Preparation Of Catalysts Of Ni-M（La, Ce, Fe, Co）/ZrO₂-MONtmorillonite Nanocomposites And Study On Their Methanation Performance

The production of synthetic natural gas (SNG) by carbon monoxide or carbon dioxide and hydrogen from the blast furnace can reduce carbon emissions and ease the environmental pressure, as well as alleviate the situation of the lack of natural gas in China, and thus has important practical significance.In this study, the support material of ZrO2-montmorillonite nanocomposites was prepared under hydrothermal condition using ZrO(NO)3·2H2O and montmorillonite as raw materials. A series of Ni/ZrO2-montmorillonite catalysts and a series of Ni-M(La, Ce, Fe, Co)/Zr02-montmorillonite catalysts were prepared by incipent impregnation method. The nanocomposite supports and the catalysts were characterized by the X-ray diffraction (XRD), the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), and the Energy dispersive spectrometer (EDS) analysis, the nitrogen adsorption-desorption, the temperature-programmed reduction (TPR) and the thermogravimetry and differential thermal analysis (TG-DTA). The CO and CO2methanation performances of the catalysts were investigated in a tubular reactor at a temperature range of300-500℃and the atmospheric pressure. For CO methanation, the GHSV was10000h-1, and H2/CO=3; for CO2methanation, the GHSV was12000h-1, and H2/CO2=4. The research content and results are as follows: 1. For the ZrO2-montmorillonite nanocomposites, with increasing the mass fraction of ZrO2, the aluminum in montmorillonite was partly leached out in the acidic condition and the specific surface area and pore volume of the nanocomposites increased. But the layer structure of montmorillonite preserved well enough and the zirconia dispersed well on the layers of montmorillonite.2. The content that was difficult to be reduced in the catalysts decreased with the increase of the content of zirconia and the deduction of the content of aluminum. The introduction of zirconia in the catalysts was beneficial to the CO conversion and the methane selectivity for the CO methanation. But for CO2methanation, the CO2conversion decreased below450℃and increased over450℃with increasing the content of zirconia. The methane selectivity tended to increase in the temperature range of300-500℃. The introduction of zirconia in the catalysts was beneficial to enhancing the stability and the carbon deposition-resistance for the CO and CO2methanation.3. By comparison of the Ni-M(La, Ce, Fe, Co)/Zr02-montmorillonite catalysts and the Ni/ZrO2-montmorillonite catalysts, the specific surface areas were comparable and the pore volumes were slightly decreased. The doping of the metals changed the reduction temperature of NiO and decreased the nickel content that was difficult to be reduced.4. For the CO methanation, doping transition metals or rare earth elements was beneficial to the enhancement of the CO conversion and the methane selectivity, Ce and Co being the best. But for CO2methanation, doping transition metals or rare earth elements was disadvantage to the CO2conversion below450℃and was beneficial to the CO2conversion over450℃. Doping Fe was beneficial to increasing the methane selectivity but cerium was averse to the methane selectivity.