Michael Hess Department of Physical Chemistry University Duisburg-Essen Campus Duisburg 47048 Duisburg, Germany E-Mail: Hi259he@uni-Duisburg - de
Michael Hess Department of Physical Chemistry University Duisburg-Essen Campus Duisburg 47048 Duisburg, Germany E-Mail: Hi259he@uni-Duisburg - de
Michael Hess Department of Physical Chemistry University Duisburg-Essen Campus Duisburg 47048 Duisburg, Germany E-Mail: Hi259he@uni-Duisburg - de
Balance
Optional
to
analyzer: Zero control
IR
GC-MS
etc. oven
Conroller
Analyzer
Data output
Mass
Thermo Carrier gas: N2, air, O2, … compensation
couple
TGA-systems can be combined with:
IR-spectrometry
GC-MS
Product identification
gas phase absorption
thinlayer chromatography
DSC
Enthalpy, phase transitions
DTA
thermo-oxidative degradation
inert atmosphere, e. g. N2
reactants i 0 products i 0
dT
dt
The mass loss at any time is given by:
w = w0-w w = sample mass
w0 = initial sample mass
so that the conversion C is given by: t = time
T = temperature
C = w/w0 = (w0-w)/w0 = heating rate
C = conversion
(1-C) = w/w0 (mass-loss fraction)
rcA (A)
rcB(B
) r= kn cA (A) cB(B) …
.
kn = f(T, p, catalyst, solvent,…)
.
. i z
n
ia
i
dw
k n w0 w
n
dt
dw Ea 1
Aexp w0 w n
dt RT
log
dT dw
log A
dt dt
Ea 1
2.302R T
n log w0 w
r
can be used:
Ozawa method
3
T [K] 1T [K-1]
Arrhenius’ law:
Ea Ea 1
kn A
e RT
ln k n ln A
preexponential factor effectivit y factor R T
collision factor
C = conversion
example of a complex depolymerization
8,000
7,000
6,000
sample mass [mg]
5,000
4,000 nitrogen
3,000
2,000
Process I
Process II Process IV
Process III
Some examples of pyrolytic reactions
volatile products
disproportionation
volatile products