Preparation of La-Mn-O Perovskite Catalyst by Microwave Irradiation Method and its Application to Methane Combustion

Tailoring the Composition of BaxBO3 (B = Fe, Mn) Mixed Oxides as CO or Soot Oxidation Catalysts in Simulated GDI Engine Exhaust Conditions

Mixed oxides with perovskite-type structure (ABO₃) are promising catalysts for atmospheric pollution control due to their interesting and tunable physicochemical properties. In this work, two series of Ba_xMnO₃ and Ba_xFeO₃ (x = 1 and 0.7) catalysts were synthesized using the sol-gel method adapted to aqueous medium. The samples were characterized by μ-XRF, XRD, FT-IR, XPS, H₂-TPR, and O₂-TPD. The catalytic activity for CO and GDI soot oxidation was determined by temperature-programmed reaction experiments (CO-TPR and soot-TPR, respectively). The results reveal that a decrease in the Ba content improved the catalytic performance of both catalysts, as B0.7M-E is more active than BM-E for CO oxidation, and B0.7F-E presents higher activity than BF for soot conversion in simulated GDI engine exhaust conditions. Manganese-based perovskites (BM-E and B0.7M-E) achieve better catalytic performance than iron-based perovskite (BF) for CO oxidation reaction due to the higher generation of actives sites.

Structural Insight into La0.5Ca0.5Mn0.5Co0.5O3 Decomposition in the Methane Combustion Process

Perovskite-like solid solution La_0.5Ca_0.5Mn_0.5Co_0.5O₃ was tested during the total methane combustion reaction. During the reaction, there is a noticeable decrease in methane conversion, the rate of catalyst deactivation increasing with an increase in temperature. The in situ XRD and HRTEM methods show that the observed deactivation occurs as a result of the segregation of calcite and cobalt oxide particles on the perovskite surface. According to the TGA, the observed drop in catalytic activity is also associated with a large loss of oxygen from the perovskite structure.

Enhanced Catalytic Oxidation of Toluene over Manganese Oxide Modified by Lanthanum with a Coral-Like Hierarchical Structure Nanosphere

Coral-like lanthanum manganese oxides (La_yMnO_x) with a hierarchical structure nanosphere were successfully prepared using a simple method, which presented a high-efficiency catalytic performance for toluene combustion. Among them, La_0.08MnO_x with the Mn₃O₄ phase exhibits superior catalytic activity, such as a lower T₉₅ value (218 °C), excellent H₂O resistance, and catalytic stability. The effects of La addition on the bulk and surface physicochemical properties of La_yMnO_x were investigated by sorts of characterization including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption-desorption, temperature-programmed reduction with H₂, temperature-programmed desorption of O₂, X-ray photoelectron spectroscopy, and so forth. The results demonstrate that the doping of La can induce the variation of physicochemical properties and the formation of more surface oxygen species and high valence state amorphous manganese oxides, improving low-temperature reducibility, which facilitates good catalytic activity for La_0.08MnO_x. A series of in situ diffuse reflectance infrared Fourier transform spectroscopy experiments for toluene adsorption were performed on the La_0.08MnO_x catalyst pretreated under different atmosphere conditions to investigate the role of oxygen species and the reaction processes. The results indicate that the abundant surface oxygen species over La_0.08MnO_x can make the rapid formation of benzoic acid species, further transfer into CO₂ and H₂O, which is considered as the key factor in the activation and oxidation of toluene.

NO oxidation performance and kinetics analysis of BaMO3 (M=Mn, Co) perovskite catalysts

Perovskite is an efficient and emerging catalyst for NO oxidation. In this study, BaMnO₃ and BaCoO₃ perovskite catalysts were synthesized by the sol-gel method, and their catalytic oxidation performances of NO were studied. The catalytic performances indicated that BaMnO₃ and BaCoO₃ perovskites had the highest NO oxidation activities with the NO conversions of 78.2% at 350 °C and 84.3% at 310 °C, respectively. The high activities of BaMnO₃ and BaCoO₃ perovskite catalysts were related to the abundant surface adsorption oxygen (O_A = 76.21% and 78.57%, respectively) and the high concentration of Mn⁴⁺ (Mn⁴⁺/Mn = 66.95%) and Co³⁺ (Co³⁺/Co = 63.8%). Moreover, the results of FT-IR and kinetics revealed that NO and O₂ adsorbed on the surface of samples and combined with the B-O band to form bidentate nitrate and bridging nitrate, which eventually was converted into NO₂. The kinetics analysis revealed that the NO oxidation reaction followed the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. In addition, the activation energies were 36.453 kJ/mol for BaMnO₃ and 30.081 kJ/mol for BaCoO₃, implying that BaMnO₃ and BaCoO₃ provide low-cost and efficient catalysts, which can be comparable to Pt noble metal catalysts.

Plasma catalytic oxidation of toluene over double perovskite-type oxide via packed-bed DBD

Various perovskite-type catalysts including La₂CoMnO₆, LaCoO₃, and LaMnO₃ are first evaluated for the activities toward C₇H₈ removal. Experimental results indicate that double-type La₂CoMnO₆ shows better activity if compared with single perovskites due to high lattice oxygen content and good reducibility. Subsequently, perovskite catalysts are combined with plasma (NTP) to form in-plasma catalysis (IPC) and post-plasma catalysis (PPC) systems. The results indicate that IPC systems have better higher performance than that of NTP-alone and PPC. Especially, high C₇H₈ conversion (100%) and mineralization efficiency (96.8%) can be achieved with the applied voltage of 18 kV and temperature of 120 °C when La₂CoMnO₆ is integrated with NTP to form IPC system. Also, it owns the highest energy efficiency (0.14 g/kWh). It is concluded that IPC performance for C₇H₈ removal is closely related with the properties of catalyst surface. In addition, the kinetics of IPC systems are investigated by a simplified model, and the result indicates that IPC with La₂CoMnO₆ as catalyst has a higher overall energy constant. This study reveals that double-type La₂CoMnO₆ is of higher activity than single perovskites for C₇H₈ removal, and demonstrates that double-type La₂CoMnO₆ is of high potential to form plasma catalysis system for VOCs removal.

Di-metal-doped sulfur resisting perovskite catalysts for highly efficient H2-SCR of NO

Lanthanide perovskite catalysts doped with limited palladium (to improve activity) and cerium (to improve sulfur resistance) were prepared using sol-gel method. In different B sites, lanthanide perovskites were studied at harsh conditions for H₂ selective catalytic reduction of NO. The activity sequence was as follows: LaCeMnPd > LaCeCoPd > LaCeFePd. LaCeMnPd had a high NO conversion of 96.6% at only 150 °C. And it also had a surprising SO₂ resistance in different SO₂ concentrations. After cutting out SO₂, NO conversion recovered rapidly to its original level, indicating that the slight deactivation was reversible. In addition, the effect of gas hourly space velocity, H₂/NO ratio, O₂, and SO₂ concentration was studied. And XRD, energy-dispersive X-ray, SEM, XPS, H₂-temperature programmed reduction, and NH₃-temperature programmed desorption were performed to characterize the catalysts. Graphical abstract ᅟ.

Removal of VOCs from gas streams with double perovskite-type catalysts

Double perovskite-type catalysts including La₂CoMnO₆ and La₂CuMnO₆ are first evaluated for the effectiveness in removing volatile organic compounds (VOCs), and single perovskites (LaCoO₃, LaMnO₃, and LaCuO₃) are also tested for comparison. All perovskites are tested with the gas hourly space velocity (GHSV) of 30,000hr^-1, and the temperature range of 100-600°C for C₇H₈ removal. Experimental results indicate that double perovskites have better activity if compared with single perovskites. Especially, toluene (C₇H₈) can be completely oxidized to CO₂ at 300°C as La₂CoMnO₆ is applied. Characterization of catalysts indicates that double perovskites own unique surface properties and are of higher amounts of lattice oxygen, leading to higher activity. Additionally, apparent activation energy of 68kJ/mol is calculated using Mars-van Krevelen model for C₇H₈ oxidation with La₂CoMnO₆ as catalyst. For durability test, both La₂CoMnO₆ and La₂CuMnO₆ maintain high C₇H₈ removal efficiencies of 100% and 98%, respectively, at 300°C and 30,000hr^-1, and they also show good resistance to CO₂ (5%) and H₂O_(g) (5%) of the gas streams tested. For various VOCs including isopropyl alcohol (C₃H₈O), ethanal (C₂H₄O), and ethylene (C₂H₄) tested, as high as 100% efficiency could be achieved with double perovskite-type catalysts operated at 300-350°C, indicating that double perovskites are promising catalysts for VOCs removal.

Preparation of Pd supported on La(Sr)-Mn-O Perovskite by microwave Irradiation Method and Its Catalytic Performances for the Methane Combustion

In this work, a series of palladium supported on the La0.8Sr0.2MnO3.15 perovskite catalysts (Pd/LSM-x) with different Pd loading were prepared by microwave irradiation processing plus incipient wetness impregnation method and characterized by XRD, TEM, H2-TPR and XPS. These catalysts were evaluated on the lean CH4 combustion. The results show that the Pd/LSM-x samples prepared by microwave irradiation processing possess relative higher surface areas than LSM catalyst. The addition of Pd to the LSM leads to the increase in the oxygen vacancy content and the enhancement in the mobility of lattice oxygen which play an important role on the methane combustion. The Pd/LSM-3 catalysts with 4.2wt% Pd loading exhibited the best performance for CH4 combustion that temperature for 10% and 90% of CH4 conversion is 315 and 520 °C.

Promotional role of La addition in the NO oxidation performance of a SmMn2O5 mullite catalyst

A series of La_xSm_1−xMn₂O_δ (x = 0, 0.1, 0.3, 0.5) catalysts were synthesized through a co-precipitation method. The catalytic activity for NO oxidation was enhanced with La substitution, and the maximum activity was achieved at x = 0.3.

A mullite oxide catalyst of SmMn2O5 for three-way catalysis: synthesis, characterization, and catalytic activity evaluation

CO conversion as a function of temperature for SMO and LCO is shown in the graphical abstract image. SMO reached 95% conversion at 150 °C and showed a better CO oxidation activity than LCO.

Three dimensionally ordered macroporous Pd-LaMnO3 self-regeneration catalysts for methane combustion

Three-dimensionally ordered macroporous (3DOM) Pd-LaMnO3 self-regeneration catalysts were successfully prepared. After reduction treatment at 500 °C, the catalyst exhibited the best catalytic activity for methane combustion. The excellent catalytic performance was attributed to the ordered porous structure, the large surface area, and the strong interaction between segregated Pd and the LaMnO3 substrate.

One-pot synthesis of Ag-modified LaMnO3–graphene hybrid photocatalysts and application in the photocatalytic discoloration of an azo-dye

Ag-modified LaMnO₃–graphene nanocomposites possess excellent photocatalytic activity for Direct Green BE photodegradation and the active hole generated in Ag/LaMnO₃–graphene plays a key role.

Three-dimensionally ordered macroporous LaMnO3 with tunable oxygen vacancies via nitric acid-aided modulating and their catalytic combustion properties

Three-dimensionally ordered macroporous (3DOM) LaMnO₃ oxides with tunable oxygen vacancies have been successfully fabricated via a facile nitric acid-aided modulating sol–gel method.

High specific surface area LaMO3 (M = Co, Mn) hollow spheres: synthesis, characterization and catalytic properties in methane combustion

LaMO₃ (M = Mn, Co) hollow spheres were synthesized by a carbon sphere template method, while a slow heating rate resulted in multishelled hollow spheres.