Preparation And Properties Of Novel Zirconia Supported Ni Catalyst For Dry Reforming Of Methane

The dry reforming of methane has been recognized as an efficient way for transformation both greenhouse gases?CH4 and CO2?into the synthesis gas?H2 and CO?,and the synthesis gas has been efficiently converted into the methanol,ammonia,dimethyl ether,higher alcohols,light olefin and feedstock for downstream chemical production and liquid fuels.The nickel with high activity comparable to those of noble metals has been extensively employed for reforming of methane.However,the drawback of Ni-based is prone to rapid deactivation deriving from carbon deposition and sintering at the higher temperature.Especially,the rapid deactivation led by coke deposition derived from dry reforming of methane has been considered as a bottleneck problem for the industrial application of Ni-based catalyst.Therefore,the development of a high coke-tolerance and sintering resistant of Ni-based catalyst for dry reforming of methane has been attracted great research interests.In this paper,from the viewpoint of improving the catalytic activity,stability and coke-resistance,a series of novel supported Ni-based catalysts have been developed for the methane reforming,and the relationship between catalytic performance for dry reforming of methane as well as Ni-based catalysts was discussed.The main contents are as follows:?1?The developed supported Ni-based catalyst was synthesized by L-Arginine ligand-assisted impregnation approach.This method efficiently facilitates Ni dispersity,reduces Ni crystalline size and strengthens Ni-support interaction as well as increases the catalytic activity and stability for reforming of methane in comparison with nickel nitrate impregnation method.?2?The preparation of laminaria japonica-like hierarchically structured zirconia?ZrO₂-lj?via a combined hydrothermal-calcination method using a low-cost of ZrOCl₂·8H₂O as the Zr precursor,glucose and hexamethylenetetramine as structuredirecting agent was synthesized.The as-synthesized laminaria japonica-like hierarchically structured ZrO₂-lj exhibits high thermal stability in comparison with the traditional zirconia nanoparticulates?ZrO₂-np?.Furthermore,the Ni/ZrO₂-lj catalyst has more Lewis basicity and NiO with strong metal-support interaction,and displays much superior activity,stability and lower coke rate?30 h of time on stream,6.8 mg gcat-1 h-1?in comparison with Ni/ZrO₂-np catalyst.?3?The development of dahlia-like hierarchically structured ZrO₂ support?ZrO₂-1.4?with using the ammonium fluoride?NH4F?as the structure-directing agent has been synthesized.The dosage ofNH4F has a great influence on the morphologies of ZrO₂ supports,and dahlia-like hierarchically structured ZrO₂ support was synthesized by appropriate of NH4F dosage.The supported Ni catalyst on dahlia-like hierarchically structured ZrO₂ support?Ni/ZrO₂-1.4?demonstrates much higher Ni dispersity,stronger CO2 adsorbtion sites in comparison with the supported Ni catalyst on laminaria japonica-like hierarchically structured zirconia?Ni/ZrO₂-lj?.Furthermore,the Ni/ZrO₂-1.4 catalyst exhibits superior activity,stability as well as lower coke rate?30 h of time on stream,3.6 mg gcat-1 h-1?.?4?According to NH4F-Urea hydrothermal method,the pinecone shape ZrO₂ was prepared by adjusting dosage of NH4F,dosage of urea,hydrothermal temperature,and hydrothermal time,and the supported Ni catalyst exhibits superior catalytic performance in comparison with the supported Ni catalyst on dahlia-like hierarchically structured zirconia?Ni/ZrO₂-1.4??30h of time on stream,3.3 mg gcat-1 h-1?.The optimal zirconia supported Ni catalyst?Ni/ZrO₂-FUAH?was selected.?5?The long-term stability of optimal Ni/ZrO₂-FUAH for dry reforming of methane was investigated.The optimal Ni/ZrO₂-FUAH catalyst exhibits superior catalytic stability and coking rate of 0.6 mg gcat-1 h-1 after 100h on stream.Therefore,it is a promising catalyst for industry application.