Preparation Of Low Dimensional Supports And Their Application In Hydrodenitrogenation Of Coal Tar

The data issued by the National Bureau of Statistics indicated that the coal tar output of china in 2020 reaches about 20 million tons.By hydrogenation treatment,coal tar can be converted into high quality fuel.However,with the increasing environmental requirements,it is more and more difficult to meet the standard of the latest National Standard（VI）efficiently over the traditional NiMoS/Al₂O₃ catalysts.In addition,coal tar contains more nitrogen-containing compounds than the crude petroleum and is rich in aromatic compounds.This signifies that the hydrogenation process of coal tar is remarkably different from that of petroleum.Therefore,it is of great significance to design and develop the high efficiency catalysts for coal tar hydrogenation.In this study,quinoline,a representative nitrogen-containing compound in middle-low temperature coal tar,was chosen as a model compound to study the hydrodenitrogenation（HDN）activity of new NiMoS-based catalysts.Considering the strong interaction of active phases with Al₂O₃,and the resultant negative impact on the hydrogenation activity of NiMoS/Al₂O₃,the following experiments have been primarily performed:（1）Six kinds of supports（TiO₂-Al₂O₃）with different dimensions were prepared using TiO₂ as a modifier,and their properties are compared.NiMoS active phases were loaded on these six different supports via co-impregnation method followed by sulfidation.The influence of the dimension of supports on the formation and catalytic performance of NiMoS active phases was investigated by comparing the HDN of quinoline.（2）The hydrogenation performance of NiMoS catalysts was investigated using phenanthrene as a model compound.The effect of phenanthrene on the HDN of quinoline over NiMoS/TiO₂-Al₂O₃ catalysts was investigated.The results are concluded as follows:1,SEM and TEM characterization results show that one-dimensional TiO₂-Al₂O₃ support with tubular structure and two-dimensional TiO₂-Al₂O₃ support with lamellar structure are synthesized by the deposition of precursor salts of TiO₂ and Al₂O₃ on carbon nanotubes（CNTs）and graphene oxide（GO）,respectively,followed by the removal of CNTs and GO templates by calcination in air.The incorporation of Ti has a certain effect on the existence of Ti and Al in TiO₂-Al₂O₃.When sol-gel method is used,Ti has a strong interaction with Al,and TiO₂ can enter into the crystal lattice of Al₂O₃ to form the amorphous Ti AlO_x.2,The specific surface area of catalyst was increased and the dispersion of active phase was improved by using two-dimensional TiO₂-Al₂O₃ as the support.The results show that NiMoS/TA-2Ds（TA-2Ds:TiO₂-Al₂O₃ prepared by impregnation method）catalysts displays a better performance in the HDN of quinoline at 350℃ and 3 MPa（H₂）.After 4 hours,74.8%of nitrogen is removed with the product selectivity of 58.4%（propylcyclohexane）and 13.4%（propylbenzene）.3,Phenanthrene can be hydrogenated to perhydrophenanthrene over NiMoS/TA-2Db（TA-2Db:TiO₂-Al₂O₃ prepared by sol-gel method）catalysts at 280℃ and 4 MPa（H₂）.Relatively,NiMoS/TA-2Ds catalysts shows best hydrogenation and HDN performance.The competitive adsorption between phenanthrene and quinoline intermediates befalls at 350℃,which inhibits the further hydrogenation of tetrahydroquinoline,however there is no competitive adsorption between phenanthrene and quinoline.The inhibition of phenanthrene on the HDN of quinoline decreases with the decrease of reaction temperature.