Construction Of Highly Active Nickel-based Catalysts In Methane Reforming Reaction

The excessive use of oil by the rapid industrial development and population growth has raised the concern of global warming and the depletion of the finite oil reserves. Methane reforming with CO2 was an ideal reaction to transform two greenhouse gases CH4 and CO2 into syngas(H2 and CO), which can be efficiently converted into a variety of valuable products, e. g. methanol, Fischer-Tropsch Fuels. This dissertation focused on the organic agents modify and synthesis strategy on the nickel-based catalysts. Ni-based catalysts modified with organic agents, or doping yttrium using impregnation method were investigated in the methane reforming reaction. The structure of the catalysts and supports were characterized by using XRD, N2 adsorption-desorption isotherms, H2-TPR, TEM,FT-IR and TG techniques and the prominent role of organic agents was revealed in improving the catalytic performance. Besides, for the different carriers(Al2O3 and Si O2), the synthesis strategy(co-impregnation method and sequential impregnation) method were also compared. Related research indicated the influence of impregnation method on the catalyst structures. The results further illustrated the superiority of organic agents and modification for carriers for nickel-based catalysts in the catalyst structure and catalytic performance. The acquired research results from this work were of great beneficial for improving the Ni-based catalysts.First, Ni-based catalysts modified with organic agents(glycol, citric acid) were synthesized successfully via ultrasonic method and the effect of different alcohols on the methane conversion rate was studied in order to determine the proper alcohols additives.Second, the effect of the citric acid content on the physicochemical properties was studied in order to determine the proper additives. Explore the synergy modification effect of CA and EG over Ni CA-x/Si O2-EG catalysts. The temperature programmed reduction(TPR) revealed that the reduction peak shifted to higher temperature with increasing CA loading, which was attributed to the smaller metallic Ni size of the reduced catalysts. The transmission electron microscopy(TEM), X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FT-IR) confirmed that the addition of organic additive modified the silica surface and retained the metallic Ni species, and thus preventing the metal aggregation at high reaction temperature.Finally, the addition of yttrium by different impregnation strategy(co-impregnation and sequential impregnation) was studied in the Ni-based catalysts with Al2O3, Si O2 as the carriers. The effect of yttrium addition and impregnation sequence on the change of the physicochemical properties of catalyst was discussed.