Mercury removal mechanism of AC prepared by one-step activation with ZnCl2
Mercury removal mechanism of AC prepared by one-step activation with ZnCl2
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DOI：
10.1016/j.fuel.2018.07.103
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发表时间：
2019-01-01
期刊：
影响因子：
7.4
通讯作者：
Qin, Qianwen
中科院分区：
文献类型：
--
作者：
Hong, Dongyang;Zhou, Jinsong;Qin, Qianwen
以不同类型的生物质（玉米秸秆、竹粉和锯末）为原料，采用氯化锌一步活化法制备表面负载ZnO的活性炭，用于煤气中的除汞。在活化过程中，部分ZnCl2转化为ZnO并负载在活性炭上，在H2S存在的情况下，大大提高了除汞性能。生物质中ZnO含量随SiO2含量变化很大，这是由于ZnO失活和Zn2SiO4的形成。在500℃活化后，对除汞很重要的羰基大部分被保留，羰基的数量似乎与比表面积（与木质素含量有关）呈正相关。采用程序升温解吸法对煤中汞的吸附进行了进一步分析。结果表明，ZnO和羰基在除汞过程中起重要作用，而在130℃下的物理吸附作用不显著，仅占约7%。机理研究表明，ZnO作为催化活性位点，在H2S存在下催化Hg-0生成hg。羰基的C=O基团作为吸附位点，吸附后变为C-O。本研究为在煤气中制备汞吸附剂提供了一种很有前途的方法，并对表面官能团的影响进行了详细的研究。
In this work, activated carbon with ZnO laden on the surface was prepared by ZnCl2-one-step activation of different types of biomass (corn straw, bamboo powder and sawdust) and employed for mercury removal in the coal gas. During the activation, a part of ZnCl2 is converted into ZnO and laden on activated carbon, which greatly promotes the mercury removal performance with the presence of H2S. The ZnO content varies greatly with the content of SiO2 in the biomass due to its inactivation of ZnO and formation of Zn2SiO4. Carbonyl, which is important to mercury removal is largely retained after the activation at 500 degrees C and the amount of carbonyl seems to be positively correlated with the specific surface area (related to the lignin content). The temperature programmed desorption method was applied to further analyse the mercury adsorption in the coal gas. The results showed that ZnO and carbonyl play an important role in mercury removal, while the physisorption is not significant and only accounts for approximately 7% at 130 degrees C. The mechanism study showed that ZnO serves as a catalytic active site and catalyses the Hg-0 into HgS with the presence of H2S. While the C=O group of carbonyl acts as adsorption sites and turns into C-O after the adsorption. This study provided a promising preparation method of mercury sorbents in the coal gas, and the influence of surface functional groups was also investigated in detail.