Benzenesulfonic Acid Groups Research Articles

Sulfonation of ordered mesoporous carbon supported Pd catalysts for formic acid electrooxidation

A novel supporting material containing benzenesulfonic acid (BSA) groups and ordered mesoporous carbons (OMCs) was first prepared by in situ radical polymerization of 4-styrenesulfonate and isoamyl nitrite under ambient conditions. Then, Pd nanoparticles were deposited on as-produced OMCs (f-OMCs) by the NaBH 4 reduction method. The structure and nature of the resulting composites were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption–desorption. The results show that BSA groups are created and the texture and surface chemistry are altered, whereas the ordered porous structure is maintained. The electrocatalytic properties of the Pd/f-OMCs catalysts for formic acid oxidation (HCOOH) have been investigated by cyclic voltammetry and chronoamperometry methods, and excellent electrocatalytic activity can be observed.

A comparative study of solid sulfonic acid catalysts based on various ordered mesoporous silica materials

Acid catalysts based on ordered mesoporous silica materials (MCM-41, HMS, and SBS-15) with covalently anchored propanesulfonic or benzenesulfonic acid groups were synthesized. Six samples were prepared by co-condensation of tetraethylorthosilicate with 3-mercaptopropyltrimethoxysilane or phenyltriethoxysilane in the presence of appropriate templating agents. Six other samples were made by post-synthesis modification of the parent silica materials. Syntheses were followed by oxidation or sulfonation to form surface sulfonic acid groups. Sample characterization was performed by physical (low-angle X-ray powder diffraction, nitrogen adsorption and desorption, diffuse reflectance IR, Raman, NMR, and X-ray photoelectron spectroscopies) and chemical (acid–base titration) methods. Spectroscopic techniques proved successful incorporation of the functional groups. Functionalization of the parent silicas, however, results in changes in structural characteristics (decreasing BET surface areas, changes in pore size distribution, decreasing long range orders). The samples exhibit high activities in various catalytic transformations. Catalysts with anchored benzenesulfonic acid groups of high acid strength and high acid site densities allow the selective synthesis of the cyclic dimer indan product in the dimerization of 2-phenylpropene. 2,3,5-Trimethylhydroquinone diacetate can also be produced in similar high yields in the rearrangement–aromatization of ketoisophorone. Characteristic differences in selectivities are interpreted by taking into account of differences in acid site densities, active site distribution, and the polarity of reactants and catalyst surface. The low activity and selectivity of samples made by grafting in the transformation of ketoisophorone are attributed to the non-random distribution of the acidic functions.

Estimation of the dissociation constants for functional groups on modified and unmodified silica gel supports from the relationship between electroosmotic flow velocity and pH.

Electroosmotic volume flow was directly observed in a simple instrument consisting of 1 cm long a home-made support, packed between two polyethylene frits in the polypropylene tube. Equations relating electroosmotic flow (EOF) velocity and pH for two functional groups on the surface of the solid materials were developed. With these equations, we can estimate the dissociation constants of two different kinds of functional groups on modified silica gel materials simultaneously. The dissociation constants of silanol groups, benzene sulfonic acid groups, and alkyl quaternary ammonium groups on the modified and unmodified silica gel supports were estimated. The estimated pK values of the silanol groups on the silica gel and modified silica gel surfaces are between 4.0 and 4.3. The estimated pK values of the benzene sulfonic acid groups and alkyl quaternary ammonium groups on the surface of the modified silica gel are 2.6 and 8.6, respectively.

Structural effect of polymeric acid dopants on the characteristics of doped polyaniline composites

The structure and doping behaviors of poly( p-styrene sulfonic acid) (PSSA)-doped polyaniline (PANi) and poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS)-doped PANi were investigated by conductivity measurement, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The conductivities of the PSSA-doped PANi composites are higher by up to two orders of magnitude than those of the PAMPS-doped PANi composites of the same composition, given by acid-to-aniline ratio. The confinement of pendant benzene sulfonic acid groups in the PSSA and that of pendant amino methyl propane sulfonic acid groups in the PAMPS may result in non-uniform and inefficient doping, such that some of the acid groups are not able to participate in the doping. The conductivity difference between the two different polymeric acid-doped PANi composites can be explained by the difference in the degree of the steric hindrance between the two polymeric acid dopants. The PSSA-doped and PAMPS-doped PANi systems reveal the same optimum composition of 1 1 (moles of sulfonic acid units in the polymeric acids/moles of aniline units in PANi) for maximum conductivity. The maximum conductivity seems to be attributed to the increase in the doping level and the decrease in the order and packing density of the PANi subchain alignment with increase of the acid-to-aniline ratio.

Preparation and characterisation of N-substituted aniline with aniline

We report the chemical synthesis of polyaniline copolymers containing N-substituted benzenesulfonic acid groups using (NH 4) 2S 2O 8 in HCl. The copolymer compositions have been studied by a wide range of techniques and related to their conductivities and solubilities.

Silver ion chromatography using solid-phase extraction columns packed with a bonded-sulfonic acid phase.

Commercial solid-phase extraction columns packed with a stationary phase with bonded benzenesulfonic acid groups are readily converted to the silver ion form and can then be used for silver ion chromatography of lipids. To illustrate the utility of such procedures, methyl ester derivatives of fatty acids with zero to six double bonds were separated from each other by a simple stepwise elution scheme. -Christie, W. W. Silver ion chromatography using solid-phase extraction columns packed with a bonded-sulfonic acid phase.