Thermal decomposition of metal methanesulfonates in air

Article abstract of DOI:10.1007/s10973-009-0119-z

The thermal decompositions of dehydrated or anhydrous bivalent transition metal (Mn, Fe, Co, Ni, Cu, Zn, Cd) and alkali rare metal (Mg, Ca, Sr, Ba) methanesulfonates were studied by TG/DTG, IR and XRD techniques in dynamic Air at 250-850 °C. The initial d

Full text of DOI:10.1007/s10973-009-0119-z

J Therm Anal Calorim (2009) 98:801–806
DOI 10.1007/s10973-009-0119-z
Thermal decomposition of metal methanesulfonates in air
M. Wang Æ Z. G. Song Æ H. Jiang Æ H. Gong
Received: 8 May 2009 / Accepted: 21 May 2009 / Published online: 9 July 2009
Ó Akad e´ miai Kiad o´ , Budapest, Hungary 2009
Abstract The thermal decompositions of dehydrated or
anhydrous bivalent transition metal (Mn, Fe, Co, Ni, Cu,
Zn, Cd) and alkali rare metal (Mg, Ca, Sr, Ba) methane-
sulfonates were studied by TG/DTG, IR and XRD tech-
niques in dynamic Air at 250–850 °C. The initial
decomposition temperatures were calculated from TG
curves for each compound, which show the onsets of mass
loss of methanesulfonates were above 400 °C. For transi-
tion metal methanesulfonates, the pyrolysis products at
showed good effects in the esterification [1], Biginelli
reaction [2, 3], diacetoxylation [4] and tetrahydropyrany-
lation [5], etc. So far, the structure and thermal behaviors
of them have been studied. For example, Aric o´ et al. [6, 7]
have investigated the structure and properties of hydrated
and anhydrous rare earth metal (La, Ce, Nd, Sm, Tb, Er,
Yb) methanesulfonates. Charbonnier studied the thermal
behavior of transition metal methanesulfonate (Cu, Zn, Mn,
Cd, Ag) under an inert atmosphere [8]. Tian et al. [9] have
reported the pyrolysis products of rare earth metal (La, Ce,
8
50 °C were metal oxides. For alkali rare metal methane-
sulfonates, the pyrolysis products at 850 °C of Sr and Ba
methanesulfonates were sulphates, while those of Mg and
Ca methanesulfonate were mixtures of sulphate and oxide.
Pr, Nd, Yb) methanesulfontes in N and Air atmosphere.
2
Moura et al. [10] reported the degradation of gadolinium
and lutetium methanesulfonates. Recently, We also repor-
ted the dehydration studies of Co, Cu and Zn methane-
Keywords Methanesulfonates Á Thermal decomposition Á
Transition metal Á Alkali earth metal
sulfonates in N atmosphere [11]. However, to the best of
2
our knowledge, there is no systematic study on the thermal
decomposition of the title materials in Air atmosphere. In
this paper, we study the thermal stability and thermal
decomposition products at 850 °C in dynamic Air atmo-
sphere for representative dehydrated or anhydrous bivalent
transition metal (Mn, Fe, Co, Ni, Cu, Zn, Cd) and alkali
earth metal (Mg, Ca, Sr, Ba) methanesulfonates using TG/
DTG, IR and XRD techniques.
Introduction
Methanesulfonate, a water-tolerant Lewis acid catalyst has
drawn much attention due to its excellent advantages such
as reactivity, selectivity and reuse in organic synthesis. It
Experimental
M. Wang (&)
College of Chemistry and Chemical Engineering,
Bohai University, Jinzhou 121000, People’s Republic of China
e-mail: minwangszg@yahoo.com.cn
Sample preparation
The methanesulfonates were prepared in aqueous solution
by the reaction of methanesulfonic acid (analytical grade,
Z. G. Song
Center for Science & Technology Experiment, Bohai University,
Jinzhou 121000, People’s Republic of China
[99.0%) and metallic oxide (Cu, Zn, Mg, Ca, Ba), car-
bonate (Mn, Co, Cd, Sr) or metal substance (Fe, Ni). After
heated at 80–90 °C for about 3 h, the hot solution was
filtered. The filtrate was concentrated and allowed to
H. Jiang Á H. Gong
Liaoning Shihua University, Fushun 113001,
People’s Republic of China
123

8
02
M. Wang et al.
crystallize in air at room temperature. The products were
purified by successive recrystallization with water. Ele-
mental analysis, complexometric titration, IR, and thermal
analysis techniques are used for characterization of the
methanesulfonates. Analytical results were listed in
Table 1. The stoichiometric formula of the compounds is
M(CH SO ) Á xH O. The crystallization water of all
Apparatuses
The TG experiments were performed by using a Perkin
Elmer Pyris 1 thermogravimetric analysis (TG) in a
-
dynamic air atmosphere (20 mL min ) at temperature
1
-
1
range 30–850 °C with a heating rate 20 K min . Ceramic
crucibles for TG were used and the sample powder mass is
2–3 mg.
3
3 2
2
M(CH SO ) Á xH O can be removed and determined by
3
3 2
2
TG in the temperature range 30–250 °C with a heating rate
The FTIR spectra of the decomposition products were
recorded on a Perkin Elmer spectrophotometer with resolu-
-
tion of 4 cm in the wave number range 2000–400 cm
-
0 K min . Therefore, the anhydrous bivalent M(CH3
1
2
1
-1
SO ) studied in this paper were obtained.
2
.
3
Table 1 Analytical results of
M(CH SO
Á xH
M(CH
3
SO
3
)
2
2
Á xH O
Found mass%
Calcd. mass%
3
3
)
2
2
O
M
S
2
H O
M
S
2
H O
Mn(CH
Fe(CH SO
Co(CH SO
SO
SO
SO
SO
SO
SO
SO
SO
3
SO
3
)
2
Á 2H
Á 4H
2
O
19.57
17.49
18.41
18.32
19.55
20.01
33.25
9.51
22.84
20.12
19.97
20.02
19.63
19.64
18.98
25.45
27.88
19.29
19.54
12.48
23.56
22.08
21.96
22.07
21.90
10.20
16.08
0
19.54
17.56
18.35
18.29
19.51
19.96
33.20
9.70
22.81
20.16
19.96
19.98
19.68
19.57
18.94
25.59
27.85
19.32
19.58
12.82
22.66
22.44
22.50
22.12
21.99
10.64
14.39
0
3
3
)
2
2
O
3
3
)
2
Á 4H
2
O
Ni(CH
3
3
)
2
Á 4H
Á 4H
Á 4H
Á 2H
Á 2H
2
O
Cu(CH
3
3
)
2
2
2
O
Zn(CH
Cd(CH
Mg(CH
Ca(CH
3
3
)
2
O
3
3
)
2
2
O
3
)
3 2
2
O
3
3
)
2
17.37
26.34
41.96
17.41
26.40
41.93
Sr(CH
3
3
)
2
Á 3H
2
O
17.30
0
16.29
0
Ba(CH
3
3
)
2
Fig. 1 TG/DTG curves of
thermal decomposition of
anhydrous bivalent
methanesulfonates in dynamic
Air atmosphere and heating rate
-
1
of 20 K min
1
23

Thermal decomposition of metal methanesulfonates in air
803
Table 2 Thermal
decomposition data of
anhydrous bivalent
Anhydrous methanesulfonates Tonset/°C Residue mass
fraction/%
Final residues and color characteristic of
them
M(CH
atmosphere in the temperature
3
SO
3
)
2
in dynamic air
Found
Calcd.
range 250–850 °C
Mn(CH SO )
3
498
439
452
483
412
408
446
476
474
486
436
28.08
25.72
26.34
25.67
24.11
25.55
39.57
21.85
41.87
54.93
68.73
27.45
25.10
25.11
23.42
24.43
24.87
38.10
22.03
41.74
54.69
71.26
2 3
Mn O
Black
Red
3 2
Fe(CH
3
SO
3
)
2
Fe O
2 3
Co(CH
3
SO
SO
SO
SO
SO
SO
SO
SO
SO
3
)
2
Co O
3 4
Black
Green
Black
White
White
White
White
Hoar
Ni(CH
3
3
)
2
NiO
CuO
ZnO
CdO
Cu(CH
3
3
)
2
Zn(CH
Cd(CH
Mg(CH
Ca(CH
3
3
)
2
3
3 2
)
3
3
)
2
MgSO and MgO
4
3
3
)
2
CaSO and CaO
4
Sr(CH
3
3
)
2
SrSO
4
Ba(CH
3
3
)
2
BaSO
4
White
The samples were prepared as KBr diluted pellets in the
solid-state.
decomposition are sulfides or metal substance in nitrogen
atmosphere. In this paper, the residues at 850 °C are only
metal oxides in air atmosphere and their calculated values
approximated to their respective measured values, shown
in Table 2. But definite experimental supports have been
still lacking. In order to confirm whether the residuals are
metal oxides, the infrared spectra of their thermal decom-
position products at 850 °C are shown in Fig. 2. As can be
seen from Fig. 2, there are not stretching vibration of
O=S=O, but only characteristic peaks of M–O exist in the
X-ray powder diffraction patterns were obtained with a
D/max-monochromated CuK radiation (40 kV, 100 mA).
a
The step scan mode was performed with a step 0.02° at a
rate of one step (2h) per min.
Results and discussion
-
1
Thermal stability of anhydrous bivalent
methanesulfonates
range 700–400 cm clearly.
The following problem is to ascertain which oxidation
states they are for transition metal exhibiting different
valence. X-ray diffraction was therefore used in order to
characterize the encountered phase at the end of the TG
experiments. The comparison of the XRD spectrum of the
pyrolysis product at 850 °C with standard spectrum was
The TG/DTG curves of thermal decomposition of dehy-
drated or anhydrous bivalent transition metal and alkali
earth metal methanesulfonates in dynamic Air atmosphere
at 250–850 °C were shown in Fig. 1. After dehydration,
anhydrous methanesulfonates keep stable for a rather wide
range. Then methanesulfonates decompose sharply and
rapidly to yield pyrolysis residues. Tonset, initial decom-
position temperature represents relative thermal stability of
methanesulfonates. From Table 1, all onsets of mass loss
are above 400 °C, which shows the thermal stability of
methanesulfonates is better. The onset of mass loss in TG
increases in the series: Zn \ Cu \ Ba \ Fe \ Cd \ Co \
Ca \ Mg \ Ni \ Sr \ Mn. The pyrolysis products are
classified into three types: metal oxide, sulphate and the
complex of metal oxide and sulphate, shown in Table 1.
The characteristic of them is discussed separately in the
following way.
Thermal decomposition products of anhydrous bivalent
transition metal methanesulfonates
For transition metal methanesulfonates, Charbonnier [8]
has ever investigated that the final products of thermal
Fig. 2 IR spectra of thermal decomposition products at 850 °C of
dehydrated bivalent transition metal methanesulfonates
123

8
04
M. Wang et al.
shown in Fig. 3. The XRD spectrum clearly shows the
correctness of the result identified by TG analysis in
Table 2. In addition, through color characteristic of resid-
uals, we can also conclude the final thermal decomposition
product of ferrous methanesulfonate is red Fe O (FeO and
methanesulfonate is black CuO (Cu O is red). As to zinc,
2
manganese and cadmium methanesulfonates, the final
thermal decomposition residues of them are their general
oxides, i.e. ZnO, Mn O and CdO, respectively. Hence, the
2
3
final products of thermal decomposition of transition metal
methanesulfonates at 850 °C are believed to be corre-
sponding metal oxides.
2
3
Fe O are all black), that of nickel methanesulfonate is
3
4
green NiO (Ni O3 is black) and that of copper
2
Fig. 3 XRD match results of
pyrolysis products at 850 °C of
dehydrated bivalent transition
metal methanesulfonates with
standard spectra
1
23

Thermal decomposition of metal methanesulfonates in air
805
Thermal decomposition products of anhydrous bivalent
alkali earth metal methanesulfonates
Ba(CH SO ) were approximately the same. The strong
3
3 2
-
absorption in the range 1234–1085 cm are caused by
1
stretch vibration of O=S=O, and absorption in the range
-
1027–983 cm should be ascribed to stretch vibration of
1
In the title compounds, alkali earth metal methanesulfo-
nates are special group for their pyrolysis products at
2
-
O–S–O in SO4
groups. Furthermore, mediate strong
-
1
8
50 °C are not single. The residuals of anhydrous stron-
absorption in the range 678–504 cm should be the con-
tribution of bend vibration of S–O or S=O. Therefore, the
tium and barium methanesulfonates are sulphates, while
those of anhydrous magnesium and calcium methanesulf-
onates are mixtures of sulphate and oxide. The character-
izations were as follows:
2
-
decomposition residue of them should contain SO4
groups. There is great difference between the theoretical
value and experimental value if the thermal decomposition
products of Mg(CH SO ) and Ca(CH SO ) are assumed
The infrared spectra of their thermal decomposition
products at 850 °C are shown in Fig. 4. In Fig. 4, the main
absorption peaks of the residues of Sr(CH SO ) and
3
3 2
3
3 2
as sulphate or oxide. Both vibrations of O=S=O, O–S–O
and M–O are exist in the IR spectrum of pyrolysis product
of Mg(CH SO ) . The vibrations of O=S=O and O–S–O
3
3 2
3
3 2
are not obvious in the IR spectrum of pyrolysis product of
Ca(CH SO ) . It cannot confirm the residual only from IR
3
3 2
characterization. Therefore, X-ray diffraction technique
was used.
The pyrolysis residues of Mg(CH SO ) , Ca(CH SO ) ,
3 2
3
3 2
3
Sr(CH SO ) and Ba(CH SO ) at 850 °C were subjected
3
3 2
3
3 2
to XRD studies (Fig. 5). Through comparing the spectra of
the pyrolysis residues at 850 °C with standard spectra, it
shows clearly the final products of Sr(CH SO ) and
3
3 2
Ba(CH SO ) were sulphates, while thermal decomposi-
3 3 2
tion products of Mg(CH SO ) and Ca(CH SO ) were
3
3 2
3
3 2
mixtures of sulphate and oxide rather than simple sulphate.
This fact provides further support for the analytical results
from TG and IR. It can be calculated from TG and XRD
Fig. 4 The IR spectra of thermal decomposition products at 850 °C
of anhydrous Mg, Ca, Sr, Ba methanesulfonates
data that the mass content of MgSO in pyrolysis product is
4
Fig. 5 XRD match results of
pyrolysis products at 850 °C of
anhydrous Mg, Ca, Sr, Ba
methanesulfonates with
standard spectra
123

8
06
M. Wang et al.
2
0% and CaSO in pyrolysis product is 50%. The others
4
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2
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The thermal stability and pyrolysis products at 850 °C of
some representative dehydrated or anhydrous bivalent
transition metal (Mn, Fe, Co, Ni, Cu, Zn, Cd) and alkali
rare metal (Mg, Ca, Sr, Ba) methanesulfonates in dynamic
Air have been studied in this paper. The initial decompo-
sition temperatures of them are above 400 °C. The
decomposition residues are classified into three types:
metal oxide, sulphate and the complex of metal oxide and
sulphate. The type of the pyrolysis products of the title
samples prepared depends on the metal ion in the parent
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