الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 232 |  |  |
| | | from | 232 | | |
Abstract
Ordered mesoporous materials raised a wide interest in the scientific
community due to their unique structural properties which encompasses nanosize
ordered channels and high surface areas (~1000 m2
/g). These materials have
potential applications in diverse technological fields such as catalysis, membranes,
microelectronics and sensors. The formation of these materials is initiated by the
interaction of micelle of surfactant molecules with precursors of an inorganic
oxide, usually sodium silicate, which further polymerizes to form solids with a
well defined pore structure and amorphous walls.
Sulfated transition metal oxides such as sulfated zirconia (S-ZrO2) as solid
superacids have been received much attention due to their significant catalytic
activities in hydrocarbon conversions such as esterification, isomerization,
alkylation, etc. The remarkable catalytic activities for these sulfated transition
metal oxides are mainly attributed to their properties as superacids. The generation
and structures of Brønsted and Lewis acid sites are responsible for these activities.
Unfortunately, the relatively small surface area for the sulfated transition metal
oxides may limit their usefulness in catalytic activities. A direct impregnation
method has been developed to explore the positive characteristic of both materials
discussed above. The sulfated metal oxides continue manifest their remarkable
catalytic activities while the high surface area of the mesoporous silica structure
ensures a large number of acid sites.
The first part of the work deals with the hydrothermal synthesis of mobile
composite material (MCM-41) using the conventional structure-directing agent,
cetyltrimethylammonium bromide, and used as a support for zirconium oxide. The - XII -
second part focuses on synthesis of phosphorous-mesoporous silica (P-MCM-41)
with helically ordered pores using a novel mixed surfactants
(cetyltrimethylammonium chloride and cetytriphenylphosphonium bromide) with
different weight ratios in order to direct incorporate phosphorous species into
MCM-41 species and used as a support for zirconium oxide. These materials were
characterized by powder X-ray diffraction (XRD), high resolution transmission
electron microscopy (HRTEM), field emission scanning electron microscopy
(FESEM), nitrogen adsorption, Fourier transform infrared spectroscopy (FTIR),
UV-Raman spectroscopy, ammonia temperature programmed desorption (NH3-
TPD) and thermogravimetric analysis.
Compared with primary Zr-MCM-41, Zr-P-MCM-41 samples exhibited
higher cumene cracking activity at the same conditions. The incorporation of
phosphorous into MCM-41 materials generated more acidic centers and more
reactive hydroxyl groups on the support surface, which can provide not only the
enhanced MCM-41 structure but also the well dispersion of catalytic active phases,
SZrO2.