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TitleAcetic Acid
TagsAcetic Acid Catalysis Chemical Reactions Carbon Monoxide Radical (Chemistry)
File Size508.8 KB
Total Pages30
Document Text Contents
Page 1

c© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
10.1002/14356007.a01 045

Acetic Acid 1

Acetic Acid

Hosea Cheung, Celanese Ltd., Chemicals Division, Technical Center, Corpus Christi, Texas 78469,
United States

Robin S. Tanke, Celanese Ltd., Chemicals Division, Technical Center, Corpus Christi, Texas 78469, United
States

G. Paul Torrence, Celanese Ltd., Chemicals Division, Technical Center, Corpus Christi, Texas 78469, United
States

1. Introduction . . . . . . . . . . . . . . 1
2. Physical Properties . . . . . . . . . . 1
3. Chemical Properties . . . . . . . . . 3
4. Production . . . . . . . . . . . . . . . . 3
4.1. Carbonylation of Methanol . . . . . 4
4.2. Direct Oxidation

of Saturated Hydrocarbons . . . . 10
4.3. Acetaldehyde Process . . . . . . . . 13
4.4. Other Processes . . . . . . . . . . . . 15
4.5. Concentration and Purification . . 17
4.6. Construction Materials . . . . . . . 17
5. Wastewater and Off-Gas Problems 17
6. Quality Specifications . . . . . . . . 18
7. Analysis . . . . . . . . . . . . . . . . . 18
8. Storage, Transportation,

and Customs Regulations . . . . . . 18
9. Uses . . . . . . . . . . . . . . . . . . . . 19
10. Derivatives . . . . . . . . . . . . . . . 19
10.1. Salts . . . . . . . . . . . . . . . . . . . . 19

10.1.1. Aluminum Acetate . . . . . . . . . . . 19
10.1.2. Ammonium Acetate . . . . . . . . . . 19
10.1.3. Alkali Metal Salts . . . . . . . . . . . 21
10.2. Esters . . . . . . . . . . . . . . . . . . . 21
10.2.1. Methyl Acetate . . . . . . . . . . . . . 22
10.2.2. Ethyl Acetate . . . . . . . . . . . . . . 22
10.2.3. Butyl Acetate . . . . . . . . . . . . . . 22
10.2.4. 2-Ethylhexyl Acetate . . . . . . . . . . 23
10.2.5. Other Esters . . . . . . . . . . . . . . . 23
10.3. Acetyl Chloride . . . . . . . . . . . . 23
10.4. Amides . . . . . . . . . . . . . . . . . . 23
10.4.1. Acetamide . . . . . . . . . . . . . . . . 23
10.4.2. N,N-Dimethylacetamide . . . . . . . . 24
10.5. Phenylacetic Acid . . . . . . . . . . . 24
11. Economic Aspects . . . . . . . . . . . 24
12. Toxicology

and Occupational Health . . . . . . 25
13. References . . . . . . . . . . . . . . . . 26

1. Introduction

Acetic acid [64-19-7], CH3COOH,Mr 60.05, is
found in dilute solutions in many plant and ani-
mal systems. Vinegar, an aqueous solution con-
taining about 4 – 12 % acetic acid, is produced
by the fermentation of wine and has been known
for more than 5000 years.

The major producers of acetic acid, account-
ing for ca. 70 % of total worldwide produc-
tion, are the United States, Western Europe, and
Japan. World capacity exceeds 7× 106 t/a [1].
The largest end uses are in the manufacture of
vinyl acetate [108-05-4] and acetic anhydride
[108-24-7]. Vinyl acetate is used in the produc-
tion of latex emulsion resins for applications
in paints, adhesives, paper coatings, and tex-
tile treatment. Acetic anhydride is used in the
manufacture of cellulose acetate textile fibers,
cigarette filter tow, and cellulose plastics.

2. Physical Properties

Acetic acid is a clear, colorless, corrosive liquid
that has a pungent odor and is a dangerous vesi-
cant. It has a pKa of 4.77 [2]. It melts at 16.75

◦C
[3] and boils at 117.9 ◦C [4] under 101.3 kPa [5].
It has a pungent vinegarlike odor. The detectable
odor is as low as 1 ppm. The acid is combustible
with a low flash point of 43 ◦C. The explosion

Page 15

Acetic Acid 15

the propagation step (Eq. 28), but does not con-
tribute to inefficiency-generating reactions.

Manganese also greatly increases the rate of
reaction of peracetic acid and acetaldehyde to
produce acetic acid [123]. The reaction in the
presence ofmanganese is first-orderwith respect
to peracid, aldehyde, and manganese. In addi-
tion, the decomposition replenishes the supply
of radicals. This is important since the oxidation
requires a constant flux of radicals. Manganese
ions increase both the rate and efficiency of ox-
idation.

Copper can interact synergistically with a
manganese catalyst [124]. Manganese has some
negative aspects associated with the fact that it
greatly increases the reaction rate [125]. The
increased reaction rate leads to oxygen starva-
tion and an increasing steady state concentra-
tion of radicals. Both contribute to byproduct
formation by decarbonylation and decarboxyla-
tion. However, Cu2+ can oxidize acetyl radicals
very rapidly (Eq. 29) [126].

(29)

The acetylium ion can react as shown in
Equation (30).

(30)

Peroxide or Mn3+ can reoxidize the Cu+.
Copper diverts a fraction of the reaction through
a nonradical pathway and consequently provides
a termination step that does not result in ineffi-
ciency.

Another effective catalyst is cobalt. At low
concentration, this catalyst shortens the induc-
tion period [126]. The cobalt catalyst is regener-
ated by decomposing peracetic acid. In kinetic
studies [127], CH3CO3 was the main free radi-

cal in the liquid phase. Other catalysts, for exam-
ple phosphomolybdic acids [128], also catalyze
acetaldehyde oxidation.

Additional byproducts from acetaldehyde
oxidation include ethylidene diacetate, crotonic
acid, and succinic acid.

Industrial Operation. A typical acetalde-
hyde oxidation unit is depicted in Fig-
ure 7. The reactor (a) is sparged with air or
oxygen-enriched air. Temperatures are typically
60 – 80 ◦C with pressures of 0.3 – 1.0MPa. The
reaction mixture is circulated rapidly through an
external heat exchanger to remove the heat of re-
action. The vent gas is cooled and then scrubbed
with recirculated crude product (which goes to
the reactor) and finally with water (which goes
to the aldehyde recovery column). The reactor
product is fed to the aldehyde recovery column
(b), from which the aldehyde is recycled, and
then to a low-boilers column (c) in whichmethyl
acetate is removed. The next column is the acetic
acid finishing column (d), where water is re-
moved overhead by azeotropic distillation and
finishedproduct comesoff as a vapor sidestream.
Yields are generally in excess of 90% and purity
is greater than 99 %.

4.4. Other Processes

Acetic Acid from Ethylene. Efforts to con-
vert ethylene directly to acetic acid without go-
ing through an acetaldehyde isolation step have
been of interest. Although the price of ethylene
generally makes this process unattractive, some
developments are noteworthy. Effective oxida-
tion of ethylene to acetic acid has been demon-
strated with metal oxides such as vanadium pen-
toxide. Seone et al. [129] demonstrated that the
presence of palladium enhances etylene oxida-
tion to acetic acid as temperatures as low as
230 ◦C. ShowaDenko combined palladiumwith
heteropolyacids and patented a catalyst for pro-
ducing acetic acid from ethylene and oxygen.
The catalyst contains palladium, an heteropoly-
acid, such as silicotungstic acid, and potassium
tellurite or potassium selenite. The process is
operated at 150 ◦C and 0.7MPa. Although wa-
ter is not consumed in the reaction, the presence
of water enhances the selectivity to acetic acid
and is recommended.

Page 16

16 Acetic Acid

Figure 7. Oxidation of acetaldehyde to acetic acid
a) Reactor; b) Acetaldehyde column; c) Methyl acetate column; d) Finishing column; e) Column for recovering entrainer;
f) Off-gas scrubber column

Acetic Acid from Ethane. Several groups
have investigated catalysts for the conversion of
ethane to acetic acid (Eq. 31).

C2H6 + 3/2O2 −→ CH3CO2H+H2O (31)

Union Carbide [130] developed the Ethoxene
process for the production of ethylene from
ethane and oxygen. The earliest catalysts con-
sisted of molybdenum, vanadium, and niobium
oxides and were very selective for ethylene
at temperatures below 300 ◦C. Unfortunately,
ethane conversions were low (about 10 %) due
to inhibition by the product. Further develop-
ment [131] focused on the coproduction of ethy-
lene and acetic acid with a catalyst comprised
of molybdenum, vanadium, niobium, calcium,
and antimony. The addition of water enhances
acetic acid formation. A later patent [132] dis-
closes that the addition of water and an ethylene
hydration catalyst improves selectivity to acetic
acid.

Rhône-Poulenc [133], [134] has patented a
process to make acetic acid from ethane with a
vanadium oxide or vanadyl pyrophosphate sup-
ported on titanium dioxide. Tessier et al. [135]
found that acetic acid production was favored
over ethylene and carbon oxides at temperatures
below300 ◦C.Roy et al. [136] demonstrated that
the addition of molybdenum enhanced acetic
acid selectivity. Desorption of acetic acid from
the catalyst surfacewas speculated to be the rate-
determining step of the reaction.

BPChemicals [137], [138] claims that the ad-
dition of rhenium tomixedmetal oxide catalysts

enhances selectivity to acetic acid from the oxi-
dation of ethane and/or ethylene. Again, water is
used to enhance selectivity to acetic acid. Stan-
dard Oil [139] claims good selectivity to acetic
acid with a vanadyl pyrophosphate catalyst con-
taining a transitionmetal.Hoechst [140] claims a
catalyst containing molybdenum and palladium
as effective for the production of acetic acid from
ethane. An acetic acid selectivity of 84%was at-
tained at 250 ◦C and 7 bar with a 14-s residence
time.

Although ethane is an inexpensive raw mate-
rial and high selectivities to acetic acid have been
achieved, it is unlikely that ethane oxidation will
competewithmethanol carbonylation in the near
future. The oxygen concentration must be lim-
ited for safety reasons and therefore ethane con-
version is limited per pass in the reactor. Al-
though staged addition of oxygen is possible,
product inhibition remains a problem and limits
ethane conversion. Since the addition of water is
needed to improve selectivity to acetic acid, wa-
termust be removed from the acetic acid, usually
by extractive distillation.

Acetic Acid from Microorganisms Since
about 10 000 b.c., aqueous solutions of acetic
acid have been prepared from spoiled wine
[141], [142]. Ethanol and sugar were the pri-
mary feedstocks for microorganism production
of acetic acid, although biomass has been pro-
posed [143]. The concentration of acetic acid
in solution is limited by the ability of bacteria
to thrive in low-pH solutions. Consequently,

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