MOFs材料MIL-101(Cr)的制备及其吸附脱氮性能研究

Preparation and adsorption denitrification performance of MOFs material MIL-101(Cr)

  • 摘要: 以乙酸替代氢氟酸矿化剂,采用水热合成法制备了四种不同乙酸加入量(0、0.5、1、1.5 mL)的金属有机骨架材料(MOFs)MIL-101(Cr)-0、MIL-101(Cr)-0.5、MIL-101(Cr)-1、MIL-101(Cr)-1.5,采用XRD、SEM、FT-IR以及N2吸附-脱附对MIL-101(Cr)-x进行表征,并用于吸附脱除碱氮含量为1732 μg/g模拟燃料中的吡啶或喹啉,考察吸附时间、吸附温度对其吸附脱氮性能的影响。实验结果表明,MIL-101(Cr)-0.5具有较大的比表面积和孔容孔径。当MIL-101(Cr)-0.5用量为0.05 g、模拟燃料用量为10 mL、吸附温度为40 ℃、吸附时间为40 min时,吸附脱氮效果较好,吡啶模拟燃料的碱氮含量降至253.8 μg/g,脱氮率达85.35%,喹啉模拟燃料的碱氮含量降至343.86 μg/g,脱氮率达80.15%。利用Materials Studio软件模拟计算吡啶和喹啉分子在MIL-101(Cr)金属簇结构配体上的吸附能以及吡啶和喹啉分子中氮的碱性孤对电子与MIL-101(Cr)中不饱和金属位Cr3+的距离,结果表明,对吡啶吸附能的绝对值大于喹啉的,吡啶的碱性孤对电子与Cr3+的距离小于喹啉的,所以MIL-101(Cr)对吡啶吸附能力较强。

     

    Abstract: Diesel, being the most widely consumed fuel oil, has garnered increasing global attention for the production of clean diesel. The NOx produced upon the combustion of nitrogen compounds in diesel constitutes one of the primary sources of atmospheric pollutants, whereas adsorption denitrification technology enables the removal of nitrogen compounds from diesel under relatively mild conditions. Adsorption technology revolves around adsorbents, and metal-organic frameworks (MOFs), emerging as a novel porous adsorbent material, exhibit unparalleled superior adsorption and separation capabilities compared to conventional porous materials. Currently, there exist up to seventy thousand types of MOFs materials, among which MIL-101(Cr) stands out due to its excellent thermal and chemical stability, high specific surface area, large pore volume and pore size, and relatively superior adsorption performance among all easily prepared MOFs materials. Presently, the majority of MIL-101(Cr) syntheses utilize hydrofluoric acid as a mineralizer, a toxic and highly corrosive substance. Furthermore, it necessitates intricate activation processes for its removal during the later stages of synthesis, thereby impeding its industrial application and promotion. MIL-101(Cr), being a carboxylic acid-based MOFs, allows for particle size control through the use of monocarboxylic acids. The four metal organic framework materials (MOFs) (MIL-101(Cr)-0, MIL-101(Cr)-0.5, MIL-101(Cr)-1 and MIL-101(Cr)-1.5) with different amounts of acetic acid 0, 0.5, 1, and 1.5 mL as acid mineralizers replacing hydrofluoric were prepared by using the hydrothermal synthesis method. The MIL-101(Cr)-x samples, characteried by XRD, SEM, FT-IR, and N2 adsorption-desorption, were used for adsorption denitrification of pyridine or quinoline from model fuels with initial alkaline nitrogen content of 1732 μg/g. The effects of adsorption time and temperature on the adsorption denitrification performance were investigated. The experimental results indicate that MIL-101(Cr)-0.5 has a larger specific surface area and pore volume. When the adsorbent dosage is 0.05 g, the model fuel dosage is 10 mL, the adsorption temperature is 40 ℃, and the adsorption time is 40 minutes, MIL-101(Cr)-0.5 has the better adsorption denitrification effect. The alkaline nitrogen content in the model fuel containing pyridine is reduced to 253.8 μg/g and the denitrification rate 85.35%, 343.86 μg/g and 80.15% for quinoline. However, relying solely on experimental chemistry methods poses significant time and cost constraints on the development of MOFs materials. In contrast, computational chemistry offers not only efficient simulation of the adsorption and separation behaviors of existing MOFs, allowing for a deeper analysis of their mechanisms, but also the ability to predict the performance of MOFs that have yet to be synthesized. In light of this, this article employs Materials Studio software to simulate and calculate the adsorption energy of pyridine and quinoline molecules on MIL-101(Cr) metal cluster ligands, as well as the distance between the basic lone pair electrons of nitrogen in pyridine and quinoline molecules and the unsaturated metal site Cr3+ in MIL-101(Cr). The results showed that the absolute value of pyridine adsorption energy was significantly greater than that of quinoline, and the distance between the basic lone pair electrons of pyridine and the unsaturated metal site Cr3+ of MIL-101(Cr) was smaller than that of quinoline. Therefore, the adsorption ability of pyridine was stronger than quinoline.

     

/

返回文章
返回