Preparation Of Silicon Carbide Supported Ni-based Catalysts For Low-Temperatured CO Methanation

Natural gas is increasingly used in human life and industrial development as a clean energy source,and the demand is increasing day by day.However,natural gas reserves and production are seriously inadequate and cannot effectively meet current needs.At present,synthetic natural gas has become an effective means to alleviate the current shortage of natural gas,especially the preparation of synthetic natural gas through coal-based syngas,coke oven gas,calcium carbide gas and other raw materials,which is the process of CO methanation.Generally,nickel-based catalysts have excellent catalytic activity,but at high temperatures,active components are prone to sintering and carbon deposition,which affects the service life of the catalyst.Silicon carbide exhibit high thermal conductivity,excellent mechanical properties and wide-band semiconductor characteristics,and has excellent thermal stability and chemical stability,which well suited to the application of support in Ni-based catalysts.In this paper,we have mainly studied the preparation of SiC-supported Ni-based catalysts and its low-temperature methanation performance.The details are as follows:?1?Enhanced low-temperature catalytic carbon monoxide methanation performance via silicon carbide supported nickel nanoparticles.We successfully synthesized porous SiC ceramics using natural mineral vermiculite?VMT?,and prepared Ni/VMT-SiC catalyst for CO methanation.Compared with commercial SiC?COM-SiC?,VMT-SiC has high specific surface areas and large pore volumes.The catalyst of Ni/VMT-SiC shown higher Ni nanoparticles dispersion and stronger metal-support interaction.At 300 ?,the CO conversion and CH₄ selectivity of Ni/VMT-SiC are 92.3%and 81.2%,respectively,which is much higher than Ni/COM-SiC CO conversion?87.1%?and CH₄ selectivity?77.6%?.Even at 250 ?,Ni/VMT-SiC showed excellent catalytic activity with the CO conversion of 83.2%.?2?Defect-rich nickel nanoparticles supported on industrial waste silica fume during metallic silicon production with enhanced carbon monoxide methanation performance.We successfully synthesized porous silicon carbide ceramics using waste silica fume,and prepared Ni/SF-SiC with abundant defects by conventional impregnation method.And according to the density functional theory calculations?DFT?results,the Ni vacancies were more favorale for adsorbing H₂ and CO molecules,with adsorption energies of 4.88 eV and1.84 eV,respectively,resulting in significantly improved reactive activity.At 350 ?,the CO conversion and CH4 selectivity of the Ni/SF-SiC catalyst could reach 99.1%and 85.7%.And at 300 ?,the CO conversion and selectivity of Ni/SF-SiC catalysts were 98.2%and 80.5%respectively,showing good catalytic activity at low temperature.?3?Effect of La promoter on Ni/SiC catalyst and low-temperature CO methanation.We prepared a series of Ni/SiC catalysts doped with the additive La,and the additive La could effectively enhance the dispersibility of the active metal Ni,reduces the particles size of Ni.As the addition amount of La was 3%,the activity of the 3%La-Ni/SiC catalyst was optimized,and at 300 ?,the CO conversion and the CH₄ selectivity were 97.8%and 87.0%,respectively.It was found that the catalyst also exhibited excellent activity at low temperature.,at 250 ?,the CO conversion and CH₄ selectivity of the 3%La-Ni/SiC catalyst could reach 95.9%and85.1%,respectively.