Study On The Performance Of Gd/Ru Promoted Ni/Al₂O₃-CeO₂ Catalyst For Dry Reforming Of Methane

For the purpose of improving the structure energy and environment,dry reforming of methane technology has attracted much more attention.Ni-based catalyst was the most profitable choice for the reaction characterized by its extensive availability and low cost.However,the catalysts suffered from the major drawback of deactivation,enhancing the reduction and anti-coking ability of Ni-based catalyst has been a hot research.The thermodynamics of the reaction system was firstly explored.Based on Ni/Al₂O₃-CeO₂,we synthesized the new Ni/Al₂O₃-CeO₂-x%Gd₂O₃?x=0,0.8,1,1.2,1.4,2?catalyst,and investigated the effect of Gd doping amount,calcination&reaction temperature and Ni/Al₂O₃-CeO₂-1.2%Gd₂O₃ calcination temperature on the performance of catalysts.Then we introduced the other Ni-x%Ru/Al₂O₃-CeO₂?x=0,0.1,0.3,0.5,1?catalyst,and investigated the effects of Ru doping method,amount,reaction space velocity and reaction temperature on the catalytic activity.At the same time,the catalysts were measured by X-ray photoelectron spectroscopy?XPS?,N₂ adsorption-desorption,Thermo gravimetric?TG?,etc.The main conclusions were as follows:?1?A series of mesoporous structures of Ni/Al₂O₃-CeO₂-x%Gd₂O₃?x=0,0.8,1,1.2,1.4,2?were prepared by sol-gel method.We investigated the effect of Gd doping amount,and found that Ni/Al₂O₃-CeO₂ exhibited good catalytic activity with adding Gd,and Ni/Al₂O₃-CeO₂-1.2%Gd₂O₃ catalyst presented the highest CH₄&CO₂ conversions?86%&93%?,and the catalytic activity of the catalyst barely decreased after the long-term activity test with 15 hours.The N₂ adsorption-desorption detection showed that the synthesized catalysts were all mesoporous.The XRD and H₂-TPR analysis indicated that the Gd doping amount had an important effect on the crystal structure of the catalyst.Adding proper amount of Gd could inhibit the formation of NiAl₂O₄ phase,promote the reduction of Ni and thereby increase the catalytic activity.It was found that Gd reduced the Ni crystal size according to the results of with XRD and TEM.The SEM and TG analysis showed that adding Gd reduced the carbon deposition of the catalyst.Moreover,Ni/Al₂O₃-CeO₂-1.2%Gd₂O₃ showed the least carbon deposition amount among all catalysts,indicated that Gd promoted the catalytic activity and carbon deposition resistance of Ni/Al₂O₃-CeO₂.?2?The effect of changing the calcination&reaction temperature on Ni/Al₂O₃-CeO₂-x%Gd₂O₃,and the calcination temperature on Ni/Al₂O₃-CeO₂-1.2%Gd₂O₃ were also investigated.It was revealed that calcined temperature had great impact on the catalytic performance and lattice structure.The XRD and BET results showed that the interaction between the active component and the support increased,the crystal transformation or catalyst sintering caused with the increase of the calcination temperature.And it was concluded that 800?was the optimum calcination and reaction temperature of the catalyst.?3?The effect of Ru introduction method on the catalytic activity of Ni-0.3%Ru/Al₂O₃-CeO₂ was investigated,it was found that Ni-0.3%Ru/Al₂O₃-CeO₂ prepared by one-pot method of sol gel showed the excellent catalytic performance.Then,the effect of Ru loading amount was discussed,the activity of catalyst was improved after adding Ru,and Ni-0.3%Ru/Al₂O₃-CeO₂ catalyst obtained the highest CH₄&CO₂ conversions?90%&96%?.However,when the loading amount of Ru was more than 0.3%,Ni-x%Ru/Al₂O₃-CeO₂ exhibited a similar catalytic performance.The results of BET,XRD and TG showed that the grain size of Ni,the specific surface area and the pore structure were all improved after the introduction of Ru,and the carbon formation rate was reduced,relying on the synergistic effect between Ni and Ru.Eventually,the catalytic performance of Ni/Al₂O₃-CeO₂ was improved.