Sulfonated silica

Zhang, M., Yang, C., and Ziad, E. R., Capillary electrochromatography with novel stationary phases. 3. Retention behavior of small and large nucleic acids on octadecyl-sulfonated-silica, Anal. Chem., 71, 3277, 1999. 

This method is certainly the oldest one described in the literature the first example concerns the ion exchange of [Pt(NH3)4]2+ and the surface of a sulfonated silica.15 Even now, the preparation of many heterogeneous catalysts (i.e., supported metal or oxide particles) involves as the first step the reaction of a coordination complex with the surface of an ionic solid such as alumina,... 

Purine and pyrimidine bases and their nucleosides (adenosine, adenine, cytidine, cytosine, guanosine, guanine, inosine, thymine, uridine, uracil) ODSS (octadecyl sulfonated silica), 10 pm Acetonitrile . 8 mM sodium acetate, pH 4.5 (40 60) 270 mm x 20.5 pm i.d 205 mm effective lengtl... 

Su et al. [138] prepared composite PEMs from sulfonated poly(phthalazinone ether ketone) (sPPEK) and various amounts of sulfonated silica nanoparticles (silica-SO3H). The use of silica-SO H was seen to compensate for the reduction in the lEC of the membrane, while the strong -SO3H/-SO3H interaction between sPPEK chains and silica-SO3H particles led to ionic crosslinking in the membrane structure, which improved not only the thermal stability but also the methanol resistance. 

Type of reaction C-S bond formation Reaction condition solvent-free Keywords sulfonation, silica sulfuric acid... 

The sulfonated silica catalysts were characterised by powder XRD. The HMS-SO3H X-ray diffraction patterns were dominated by the 100 reflections corresponding to a dioo spacing of about 3.6 nm in each of the three samples. The SBA-I5-SO3H patterns also showed intense reflections from 100 planes with a spacing of 9.4 nm. In both cases the patterns were similar to those reported in the literature. ... 

Table Acidity and catalytic data for sulfonated polystyrenes and sulfonated silicas...

In Figure lb similar plots are shown for the sulfonated silica catalysts. The profiles are very different to those of the resins. They do not show the abrupt decreases at coverages equivalent to the known concentrations of acid sites. In fact, all four catalysts exhibit a steadily falling differential enthalpy of adsorption as coverage increases. In each case, it drops below 80 kJ mol (as an arbitrary indicator of the saturation of acid sites) at coverages well below the known concentrations of surface acid sites given in the Table, and there is only a weak correlation between the coverage at which it drops to this level and the acid site concentration. 

The reason for this relatively inconclusive data on acidity of the dry sulfonated silicas is most likely that these materials, with high surface areas compared to the resins, interact with ammonia through physisorption at the same time as chemisorption on acid sites. Each point on the profile is a weighted average of the two types of interaction, with physisorption becoming increasingly dominant as coverage increases. 

A typical microcalorimeter output is shown in Figure 2 for an aqueous NaOH titration of a sulfonated silica. The molar enthalpy of neutralisation is essentially constant throughout the neutralisation and a precise value for the molar enthalpy of neutralisation can be obtained from the linear plot of cumulative enthalpy against added base. 

Activities are reported in the Table as initial rates per mole of acid group, or initial turnover numbers. In the case of the resins, higher rates were recorded for the powdered than the bead resins, and the data shown is for the powdered materials. This suggests that, when in bead form, the reaction is largely under diffusion control (through the swollen gel). It is not possible to estimate the extent to which the reaction is still under diffusion control when the catalyst is powdered. However, the consistent pattern of rates for the sulfonated resins and the sulfonated silicas that appears in the Table suggests that kinetic control dominates in both catalysts under the conditions used. 

The turnover numbers, or specific rates, of the sulfonated silicas are all similar and within experimental error of each other. This suggests that all acid sites are readily accessible, and diffusion rates to the sites are not rate limiting, in both HMS supported catalysts with relatively narrow pores, and SBA-15 where the pores are very much larger. On this basis the catalytic activities of the all acid groups in both sulfonated HMS and sulfonated SBA-15 are essentially constant. 

The activities of the resins with low levels of sulfonation are similar to those of the sulfonated silicas, again suggesting that the acid groups are readily accessible and exhibit the same specific activity. A very significant difference is seen however, for resins with higher levels of sulfonation. Sulfonic acid groups on these catalysts are evidently very much more active than those on the silicas and those on the resins with acid concentrations. 

Zhang, M. and El Rassi, Z., Capillary electrochromatography with novel stationary phases II. Studies of the retention behavior of nucleosides and bases on capillaries packed with octadecyl-sulfonated-silica microparticles, Electrophoresis, 20, 31, 1999. 

Chem. Descrip. Zinc sulfonate, silica carrier... 

Sulfonated silica/carbon nanocomposites are also known to be an effective catalyst for cellulose hydrolysis [147], with their hybrid structure influencing catalytic activity. Increasing the silicaicarbon ratio enhanced the turnover frequency, suggesting that hydrophilic silica groups fadlitate substrate adsorption. 

Van de Vyver S, Peng L, Geboers J, Schepers H, de Clippel F, Gommes CJ, Godeiis B, Jacobs PA, Sels BF (2010) Sulfonated silica/carbon nanocomposites as novel catalysts for hydrolysis of cellulose to glucose. Green Chem 12(9) 1560-1563... 

Poly(vinylidene fluoride) (PVDF) membranes, on the other hand, have much better chemical and thermal stabilities than PSSA, but is not a proton conducting polymer. A composite membrane of polyvinylidene fluoride -hexafluoropropyl ene (PVDF-HFP) with sulfonated silica was prepared [485] with proton conductivity up to 40 mS.cm and good relative selectivity (fi, >3), which delivers 43 mW.cm in a DMFC at 80 °C. However, the most studied PVDF composites membranes, are those prepared with PSSA [486—488], poly(2-acrylamido-2-methyl propylene sulfonic acid) (PAMPS) [489]. 

Yen CY, Lee CH, Lin YF, Lin HL, Hsiao YH, Liao SH, Chuang CY, Ma CCM (2007) Sol-gel derived sulfonated-silica/Nafion composite membrane for direct methanol fuel cell. J Power Sources 173 36 14... 

Lee CH, Min KA, Park HB, Hong YT, Jung BO, Lee YM (2007) Sulfonated poly(arylene ether sulfone)-silica nanocomposite membrane for direct methanol fuel cell (DMFQ. J Membr Sci 303 258-266... 

Proton exchange membranes (PEM) were also prepared by solution blending of sulfonated poly(phthalazinone ether ketone) (sPPEK) and various amotmts of sulfonated silica nanoparticles (silica-SOsH) [58]. The solution blending techiuque was also used in combination with compression molding thus, poly(ether ether ketone) (PEEK)-based nanohybrids were fabricated by means of compression molding at 400°C under a pressure of 60 MPa using silica surface-modified with stearic acid and PEEK [59]. 

Su Y, Liu Y, Sun Y, Lai J, Wang D, Gao Y, Liu B, Guiver M (2007) Proton exchange membranes modified with sulfonaled silica nanoparticles for direct methanol fuel cells. J Membr Sd 296(l-2) 21-28... 

Figure 4.40 Separation of aikaiine-earth metals on a sulfonated silica-based cation exchanger. Separator column Nucleosil 5 SA eluent 3.5 mmol/L oxalic acid -I- 2.5 mmol/L ethylenediamine -l-50mL/L acetone, pH 4 ...

Gomes D, Buder I, Nunes SP (2006) Sulfonated silica-based electrolyte nanocomposite membranes. J Polym Sci Pol Chem 44 2278-2298... 

Suryani, Liu YL (2009) Preparatirut and properties of nanocomposite membranes of polybenzi-midazole/sulfonated silica nanoparticles for proton exchange membranes. J Membr Sci 332 121-128... 

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