XPS study on transformation of N- and S-functional groups during pyrolysis of high sulfur New Zealand coal
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摘要: 选择一种高硫新西兰煤(NXL)作为研究对象,高纯Ar气氛中,以5℃/min的升温速率在管式炉中热解,热解终温为300~1 000℃。用XPS研究煤及不同温度下半焦中氮、硫的赋存形态。将N 1s谱图用Lorentzian-Gaussian拟合分为四个峰:N-6(398.8±0.4)eV、N-5(400.2±0.3)eV、N-Q(401.4±0.3)eV和N-X(402.9±0.5)eV;S 2p谱图分为六个峰:硫铁矿(162.5±0.3)eV、硫化物(163.3±0. 4)eV、噻吩(164.1±0.2)eV、亚砜(166.0±0.5)eV、砜(168.0±0.5)eV和硫酸盐硫(169.5±0.5)eV。结果表明,煤中氮元素的主要存在形式是吡啶、吡咯、质子化吡啶和氮氧化物;低于600℃,半焦中的氮元素主要以吡啶和吡咯形式存在;随温度的升高,吡咯向吡啶转化;当温度超过900℃,氮氧化物这一形态消失。该煤中的硫以有机硫为主,其中,噻吩硫占50%以上;随着热解温度的升高,煤中的硫铁矿硫逐步转化为无机硫化物,600℃时分解完全。Abstract: X-ray photoelectron spectroscopy (XPS) was used to investigate the nitrogen and sulfur functional forms present in New Zealand coal (NXL) and its pyrolysis char prepared under argon atmosphere at 8 different temperatures between 300 and 1 000℃. The N 1s spectra obtained were curve-resolved into 4 peaks: pyridinic-N (398.8±0.4 eV), pyrrolic-N (400.2±0.3 eV), quaternary-N (401.4±0.3 eV) and nitrogen oxides (402.9±0.5 eV); and S 2p peaks into 6 peaks: pyrite (162.5±0.3 eV), sulphidic (163.3±0.4 eV), thiophenic (164.1±0.2 eV), sulfoxide (166.0±0.5 eV), sulfones (168.0±0.5 eV) and sulfate (169.5±0.5 eV). The results show that nitrogen present in coal in pyrrolic forms is converted into pyridinic functionalities upon heat treatment and nitrogen oxides disappeared above 900℃. The major organic sulfur form in NXL is thiophene and its content is over 50%. Pyrite is decomposed completely into troilite at 600℃.
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Key words:
- XPS /
- high sulfur coal /
- pyrolysis /
- nitrogen transformation /
- sulfur transformation
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