Study On The Adsorption Performance Of Activated Alumina For Removal Of Basic Nitride Compounds

Nitrogen compounds in diesel are harmful to its processing,storage,transportation and useing.Nitrogen compounds will promote the reaction of other non-hydrocarbon compounds in diesel,forming colloidal precipitation,and then affect the color and stability of diesel.The main purpose of this paper is to study the adsorption performance of activated alumina for aniline or pyridine in simulated fuels the adsorption and time of activated alumina,adsorption temperature,adsorption dosage and usage amount on the effects of its comprehensive denitrification were investigated.It can be seen from the experimental results that the amount of adsorbent has a greater influence on the adsorption of aniline or pyridine,and the optimal amount of adsorbent is about 1.6 g(15 m L simulated fuel).The adsorption time has little effect on the adsorption of aniline and pyridine,and the best adsorption time is 40 min.The adsorption effect is better at low temperature,indicating that the adsorption of aniline and pyridine are mainly physically adsorbed.Activated alumina has better adsorption performance for aniline,which is mainly due to the fact that the N atom of pyridine is on the ring,but the N atom of aniline is outside the ring So its steric hindrance is small.It is easier for aniline to have intermolecular interaction with the active sites of activated alumina.The molecular polarity,the distance between the adsorbed molecules and the charge transfer amount during the adsorption process were calculated through molecular simulation.The polarity of aniline is 6.3 greater than that of pyridine 5.3.The intermolecular distance of activated alumina and adsorbing aniline is1.527 lower than that of pyridine 2.245 and the N atom charge transfer amount of activated alumina adsorbing aniline is 0.577 which is greater than the charge transfer amount of pyridine N atom adsorbing 0.196.Therefore,the effect of activated alumina adsorbing aniline is greater than that of pyridine.The calculated results are completely consistent with the experimental results.It is concluded from the simulation calculation results that in the prediction of the crystal habit of activated alumina,the spacing of activated alumina at(1 1 1)is 4.55,and the proportion of total crystal planes is the largest 100%.The adhesion energy of(1 1 1)surface-5865.502 is also the largest.The stronger the adhesion,the easier it is for the adsorbate to adhere to the surface(1 1 1)for adsorption.From the layout analysis.It can be concluded that the relative nucleophilicity f~-of the N atom on pyridine is 0.19 which is significantly higher than the relative nucleophilicity of the N atom on aniline of 0.095.The relative nucleophilicity f~-reflects Lewies base its strength.Therefore,the Lewis base strength of pyridine is greater than that of aniline.According to the calculation results of HOMO and LUMO,the energy band gap of aniline is 0.1475,the energy band gap of pyridine is 0.1512.Since the band gap of aniline is smaller than that of pyridine,aniline is more active than pyridine.The calculation shows that the adsorption energy of pyridine and aniline is-7.2×10~5 k J/mol and-1.14×10~6 k J/mol,the adsorption energy of activated alumina for aniline is-291.37 k J/mol,the adsorption energy of activated alumina for pyridine is-169.56 k J/mol.The adsorption capacity of activated alumina for aniline adsorption is greater,and the distance between the adsorbed molecules is also smaller.Therefore,the adsorption structure of activated alumina for aniline adsorption is more stable and the adsorption effect for anilineis better.It is consistent with the conclusion of the experimental part in the paper,so the simulation calculation result is consistent with the experiment.