先锋褐煤在水热处理过程中的结构演绎

刘鹏; 周扬; 鲁锡兰; 王岚岚; 潘铁英; 张德祥

先锋褐煤在水热处理过程中的结构演绎

基金项目:

国家重点基础研究发展规划 973计划, 2011CB201304

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中图分类号: TQ520.61
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出版历程
- 收稿日期: 2015-09-14
- 修回日期: 2015-11-01

Structural evolution of Xianfeng lignite during hydrothermal treatment

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Corresponding author: Tel: 021-64252367，E-mail: zdx@ecust.edu.cn

摘要

摘要: 以先锋褐煤 (XF) 为原料, 在高压反应釜中考察了水热处理过程中褐煤的结构变化, 通过¹³C固体核磁共振 (NMR) 和傅里叶变换红外光谱进行了分析表征。结果表明, 在低于240℃的水热处理条件下, 煤有机分子结构中的弱化学键有一定断裂, 含氧官能团逐步减少; 水中氢以离子形态迁移至褐煤中, 处理后褐煤结构中甲基比例先增加后减少, 次甲基比例由原煤的4.80%增加至XF-240的13.16%;释放的气体中主要是CO₂, 烃类气体组分随处理温度的升高略有增加。当水热处理温度高于240℃时, 褐煤中部分共价键开始断裂, 释放的烃类气体 (C_1-4) 由240℃时的2.13%增加至300℃时的8.59%, 脂肪碳比例由XF-240的44.83%降低至XF-300的39.49%, 与氧连接的碳比例由XF-240的12.57%降低至XF-300的1.49%。水热处理对褐煤的脱氧提质效果显著, 300℃时氧含量降低约30%, 芳香碳比例增加至60.50%, 比原煤提高19%。
- 褐煤 /
- 水热处理 /
- ¹³C固体核磁共振 /
- 碳结构 /
- 氢转移
Abstract: Xianfeng lignite (XF) was used as raw material to investigate its structural evolution during hydrothermal treatment in a 500 mL autoclave.The structure was characterized by solid state ¹³C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR).The results show that the carbon contents increase and oxygen contents decrease after hydrotnermal treatment.The weak bonds in lignite are broken and the oxygen functional groups decrease gradually during hydrothermal treatment below 240℃.Hydrogen is donated from water to lignite through ionic pathway and transferred into lignite.The methyl carbon increases at 200℃ and then decreases.The methenyl carbon increases from 4.80% in XF to 13.16% in XF-240.The released gas is mainly CO₂ during hydrothermal treatment.The hydrocarbon composition in released gas increases with the treated temperature.The covalent bonds are broken above 240℃.The hydrocarbon composition in released gas increases from 2.13% at 240℃ to 8.59% at 300℃.The aliphatic carbon in lignite deceases from 44.83% in XF-240 to 39.49% in XF-300.The oxygen-linked carbon in lignite decreases from 12.57% in XF-240 to 1.49% in XF-300.Hydrothermal treatment plays a role in deoxygenation and upgrading of raw lignite.The oxygen contents decrease by about 30% and the aromatic carbon increases to 60.50% at 300℃.
- lignite /
- hydrothermal treatment /
- ¹³C-NMR /
- carbon structure /
- hydrogen transfer

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图 1 ¹³C-NMR波谱谱图

Figure 1. ¹³C-NMR spectra

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图 2 ¹³C-NMR谱图分峰拟合模拟图

Figure 2. Fitted ¹³C-NMR spectra

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图 3 FT-IR光谱谱图

Figure 3. Fitted FT-IR spectra

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图 4 XF褐煤水热处理结构演绎图

Figure 4. Schematic for structural evolution of XF during hydrothermal treatment

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表 1 褐煤干燥提质工艺参数

Table 1. Comparison of process parameters of lignite upgrading

Project	Evaporation drying		Non-evaporation drying
Project	WTA	HPU	D-K	MTE	HTD
Temperature t/℃	100-120	105-110	180-240	150-220	220-300
Operating pressure p/MPa	0.30-0.40	atmospheric	17	10	saturated vapor pressure
Heavy water absorption	yes	no	no	no	no
Pore structure	unchanged	decrease	decrease	decrease	decrease
Oxygen content	unchanged	unchanged	decrease	decrease	decrease
Dewaterability t/h	110	110	1	25	-

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表 2 先锋褐煤处理前后工业与元素分析

Table 2. Proximate and ultimate analyses of XF and treated XF

Sample	Recovery ^a w/%	Proximate analyses w/%			Ultimate analyses w_daf /%
Sample	Recovery ^a w/%	A_d	V_daf	FC_daf	C	H	N	S	O ^c
XF	-	8.42	52.58	47.42	71.26	5.06	2.25	0.94	20.49
XF-200 ^b	93.15	8.10	51.51	48.49	72.90	5.07	2.35	0.81	18.87
XF-220	91.89	8.53	49.12	50.88	72.24	4.91	2.42	0.86	19.56
XF-240	90.11	8.45	47.73	52.27	73.11	4.82	2.40	0.87	18.79
XF-260	88.32	8.25	47.85	52.15	75.33	4.65	2.39	0.76	16.87
XF-300	81.76	9.22	43.05	56.95	77.65	4.94	2.22	0.82	14.37
^a: recovery is the mass ratio of treated lignite to raw lignite during hydrothermal treatment; ^b: “XF-200” indicates the IM was treated at 200℃for 30min; ^c: by difference

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表 3 先锋褐煤¹³C-NMR中不同类型碳对应的化学位移

Table 3. Main assignments of chemical shift values for different structural carbons in solid-state ¹³C-NMR spectra of XF lignite

Assignment	Location	Chemical shift δ	Character
Aliphatic methyl	R-CH₃	14-22	f_al³
Aromatic methyl		22-26	f_al^a
Methylene	-CH₂,	26-37	f_al²
Quaternery sp³ C	-CH--C	37-50	f_al¹, f_al^*
Oxygen aliphatic carbon	R-O-R,	50-95	f_al^O
Protonated aromatic carbon		95-124	f_a^H
Bridging ring junction aromatic carbon		124-137	f_a^B
Aliphatic substituted aromatic carbon		137-149	f_a^S
Oxygen aromatic carbon		149-164	f_a^O
Carboxyl, quinone and carbonyl carbon	RCOOH, RCOR	164-220	f_a^CC
f_al³: fraction of aliphatic methyl carbon; f_al^a: fraction of aromatic methyl carbon; f_al²: fraction of methylene carbon; f_al¹: fraction of methine carbon; f_al^*: fraction of carbon that is aliphatic and either quaternary, methyl, or mobile methylene; f_al^O: fraction of total carbon associated with aliphatic ethers and alcohols; f_a^H: protonated aromatic carbon; f_a^B: bridgehead aromatic carbon; f_a^S: alkyl substituted aromatic carbon; f_a^O: oxygenated aromatic carbon; f_a^CC: fraction of carbonyl, quinone and carboxyl carbons

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表 4 XF褐煤含氧官能团在FT-IR光谱谱图中对应的位置

Table 4. Band assignments of oxygen functional groups for the FT-IR spectrum of XF lignite

Wavenumber σ/ cm^-1	Assignment
1690-1720	C-O, ketone, aldehyde and -COOH
1600-1660	conjugated C=O
1450-1600	aromatic C=C
1375-1450	CH₃-Ar, CH₃ and CH₂
1110-1300	C-O phenol
1000-1110	ash, alkyl ethers,
	Si-O and aryl ethers

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表 5 先锋褐煤处理前后不同类型有机碳的分布

Table 5. Carbon structure distributions of the raw and treated XF

Sample	Distribution /%
Sample	f_al³	f_al^a	f_al²	f_al¹+f_al^*	f_al^O	f_a^H	f_a^B	f_a^O	f_a^S	f_a^CC
XF	12.77	14.00	11.35	4.80	5.27	8.91	26.61	5.42	7.22	3.65
XF-200	16.95	15.38	7.81	5.14	1.49	11.80	25.61	7.12	5.27	3.43
XF-220	7.99	17.65	12.71	5.07	1.75	8.65	29.76	3.94	10.18	2.29
XF-240	8.11	17.13	6.43	13.16	0	5.39	31.82	5.38	8.29	4.28
XF-260	6.92	20.52	10.33	6.29	0	6.30	29.21	9.79	8.78	1.87
XF-300	10.34	16.05	9.31	3.79	0	3.86	19.36	35.79	1.49	0
f_al³: fraction of aliphatic methyl carbon; f_al^a: fraction of aromatic methyl carbon; f_al²: fraction of methylene carbon; f_al¹: fraction of methine carbon; f_al^*: fraction of carbon that is aliphatic and either quaternary, methyl, or mobile methylene; f_al^O: fraction of total carbon associated with aliphatic ethers and alcohols; f_a^H: protonated aromatic carbon; f_a^B: bridgehead aromatic carbon; f_a^S: alkyl substituted aromatic carbon; f_a^O: oxygenated aromatic carbon; f_a^CC: fraction of carbonyl, quinone and carboxyl carbons

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表 6 先锋褐煤FT-IR光谱谱图上含氧官能团区域的变化

Table 6. Oxygen functional groups band of the raw and treated XF for the FT-IR spectrum

Peak	Position σ/cm^-1	Assignment	XF area percentage /%	XF-240 area percentage /%
1	1035	alkyl ethers，Si-O	8.62	11.45
2	1100	aryl ethers	6.82	5.69
3	1167	C-O phenol	2.42	0.45
4	1207	C-O phenol	4.40	17.36
5	1269	C-O phenol	3.39	0.42
6	1310	C-O phenol	3.97	4.35
7	1376	CH₃-Ar	5.92	2.20
8	1442	CH₃, CH₂	8.16	13.02
9	1502	aromatic C=C	2.12	2.37
10	1556	aromatic C=C	5.60	0.23
11	1588	aromatic C=C	16.54	8.63
12	1620	conjugated C=O	13.48	26.53
13	1656	conjugated C=O	0.61	0.68
14	1696	carboxyl acids	17.94	6.63

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表 7 褐煤在水热处理过程中析出气体组分的变化

Table 7. Variation of gas composition during hydrothermal treatment

Temperature t/℃	Volume percentage φ/%
Temperature t/℃	H₂	CO	CO₂	CH₄	C₂	C₃	C₄
200	3.41	2.96	92.83	0.80	-	-	-
220	2.11	2.46	94.07	1.00	0.20	0.14	0.02
240	1.17	2.69	94.02	1.58	0.31	0.20	0.03
260	5.91	2.75	88.61	1.97	0.45	0.27	0.04
300	3.39	2.01	86.02	6.11	1.48	0.83	0.16
^*：the hydrothermal treatment temperature

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