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

As an ideal secondary energy,H₂ has received extensive attention from all over the world because of its high combustion calorific value（142.35 k J/g）and no pollution during utilization.With the continuous development of hydrogen fuel cell electric vehicles（FCEVs）,the demand for hydrogen energy will continue to increase in the future.Among various processes,steam reforming of methane（SRM）is one of the most mature and economical hydrogen production methods,in which about 80%of the hydrogen is produced by SRM.The most commonly used catalyst for SRM reaction is Ni-based catalyst,which has the advantages of being more economical and efficient than noble metals,but this type of catalyst still has some problems.Due to the relatively low Taman temperature(T_Tam=590°C)of metal Ni,Therefore,Ni nanoparticles（NPs）are likely to sinter under high temperature,water-containing operating conditions.Even if the water-to-carbon ratio is reduced,commercial Ni Al catalysts are very prone to carbon deposition at high temperatures,making the catalysts less stable.The key to solving the sintering problem is to prepare a catalyst that is highly dispersed and can inhibit the aggregation of Ni particles;the key to solving the carbon deposition problem is to prepare a catalyst that has better activating H₂O performance and can take away carbon from the catalyst surface in time.In this paper,different SRM catalysts were prepared from the aspects of embedded structure design,control of metal Ni particle size,and metal-support interaction,and the coupled SRM reaction of cold plasma catalysis was explored.Firstly,a method to prepare well-confined Ni NPs by precisely tuning the reduction temperature of nickel-containing phyllosilicate（PSi）was adopted to obtain Ni@PSi catalysts.The H₂ reduction of the Ni-PSi precursor at 600°C to build the intercalated structure yielded the Ni@PSi-600 catalyst,in which uniform Ni NPs（about 3.0 nm）were intercalated into the PSi structure.This structure not only endowed the highest reaction rate of methane steam reforming（SRM）,but also suppressed the sintering of Ni NPs under the harsh reaction conditions of SRM（800°C,WHSV=3,000,000 m L/g/h）.At the same time,it was found that the reduction temperature that was too high（850°C）or too low（400°C）could not form such an intercalated structure,resulting in rapid sintering and deactivation of the catalyst during the reaction.Secondly,the use of cold plasma（NTP）provides a possibility for the SRM reaction to occur at low temperature,but when pure plasma catalyzes the SRM reaction,the catalyst is easily deactivated due to the faster decomposition of CH₄.Therefore,it is particularly necessary to combine the catalyst with NTP.β-Mo₂C is considered to be an effective component for activating H₂O,and the Ni/β-Mo₂C-Al（2:1）catalyst formed by mechanical mixing with Ni/γ-Al₂O₃ can match the activation rate of H₂O with that of CH₄.,inhibited the generation of carbon deposition,thereby improving the catalytic stability.At the same time,the addition ofβ-Mo₂C promotes the accumulation of surface charges,which is beneficial to improve the discharge power,and due to the strong interaction between Ni andβ-Mo₂C,the nickel nanoparticles are redispersed on the surface ofβ-Mo₂C.Compared with the undoped Ni/Al₂O₃ catalyst,the Ni/β-Mo₂C-Al（2:1）catalyst obtained by mechanical mixing has better activity and stability.