Preparation of Tetramethylguanidine-Functionalized Mesoporous Silica as a Catalyst for the Epoxidation of Electron Deficient Alkenes

A heterogeneous guanidine catalyst, based on 1,1,3,3-tetramethylguanidine was prepared by functionalisation of a glycidylpropyl group previously attached to hexagonal mesoporous silica. The catalyst was characterized by various techniques including Diffuse Reflectance FTIR, 13C NMR, elemental analysis and simultaneous thermogravimetric and differential scanning calorimetry analyses. It was then screened in the epoxidation of electron deficient alkenes. The results obtained show that indeed the intended moiety was attached onto silica surface at a loading of 0.4 mmol per g silica. The parent silica had a surface area of 1511 m2 g-1 which decreased to 1275 m2 g-1 upon functionalisation. The catalyst was active and highly selective in epoxidation of electron deficient alkenes, giving yields up to 60% within 12 hours. The reusability of the catalyst was however limited, calling for further investigation.Tanz. J. Sci. Vol. 37 2011, 156-16

Synthesis of organoamine-silica hybrids using cashew nut shell liquid components as templates for the catalysis of a model Henry reaction

Organoamine-silica hybrids were prepared by a co-condensation of tetraethoxysilane (TEOS) and different aminoalkoxysilanes, namely, 3-aminopropyltrimethoxysilane, N-(3(trimethoxysilyl)propyl)-ethylenediamine and 3[2(2-amino)ethylamino]propyl trimethoxysilane, at different ratios using cashew nut shell liquid (CNSL) components as templates. Of the major components of CNSL tested, only cardanol was found to be efficient as a template as it yielded 66% of the hybrid. The prepared materials were characterized by diffuse reflectance Fourier Transform Infrared (FTIR), Atomic Force Microscopy and acid titration. Results indicated that indeed the organoamine groups were attached onto the silica surface, with a maximum loading of 2.9 mmol organic group per g silica. The materials were found to be very active as catalysts in a model Henry reaction, with yields ranging from 81% to 98%. The catalytic efficiency was found to depend on the type of template, amount of loading, type of aminoalkoxysilanes incorporated onto the silica framework and the ratio of aminoalkoxysilane to TEOS.Key words: Organoamine-silica hybrids, micelle templated silica, cashew nut shell liquid

Wet Oxidation of Maleic Acid by a Pumice Supported Copper (II) Shiff Base Catalyst

Pumice supported Cu (II) Schiff base catalysts were prepared by surface chemical modification followed by complexation with Cu (II) acetate. The resulting materials were characterised by Diffuse Reflectance Fourier Transform Spectroscopy (DRIFTS) to confirm the modification. The materials were tested in a wet oxidation of maleic acid using air or hydrogen peroxide as an oxidant. Results indicate that up to 80% degradation of maleic acid could  be achieved in the presence of the catalyst using hydrogen peroxide as an oxidant. The degradation was found to depend on the type of oxidant, temperature and whether the parent pumice was acid pre-treated or not prior to the preparation of the catalyst.Keywords: Supported Cu (II) Schiff base, maleic acid degradation, pumic

Preparation and characterization of activated carbons from rice husks and shells of palm fruits

Activated carbons from palm fruit shells (PFS) and rice husks (RH) were prepared using physical and chemical activation processes, respectively. The influence of activation time and temperature (in the case of PFS) and impregnation ratio and carbonization temperature (in the case of RH) on the properties of the resultant carbons were studied. In the case of PFS carbons, there were an increase in adsorption capacity and surface areas with increase in activation time and temperature. The surface area ranged between 292 and 642 m2g-1 at temperature range of between 1000 and 1200 K. In the case of RH carbons, surface areas and adsportion capacity also increased with increase in impregnation ratio and carbonization temperature. However, at temperatures above 1100 K there was a decrease in both surface area and adsorption capacity. The surface areas ranged between 146 m2g-1 and 526 m2g-1 at a temperature range of 1000 to 1100 K for the later carbons. Tanz. J. Sci. Vol. 28(2) 2002: 131-14