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

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

[i] CFT = cigar filler tobacco; CWT = cigar wrapper tobacco; FCT = flue-cured tobacco

Table 2

Functional expressions of several common response models.

Mechanisms	Symbol	G(α)	f(α)
One-dimensional diffusion	D1	α²	$\frac{1}{2} α^{- 1}$
Two-dimensional diffusion	D2	α + (1 − α)ln(1 − α)	[−ln(1 − α)]⁻¹
Three-dimensional diffusion	D3	${[1 - {(1 - α)}^{\frac{1}{3}}]}^{2}$	$\frac{3}{2} {(1 - α)}^{\frac{2}{3}} {[1 - {(1 - α)}^{\frac{1}{3}}]}^{- 1}$
Avrami-Erofeev	A2	${[- ln (1 - α)]}^{\frac{1}{2}}$	$2 (1 - α) {[- ln (1 - α)]}^{\frac{1}{2}}$
Avrami-Erofeev	A3	${[- ln (1 - α)]}^{\frac{1}{3}}$	$3 (1 - α) {[- ln (1 - α)]}^{\frac{2}{3}}$
First-order reaction	F1	−ln(1 − α)	1 − α
1.5-order reaction	F3/2	$2 [{(1 - α)}^{- \frac{1}{2}}] - 2$	${(1 - α)}^{\frac{3}{2}}$
Second-order reaction	F2	(1 − α)⁻¹ − 1	(1 − α)²
Contracting area	R2	$1 - {(1 - α)}^{\frac{1}{2}}$	$2 {(1 - α)}^{\frac{1}{2}}$
3D contracting volume	R3	$1 - {(1 - α)}^{\frac{1}{3}}$	$3 {(1 - α)}^{\frac{2}{3}}$

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

Table 3

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

Sample	Stage I		Stage II		Stage III
Sample	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

[i] CFT = cigar filler tobacco; CWT = cigar wrapper tobacco; FCT = flue-cured tobacco

Table 4

Characteristic parameters of tobacco leaves during pyrolysis.

Sample	T_S (°C)	T_max (°C)	R_max (% min⁻¹)	R_mean (% min⁻¹)	ΔT_1/2 (°C)	D_i (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

Table 5

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	Aromatics	(42, 43)
966		NH₃	(42)

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

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

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

Arrhenius plots of FWO 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.

Table 6

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
	E_a (kJ mol⁻¹)	Correlation coefficient R²	E_a (kJ mol⁻¹)	Correlation coefficient R²	(%)	E_a (kJ mol⁻¹)	Correlation coefficient R²	E_a (kJ mol⁻¹)	Correlation coefficient R²	(%)	E_a (kJ mol⁻¹)	Correlation coefficient R²	E_a (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

[i] CFT = cigar filler tobacco

[ii] CWT = cigar wrapper tobacco

[iii] FCT = flue-cured tobacco

[iv] FWO = Flynn-Wall-Ozawa method

[v] KAS = Kissinger-Akahira-Sunose method

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

Table 7

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

Sample	Stage	Reaction	Fitted equation	A (min⁻¹)	E_a (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
	III	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
	III	F2	Y = −27020.35x + 33.40	1.73 × 10¹⁷	224.7	0.984

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

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DOI: https://doi.org/10.2478/cttr-2021-0004 | Journal eISSN: 2719-9509 (formerly 1612-9237)

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Language: English, French, German

Page range: 29 - 43

Submitted on: Aug 17, 2020

Accepted on: Feb 17, 2021

Published on: Apr 20, 2021

Published by: Beiträge zur Tabakforschung GmbH

In partnership with: Paradigm Publishing Services

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© 2021 Anran Wang, Bin Cai, Lili Fu, Miao Liang, Xiangdong Shi, Bing Wang, Nan Deng, Bin Li, published by Beiträge zur Tabakforschung GmbH
This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License.

Volume 30 (2021): Issue 1 (March 2021)

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

Figures & Tables

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Figure 9

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