金属Sr、Fe掺杂对LaCoO3催化氧化碳烟及抗硫性能影响

利用柠檬酸-EDTA(乙二胺四乙酸)配位法制备了La1-xSrxCo1-yFeyO3催化剂,展现出较好的催化氧化碳烟(soot)活性和抗硫性能。通过X射线衍射(XRD)、傅利叶红外光谱(FT-IR)、扫描电镜(SEM)、H2-程序升温还原(H2-TPR)、X射线光电子能谱(XPS)和SO2程序升温脱附(SO2-TPD)等研究了Sr、Fe掺杂对催化剂物理化学性质及抗硫能力影响。当Sr掺杂LaCoO3时有利于形成较多的表面吸附氧(O2^-、O^-)和氧空位,且低温氧化还原性能亦有较大改善,提高了催化氧化碳烟活性,其Ti(起燃温度)和Tm(最大碳烟燃烧速率温度)分别为284和347℃。当催化剂同时掺杂Sr、Fe时,其低温氧化还原性能进一步改善,并形成较多Fe^4+离子,有利于提高催化氧化碳烟活性。催化剂SO2中毒失活主要来源于Co^2+/Co^3+和表面吸附氧的硫酸化(SO3^2-、SO4^2-)。XPS和SO2-TPD结果表明,LaSrCoFeO3抗硫性主要来源于Fe^3+与SO2结合形成的硫酸盐物种,降低了SO2对活性组分表面吸附氧和Fe^4+毒化。TPO(程序升温氧化)结果表明,硫化后的LaSrCoFeO3-S仍具有较好的催化氧化碳烟活性,其Tm仅为361℃,表明Sr、Fe同时掺杂具有较好的低温催化氧化碳烟活性和良好的抗硫性能。

Effect of Sr and Fe Doped LaCoO3 on Catalytic Oxidation of Soot and Sulfur Resistance

A series of perovskite-type La1-xSrxCo1-yFeyO3 catalysts were successfully prepared by the citric acid-EDTA complexation.The catalysts exhibited excellent catalytic oxidation soot activity and sulfur resistance.The characterization of X-ray diffraction(XRD),fourier transform infrared spectra(FT-IR),scanning electron microscope(SEM),H2-temperature-programmed reduction(H2-TPR),X-ray photoelectron spectroscopy(XPS)and SO^2-temperature programmed desorption(SO2-TPD)were used to reveal the effect of Sr and Fe doping on the physicochemical properties and sulfur tolerance of La1-xSrxCo1-yFeyO3 catalysts.Experimental results demonstrated that when the Sr doped with LaCoO3,it was beneficial for the catalyst to form more surface adsorption oxygen(O^2-or O^-)and oxygen vacancies,thereby improving both the low-temperature redox ability and catalytic oxidation soot activity of catalyst.Ti(ignition temperature of soot)and Tm(complete conversion temperature of soot)are only 284 and 347℃.Furthermore,with the doping of Fe,the low-temperature redox performance of catalyst was further improved,because the high-valent ions(Fe^4+)were formed in the surface of catalyst,the Fe4+ion could enhance the oxidation soot activity of catalyst.Moreover,the poisoning of SO2 was mainly attributed to the sulfation(SO3^2-,SO4^2-)of Co^2+/Co^3+and surface adsorbed oxygen,leading to deactivating the active site(O^2- or O^-and Fe^4+)of catalyst.Simultaneous doping of Sr and Fe can form a strong interaction,which can effectively inhibit the deposition of sulfur species on the catalyst surface and reduce the poisoning of SO2 into the catalyst.Both XPS and SO2-TPD characterizations showed that the sulfur resistance of catalyst was mainly attributed the competitive adsorption of metal ions(Fe^3+)on SO2,which could effectively reduce the poisoning of SO2 on the surface adsorption oxygen and Fe^4+.TPO(temperature programmed oxidation)activity characterization showed that LaSrCoFeO3-S still maintained good catalytic oxidation soot activity.Ti and Tm were 320 and 361℃,respectively,indicating that the simultaneous doping of Sr and Fe has excellent low-temperature catalytic soot activity and good sulfur poisoning ability.