Construction Ni-Zr-Al Catalytic System For CO Methanation By Phase Transfer Method

Syngas methanation is one of the core processes of coal-to-natural gas,and methanation catalysts have become a key issue restricting its development.At present,nickel-based catalysts are mainly used in methanation catalysts,but they still have the problems of carbon deposition and sintering to deactivate the catalyst.Therefore,it has important research and application value that the development of nickel-based catalysts with excellent performance.Therefore,in this paper,aiming at the problems of easy carbon deposition and easy sintering of nickel-based catalysts,a NiO/Al-Zr catalyst prepared by the citric acid complexation method was constructed by changing the roasting method.The phase transition of the Ni-Al-Zr ternary system during the calcination process is used to form Ni-based catalysts with different functional structures for CO methanation reactions.Through XRD,H₂-TPR,XPS,Raman,N₂ adsorption and desorption and other characterization methods,it studies the effect of different calcination temperatures on the three elements of Ni-Zr-Al,the surface structure of Ni on the microscopic level,the interface effect of Ni and the support,and the correlation of phase change transfer on the catalytic activity and stability,so as to realize effective regulation the catalytic performance of the catalysts.For the NiO/Al-Zr catalysts at different calcination temperatures,the microenvironment of the three elements Ni-Al-Zr was changed,which lead to the catalyst showing different Ni-Zr,Ni-Al and Al-Zr action forms.In the Ni₃ Zr alloy phase,Zr transfers the charge to Ni,Zr has a strong interaction with O,and increases the reducibility in a hydrogen-rich atmosphere.The synergistic effect of the above three will significantly reduce the C-O polarity,promote C-O fracture and increase the type of active site.Different forms of action are easy to make the existence of NiO and Al-Zr support interface different,producing α-NiO,β-NiO,γ-NiO reduction of many different types of NiO,among which the increase of β-NiO is conducive to more stable NiO reduction and overflow of lattice oxygen produce oxygen vacancies,which can not only effectively inhibit the sintering of nickel-based catalysts during the reaction,but also strengthen the catalyst’s ability to store and release oxygen and move oxygen,thereby improving the dissociation ability of CO and promoting the medium and high temperature of the catalyst active.The calcination temperature of the Al-Zr composite support affects the difference in the crystal phase structure of the support,and it is easy to form a multi-phase support under the firing at 400°C.It is easy to form a single-phase carrier under calcination at 600°C.The existence of heterogeneous and single-phase supports significantly affects the specific surface area and pore size of the catalyst.The Al-Zr400 support that exists in a heterogeneous and disordered state is more likely to make the catalyst have a larger specific surface area,and it is easy to form a smaller pore size when calcined at 700°C.The single-phase Al-Zr600 support is easier to transform some small pores in the catalyst to the direction of large pores when calcined at 700℃,forming a composite pore structure.Multi-phase disordered and single-phase ordered Al-Zr carrier.After loading the active component Ni,it is calcined at 700℃.Ni-Al-Zr ternary system has different preferential effects.Multi-phase disordered Al-Zr400 carrier,Preferentially carry out the Al-Zr interaction,from the disordered Al-Zr multi-phase to the ordered Al_0.48Zr_0.52O_1.74 single crystal phase,the single-phase ordered Al-Zr600 carrier has formed a stable Al-Zr After the action,a Ni-Al interaction is formed.The NiO/Al-Zr6-7 catalyst has a regular Al-Zr carrier composite pore structure,Ni-Zr alloy promotes the increase of active sites,and the additive effect of Zr facilitates the reduction of Ni.The above three synergistic effects make the catalyst show the best performance Catalytic activity and sintering resistance,the CO conversion rate reaches99.7% at 450℃,and the CH₄ selectivity reaches 80.5%.