Mesoporous template

Preparation and physisorption characterization of D-glucose-templated mesoporous silica sol-gel materials. Chemistry of Materials, 11, 2023-2029. 

The synthesis of carbon templated mesoporous tin MFI catalysts with different Si/Sn was carried out using microwave and in typical synthesis methodology TEOS, TPAOH, [Sn(C5H70)2]2]Cl2, ethanol and water were employed where the molar composition of the reaction mixture was 0.06 TPAOH 0.67 H20 0.028 TEOS 1.3 g EtOH X mg of tin precursor (X = 85, 63, 42, 21 mg). This synthesis mixture was stirred for 90 min at room temperature and then Black pearl 2000 carbon (10% wt. of TEOS) was added and again stirred for 4 h vigorously. The crystallization of C-meso-Sn-Silicalite was performed in a Teflon cup placed in a microwave oven (MARS-5, CEM, maximum power of 1200 W). 

Immobilizing DENs within a sol-gel matrix is another potential method for preparing new supported catalysts. PAMAM and PPI dendrimers can be added to sol-gel preparations of silicas " and zinc arsenates to template mesopores. In one early report, the dendrimer bound Cu + ions were added to sol-gel silica and calcined to yield supported copper oxide nanoparticles. Sol-gel chemistry can also be used to prepare titania supported Pd, Au, and Pd-Au nanoparticle catalysts. Aqueous solutions of Pd and Au DENs were added to titanium isopropoxide to coprecipitate the DENs with Ti02. Activation at 500°C resulted in particles approximately 4 nm in diameter. In this preparation, the PAMAM dendrimers served two roles, templating both nanoparticles and the pores of the titania support. 

M. C. Rogers, B. Adisa, and D. A. Bruce, Synthesis and characterization of dendrimer-templated mesoporous oxidation catalysts, Catal Lett. 98,29-36 (2004). 

Di Renzo, F., Cambon, H., and Dutarte, R. (1997) A 28-year-old synthesis of micelle-templated mesoporous silica. Microporous Mater., 10, 283-286 Chiola, V., Ritsko, J.E., and Vanderpool, C.D. (1971) Process for producing low-bulk density silica. US Patent 3,556,725, assigned to Sylvania Electric Products, Inc. 

In the following section, we restrict our discussion to templated mesoporous solids that are of potential interest as battery electrodes, including many transition-metal oxides and carbon. This slice of the literature still points the interested reader to many articles on the synthesis and physical characterization of relevant mesoporous materials. A much smaller number of electrochemical studies with templated mesoporous electrodes have been published, and these studies in particular will be noted. 

A novel approach to polymer-template mesoporous molecular sieves... 

Many studies that have focused on the formation mechanism of various types of templated mesoporous materials have been summarized in a number of recent reviews,46 9 and it is still an ongoing topic of research.50 51 Here, we want to recapitulate only very briefly the useful interaction classification scheme between the surfactants (S) and the inorganic species (I), which was suggested by Huo et al.52,53... 

Figure 18.1 (a) Examples of surfactant types used to template mesoporous and mesostructured... 

Ying, J. Y., Mehnert, C. P. and Wong, M. S. Synthesis and applications of supramo-lecular-templated mesoporous materials, Angew. Chem. Int. Ed., 1999, 38, 56-77. 

Derrien, A., Renard, G. and Brunei, D. Guanidine linked to micelle-templated mesoporous silicates as base catalyst for transesterification. Stud. Surf. Sci. Catal., 1998,117, 445-452. 

Soler-Illia GJdAA, Crepaldi EF, Grosso D, Sanchez C. Block copolymer-templated mesoporous oxides. Current Opinion in Colloid Interface Science. 2003 8(1) 109—126. 

Catalysts and catalytic supports are often formulated from aluminas owing to their low cost, and their thermal, chemical and mechanical stability [27], To this end, nonionic surfactant templating with polyethylene oxide surfactants was used to synthesize mesoporous alumina [28], Partially ordered mesoporous materials with wormhole channels were obtained - this seems to be a characteristic of templating with nonionic surfactants. Cationic surfactants have recently been found to template mesoporous aluminum oxide with pore sizes that could be fine-tuned by varying the molar ratio of the reactants [29]. The material obtained was thermally stable to 900 °C and exhibited a narrow pore size distribution. 

Soler-Illia, G., Crepaldi, E. L., Grosso, D. and Sanchez, C. (2003). Block copolymer-templated mesoporous oxides. Curr. Opin. Colloid Interface Sci. 8(1), 109-126. 

Cauvel, A., Brunei, D., and Di Renzo, F., Hydrophobic and hydrophilic behavior of micelle-templated mesoporous silica, Langmuir, 13, 2113, 1997. 

Templated mesoporous silica materials have been discovered by Kresge et al. in 1992 [ 1,2]. S ince then, efforts have been made to produce by direct co-condensation synthesis hybrid materials functionalized by different types of reactive groups. 

J.Y. Ying, C.P. Mehnert, M.S. Wong, Synthesis and Applications of Supramolecular-Templated Mesoporous Materials , Angew. Chem. Int. Ed., 38,56 (1999)... 

Relatively few studies on the synthesis of mesoporous alumina have been reported to date [8]. One of the limitations of the reported synthetic strategies is that the rate of hydrolysis (and condensation) reaction of aluminum alkoxide are much faster than that of silicon alkoxide. In this study, we proposed a novel method to prepare bimodal porous aluminas with meso- and macropores with narrow pore size distribution and well-defined pore channels. The fiamewoik of the porous alumina is prepared via a chemical templating method using alkyl caiboxylates. Here, self-assemblied micelles of carboxylic acid were used as a chemical template. Mesoporous aluminas were prepared through carefiil control of the reactants pH, while the procedures are reported elsewhere [9]. 

The resulting mesoporous layers don t usually exhibit extraporosity at a larger scale, but as smaller pores in the oxide walls (Figure 25.24). ° Due to limitations associated with intrinsic mesostructure characteristics, anisotropy resulting from preferential orientations, or boundaries between ordered domains, the tem-plated mesoporosity is usually not directly interconnected. " In such situations, it does directly define the selectivity of the membrane, which depends on the pore size of the oxide walls. However, the resulting hierarchical porosity (templated mesopores and smaller pores of the oxide walls) favors a decrease in layer permeability. The templated mesoporosity can also be used to functionalize the membrane. 

J. Y. Ying, C. P. Mehnert, M. S. Wong "Synthesis and applications of supramolecular-templated mesoporous materials" Angewandte Chemie, 1999, Vol.38, No.l-2,pp.56-77... 

Ying JY, Mehnert CP, Wong MS (1999) Synthesis and appheations of supramolecular-templated mesoporous materials. Angew Chem Int Ed 38 56... 

Figure 1. Schematic pathway for preparing surfactant-templated mesoporous silicas, illustrating a formation mechanism based on preformed liquid crystal (LC) mesophase (route A) or a cooperative process (route B). Reprinted from [20], Copyright (2008) WILEY-VCH Verlag GmbH Co.

This is where the synthesis of nano-sized molecular sieves is carried out in the template matrix within confined spaces. This is an ideal synthetic route if the space size and uniformity favor the crystallization, and the as-synthesized product is easily isolated from the templates. Mesoporous molecular sieves with uniform mesopore structures can be adopted as the template, such as MCM-41. In 2000, Schmidt et al.[127] first proposed such a route to synthesize ZSM-5 nanocrystals. The synthesis procedure consisted of the impregnation of mesoporous carbon black with reaction solution, followed by treatment with steam at 150 °C, and the combustion of carbon black. Compared with other methods, the advantage of this one is that the nano-sized product is easily isolated and the yield is relatively higher. However, it also has some drawbacks. First, there is a high requirement for the preparation of carbon black as the template matrix, i.e., the mesopore sizes in carbon black must be uniform. Second, the crystallization must be performed in the mesopores, not on the extra surfaces of the carbon black. Third, a large amount of carbon black will be consumed (about four-times that of the nanozeolite product). All of these factors affect the further development of this route to some degree. 

Zhao[266] demonstrated the successful synthesis of highly ordered mesoporous silicon carbides with unusually high surface areas (430-720 m2/g), uniform pore sizes (<3.5 nm), and extremely high thermal stabilities (up to 1400 °C) replicated by mesoporous silica hard templates via a one-step nanocasting process. Highly ordered 2-D hexagonal (p6m) and bicontinuous cubic (Ia3d) SiC nanowire arrays have been cast from the hard templates, mesoporous silica SBA-15 and KIT-6, respectively. 

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