Preparation Of Ni-based Catalysts And Application In Steam Reforming Of Methane

Natural gas, as a kind of the efficient high quality clean energy, plays an important role in the social development and world’s energy consumption structure. Hydrogen is a clean energy carrier and plays an important role in the chemical and oil refining industry. Steam reforming of methane (SRM) is one of the most important techniques to produce hydrogen. Catalyst is the key of SRM. Nobel metal catalyst exhibits higher catalytic activity, better anti-resistance to carbon formation, but the expensive price limits its practical application. Nickel-based catalyst, owing to its relatively low cost and high activity, has become the focus in SRM research and industry. However, Ni is easy to sinter under high temperature and the resistance to carbon formation and sulfur poisoning is poor. To improve catalytic performances, anti-resistance of carbon formation and sulfur poisoning, in this paper, nickel-based catalysts were made by using Mo as a promoter and preparing the new composite catalyst support. The prepared Ni-based catalysts and catalyst supports were characterized by XRD, H2-TPR, N2adsorption and TG-DTG, and applied in SRM to study the effect of catalysts on the reaction performance.Firstly, the influence of impregnation sequences and impregnated amounts of Mo on the characters of catalysts and reactions were investigated, and the results showed that the catalysts Ni impregnated prior to Mo have high component dispersion and are easy to be reduced from XRD and H2-TPR data. The catalytic initial activity reduces with the increasing amount of Mo, and the reduction degree of initial activity is different with different impregnation sequences. When Mo impregnated amount is less than0.5wt.%, the initial activity of catalyst declines little and shows good catalytic stability. The TG-DTG of the used catalysts show that Mo added in catalyst can significantly reduce carbon formation. The impregnation sequences and impregnated amounts of Mo show different sulfur resistance in SRM, and the best sulfur poisoning resistance can be achieved when Mo impregnated after active component Ni and Mo content is0.2wt.%.Secondly, a new composite catalyst support (AAC) was prepared by carbonizing mixture of alumina and activated carbon using sucrose as a binder. The support precursor needs to be carbonized at600℃, and no new phase is created in the carbonization process, and specific surface area of the support is between alumina and activated carbon resulting from TG-DTG, XRD and N2adsorption analysis. The catalysts were prepared by impregnating Ni on AAC followed by carbonized at650℃resulting from TG-DTG analysis making use of carbon reducibility at high temperature. The active components disperse uniformly in the composite supporter, and the specific surface area of Ni/AAC is larger than that of the traditional Ni/Al2O3catalyst resulting from XRD and N2adsorption analysis. The SRM reaction containing hydrogen sulfide shows that the Ni/AAC has better sulfur-resistant performance than Ni/Al2O3. The process parameters of the catalyst support preparation have great influence on the sulfur-resistance, and the catalyst prepared with a support from carbonization of the mixture with20%AC, Al2O3/AC=4:1, and20%(based on the sum of Al2O3and AC) sucrose at600℃shows the best sulfur-resistance in SRM with hydrogen sulfide.