Interaction between functional groups during slow pyrolysis of Naomaohu coal

doi:10.11949/0438-1157.20211530

Abstract

Abstract:

To study the interaction between functional groups during slow pyrolysis of coal, Naomaohu coal (NMHcoal) sample was pyrolyzed in a drop tube furnace reactor with a short residence time to prepare rapid pyrolysis char (NRPchar) with part remained reactivity of coal but most of the low-temperature crosslinking site precursor eliminated. TG results indicated that the pyrolysis of NMHcoal/NRPchar with a ratio of 5∶5 at 500℃ shows a strong negative synergy. The fixed bed pyrolysis results show that some volatiles generated by the pyrolysis of NMHcoal diffused into the NRPchar, which provided more probability and time to the combination of ?CH₃ with aromatic carbon radicals and ?O. As a result, the structure of naphthalenes and phenols containing methyl groups in tar, and also the alkylated oxyaromatic carbon structure and ether structure in the char increased. The increased release of phenols reduced the oxyaromatic carbon structure in the char. More polycyclic aromatic hydrocarbon precursors are generated in NRPchar, they react with phenolic substances to generate polycyclic aromatic hydrocarbons and CO, which increase the content of 5 and 6 ring compounds in the co-pyrolysis tar, while the other part is retained in the semi-coke to reduce its specific surface area.

Key words: pyrolysis, free radical, fixed bed, char, functional group, interaction

摘要：

采用滴管炉，在短停留时间下，制备具有一定低温反应活性而消除主要低温交联位点的淖毛湖煤（NMHcoal）快速热解半焦（NRPchar），再将NMHcoal和NRPchar混合进行慢速热解，研究官能团间的相互作用。热重分析结果表明，NMHcoal/NRPchar混合比为5∶5，温度为500℃热解时具有较强的负协同作用。固定床热解结果表明，NMHcoal热解生成的挥发物部分扩散至NRPchar中，?CH₃与芳碳自由基以及?O有更多的结合概率与时间，使焦油中含甲基的萘、酚类增多，半焦中烷基化邻氧芳碳结构与醚类结构增加。析出的酚类增多，使半焦中连氧芳碳结构减少。NRPchar中生成较多的多环芳烃前体，它们与酚类物质发生反应生成多环芳烃和CO，使共热解焦油中5、6环化合物含量增加，而另一部分滞留在半焦中使其比表面积降低。

关键词: 热解, 自由基, 固定床, 半焦, 官能团, 相互作用

CLC Number:

TQ 530.2

Yingjie YANG, He YANG, Jialong ZHU, Shuangqi GUO, Yan SHANG, Yang LI, Lijun JIN, Haoquan HU. Interaction between functional groups during slow pyrolysis of Naomaohu coal[J]. CIESC Journal, 2022, 73(2): 865-875.

杨英杰, 杨赫, 朱家龙, 郭双淇, 尚妍, 李扬, 靳立军, 胡浩权. 淖毛湖煤慢速热解过程官能团相互作用[J]. 化工学报, 2022, 73(2): 865-875.

Figures/Tables 17

Fig.1 Schematic diagram of drop tube furnace experimental system

Table 1 Proximate and ultimate analyses of NMHcoal and NRPchar

样品	工业分析/%(质量)			元素分析/%(质量，daf)
样品	M_ad	A_d	V_daf	C	H	N	O	S
NMHcoal	3.37	5.29	54.83	71.64	6.01	0.85	21.08	0.42
NRPchar	2.43	10.36	14.37	90.19	1.46	2.25	5.33	0.77

Fig.2 Schematic diagram of the fixed-bed equipment for coal pyrolysis

Fig.3 FT-IR spectra of NMHcoal and NRPchar

Fig.4 Fitting curves of NMHcoal and NRPchar in 2800—3000 cm-1

Table 2 Fitting results of NMHcoal and NRPchar in 2800—3000 cm-1

峰位置/cm^-1	峰归属	峰面积的比例
峰位置/cm^-1	峰归属	NMHcoal	NRPchar
2825	O—CH₃	3.20	3.39
2851、2920	sym.R₂CH₂、asym.R₂CH₂	61.60	54.97
2874、2953	sym.RCH₃、asym.RCH₃	24.69	22.94
2893	R₃CH	10.51	18.69

Fig.5 TG/DTG curves of NMHcoal /NRPchar co-pyrolysis

Table 3 Characteristic parameters of NMHcoal， NRPchar and NMHcoal/NRPchar pyrolysis

样品	初温/ ℃	峰温/ ℃	终温/ ℃	失重量/%		DTG_max/(%/℃)
样品	初温/ ℃	峰温/ ℃	终温/ ℃	实验值	加权平均值	实验值	加权平均值
NMHcoal	201	443	636	47.3	—	-0.215	—
NRPchar	368	—	—	22.3	—	-0.058	—
20% char	197	443	637	41.8	42.3	-0.166	-0.175
40% char	203	443	625	34.8	37.3	-0.134	-0.134
50% char	209	442	625	32.7	34.8	-0.101	-0.114
60% char	203	443	608	29.5	32.3	-0.097	-0.094
80% char	207	443	583	24.6	27.3	-0.055	-0.054

Fig.6 FT-IR spectra of NMHcoal/NRPchar(5∶5) at different temperature

Table 4 Main single-ring， polycyclic aromatic compounds and long-chain aliphatic hydrocarbons detected in tar samples obtained from pyrolysis of NMHcoal， NRPchar and their mixtures at 500℃

序号	化合物	NMHcoal-fb	NMHcoal/NRPchar-fb	NRPchar-fb
1环芳香化合物
1	甲苯	0.806	0.243	0.732
2	乙苯	0.366	0.206	0.058
3	对二甲苯	1.400	0.594	0.409
4	1,2,3-三甲苯	1.362	1.194	—
5	苯酚	6.274	5.582	1.548
6	2-甲基苯酚	9.222	8.639	0.916
7	2,6-二甲基苯酚	10.04	6.08	—
8	2-乙基苯酚	0.475	1.709	—
9	3-甲基-1,2-苯二酚	0.715	2.765	—
10	2,3,6-三甲基苯酚	0.371	0.840	—
11	4,5-二甲基-1,3-苯二酚	0.445	0.594	—
12	4-乙基-1,3-苯二酚	0.431	0.814	—
2环芳香化合物
13	茚	0.437	0.280	0.061
14	萘	1.238	1.647	66.852
15	4,7-二甲基苯并呋喃	0.317	0.230	—
16	1,3-二甲基-1-氢茚	0.85	1.006	—
17	2,3-二氢化-5-羟基茚	0.744	1.236	—
18	2-甲基萘	3.377	2.912	—
19	2,6-二甲基萘	3.117	2.844	—
20	1,4,6-三甲基萘	3.266	4.052	—
21	2-甲基-1-萘酚	3.388	3.994	—
3环以上芳香化合物
22	1-甲基-9H-笏	0.268	0.874	—
23	菲	—	1.132	5.773
24	3,6-二甲基菲	0.187	—	—
25	2,3,5-三甲基菲	—	0.131	—
26	芘		0.974	4.428
27	荧蒽	—	—	5.437
28	苯并芘	—	0.340	1.080
29	苯并荧蒽	—	1.692	—
30	苝	0.166	0.405	—
31	苯并苝	—	0.548	0.117
长链脂肪烃化合物
32	十一烷	0.741	0.552	—
33	十二烷	0.958	1.567	—
34	十四烷	1.058	1.383	—
35	十五烷	1.009	1.165	—
36	十七烷	1.004	1.100	—
37	十八烷	0.945	0.947	—
38	十九烷	0.873	0.962	—
39	二十烷	0.909	1.025	—
40	二十一烷	1.005	1.154	—
41	二十二烷	1.110	1.170	—
42	二十三烷	1.357	1.445	—
43	二十四烷	1.170	1.035	—
44	二十五烷	1.019	2.473	—

Fig.7 Gas production during pyrolysis of NMHcoal-fb, NRPchar-fb and NMHcoal/NRPchar (5∶5) -fb

Fig.8 Synergetic effects from single-ring, polycyclic aromatic compounds and long-chain aliphatic hydrocarbons obtained from NMHcoal/NRPchar (5∶5)at 500℃ (The numbers 1—44 on x-axis correspond to the compounds in Table 4)

Fig.9 N2 adsorption/desorption isotherms (a) and pore size distributions (b) of char

Table 5 Specific surface area and pore structure parameters of char

样品	比表面积/ (m²/g)	孔容/ (cm³/g)	孔径/nm
NMHcoal-fb	10.7	0.016	5.44
NRPchar-fb	285.9	0.171	4.27
NMHcoal/NRPchar-fb（实验值）	105.0	0.088	4.23
NMHcoal/NRPchar -fb（加权平均值）	148.3	0.093	4.86

Fig.10 FT-IR spectra of NMHcoal, NRPchar and their blends in fixed bed at 500℃

Fig.11 13C NMR spectra and their fitting curves for NMHcoal-fb and NMHcoal /NRPchar(5∶5)-fb

Table 6 Distribution of carbon types in NMHcoal-fb and NMHcoal /NRPchar（5∶5）-fb

峰	碳类型	符号	峰化学位移		摩尔分取/%
峰	碳类型	符号	NMHcoal-fb	NMHcoal/NRPchar-fb	NMHcoal-fb	NMHcoal/NRPchar-fb
脂肪碳
1	脂肪甲基	$f a l M$	12.2	11.0	1.64	0.74
2	芳环甲基	$f a l A$	20.2	20.3	3.13	1.24
3	亚甲基	$f a l H$	30.2	29.2	1.36	0.99
4	次甲基	$f a l D$	36.8	36.1	1.88	1.67
5	季碳	$f a l D$	45.5	45.9	2.23	2.81
6	连氧脂肪碳	$f a l O$	55.5 67.6 86.0	55.0 66.7 88.0	15.12	16.98
总					25.36	24.43
芳碳
7	质子化邻氧芳碳	$f a O 1$	108.9	108	5.49	5.96
8	烷基化邻氧芳碳	$f a O 2$	116.1	116.8	4.78	7.64
9	质子化芳碳	$f a H$	122	122.3	7.13	7.86
10	桥头芳碳	$f a B$	129	128.6	23.61	24.29
11	烷基取代芳碳	$f a S$	138.9 147.1	138.8 147.8	13.13	11.06
12	连氧芳碳	$f a O 3$	155 165	155 165	6.51	4.45
总					60.65	61.26
羰基
13	羧基、酯的羰基碳	$f a C 1$	178.5	176.3	1.55	1.02
14	酮、醛的碳	$f a C 2$	199.3	197.3	12.41	13.27
总					13.96	14.29

Table 6 Distribution of carbon types in NMHcoal-fb and NMHcoal /NRPchar（5∶5）-fb

峰	碳类型	符号	峰化学位移		摩尔分取/%
峰	碳类型	符号	NMHcoal-fb	NMHcoal/NRPchar-fb	NMHcoal-fb	NMHcoal/NRPchar-fb
脂肪碳
1	脂肪甲基	$f a l M$	12.2	11.0	1.64	0.74
2	芳环甲基	$f a l A$	20.2	20.3	3.13	1.24
3	亚甲基	$f a l H$	30.2	29.2	1.36	0.99
4	次甲基	$f a l D$	36.8	36.1	1.88	1.67
5	季碳	$f a l D$	45.5	45.9	2.23	2.81
6	连氧脂肪碳	$f a l O$	55.5 67.6 86.0	55.0 66.7 88.0	15.12	16.98
总					25.36	24.43
芳碳
7	质子化邻氧芳碳	$f a O 1$	108.9	108	5.49	5.96
8	烷基化邻氧芳碳	$f a O 2$	116.1	116.8	4.78	7.64
9	质子化芳碳	$f a H$	122	122.3	7.13	7.86
10	桥头芳碳	$f a B$	129	128.6	23.61	24.29
11	烷基取代芳碳	$f a S$	138.9 147.1	138.8 147.8	13.13	11.06
12	连氧芳碳	$f a O 3$	155 165	155 165	6.51	4.45
总					60.65	61.26
羰基
13	羧基、酯的羰基碳	$f a C 1$	178.5	176.3	1.55	1.02
14	酮、醛的碳	$f a C 2$	199.3	197.3	12.41	13.27
总					13.96	14.29

References 32

1	Wang N, Yu J L, Tahmasebi A, et al. Experimental study on microwave pyrolysis of an Indonesian low-rank coal[J]. Energy & Fuels, 2014, 28(1): 254-263.
2	袁帅, 陈雪莉, 李军, 等. 煤快速热解固相和气相产物生成规律[J]. 化工学报, 2011, 62(5): 1382-1388.
	Yuan S, Chen X L, Li J, et al. Formations of solid and gas phase products during rapid pyrolysis of coal[J]. CIESC Journal, 2011, 62(5): 1382-1388.
3	Wang Z Q, Bai Z Q, Li W, et al. Quantitative study on cross-linking reactions of oxygen groups during liquefaction of lignite by a new model system[J]. Fuel Processing Technology, 2010, 91(4): 410-413.
4	Ibarra J V, Cervero I, García M, et al. Influence of cross-linking on tar formation during pyrolysis of low-rank coals[J]. Fuel Processing Technology, 1990, 24: 19-25.
5	王志青, 白宗庆, 李文, 等. 吡啶预处理抑制煤热解过程中交联反应的研究[J]. 燃料化学学报, 2008, 36(6): 641-645.
	Wang Z Q, Bai Z Q, Li W, et al. Suppressing cross-linking reactions during pyrolysis of lignite pretreated by pyridine[J]. Journal of Fuel Chemistry and Technology, 2008, 36(6): 641-645.
6	Li J G, Zhu J L, Hu H Q, et al. Co-pyrolysis of Baiyinhua lignite and pine in an infrared-heated fixed bed to improve tar yield[J]. Fuel, 2020, 272: 117739.
7	Chen Y Y, Mastalerz M, Schimmelmann A. Characterization of chemical functional groups in macerals across different coal ranks via micro-FTIR spectroscopy[J]. International Journal of Coal Geology, 2012, 104: 22-33.
8	Haykiri-Acma H, Yaman S. Interaction between biomass and different rank coals during co-pyrolysis[J]. Renewable Energy, 2010, 35(1): 288-292.
9	王刚, 李爱民, 全翠. 生物质与聚乳酸塑料共热解特性[J]. 化工学报, 2009, 60(7): 1787-1792.
	Wang G, Li A M, Quan C. Thermal decomposition of biomass/polylactic acid during co-pyrolysis[J]. Journal of Chemical Industry and Engineering(China), 2009, 60(7): 1787-1792.
10	Zhang Y, Zhang X Q, Zhong Q F, et al. Structural differences of spontaneous combustion prone inertinite-rich Chinese lignite coals: insights from XRD, solid-state ¹³C NMR, LDIMS, and HRTEM[J]. Energy & Fuels, 2019, 33(5): 4575-4584.
11	Jing Z H, Rodrigues S, Strounina E, et al. Use of FTIR, XPS, NMR to characterize oxidative effects of NaClO on coal molecular structures[J]. International Journal of Coal Geology, 2019, 201: 1-13.
12	Solum M S, Pugmire R J, Grant D M. ¹³C solid-state NMR of Argonne-premium coals[J]. Energy & Fuels, 1989, 3(2): 187-193.
13	Cao S Q, Wang D C, Wang M Y, et al. In‐situ upgrading of coal pyrolysis tar with steam catalytic cracking over Ni/Al₂O₃catalysts[J]. ChemistrySelect, 2020, 5(16): 4905-4912.
14	Zhu J L, Jin L J, Luo Y W, et al. Fast co-pyrolysis of a massive Naomaohu coal and cedar mixture using rapid infrared heating[J]. Energy Conversion and Management, 2020, 205: 112442.
15	陈宗定, 王永刚, 许德平, 等. 褐煤热解过程中半焦重整催化剂性质的变化[J]. 燃料化学学报, 2017, 45(8): 908-915.
	Chen Z D, Wang Y G, Xu D P, et al. Changes in char properties after catalytic reforming volatiles from pyrolysis of brown coal[J]. Journal of Fuel Chemistry and Technology, 2017, 45(8): 908-915.
16	Mae K, Maki T, Miura K. A new method for estimating the cross-linking reaction during the pyrolysis of brown coal[J]. Journal of Chemical Engineering of Japan, 2002, 35(8): 778-785.
17	Qiu S X, Zhang S F, Zhou X H, et al. Thermal behavior and organic functional structure of poplar-fat coal blends during co-pyrolysis[J]. Renewable Energy, 2019, 136: 308-316.
18	Fletcher T H, Hardesty D R. Compilation of Sandia coal devolatilization data: milestone report[R]. Livermore, CA, USA: Sandia National Laboratories, 1992.
19	Solomon P R, Serio M A, Carangelo R M, et al. Very rapid coal pyrolysis[J]. Fuel, 1986, 65(2): 182-194.
20	Niu Z Y, Liu G J, Yin H, et al. In-situ FTIR study of reaction mechanism and chemical kinetics of a Xundian lignite during non-isothermal low temperature pyrolysis[J]. Energy Conversion and Management, 2016, 124: 180-188.
21	Xiong G, Li Y S, Jin L J, et al. In situ FT-IR spectroscopic studies on thermal decomposition of the weak covalent bonds of brown coal[J]. Journal of Analytical and Applied Pyrolysis, 2015, 115: 262-267.
22	Iglesias M J, del Rı́o J C, Laggoun-Défarge F, et al. Control of the chemical structure of perhydrous coals; FTIR and Py-GC/MS investigation[J]. Journal of Analytical and Applied Pyrolysis, 2002, 62(1): 1-34.
23	商铁成. 热解温度对低阶煤热解性能影响研究[J]. 洁净煤技术, 2014, 20(6): 28-31.
	Shang T C. Influence of temperature on pyrolysis properties of low rank coal[J]. Clean Coal Technology, 2014, 20(6): 28-31.
24	Liang L T, Huang W, Gao F X, et al. Mild catalytic depolymerization of low rank coals: a novel way to increase tar yield[J]. RSC Advances, 2015, 5(4): 2493-2503.
25	杨亚慧. 淖毛湖煤慢速热解过程化学渗透热解模型研究[D]. 大连: 大连理工大学, 2021.
	Yang Y H. Study on chemical percolation devolatilization model for slow pyrolysis process of NMH coal[D]. Dalian: Dalian University of Technology, 2021.
26	Wu Y F, Zhu J L, Zhao S, et al. Co-pyrolysis behaviors of low-rank coal and polystyrene with in-situ pyrolysis time-of-flight mass spectrometry[J]. Fuel, 2021, 286: 119461.
27	陈霞, 徐艳梅, 陆人春, 等. 淖毛湖煤及显微组分热解半焦微观结构分析[J]. 高校化学工程学报, 2020, 34(3): 831-837.
	Chen X, Xu Y M, Lu R C, et al. Microstructure analysis of char from pyrolysis of Naomaohu coal and macerals[J]. Journal of Chemical Engineering of Chinese Universities, 2020, 34(3): 831-837.
28	韩峰, 张衍国, 蒙爱红, 等. 云南褐煤结构的FTIR分析[J]. 煤炭学报, 2014, 39(11): 2293-2299.
	Han F, Zhang Y G, Meng A H, et al. FTIR analysis of Yunnan lignite[J]. Journal of China Coal Society, 2014, 39(11): 2293-2299.
29	Peng C N, Zhang G Y, Yue J R, et al. Pyrolysis of black liquor for phenols and impact of its inherent alkali[J]. Fuel Processing Technology, 2014, 127: 149-156.
30	Yang F, Hou Y C, Wu W Z, et al. A new insight into the structure of Huolinhe lignite based on the yields of benzene carboxylic acids[J]. Fuel, 2017, 189: 408-418.
31	Xiong Y K, Jin L J, Li Y, et al. Structural features and pyrolysis behaviors of extracts from microwave-assisted extraction of a low-rank coal with different solvents[J]. Energy & Fuels, 2019, 33(1): 106-114.
32	Li L, Fan H J, Hu H Q. A theoretical study on bond dissociation enthalpies of coal based model compounds[J]. Fuel, 2015, 153: 70-77.

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