Ni/MgO[sbnd]Al2O3 catalyst derived from modified [Ni,Mg,Al]-LDH with NaOH for CO2 reforming of methane

Abstract

[Ni,Mg,Al]-layered double hydroxide (LDH) was modified with NaOH solution to prepare the LDH-derived Ni/MgOAl2O3 catalyst and characterized by X-ray diffraction, inductively coupled plasma optical emission spectrometer, scanning electron microscope, transmission electron microscopy, temperature programmed desorption of CO2 or NH3, N2 adsorption, and thermogravimetry analysis, respectively. The resultant Ni/MgOAl2O3 catalysts were used for CO2 reforming of CH4. The results showed that the concentration of NaOH solution has an obvious effect on the structure of LDH and catalytic performances of the resultant nickel-based catalysts. Aluminum species in LDH was partly dissolved with increasing NaOH solution concentration, resulting in the increase of [M2+/M3+] molar ratio and the interlayer spacing of modified LDHs. The surface area and pore volume, especially mesoporous surface area and pore volume, were improved compared with parent [Ni,Mg,Al]-LDH, and the catalytic activity of the resultant Ni/MgOAl2O3 catalyst in CO2 reforming of CH4 was enhanced. NaOH concentration has a slight influence on CO2 conversion and stability of the resultant Ni/MgOAl2O3 catalyst. The Ni/MgOAl2O3 prepared from the modified [Ni,Mg,Al]-LDH with 0.1 mol/L NaOH exhibits the best stability and anti-coke deposit ability. CH4 and CO2 conversions retain at about 91% and 96%, respectively, along with a H2/CO ratio of about 0.90 after reaction of 28 h. High CO2/CH4 molar ratio can improve catalytic stability, resistance to coke deposit and Ni sintering of the catalyst.