| Alumina |
 |
In the industrial process, Activated Alumina is produced from
dehydroxylating of aluminium hydroxide. The resultant material can have
a significant surface area over 200 square metres/g. Basically Activated
aluminas are porous materials that consists of water and alumina in
various proportions. These result in different forms of structures.
Activated Aluminas are essentially amorphous (or non-crystalline) in
nature that is the reason why the pore structure is not uniform. The
pore system of Activated alumina contains mesopores and macropores.
Unlike molecular sieves they do not have a large fraction of micropores.
This property is depicted as the size of the molecules that is needed to
be adsorbed has little influence on its adsorptive selectivity.
Activated alumina’s usage as an adsorbent is more or less
determined by its surface functionality. These can be upgraded by
thermal treatment or by additional promoters during the manufacturing
process. The nature of this internal surface area means that the
activated alumina adsorbent would attract and gather molecules from a
gas or liquid to which it is exposed to. This is what is referred to as
adsorption.
Features of Activated Alumina:
- Moisture Capacity: The combination of high surface area
and good pore distribution give activated alumina a high water
adsorption capacity. That translates to smaller bed sizes and/or
long operating cycles.
- Smooth beads and Low abrasion: This feature ensure
comparatively less dusting during the processes of tower loading and
depressurization. Low abrasion denotes lower pressure drop and
reduces the risk for plugged or clogged valves, pore orifices, or
filters due to carryover of dust.
- Low pressure drop: Activated alumina provides a low
pressure drop in a packed bed which minimizes channeling and
optimises utilization of the drying capacity of the tower.
The properties of Activated Alumina that make them suitable for PSA
separation processes is shown in the tabular form.
Typical Activated Alumina Properties |
Part Number |
1AA116 |
1AA18 |
1AA316 |
1AA14 |
Bead Size |
1/ 16" (2.0 mm) |
1/ 8" (3.2 mm) |
3/ 16" (4.8 mm) |
1/ 4" (6.4 mm) |
Color |
White |
White |
White |
White |
Surface Area |
360 m2 /gram |
355 m2 /gram |
340 m2 /gram |
325 m2 /gram |
Pore Volume |
05cc/ gram |
05cc/ gram |
05cc/ gram |
05cc/ gram |
Bulk Density |
48 lbs. /ft3 769 kg/m3 |
48 lbs. /ft3 769 kg/m3 |
48 lbs. /ft3 769 kg/m3 |
48 lbs. /ft3 769 kg/m3 |
Crush Strength |
11 lbs. (5kgs) |
30 lbs. (14kgs) |
55 lbs. (25kgs) |
70 lbs. (32kgs) |
Abrasion Loss |
0.1 wt% |
0.1 wt% |
0.1 wt% |
0.1 wt% |
Static Sorption @ Relative Humidity
% 11% RH |
8 |
8 |
7 |
7 |
@ 58% RH |
22 |
22 |
21 |
19 |
@ 97% RH |
42 |
42 |
40 |
38 |
Use
of Activated Alumina in PSA process:
There is widespread use of Activated Alumina in PSA separation
processes involving various gases an example here is given for a
successful separation for production Of Carbon monoxide. In this process
of carbon Monoxide separation, the adsorbent that is used is a chemical
adsorbent of the Activated Alumina. It carries a copper compound, that
has the capability of selective adsorption of Carbon Monoxide. This
facilitates a single stage process of separation and recovery of high
purity CO from the gaseous mixture of H
2, CO, CO
2,
and N
2.
