氧化改性活性炭吸附脱氮选择性研究

Effects of oxidative modification of carbon surface on selective removal of nitrogen compounds from model fuel

以芳烃萘作为参照物,研究了超大比表面积活性炭MSC-30对喹啉、吲哚和咔唑的吸附选择性。进一步采用3种不同的氧化改性方法对MSC-30活性炭进行了氧化改性,考察氧化改性对活性炭吸附脱氮选择性的影响。结果表明,该活性炭及氧化改性样品选择性吸附脱氮。氧化改性后,活性炭对氮化物的选择性进一步提高,并且对氮化物的吸附量增加。通过量子化学密度泛函理论(DFT)对目标吸附质的前线轨道能量分布进行计算,结果证明,活性炭对于氮化物的吸附选择性高于对芳烃萘的选择性,这和吸附质的反应活泼顺序一致。氧化改性的活性炭,由于表面含氧基团增加,不利于吸附稳定的萘,而有利于吸附较活泼的吲哚和喹啉,尤其倾向于吸附碱性氮化物喹啉。在强氧化的活性炭样品MSC-N和MSC-NS上,喹啉的吸附量分别高达1.05和1.06mmol/g。

This work examines the adsorptive selectivity of activated carbon （AC） MSC-30 for the nitrogen com pounds, quinoline, indole and carbazole, based on aromatic naphthalene as reference compound. Furthermore, the effects of three different oxidation modification methods on the adsorptive selectivity of AC were investiga- ted. It was found that both of original and modi[ied ACs selectively adsorbed nitrogen compounds. Oxidation modification of AC further improved the selectivity for nitrogen compounds as well as the adsorption capacity of nitrogen compounds. The frontier orbital distribution of target adsorbates was calculated through the density functional theory （DFT） method. The results demonstrated that the higher selectivity for nitrogen compounds than that for aromatic naphthalene was consistent with the order of adsorbates＂ reaction activities. Moreover, due to the increased surface oxygen-containing groups on oxidized activated carbon, they weren＇t beneficial to adsorb stable naphthalene, but favored adsorbing indoles and quinoline, especially tended to adsorb basic quino- line. The adsorptive capacity for quinoline on severely oxidized samples MSC-N and MSC-NS could reach 1.05 and 1.06mmol/g, respectively.