Preparation Of Ni Based Catalysts For CO₂Reforming Of CH₄Derived From Hydrotalcite

The conversion of natural gas into high value-added chemicals has aroused the increasing interests. Especially, CO2reforming of CH4(CRM), can directly convert two important greenhouse gases (CH4and CO2) to valuable feedstock with a suitable ratio of H2/CO for Fischer-Tropsch process. Nickel-based catalysts are widely used in the methane reforming reaction, but the easy deactivation caused by coke deposits or sintering of nickel particles limit their industrial utility. Therefore, it is the key to develop an appropriate catalyst with excellent activity, high stability and better resistance to coke and metal sintering for industrial standpoint.Ni-based catalysts prepared from MgAl layered double hydroxides (LDHs) have been widely studied in CO2reforming of CH4because of its high specific surface, high dispersion and strong basicity. In this paper, the MgO-Al2O3mixed oxides calcined from commercial Mg-Al hydrotalcite was used as the support to prepare Ni based catalyst for CH4reforming of CO2by a microwave-assisted method. The effects of the concentration of Ni(NO3)2solution and treatment temperature were investigated. The results of XRD indicated that the hydrotalcite structure can be recovered after impregnation. H2-TPR results indicated that there was a strong interaction between the support and NiO particle. The obtained catalyst displayed better anti-coking and anti-sintering ability when used in CH4reforming of CO2compared with the conventional co-precipitation Ni/MgO-A;2O3catalyst despite relatively lower activity. The high dispersity of Ni particle on the support surface may contribute to the good stability of the resultant catalyst.The Ni-Mg-Al ternary hydrotalcite was successfully and rapidly synthesized by rapid precipitation combined with microwave-assisted hydrothermal crystallization. The microwave radiation greatly improved the crystallinity of the obtained hydrotalcite. In rapid precipitation process, the nuclei formation and crystal growth took place simultaneously. Ni/MgO-Al2O3nano-composite catalyst was prepared by controlling the microwave power and synthesis temperature. XRD results indicated that the obtained Ni catalyst had high dispersibility. The catalyst exhibited good activity and stability when used in CO2reforming CH4.Based the above work, a new method namely two-steps method was proposed here to prepare the Ni/MgO-Al2O3catalysts derived from LDHs. MgAl LDHs were firstly synthesized by rapid precipitation combined with microwave-assisted hydrothermal crystallization, and then the nickel nitrate solution for incorporating Ni2+into the framework of LDHs was mixed with obtained MgAl LDHs sol under stirring. The. N2adsorption/desorption results indicated that the resultant Ni/MgO-Al2O3catalysts prepared by two-steps method show larger pore volume and pore size compared with the samples by the conventional coprecipitation catalyst. The derived Ni catalysts exhibit higher catalytic activities and better stability at800℃during6h. The characterization of the used catalysts by XRD and TPO indicate that the catalysts prepared by the two-steps show higher resistance to coke formation and sintering.