Journal of Thermal Analysis and Calorimetry, Vol. 88 (2007) 1, 47–49
THE KINETICS OF THERMAL DECOMPOSITION OF BISMUTH
OXOHYDROXOLAURATE
1*
V. Logvinenko , K. Mikhailov and Yu. Yukhin
2
2
1Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Ac. Lavrentyev Ave. 3
Novosibirsk–90, 630090, Russia
2Siberian University of Consumer’s Cooperation, K. Marx Ave. 26, Novosibirsk, 630087, Russia
The bismuth salt of lauric (dodecanic) acid Bi6O4(OH)4(C11H23COO)6 was studied earlier. This salt has layer structure
(the interlaminar distance=37.50 ), under heating this liquid-crystalline state has the mesomorphic transformation, turns to the
amorphous state, decomposes stepwise with the formation of well-ordered layers of bismuth nanoparticles. DSC-curves were used
for the study of the decomposition kinetics in the area of decomposition with small mass loss and exothermic effect (423–483 K).
Keywords: bismuth, coordination compounds, ‘model free’ kinetics
Introduction
• The decomposition with noticeable mass loss and in-
essential heat effect (473–553 K); we studied the ki-
netics of the decomposition at 373–533 K; the con-
stancy of the activation energy was observed at
50–90% of decomposition degree (that is 473–553 K
interval). The final results: E=44–46 kJ mol–1;
lgA=1.2–2.0 [1].
The hydroxo-salt of lauric (dodecanic) acid:
Bi6O4(OH)4(C11H23COO)6 was studied earlier [1].
Bismuth
oxohydroxolaurate
Bi6O4(OH)4(C11H23COO)6 has layer structure, the
interlaminar distance=37.50 , under heating this liq-
uid-crystalline state has the mesomorphic transforma-
tion, turns to the amorphous state, decomposes
stepwise with the formation of well-ordered layers of
bismuth nanoparticles [2].
In general the stages resolution of the multi–step
decomposition can be quite different (better or worse)
on TG or DSC curves. The steps contributions in the
mass loss sum and in the heats sum are different be-
cause of the difference in molar mass of evolved
gases and in reactions molar enthalpy. So we tried to
obtain the kinetic parameters of the very initial stage
of decomposition (353–483 K), by processing the
DSC data of this reaction.
The beginning step of chemical transformations
under heating proceeds inside polyatomic cation lay-
ers with lauric (dodecanic) acid elimination
(403–483 K), lauryl ketone evolves later.
This compound decomposes (with mass loss
≈40%) under quasi-isothermal conditions in two steps:
Δm1≈14% (373–533 K) and Δm2≈26% (533–673 K).
Experimental conditions: the standard open crucible,
sample mass 100 mg, constant mass loss rate
0.4 mg min–1, atmosphere – helium (120 cm3 min–1).
Linear heating and plate-like sample holder were
used for kinetic studies; sample mass was 20 mg,
heating rate 2.5, 5 and 10 K min–1; helium flow
120 cm3 min–1. The mentioned temperature intervals
change (so as the kinetic stability of intermediates
governs the process), and the first temperature inter-
val (14% of mass loss) becomes multi-step one.
There are three decomposition steps:
Experimental
The synthesis of the salt was described earlier [1].
DSC curves and TG curves (Figs 1, 2) were ob-
tained by means of thermoanalyzer Netzsch
STA 449C; experimental conditions: sample mass
was about 10 mg (DSC) or 60 mg (TG), standard alu-
minum sample holder for DSC measurement (the lid
with holes), helium flow 30 cm3 min–1. We used for
the calculation only the big DSC peak.
The temperature interval of this exo effect
(403–463 K at 3 K min–1) corresponds to the very be-
ginning of the decomposition on TG curve (full
Δm≈1.2% only, Fig. 1). We did not succeed in the cal-
culation of kinetic parameters according to TG curves
• The decomposition with small mass loss and endo-
thermic effect (353–403 K, if m=10 mg);
• The decomposition with small mass loss and exo-
thermic effect (423–483 K);
*
Author for correspondence: val@che.nsk.su
1388–6150/$20.00
© 2007 Akadémiai Kiadó, Budapest
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
Logvinenko
