Research and development of method for potassium acetate of high purity

Article abstract of DOI:10.1134/S1070427212120038

Crystallization of potassium acetate from aqueous solutions, an effect of product yield and washing of its crystals on an efficiency of purification were investigated. Behavior of KCH₃COO·1.5H₂O was studied in heating. Based on data of the study a technological scheme of producing anhydrous potassium acetate of high purity was developed.

Full text of DOI:10.1134/S1070427212120038

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 12, pp. 1807−1813. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.A. Fakeev, G.L. Murskii, V.Z. Krasil’shchik, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 12, pp. 1917−1923.
INORGANIC SYNTHESIS
AND INDUSTRIAL INORGANIC CHEMISTRY
Research and Development of Method
for Potassium Acetate of High Purity
A. A. Fakeev, G. L. Murskii, and V. Z. Krasil’shchik
State Scientific Research Institute of Chemical Reagents and High Pure Chemicals, Moscow, Russia
e-mail: geo5152@yandex.ru
Received June 8, 2012
Abstract—Crystallization of potassium acetate from aqueous solutions, an effect of product yield and washing
.
of its crystals on an efficiency of purification were investigated. Behavior of KCH СOO 1.5H O was studied in
3
2
heating. Based on data of the study a technological scheme of producing anhydrous potassium acetate of high
purity was developed.
DOI: 10.1134/S1070427212120038
Potassium acetate of pure and ultrapure grades is
used as a reagent in analytical chemistry, in conducting
researches, in the production of heat-resistant silicone-
organic resins [1], antibiotics [2]. In recent years,
potassium acetate is widely used in a fire fighting
equipment and de-icing [1].
of preparation of anhydrous potassium acetate by
interaction of KOH solution with acetic acid to рН 8.3–
8.6 at 70–75°С, with purification by activated carbon
Table 1. Quality of potassium acetate produced in Russia
State Standard 5820
High purity
-3 (State
Standard TU
3
In Russia, potassium acetate is produced of
analytically pure grade (State Standard GOST 5820)
and of high purity 3-3 for researches (State Standard TU
Quality indices
analytically
pure
pure grade
6
-09-4141)
Content, wt %:
major substance
6
-09-4141) (Table 1).
Comparison of quality of domestic products with
the best foreign samples shows that products of SIGMA
BIO ULTRA (US) and FLUKA Bio Chemica Ultra
(
CH COOK) in
3
the dried product
≥99.5
≥99.0
≥99.5
substances
5 × 10–3
1 × 10–2
3 × 10–3
(Switzerland) are of higher quality with controlling of
insoluble in water
more number of impurities (Table 2).
acidity
1 × 10–1
2 × 10–1
1 × 10–1
Scarce information on ways of potassium acetate
producing is published in scientific and patent
literature: obtaining by interaction of potassium
hydroxide with acetic acid, acetic anhydride, solution of
ammonium acetate, and also of potassium carbonate or
(
CH COOН)
3
sulfates
phosphates
chlorides
iron
2 × 10–3
1 × ·10–3
2 × 10–3
5 × 10–3
5 × 10–3
5 × 10–3
2 × 10–3
2 × 10–4
2 × 10–3
5 × 10–4
1 × 10–3
5 × 10–4
hydrocarbonate with CH COOH [1–4]. It was suggested
3
preparation of anhydrous potassium acetate from KOH
of technical grade and acetic anhydride in environment
of aliphatic alcohols at 40–50°С, by treatment of the
obtained solution by activated carbon followed by
crystallization after distillation of a solvent, filtration,
and drying of the crystals. A technique was described
2 × 10–3
1 × 10–3
1 × 10–4
5 × 10–3
2 × 10–3
2 × 10–3
calcium
magnesium
arsenic
1 × 10–3
5 × 10–5
5 × 10–4
heavy metals (Pb) 5 × 10–4
1 × 10–3
7
loss on drying
5
1
807

1808
FAKEEV et al.
Table 2. Quality of anhydrous potassium acetate produced abroad
Fluka Bio
Chemica Ultra,
Switzerland
Merck
Suprapur,
Germany 2008– analysis, Italia
2010
Sigma Bio
Ultra, USA
Panreak PA,
Italia 2009–
2010
Carlo Erba for
Quality indices
2
008–2009
2
007–2008
Content, wt %:
major substance
substances insoluble in water
total nitrogen
loss on drying
chlorides
≤99.0
≤99.0
≤99.0
≤99.0–100.5
≤99.0
≤5 × 10–3
≤5 × 10–3
≤1 × 10–3
2 × 10–3 (NH4)
1.0 (130°С)
≤1 × 10–3
1.0 (105°С)
≤1 × 10–2
≤5·10–3
≤2 × 10–3
≤1 × 10–3
≤5 × 10–3
≤5 × 10–3
phosphates
sulfates
≤1 × 10–3
≤5 × 10–3
≤5 × 10–4
≤1 × 10–5
≤5 × 10–4
≤5 × 10–4
≤5 × 10–3
≤5 × 10–4
≤5 × 10–4
≤5 × 10–44
≤5 × 10–44
≤5 × 10–4
≤0.5
≤5 × 10–3
≤5 × 10–4
≤1 × 10–5
≤5 × 10–4
≤5 × 10–4
≤5·10–3
≤5 × 10–3
≤1 × 10–4
≤2 × 10–4
≤2 × 10–3
aluminum
arsenic
≤1·10–4
≤1 × 10–4
≤5 × 10–3
barium
bismuth
calcium
≤5 × 10–3
≤5 × 10–4
≤5 × 10–4
cadmium
cobalt
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5.0
chromium
copper
≤5 × 10–4
≤5 × 10–4
≤0.25
≤1 × 10–4
≤5 × 10–4
≤2 × 10–3
iron
≤1 × 10–3
≤0.5
sodium
lithium
≤5 × 10–4
≤1 × 10–3
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
7.0–9.0
≤5 × 10–4
≤1 × 10–3
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
≤5 × 10–4
7.0–9.0
magnesium
manganese
molybdenum
nickel
≤5 × 10–3
≤5 × 10–3
≤5 × 10–4
≤5 × 10–4
≤2 × 10–4
≤3 × 10–4
lead
≤4 × 10–4
strontium
zinc
≤5 × 10–4
≤4 × 10–4 (Hg)
≤2 × 10–4
рН of 1 M solution
6.5–9.0
7.5–8.5
7.5–8.0
followed by crystallization in the presence of tartaric
acid (0.005–0.025 wt %), filtration, and drying of the
crystals [1]. Also production of anhydrous potassium
acetate is known by treatment of potassium carbonate
[4]. All described techniques can provide the products
of reactive grade.
Among the techniques well-known from the literature
for preparation of especially pure substances with regard
to obtaining of potassium acetate the crystallization
from aqueous solutions can be of practical interest [5].
However, no research on the use of the technique of
or bicarbonate powder by ice CH COOH taken with
3
a 2.5% excess in term of stoichiometry with stirring
followed by heating the reaction mixture to 110–150°C
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 12 2012

RESEARCH AND DEVELOPMENT OF METHOD FOR POTASSIUM ACETATE
1809
Table 3. Solubility of potassium acetates and accompanying elements in water [6]
Solubility, wt%, at temperature, °С
Compound
0
10
20
30
50
60
80
90
KCH COO·1.5H O
68.4
70.0
71.9
73.9
76.4
3
2
(40°С)
Mg(CH COO) ·4H O
36.2
38.0
39.3
41.8
49.8
3
2
2
(15°С)
(25°С)
(35°С)
(55°С)
Ca(CH COO) ·2H O
27.2
27.0
26.5
30.4
25.8
29.5
15°С)
25.3
24.6
25.1
26.5
23.7
26.6
3
2
2
Sr(CH COO) ·0.5H O
28.7
(25°С)
27.2
43.5
26.6
(70°С)
3
2
2
(
Ba(CH COO) ·3H O
37.0
40.9
43.3
42.8
42.8
42.5
42.8
3
2
2
(18 °С)
(26°С)
(99°С)
Pb(CH COO) ·3H O
16.5
26.6
22.8
30.7
41.1
35.3
67.6
45.4
3
2
2
NaCH COO·3H O
29.0
31.7
58.2
60.5
61.7
3
2
obtaining high purity potassium acetate was found in
the literature.
Table 4. Crystal structures of potassium acetate and a number
of accompanying elements
Potassium acetate is highly soluble in water, has
a positive temperature coefficient of solubility [6], its
crystallization from aqueous solutions may be promising
for obtaining a product of high purity.
Type of crystal
Compound
Reference
[11]
lattice
KCH COO·1.5H O
Tetragonal, space
group P4/cc
3
2
For forecasting the effectiveness of the crystallization
purification of potassium acetate we reviewed published
data on phase equilibria in water–salt systems with
its participation and with acetates of accompanying
elements.
Pb(CH COO)
Monoclinic, space
[12]
[13]
3
4
group Р2 /с
1
Pb(CH COO) ·3H O
Monoclinic, space
3
2
2
group С2/m
n+
Analysis of KCH COO–M (CH COO) –H O
3
3
n
2
n+
2+
2+
2+
systems (M is Co [7, 8], Ni [9], Cu [10]) at 25°C
indicates the absence of iso- and isodimorphism of
components. In the crystallization region of potassium
acetate in the systems considered [7–10] the formation of
solid solutions was not observed, and, therefore, copper
acetate(II), cobalt(II), nickel(II) will be concentrated in
the mother liquor. Data on the study of water–salt acetate
systems with K–Fe, K–Mg, K–Ca, K–Sr, K–Ba in the
literature were not found. Large solubility of acetates
of accompanying elements in water (Table 3) points to
the possibility of their separation in the crystallization
region of potassium acetate (concentration in mother
liquor).
Zn(CH COO) ·2H O
Monoclinic, space
[14]
3
2
2
group С2/с
Mg(CH COO) ·4H O
Monoclinic, space
[15]
3
2
2
group Р2 /с
1
Ca(CH COO) ·2H O
Triclinic, space
[16, 17]
3
2
2
group Р1
Co(CH COO) ·4H O
Monoclinic, space
[18]
[19]
3
2
2
group Р2 /с
1
Cu(CH COO) ·H O
Monoclinic, space
3
2
2
group С2/с
Ni(CH COO) ·4H O
Monoclinic, space
[18]
[20]
Literature data on structures of potassium acetate
and accompanying elements (Table 4) demonstrate that
KCH COO·1.5H O is crystallized in tetragonal system,
in its crystallization lead(II, IV), calcium, magnesium,
zinc, copper(II ), cobalt (II), nickel (II), sodium acetate
3
2
2
group Р2 /с
1
3
2
NaCH COO·3H O
Monoclinic, space
3
2
group С2/с
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 12 2012

1810
FAKEEV et al.
present in the solution will be concentrated in the
mother liquor and their capture by crystals can be due to
occlusion and adsorption.
25°C with stirring, the crystals KCH COO·1.5H O were
3 2
separated from the mother liquor, and a sample was taken
for analysis. The remaining crystals were washed on the
funnel with a saturated solution of potassium acetate of
high purity (200 ml per 100 g of crystals: the ratio was
chosen experimentally) and thoroughly wrung out.
In view of the above the crystallization of potassium
acetate from aqueous solutions was investigated
experimentally. The effect of the output of potassium
acetate and washing of its crystals on the efficiency of
the purification was examined.
The sample of the solution for the analysis (the
original) was evaporated to dryness, the samples of
crystals before and after washing were dried and the
content of impurities was determined.
EXPERIMENTAL
The samples were examined by atomic emission
method with excitation in an inductively coupled plasma
Available reagents: acetic acid (analytically pure,
State Standard GOST 61) and potassium hydroxide
(plasma spectrometer Baird, USA) and preconcentration
(reagent grade, GOST 24363) were used as an original
of impurities. A determination error was 10–30%
depending on properties of an impurity and its content
raw material for potassium acetate preparation.
Potassium acetate (analytically pure, GOST 5820)
is produced in Russia in small amounts as a custom
reagent, and its use is not appropriate as an original raw
material for obtaining the product of high purity.
[21].
Based on the results we calculated purification
coefficients Kpur as a ratio of impurity content before and
after crystallization (washing). Crystallization degree α
was 0.8 [5].
The calculated amount of KOH crystals (reagent
grade) was charged in a glass apparatus equipped with
an anchor stirrer and electric heating, and then acetic
acid (analytically pure) with an excess of 30 wt % in
term of stoichiometry was slowly added. The resulting
solution of potassium acetate was filtered off from
possible mechanical impurities by paper filter “blue
ribbon,” a sample was taken for analysis, the solution
was evaporated at 115 ± 10°C to a density of 1.38–
The data of Table 5 show that in the crystallization
of KСН СОО·1.5Н О the purification from the majority
3
2
of the impurities (Kpur > 3–50) occurs. The value of
Kpur of KСН СОО·1.5Н О crystals after washing for
3
2
most of these impurities could not be found due to the
insufficient sensitivity of the analysis method.
As a whole, these data confirm the assumption on
usefulness of the crystallization for purification of po-
–3
1
.41 g cm . Afterwards the contents was cooled to
Table 5. Results of analysis of laboratory samples of potassium acetate
Content of impurity, wt %, in the sample
Impurity
Purification
coefficient, Kpur
original
7 × 10–5
3 × 10–6
5 × 10–5
5 × 10–5
1 × 10–5
7 × 10–5
3 × 10–4
5 × 10–4
3 × 10–5
8 × 10–5
4 × 10–5
2 × 10–1
after crystallization without washing after crystallization with washing
Iron
4 × 10–5
1 × 10–6
2 × 10–5
1 × 10–5
1 × 10–6
5 × 10–5
1 × 10–5
<1 × 10–4
1 × 10–5
5 × 10–5
2 × 10–6
1 × 10–1
1 × 10–5
<1 × 10–6
<1 × 10–5
<1 × 10–6
<1 × 10–6
2 × 10–5
7
> 3
> 5
> 50
> 10
> 3
> 30
> 5
6
Cobalt
Manganese
Nickel
Copper
Chromium
Magnesium
Calcium
Strontium
Barium
Lead
<1 × 10–5
<1 × 10–4
5 × 10–6
3 × 10–6
25
<2 × 10–6
2 × 10–2
> 20
10
Sodium
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 12 2012

RESEARCH AND DEVELOPMENT OF METHOD FOR POTASSIUM ACETATE
1811
tassium acetate. Comparison of the crystal structures
KСН СОО·1.5Н О [11] and acetate of accompanying
3
2
elements [12–20] (Table 4) with the data after research
n+
of the systems KCH COO–М (СН СОО) –H O
(
3
3
n
2
Mn+ = Co , Ni , Cu ) at 25°C [7–10], the solubility
2+
2+
2+
of a number of acetates (Table 3) points to the effective-
ness of the purification of potassium acetate by crystal-
lization with an additional washing of the crystals. The
impurities of the accompanying elements are concen-
trated in the mother liquor, and their capture by crystals
KСН СОО·1.5Н О may be due to occlusion (adsorp-
DTA
3
2
tion is excluded under the terms of the experiment as the
excess of CH COOH is introduced).
3
For selection of the drying conditions of crystalline
hydrate of potassium acetate in the process of obtain-
ing anhydrous product of high purity a behavior of
KCH COO·1.5Н О was investigated in heating (a de-
DTG
3
2
rivatograph MOM, Hungary). The heating was carried
out in air up to 1000°C at a rate of heating 10° min
–
1
TG
at atmospheric pressure and humidity, temperature mea-
surement accuracy was ±5°. Reference Al O calcined
2
3
at 1000°C. The weighed sample in an alundum crucible
was 300–400 mg.
Fig. 1. DTG, DTA, TG curves for KСН СОО·1.5Н О. (Δm)
3
2
Weight loss, %; (Т) temperature, °С.
According to data of thermogravimetric investigation
the compound KСН СОО·1.5Н О was stable in heating
and practically coincides with the literature data [9, 24,
25]. In contrast to results of [9, 22, 24, 25] we did not find
the formation of potassium oxalate as an intermediate.
In the region of K C O decomposition (500–600°C) on
the derivatogram there is no transformation associated
with the weight loss.
3
2
to 35–40°C, at higher temperatures it was decomposed
through two stages (Fig. 1). On the DTA curve an
endothermiceffectwasrecordedat24°Cthatisconsistent
with published data on the phase transition [22, 23]. In
the temperature range 40–250°C the compound has lost
2
2
4
1
.5 molecules of crystallization water, the weight loss
Based on the research we developed the technological
scheme of the producing anhydrous potassium acetate
of high purity (Fig. 2). The major stages of the process
were: (1) obtaining a solution of potassium acetate, (2)
evaporating the solution, crystallization with stirring;
was 19.51% (theoretical 21.57%):
KСН СОО·1.5Н О → KСН СОО + 1.5Н О.
(1)
3
2
3
2
In this case there is a fairly large endothermic effect
on the diagram at T ~ 155°C, which is a superposition of
two effects of the phase transition known in the literature
(
3) separation of crystals KСН СОО·1.5Н О, washing
3 2
them with its saturated solution of high purity prepared
in the reactor (4), (5) drying. The evaporation of
[
22, 23] and crystalline decomposition. Horizontal
sections on the curves TG, DTG in the temperature range
32–364°C are evidence of the stability of the resulting
solution of KCH COO was carried out to the density
3
–
3
of 1.38–1.41 g cm at 115 ± 10°C, the content was
cooled with stirring to 25°C, the precipitated crystals
of KCH COO·1.5Н О were carefully separated from
2
anhydrous compound KСН СОО. The endothermic
effect at T ~ 310°C corresponds to melting of KCH COO
and is consistent with the data of [9, 24, 25].
3
3
2
3
the mother liquor, washed with a saturated solution of
potassium acetate of high purity (l : s = 1 : 2), and dried
in a shelf drying box at 150 ± 5°C. The mother liquor
from the KCH COO·1.5Н О crystallization stage was
The second stage of the sample weight loss in the
temperature range 340–520°C corresponds to the
decomposition to potassium carbonate of KCH COO
3
2
3
directed at the stage (1) of obtaining the solution.
formed in the first stage:
Comparison of the results of laboratory analysis of
the sample shows that by the developed technique the
2
KСН СОО + 4О → K СО + 3Н О + 3СО
2
(2)
3
2
2
3
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 12 2012

1812
FAKEEV et al.
(
dist.)
(high purity grade)
(analytically pure)
(reagent grade)
vapor
vapor
(high purity grade)
Fig. 2. Technological scheme for production of KСН СОО of high purity. (1) Reactor for preparation of KСН СОО solution, (2)
3
3
evaporator, (3) a filter for separating and washing the crystals KСН СОО·1.5Н О, (4) reactor for preparation of the washing liquid, (5)
3
2
shelf drying box.
Table 6. Quality of the laboratory sample of potassium
acetate and the best foreign analogues (by catalogs)
anhydrous potassium acetate is obtained of very high
purity and it is of much higher quality than the best
foreign analogues (Table 6).
Fluka
Laboratory Sigma Bio BioChemica
Indices
sample
Ultra, USA
Ultra,
Switzerland
CONCLUSIONS
(
1) The high efficiency of the purification of
Content, wt %:
major substance
99.5
1 × 10–5
99.0
5 × 10–4
99.0
5 × 10–4
potassium acetate by crystallization from aqueous
solutions was demonstrated.
iron
(2) The behavior of KCH CОО·1.5H О in heating
3 2
was studied.
vanadium
cobalt
<1 × 10–6
<1 × 10–6
5 × 10–4
5 × 10–4
<1 × 10–5
5 × 10–4
5 × 10–4
(3) The technological scheme for production
of anhydrous potassium acetate of high purity was
developed.
manganese
copper
<1 × 10–6
<1 × 10–6
2 × 10–5
5 × 10–4
5 × 10–4
5 × 10–4
1 × 10–3
5 × 10–3
5 × 10–4
5 × 10–4
5 × 10–4
1 × 10–3
5 × 10–3
nickel
chromium
magnesium
calcium
lead
ACKNOWLEDGMENTS
<1 × 10–5
<1 × 10–4
<5 × 10–5
2 × 10–2
Analytical studies were conducted with the financial
support of the Russian Ministry by the equipment on
the CCU “Research scientific analytical center IREA
FSUE” under GC no. 16.552.11.7010 of 29 April 2011
sodium
0.5
5.0
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 12 2012

RESEARCH AND DEVELOPMENT OF METHOD FOR POTASSIUM ACETATE
1813
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