into KBr pellets and studied.
Thermogravimetric Analysis (TGA). TGA was used to determine
the conversion of Al(OH)2 to Al2O3 during heat
treatment. These studies were conducted under a nitrogen
flow. To measure the weight loss the Al2O3 samples were
placed in a basket and heated at a rate of 10°/min from room
temperature to 700 °C. The instrument used was a thermogravimetric
analyzer TGA-50 from the Shimadzu Co.
Elemental Analysis. Al2O3 after heat treatment was transferred
to glass vials, under argon atmosphere, and sent to
Galbraith Laboratories for analysis. Elemental analysis was
conducted for Al, C, and H. The amount of oxygen was obtained
by subtracting the sum of Al, C, and H from 100.
Adsorption Studies. Reaction of Al2O3 and Al2O3/MgO
with CCl4. These reactions were conducted in a U-tube that
was connected to a gas chromatograph (GOW-MAC gas chromatograph
series 580).34 The U-tube was made of Pyrex and
connected between the injector port and the column (Alltech
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Chromosorb W-HP). An oxide sample (0.100 g) was placed in
the U-tube between two small plugs of quartz wool. The most
favorable temperatures for both reactions were found to be at
500 °C, and the U-tube was heated to this temperature. The
injector port was kept at 100 °C. Injections of 2 ÌL of CCl4
were made every 7 min. Any CO2 coming off the sample, or
CCl4 that was not destroyed, was then sent via helium (20
cm3/min) through the column (90 °C) to be separated. They
were then detected by a thermal conductivity detector (120
°C) and peak areas recorded. Injections of CCl4 were made
until the oxide bed had been exhausted.
Sulfur Dioxide Adsorption. A quartz spring balance was
used to measure the adsorption of SO2 onto Al2O3 and Al2O3/
MgO. The apparatus consists of a basket, which is used to hold
the sample, and this is attached to a quartz spring.35 The
basket and the spring are closed within the vacuum line. The
SO2 gas tank is also attached to the vacuum line. As the SO2
adsorbs onto the metal oxide in the basket, the weight change
causes the spring to move, and this movement is noted by a
telescope. Once the telescope is calibrated, it is accurate to
Granules (100 mg) of oxides were placed into the basket on
the spring balance. The samples were placed under dynamic
vacuum for 1 h at room temperature. After evacuation, the
vacuum line was closed to the pump and the spring position
was noted. The SO2 gas was allowed to fill the vacuum line,
including the spring balance to the desired pressure. The
spring position was noted over the next hour. This was followed
by 100 min of evacuation to remove all physisorbed species.
After the evacuation the spring position was noted again, indicating
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