Mesoporous LaAl_0.25Ni_0.75O₃ And In-situ Growth Of Layered Nickel Silicate Catalysts For Methane Dry Reforming

Dry reforming of methane（DRM）and carbon dioxide has attracted the attention of researchers.It can convert CH₄ and CO₂ into chemical products,which is a feasible solution for the effective utilization of greenhouse gases.In addition,the product with H₂/CO ratio of 1 is more favorable for follow-up Fischer-Tropsch synthesis and other production.Ni-based catalysts such as perovskite,silicate,etc.,with specific structural precursors,can effectively reduce the size of Ni particles and improve the interaction between Ni and support.Therefore,they are increasingly concerned by researchers.This paper focuses on the mesoporous LaAl_0.25Ni_0.75O₃ perovskite and in-situ growth of layered nickel silicate on SiO₂catalysts for dry reforming of methane.A LaAl_0.25Ni_0.75O₃ perovskite catalyst（LANO-S）was prepared by using SBA-15as templating agent and applied for methane dry reforming reaction.The LANO-S catalyst forms a mesoporous structure after removal of the templating agent and an appropriate amount of Si was doped into the LaAl_0.25Ni_0.75O₃ perovskite.After the catalyst characterization by the XRD,FT-IR,N₂-physisorption,etc.,it was found that due to the special structure of the catalyst and the proper Si doping,the specific surface area was enlarged,the interaction between Ni and support was enhanced,and the amount of strong basic sites was increased.LANO-S had higher activity and stability than the catalyst using commercial silica as a hard template（LANO-Si）and the bulk perovskite catalyst（LANO-bulk）.After 36 h of DRM reaction,more than 75%conversion of CH₄ and CO₂ was maintained under the GSHV value of 192000 m L h^-1 g^-1.A layered nickel silicate catalyst grown in situ on the surface of SiO₂was prepared by hydrothermal crystallization for methane dry reforming reaction.For comparison,three crystallization temperatures of 100,150 and 200°C were selected.When the crystallization temperature was 150°C,the catalyst had more excellent reaction performance.XRD,FT-IR,H₂-TPR and other characterization showed that Ni/SiO₂-150 had more 1:1 layered nickel silicate.1:1 layered nickel silicate was reduced gradually,which is first reduced to partial Ni and 2:1 layered nickel silicate and then completely reduced,forming the interlaced structure of Ni particles and silica.Ni/SiO₂-150 had the smallest Ni particle size after reduction,thus showing higher activity and stability in the reaction.After 60 h of DRM reaction,more than 75%conversion of CH₄and CO₂ was maintained under the GSHV value of 1200000 m L h^-1 g^-1.