EFFECT OF METAL OXIDE-SUBSTITUTED LaCoO3 PEROVSKITE SUPPORT ON THE CATALYTIC PROPERTIES OF Ni/PEROVSKITE IN CARBON DIOXIDE REFORMING OF METHANE

Abstract

The effect of the Ni loading on the LaCoO3 perovskites, the Ce substitution into La position and the transition metal (Cu, Mn and Zn) substitution into Co position on the LaCoO3 perovskites structure in Ni/perovskites catalysts was investigated. First, the LaCoO3 perovskites (LC) were prepared by flame spray pyrolysis (FSP), and then the xNi (x = 0, 2, 5 and 10 wt%) was loaded by incipient wetness impregnation method. The catalysts were investigated using a quartz tubular reactor under the atmospheric pressure of 700 oC for 15h. The Ni loading maintains the perovskite structure. The 2Ni/LC shows the highest reducibility and intensity in the La2O2CO3 phase. The LC catalyst was inactive due to the reduction temperature to 500 oC which was not enough to produce the Co metal dispered in the La2O3 support. The 2Ni/LC catalyst showed the highest CH4 and CO2 conversions and H2/CO ratio and stability for the 15 h conversion. When increasing the Ni loading by 5 and 10 wt%, the CH4 conversion decreases due to the RWGS reaction which is favored a Ni-enriched surface found on the perovskite support. And then, the 2Ni/CexLa1-xCoO3 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were investigated. The Ce contents x = 0.2, was inserted into the perovskite structure. When increasing Ce more than 0.2 ratio, it appears segregated in the CeO2 phase. CeO2 can provide the stabilization of lattice oxygen O2 on the surface which it gave the high catalytic activity and stability after the initial 3 hours. The substitution of the La site metal ion with Ce metal ion at x = 0.2, 0.4 and 0.6 show little change in the CO2 and CH4 conversion. At x=0.8 and 1.0, it shows an increase in the CO2 conversion and CO yield due to the effect of RWGS reaction. Its insertion in the perovskite structure is also possible in the low Ce-content. Finally, the transition metal (Cu, Mn and Zn) substitution into Co position were investigated. The perovskite structures were formed when using Co and Mn metals but they did not forme when using Zn and Cu metal. All of the Mn/Co ratio maintains the perovskite structure. The Mn/Co ratio at 0.05 shows the highest CH4 conversion, H2 yield and H2/CO ratio. The Mn and Co mix metals increase catalytic activity due to a change in oxygen mobility within the crystal lattice of the Co component. The Mn/Co ratio at 0.1-0.5 show a decrease in the CO2 and CH4 conversion after the 9 hr mark due to metals sintering.

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