Study On CH₄/CO₂ Reforming Performance Of Highly Dispersed Nickel-based Catalyst Prepared By Phase Formation/phase Transformation Induction Method And Derived Ga_0.3Ni_0.7 Catalyst

The dry reforming of methane reaction is one of the effective ways to convert and utilize greenhouse gases reasonably and alleviate global warming.Non-noble metal nickel-based catalysts have been widely used in the study of dry reforming of methane,because of their low cost and easy availability.However,the deactivation of the catalysts still cannot meet the needs of industrialization.The main reasons for deactivation are carbon deposition and sintering.So for this problem,in this thesis,a series of new catalyst preparation methods were designed,and the structure-activity relationship of the catalyst was deeply explored.The specific research contents are as follows:（1）Highly dispersed and strongly anchored nickel-based catalyst(Ni/Ce_0.3Zr_0.7O₂-TB)was prepared by the method of support phase formation induction.The catalytic performance of the catalyst for dry reforming of methane at 750℃was investigated.The results show that by controlling the two-phase formation of the support and the loading of the active component precursor at the same time,the highly dispersed and anchored active component nickel particles were successfully achieved under the induction of the phase formation of cerium zirconium solid solution support.At 750℃,compared with the Ni/Ce_0.3Zr_0.7O₂-B catalyst prepared by the traditional impregnation method,the Ni/Ce_0.3Zr_0.7O₂-TB catalyst prepared by the support phase formation induction method had higher activity and stability.After 60 hours of reaction,the conversion of CH₄ and CO₂ of Ni/Ce_0.3Zr_0.7O₂-TB catalyst only slightly decreased,76%and 83%respectively.The CH₄ conversion rate of Ni/Ce_0.3Zr_0.7O₂-B catalyst decreased significantly,from 82%to 53%,and the CO₂ conversion rate decreased from 86%to67%.（2）The highly dispersed and strongly anchored nickel-based catalysts（Ni/Ga₂O₃-TB）were prepared by the phase transformation of support induction method.The catalytic performance of the catalyst for dry reforming of methane at 750℃was investigated.The results show that by controlling the structural rearrangement caused by the phase transformation of the support and the reduction of the active component nickel simultaneously,the small particle size and highly dispersed active component nickel particles were successfully obtained under the phase transformation of gallium oxide support induction.But at 750℃,Ni/Ga₂O₃-TB catalyst prepared by the phase transformation of support induction had no significant advantages in activity and stability.The presence of surface films was found in the TEM diagram of the catalysts prepared by the two methods before the reaction,and the formation of a new phase Ga_0.3Ni_0.7was observed in the XRD diagram of the catalyst after the reaction.The film formed on the surface of the catalyst prepared by the two methods before the reaction was further studied.Ni/Ga₂O₃-B（In-situ）catalyst without thin film was prepared by in situ reduction method.The results show that there was almost no difference in activity and stability of the two catalysts after 50 hours of reaction,and the existence of thin films is not the main factor affecting the activity and stability of Ni/Ga₂O₃-B catalyst and Ni/Ga₂O₃-TB catalyst.However,the film-free catalyst had better carbon deposition resistance due to the improvement of surface alkalinity.（3）A preliminary study on the performance of dry reforming of methane reaction in Ga_0.3Ni_0.7 new phase of dry reforming of methane reaction.The Ga_0.3Ni_0.7 was used as the active component to prepare the Ga_0.3Ni_0.7/SiO₂catalyst.The dry reforming of methane activity of the catalyst at 800℃and 750℃was investigated.As a result,Ga_0.3Ni_0.7 new phase had excellent activity and stability of dry reforming of methane.At 750℃,the CH₄ conversion rate could still reach 86%and the CO₂ conversion rate was 92%,whether the reaction temperature was 800℃or 750℃,the catalyst had no deactivation in 100 hours.Compared with the existing catalysts,Ga_0.3Ni_0.7/SiO₂catalyst has a good development prospect.