介孔材料Co-MCM-41的合成及其吸附脱除各种碱性氮化物

采用水热法合成了MCM-41和不同Co/Si物质的量比的Co-MCM-41介孔材料,并采用XRD、FT-IR和低温氮气吸附-脱附方法对样品进行了表征。FT-IR及XRD表征结果说明,Co原子已经进入了介孔材料的孔壁。合成的MCM-41及Co/Si(物质的量比)为0.18以下的Co-M CM-41都具有六方有序排列的介孔结构。当加入的Co/Si(物质的量比)为0.22时,样品的(100)峰完全消失,不具备六方有序排列的介孔结构,说明以硝酸钴为钴源合成Co-MCM-41的最大Co加入量为Co/Si(物质的量比)为0.18左右。与MCM-41相比,各Co-MCM-41样品的XRD(100)峰随着Co加入量的增加逐渐变宽变弱,比表面积和孔容变小,平均孔径增大。当加入的Co/Si物质的量比大于0.06时,Co-MCM-41的介孔孔道中存在少量聚集态的Co3O4。利用合成的Co-MCM-41吸附脱除氮含量为1737.35μg/g模拟燃料中的碱性氮化物喹啉、苯胺或吡啶,结果表明,所有样品的吸附脱氮效果顺序为苯胺吡啶喹啉。Co-MCM-41(0.06)的吸附容量和氮脱除率明显要高于其他样品,对苯胺、吡啶和喹啉的吸附容量分别为42.17、35.66和29.18 mg(N)/g,去除率分别为82.38%、73.53%和61.11%。添加到模拟燃料中的芳烃化合物萘、苯或甲苯对其吸附脱氮没有影响,表明介孔材料Co-MCM-41对各种含氮化合物的吸附主要是N原子与Co的配位络合吸附,而不是π-π络合作用。采用焙烧或乙醇溶剂洗涤再生后的Co-MCM-41(0.06)恢复了吸附脱氮能力,说明其具有较好的再生性能。

Preparation of mesoporous Co-MCM-41 and its performance in adsorption removal of various basic nitrogen compounds

The mesoporous materials MCM-41 and Co-MCM-41, with Co/Si(molar ratio)=0.18, were prepared by hydrothermal synthesis method with cobalt nitrate as cobalt source and characterized by X-ray diffraction (XRD), fourier transform infrared spectrometry (FT-IR) and nitrogen adsorption-desorption. XRD and FT-IR results indicated that Co was introduced into the framework of mesoporous materials. The MCM-41 and Co-MCM-41 with highly ordered hexagonal mesoporous structure had been synthesized when the Co/Si(molar ratio) was 0.18 or less. But the sample had lost its ordered hexagonal mesoporous structure when Co/Si(molar ratio) was 0.22, indicating that the maximum addition amount of Co was about Co/Si(molar ratio)=0.18 when Co-MCM-41 was synthesized by using cobalt nitrate as cobalt source. Compared with the MCM-41, the intensity of XRD peak (100) of Co-MCM-41 became weak, broad and its surface area and total pore volume decreased, but the average pore diameter increased with the increase of Co amount. However, there was small amount of highly dispersed Co₃O₄ on the channel surface of Co-MCM-41 samples when the Co/Si(molar ratio) was 0.06 or more. Denitrification of model fuels containing about 1737.35 μg(nitrogen)/g of quinoline, aniline or pyridine was studied over the synthesized Co-MCM-41 with static adsorption at ambient conditions. The sequence of adsorption denitrification performance over all Co-MCM-41 samples was aniline, pyridine and quinoline. The adsorption capacity of Co-MCM-41(0.06) for aniline, pyridine and quinoline was 42.17, 35.66 and 29.18 mg(N)/g and the removal rate of basic nitrogen was 82.38%, 73.53% and 61.11% respectively. The coexisting aromatic compounds in model fuel had little impact on the removal performance of basic nitrogen over Co-MCM-41(0.06), implying that the N-M bond between the adsorption sites and N atom in the compound plays a significant role. Furthermore, Co-MCM-41 could be easily regenerated its adsorption denitrification performance by using calcination or ethanol regeneration method.