Preparation And Adsorptive Desulfurization Performance Of Silica-based Aerogel Composites Doped Cu, Pd

The sulfur compounds in the fuel oil are burned to form sulfur oxides.which has a great impact to environment and are poisonous to the reforming and shift catalysts in the fuel processor and the electrode catalysts in fuel cell stacks.The traditional hydrodesulfurization technology?HDS?has strict operating conditions,and it is difficult to remove macromolecular thiophene sulfides,which cannot achieve the purpose of deep desulfurization and it is difficult to meet the needs of fuel cells.Adsorption desulfurization technology is a kind of desulfurization technology with low energy consumption,low cost,easy regeneration,environmental protection and good desulfurization performance for thiophene and its derivatives,and is very suitable for the application in fuel cells.Therefore,it has received extensive attention from researchers.The adsorbent is critical for the adsorption desulfurization technology.The mesoporous adsorbents based?-complexation with abundant active centers highly dispersed,and low preparation cost are the most promising desulfurization adsorbents.Aerogel is a kind of solid materials with three-dimensional porous network through the formation of the mutual aggregate of nanoscale particles,which has low preparation cost and is easy to be large-scale producted.In the previous work,our research group studied a series of aerogel composite desulfurization adsorbents based on?-complexation containing Ni???,Ag???and Cu???.It exhibited an excellent adsorption performance for thiophene and benzothiophene in model gasoline,however,in the preparetion process of these adsorbents active components clearly lost,and the adsorption selectivity for thiophene and its derivatives need to be improved furture at the presence of aromatic and olefins.In this thesis,Cu₂O-SiO₂,Cu₂O-Al₂O₃-SiO₂,Cu₂O-TiO₂-SiO₂ aerogel composites,Cu₂O-SiO₂@GO aerogel composites with different graphene oxide?GO?content and Pd???-SiO₂ aerogel composites with different n?Si/Pd?were prepared by a sol-gel method followed by drying under atmospheric pressure,respectively.The adsorptive desulfurization performance of the materials was evaluated by equilibrium and breakthrough adsorption experiments,respectively.At the same time,the structure and composition of the materials were characterized by low temperature N₂ adsorption desorption,FTIR,XRF and SEM.The effects of different active components on the structure and desulfurization performance of the materials were investigated.The results showed that Cu₂O-SiO₂,Cu₂O-Al₂O₃-SiO₂ and Cu₂O-TiO₂-SiO₂aerogel composites were three-dimensional network-like mesoporous solid materials formed by the aggregation of nano-sized particles.They have high porosity,high specific surface area,and Cu₂O-Al₂O₃-SiO₂ and Cu₂O-TiO₂-SiO₂ has more acid centers and stronger acidity.The adsorption capacity of thiophene on Cu₂O-SiO₂,Cu₂O-Al₂O₃-SiO₂ and Cu₂O-TiO₂-SiO₂ aerogel composite adsorbents decreased following the order of Cu₂O-Al₂O₃-SiO₂>Cu₂O-TiO₂-SiO₂>Cu₂O-SiO₂,which have a larger breakthrough adsorption capacity for benzothiophene and dibenzothiophene than thiophene.The addition of Al and Ti to Cu₂O-SiO₂ reduces the influence of competitive adsorption of aromatic/olefin on desulfurization performance?increased the desulfurization selectivity of the adsorbent?.The adsorbent also has excellent regeneration performance,breakthrough adsorption capacity of thiophene after regeneration was 57.1%,78.6%and 66.7%of the fresh adsorbent.In order to improve the Cu???incorporation and mechanical strength of Cu₂O-SiO₂aerogel composite,Cu₂O-SiO₂@GO aerogel composite was further synthesized.After incorporation of graphene oxide,the characteristic morphology of the Cu₂O-SiO₂aerogel composite does not change.It still has high porosity,high specific surface area?608-820 m²/g?and mesoporous?5.0-8.4 nm?structure.When the GO incorporation amount is 2.00 wt‰,the adsorbent?Cu₂O-SiO₂@2.00 wt‰GO?exhibited the largest breakthrough adsorption capacity for thiophene from model gasoline.The equilibrium adsorption data of thiophene from model fuel over all Cu₂O-SiO₂@GO adsorbents can be well fitted by Langmuir and Freundlich models,and the adsorption process of thiophene from fuel over Cu₂O-SiO₂@2.00 wt‰GO is an endothermic process with reduced chaotic and spontaneous.The selectivity of the Cu₂O-SiO₂ adsorbent can be increased by incorporating GO.Cu₂O-SiO₂@2.00 wt‰GO adsorbent has good regeneration performance and can be reused many times.Cu???is easily disproportionated in air to form Cu and Cu???,so Pd???-SiO₂composite aerogel adsorbent was prepared.The loss rate of the active component is increasing with the decrease of n?Si/Pd??the increase of the amount of Pd added?,and is as high as?67.0-69.3%?.When n?Si/Pd?is 318,the adsorbent exhibited the largest breakthrough adsorption capacity of thiophene from model fuel,and The equilibrium adsorption data of thiophene from model fuel over all Pd???-SiO₂ adsorbents can be well fitted by Langmuir and Freundlich models,.The R² values of the Freundlich adsorption isotherms were almost slightly higher than that of the Langmuir adsorption isotherms,indicated that the Freundlich model is more suitable for describing the process of Pd???-SiO₂ adsorption of thiophene.The adsorption process of thiophene from model fuel over Pd???-SiO₂-318 is still an endothermic process with reduced chaotic and spontaneous.After four regenerations,the breakthrough adsorption capacity of thiophene over Pd???-SiO₂-318 was 86%of the fresh adsorbent.