Synthesis and Characterization of A-Site Doped Lamno3 Nano Catalysts and its Application for Soot Oxidation

Abstract

A series of barium doped LaMnO3 perovskite nano catalysts were synthesized using the citric acid sol gel method. The prepared nano catalysts were characterized using the various characterization techniques such as XRD, ICPAES, FTIR, SEM, HRTEM, TPR and BET. The Xrd results showed the purity of the prepared catalyst as no segregated phases were observed and also confirming the crystallinity of the prepared catalyst. The surface area achieved in this experiment presented one of the highest reported in literature. The doping of the perovskite catalysts helps in increasing the surface area. The ICPAES results shows the efficiency of the preparation method adopted. The catalytic evaluation shows that upon introduction of Ba into the perovskite structure, the catalytic performance of the catalyst were greatly increased with LBM3 giving the lowest T50 at 550°C

Novel La 1− x Ca x MnO 3 perovskite materials for chemical looping combustion applications

“…All samples exhibited one broad desorption peak centered at 770°C‐780°C, with a shoulder at 900°C, while LCM100 present one additional peak centered at 450°C. According to the literature, 44,47 the peak at 450°C is related with the desorption of oxygen from the surface vacancies of the OCM. This kind of oxygen species, named superfacial α‐oxygen, are often related to the catalytic performance, due to the fact that these species are correlated to the reduction of Mn 4+ and considered as the active oxygen species which can initiate the oxidation reaction 20,41,44,47 .…”

“…According to the literature, 44,47 the peak at 450°C is related with the desorption of oxygen from the surface vacancies of the OCM. This kind of oxygen species, named superfacial α‐oxygen, are often related to the catalytic performance, due to the fact that these species are correlated to the reduction of Mn 4+ and considered as the active oxygen species which can initiate the oxidation reaction 20,41,44,47 . The broad O 2 desorption peak at 770°C‐780°C is due to the desorption of lattice oxygen (named intrafacial β‐oxygen), which is the oxygen placed in the lattice of perovskite oxides, is the connection of the metal cations of La, Ca, and Mn site, and it is associated with the reduction‐oxidation ability of the Mn‐site cation 22,44,45,47 …”

“…The hydrogen consumption at the low temperature area is assigned to the reduction of Mn 4+ into Mn 3+ and also the reduction of some Mn 3+ . Based on the literature, the reduction profiles of La 1 À x Ca x MnO 3 or with the general formula of ABO 3 perovskites have shown 20,22,[41][42][43][44][45][46][47][48] that the peaks at low temperature area correspond to the oxygen removal from the perovskite structure presenting oxidative non stoichiometry and the reduction of Mn 4+ to Mn 3+ , while the peaks at high temperature (above 600 C) correspond to the reduction of Mn +3 to Mn +2 and the collapsing of the perovskite structure. 22,42,43,47 The shape and the maximum temperature of the peaks seem to be affected from Ca addition.…”

“…Based on the literature, the reduction profiles of La 1 À x Ca x MnO 3 or with the general formula of ABO 3 perovskites have shown 20,22,[41][42][43][44][45][46][47][48] that the peaks at low temperature area correspond to the oxygen removal from the perovskite structure presenting oxidative non stoichiometry and the reduction of Mn 4+ to Mn 3+ , while the peaks at high temperature (above 600 C) correspond to the reduction of Mn +3 to Mn +2 and the collapsing of the perovskite structure. 22,42,43,47 The shape and the maximum temperature of the peaks seem to be affected from Ca addition. The reduction profile of LCM30 perovskite shifted to lower temperatures in comparison with LCM00 and present higher H 2 consumption (Table 2), which indicates an increment of the cation/anion vacancies, facilitating the reduction of Mn 4+ .…”

“…This kind of oxygen species, named superfacial α-oxygen, are often related to the catalytic performance, due to the fact that these species are correlated to the reduction of Mn 4+ and considered as the active oxygen species which can initiate the oxidation reaction. 20,41,44,47 The broad O 2 desorption peak at 770 C-780 C is due to the desorption of lattice oxygen (named intrafacial β-oxygen), which is the oxygen placed in the lattice of perovskite oxides, is the connection of the metal cations of La, Ca, and Mn site, and it is associated with the reduction-oxidation ability of the Mn-site cation. 22,44,45,47 A higher quantity of lattice oxygen is desorbed from the perovskites with the increase of Ca content, showing that the replacement of La 3+ by Ca 2+ increased the amount of surface vacancies in the perovskite structure, facilitating the reduction of Mn 4+ as observed in H 2 -TPR profiles.…”