Research was conducted on a cobalt spinel catalyst doped with Ni and Mg for the efficient decomposition of nitrous oxide (N2O),to address the issue of N2O emissions from ammonia-fueled engines.Series of transition metal M(Cu,Ni,Mg)doped cobalt spinels(Co3O4)were synthesized by the co-precipitation method to form composite metal oxides MxCo3-xO4,and their catalytic activities under different atmospheres were investigated. The Ni0.4Mg0.2Co2.4O4 catalyst could achieve a 90％ decomposition efficiency of N2O at 350℃,and complete conversion is achieved at 480℃ under the reaction with 10％ steam. A series of characterization methods revealed that:The simultaneous doping of Ni and Mg into the lattice structure was well integrated,forming a more complete overall spinel structure;The synergistic effect of Ni and Mg,along with Co as active sites,resulted in better dispersion of the cobalt spinel,and unlike doping with Cu and other elements that formed corresponding metal oxide impurities,reduced the number of active centers,which was an important reason for the further improvement of its modification effect;Due to the simultaneous doping of Ni and Mg into the lattice,the doped cobalt spinel experienced lattice expansion and increasing of lattice dimensions,resulting in a significant enhancement of the specific surface area,which was higher than that of individual doping with Ni or Mg,thus increased the number of active sites for contact,enabling it to have a lower reaction temperature;XPS analysis revealed that in Ni0.4Mg0.2Co2.4O4,Co2+and Ni2+had the highest binding energy,and the density of electron cloud is the lowest,which facilitated the transfer of electrons from N and O to them;The proportion of Co2+,as the main decomposition active center,was the highest,which explained the phenomenon of its highest decomposition efficiency at the same temperature from the perspectives of energy and valence state;Under H2-TPR conditions,as the doping amounts of Ni and Mg increase,the reduction temperature of H2 was higher,indicating stronger reducibility at both high and low temperatures,which was beneficial for the adsorption and reduction of the high-valent N in N2O;Ni0.4Mg0.2Co2.4O4 also showed good stability under a 60000h-1 air flow at 60h (maintaining a conversion rate of around 90％ at 350℃).
关键词
氨燃料/氧化亚氮/钴尖晶石/Ni掺杂催化剂/催化分解/复合金属氧化物
Key words
ammonia fuel/nitrous oxide/cobalt spinel/Ni-doped catalyst/catalytic decomposition/composite metal oxide
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