Preparation Of SiO₂ And CNTs Confined Ni-based Catalysts And Study On Their Catalytic Performance In Dry Reforming Of Methane

Dry reforming of methane can convert two major greenhouse gases?CH₄ and CO₂?and make comprehensive use of the two major carbon sources.While alleviating global warming,this reaction also produces H₂/CO=1 syngas to use as the vital intermediate for carbonyl or Fischer-Tropsch synthesis,which has important research value and practical significance in the chemical,environmental and energy fields.However,due to the lack of cost-effective and stable catalyst application,the reaction has not been able to achieve industrialization.Nickel has shown much promise and comparable activity to that of noble metals and its low-cost allows Nickel receiving extensive attention and research.However,there are two major problems of sintering and carbon deposition that seriously affect the catalytic performance of Ni-based catalysts for dry reforming of methane.In this paper,the stabilization of active Ni was realized by the confinement of SiO₂ and CNTs supports and superior catalytic performance was obtained.The specific work is as follows:An ammonia-assisted hydrothermal one-step synthesis method was used to obtain Ni-SiO₂ catalyst with core-shell-like structure in the absence of template agent.During the 30 h stability test of dry reforming of methane,no obvious sintering phenomenon occurred and nearly no carbon deposition was found.This preparation process was easy to operate and took the low-cost silica sol as support,which had certain economic benefits.Utilizing the complexation of ammonia and Ni species,the effective dispersion was achieved under hydrothermal conditions with small Ni particle size?³.2 nm?and strengthened metal-support interaction.The confinement of SiO₂ support stabilized Ni nanoparticles and inhibited metal sintering while preventing carbon deposition.Ni-based catalyst encapsulated by carbon nanotubes?CNT?with adding MgO as promoter was prepared by impregnation method and had improved dry reforming of methane catalytic activity as well as better catalytic stability.The results showed that due to the well-defined morphology and unique electronic structure,CNT not only provided the loaded Ni an effective space confinement,but also adjusted the reduction behavior of Ni species by changing their electronic structure with the lack of electrons inside the CNT.In addition,the relatively narrow diameter of CNT was more conducive to reducing the size of the loaded Ni species?<4.5 nm?,and the addition of MgO increased the adsorption of CO₂ and suppressed the gasification of CNT,promoting the stability of the catalyst.