前驱体和表面改性过程都影响着活性半焦脱除SO2的活性.在氮气中、800℃下对原料半焦进行热处理,并在固定床反应器上测试了其脱除SO2的活性.利用酸碱滴定、工业分析和元素分析、X-射线光电子能谱(XPS)、傅立叶转换红外光谱(FTIR)等表征原料半焦和活性半焦表面化学性质.结果表明:石墨碳是原料半焦和活性半焦样品表面的主要碳功能团.表面C=O基团(酮、内酯、羰和醌类中)和吡咯-N分别是原料半焦表面的氧、氮功能团.热处理导致半焦表面含氧基团分解、表面含氧和含氮基团分布改变、表面C=O基团(酮、内酯、羰和醌类中)明显下降;而化学吸附氧和水增加,吡咯-N变成类吡啶结构.醚类和π - π* 离域基团的增加提高了活性半焦表面的碱性.热处理提高了活性半焦脱除SO2的活性.影响SO2脱除活性的表面基团可能是具有碱性性质的醚类、π - π* 离域及含氮基团.
The activity of SO2 removal by activated semi-coke is influenced by the precursor and surface modification processes. Raw semi-coke was modified by heat treatment at 800℃ in a nitrogen flow, and its activity for SO2 removal was tested in a fixed bed reactor. The surface chemical properties of both raw semi-coke and activated semi-coke were characterized by acid-base titration, XPS, and FTIR. Graphitic carbon was the major component of carbon functional groups in the surface of both raw semi-coke and activated semi-coke. Surface C=O groups in the forms of ketone, lactone, carbonyl, or quinone were the main surface oxygen functional groups, and pyrrolic and/or pyridon-N groups were the main nitrogen functional groups in raw semi-coke. The heat treatment resulted in the decomposition of surface oxygen functional groups and the redistribution of surface oxygen and nitrogen functional groups. The content of the surface carbon groups, such as C=O decreased dramatically after heat treatment. However, the content of surface oxygen functional groups, such as ethers and chemisorbed oxygen or water increased on the surface of activated semi-coke. The number of pyridine-like structures was increased by the removal of pyrrolic and/or pyridon-N groups in the activation process. The increase of ethers group and π - π* transitions in aromatic systems, and the change of the nitrogen functional groups increased the surface basicity for activated semi-coke. Activated semi-coke had the higher activity for SO2 removal than did raw semi-coke. The surface features influencing the activity for SO2 removal for activated semi-coke may be ethers, aromatic carbons and nitrogen functional groups with basicity.
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