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摘要: 以中国呼伦贝尔褐煤为原料，基于工业分析、元素分析、傅里叶变换红外光谱、气相色谱-质谱联用分析，考察140-230℃预热处理对褐煤650℃等温热解氧迁移的影响。结果表明，与未经预热处理的干煤热解相比，褐煤经200℃预热处理后热解，迁移至热解水和半焦中的氧分别下降7.55%和1.43%，迁移至焦油和气体中的氧分别增加6.66%和1.61%，焦油中酚类氧增加一倍。褐煤预热过程中氢键的减少与热解焦油中正己烷可溶物所含酚类化合物的增加，经原位红外漫反射光谱分析，发现源自OH…π、OH…N和羟基自缔合氢键在预热过程中断裂形成自由OH·，导致酚类化合物中苯酚和甲酚含量增加。Abstract: The effect of preheating treatment (140-230 ℃) on the oxygen migration rule of Hulunbuir lignite which is pyrolyzed at 650 ℃ has been discussed by using the proximate and ultimate analyses, the Fourier transform-infrared spectroscopy, and the gas chromatography-mass spectrometry analysis. Results show that the amount of oxygen migrated to the pyrolysis water and semi-coke is decreased by 7.55% and 1.43%, respectively due to the effect of preheating at 200 ℃. Furthermore, the amount of oxygen transferred to tar and gas is increased by 6.66% and 1.61% respectively, and phenolic oxygen in tar is getting doubled. The decrease of hydrogen bonding and the increase of phenolic compounds are noted as the result of preheating process of lignite, as evidenced by in-situ infrared diffuse reflectance spectroscopy, this could be due to the dissociation of OH…π, OH…N bonds. Hydroxyl self-association hydrogen bonds have also broken down and transformed during the preheating process with the formation of free OH·, which result in the increase of phenol and cresol contents.
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Key words:
- preheating treatment /
- lignite /
- pyrolysis /
- oxygen migration /
- hydrogen bond
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图 2 不同预热处理温度下褐煤热解产物分布
Figure 2 Effect of the preheating temperature on the products distribution during lignite pyrolysis (NO: dry coal)
图 3 不同预热处理温度下褐煤热解产气的组成
Figure 3 Effect of the preheating temperature on the gas components of lignite pyrolysis
a: CO; b:CO2; c: H2; d: CH4
图 4 不同预热处理温度下热解焦油的FT-IR谱图
Figure 4 FT-IR spectra of coal tar from pyrolysis of preheated lignite
图 5 不同预热温度下褐煤热解焦油正己烷可溶物GC-MS分析
Figure 5 GC-MS analysis of n-hexane extracted coal tar obtained from the pyrolysis of preheated lignite
图 6 干煤和预热处理煤热解油中正己烷可溶物中酚类及酚类氧含量分析
Figure 6 Quantitative analysis of phenols (a) and phenolic oxygen (b) present in the n-hexane extracted coal tar
图 7 650 ℃下热解褐煤的氧迁移路径
Figure 7 Oxygen migration paths in coal pyrolysis at 650 ℃
(a): dry lignite; (b): 200 ℃ pretreated lignite
图 8 不同预处理温度下褐煤的原位漫反射光谱谱图
Figure 8 In situ diffuse reflectance spectra of lignite treated at different preheating temperatures
图 9 110 ℃预热处理褐煤的FT-IR光谱分峰拟合谱图
Figure 9 Fitting results of FT-IR spectral peaks for 110 ℃ pretreated lignite
表 1 褐煤的工业分析和元素分析
Table 1 Proximate and ultimate analyses of lignite
Proximate analysis wad/% Ultimate analysis# wdaf/% M A V FC C H O N S 11.44 13.11 33.08 42.37 68.65 4.97 25.92 0.97 0.32 note: # all data are directly detected by vario MACRO cube elementar, detailed measurement methods see section 1.3.1 
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表 2 不同预热处理温度下热解产物中氧分布
Table 2 Distribution of oxygen in pyrolysis products at different preheating temperatures
Temperature t / ℃ Oxygen distribution w/% char-O water-O tar-O gas-O NO 21.00 41.84 2.41 28.49 140 20.97 39.44 5.00 28.36 170 20.94 37.45 6.20 28.98 200 19.57 34.29 9.07 30.10 230 25.54 32.58 6.40 28.41
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表 3 不同预热处理温度下热解焦油各吸收峰透射率
Table 3 Transmittance values of specific functional groups of coal tar obtained from the pyrolysis of preheated lignite
Radical Transmissivity /% NO 140 ℃ 170 ℃ 200 ℃ 230 ℃ -OH (3400 cm-1) 58.84 52.80 46.44 28.45 36.21 C-H (2900 cm-1) 54.15 50.70 41.52 20.48 40.52 C=O (1660 cm-1) 58.43 58.18 53.38 41.25 52.63 C-O (1230 cm-1) 57.59 51.76 44.41 21.45 46.23
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表 4 子峰位置及其归属
Table 4 Location and attribution of sub-peaks
The band assignments of sub-peak Position of sub-peak σ /cm-1 Free OH 3611±5 OH…π hydrogen bond 3538±4 Self-associated OH 3415±5 OH…ether hydrogen bond 3300±2 Cyclic OH tetramers 3150±8 Aromatic C-H 3050±2 OH…N hydrogen bond 2940±4 Aliphatic C-H 2857±1
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表 5 不同预热温度酚羟基及酚羟基氢键定量
Table 5 Quantitative of phenolic hydroxyl group and hydrogen bond at different preheating temperatures
Temperature t/ ℃ Ar-OH / (mmol·g-1) Free OH / (mmol·g-1) Hydrogen bond /(mmol·g-1) OH…π self-associated OH OH…O cyclic OH tetramers OH…N NO 3.11 0.14 0.73 1.20 0.51 0.08 0.45 140 3.10 0.17 0.73 1.18 0.51 0.08 0.43 170 3.10 0.28 0.68 1.13 0.53 0.08 0.40 200 3.09 0.77 0.54 0.93 0.49 0.06 0.30 note: Ar-OH is phenolic hydroxyl group
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