Studies On Modification, Characterization And Catalytic Oxidation Properties Of LaSrCoO₄ Composite Materials

In this dissertation, a series of LaSrCoO4 composite materials were synthesized by the polyacrylamide-gel method. The effects of different synthesis conditions, B-site adulteration with different metal ions (B'= Mn, Fe, Ni and Cu) and O-site adulteration with halogen ions (F^-, Cl^-) on the structure and performance of LaSrCoO₄ were deeply studied. The supported composite materials, with LaSrCoO₄ acting as support or activity ingredient, were also studied, respectively. The catalytic activity towards CO and C₃H₈ oxidation has been investigated, too. The physicochemical properties and function mechanism were characterized by means of TPD, BET, XRD, TEM, XPS and iodometry methods.The results show that the two LaSrCoO4 composite materials calcined at 950 and 850℃ have tetragonal K₂NiF₄ structure. With the increase of calcined temperature, the conglomeration of the sample becomes more obvious, the particle size increases, and the specific surface area decreases. TPD results show that there are three 02-desorption peaks and two CO₂-desorption peaks over the two samples, respectively. In compare to the sample calcined at 950℃, the other one has almost the same quantity of ordinarily chemisorbed oxygen and CO₂ desorbed at higher temperature. The sample calcined at 850℃ has greater quantity of the chemisorbed oxygen in the oxygen vacancies, the lattice oxygen, and the desorbed CO₂ at lower temperature, and the activation energy of CO reaction is less with higher catalytic activity.LaSrCo₀.9Ni₀.1O₄ and LaSrCoO₄ are nanostructured materials with tetragonal K₂NiF₄ structure. B-site adulteration with nickel enhances the catalytic activity, the O₂-adsorption quantity, the CO₂-desorption quantity and the lattice distortion, while reduces the average crystal size.O-site doped LaSrCoO3 7F0 3 and LaSrCoC>3 7CI0.3 are perovskite-like composite materials with tetragonal K2NiF4 structure. The adulteration of Cl" leads to the increase of the chemisorbed oxygen in the oxygen vacancies, the mobile lattice oxygen, Co + content, the average valence of Co ions and catalytic activity. While the adulteration of F" has opposite effects.LaSrCoCU and the supported composite materials, LaSrCoC>4 supporting Ni or Pd, have the same quantity of ordinarily chemisorbed oxygen. According to the order of LaSrCoCU, Ni/LaSrCoC>4, Pd/LaSrCoO*) the oxygen vacancies and the mobile lattice oxygen increase, and the lattice oxygen becomes more mobile, and the activation energy of CO reaction is less with higher catalytic activityThe supported composite materials, ZrO2 or T1O2 acting as support, were synthesized. According to the order of LaSrCoO4, LaSrCoO4/ZrO2, LaSrCoO4/ TiO2, the catalytic activity, the quantity of the ordinarily chemisorbed oxygen and the chemisorbed oxygen in the oxygen vacancies increase, and the desorbed temperature decreases gradually.