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Analysis of Pyrolysis Characteristics and Kinetics of Cigar Tobacco and Flue-Cured Tobacco by TG-FTIR

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Figure 1

TG (a) and DTG (b) curves of CFT, CWT and FCT pyrolysis processes at the heating rate of 10 °C min−1.
TG (a) and DTG (b) curves of CFT, CWT and FCT pyrolysis processes at the heating rate of 10 °C min−1.

Figure 2

TG-DTG curves of CFT (a), CWT (b) and FCT (c) pyrolysis processes under different heating rates of 5 °C min−1, 10 °C min−1, 15 °C min−1, and 20 °C min−1.
TG-DTG curves of CFT (a), CWT (b) and FCT (c) pyrolysis processes under different heating rates of 5 °C min−1, 10 °C min−1, 15 °C min−1, and 20 °C min−1.

Figure 3

3D TG/FTIR diagram of pyrolysis products for CFT (a), CWT (b) and FCT (c).
3D TG/FTIR diagram of pyrolysis products for CFT (a), CWT (b) and FCT (c).

Figure 4

FTIR spectra of volatile products at peak temperature for tobacco samples.
FTIR spectra of volatile products at peak temperature for tobacco samples.

Figure 5

Evolution of gas products with increasing temperature in the pyrolysis of tobacco.
Evolution of gas products with increasing temperature in the pyrolysis of tobacco.

Figure 6

Arrhenius plots of FWO method for CFT (a), CWT (b) and FCT (c) at different conversion rates.
Arrhenius plots of FWO method for CFT (a), CWT (b) and FCT (c) at different conversion rates.

Figure 7

Arrhenius plots of KAS method for CFT (a), CWT (b) and FCT (c) at different conversion rates.
Arrhenius plots of KAS method for CFT (a), CWT (b) and FCT (c) at different conversion rates.

Figure 8

Changes in Ea versus α obtained by applying the FWO and KAS methods.
Changes in Ea versus α obtained by applying the FWO and KAS methods.

Figure 9

y(α) versus α curves at 10 °C min−1 calculated by Equation [8] for tobacco leaves, (a) CFT, (b) CWT, (c) FCT.
y(α) versus α curves at 10 °C min−1 calculated by Equation [8] for tobacco leaves, (a) CFT, (b) CWT, (c) FCT.

Composition of tobacco leaves.

Item CFT CWT FCT
Proximate analysis (wt.%)
Moisture 2.95 3.84 1.89
Volatile 77.31 75.41 76.79
Fixed carbon 12.80 11.19 16.76
Ash 9.89 13.40 6.54
Ultimate analysis (wt.%)
C 43.57 42.95 41.83
H 5.88 6.17 6.32
N 3.63 3.77 1.67
S 0.00 0.18 0.17
O 36.52 37.41 43.28
Biochemical analysis (wt.%)
Hemicellulose 2.25 3.24 2.81
Cellulose 11.35 13.12 14.26
Lignin 2.84 3.65 3.21
Nicotine content (wt.%) 2.20 2.33 2.07

Characteristic parameters of tobacco leaves during pyrolysis.

Sample TS (°C) Tmax (°C) Rmax (% min−1) Rmean (% min−1) ΔT1/2 (°C) Di (10−7%2 °C−3 min−2) Residue (%)
CFT
 5 130 313 −2.01 −0.43 105 2.02 24.46
10 134 323 −3.96 −0.86 112 6.99 24.73
15 142 330 −5.78 −1.27 121 12.91 25.71
20 146 335 −7.65 −1.68 122 21.61 26.11
CWT
 5 131 297 −2.16 −0.43 72 3.30 24.75
10 140 307 −4.21 −0.83 76 10.62 27.56
15 144 310 −6.22 −1.23 79 21.61 28.25
20 151 315 −8.18 −1.62 82 33.94 28.97
FCT
 5 101 188 −1.82 −0.47 60 7.51 18.75
10 103 197 −3.73 −0.92 62 27.30 20.06
15 108 201 −5.60 −1.36 64 54.80 21.38
20 115 206 −7.30 −1.80 65 85.30 21.82

Identification of gas products during pyrolysis of tobacco based on FTIR spectra.

Wavenumber (cm−1) Functional groups Compounds References
3500–4000 (selected:3566) O-H Symmetrical and asymmetrical stretching H2O (14, 42, 45)
2250–2500 (selected:2359) Asymmetrical stretching in O=C=O CO2 (14, 45)
2850–3030 (selected:3016) C-H Stretching CH4 (43)
2000–2250 (selected:2190) Stretching vibration in CO CO (14, 45)
1710–1800 (selected:1749) C=O Stretching Carbonyl groups (14, 45)
1050–1200 (selected:1180) C-O Stretch Hydroxyl groups (14)
1450–1650 Aromatic C=C-C ring stretch Aromatics (42, 43)
3070–3130 (selected:3076) Aromatic C-H in plane bend
966 NH3 (42)

Kinetic parameters of tobacco thermal decomposition obtained by Coats-Redfern method.

Sample Stage Reaction Fitted equation A (min−1) Ea (kJ mol−1) Correlation coefficient R2
CFT II D1 Y = −10165.86x + 6.09 4.49 × 104 84.5 0.995
III F3/2 Y = −23551.40x + 26.44 7.12 × 1013 195.8 0.990
F2 Y = −28195.40x + 34.48 2.65 × 1017 234.4 0.997
CWT II D1 Y = −10305.79x + 5.30 7.74 × 104 85.7 0.998
III F3/2 Y = −22403.96x + 25.26 4.17 × 1013 186.2 0.963
F2 Y = −27020.35x + 33.40 1.73 × 1017 224.7 0.984

Mass loss at different temperature intervals during pyrolysis of tobacco leaf samples.

Sample Stage I Stage II Stage III

Temperature interval (°C) Mass loss (%) Temperature interval (°C) Mass loss (%) Temperature interval (°C) Mass loss (%)
CFT
 5 40–130 2.84 130–283 22.60 283–397 26.43
10 40–134 2.88 134–292 23.26 292–411 26.78
15 40–142 3.03 142–296 23.07 296–415 26.77
20 40–146 3.06 146–299 23.35 299–424 27.34
CWT
 5 40–131 2.81 131–273 20.04 273–407 25.33
10 40–140 2.85 140–284 20.83 284–417 24.65
15 40–144 2.84 144–287 20.94 287–419 24.32
20 40–151 2.96 151–291 21.08 291–426 24.44
FCT
 5 40–101 1.29 101–216 21.09 216–401 38.82
10 40–103 1.10 103–227 22.27 227–405 38.41
15 40–108 1.15 108–232 21.76 232–408 38.19
20 40–115 1.27 115–240 22.12 240–416 37.40

Activation energies of cigar tobacco leaves obtained by the FWO method and KAS method.

Conversion CFT CWT FCT



FWO KAS Difference FWO KAS Difference FWO KAS Difference



Ea (kJ mol−1) Correlation coefficient R2 Ea (kJ mol−1) Correlation coefficient R2 (%) Ea (kJ mol−1) Correlation coefficient R2 Ea (kJ mol−1) Correlation coefficient R2 (%) Ea (kJ mol−1) Correlation coefficient R2 Ea (kJ mol−1) Correlation coefficient R2 (%)
0.1 207.4 0.984 210.3 0.982 1.40 160.4 0.993 161.0 0.993 0.35 102.2 0.999 100.1 0.999 1.02
0.2 249.9 0.995 254.2 0.994 1.72 206.9 0.987 209.1 0.986 1.05 120.4 0.999 118.9 0.999 0.76
0.3 253.5 0.994 257.6 0.994 1.59 229.3 0.990 232.2 0.989 1.26 121.4 0.996 119.6 0.996 0.92
0.4 252.2 0.995 255.9 0.994 1.42 228.8 0.992 231.4 0.991 1.12 155.4 0.994 154.7 0.994 0.35
0.5 222.2 0.995 224.0 0.994 0.77 215.6 0.993 217.2 0.993 0.74 172.3 0.996 172.0 0.996 0.15
0.6 219.3 0.994 220.6 0.993 0.58 221.9 0.994 223.5 0.994 0.74 171.9 0.996 171.2 0.996 0.38
0.7 266.4 0.999 269.7 0.988 1.21 238.0 0.989 240.0 0.988 0.82 173.5 0.998 172.5 0.998 0.52
0.8 301.3 0.992 305.7 0.991 1.43 234.3 0.994 235.2 0.994 0.38 162.6 0.984 160.5 0.982 1.06
0.9 315.2 0.993 319.3 0.993 1.28 259.3 0.994 260.5 0.994 0.45 192.1 0.983 190.4 0.980 0.84
Average 254.2 257.5 221.6 223.3 155.4 151.1

Functional expressions of several common response models.

Mechanisms Symbol G(α) f(α)
One-dimensional diffusion D1 α2 12α1 {1 \over 2}{\alpha ^{ - 1}}
Two-dimensional diffusion D2 α + (1 − α)ln(1 − α) [−ln(1 − α)]−1
Three-dimensional diffusion D3 [1(1α)13]2 {\left[ {1 - {{\left( {1 - \alpha } \right)}^{{1 \over 3}}}} \right]^2} 32(1α)23[1(1α)13]1 {3 \over 2}{\left( {1 - \alpha } \right)^{{2 \over 3}}}{\left[ {1 - {{\left( {1 - \alpha } \right)}^{{1 \over 3}}}} \right]^{ - 1}}
Avrami-Erofeev A2 [ln(1α)]12 {\left[ { - \ln \left( {1 - \alpha } \right)} \right]^{{1 \over 2}}} 2(1α)[ln(1α)]12 2\left( {1 - \alpha } \right){\left[ { - \ln \left( {1 - \alpha } \right)} \right]^{{1 \over 2}}}
Avrami-Erofeev A3 [ln(1α)]13 {\left[ { - \ln \left( {1 - \alpha } \right)} \right]^{{1 \over 3}}} 3(1α)[ln(1α)]23 3\left( {1 - \alpha } \right){\left[ { - \ln \left( {1 - \alpha } \right)} \right]^{{2 \over 3}}}
First-order reaction F1 −ln(1 − α) 1 − α
1.5-order reaction F3/2 2[(1α)12]2 2\left[ {{{\left( {1 - \alpha } \right)}^{-{1 \over 2}}}} \right] - 2 (1α)32 {\left( {1 - \alpha } \right)^{{3 \over 2}}}
Second-order reaction F2 (1 − α)−1 − 1 (1 − α)2
Contracting area R2 1(1α)12 1 - {\left( {1 - \alpha } \right)^{{1 \over 2}}} 2(1α)12 2{\left( {1 - \alpha } \right)^{{1 \over 2}}}
3D contracting volume R3 1(1α)13 1 - {\left( {1 - \alpha } \right)^{{1 \over 3}}} 3(1α)23 3{\left( {1 - \alpha } \right)^{{2 \over 3}}}
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General Interest, Life Sciences, other, Physics