杂原子介孔Co-MCM-41分子筛的制备及其吸附脱氮性能

采用水热法合成了介孔MCM-41和Co-MCM-41分子筛,并利用XRD、FT-IR、低温N₂吸附-脱附和NH₃-TPD等方法对合成的分子筛进行了表征。考察了晶化时间、晶化温度、陈化时间对合成介孔Co-MCM-41分子筛的影响,确定较适宜的合成条件为陈化时间1 h,晶化温度110 ℃,晶化时间2 d。XRD 和FT-IR表征结果说明,Co原子已经进入MCM-41的骨架。MCM-41和Co-MCM-41的平均孔径均为2.82 nm,BET比表面积分别为986.42和 637.69 m²/g,孔容分别为0.762 1和0.537 2 m³/g。NH₃-TPD的表征结果表明,MCM-41和Co-MCM-41的酸性都较弱,但Co-MCM-41的酸性明显强于MCM-41。在此基础上,利用合成的MCM-41和Co-MCM-41吸附脱除氮含量为1 737.35 μg/g的模拟燃料中的喹啉。喹啉分子尺寸的模拟结果为0.711 6 nm × 0.500 2 nm,说明其可以很容易地进入MCM-41和Co-MCM-41的介孔孔道中。Co-MCM-41分子筛的氮脱除率明显高于MCM-41,这是由于其较强的酸性及与喹啉之间的化学吸附,而且,Co-MCM-41吸附脱氮具有较好的再生性能。

Preparation and adsorption denitrification of heteroatoms mesoporous molecular sieve Co-MCM-41

The MCM-41 and Co-MCM-41 molecular sieves, prepared by hydrothermal synthesis method, were characterized with X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), nitrogen adsorption and NH₃-TPD. The effects of aging time, crystallization temperature, crystallization time on the crystallization process of MCM-41 and Co-MCM-41 molecular sieves were investigated. The optimal conditions were as follows: 1 h of aging time, 110 ℃ of crystallization temperature and 2 d of crystallization time. XRD and FT-IR results indicated that Co was introduced into the framework of MCM-41. Brunauer-Emmett-Teller (BET) surface area and pore volume of MCM-41 and Co-MCM-41 were 986.42 m²/g, 637.69 m²/g, 0.762 1 m³/g and 0.537 2 m³/g respectively. The average pore diameter was 2.82 nm for both of MCM-41 and Co-MCM-41. The results of TPD showed that although MCM-41 and Co-MCM-41 possessed weak acidity, the acidity of Co-MCM-41 was stronger than MCM-41. Denitrification of model fuels containing about 1 737.35 μg(nitrogen)/g (16.03 mg(quinoline)/g) was studied over the synthesized MCM-41 and Co-MCM-41 with static adsorption at ambient conditions. The molecular size of quinoline, calculated by using density functional theory (DFT), was 0.711 6 nm×0.500 2 nm, implying that the quinoline easily access to the mesopores of MCM-41 and Co-MCM-41. The removal rate of basic nitrogen by Co-MCM-41 was clearly higher than MCM-41 due to its strong acidity and chemisorption between Co-MCM-41 and quinoline. Furthermore, Co-MCM-41 could be easily regenerated.