Synthesis Of Micro/mesoporous Materials And Their Catalytic Performances For Hydro-upgrading

With the rapid increase in vehicle ownership and gasoline demand,the environmental pollution caused by automobile exhaust is becoming more and more serious.In order to reduce the pollution caused by fuel combustion,strict standards for automotive gasoline have formulated around the world.On January 1,2023,China will implement the national VI standard?Stage B?,and further reduce the olefin content in gasoline while ensuring that the sulfur content is not more than 10?g/g and the octane number is also meet the standard.These posed a serious challenge,especially on the gasoline hydroupgrading process.In this thesis,the reaction performance of three-dimensional ordered mesoporous structure KIT-5 material in dibenzothiophene?DBT?hydrodesulfurization reaction was studied.Aiming at the problems of high olefin content in FCC gasoline,high olefin saturation and large loss of octane number after hydroupgrading,a novel hierarchical porous catalyst with dual functions of hydrodesulfurization and isomerization was designed and synthesized.Ordered micro/mesoporous composites materials were prepared by in situ self-assembly of mesoporous materials with different topological structures using microporous molecular sieves with better isomerization properties to be the precursors.Optimization of the synthesis processes is significant to achieve the controlled synthesis of microporous molecular sieves with different acidities,different topologies and different pore sizes.The corresponding hydroupgrading or hydroisomerization catalyst is prepared by using the micro/mesoporous composite as a support additive.The materials and catalysts were characterized by XRD,N₂ physical adsorption,TEM,SEM,Py-FTIR,XPS and Raman.Finally,the hydro-upgrading and hydroisomerization properties of the catalyst was evaluated using FCC gasoline and n-octane as raw feedstocks,respectively.The main contents and the research results are as follows:?1?A series of highly ordered aluminosilicates?Al KIT-5?with different Si/Al molar ratios combining with high framework alumina content,which possessed three-dimensional cubic Fm3m mesoporous structure,were synthesized by using the post-treatment method.TEM results showed that the material still maintained a highly regular order after the introduction of Al.The ²⁷Al NMR results confirmed that about84%the aluminum species had been introduced into the siliceous framework of KIT-5.The Ni Mo supported catalyst were prepared using KIT-5,Al-MCM-41,AK-x and the mechanical mixture material as the support.It should be noted that the Ni Mo/KIT-5 and Ni Mo/AK-x catalysts exhibited superior HDS activities relative to those of the Ni Mo/Al-MCM-41 catalyst at each WHSV value.The highest HDS efficiency?99.2%?of DBT was achieved at WHSV=10 h^-1 over the Ni Mo/AK-10 catalyst,of which the4.76 h^-1,respectively.?2?The zeolite W precursor was prepared using the low-cost silica aluminum microsphere without using any additional template surfactant.The micro/mesoporous composite W-MCM-41 was prepared by adding W zeolite precursors into CTAB solution and optimizing the synthesis conditions parameters involving crystallization time of precursors,the molar ratio of CTAB/Si O₂ and H₂O/Si O₂.TEM results displayed that W-MCM-41 composites had orderly mesoporous structure.Co Mo supported hydroupgrading catalysts were prepared by using W zeolite,Al-MCM-41,W-MCM-41and the mechanical mixtures as the carrier additives.The series of catalysts were evaluated for hydrogenation performance by using FCC gasoline as feedstock.The Co Mo/WMA catalyst exhibited the best hydroisomerization performance,higher aromatization performance and HDS activity,which compensated for the octane loss.The desulfurization efficiency was 93.4%,and the octane loss was 1.3 units.?3?ZSM-22 zeolite with excellent isomerization properties were introduced into PHTS?Plugged hexagonal template silicas?mesoporous materials to prepare micro/mesoporous composites with different Si/Al ratios of ZSM-22/PHTS?ZP?.The composite ZP had both the structural characteristics of the ZSM-22 zeolite and the PHTS material.The Co Mo supported hydro-upgrading catalysts were prepared by using ZSM-22,PHTS and the composite material with different Si/Al ratios to be the carrier additives for evaluating the hydroupgrading performance of FCC gasoline.Co Mo/ZPA120 catalysts exhibited large specific surface area,maximum pore volume and weak metal-support interaction.The Co Mo/ZPA120 catalyst achieved the highest hydrodesulfurization?95.2%?and hydroisomerization performance,and had good octane number retention capacity?-1.1 unit?.?4?Pt supported catalysts were prepared by using ZSM-22/PHTS composites with different Si/Al ratios as supports.The hydroisomerization performance of the series of catalysts was evaluated using n-octane as model compound in a fixed-bed microreactor.The evaluation results showed that the conversion of n-octane on Pt/ZP100 catalyst reached 86.3%at 300?.The product analysis demonstrated that the selectivity of Pt/ZP100 catalyst and the selectivity of double-branched isomers were significantly higher than that of Pt/ZSM-22 catalyst.