The Study Of Ni/SiC_XO_Y Catalyst Supported On SiC Porous Ceramic And Its Ethanol Steam Reforming For Hydrogen Production

Carbon peaking and carbon neutrality are important goals of my country’s green development,and hydrogen energy is considered to be the ultimate solution to achieve this goal.The hydrogen production technology of ethanol steam catalytic reforming based on porous support is a kind of hydrogen production technology with great development potential and expected to be miniaturized and real-time.The properties of the porous support and the catalyst and their relationship are the key factors affecting the performance of ethanol steam catalytic reforming for hydrogen production.Due to its excellent corrosion resistance,high temperature resistance,mechanical properties and pore channel designability,SiC porous ceramic is ideal catalyst support and reaction microchannels for ethanol steam reforming at high temperature.However,SiC porous ceramic is difficult to form a high bonding force with the catalyst due to the surface characteristics of the its inner pores and the surface chemical inertness of SiC itself.Ni-based catalysts are important non-precious metal catalysts for hydrogen production from ethanol steam reforming and have the advantages of high cost-efficient,good catalytic activity,and high hydrogen selectivity,but at the same time,they have the disadvantage of easy carbon deposition and deactivation.In this paper,Niwas used as the catalyst,SiC porous ceramic was used as the catalyst support and the microchannel for the reforming hydrogen production reaction.From the interface structure design and control between the Nicatalyst and SiC support,the particle size control of the catalyst Ni,and the SiC porous ceramic-based Three aspects of the hydrogen production reaction from ethanol reforming were studied.The main research contents and results were as follows:1.Investigating the effects of impregnating solution types and film-forming additives on the film formation of PCS precursor and its pyrolysis product SiC_XO_Y on the surface of SiC inner pores and catalyst loading,and discuss the mechanism of in-situ reduction of NiO by PCS to form elemental Nicatalyst.The results showed that the inverse microemulsion modified by epoxy in the oil phase can form a uniform and complete film on the inner pore surface of the SiC porous ceramic.The SiC_XO_Y film formed by the catalyst through the pyrolysis of PCS was uniformly supported in the SiC porous ceramic.The dehydrogenation coupling reaction that occurred during the PCS pyrolysis process generates H₂,which reduced NiO to Niin situ.2.The effect of the mass ratio of PCS/Nion the Ni/SiC_XO_Y catalyst was systematically studied;the effect of Nicatalyst and Ni/SiC_XO_Y catalyst on the morphology and support strength of the catalyst were compared;the reaction conditions for catalytic hydrogen production were optimized,and The stability of the catalyst was evaluated.The results showed that the R-PCS100Ni45 catalyst with a mass ratio of PCS/Niof 100:45 was uniformly and densely distributed on the SiC support,and the Niparticle size control and loading strength of the Ni/SiC_XO_Y catalyst were significantly better than that of the pure Nicatalyst.Under optimized reaction conditions（the reactant flow rate was 3ml/h,the ratio of water to alcohol was 8,the reaction temperature was 500℃）,the ethanol conversion rate can reach 96%,and the hydrogen selectivity can reach 74.9%.3.The Ni/SiC_XO_Ycatalyst was prepared by the inverse microemulsion-coprecipitation method,and the effect of NH₃·H₂O addition on the elemental Niparticles in the Ni/SiC_XO_Y catalyst was discussed.The stability of the catalyst was evaluated and the catalyst size was studied for its carbon deposition mechanism.The results showed that Ni（OH）₂ enclosed in the water phase microdroplets of the reverse microemulsion was affected by its concentration and the oil phase,and its crystal growth was inhibited.The Niparticles had high sphericity,and were uniformly distributed in the SiC_XO_Y film,and the size is multi-level distribution,the smallest particles were below 5nm.RP-35 catalyst under optimized reaction conditions（reactant flow rate was3ml/h,water-to-alcohol ratio was 8,reaction temperature was 500℃）,ethanol conversion rate can reach 100%,hydrogen selectivity can reach 75%,the ethanol conversion rate was still as high as 95%,and the H₂ selectivity was 69.2%after reaction for 20h,which significantly improved the activity and stability of the catalyst.The study on the carbon deposition mechanism of catalysts of different sizes showed that the smaller the Niparticles,the higher the activity,and the faster the mass transfer rate of carbon in the Nicatalyst.The carbon deposition form on the catalyst surface changed from coated carbon to carbon nanowires.The reduction of the coated carbon content slowed the deactivation rate of the catalyst and prolonged the service life of the catalyst.