Combustion of sewage sludge in a fluidized bed of catalyst: ASPEN PLUS model.

Separation of nickel from cobalt and manganese in lithium ion batteries using deep eutectic solvents

Mixtures of copper and iron oxides are used as industrial catalysts for the water-gas shift (WGS, CO + H2O f H2 + CO2). In-situ time-resolved X-ray diffraction, X-ray absorption fine structure, and atomic pair distribution function analysis were used to study the reduction of CuFe2O4 with CO and the behavior of CuFe2O4 and Cu/Fe2O3 catalysts under WGS reaction conditions. MetalToxygenTmetal interactions enhance the stability of Cu 2+ and Fe 3+ in the CuFe2O4 lattice, and the mixed-metal oxide is much more difficult to reduce than CuO or Fe2O3. Furthermore, after heating mixtures of CuFe2O4/CuO in the presence of CO or CO/H2O, the cations of CuO migrate into octahedral sites of the CuFe2O4 lattice at temperatures (200-250 C) in which CuO is not stable. Above 250 C, copper leaves the oxide, the occupancy of the octahedral sites in CuFe2O4 decreases, and diffraction lines for metallic Cu appear. From 350 to 450 C, there is a massive reduction of CuFe2O4 with the formation of metallic Cu and Fe3O4. At this point, the sample becomes catalytically active for the production of H2 from the reaction of H2O with CO. Neutral Cu 0 (i.e., no Cu 1+ or Cu 2+ cations) is the activemore » species in the catalysts, but interactions with the oxide support cannot be neglected. These studies illustrate the importance of in situ characterization when dealing with mixed-metal oxide WGS catalysts.« less

In Situ Characterization of CuFe2O4 and Cu/Fe3O4 Water-Gas Shift Catalysts

Ternary Fe–Zn–Al Spinel Catalyst for CO2 Hydrogenation to Linear α-Olefins: Synergy Effects between Al and Zn

The oxidation of CO has been studied over Fe−Al and Cu−Fe−Al oxide nanocomposite catalysts prepared by melting of copper, iron, and aluminum nitrates. It was shown that the addition of copper significantly increases the catalytic activity of the Fe−Al nanocomposites. The catalysts were characterized by low‐temperature nitrogen adsorption, X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). It was found that the catalysts contain Fe2O3 with the hematite structure modified by aluminum. Copper in the three‐component catalyst is in the Cu2+ state, forming CuO and CuFeOx clusters on the catalyst surface. An increase in the copper content leads to the formation of a CuxAlyFe3‐x‐yO4 spinel phase. In situ XPS study showed that a treatment of the catalysts in a CO flow leads to the reduction of both copper and iron cations into the metallic state. In contrast, a treatment in a CO/O2 flow leads only to partial reduction of Cu2+ to Cu1+, while Fe3+ are not reduced. The tests of catalytic activity performed in a flow fixed bed reactor using a CO pulse technique showed that the light‐off temperature in the oxidation of CO over the Cu−Fe−Al nanocomposite catalysts depends on the copper content. The minimal light‐off temperature was achieved over the catalyst containing 5 wt% CuO. In addition, we performed kinetic measurements in a differential reactor and obtained the activation energy and the reaction orders with respect to the reactants. The reaction mechanism of the catalytic oxidation of CO and the origin of active species are discussed.

Kinetic and mechanistic study of CO oxidation over nanocomposite Cu−Fe−Al oxide catalysts

The Fe-Al and Cu-Fe-Al oxide nanocomposites active in the oxidation of CO were studied by XRD, TEM, EDX, Raman spectroscopy, TPR-H2 and differential dissolution techniques. The nanocomposites were prepared by fusion of aluminum, iron, and copper salts that leads to their inhomogeneity. The Al3+ cations partially dissolve in the Fe2O3 lattice, which leads to a significant decrease in size of iron oxide. Copper locates in the Al-rich agglomerates to form CuO nanoparticles and partially dissolves in alumina. The dissolution of copper in iron oxide and formation of a (Cu,Al,Fe)3O4 spinel was observed only at a high Cu loading. Hence, aluminum plays the role of a textural promoter, preventing sintering and stabilization of the high specific surface area of oxide. Copper does not act as a textural promoter, as it does not affect the crystal size of iron oxide. The addition of Cu increases the catalytic activity of iron oxide-based catalysts.

Chemical and texture promoters in Cu-Fe-Al oxide nanocomposite catalysts for combustion of solid fuel gasification products

The Mn-Ce oxide catalysts active in the oxidation of CO were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), transition electron microscopy (TEM), energy dispersive X-Ray (EDX), and a differential dissolution technique. The Mn-Ce catalysts were prepared by thermal decomposition of oxalates by varying the Mn:Ce ratio. The nanocrystalline oxides with a fluorite structure and particle sizes of 4–6 nm were formed. The introduction of manganese led to a reduction of the oxide particle size, a decrease in the surface area, and the formation of a MnyCe1−yO2−δ solid solution. An increase in the manganese content resulted in the formation of manganese oxides such as Mn2O3, Mn3O4, and Mn5O8. The catalytic activity as a function of the manganese content had a volcano-like shape. The best catalytic performance was exhibited by the catalyst containing ca. 50 at.% Mn due to the high specific surface area, the formation of the solid solution, and the maximum content of the solid solution.

https://www.mdpi.com/2079-4991/11/4/988/pdf

The Formation of Mn-Ce Oxide Catalysts for CO Oxidation by Oxalate Route: The Role of Manganese Content.

The effect of the substitution of copper ions by titanium ions in LaCuxTi1-xO3 (x = 0.4–0.8) mixed oxide on physicochemical and catalytic properties in syngas conversion was studied. The activation and catalytic testing were accompanied by reduction of part of copper ions and destruction of the perovskite structure leading to the removal of titanium and copper cations. An increase in the titanium content leads to a decrease in the proportion of reduced copper with the preservation of the defective perovskite-like oxide substrate. The application of KIT-6 silica for increasing the surface area essentially enhanced catalytic efficiency of the system. The main product of syngas conversion was methanol; its formation selectivity on the synthesized mixed oxides is comparable to the selectivity on conventional CuZnAl oxide catalyst. With increasing copper content in the samples, the selectivity for higher alcohols increases and contribution of water-gas shift reaction to the total CO conversion rate grows.

Syngas conversion over perovskite-like LaCuxTi1-xO3/KIT-6 catalysts

A series of Mn-Ce oxide catalysts with Mn:Ce = 1 was synthesized by oxalate route under different annealing conditions The physicochemical properties were characterized by means of XRD, HRTEM, N2 adsorption, TPR, XPS and DD technique All the catalysts were investigated in the CO oxidation reaction The annealing conditions exhibited a great impact on the structural properties, which resulted in different catalytic performance The activity of the samples calcined in air exceeds the activity of the samples prepared in argon at a similar temperature In the inert at 300–400 °C, the oxalate precursor does not completely decompose to oxide; at 500–600 °C, MnO and ceria are formed For the Mn-Ce oxide catalyst obtained in air, the combination of XRD, DD and TPR showed that the catalyst consists of a MnxCe1-xO2-δ (x ~ 02) solid solution, amorphous and crystalline manganese oxides (Mn3O4, Mn2O3, Mn5O8) XPS analysis indicates that the catalyst surface contains Mn cations in the form of Mn2+, Mn3+ and Mn4+ An increase in the calcination temperature results in the oxide sintering During the variation of the calcination time at 300 °C, the composition of the MnxCe1-xO2-δ solid solution does not change, while transformations occur in Mn oxides The most active Mn-Ce catalyst was obtained by annealing at 300 °C for 10 h in air and consists of a MnxCe1-xO2-δ solid solution and Mn5O8

Alena A. Pochtar

Papers

Chemical and texture promoters in Cu-Fe-Al oxide nanocomposite catalysts for combustion of solid fuel gasification products

The Formation of Mn-Ce Oxide Catalysts for CO Oxidation by Oxalate Route: The Role of Manganese Content.

Syngas conversion over perovskite-like LaCuxTi1-xO3/KIT-6 catalysts

The Formation of Mn-Ce Oxide Catalysts for CO Oxidation by Oxalate Route: The Role of Annealing Conditions