Study On The Synthesis Of Mesoporous Molecular Sieves And The Process Conditions For Adsorption Denitrification From Diesel Fuel

Nitrogenous compounds in the diesel fuel were harmful to the processing,storage,transportation and using.In the process of combustion,carbon deposition was produced and the toxic nitrogen oxide gas was released,which can form photochemical smog and acid rain to pollute the environment.At present,denitrification processes mainly include hydrogenation denitrification process and non-hydrogenation denitrification process.The adsorption denitrification process in the non-hydrogenation denitrification process has attracted much attention due to its lower investment and simpler operation compared with the hydrogenation denitrification process.Mesoporous molecular sieve MCM-41 is often used as an adsorbent due to its large specific surface area,narrow pore size distribution and ordered pore arrangement.However,the mesoporous molecular sieve MCM-41 is weak in activity,so it needs to be modified.In addition,the mechanism of adsorption and removal of nitrogenous compounds are not studied deeply enough.Therefore,the synthesis of several mesoporous molecular sieves and their adsorption denitrification performance from diesel oil were studied in this paper.The mechanism of adsorption using the experimental method and molecular simulation method was explored.In this thesis,the mesoporous molecular sieves MCM-41,Zn-MCM-41,Ba-MCM-41and Ce-MCM-41 were successfully synthesized and characterized by X-ray diffraction?XRD?,FT-infrared spectroscopy?FT-IR?and low-temperature N₂ adsorption-desorption;their performance in the adsorption denitrification of quinoline from model diesel oil was investigated.The results indicate that all the synthesized samples take typical mesoporous structure and heteroatoms have been successfully incorporated into the molecular sieves framework.An 8T cluster model for the molecular sieves were bulit by usting the Materials Studio software;the simulated XRD spectrum is basically consistent with the experimental spectrum,which proved the accuracy of cluster model.The adsorption of quinoline on the mesoporous molecular sieves were then simulated and the adsorption energy and the distance between the adsorbed molecule and the adsorption center(d_?N-M?)were calculated.The results suggest that the adsorption denitrification performance of various molecular sieves follows the order of Zn-MCM-41>Ce-MCM-41>Ba-MCM-41>MCM-41;that is,Zn-MCM-41exhibits the best adsorption denitrification performance,with the highest adsorption energy and shortest d_?N-M?;the optimal Me/Si O₂ molar ratio of the mesoporous molecular sieves Zn-MCM-41,Ba-MCM-41 and Ce-MCM-41 was 0.01,0.01 and 0.02,respectively.Moreover,the adsorption time has a significant influence on the denitrification efficiency,whereas the effect of adsorption temperature is relatively minor;the optimal adsorption times for Zn-MCM-41,Ba-MCM-41 and Ce-MCM-41 are 40 min,10 min and 30 min,respectively,whereas the optimal adsorption temperatures for three molecular sieves are 40?,30?and40?.The adsorption forces of quinoline on mesoporous molecular sieves were mainly physical adsorption and chemisorption,the chemisorption mainly included the?-complexation between heteroatoms?M?in the mesoporous molecular sieves and the benzene ring in the quinoline molecule and the N-M action.