Research On CO₂ Methanation Over Ni-Mg-Al Hydrotalcite-like Catalyst

Carbon dioxide was considered to be one of the most main greenhouse gases?GHS?,accounting for 60%of GHS.With the increasing of CO₂ in the atmosphere and global warming,climate change has become the biggest environment problem in the world.However,CO₂ as a significant carbon resource,which can be converted into high value-added chemicals by CO₂ hydrogenation.It can not only alleviate greenhouse effect caused by CO₂ emissions,but also obtain useful chemicals.At present,it is considered to be one of the most effective ways to recycle CO₂.However,the problem of methanation reaction is poor activity at low temperature.In this paper,we prepared a mixed metal oxides with hydrotalcite as precursor by doping additives Fe and realized the excellent catalytic performance of methanation of CO₂.The specific work are as follows:Hydrotalcite precursors were synthesized by co-preparation method followed by calcining at 450°C,550°C and 650°C respectively to get the mixed metal oxides.The influence of different calcination temperature on the catalytic performance was investigated.BET,XRD and H₂-TPR were employed to analyze the structure,surface species and reducibility of catalyst.The result indicated that NiO particles tended to accumulate and sinter at high calcined temperature,while the mixed metal oxides cannot be obtained at low calcined temperature.The catalyst calcined at 550°C exhibited large specific surface area,high dispersion and the strong interaction between active metal Ni and oxide support.And its resistance to sinter and coke are enhanced owing to the uniformly dispersed active metal Ni on the surface of support.The addition of Fe into the mixed metal oxides were obtained by co-preparation method via using hydrotalcite as precursors and revealed outstanding performance at low temperature.The existence of NiFe₂O₄ was confirmed by Raman characterization,which proved that Fe species were successfully incorporated into hydrotalcite.H₂-TPR also revealed that the main reduction temperature decreased from 741°C to528°C,indicating the addition of Fe improved the reduction ability of the catalyst.CO₂-TPD analysis displayed that the distribution and quantity of basic sites were changed after adding Fe species.Apart from these,the in situ DRIFTS demonstrated that the incorporation of Fe enhanced CO₂ adsorption and activation as well as promoted the decomposition of formate species,giving rise to high catalytic performance for CO₂ methanation.