LaBO3 (B = Mn, Fe, Co, Ni, Cu, and Zn) Catalysts for CO + NO Reaction

A series of transition-metal LaBO3 perovskites (B = Mn, Fe, Co, Ni, Cu, and Zn) have been synthesized and tested as catalysts for the simultaneous removal of CO and NO in a fixed-bed reactor. To improve the catalytic activity, LaFeO3, the most active formulation, was modified by partially substituting other active metals (Mn, Co, and Cu) for Fe in the perovskite formulation (LaFe0.7M0.3O3). The results revealed that Mn substitution significantly improved the catalytic activity because it increased the Mn(IV)-to-Mn(III) ratio, leading to the generation of a large amount of structural defects, and also because it increased the amount of reducible active sites.Financial support from the Iran National Science Foundation (INSF) is gratefully acknowledged

Experimental and Modeling Study of CO-Selective Catalytic Reduction of NO Over Perovskite-Type Nanocatalysts

In this work LaFeO3, LaFe0.7Mn0.3O3 and LaMn0.7Fe0.3O3 nanocatalysts with perovskite structures have been synthesized by sol-gel method. The selective catalytic reduction of NO with CO (CO-SCR) using synthesized nanocatalysts was investigated in a plug flow reactor. The kinetics of CO-SCR process was studied and three kinetic models were used to describe the behavior of the system, including power low model (PLM), kinetic model 1 (KM1) and kinetic model 2 (KM2). The KM1 was the best model with correlation coefficients of 0.9924, 0.9911 and 0.9902 and the sum of squared errors of 0.0504, 0.0488 and 0.0397, for LaFeO3, LaFe0.7Mn0.3O3 and LaFe0.3Mn0.7O3 catalysts, respectively. By comparing experimental results with the predicted results of the KM1, it was found that the proposed model can predict the performance of catalysts in the CO-SCR process with considerable precision. The structure and morphology of perovskite-type oxides were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively

NO + CO reaction over LaCu0.7B0.3O3 (B = Mn, Fe, Co) and La0.8A0.2Cu0.7Mn0.3O3 (A = Rb, Sr, Cs, Ba) perovskite-type catalysts

In this paper, catalytic reduction of NO by CO over perovskite-type oxides LaCu0.7B0.3O3 (B = Mn, Fe, Co) synthesized by sol–gel method was investigated. LaCu0.7Mn0.3O3 showed the highest activity among LaCu0.7B0.3O3 perovskite catalysts (88% CO conversion and 93% NO conversion at 350 °C). The effect of alkali and alkaline earth metals (Rb, Sr, Cs and Ba) on the structure and catalytic activity of LaCu0.7Mn0.3O3 perovskite catalysts was also investigated. The results showed that catalytic activity was improved by partial substitution of La by alkali and alkaline earth metals. The superior activity of La0.8Sr0.2Cu0.7Mn0.3O3 with respect to other catalysts (93% CO conversion and 96% NO conversion at 350 °C) was associated with a higher reducibility at low temperature, more oxygen vacancies and synergistic effect between Cu and Mn. The catalysts were characterized by XRD, BET, H2-TPR, XPS and SEM

Catalytic Reduction of NO by CO over LaMn1−xFexO3 and La0.8A0.2Mn0.3Fe0.7O3 (A = Sr, Cs, Ba, Ce) Perovskite Catalysts

In this study, LaMn1−xFexO3 (x = 0, 0.3, 0.5, 0.7, 1) and La0.8A0.2Fe0.7Mn0.3O3 (A = Sr, Cs, Ba, Ce) perovskite oxides were synthesized by sol–gel method and their activities were evaluated in catalytic reduction of NO by CO. Perovskite catalysts were characterized by XRD, BET, H2-TPR, XPS and SEM. Synthesized perovskites present a high activity for the catalytic reduction of NO by CO, LaMn0.3Fe0.7O3 Show the highest activity among LaMn1−xFexO3 perovskite catalysts (71 % CO conversion and 82 % NO conversion at 350 °C). The effect of partial substitution of Sr, Cs, Ba and Ce in A-site was also examined on the structure and catalytic activity of LaMn0.3Fe0.7O3 perovskite catalyst. La0.8Sr0.2Fe0.7Mn0.3O3 and La0.8Ce0.2Fe0.7Mn0.3O3 present the highest activities among La0.8A0.2Fe0.7Mn0.3O3 perovskites. The introduction of Sr2+ and Ce4+ in A-site of perovskite change the reducibility of B-site cations and Fe4+/Fe3+ and Mn4+/Mn3+ ratios, and increase Oads/Olatt ratio and these factors create structural defects in perovskite which lead to higher catalytic activities.Financial supports from the Iran National Science Foundation (INSF) are gratefully acknowledged

Promotion of La(Cu0.7Mn0.3)0.98M0.02O3−δ (M = Pd, Pt, Ru and Rh) perovskite catalysts by noble metals for the reduction of NO by CO

To evaluate the structural and spectroscopic steering factors of noble metal promotion in the catalytic reduction of NO by CO, a series of La(Cu0.7Mn0.3)0.98M0.02O3−δ (M = Pd, Pt, Ru, Rh) perovskite catalysts is investigated. The materials are synthesized by a sol-gel method and characterized by X-ray powder diffraction (XRD), electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). All metal-promoted perovskites exhibit a comparatively higher activity for catalytic reduction of NO by CO with respect to pure La(Cu0.7Mn0.3)O3−δ . Among all catalysts tested, the La(Cu0.7Mn0.3)0.98Pd0.02O3−δ perovskite shows the highest catalytic activity, which is tentatively related to a combined synergistic effect of improved oxygen vacancy activity and noble metals. Additionally, the redox chemistry of the catalysts in different reducing (H2) and oxidizing (NO, O2) atmospheres is tested. An enhanced kinetic reducibility, especially with Pd, was observed. All the H2-reduced catalysts are capable of reducing NO. At low and intermediate temperatures, the formation of N2O is observed, but at higher temperatures NO is exclusively converted to N2. The introduction of noble metals leads to new adsorption sites for NO. As XPS suggests a tendency for depletion of noble metals in the surface-near regions, while the catalytic activity in NO reduction at the same time appears much improved, directed noble metal promotion with modest amounts especially in surface-near regions during synthesis appears as an encouraging method to economize the use of the latter.This work was performed within the framework of the funding programme IMPULSE Iran Austria, financed by funds of the OeAD fonds and of the Ministry of Science, Research and Technology of the Islamic Republic of Iran. We also thank the SFB F45-N16 special research program for financial support. This work was performed within the framework of the research platform ‘‘Materials and Nanoscience” and the special PhD program ‘‘Reactivity and Catalysis”, both at the University of Innsbruck