Mesoporous benzene-silica

Fig. 2 Mesoporous benzene-silica with crystal like pore walls. Figures reproduced with the permission of Prof M. Froba [34]...

Remarkably, in 2002, Inagaki and co-workers reported that, starting from 1,2-bis (triethoxysilyl)benzene as a siliceous precursor, mesoporous benzene-silica with crystal-like pore walls (Ph-PMO) can be prepared (Fig. 2) [35]. Owing to their crystallinity, these new hybrid organic-inorganic materials were much more stable in water than the amorphous mesoporous silica-supported sulfonic sites described above [36-39]. 

Q. Yang, M. P. Kapoor, and S. Inagaki, Sulfuric acid-functionalized mesoporous benzene -silica with a molecular scale periodicity in the walls, /. Am. Chem. Soc. 124, 9694-9695 (2002). 

The possible compositions for the walls of the ordered mesoporous materials go beyond the field of inorganic chemistry, and materials with hybrid organosilica walls have been prepared [81-84], Some mesoporous benzene-silica hybrids are stable at a temperature higher than 500 °C [84], Mesoporous materials prepared from polysilazanes and nonionic surfactants can be activated to form silicon carbonilride ceramics, which retain an ordered mesoporosity up to 1500 °C [85],... 

Cho EB, Kim H, Kim D (2009) Effect of morphology and pore size of sulfonated mesoporous benzene-silicas in the preparation of poly(vinyl alcohol)-based hybrid nanocomposite membranes for direct methanol fuel cell application. J Phys Chem B 113 9770-9778... 

Ting, C.C., Chung, C.H., and Kao, H.M. (2011) Direct synthesis of bifunctional periodic mesoporous benzene-silicas functionalized with a high loading of carboxylic acid groups. Chem. Commun., 47, 5897-5899. 

Sulfuric acid-functionalized mesoporous benzene-silica with a molecular-scale periodicity in the walls. /. 

It should be noted that the PVA-based composite/blend membranes generally showed high potential for DMFC applications due to the better methanol barrier capability for PVA itself resulting from the dense molecular packing structure caused by inter- and intramolecular hydrogen bonding. " Kim group developed PVA-based nanocomposites modified with sulfonated mesoporous benzene-silicas and obtained... 

The ordered benzene-silica hybrid material[228] has a hexagonal array of mesopores with a lattice constant of 52.5 A, and crystal-like pore walls that exhibit structural periodicity with a spacing of 7.6 A along the channel direction. The periodic wall structure results from alternating hydrophilic and hydrophobic layers, composed of silica and benzene, respectively. 

Other molecules present in the gas mixtures like alcohols or ketones may have a moderate effect on aromatic oxidation but the reverse (inhibition of alcohol oxidation by aromatics) is most often observed. Different supports of Pt were used for toluene oxidation Al203, Al203/Al, Zn0/Al203, Ti02, mesoporous fibrous silica or monoliths. Zeolites, generally promoted by platinum, were shown to give excellent catalysts for aromatic oxidation. Basic zeolites showed excellent performances in oxidation of m-xylene even in the absence of platinum. Palladium catalysts, either supported on alumina or ceria-alumina, were also investigated for oxidation of benzene and several alkylbenzenes. ... 

Fig. 5.8 Adsorption isotherms at 25°C of benzene and cyclohexane on a mesoporous silica gel. Curve (A), benzene curve (B), cyclohexane. Solid symbols denote desorption.

Zinc chloride was used as a catalyst in the Friedel Crafts benzylation of benzenes in the presence of polar solvents, such as primary alcohols, ketones, and water.639 Friedel-Crafts catalysis has also been carried out using a supported zinc chloride reagent. Mesoporous silicas with zinc chloride incorporated have been synthesized with a high level of available catalyst. Variation in reaction conditions and relation of catalytic activity to pore size and volume were studied.640 Other supported catalytic systems include a zinc bromide catalyst that is fast, efficient, selective, and reusable in the /wa-bromination of aromatic substrates.641... 

The first demonstration, to our knowledge, that the properties of a gas or liquid within a mesoporous cavity change was made by Dosseh et al. studying the properties of cyclohexane and benzene confined in MCM-41 and SBA-15. The effect was related to the influence of the inner surfaces of mesoporous silica. Other authors have further demonstrated the influence of confinement on the adsorption and properties of fluids within an ordered mesoporous material. Flowever, Fajula et were the... 

Figure 2. Separation of (a) benzene, (b) naphthalene, and (c) biphenyl on reverse phase (C8-modified) mesoporous silicas. Left Cg-MCM-48, run conditions 65/35 (v/v%) MeOH/HjO, column pressure 97 bar. Right Cg-APMS run conditions. 65/35 (v/v%) Me0H/H20, column pressure 35 bar. The first peak is due to an impurity.

Benzene hydroxylation to give phenol has been performed with Mo-substituted mesoporous silicas and H2O2 in the absence of solvent (267). However, as explained earlier, reports of anchoring of Mo in an inorganic support must be treated with great caution, particularly if there is no clear concept for immobilizing both Mo and peroxo Mo. The same holds true for the Mo silicalite MoS-1, which has been used for sulfide oxidation with H2O2 (268). 

Adsorption isotherms isotherms of nitrogen (77K) and benzene (31 OK) were measured as previously (9). For the SI sample, the isotherms were of type IV, showing hysteresis loops, corresponding to capillary condensation in the larger mesopores. All the other samples (S2M, S3M and S4M) contained smaller mesopores, and the nitrogen adsorption/desorption isotherms were reversible and sigmoidal in shape. Surface and porous properties of different silica samples (Table 2) were derived fi"om nitrogen adsorption data. 

Figure 1. SANS of evacuated mesoporous Figure 2. Dependence of I(Q) for sample silica, SIM (dp - 6nm). SANS contains two SIM in the Porod Scattering region (at Q = components (a) at low Q - Porod Scattering 10-2A-1) on fractional volume filling of (b) at high Q - Diffraction. mesopores, 0, with matched benzene.

Mesoporous melamine-formaldehyde and phenolic-formaldehyde resins were synthesized in the process of polymerization in the presence of fumed silica as an inorganic template. The surface and structural characteristics of the obtained sorbents were investigated using XPS technique and sorption from gas phase. The parameters characterizing porous structure of the synthesized resins in a dry state were determined from nitrogen adsorption/desorption isotherms. The sorption processes of benzene and water vapor accompanied by simultaneous swelling of both polymers were also studied. 

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