Oxygen Mobility Research Articles

Conversion of CO2(g) to CO(g) via reverse water–gas shift cycle on mixed cerium/praseodymium oxides at 500 °C

Reactions of cerium/praseodymium oxides under hydrogen atmospheres, and subsequently, carbon dioxide, involved in chemical looping reverse water–gas shift cycles (RWGS) at 500 °C were investigated by in-situ high-temperature X-ray powder diffraction, FTIR and thermogravimetry. The RWGS cycle is a critical chemical process for converting carbon dioxide into useful products, such as carbon monoxide, which can be used to synthesize fuels and chemicals. The mixed oxides exploit the redox properties of Ce and Pr, which can switch between oxidation states, making them suitable for oxygen incorporation and release during the RWGS process allowing them to react with H2(g), and subsequently with CO2(g), promoting their interaction and conversion into H2O(g) and CO(g). Pure cerium and praseodymium oxides showed poor CO2(g) conversion efficiency. However, we found that nanometric Ce/Pr mixed oxides exhibit enhanced oxyreduction performance suitable for this application, particularly with a composition of 75 mol% Ce and 25 mol% Pr, significantly improved performance, achieving an average CO(g) yield of 0.6 mmol/(goxide.cycle) and a maximum rate of 0.26 mmol/(goxide.min). Pr enhances oxygen mobility in CeO2, which improves the dissociation of C═O bonds in CO2(g). This is because the remaining oxygen atoms are delivered more quickly to the support sink, thereby cleaning up the vacant sites generated during the reduction step. These findings suggest that Ce/Pr mixed oxides are highly effective for CO2(g) conversion to CO(g) via RWGS cycle, offering a potentially viable option for industrial application.

Mn-Ce solid solution growth on Mn2O3 surface to form heterostructure catalysts with multiple active sites for toluene degradation

A solid solution-heterostructure catalyst with abundant active sites was successfully constructed in this study by in situ growth of Mn-Ce solid solution on the surface of Mn2O3. The solid solution structures with optimum physical and chemical properties were synthesized initially by controlling the Mn-Ce ratios. Subsequently, the reaction time was controlled to realize the orderly growth of the solid solution on the Mn2O3 surface. The catalyst (M−CeMn0.5) with solid solution-heterostructure formed by the reaction of Ce3Mn1 and Mn2O3 for 0.5 h could reach more than 90 % toluene degradation rate at 183 °C and was operated continuously for 15 h without deactivation. XRD showed that the appropriate reaction time resulted in the active components on the catalyst surface exhibiting lower crystallinity and reduced grain size. The reduction capacity (2.28 → 10.47 mmol/g) and the mobility of lattice oxygen were significantly enhanced in the M−CeMn0.5 catalyst compared to the Mn-Ce solid solution. Meanwhile, a high content of low valent metal ions (Ce3+/Ce4+ 0.33, Mn3+/Mn4+ 1.64) and reactive oxygen species (Oads/Olatt 0.53) were also present on the catalyst surface. The DFT demonstrated that the Mn atoms and Mn-O bridge sites on the solid solution surface exhibited high adsorption energy values for toluene (−0.8402/-0.8406 eV) and oxygen (−1.6546/-1.661 eV) molecules. The TEM indicated that lattice distortion and oxygen vacancies were formed at the interface between the solid solution and Mn2O3 at the interface. The synergy of multiple active sites favors the generation of reactive oxygen species and thus promotes p-methyl dehydrogenation. Meanwhile, the high mobility of lattice oxygen facilitates the breakage of benzene ring. This study provides a new strategy for the synthesis of efficient Mn-Ce-based catalysts.

Strong interaction between promoter and metal in Pd-Ba/TiO2 catalysts for formaldehyde oxidation

As our previous works found, alkali metals have a common promotion effect on supported noble metals catalysts for formaldehyde (HCHO) oxidation. As second-group elements, alkaline earth metals (AEMs) are neighbors to the first-group elements and share some properties in common. However, detailed investigations into the specific mechanisms underlying AEMs’ effects on HCHO oxidation remain limited. In this study, we found that Ba addition showed a similar promotion effect on HCHO oxidation for Pd/TiO2. Ba species stabilized Pd groups, improved the dispersion, and even caused a large number of monatomic-like Pd sites to appear, which may be attributed to the electronic interaction between promoter and metal (EIPM) between Ba and Pd. Besides, AEM loading had the important effect of increasing the electron density of metallic Pd nanoparticles, which further improved the ability for O2 activation and so enhanced the mobility of chemisorbed oxygen on the catalyst surface. For Pd/TiO2, the HCHO oxidation path is mainly HCHO→HCOOH→HCOO→H2O+CO2. By contrast, for Pd-Ba/TiO2, with more surface-active species, the formate intermediate was more likely to be directly oxidized into H2O and CO2, which is a more effective reaction pathway. The details of the EIPM between Pd and Ba were investigated by GPAW (DFT calculation module) in ASE (Atomic Simulation Environment). The AEM Ba acted as an electron donor and could interact with Pd d orbital electrons through BaO sp orbital electrons. Ba species were highly dispersed on the carrier due to the Ba-Ti interaction. Ba species dispersed over large areas stabilized the Pd particles and donated electrons to Pd. Therefore, adding an AEM is an efficacious strategy to improve the performance of the catalytic oxidation of HCHO.

Enhancing hydrogen production via dry reforming of methane: Optimization of Co and Ni on scandia-ceria-zirconia supports for catalytic efficiency and economic feasibility

The Novel “Scandia-ceria incorporated zirconia” (10ScCeZr) is a well-recognized material in ceramic and solid oxide electrolytes due to stable phases (like cubic ZrO2) and oxide conducting phases (like hexagonal Sc4Zr3O12 phases). The objective of the current study is to introduce 10ScCeZr as support for bearing a proportional ratio of active sites (Ni and Co), investigating catalytic performance in DRM and studying the economic viability with respect to other catalysts. The 10ScCeZr support is used first time where the concentration of ceria is minimal to minimize the risk of oxidation of active sites but achieve the benefit of mobile lattice oxygen along with scandia and zirconia. Upon dispersion of different proportions of Ni and Co over 10ScCeZr, the reducibility pattern, stability of active sites, stability of oxide vacancy, and type of carbon deposit are modified markedly. Upon using 3: 1 Ni and Co over 10ScCeZr, the crystallinity of the catalyst is minimal, and the total concentration of active site and stable active sites doesn’t fluctuate more than 5Ni/10ScCeZr, and active sites are majorly derived by NiO. During the DRM, less inert carbon is deposited over the catalyst (than 5Ni/10ScCeZr). These physiochemical modifications over 3.75Ni1.25Co/10ScCeZr result in the highest 45 % H2 yield at 700 °C and 79 % H2 yield at 800 °C at the end of 300 min. The significant high operational savings due to the 0.44 % increased H2-yield validate the long-term financial benefits upon industrialization of the current catalyst. Now, this catalyst is open for further investigation on promotors’ effect and process optimization for developing a high-performance catalyst with excellent savings in H2-production through DRM.

Excellent performance of Ce doped CoMn2O4/TiO2 catalyst in NH3-SCR of NOx under H2O&SO2 conditions

Mn-based catalysts have become a research hotspot for low-temperature NH3-SCR, and the improvement of anti-SO2 poisoning performance is crucial to promote their industrial application for NH3 selective catalytic reduction of NOx. In this work, the CoMn2O4/Ce-TiO2 catalyst was able to maintain 95 % NOx conversion even in the presence of 10 vol% H2O+50 ppm SO2 for 24 h at 250 °C.The excellent performance was attributed to the large mesoporous structure, specific surface area, and the enhancement of acid and redox properties associated with the catalysts. The Ce doped CoMn2O4/Ce-TiO2 catalyst maintained Mn3+, Mn4+ and Co3+ in high concentrations on the surface, which improved the lattice oxygen mobility, and the electron transfer and interaction. The presence of more Ce4+ provided higher SCR activity due to the strong oxygen storage migration and also release ability. The reaction process of NH3-SCR for NOx removal on the surface of CoMn2O4/Ce-TiO2 catalyst mainly followed the Eley-Rideal (E-R) mechanism. The NH3 adsorbed on the catalyst surface reacted mainly with NO/NO2 species, even under H2O&SO2. The E-R reaction mechanism on the surface of CoMn2O4/Ce-TiO2 catalyst was less restricted by the inhibition of H2O&SO2. This is one of the primary reasons for the superior anti-sulfur toxicity performance of the catalyst. This work opens a new avenue for the design of efficient and environmentally friendly NH3-SCR catalysts with good application prospects.

Synergistic SiC/Co3O4 composites for enhanced microwave-assisted benzene catalytic removal performance

Microwave-assisted catalysis is a promising technique for enhancing catalytic reactions through selective heating, potentially leading to improved reaction rates and energy efficiency. However, understanding the complex interactions between microwave absorption and catalytic performance in composite catalysts remains a challenge. In this study, Cobalt oxide(Co3O4)/silicon carbide(SiC) composite catalysts with varying SiC content were synthesized and characterized to investigate the relationship between their microwave absorption properties and catalytic performance. Quantitative analysis revealed that SiC and Co3O4 absorb microwave energy through relaxation polarization and magnetic loss mechanisms, respectively. Increasing SiC content enhanced the dielectric and magnetic loss capabilities of the composites, with the Co3O4/SiC composite containing 10 wt% SiC (Co3O4/SiC-10) exhibiting a dielectric loss tangent of 3.87 and a minimum reflection loss of −35dB. However, higher SiC content decreased the surface chemically adsorbed oxygen, surface oxygen mobility, and benzene adsorption capacity, weakening the catalytic activity under conventional heating. The Co3O4/SiC-10 sample achieved a significantly better balance between microwave absorption and catalytic performance, significantly outperforming the original Co3O4 sample under microwave irradiation. These founding establishes a quantitative research methodology that correlates dielectric loss tangent, reflection loss, and other crucial parameters with microwave absorption performance and further catalytic properties, providing insights for the rational design of catalysts that optimize both microwave absorption and catalytic activity.

Influence of the La/Ce ratio on La-Ce oxides promoted by Sr in the methane oxidative coupling reaction

The high methane availability and its significant role as a greenhouse gas have led the scientific community to pursue methods for its use. This paper proposes the usage of the oxidative coupling of methane (OCM) as a promising path to transform methane directly into value-added hydrocarbons, mostly ethylene, which serves as a crucial compound in the petrochemical sector. An efficient OCM catalyst should contain substantial basicity and oxygen vacancies for providing surface electrophilic oxygen species, such as superoxides and peroxides, instrumental for boosting selectivity towards C2 products. Mixed lanthanum-cerium oxide (La-Ce) catalysts have emerged as strong candidates in OCM due to their high thermal stability, oxygen mobility, and high alkalinity. In this study, they were prepared through a surfactant-assisted hydrothermal method with different La/Ce ratios for fine-tuning their basic properties and promoting oxygen mobility on the surface of the catalysts. Samples followed a volcano-shaped relationship between C2 yield and La content, with optimal performance at a La/Ce molar ratio of 2.1, attributed to the interplay between the high amount of basic sites and oxygen vacancies, increasing the presence of superoxide species over lattice oxygen. Moreover, the Sr-promoted catalyst showed high density of strong basic sites while preserving the reactive oxygen species, achieving 20 % CH4 conversion, with 57 % C2 compounds selectivity at 750 °C and GHSV of 18.000 mL.gcat−1.h−1.

Oxygen vacancy–rich K-Mn3O4@CeO2 catalyst for efficient oxidation degradation of formaldehyde at near room temperature

Synthesis of catalysts with high catalytic degradation activity for formaldehyde (HCHO) at room temperature is highly desirable for indoor air quality control. Herein, a novel K-Mn3O4@CeO2 catalyst with excellent catalytic oxidation activity toward HCHO at near room temperature was reported. In particular, the K addition in K-Mn3O4@CeO2 considerably enhanced the oxidation activity, and importantly, 99.3 % conversion of 10 mL of a 40 mg/L HCHO solution at 30 °C for 14 h was achieved, with simultaneous strong cycling stability. Moreover, the addition of K species considerably influenced the chemical valence state of Mn from +4 (ε-MnO2) to +8/3 (Mn3O4) on the surface of CeO2, which obviously changed the tunnel structure and the number of oxygen vacancies. One part of K species is uniformly dispersed on K-Mn3O4@CeO2, and the other part exists in the tunnel structure of Mn3O4@CeO2, which is mainly used to balance the negative charge of the tunnel and prevent collapse of the structure, providing enough active sites for the catalytic oxidation of HCHO. We observed a phase transition from tunneled KMnO2 to Mn3O4 to tunneled MnO2 with the decreasing K+ content, in which K-Mn3O4@CeO2 exhibited higher HCHO oxidation activity. In addition, K-Mn3O4@CeO2 exhibited lower oxygen vacancy formation and HCHO adsorption energies in aqueous solution based on density functional theory calculations. This is because the K species provide more active oxygen species and richer oxygen vacancies on the surface of K-Mn3O4@CeO2, promote the mobility of lattice oxygen and the room-temperature reduction properties of oxygen species, and enhance the ability of the catalyst to replenish the consumed oxygen species. Finally, a possible HCHO catalytic oxidation pathway on the surface of K-Mn3O4@CeO2 catalyst is proposed.

Pt nanoparticles in cooperation with Mn-P composite drive base-free selective oxidation of 5-hydroxymethylfurfural

Selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is a key approach to sustainable upgrading of furfural based biomass resources. In this work, small Pt nanoparticles (about 2.1 nm) loaded on MnPnOx composite were shown to effectively drive the base-free aerobic oxidation of HMF to FDCA in water. Regulating the P content in carrier enabled to tune HMF conversion and product distribution. The optimal Pt/MnP0.5Ox catalyst can reach 98% yield of FDCA at 110 °C under 10 bar of O2 after 24 h. It also showed the highest initial conversion rate of HMF (13 mmol molPt−1 s−1) and productivity of FDCA (4.1 mmol molPt−1 h−1) among all the Pt/MnPnOx catalysts. The carrier effect of P addition on promoting Pt oxidation catalysis was elucidated by using rigorous kinetic investigations and comprehensive characterizations. The initial conversion rate, rate constant and apparent activation energy were independently measured on oxidation of HMF and its derived intermediates. ICP-MS, XRD, TEM, H2-TPR, O2-TPD and XPS were used to acquire catalytic properties. It was demonstrated that P addition led to changes in carrier structure and metal-support interaction, which eventually promoted the formation of highly active electron-rich Pt0 sites and mobile reactive defect oxygen species. These features allowed improving the selective oxidation catalysis of supported-Pt nanoparticles for the base-free conversion of HMF to FDCA.

Nanoarchitectonics of hollow Co3O4 through tannic acid etching of ZIF-67 for catalysis of toluene oxidation

Oxide catalysts obtained by derivatization of MOFs as precursors often have excellent results in the catalysis of VOCs. In this study, the Co3O4 catalysts obtained by pyrolysis after tannic acid etching using ZIF-67 as precursor showed excellent toluene catalytic activity. Among them, Co3O4 −1–15 showed the best catalytic activity with T90 = 219 °C (the conversion temperatures of 90 %), which was 20 °C lower than that of Co3O4 -O obtained by direct pyrolysis of ZIF-67. It also exhibits excellent stability and cyclic stability. After tannic acid treatment, Co3O4 −1–15 exposed higher surface Co3+ and Olatt (surface lattice oxygen) content, which were the key factors for its most outstanding catalytic activity. Lattice oxygen mobility and oxygen vacancies were also important factors affecting catalyst activity.

MOFs-derived CuCeOx supported on H-zeolite socony mobile-5 for catalytic oxidation of 1,2-dichlorobenzene

The catalytic elimination of chlorinated aromatic hydrocarbons is the frontier of catalytic oxidation of organic pollutants, and the screen of efficient catalysts (low cost, high activity, durability and selectivity) remains challenging. In this work, the CuCeOx derived from metal-organic frameworks supported on H-zeolite socony mobile-5 (HZSM-5) complex catalyst (CuCeOx-H-C) was prepared through impregnation combined with pyrolysis and applied in the catalytic oxidation of 1,2-dichlorobenzene. The results indicate that the introduction of carboxyl groups on the surface of HZSM-5 is crucial for the formation of Ce-MOF/HZSM-COOH core–shell structure. This introduction facilitates the uniform deposition of CuCeOx on HZSM-5 and significantly enhances the overall acidity. Furthermore, the synergistic effect of Cu-Ce significantly enhanced the catalyst’s activity at low temperatures. Therefore, CuCeOx-H-C exhibited the highest activity, with a T90 of 236 °C. Additionally, the CuCeOx-H-C catalyst showed high selectivity for HCl and suppressed the generation of chlorinated by-products. The differences in catalyst activity among various catalysts arise from multiple factors, including specific surface area, dispersion of active species, oxygen mobility, oxygen storage capacity, redox properties, and others. Under the synergetic effects of above-mentioned factors, the activity of CuCeOx-H-C is remarkably enhanced and would be promising for potential industrial application.

Oxygen Vacancy Enabled Electronic Structure Engineering of Pt-WO3 Nanosheets toward Highly Efficient BTEX Sensing.

A Pt nanoparticle-immobilized WO3 material is a promising candidate for catalytic reactions, and the surface and electronic structure can strongly affect the performance. However, the effect of the intrinsic oxygen vacancy of WO3 on the d-band structure of Pt and the synergistic effect of Pt and the WO3 matrix on reaction performance are still ambiguous, which greatly hinders the design of advanced materials. Herein, Pt-decorated WO3 nanosheets with different electronic metal-support interactions are successfully prepared by finely tuning the oxygen vacancy structure of WO3 nanosheets. Notably, Pt-modified WO3 nanosheets annealed at 400 °C exhibit excellent benzene series (BTEX) sensing performance (S = 377.33, 365.21, 348.45, and 319.23 for 50 ppm ethylbenzene, benzene, toluene, and xylene, respectively, at 140 °C), fast response and recovery dynamics (10/7 s), excellent reliability (σ = 0.14), and sensing stability (φ = 0.08%). Detailed structural characterization and DFT results reveal that interfacial Ptδ+-Ov-W5+ sites are recognized as the active sites, and the oxygen vacancies of the WO3 matrix can significantly affect the d-band structure of Pt nanoparticles. Notably, Pt/WO3-400 with improved surface oxygen mobility and medium electronic metal-support interaction facilitates the activation and desorption of BTEX, which contributes to the highly efficient BTEX sensing performance. Our work provides a new insight for the design of high-performance surface reaction materials for advanced applications.

Promotion of Different Active Phases in MnOX-CeO2 Catalysts for Simultaneous NO Reduction and o-DCB Oxidation

AbstractMnOX-CeO2 catalysts with different Mn and Ce content were prepared to evaluate the effect of metal content on catalytic properties and activity in the simultaneous NO reduction and o-DCB oxidation, in order to elucidate the most active species for the process. Catalytic properties were evaluated by ICP-AES, XRD, skeletal FTIR, STEM-HAADF, XPS, N2-physisorption, H2-TPR, NH3-TPD and pyridine-FTIR. Catalysts with 85%Mn and 15%Ce molar content have been found to be the most active. Their excellent catalytic performance is related to the coexistence of Mn in different phases, i.e., Mn species strongly interacting with Ce and segregated Mn species. The effect of the preparation methods has also been deeply investigated: Co-precipitation method (CP) leads to Mn segregation as Mn2O3, whereas sol-gel preparation method (SG) promotes the formation of an amorphous powder. The synergy between segregated Mn2O3 species and Mn species in high interaction with Ce (resulting in a mixed oxide phase) leads to the presence of Mn with different oxidation states. This effect, together with the high oxygen mobility caused by structural defects, enhances redox, acidic and oxidative properties. The improvement of catalytic properties with Mn content also favors NO reduction side-reactions, with N2O and NO2 being the most important by-products, whereas it limits the production of chlorinated organic by-products in o-DCB oxidation.

Oxygen-deficient layered ε-MnO2 nanosheets derived from acid-etched La3Mn2O7 for robust adsorption-catalytic oxidation of toluene

Manganese dioxide (MnO2) stands out as a promising catalyst for toluene degradation yet refining its synthesis for optimal efficiency poses a significant challenge. In this study, we presented an up-bottom synthesis approach for ε-MnO2 by selectively removing inactive La ions from La3Mn2O7 (LLM) through acid etching, yielding stacked nanosheets with enriched oxygen vacancies. The resulting H2SO4-LLM catalyst exhibited efficient synergistic adsorption-catalytic oxidation effects, attributed to its exceptional specific surface area (307.0 m2/g) and abundant acidic sites, achieving almost 90 % removal of 2000 mg/m3 toluene (T90) at 196 ℃ and complete oxidation to CO2 at 205 °C at a space velocity of 18000 mL/(g·h), outperforming most state-of-the-art catalysts for toluene removal. The study elucidates the role of lattice oxygen in catalyzing toluene oxidation and reveals the intricate interplay between oxygen adsorption, lattice oxygen mobility, and redox capability, paving the way for the development of robust catalysts for environmental remediation.

Regulation of oxygen vacancies in MnCO3-based catalysts by thermally inducing for efficiently catalytic benzene combustion

Tuning oxygen vacancies through carbon pyrolysis is an effective strategy for fabricating high-performance catalysts to oxidize volatile organic compounds (VOCs). Herein, a series of MnCO3-based catalysts were synthesized by pyrolyzing MnCO3 precursors with different morphologies including dumbbell-like (D), bayberry-like (B) and cubic (C) structures for the benzene oxidation. The catalyst (D-300) derived from dumbbell-like MnCO3 exhibited superior catalytic performance for the benzene oxidation with a T90 of 176 °C and remarkable stability in long-term, cycling and water-resistance tests. Abundant oxygen vacancies in D-300 improved lattice oxygen mobility and redox ability, resulting in superior oxygen uptake and release capabilities. Moreover, oxygen vacancies greatly facilitated the activation and replenishment of gaseous oxygens to generate active oxygen species, thereby dramatically accelerating the cleavage of benzene rings and deep mineralization. In situ DRIFTS analysis demonstrated that benzene preferentially adsorbed onto D-300 due to its abundant acidic sites, and the oxidation of phenolate species was a rate-determining step. H2O may hinder the activation of gaseous oxygen, suppressing the activity of the catalyst.

Effect of transition metal (M=Cr, Mn, Fe, Co) doping on catalytic combustion of chlorobenzene over Ce − Y composite oxide

Transition metal (Cr, Mn, Fe, Co)-doped CeYOx catalysts were prepared by a co-precipitation method and applied for chlorobenzene elimination. Metal doping caused significant changes in physical properties and chemical environment of CeY solid solution. Intrinsic activity of metals and their interaction with CeY significantly improved the redox performance and oxygen mobility, thus enhancing the catalytic activity and chlorine poisoning resistance. The enhanced concentration and mobility of reactive oxygen can effectively control chlorinated by-products. MnCeYOx can achieve 90 % chlorobenzene conversion at 235 °C, attributing to the promotion of the redox dynamic cycle by the enhanced mobility of active oxygen.

On the Selection of Catalysts’ Support with High Oxygen Delivery Capacity for DRM Application: Interest of Praseodymium as Dopant of Ceria

AbstractIn the present work, a series of supports with varying compositions (ranging from pure CeO2 to pure PrO2-y) was designed to investigate their ability to release oxygen (with the concomitant formation of oxygen vacancies) under diverse reducing atmospheres: hydrogen (H2), helium (He), and in the presence of a carbonaceous substance that mimics eventual carbon deposits formed under practical reaction conditions (DRM). Oxygen vacancies were generated effectively in all three atmospheres (following the order He < H2 < carbon material). With regard to the influence of the composition, the capability to generate oxygen vacancies clearly increased with the Pr content, for whatever the conditions tested. Notably, the non-stoichiometry obtained with the support of pure praseodymia in both inert and reducing atmospheres is very remarkable, as it approaches the maximum non-stoichiometry value of the well-established theoretical Bevan cluster. This leads to consider this formulation as a very promising support for applications in catalysis and other fields where oxygen vacancies play a crucial role. Dry Reforming of Methane requires catalytic supports that possess highly mobile oxygen, enabling it to actively participate in the reactions step involved or potentially gasify undesirable carbon deposits generated during parallel reactions. Consequently, designing and elucidating the behavior of ceria-praseodymium-based supports with high reducibility and generation of oxygen vacancies (oxygen storage and release capacity) holds particular relevance in this context. Actually, the very preliminary results comparing two counterpart formulations (5%Ni/PrO2-y versus 5%Ni/Al2O3) already confirm the suitability of the choice of pure praseodymia in terms of activity, stability and very high selectivity towards H2 and CO, reaching a very close value to the ideal H2/CO ratio of 1.

Optimized preparation of La3Mn2O7 with superior lattice oxygen mobility and adsorbed oxygen utilization for catalytic removal of toluene

The R-P type layered perovskite La3Mn2O7 (LLM) is considered a more promising toluene oxidation catalyst than perovskite LaMnO3 (LMO) due to the versatile environment it provides for oxygen atoms, yet the challenge of realizing an optimal synthesis route remains. Herein, we revealed how calcination temperature influenced the structure–activity relationship and the mechanism by which the layered structure enhanced oxygen species reactivity. LLM700 possesses optimal toluene adsorption performance, oxygen species activation capability and low-temperature reducibility, thus exhibiting the highest catalytic activity (T90 = 283 °C) among single layered perovskite catalysts. The large interlayer gaps in the layered structure, combined with the weaker Mn-O bond strength near the layered structure, facilitate the easy removal of oxygen atoms, creating oxygen vacancies that act as pathways for oxygen ions to migrate within the lattice. Together, these factors enable the layered structure to enhance the mobility of lattice oxygen and the utilization of adsorbed oxygen, making LLM an ideal model for catalyzing the oxidation of toluene. Furthermore, the possible reaction pathway for the oxidation of toluene on LLM700 was inferred using GC–MS. This work paves the way for the catalytic applications of layered perovskites.

TYMS Knockdown Suppresses Cells Proliferation, Promotes Ferroptosis via Inhibits PI3K/Akt/mTOR Signaling Pathway Activation in Triple Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is characterized by a grim prognosis and numerous challenges. The objective of our study was to examine the role of thymidylate synthase (TYMS) in TNBC and its impact on ferroptosis. The expression of TYMS was analyzed in databases, along with its prognostic correlation. TYMS positive expression was identified through immunohistochemistry (IHC), while real-time quantitative PCR (qRTPCR) was employed to measure TYMS mRNA levels in various cell lines. Western blotting was utilized to assess protein expression. Cell proliferation, mobility, apoptosis, and reactive oxygen species (ROS) levels were evaluated using CCK8, wound scratch healing assay, transwell assay, and flow cytometry, respectively. Additionally, a tumor xenograft model was established in BALB/c nude mice for further investigation. Tumor volume and weight were measured, and histopathological analysis using hematoxylin and eosin (H&E) staining was conducted to assess tumor tissue changes. IHC staining was employed to detect the expression of Ki67 in tumor tissues. High expression of TYMS was observed in TNBC and was found to be correlated with poor prognosis in patients. Among various cell lines, TYMS expression was highest in BT549 cells. Knockdown of TYMS resulted in suppression of cell proliferation and mobility, as well as promotion of apoptosis. Furthermore, knockdown of TYMS led to increased accumulation of ROS and Fe2+ levels, along with upregulation of ACLS4 expression and downregulation of glutathione peroxidase 4 (GPX4) expression. In vivo studies showed that knockdown of TYMS inhibited tumor growth. Additionally, knockdown of TYMS was associated with inhibition of mTOR, p-PI3K, and p-Akt expression. Our research showed that the knockdown of TYMS suppressed the TNBC progression by inhibited cells proliferation via ferroptosis. Its underlying mechanism is related to the PI3K /Akt pathway. Our study provides a novel sight for the suppression effect of TYMS on TNBC.

Study on the Catalytic Activity Modification of Pr and Nd Doped Ce0.7Zr0.3O2 Catalysts for Simultaneous Removal of PM and NOX

Cerium-zirconium composite oxides (Ce0.7Zr0.3O2) have a remarkable effect on catalytic removal of carbon particles (PM) and nitrogen oxides (NOX) emitted from diesel engine, in order to further improve the thermal stability, oxygen storage capacity and low temperature catalytic REDOX performance of cerium zirconium composite oxides (Ce0.7Zr0.3O2), a small amount of Pr and Nd rare earth elements are doped to improve the catalytic activity of cerium zirconium composite oxides. In this paper, the composite oxide of Pr6O11–Nd2O3–CeO2–ZrO2 is prepared by unsteady co-precipitation method, and the physicochemical properties of the composite oxide catalyst are analyzed by BET, SEM, XRD and ICP. The gas adsorption capacity and catalytic activity of composite oxide catalysts are measured by temperature programmed reaction technology (TPR). The results show that the composite oxide of Pr0.05Nd0.05Ce0.6Zr0.3O2 prepared by using rare earth elements Pr and Nd inhibits the growth process of grain, refining the grain, and improving the sintering phenomenon at high temperature. The addition of Pr and Nd causes lattice defects, increases the number of oxygen vacancies, and improves the mobility of lattice oxygen, namely promotes oxide oxygen storage property, gas adsorption and catalytic oxidation reduction ability. After modification, Pr0.05Nd0.05Ce0.6Zr0.3O2 has good resistance to high temperature aging performance, prolongs the service life, reduces the PM lowest ignition temperature and minimum catalytic activity temperature of nitrogen oxide, and promotes the NOX reduction rate. For Pr0.05Nd0.05Ce0.6Zr0.3O2, the lowest ignition temperature of PM is about 150 °C, and the lowest catalytic activity temperature of NO is about 130 °C. The maximum CO2 production rate is 68.3%, and the maximum NO reduction rate is 45%.