Catalytic performance of carbonaceous materials in the esterification of succinic acid

Mesoporous carbonaceous materials have outstanding potential in many different applications such as adsorption, medicine and catalysis. We have recently reported the synthesis of a new form of mesoporous carbon, named Starbon((R)), obtained after low temperature carbonization of expanded starch. Such starch-derived mesoporous materials have several tunable properties including surface energies (ranging from hydrophilic to hydrophobic surfaces), which can be easily controlled by the degree of carbonization (from 200 to 700 degrees C). Due to the diversity of surface functional groups, Starbons((R)) can be easily chemically modified. Treatment of Starbon((R)) materials with sulfuric acid gave a solid acid that has promising properties as heterogeneous catalyst. Comparative catalytic studies with some other similar commercial carbonaceous materials such as DARCO((R)) and NORIT (R), as well as phosphorous-containing microporous carbons, are reported. (c) 2008 Elsevier B.V. All rights reserved

A Sweet Killer: Mesoporous Polysaccharide Confined Silver Nanoparticles for Antibacterial Applications

Silver nanoparticles (AgNP) confined within porous starch have been prepared in a simple, green and efficient manner, utilising the nanoporous structure of predominantly mesoporous starch (MS) to act as nanoparticle stabiliser, support and reducing surface. MS/AgNP materials present high surface areas (SBET > 150 m2 g−1) and mesopore volumes (Vmeso > 0.45 cm3 g−1). The interaction of the AgNP precursor and forming nanoparticle nuclei with the mesoporous domains of the porous polysaccharide, direct porosity to increasingly narrower and more defined pore size distributions, indicative of a degree of cooperative assembly. Transmission electron microscopy images indicated the presence of spherical AgNP of a size reflective of the porous polysaccharide mesopore diameter (e.g., 5–25 nm), whilst XPS analysis confirmed the metallic Ag0 state. Materials were prepared at relatively low Ag loadings (<0.18 mmol g−1), demonstrating excellent antimicrobial activity in solid and liquid phase testing against Gram negative (E. coli) and positive (S. aureus) model bacteria. The resulting materials are biocompatible and present a useful solid porous carbohydrate-based polymer vehicle to control the AgNP size regime and facilitate transference to a biological environment

Synthesis, Immobilization and Catalytic Activity of a Copper(II) Complex with a Chiral Bis(oxazoline)

A chiral bis(oxazoline) bearing CH2OH groups was synthesized from a commercial bis(oxazoline) and characterized by H-1- and C-13-NMR, high resolution ESI-mass spectrometry and FTIR. The corresponding copper(II) complex was immobilized onto the surface of a mesoporous carbonaceous material (Starbon (R) 700) in which the double bonds had been activated via conventional bromination. The materials were characterized by elemental analysis, ICP-OES, XPS, thermogravimetry and nitrogen adsorption at 77 K. The new copper(II) bis(oxazoline) was tested both in the homogeneous phase and once immobilized onto a carbonaceous support for the kinetic resolution of hydrobenzoin. Both were active, enantioselective and selective in the mono-benzoylation of hydrobenzoin, but better enantioselectivities were obtained in the homogeneous phase. The heterogeneous catalyst could be separated from the reaction media at the end of the reaction and reused in another catalytic cycle, but with loss of product yield and enantioselectivity

The Influence of Carrier on the Critical Phenomena in CO Oxidation over NiO

The influence of thermo-exfoliated graphite (TEG) on the catalytic activity of nickel in the CO oxidation process has been investigated. It was shown that nickel supported on the thermo-exfoliated graphite surface was more active catalytically than the bulk metal. Alternate oxidation–reduction on the Ni–NiO phase boundary occurred at temperatures higher than 633 K (Curie temperature of pure nickel). Using a magnetogravimetric method, it was found that the nickel catalyst was transformed by the reaction mixture into a heterophase (Ni/NiO) system both in the presence of a carrier and in its absence. Hence the carrier did not influence the size of the Ni particles. The high catalytic activity of the catalyst supported on graphite may be explained by an increase in the number of Ni particles. Ni/TEG and Ni/NiO samples were studied via X-ray diffraction, Auger spectroscopy and electron microscopy methods

Influence of the Donor Properties of Silica-immobilized Amines on the Thermodynamic Characteristics of Interfacial Protolytic Reactions

The thermodynamic characteristics of the reaction between amino groups covalently bonded to a silica surface and aqueous solutions of a strong acid were calculated. Data concerning the influence of the surface on the properties of the bonded amino groups and also about the interaction between neighbouring amines were obtained. The characteristics of the protonation process were explained in terms of a bonded layer structure

The Hydrophobisation of Activated Carbon Surfaces by Organic Functional Groups

A technique of hydrophobic surface design with a high degree of structural homogeneity has been developed for catalytic materials. Mesoporous activated carbons and silica gel were modified by (A) treatment with vinyltrimethoxysilane (vtms) or (B) chlorination with carbon tetrachloride followed by reaction with a Grignard reagent. Evidence for silica gel modification was obtained from FT-IR and 13 C NMR spectroscopy and from elemental analysis. Carbons chemically modified with alkanes and olefins were studied using thermogravimetry (TG) and the results compared with those for the modified silica gel. TG and differential scanning calorimetry (DSC) revealed that the polymerisation of vinyl groups occurred on the carbon surface. The participation of the carrier surface in the initiation of radical processes has been discussed