On the location of different titanium sites in Ti–OMS-2 and their catalytic role in oxidation of styrene

Octahedral manganese oxide molecular sieves (OMS-2) modified by impregnation of TiO₂ exhibit a higher catalytic activity for oxidation of styrene with tert-butylhydroperoxide in comparison to titanium-incorporated OMS-2, where the styrene conversions were ca. 70% and 45–50%, respectively. The framework of titanium species has no effect on the enhancement of catalytic activity, while the non-framework of titanium species induces a synergetic effect that enhances the oxidation of styrene with tert-butylhydroperoxide.     

Effects of Solvent Exchange Period and Heat Treatment on Physical and Chemical Properties of Rice Husk Derived Silica Aerogels

In this study, hydrophobic silica aerogels were synthesized from rice husk ash-derived sodium silicate through sol-gel processing, solvent exchange, surface modification and ambient pressure drying. By volume, 10% of trimethylchlorosilane (TMCS) in 90% of n-hexane was used as a hydrophobic solution in the surface modification process. The physical and chemical properties of silica aerogels were characterized by density and porosity measurements, scanning electron microscopy (SEM), Fourier transforms infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller theory (BET) and dynamic scanning calorimetry (DSC). The hydrogels prepared were in the form of 2.5 ± 0.5 mm beads and then converted into alcogels through solvent exchange with ethanol for repetition of 3, 6 and 9 days. It is found that the optimal quality of silica aerogels with the BET surface area as high as 668.82 m²/g was obtained from the alcogels of the solvent exchange period of 9 days. Depending on the size of the gel’s block, a longer solvent exchange period will ensure adequate removal of pore water. Post heat treatment on silica aerogels obtained from the 9 days of solvent exchange at 200, 300 and 400 °C for 2 h results in slight decreased of aerogel’s density from 0.048 g/cm³ to 0.039 g/cm³ and the hydrophobicity of the aerogels is decreased above 380 °C as confirmed by DSC analysis.

     

Simultaneous adsorption of a mixture of paraquat and dye by NaY zeolite covered with alkylsilane

The surfaces of NaY zeolite particles were modified by the alkylsilylation of n-octadecyltrichlorosilane (OTS). Two kinds of modified NaY zeolites were prepared; one with its external surface partially and the other fully covered with alkylsilyl groups. Since the size of OTS is bigger than the pore diameter of NaY, it is attached on the external surface, leaving the internal pore accessible to adsorbate molecules. As a result of alkylsilylation, the adsorption properties of these sorbents were improved. The adsorption properties of these materials were tested by their reaction in a mixture of paraquat and blue dye. The results demonstrate that the alkysilylated NaY materials are capable of simultaneous adsorption of paraquat and blue dye. Paraquat was selectively adsorbed into the internal pore of the zeolite whereas the dye on the externally attached alkylsilyl groups of the sorbent; displaying the unique bimodal amphiphilic character of the alkylsilylated NaY zeolites.     

Thermal and mechanical behavior of natural rubber latex‐silica aerogel film

A major problem in most natural rubber latex (NRL) commonly encountered like other polymer is susceptibility to mechanical properties and thermal degradation; particularly in thin film due to the presence of double bonds in the main chain. Therefore, it is desirable to seek for ways of improving these properties. Silica aerogel is a material with extraordinary properties was believed to have potential enhance properties in NRL films because of its high specific surface area. Therefore, based on the unique character of silica aerogel, NRL‐silica aerogel film was developed by latex compounding and dry coagulant dipping to form thin film where silica aerogel acts as filler. Silica aerogel, synthesized from rice husk was dispersed in a ball‐mill using distilled water for NRL compounding. Results indicate that increasing silica aerogel loading enhances the mechanical properties of the NRL‐silica aerogel film. Effects of postvulcanization processes were also investigated, whereby the best reinforcing effect was obtained at 4 phr silica aerogel loading with leaching postvulcanization condition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Physical Properties and Bifunctional Catalytic Performance of Phosphate–Vanadium Impregnated Silica–Titania Aerogel

The excellent catalytic performance of phosphate–vanadium impregnated silica–titania aerogel as a bifunctional oxidative and acidic catalyst was evaluated in consecutive transformation of 1-octene to 1,2-octanediol through formation of 1,2-epoxyoctane using aqueous H₂O₂. Phosphate group and vanadium were impregnated onto silica–titania aerogel via wet impregnation method at room temperature, followed by a high calcination temperature. Significant increase of hydrated, tetrahedrally coordinated Ti species was found in phosphate–vanadium impregnated silica–titania sample. Pyridine adsorption study revealed that the combination of phosphate group and vanadium is essential for generation of Brønsted acidic sites. Phosphate–vanadium impregnated silica–titania catalyst produced 1,2-octanediol (275 μmol) with selectivity of 65%. In contrast, no noticeable diol was produced when silica–titania aerogel and phosphate treated silica–titania sample were used.     

Effects of silica aerogel particle sizes on the thermal–mechanical properties of silica aerogel – unsaturated polyester composites

Silica aerogels with a surface area as high as 773?m²?g^?1 and a density of 0.077?g?cm^?3 were produced from rice husk via sol–gel process and ambient pressure drying. A particulate composite material was prepared by adding silica aerogel particles of three different particle sizes (powder, granules and bead) to unsaturated polyester resin with a fixed volume fraction of 30%. Thermogravimetric and thermal conductivity studies revealed that silica aerogel composites were having higher thermal stability and thermal insulation than the neat resin. It was suggested that the preservation of aerogel pores from resin intrusion is important for better thermal properties. Larger silica aerogel particles have more porous area (unwetted region) which results in a lower degradation rate and lower thermal conductivity of the base polymer. However, the addition of silica aerogel into resin has reduced the tensile modulus of the polymer matrix where smaller particle size displayed higher toughness than those with bigger particle size.     

Organosulfonic acid functionalized zeolite ZSM-5 as temperature tolerant proton conducting material

Organosulfonic acid functionalized zeolite ZSM-5 materials namely sulfonated polystyrene ZSM-5, phenylsulfonic acid functionalized ZSM-5 and propylsulfonic acid functionalized ZSM-5, were successfully synthesized in this study. Characterization by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectrometers indicate that the functionalized zeolites comprise of the organosulfonic acid groups attached onto the surface of zeolites. Impedance spectroscopy results showed that the proton conductivities of zeolites in the operating temperature range of 24–100 °C were enhanced significantly to higher values (about 1–3 orders of magnitude) by loading of sulfonic acids onto the surface of zeolite. Proton conductivities were correlated with the concentration of sulfonic acid groups and increased as follows: sulfonated polystyrene ZSM-5 > phenylsulfonic acid functionalized ZSM-5 > propylsulfonic acid functionalized ZSM-5 which is in line with the ion-exchange capacity, acidity and water uptake analysis. The high proton conductivity of sulfonated polystyrene ZSM-5 might be explained by using surface diffusion mechanism.     

NanoMalaysia Programme (2011–2020): engine of growth for innovative Malaysia

Nanotechnology not only enables further technical and scientific advancement of existing technologies, but also creates new technology and imposes drastic impact on industries and economy. Moreover, through the implementation of nanotechnology initiatives, advances in nanoscience and nanotechnology promise to have a major impact on the society in the coming decades. Among the expected breakthroughs are an order of magnitude increase in device efficiency and emergence of entirely new phenomena in physics, chemistry and biology. Thus, many exciting prospects for new scientific knowledge, more efficient and higher quality products and technological innovations will soon be available and implemented. The NanoMalaysia Programme (2011–2020) with its strategic initiatives and action plans in various areas of nanotechnology in Malaysia is presented.     

1H mas NMR and IR studies of the acidic properties of realuminated zeolite Y

IR and¹H MAS NMR confirm that extra-framework aluminium present in dealuminated (ultrastable) zeolite Y is reintroduced into the framework by treatment with strongly basic solutions at elevated temperatures. The realuminated sample contains twice as many Brønsted acid sites than the ultrastable precursor and, with an accuracy of 20%, the same number of acid sites as the parent as-prepared zeolite. However, not as many hydroxyl groups associated with framework Al in the product are acccesible to pyridine as in the parent sample.