Abstract

The expansive nature of soils containing high amounts of montmorillonite mineral can be altered through chemical stabilization, resulting in a material suitable for construction purposes. In this paper, the physicochemical behaviour of phosphoric acid treated samples was studied using X-ray Diffractometry (XRD), Energy Dispersive X-ray Spectrometry (EDAX), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), and Solid-State Nuclear Magnetic Resonance spectroscopy (SS-NMR). It was found that in acid stabilized montmorillonitic soil, clay alumina was more susceptible to dissolution and mostly responsible for the formation of aluminate phosphate hydrate compounds that bonded the soil particles together. Furthermore, since the action of stabilizer was mainly “surface-associated”, the efficiency of phosphoric acid treatment in terms of strength improvement was rather limited.

The structure, basicity and acidity properties of the alkali metals (Na, K and Cs) exchanged zeolite beta were investigated in this work. Infrared (IR) and X-ray diffraction (XRD) were used for structural characterizations, while Temperature programmed desorption (TPD) of CO2 and NH3 were use for the determination of basicity and acidity, respectively. Results reveal that the framework structure of zeolite beta is retained after the exchange but with a successive decrease in the relative crystallinity after the modification. The acidity of zeolite beta was strongly affected by the crystallinity of the ion-exchanged zeolite beta, in which the acidity has decreased significantly with the decrease in the crystallinity. However, the basicity after the exchange was not very significant in comparison to the acidity. The effect of the crystallinity and the type of alkali metal cations on basicity is also shown.

The need for cleaner environment concerns motivates the development of more efficient catalytic system. Based on this consideration, recently a novel catalyst named "Phase-boundary catalyst", a bimodal amphiphilic solid catalyst, was proposed. It was demonstrated that the catalytic system containing phase-boundary catalyst required neither stirring to make an emulsion nor addition of a co-solvent to make a homogeneous solution to drive the reaction. The driving force that has prompted this paper is to investigate the surface structure of alkylsilylated HZSM-5 as phase-boundary catalyst. Temperature Programmed Desorption (TPD) of ammonia and, 13C and 29Si MAS NMR spectroscopy were used to elucidate the surface structure of alkylsilylated HZSM-5. It is suggested the addition of small amount of water to the solid particles before alkylsilylation, as a recipe to make a bimodal amphiphilic particles, is desired to enhance the acidity of HZSM-5. The enhancement of acidity might be induced by polymeric octadecylsiloxane as elucidated by 13C and 29Si MAS NMR spectroscopy

Abstract

Stannic oxide-titanium dioxide (SnO2–TiO2)
coupled semiconductor photocatalyst loaded with polyaniline (PANI), a conducting
polymer, possesses a high photocatalytic activity in oxidation of 1-octene to
1,2-epoxyoctane with aqueous hydrogen peroxide. The photocatalyst was prepared
by impregnation of SnO2
and followed by attachment of PANI onto a TiO2
powder to give sample PANI-SnO2–TiO2.
The electrical conductivity of the system becomes high in the presence of PANI.
Enhanced photocatalytic activity was observed in the case of PANI-SnO2–TiO2
compared to PANI-TiO2,
SnO2–TiO2,
and TiO2.
A higher photocatalytic activity in the oxidation of 1-octene on PANI-SnO2–TiO2
than SnO2–TiO2,
PANI-TiO2,
and TiO2
can be considered as an evidence of enhanced charge separation of PANI-SnO2–TiO2
photocatalyst as confirmed by photoluminescence spectroscopy. It suggests that
photoinjected electrons are tunneled from TiO2
to SnO2
and then to PANI in order to allow wider separation of excited carriers.