预氧化对煤表面关键官能团影响的实验研究
Experimental study for the effect of pre-oxidization on functional groups of coal surface
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摘要: 为探讨氧化后煤表面关键官能团的演化规律，对六家褐煤、四台褐煤、同忻烟煤和白芨沟无烟煤进行了预氧化处理，预氧化温度为50、120、200 ℃，预氧化时间为6 h；采用傅里叶变换红外光谱仪对原始煤样和预氧化煤样进行红外光谱测试，获得氧化前后煤表面关键官能团的变化规律。结果表明：预氧化过程不会改变煤样官能团种类，只会改变其含量大小；预氧化温度越高，在初次氧化过程中参与反应的-OH官能团数量越多；200 ℃预氧化6 h后，六家褐煤预氧化煤样中-OH官能团含量较原始煤样下降51.43%，说明预氧化过程对变质程度低的煤种影响更大；同一煤种的各预氧化煤样，随着预氧化温度的升高-CH2-、-CH3和-C=O官能团数量较原始煤样都呈现出先升高后下降的趋势；其中，预氧化温度为50℃的预氧化煤样中-CH2-、-CH3和-C=O官能团数量较原始煤样升高，而预氧化120 ℃和200 ℃的预氧化煤样中-CH2-、-CH3和-C=O官能团数量较原始煤样降低；当再次发生氧化时，50 ℃预氧化煤样较原始煤样生成CO、CO2、C2H4和C2H6等气体初始温度更低、生成量更大，120 ℃和200 ℃预氧化煤样则相反。Abstract: In order to investigate the evolution law of the functional groups of pre-oxidized coal samples, lignite from Liujia and Sitai, bituminous coal from Tongxin and anthracite from Baijigou were pre-oxidized at 50 ℃, 120 ℃ and 200 ℃ for 6 h. Fourier transform infrared spectrometer was used to test the infrared spectrum of both original and pre-oxidized coal samples. The evolution law of functional groups on the coal surface was obtained. the results showed that: pre-oxidation did not change the type of functional groups, which only changed the amounts of functional groups; The higher is the pre-oxidation temperature, the more functional groups of -OH were involved in the reaction. The absorbance of the -OH decreased 51.43% after the pre-oxidization at 200 ℃, which suggested that the pre-oxidation had more effects on the low metamorphic degree coal; as the pre-oxidation temperature increased, the functional groups of -CH2-, -CH3 and -C=O increased first, and then decreased. For coal samples pre-oxidized at 50 ℃, the amounts of -CH2-, -CH3 and -C=O increased after pre-oxidation; for coal samples pre-oxidized at 120 ℃ and 200 ℃, the amounts of -CH2-, -CH3 and -C=O decreased after pre-oxidation. When the pre-oxidized coal samples were re-oxidized, compared with the original coal samples, the coal samples pre-oxidized at 50 ℃ generated more gases of CO, CO2, C2H4 and C2H6 at a lower temperature, while the coal samples pre-oxidized at 120 ℃ and 200℃ generated less gases at ahigher temperature.
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