变色硅胶吸附脱除模拟柴油中各种碱性氮化物

研究了变色硅胶吸附脱除氮含量为960.56μg/g模拟柴油中的碱性氮化物喹啉、苯胺和吡啶。比较了氧化铝、硅藻土、硅胶及变色硅胶对模拟柴油中喹啉的吸附脱除效果。采用XRD、低温N_2吸附-脱附和NH_3-TPD等方法对硅胶和变色硅胶进行了表征。考察了粒径、吸附温度、吸附时间、剂油质量比及共存芳香化合物(萘、苯或甲苯)对变色硅胶吸附脱除各种碱性氮化物的影响。变色硅胶吸附脱除碱性氮化物的顺序均为苯胺吡啶喹啉。吸附时间对三种氮化物的吸附脱除没有影响;吸附温度、变色硅胶粒径和共存芳香化合物对苯胺和吡啶的吸附脱除效果影响不大,对喹啉的吸附脱除效果影响较为明显;剂油质量比对三种氮化物的吸附脱除影响均较大,尤其是对喹啉影响最大。结果表明,变色硅胶吸附各种氮化物时Co能够与其中的N原子形成配位络合吸附。经焙烧再生,变色硅胶几乎完全恢复了对喹啉和吡啶的吸附脱除能力,并可多次再生,但变色硅胶再生后对苯胺的吸附能力损失较大。

Various basic nitrogen compounds removal from model diesel by adsorption with allochroic silica gel

The allochroic silica gel was used for adsorptive denitrification from model diesel containing known amounts of quinoline, aniline or pyridine with a total nitrogen concentration 960.56 μg/g. The adsorptive removal of quinoline in model diesel with alumina, diatomite, silica gel and allochroic silica gel was investigated. The experiment results indicate that the adsorptive denitrification performance of allochroic silica gel is more superior to that of other three adsorbents, implying that the CoCl₂ in allochroic silica gel can significantly improve the performance of denitrification. The silica gel and allochroic silica gel were characterized with X-ray diffraction (XRD), nitrogen adsorption and NH₃-TPD. The XRD results indicate that the two samples are of an amorphous structure. Silica gel and allochroic silica gel have the average pore diameter of 18.46 and 1.80 nm, the Brunauer-Emmett-Teller (BET) surface area of 437.86 and 623.39 m²/g, and the pore volume of 0.9724 and 0.3442 m³/g, respectively. The results of NH₃-TPD show that the acidity of allochroic silica gel is much stronger than that of silica gel which greatly enhances the adsorptive denitrification. Also, the influence of particle size, adsorption temperature, adsorption time, adsorbent to oil mass ratio and aromatic compounds on the adsorptive denitrification of allochroic silica gel was investigated. The adsorptive denitrification for different model diesels by allochroic silica gel is ordered as:aniline > pyridine > quinoline. Adsorption time has almost no influence on the removal of three nitrogen compounds. Adsorption temperature, particle size and aromatic compounds in the model diesel have little impact on the removal of aniline and pyridine, but have evident influences on the removal of quinoline. The adsorbent to oil ratio has a significant effect on the adsorptive denitrification, especially for quinoline. The experimental results suggest that the N-Co bond between Co in allochroic silica gel and N atom in the nitrogen compounds plays a significant role. Furthermore, the allochroic silica gel could be easily regenerated to recover its adsorptive denitrification for quinoline and pyridine by calcination once or several times, but except aniline.