely focused on catalytic reactions of lignin model compounds which could provide useful information for the development of selective and high yield processes of lignin oxidation namely the conversion of lignin to aromatic monomers catalyzed by triflic acid [2], depolymerization of oxidized lignin to aromatics by formic acid [3], oxidation of phenolic and non-phenolic compounds in presence of metal chlorides in ionic liquid medium [4] are some of the significant achievements in the area of lignin valorization. Among the lignin model phenolic monomers, apocynol, 1-(4-hydroxy-3-methoxyphenoxy)-ethanol is commonly studied over many catalysts. Recently, much attention is focussed on the catalytic oxidation of lignin derived fragments to fine chemicals. Wozniak et al. [5] have studied the liquid phase oxidation of apocynol over potassium nitrosodisulfonate (Fremy's salt) and corresponding benzo- The present study focussed on investigation of the potentiality of cobalt containing mesoporous material (M41S) as a robust heterogeneous catalyst for the oxidation of lignin model phenolic compound. Cobalt containing MCM-41 and MCM-48 were prepared under hydrothermal condition and characterized by various spectroscopic and analytical techniques. Formation of well ordered hexagonal and cubic mesopore structures of MCMs, containing cobalt in the silicate framework was inferred from XRD, TG-DTA and N2 adsorption-desorption studies. DR UV-visible spectral analysis revealed existence of Co(II) and Co(III) in the tetrahedral framework. The oxidative ability of CoMCMs were studied for the lignin model phenolic monomer, 1-(4-hydroxy-3-methoxyphenoxy)-ethanol, under mild conditions using environmentally benign H2O2 as the oxidant. The catalytic results showed that under optimum reaction conditions, apocynol undergoes selective oxidation yielding 2-methoxybenzoquinone and acetovanillone. CoMCM-41 was found to be more selective towards acetovanillone, on the contrary, CoMCM-48 was better catalyst for 2-methoxybenzoquinone yield.

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Section: Methodssupporting

confidence: 70%

Catalytic Conversion of Lignin: Studies on Oxidation of Lignin Model Phenolic Monomer over CoMCM-41 and CoMCM-48 Catalysts

Sadual¹,

Badamali²

2018

Asian J. Chem.

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“…CMK-1 is prepared by using MCM-48 as the parent silica phase, [17] thus, the backtransformation of CMK- 1 to an ordered mesoporous ZnO II should lead to pore sizes similar to those for MCM-48. [22] As the BJH pore-size distributions show (see Figure 6b), this is indeed the case, as the average pore size of the resulting mesoporous ZnO material is 3.8 nm, although the distribution is somewhat broader than in the case of siliceous MCM materials. The use of CMK-1 as a template allows the surface area of the resulting nanoporous ZnO II material to increase even further to 202 m 2 g À1 (BET).…”

mentioning

confidence: 65%

Preparation of High‐Surface‐Area Zinc Oxide with Ordered Porosity, Different Pore Sizes, and Nanocrystalline Walls

Polarz

Orlov

Schüth

et al. 2006

Chemistry A European J

129

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Zinc oxide (ZnO) is attracting tremendous research interest due to its vast spectrum of properties and applications. ZnO is an n-type direct band-gap semiconductor with DE gap = 3.37 eV and an exciton-binding energy of 60 meV. Thus, it possesses properties similar to those of gallium nitride, but it is much easier to prepare. Among the interesting features of ZnO are piezoelectric-and electromechanical-coupling properties, and it has been applied for UVlight-emitting diodes, lasers, in photovoltaic solar cells, in UV-photodetectors, gas-sensors, and for varistors.[1] However, more important for this paper is the pivotal role of ZnO as a component in industrial methanol-synthesis catalysts (Cu/ZnO/Al 2 O 3 ).[2] Methanol is increasing in importance because it is believed to be one key compound in future hydrogen-based energy technologies. [3] Because catalytic activity depends highly on dispersion and surface area, [4] an approach used frequently is to immobilize the respective catalytic system on suitable supports. Ordered mesoporous silica materials, such as MCM-41 or SBA-15, [5,6] have proven to be valuable supports for heterogeneous catalysts, due to their unique nanostructure. [7] Recently, we were able to prepare size-selected ZnO particles in the pores of ordered mesoporous silica materials.[8] The key to success in this preparation was the use of an innovative, organometallic-precursor system resembling ZnO on a molecular scale. [8,9] Due to the potentially large surface area, the idea is very tempting that the nanoporous material itself is composed of a matrix material that is catalytically more relevant than silica. This approach is still rather unexplored, although some success in the synthesis of non-siliceous, ordered mesoporous materials has been made. [6,10,11] The preparation of some transition-metal oxides, especially TiO 2 , in a mesoporous state was achieved by using liquid-crystalline templates.[12] A wider spectrum of materials (e.g., mesoporous MgO) could be accessed by using a thermally and mechanically more robust template, an ordered mesoporous carbon material. [11,13] Although there have been some efforts to synthesize nanoporous ZnO with ordered porosity, [14] to the best of our knowledge, the successful preparation of this interesting material has not yet been reported. One of the problems encountered in previous attempts is the reduction of saltlike ZnO precursor, for instance zinc nitrate, in the course of the thermolytic removal of the template.Here, we present the successful preparation of ordered mesoporous ZnO with high surface area. We compared the two methods of preparation, the true liquid-crystal templating and the exotemplating with mesoporous carbons, and obtained ZnO materials with different pore sizes. In both Abstract: Transition-metal-oxide materials possessing ordered mesoporosity have recently attracted significant research interest due to their numerous potential applications. Among them, ordered mesoporous zinc oxide (ZnO) is a very tempting material because of the ...

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“…MCM-41 possessed a large specific surface area, a hexagonal array, and uniform mesopore channels. MCM-48 had a cubic pore system indexed in the space group Ia3d, and possessed a bicontinuous structure centered on the gyroid minimal surface [2] that divided available pore space into two nonintersecting subvolumes [3,4] The discovery of mesoporous materials offered an opportunity for catalyst supports.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of tungsten-incorporated mesoporous molecular sieve MCM-48 by one step

et al. 2010

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Tungsten-substituted mesoporous MCM-48 materials are successfully synthesized at 393 K by a onestep co-condensation sol-gel method. The prepared samples with different Si/W ratios are characterized by X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), diffuse reflectance UV-visible spectroscopy and FT-IR, and the results indicate the presence and good dispersion of tungsten species inside the silica pores, the Si/W ratio is controlled above 28. When the Si/W ratio is less than 28, though no bulk tungsten is detected outside the MCM-48 mesoporous silica, the pore structure order becomes worse.

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Structure of MCM-48 Revealed by Transmission Electron Microscopy

Cited by 248 publications

References 19 publications

Catalytic Conversion of Lignin: Studies on Oxidation of Lignin Model Phenolic Monomer over CoMCM-41 and CoMCM-48 Catalysts

Catalytic Conversion of Lignin: Studies on Oxidation of Lignin Model Phenolic Monomer over CoMCM-41 and CoMCM-48 Catalysts

Preparation of High‐Surface‐Area Zinc Oxide with Ordered Porosity, Different Pore Sizes, and Nanocrystalline Walls

Synthesis and characterization of tungsten-incorporated mesoporous molecular sieve MCM-48 by one step

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