Reaction of zinc oxide with ammonium chloride

Article abstract of DOI:10.1134/S0036023612040043

The reaction of ammonium chloride with zinc oxide was studied kinetically and thermogravimet-rically. Reaction products were identified by IR spectroscopy and X-ray powder diffraction. Ammonium chlorozincates were found to form in the reaction and to deco

Full text of DOI:10.1134/S0036023612040043

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 4, pp. 499–501. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.A. Borisov, A.N. D’yachenko, R.I. Kraidenko, 2012, published in Zhurnal Neorganicheskoi Khimii, 2012, Vol. 57, No. 4, pp. 560–563.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Reaction of Zinc Oxide with Ammonium Chloride
V. A. Borisov, A. N. D’yachenko, and R. I. Kraidenko
Tomsk Polytechnical University, pr. Lenina 30, Tomsk, 634050 Russia
Received July 20, 2009
Abstract—The reaction of ammonium chloride with zinc oxide was studied kinetically and thermogravimetꢀ
rically. Reaction products were identified by IR spectroscopy and Xꢀray powder diffraction. Ammonium
chlorozincates were found to form in the reaction and to decompose to zinc chloride.
DOI: 10.1134/S0036023612040043
It is known that ammonium chlorozincates was sintered in a muffle furnace preheated to 210°С
(NH4)2ZnCl4 and (NH4)3ZnCl5 can be prepared from for 12 h. The theoretical composition of the product is
aqueous solutions containing zinc and ammonium (NH4)3ZnCl5
.
chlorides [1]. Ammonium chloride reacts with metal
Elemental analysis was performed as follows. The
chloride ion was determined titrimetrically with an
AgNO3 standard solution in the presence of KСrO4 as
an indicator. The studied compound was analyzed for
zinc complexometrically. A zinc compound solution
was titrated with EDTA in the presence of dithizone as
an indicator in aqueous acetone. The ammonium ion
was determined photometrically from the absorbance
of a colored ammonium complex of Nessler’s reagent.
oxides to form metal chlorides [2]. The reaction of
zinc oxide with excess ammonium chlorides yields
products that differ from zinc chloride in their physicꢀ
ochemical properties [3, 4]. The reaction of zinc oxide
with ammonium chloride was suggested to produce
ammonium chlorozincates.
The objective of this work is to establish the mechꢀ
anism of the reaction of zinc oxide with solid ammoꢀ
nium chloride and to identify reaction products.
IR spectra were recorded on a Nicolet 6700 Fouꢀ
rierꢀtransform spectrometer (Thermo Electron)
within a wavenumber range of 50–4000 cm–1 in nitroꢀ
gen flow (the ultimate admissible wavenumber scale
error was 0.5 cm–1). For the region 400–4000 cm–1,
samples pellets of the studied compound compacted with
KBr in the ratio 1 : 300; in the region of 50–400 cm–1,
test samples were Nujol mulls.
EXPERIMENTAL
Thermogravimetric analysis (TGA) and differential
scanning calorimetry (DSC) were performed on a
combined TGA/DSC/DTA SDT Q600 analyzer with
TA Instruments Universal V4.2E software data proꢀ
cessing (scale sensitivity, 0.1
Studies were conducted within a temperature range of
20–600 in an atmospheric air flow at a heating rate
µ
g; DSC noise,
≤
4
µ
W).
Xꢀray powder diffraction analysis was conducted on
a DRONꢀ3M diffractometer with a copper anticathꢀ
°
С
ode (
I
= 25 mA, V = 335 kV).
of 5 K/min in alumina crucibles. A mixture of ZnO
(0.50 g) and NH4Cl (3.30 g) was used for analysis. The
sample weight was 20 mg.
m
, %
Kinetic experiment was conducted by continuous
weighing a reaction mixture with automatic mass
recording. The conversion was determined from the
mass loss due to the formation of gaseous compounds.
The ammonium chloride decomposition rate was
determined experimentally beforehand at the same
temperatures, and the final results were appropriately
corrected. The temperature was maintained with an
accuracy of 2 K. In the kinetic experiment, we used
a carefully weighed mixture of zinc oxide and a twofold
excess of ammonium chloride with respect to stoichiꢀ
ometry, assuming the formation of zinc chloride,
ammonia, and water.
2
150.3°C
98.9%
194.7°C
93.0%
100
80
1
1
0
60
40
20
–1
–2
–3
307.0
28.3% 365.9
21.4%
°C
288.2
38.8%
°C
°C
2
521.9
3.78%
°C
0
100
200
300
T, °C
400
500 600
Products of the reaction of ammonium chloride with
zinc oxide were synthesized as follows. A mixture of
zinc oxide (5.46 g) with ammonium chloride (18.04 g)
Fig. 1.
(1) TGA and (2) DSC curves for the reaction of
ZnO with NH Cl.
4
499

500
BORISOV et al.
α
, %
320°C
370
°
C
300°C
290°C
80
60
40
20
4000 3500 3000 2500 2000 1500 1000 500
~
0
ν
, cm–1
Fig. 2. IR spectrum of the NH Cl–ZnO reaction product.
4
RESULTS AND DISCUSSION
According to TGA data, the heating of a carefully
weighed mixture of ammonium chloride and zinc(II)
0
10
20
30
40
50
τ, min
oxide initiates at 150
ZnO with the formation of chlorineꢀcontaining zinc
compound. At 195 , ammonium chloride begins to
°
С the reaction of NH4Cl and
Fig. 3. Conversion vs time for the reaction of ZnO with
NH Cl.
4
°
С
decompose with the liberation of gaseous ammonia
and hydrochloric acid [5]. Excess ammonium chloride
the M–Cl bond [6], were also found in the IR specꢀ
trum of a ZnO–NH4Cl reaction product.
is sublimed at 290
°
С
. A chlorineꢀcontaining product
is decomposed in steps (Fig. 1) and, at
T
> 307 , preꢀ
°
С
sumably gives (NH4)2ZnCl4, which in turn decomꢀ
poses to zinc chloride as follows
Relying on the IR spectrum of a chlorineꢀcontainꢀ
ing zinc product, we may suppose the presence of free
ammonium chloride, which may be due to the use of
excessive NH4Cl in the synthesis, an ammonium comꢀ
plex, and zinc chloride. To unambiguously identify the
composition of reaction products, we additionally
chemical and Xꢀray powder diffraction analyses.
ZnO + NH4Cl
heating
−NH3, −HCl
150°С
−NH3, −H2O
⎯⎯⎯⎯⎯→ NH ZnCl4 ⎯⎯⎯⎯⎯→ZnCl2.
(
)
4
2
The analysis of DSC curves shows that the endotꢀ
herm associated with the dissociation of ammonium
According to the results of chemical analysis of the
chlorineꢀcontaining zinc product (Table 1), the ratio
Zn : Cl– : NH4 is 1 : 4.4 : 2.4. This indicates the presꢀ
ence of excess ammonia. The presence of excess
ammonium chloride in the product allows us to conꢀ
clude that the chlorineꢀcontaining product represents
a mixture of zinc chloride or ammonium chlorozinꢀ
cate with ammonium chloride and is not zinc ammoꢀ
niate.
chloride is overlapped by the exotherm (195
reaction, which evolves into the endotherm (208
°
С
) of the
°
С)of
the vaporization of gaseous reaction products (H2O
and NH3). On the whole, the process proceeds with
the absorption of heat.
To identify chlorineꢀcontaining zinc products, we
conducted the solidꢀphase sintering of ammonium
chloride with zinc(II) oxide at 210 С in excess
°
NH4Cl. The product was studied by IR spectroscopy.
The IR spectrum of a ZnO–NH4Cl reaction prodꢀ
uct (Fig. 2) contains absorption bands typical of the
[NH4]+ ion and ammonium chloride at 3270, 3000,
2800, and 1400 cm–1. The bands at 3550 and 1609 cm–1
relate to the bonds of crystal water. The absorption
The Xꢀray diffraction pattern of the ZnO– NH4Cl
reaction product (Table 2) indicates that ammonium
tetrachlorozincate (NH4)2[ZnCl4] and ammonium
pentachlorozincate (NH4)3[ZnCl5] are the major
bands at 669, 295, and 140 cm–1, which are typical of components [7, 8].
Table 1. Chemical analysis of the NH4Cl–ZnO reaction product
Content, %
Zn : Cl : NH
ratio
4
Zn
Cl
NH
4
NH Cl–ZnO
1 : 4.4 : 2.4
24.50
58.95
16.55
4
reaction product
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 4 2012

REACTION OF ZINC OXIDE
501
Table 2. Xꢀray powder diffraction data for the NH4Cl–ZnO reaction product
(ZnO + NH Cl) sample
(NH ) ZnCl [12ꢀ0304]*
(NH ) ZnCl [30ꢀ0069]**
4 3 5
4
4 2
4
d, Å
I
, %
d
, Å
I
, %
d
, Å
I
, %
7.8115
6.286
19
40
33
100
21
32
17
19
31
23
65
43
23
62
18
22
18
25
22
20
19
17
17
7.7859
5.8104
4.949
45
6.2752
5.1938
11
99
5.8203
5.1957
4.9404
4.6407
4.2348
3.8736
3.6262
3.2506
3.1529
3.0017
2.8993
2.7694
2.6346
2.5922
2.3595
2.2988
1.9527
1.882
74
50
4.6437
4.2336
35
11
3.8782
50
3.6429
3.2527
3.1624
3.0025
30
20
20
25
2.9052
2.6341
50
15
2.7773
59
2.5969
2.3599
2.3029
1.1.9561
1.8856
1.8856
1.8054
1.7715
15
13
13
7
9
9
1.8168
1.7971
1.7678
7
5
* Powder Diffraction File II, Swarthmore. de Wolff P. Technisch Physische. Dienst. Delft. The Netherlands. ICDD GrantꢀinꢀAid.
** Powder Diffraction File II, Swarthmore. Natl. Bur. Stand. (U.S.) Monogr. 25 15 12 (1978).
Kinetic Studies of the Reaction of Ammonium Chloride is the final reaction product. A way of intensifying the
with Zinc(II) Oxide
reaction of NH4Cl with ZnO is to increase the process
temperature.
Processing kinetic data on the reaction of zinc
oxide with ammonium chloride was carried out using
Gistling’s, squeezing sphere, and Jander’s equations.
The applicability of these equations was evaluated by
REFERENCES
1. Shigera Obba, Acta Crystallogr., Sect. C 43, 189 (1987).
the maximum correlation coefficient
k
=
f(
α
, ).
τ
2. R. C. Young and J. L. Hastings, J. Am. Chem. Soc. 59
,
Experimental data (Fig. 3) were processed by the
squeezing sphere equation (correlation coefficients
were 0.95–0.98). The following dependence of the
765 (1937).
3. Yu. V. Karyakin and I. I. Angelov, Pure Chemicals
(Khimiya, Moscow, 1974) [ in Russian].
conversion
α
on time
τ
and temperature Т was derived:
4. A. A. Furman, Inorganic Chlorides (Khimiya, Moscow,
3
42500
−
1980) [in Russian].
⎛
⎞
α = 1 − 1 −1.29e 8.31T τ .
⎜
⎟
5. B. D. Mel’nik and E. B. Mel’nikov, Concise Engineer's
Engeer’s Hanbook on Technology of Inorganic Materials
(Khimiya, Moscow, 1968) [in Russian].
⎝
⎠
The process activation energy was 42.5 kJ/mol.
The limiting stage was the chemical reaction rate.
6. K.Nakamoto, Infrared and Raman Spectra of Inorganic
and Coordination Compounds (Interscience, New York,
1986).
Relying on the experimental data, we may say that
the reaction of ammonium chloride with zinc(II)
oxide begins at 150 С. The reaction mechanism is
stagewise and proceeds through the formation of therꢀ
mally decomposable ammonium chlorozincates
(NH4)2[ZnCl4] and (NH4)3[ZnCl5], and zinc chloride
7. W. Lang, H. A. Farach, R. J. Creswick, and C. P. Poole, Jr.,
°
Phys. Rev. B: Condens. Matter 57 (14), 8155 (1998).
8. Z. S. Liu, M. Punkkinen, A. H. Vuorimäki, and
E. E. Ylinen, Physica B: Condens. Matter 202 (1994).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 4 2012