Investigation of activities of LaNiMO3 (M=Mn, Co, Cu, Ag)perovskite catalysts for total oxidation of methane

In this study, synthesis and characterization of different metal-containing LaNi0.5M0.5O3 (M = Ag, Cu, Co, Mn) perovskite catalysts and activity studies for total oxidation reaction of methane were carried out. Catalysts containing LaNi0.5M0.5O3 (M = Ag, Cu, Co, Mn) were synthesized using both the co-precipitation method and the Pechini sol-gel method. X-ray diffraction, N2 adsorption/desorption, electron microscopy (SEM and HRTEM), inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray photoelectron spectroscopy (XPS) characterization techniques were applied to determine the characteristics of the synthesized catalysts. As a result of the characterization analysis; analysis of the crystal phases of catalysts, average crystal sizes, N2 adsorption / desorption isotherms, pore volume values, average pore diameters, surface areas, surface topography, ratio of components in the catalyst phase structure, elemental composition and oxidation states of the elements were made. X-ray diffraction patterns showed that NiO, La2O3, MnO, Co3O4, CuO and Ag crystal phases were formed in catalysts. It was determined that LaNi0.5Mn0.5O3 catalyst prepared by both methods from the average crystal size values calculated from the most severe peaks had higher average crystal size compared to other catalysts. Average pore diameters have shown that more than 50% of catalyst structures are generally composed of micro + meso pores. When the BET multi-point surface area results are examined, and comparison is made in terms of the preparation method, higher surface areas were obtained in the catalysts prepared by co-precipitation method. Catalytic activities of catalysts were carried out in the temperature range of 300-800oC for the total oxidation reaction of methane. The total oxidation reaction of methane was carried out without pre-treatment with O2 and pre-treatment with O2 at room temperature for 1 hour. Mn doped LaNi0.5Mn0.5O3 catalyst, synthesized by co-precipitation method, showed the best catalytic activity. While LaNi0.5Mn0.5O3 catalyst gave 50% conversion at 560oC without pretreatment for the total oxidation reaction of methane, it gave %50 conversion at 557oC with pretreatment.