الفهرس 
AIM OF THE WORKOnly 14 pages are availabe for public view
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Abstract
SUMMARY AND CONCLUSIONS
Mesoporous alumina with narrow pore size
distribution was synthesized using sol-gel method. The
effect of various synthesis parameters, including reactants
molar ratio, type of co-surfactant, aging time and the
presence of source of power (conventional process - under
ambient conditions (C) and microwave irradiation (MW))
on the structural properties of the resultant alumina samples
were examined. The texture and crystalline phase of the
prepared samples were characterized using XRD, TG-DTA,
FT-IR, N2 adsorption-desorption, pyridine adsorption, and
TEM. The adsorption activity of the prepared samples was
examined towards thiophene and dibenzothiophene species
and the resulted materials have the following
characteristics:
- All of the prepared alumina samples using different
preparation conditions show similar XRD patterns
with the reflections of γ-alumina appeared after
calcination at temperature 600ºC and at 400ºC in
case of conventional process (under ambient
conditions) and microwave irradiation process
successively.
- The TEM photographs of all prepared alumina
samples illustrated that the alumina particles was
build as cylindrical shapes have diameter ranged
from 68 to 73 nm and length ranged from 326 to 518
nm under conventional process but when using the
microwave irradiation the diameter ranged from 41
to 102 nm and length ranged from 172 to 489 nm.
Summary and Conclusions
168
- All isotherms of the prepared alumina samples by
conventional process could be classified as type IV
for mesoporous materials and H3 hysteresis loop due
to the presence of non-rigid aggregates of plate-like
particles giving rise to slit-shaped pores.
- Microwave irradiation give also alumina samples
with type IV isotherm and H2 hysteresis loop. Such
loops are characteristics of many inorganic oxide
gels. These materials have complex pore structures
like as interconnected pore networks of various sizes
and shapes.
- In case of using propanol as co-surfactant at metal
precursor/ surfactant/ co-surfactant molar ratio 2/1/1
and aging time 4h at 25 ºC by conventional process
give alumina sample with surface area 262 m2/gm,
total pore volume 0.520 cm3/gm, micropore volume
0.067 cm3/gm and average pore diameter 4.42 nm.
That increases in surface area give increasing in
pyridine adsorption capacity 1302 μmol pyridine/gm.
- By using iso-propanol at molar ratio 2/1/1 metal
precursor/ surfactant/ co-surfactant and after
exposure to microwave irradiation for 8 min at 300
watt, Lewis acid sites increased and accordingly the
pyridine adsorption capacity increased to 2189 μmol
pyridine/gm that due to increasing the surface area to
334.2 m2/gm and the average pore diameter to 5.80
nm.
- Increasing of the surface area of the alumina samples
corresponded with an increasing in the pyridine and
thiophene adsorption capacity due to increasing the
Lewis acid sites.
Summary and Conclusions
169
- The adsorption capacity of different prepared
alumina samples towards the dibenzothiophene
species dissolved in dodecane (500 ppm) shows
direct proportional relation of the adsorption activity
with the values of the surface area and strength of the
acid sites on the surfaces of the tested samples.
- The synthesized alumina sample that had been
prepared under microwave irradiation of power 300
watt and aging time 8 minutes based on aluminum
nitrate to CTAB to iso-propanol molar ratio 2:1:1,
was selected to be used as support for impregnation
molybdenum oxide and tungsten oxide species.
- The γ-Al2O3 sample had been mixed with a solution
of [(NH4)6Mo7O24.4H2O] or [(NH4)6WO12.xH2O] at
pH 6.5 to prepare different catalysts contained
several percentages related to the two transition
metals impregnated on alumina.
- The catalyst has the highest metal weight percentage
on alumina showed the lowest surface area, the
lowest total pore volume and the lowest surface
acidity, that related to the poor distribution of such
high metal content.
- The TEM photographs of alumina-supported
catalysts with different percent of metal content
showed the lowest metal surface density the good
distribution on the alumina surface. On the other
hand, the catalysts that have high metal contents
showed molybdate and tungestate clusters.
- The catalyst coded (M5) showed the highest surface
area within the prepared molybdenum oxide catalysts
(~141.9 m2/g). The textural properties of the sample
indicated creation of micropores due to the
Summary and Conclusions
170
impregnation of the molybdenum oxide species
(~0.033 cm3/g), the average pore diameter of the
sample is the widest within the prepared
molybdenum oxide catalysts (5.96 nm).
- The catalyst coded (W5) achieved the highest surface
area within the prepared tungestate catalysts (~156.8
m2/g). The textural properties of the sample showed
existence of micropores due to the impregnation of
the tungestate species (~0.195 cm3/g), The average
pore diameter of the sample is the widest within the
prepared tungestate catalysts (6.34 nm).
- There is a positive proportional relation between the
adsorption capacity of the molybdenum oxide
alumina and tungestate alumina catalysts and their
surface area. The catalysts that had been coded M5
and W5 showed high thiophene and
dibenzothiophene adsorption capacity due to increase
the exposure Lewis acid sites in the surface of these
catalysts.
- Oxidation of the sulfur compounds using H2O2 and
(M5 or W5) as catalysts decreased the aromatic and
sulfur contents from 16 wt.% and 450 ppm to 9.6
wt.% and 225 ppm respectively in case of using
molybdenum oxide catalyst while in case of using
tungsten oxide catalyst the decrease are to 10 wt.%
aromatic and 234 ppm sulfur.
- The aromatic and sulfur contents reached to 4 wt.%
and 10 ppm content respectively when use cross
current solvent extraction of S/F ratio 3/1 from
NMP+10wt.% EG and followed by adsorption by
using M5, but in case using W5 as adsorbent
Summary and Conclusions
171
materials we reached to 5 wt.% aromatic content and
15 ppm sulfur content.
That results are compatible with the international
environmental regulations for on-road diesel fuel where
in US, the acceptable sulfur content diesel fuel had been
decreased down to 15 ppm at 2013, while in Europe, the
sulfur content reduced to 10 ppm since 2013. Moreover,
in Japan, the acceptable sulfur level in diesel had reached
10 ppm since 2007 while the south Korea’s diesel sulfur
content reached 10 ppm and below since 2009 [Tanya,
2014]