Mesoporous synthesis

Vartuli J C, Roth W J, Beck J S, McCullen S B and Kresge C T 1998 The synthesis and properties of M41S and related mesoporous materials Moiecuiar Sieves Science and Technoiogy vol 1, ed FI G Karge and J Weitkamp (Berlin Springer) pp 97-119... 

SYNTHESIS AND PROTOLYTIC PROPERTIES OF THE PERIODICALLY ORDERED MESOPOROUS ORGANOSILICAS WITH MCM-41-TYPE ARCHITECTURES FUNCTIONALISED... 

The mesoporous ordered silicas of different type represent the new generation of materials with unique properties. The discovery of these materials became basis for creation of new catalysts, adsorbents, sensors and supporter for other molecules. The most important way of the modifying physical and chemical properties of mesopurous silicas consist in organic components incorporation on the silica surface as part of the silicate walls or their insertion within channels of the mesopores. This ensured that interest in synthesis and study of functionalized mesoporous materials shai ply grew. In spite of it, these materials are studied insufficiently. 

I 6 Oxidation Tools in the Synthesis of Catalysts and Related Functional Materials Table 6.1 Detemplation approaches of micro- and mesoporous materials. 

Controlled and selective combustion of components via thermal or chemical routes Calcination. Thermal detemplation of organic templates in micro- and mesoporous materials. Chemical detemplation protocols. Solution combustion synthesis... 

For L=NH3 (1) and L=Pr2NH (3), the isotherms are of type II as expected for non-porous materials [27]. Sample 2 shows a significant uptake at 0.6

narrow particle-size distribution which results in a more regular packing with interparticle pores of size similar to that of the particles [27]. The latter shows that the ligand-assisted synthesis does not only allow one to affect the total surface area and particle size, but also the size distribution which is an important tool for tailoring the particle properties. 

CNFs, preparai by proper choice of foe synthesis conditions, were supported palladium and used for CTA hjfoogenation. Results indicated that Pd/CNF catalysts behave satisfectorily. The conversion of 4-CBA reached 98.3% with our novel Pd/CNF catalyst, while 90% with commercial Pd/C under similar evaluation conditions. This may attribute to foe unique mesoporous structure of CNF support r ucing foe diflusion resistance. 

Synthesis, eharacterization and catalytic activity of titanium containing mesoporous materials with TS-1 wall structure... 

Titanium containing hexagonal mesoporous materials were synthesized by the modified hydrothermal synthesis method. The synthesized Ti-MCM-41 has hi y ordered hexa rud structure. Ti-MCM-41 was transformed into TS-l/MCM-41 by using the dry gel conversion process. For the synthesis of Ti-MCM-41 with TS-1(TS-1/MCM-41) structure TPAOH was used as the template. The synthesized TS-l/MCM-41 has hexagonal mesopores when the DGC process was carried out for less than 3 6 h. The catalytic activity of synthesized TS-l/MCM-41 catalysts was measured by the epoxidation of 1-hexene and cyclohexene. For the comparison of the catalytic activity, TS-1 and Ti-MCM-41 samples were also applied to the epoxidation reaction under the same reaction conditions. Both the conversion of olefins and selectivity to epoxide over TS-l/MCM-41 are found hi er flian those of other catalysts. 

The pore size of most zeolites is <1.5nm. This microporosity limits their utility in most areas of chemistry, where the molecules used are much larger, and for which mesoporous materials would be necessary. Unfortunately, attempts to use larger template molecules in the zeolite synthesis, an approach which should in theory lead to larger pore size zeolites, have met with very little success. Indeed, some zeolitic materials have been prepared which have mesopores - none of these has ever displayed any real stability and most collapse on attempts to use them. A new methodology was thus required. 

Commercial porous ceramic tubes (SCT /US Filter Membralox Tl-70 [7]) were used in this study as support for the zeolite material. They are made (Figure 1) of three consecutive layers of tnacroporous a-Al203 with average pore sizes decreasing from the external to the internal layer. A thin toplayer made of mesoporous y-Al203 was also present in some samples. For gas permeability, gas separation and catalytic measurements the tubes were first sealed at both ends with an enamel layer before zeolite synthesis. Tubes with porous lengths up to 20 cm were used in this study. 

Keywords Catalyst synthesis Hybrid inorganic/organic Mesoporous ... 

The mechanical incorporation of active nanoparticles into the silica pore structure is very promising for the general synthesis of supported catalysts, although particles larger than the support s pore diameter cannot be incorporated into the mesopore structure. To overcome this limitation, pre-defined Pt particles were mixed with silica precursors, and the mesoporous silica structures were grown by a hydrothermal method. This process is referred to as nanoparticle encapsulation (NE) (Scheme 2) [16] because the resulting silica encapsulates metal nanoparticles inside the pore structure. 

Template Synthesis and Catalysis of Metal Nanoclusters in Ordered Mesoporous Silicas... 

Zeolites have ordered micropores smaller than 2nm in diameter and are widely used as catalysts and supports in many practical reactions. Some zeolites have solid acidity and show shape-selectivity, which gives crucial effects in the processes of oil refining and petrochemistry. Metal nanoclusters and complexes can be synthesized in zeolites by the ship-in-a-bottle technique (Figure 1) [1,2], and the composite materials have also been applied to catalytic reactions. However, the decline of catalytic activity was often observed due to the diffusion-limitation of substrates or products in the micropores of zeolites. To overcome this drawback, newly developed mesoporous silicas such as FSM-16 [3,4], MCM-41 [5], and SBA-15 [6] have been used as catalyst supports, because they have large pores (2-10 nm) and high surface area (500-1000 m g ) [7,8]. The internal surface of the channels accounts for more than 90% of the surface area of mesoporous silicas. With the help of the new incredible materials, template synthesis of metal nanoclusters inside mesoporous channels is achieved and the nanoclusters give stupendous performances in various applications [9]. In this chapter, nanoclusters include nanoparticles and nanowires, and we focus on the synthesis and catalytic application of noble-metal nanoclusters in mesoporous silicas. 

Recently, Somorjai reported the hydrothermal synthesis of SBA-15 in the presence of PVP-stabilized Pt nanoparticles [22]. This is a one-step synthesis of composites of metal nanoparticles and mesoporous silica. 

Figure 3. Schematic representation of the selective synthesis of metal nanowires and nanoparticles by the Sintering Controlled Synthesis approach, (a) Mesoporous silica, (b) impregnation of mesoporous silica with metal ions, (c) addition of water/alcohol vapors and UV-irradiation, or wet H2-reduction, (d) formation of metal nanowires, (e) dry H2-reduction, (f) formation of metal nanoparticles.

Similarly, monometallic Rh, Pd, and Au and bimetallic Pt-Rh and Pt-Pd nanowires were prepared in FSM-16 or HMM-1 by the photoreduction method [30,33,34]. The bimetallic wires gave lattice fringes in the HRTEM images, and the EDX analysis indicated the homogeneous composition of the two metals. These results show that the wires are alloys of Pt-Rh and Pt-Pd. Mesoporous silica films were also used as a template for the synthesis of uniform metal particles and wires in the channels [35,36]. Recently, highly ordered Pt nanodot arrays were synthesized in a mesoporous silica thin film with cubic symmetry by the photoreduction method [37]. The... 

Synthesis and Characterization of RhPt Nanoparticles in Mesoporous Silica... 

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