Effect of Fe2O3 on the pyrolysis of two demineralized coal using in-situ pyrolysis photoionization time-of-flight mass spectrometry
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摘要: 利用原位热解真空紫外单光子电离飞行时间质谱系统研究了Fe2O3对脱矿红沙泉和大柳塔煤热解产物分布的影响。实验所用样品是经酸洗脱矿物质后的煤与Fe2O3以10∶1、5∶1和2∶1的质量比机械混合得到。在该热解检测系统中,由于原位捕捉、软电离和高真空环境的特点可以检测到热解初始挥发产物,主要包括烯烃、芳烃、单酚、双酚及少量含硫和含氮物质。结果表明,Fe2O3对两种脱矿煤的热解产物分布具有相似的影响规律,但对脱矿大柳塔煤的影响较为明显。随着Fe2O3添加量的增加,产物中烯烃、芳烃等轻质组分含量增加,双酚类的含量明显降低,重质产物的含量也有所降低,但产物的逸出峰值温度提高。Fe2O3在使重组分向轻质组分转变的同时,自身被还原成FeO并进一步还原成Fe。煤热解过程中形成产物的脂碳(或芳烃取代碳)愈多,其产生的峰值温度愈低。Abstract: Influence of Fe2O3 on the pyrolysis products distribution of demineralized Hongshaquan (HSQ) and Daliuta (DLT) coal was investigated by a novel in-situ pyrolysis vacuum ultraviolet single photon ionization time-of-flight mass spectrometry. The experiment samples were obtained by mechanical mixing of Fe2O3 and demineralized coal from acid elution with the mass ratio of 10∶1, 5∶1 and 2∶1. Due to the characteristics of in-situ sampling, soft ionization and high vacuum environment, the initial pyrolysis volatiles including alkenes, aromatic hydrocarbons, phenols, bi-phenols and a small amount of sulfur and nitrogen-containing substances can be detected. The results show that Fe2O3 has similar influence on the products distribution of two demineralized coal, and it is relatively stronger on DLT coal than that on HSQ. With the increase of Fe2O3 content, the light fraction content is promoted such as alkenes and aromatic hydrocarbons, but bi-phenols are obviously inhibited. Correspondingly, the heavy products are also decreased, and the evolution peak temperatures of the product increase. Fe2O3 is successively reduced to FeO and Fe while transforming heavy components into light components. The increase of aliphatic carbon (or aromatic hydrocarbon substituted carbon) during coal pyrolysis process is mainly responsible for the decrease pyrolysis peak temperature.
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Key words:
- coal pyrolysis /
- photoionization /
- primary volatiles /
- PI-TOF MS /
- Fe2O3
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图 1 原位热解光电离飞行时间质谱装置示意图[12]
Figure 1 Schematic diagram of Py-VUVPI-TOF-MS[12]
图 8 添加Fe2O3前后大柳塔脱矿煤的主要热解产物:(a) DLTDM及DLTDM:Fe2O3 = 5∶1的主要热解产物的相对含量;(b) 热解产物分类汇总和重质产物相对含量
Figure 8 Relative content of main pyrolysis products of DLTDM coal samples with and without addition of Fe2O3: (a) relative content of main pyrolysis products; (b) different types of pyrolysis products and relative content of heavy products
表 1 大柳塔、红沙泉原煤及其脱矿煤的工业分析和元素分析
Table 1 Proximate and ultimate analyses of coal samples
Coal sample Proximate analysis w/% Ultimate analysis wdaf/% H/C Mad Ad Vdaf C H N S O* DLT 1.43 13.93 34.06 78.32 4.75 1.09 0.62 15.22 0.73 DLTDM 1.13 0.30 32.09 78.62 4.67 0.99 0.45 15.27 0.71 HSQ 3.15 7.60 35.43 76.30 4.85 1.08 0.12 17.65 0.76 HSQDM 1.96 0.11 37.59 76.56 4.72 1.06 0.08 17.58 0.74 *: by difference 表 2 大柳塔和红沙泉原煤的灰成分分析
Table 2 XRF analyses of DLT and HSQ coal ashes
Sample Content w/% Fe2O3 SiO2 Al2O3 Na2O CaO K2O SO3 MgO other* DLT 7.82 52.56 17.22 1.02 11.58 1.47 6.29 0.69 1.35 HSQ 14.83 43.44 19.70 3.34 8.47 0.47 3.92 4.00 1.83 *: by difference 表 3 煤原位热解光电离飞行时间质谱检测主要热解产物归属
Table 3 Mass attribution of main pyrolysis products of coal via in-situ Py-VUVPI-TOF MS
m/z Name Formula Formula IE/eVa 28 ethylene C2H4 10.51 42 propylene C3H6 9.73 56 butene/methylcyclopropane C4H8 9.10/9.30 70 pentene/ethylcyclopropane C5H10 9.04/8.96 78 benzene C6H6 9.244 84 cyclohexane/hexene C6H12 9.88/8.97 92 toluene C7H8 8.828 94 phenol C6H6O 8.49 106 dimethylbenzene/ethylbenzene C8H10 8.44/8.77 108 methylphenol/anisole C7H8O 8.29/8.20 110 benzenediol C6H6O2 7.94 120 trimethylbenzene C9H12 8.4 124 guaiacol/methylbenzenediol C7H8O2 134 tetramethylbenzene C10H14 8.06/8.29 136 2,4,6-trimethyl phenol C9H12O 8.00 138 ethoxyphenol/dimethoxybenzene C8H10O2 8.49/7.80 142 methylnaphthalene C11H10 7.96 144 naphthalenol C10H8O 7.89 146 coumarin C9H6O2 8.72 156 dimethylnaphthalene C12H12 8.11 158 methoxynaphthalene/methylnaphthalenol C11H10O 7.82/7.72 160 1,8-naphthalenediol C10H8O2 7.62 170 trimethylnaphthalene C13H14 174 methylnaphthalenediol C11H10O2 178 phenanthrene/anthracene C14H10 7.44/7.89 a: IE values with reference to NIST Chemistry Web Book[15] -
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