New results on the effect of TiO₂ on Pd/La₂O₃-CeO₂-Al₂O₃ systems for catalytic oxidation of methane in the presence of H₂O and SO₂ have been received. Low-temperature N₂-adsorption, XRD, SEM, HRTEM, XPS, EPR and FTIR techniques were used to characterize the catalyst. The presence of Ce³⁺ on the catalytic surface and in the volume near the lantana was revealed by EPR and XPS. After aging, the following changes are observed: (i) agglomeration of the Pd-clusters (from 8 nm to 12 nm); (ii) transformation of part of the TiO₂ from anatase to larger particles of rutile; and (iii)—the increase in PdO/Pd—ratio above its optimum. The modification by Ti of the La₂O₃-CeO₂-Al₂O₃ system leads to higher resistance towards the presence of SO₂ most likely due to the prevailing formation of unstable surface sulfites instead of thermally stable sulfates. Based on kinetic model calculations, the reaction pathway over the Pd/La₂O₃-CeO₂-TiO₂-Al₂O₃ catalyst follows the Mars–van Krevelen mechanism. For evaluation of the possible practical application of the obtained material, a sample of Pd/La₂O₃-CeO₂-TiO₂-Al₂O₃, supported on rolled aluminum-containing stainless steel (Aluchrom VDM^®), was prepared and tested. Methane oxidation in an industrial-scale monolithic reactor was simulated using a two-dimensional heterogeneous reactor model.

The present study aims to investigate a Pd catalyst on a complex multi-oxide medium-entropy support interlayer La₂O₃-CeO₂-ZrO₂-Al₂O₃ and its possible use as catalysts for methane abatement applications. The low-temperature N₂-adsorption, XRD, TEM, XPS, TPD, and TPR techniques were used to characterize the catalyst. The palladium deposition on the supports leads to the formation of PdO. After the catalytic tests, the metal-Pd phase was observed. The complete oxidation of methane on Pd/La-Ce-Zr-Al catalyst takes place at temperatures above 250 °C, and in the presence of water vapor, the reaction temperature increases to about 70 °C. The careful choice of constituent oxides provides a balance between structural stability and flexibility. The alumina and lanthanum oxide ensure the high specific surface area, while the simultaneous presence of zirconia and ceria leads to the formation of a mixed-oxide phase able to interact with palladium ions by incorporating and de-incorporating them at different conditions. The mechanism of Mars–van Kerevelen was considered as the most probable for the reaction of complete methane oxidation. The possibility of the practical application of Pd-modified La-Ce-Zr-Al catalyst is evaluated. The use of a mix of multiple rare and abundant oxides makes the proposed catalyst a cost-effective alternative.

Catalysts with a Ruddlesden–Popper structure (LaSrFeO₄, La_0.5Sr_1.5FeO₄, and La_1.5Sr_0.5FeO₄) were successfully synthesized and tested for the complete oxidation of C₁–C₄ hydrocarbons (methane, ethane, propane, and n-butane) as representative compounds of volatile organic compounds (VOCs), which are responsible for the global warming process. The samples were characterized by nitrogen physisorption, XRD, TEM, Mössbauer spectroscopy, XPS, O₂-TPD, and “depletive oxidation”. The catalyst La_0.5Sr_1.5FeO₄ showed the highest activity in the VOCs oxidation processes. This activity was connected with the enhanced strontium content in the catalyst, leading to high surface Fe⁴⁺ concentration and increased Fe⁴⁺/Fe³⁺ ratio, which promoted oxygen mobility and surface oxidation. Kinetic studies, along with physicochemical characterization, indicated that the ethane combustion proceeds via the Mars–van Krevelen mechanism.

In this work, nanocrystalline high-entropy spinels with the nominal composition (Co,Mn,Ni,Cr,Fe)₃O₄ and different Fe contents were synthesized by a facile solution combustion method and evaluated as catalysts for the complete oxidation of light hydrocarbons and methanol decomposition. Structural characterization by XRD, SEM, TEM, XPS, Mössbauer spectroscopy, and N₂ physisorption confirmed the formation of single-phase cubic spinels and mesoporous morphology. Increasing the Fe content resulted in changes in surface elemental distribution without altering the oxidation states of the cations. Among the investigated catalysts, HES-Fe 1:1 exhibited the highest specific surface area, favorable surface enrichment in Co and Mn, and the best catalytic performance for the complete oxidation of light hydrocarbons. In methanol decomposition, HES-Fe 1:1 showed the highest methanol conversion at lower temperatures, whereas HES-Fe 1:2 exhibited the highest CO selectivity, making it the most efficient catalyst for syngas production. The results establish a relationship between Fe content, surface composition, redox properties, and catalytic performance, revealing high-entropy spinels as promising catalysts for environmental catalysis and syngas production.

SrMoO₄ nanoparticles were effectively prepared through direct mechanochemical activation carried out under ambient conditions. In order to improve their catalytic properties, the obtained SrMoO₄ was modified with palladium and comprehensively characterized by X-ray diffraction analysis (XRD), N₂-physisorption, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Catalytic tests for VOCs were carried out. The XRD patterns showed that the as-synthesized SrMoO₄ and Pd/SrMoO₄ samples are crystallized in a scheelite-type structure. It was found that the use of SrMoO₄ as a catalytic support enables the preparation of a catalytic system with highly dispersed Pd species and strong metal–support interactions. The presence of reduced Mo species on the Pd-modified SrMoO₄ catalyst, together with oxygen-deficient surface regions, suggests that the Mo species actively participate in the catalytic process through their redox cycle. The possible coexistence of both Pd²⁺ and Pd⁰ species and partially reduced Mo environments further indicates the active involvement of the Pd/SrMoO₄ surface in oxygen activation and VOC oxidation, supporting the Mars–van Krevelen mechanism as the most probable reaction route. In addition, the high stability of the material demonstrates the reliability of the Pd-modified SrMoO₄ catalyst. Therefore, this material can be considered a promising catalyst in environmental catalysis.

This study investigates the effect of dilute organic acid treatment on the structural, textural, electronic, and catalytic properties of layered La–Sr–Fe–O Ruddlesden–Popper (R–P) oxides using XRD, TEM, BET, Mössbauer spectroscopy, XPS, H₂-TPR, C₂H₆-TPR and catalytic testing. XRD and TEM confirm that the overall layered Ruddlesden–Popper structure is preserved after acid treatment and during catalysis, with minor changes in phase composition, including a decrease in the n = 1 phase and a relative increase in the n = 2 phase. BET analysis shows increased specific surface area and pore volume, forming a more accessible mesoporous structure that is retained under reaction conditions. Mössbauer spectroscopy and XPS reveal an increased Fe⁴⁺ fraction and formation of hydroxylated and carbonated surface species stabilizing active Fe sites. During catalysis, a dynamic Fe³⁺/Fe⁴⁺ redox cycle occurs, along with surface restructuring and involvement of non-lattice oxygen, while the bulk electronic structure remains largely unchanged. Catalytic tests show improved activity, with a 40–60 °C reduction in operating temperature for all acid-treated samples, independent of acid type. This enhancement is mainly attributed to surface-related modifications, including removal of surface Sr-containing species, improved surface accessibility, and enhanced mass transport, while the overall R–P structural remains preserved.