The catalytic activity in the soot combustion is reported for a series of potassium-promoter alumina supported catalysts prepared by the sol-gel method to be used in the catalytic combustion of soot. The studied syste...The catalytic activity in the soot combustion is reported for a series of potassium-promoter alumina supported catalysts prepared by the sol-gel method to be used in the catalytic combustion of soot. The studied systems correspond to CeO2-Al2O3 and La2O3-Al2O3 with charges of 3 and 5 wt% of CeO2 and La2O3. Potassium impregnation is performed to reach 3 atoms of K per nm2 of the mixed oxide. The effect of the potassium incorporation increases its reducibility, decreases the surface area and forms a new type of oxygen that is stronger than the oxygen in mixed oxides with similar chemical nature. The existence of potassium oxides, K2O and oxygen responsible for the vacancies and/or lattice defects (O2−) are related to good catalytic activity. Additionally, the presence of alkali affects the structural and textural characteristics of the catalyst, promoting the catalytic activity in soot combustion.展开更多
Substituted La0.6Ca0.4Fe1-xNixO3 (0.0 ≤ x ≤ 1.0) perovskite-type oxides prepared by the amorphous citrate method have been investigated as catalysts in the dimethyl ether (DME) oxidation reaction. The samples with a...Substituted La0.6Ca0.4Fe1-xNixO3 (0.0 ≤ x ≤ 1.0) perovskite-type oxides prepared by the amorphous citrate method have been investigated as catalysts in the dimethyl ether (DME) oxidation reaction. The samples with an x ≤ 0.3 composition show an orthorhombic structure, while the intermediate compositions with 0.5 ≤ x ≤ 0.9 show a less crystalline orthorhombic perovskite structure with segregated phases that increase upon increasing the Ni content. The progressive substitution of Fe3+ by Ni2+ in La0.6Ca0.4FeO3 entails the progressive formation of oxygen vacancies and Fe4+ species for Ni substitution degrees of x ≤ 0.5. For larger degrees of substitution with x > 0.7, segregated phases and a progressive loss of the perovskite structure are detected. The highest catalytic performance for the total combustion of DME is obtained from equimolar substitution in the B-site position (Fe0.5Ni0.5), in which a large extent of Fe4+ species and oxygen vacancies are present.展开更多
文摘The catalytic activity in the soot combustion is reported for a series of potassium-promoter alumina supported catalysts prepared by the sol-gel method to be used in the catalytic combustion of soot. The studied systems correspond to CeO2-Al2O3 and La2O3-Al2O3 with charges of 3 and 5 wt% of CeO2 and La2O3. Potassium impregnation is performed to reach 3 atoms of K per nm2 of the mixed oxide. The effect of the potassium incorporation increases its reducibility, decreases the surface area and forms a new type of oxygen that is stronger than the oxygen in mixed oxides with similar chemical nature. The existence of potassium oxides, K2O and oxygen responsible for the vacancies and/or lattice defects (O2−) are related to good catalytic activity. Additionally, the presence of alkali affects the structural and textural characteristics of the catalyst, promoting the catalytic activity in soot combustion.
文摘Substituted La0.6Ca0.4Fe1-xNixO3 (0.0 ≤ x ≤ 1.0) perovskite-type oxides prepared by the amorphous citrate method have been investigated as catalysts in the dimethyl ether (DME) oxidation reaction. The samples with an x ≤ 0.3 composition show an orthorhombic structure, while the intermediate compositions with 0.5 ≤ x ≤ 0.9 show a less crystalline orthorhombic perovskite structure with segregated phases that increase upon increasing the Ni content. The progressive substitution of Fe3+ by Ni2+ in La0.6Ca0.4FeO3 entails the progressive formation of oxygen vacancies and Fe4+ species for Ni substitution degrees of x ≤ 0.5. For larger degrees of substitution with x > 0.7, segregated phases and a progressive loss of the perovskite structure are detected. The highest catalytic performance for the total combustion of DME is obtained from equimolar substitution in the B-site position (Fe0.5Ni0.5), in which a large extent of Fe4+ species and oxygen vacancies are present.
