Coke Resistant Perovskite-supported Ni Catalysts With High Efficiency For CH₄ Reforming For Hydrogen Production

Methane reforming gains tremendous research interests as it can consume the major greenhouse gases CH₄ and produce high efficient and clean secondary hydrogen energy sources,thus effectively relieving global warming.Ni-based catalysts are effective for methane reforming owing to their high initial activity,abundant resources and low cost.However,the severe carbon deposition and rapid deactivation of the Ni active sits limit its wide application.Thus,researching and developing catalysts with improved performance is becoming a hot topic.To develop and design catalysts with higher efficieny,it is necessary to study the reaction mechanism,the interaction between Ni active species with the supports,and means to control Ni particles size.First,steam reforming of methane for hydrogen production has been performed over Nickel supported on LaFeO₃ perovskites and treated by dielectric barrier discharge plasma?DBD?in H₂/Ar atmosphere.LaFeO₃ was synthesized with different methods including glycine-nitrate combustion method?GNC?,sol-gel method?SG?and co-precipitation method?CP?.It is found that catalysts prepared by glycine-nitrate combustion and sol-gel methods show better catalytic performance than the one prepared with co-precipitation method though it has the highest surface.Catalysts prepared with SG method has the lowest surface of support,it shows the best catalytic performance taking into account of both activity.With non-thermal plasma treatment before calcination,the stability of all catalysts has been improved.It is revealed that plasma treating can enhance the interaction between Ni and the LaFeO₃ supports,thus resulting in catalysts with improved Ni dispersion and higher thermal stability.SEM and TGA-DSC results testified that on the plasma treated catalysts,carbon deposition can be suppressed.These are believed to be the major reasons accounting for the improved catalytic performance of the catalysts by plasma treatment.Second,we have studied core-shell structiured catalysts LaNiO₃@SiO₂ for methane dry reforming.Cubic LaNiO₃ has been prepared by hydrothermal method.Taking CTAB and TEOS as surfactant and silica sources respectively,we have synthesized a series of core-shell structured catalysts with different core thickness for methane dry reforming.The results show that LaNiO₃@SiO₂ exhibited better catalytic performance and coke resistance than non-encapsulated LaNiO₃.Moreover,thickness of SiO₂ shell doesn't affect much on catalytic performane but prohibits carbon deposition comparing with the non-encapsulated LaNiO₃ catalysts.In summary,the protection of LaNiO₃ by the SiO₂ shell can effectively proect the Ni particles from sintering and make carbon lack of physical growth space,thus resulting in catalysts with enhanced coke resistance and catalytic performance.