Chemical Engineering October 2016 - 41

Technology Profile
Aluminum Chloride Production
By Intratec Solutions
A
luminum chloride (AlCl3) is
among the most widely used
Lewis acids in industry, and is
also one of the most powerful.
The compound is employed as a
catalyst in the manufacture of a multitude
of organic chemicals produced
by several different reaction mechanisms,
including isomerization, alkylation
and polymerization.
The main applications of AlCl3 are
in the production of ethylbenzene and
dyes. AlCl3 catalyzes the ethylation of
benzene with ethylene to yield ethylbenzene,
which, in turn, is used in the
production of styrene. In the dyestuffs
industry, AlCl3 is used as a catalyst in
the production of anthraquinone and
its derivatives, as well as in the production
of pigments.
The process
The following paragraphs describe a
conventional process for anhydrous
AlCl3 production from aluminum metal
and chlorine. Figure 1 presents a
simplified flow diagram of the process.
Reaction. The reaction takes place in
ceramic-lined, tube-shaped reactors
containing molten aluminum. Chlorine
gas is injected below the surface
of the molten aluminum pool, leading
to the formation of aluminum chloride
vapor in a highly exothermic and
practically instantaneous reaction.
The reaction occurs at 670-850°C.
The temperature is maintained in this
range by controlling the feedrates of
chlorine and aluminum and by cooling
the reactor walls with water.
The AlCl3 vapor from the reactors is
fed to air-cooled condensers, which are
vertical cylinders with conical bottoms.
Aluminum,
chlorine
Metal
chlorination
Anhydrous
aluminum chloride
Chlorine, carbon
monoxide,
alumina
Catalytic
chlorination
n Raw material n Pathway n Main product
FIGURE 2. Several possible production pathways exist for AlCl3
As the AlCl3 vapor comes into contact
with the condenser walls, it loses its
heat of sublimation, and is deposited
on the walls. The deposited solid AlCl3
is withdrawn from the condenser walls
at regular intervals, and subsequently
conveyed to holding silos.
Crushing and sizing. AlCl3 crystals
from the holding silos are crushed and
sized by sieving under a dry-air atmosphere.
After sizing, the AlCl3 product
is obtained.
Scrubber. The condensing, crushing
and sizing operations, as well as storage
facilities, are designed to avoid
the entrance of moist atmospheric air.
To achieve this, a vent system linked
to those pieces of equipment directs
the offgas (containing unreacted chlorine
and uncondensed gases) to a
caustic scrubber. The scrubbed gas is
vented to the atmosphere, while the
scrubber's bottom stream is treated
as wastewater.
AlCl3 pathways
Initially, aluminum chloride was produced
on a commercial scale from
calcined bauxite and coke. New routes
have emerged, however, that present
advantages over the bauxite process.
The advantages are derived from a reOffgas
6
Caustic
soda
make-up
Wastewater
2
Aluminum
scrap
CW
Chlorine
OCTOBER 2016
1
3
CW
5
Aluminum
chloride
FIGURE 1. This figure shows a conventional process for the production of AlCl3 from aluminum and chlorine
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
41
7
4
CW = Cooling water
duced occurrence of reactor corrosion
and from the production of a higherpurity
product. Currently, the most important
raw materials for AlCl3 production
are either aluminum metal or pure
aluminum oxide. Figure 2 presents different
pathways for AlCl3 production.
Economic performance
The total capital investment estimated
to construct a plant based on the process
in Figure 1 with capacity to produce
5,000 metric ton per year of AlCl3
in the U.S. is about $8 million (data
from the second quarter of 2013). This
capital investment includes fixed capital,
working capital and additional capital
requirements.
This column is based on " Aluminum
Chloride
Production
n
Process
- Cost Analysis, " a report published
by Intratec. It can be found at: www.
intratec.us/analysis/aluminum-chloride-production-cost.
Edited
by Scott Jenkins
Editor's note: The content for this column is supplied by Intratec
Solutions LLC (Houston; www.intratec.us) and edited
by Chemical Engineering. The analyses and models presented
are prepared on the basis of publicly available and nonconfidential
information. The content represents the opinions
of Intratec only. More information about the methodology for
preparing analysis can be found, along with terms of use, at
www.intratec.us/che.
1. Reactor
2. Condenser
3. Holding silo
4. Crusher
5. Sizing equipment
6. Caustic scrubber
7. Cooling tower
Chlorination
Aluminum,
hydrogen chloride
Chlorination
Bauxite, coke,
chlorine

http://www.intratec.us/analysis/aluminum-chlo http://www.intratec.us http://www.intratec.us/che http://WWW.CHEMENGONLINE.COM

Chemical Engineering October 2016

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