Efficient Catalytic Oxidation Research Articles

Efficient Visible‐Light‐Driven Aromatic Alcohol Oxidation Using PI‐TiO2 Composite Photocatalyst

AbstractSynthesizing fine chemicals and valuable pharmaceutical intermediates through selective catalytic oxidation of alcohols is indispensable and crucial. However, the conventional methods of alcohol oxidation have inevitable drawbacks, including harsh reaction conditions and environmental pollution. Thus, it is imperative to develop efficient catalytic oxidation systems for alcohols. Herein, we successfully synthesized a 15 wt %PI‐TiO2 composite by a one‐step solid‐state heating polymerization technique. This catalyst exhibits excellent responsiveness to visible light and demonstrates remarkable catalytic activity. Furthermore, TEMPO was introduced as a cocatalyst to construct a PI‐TiO2/TEMPO/O2 system for the catalytic oxidation of alcohols. In comparison to the individual effects of PI or TiO2, this system showcases improved catalytic activity and broader substrate applicability. As a result, the conversion efficiency of benzyl alcohol increases by 3.44 times and 2.26 times, respectively. This research not only introduces a novel approach for preparing visible light‐active PI‐TiO2 catalysts but also indicates the significance of establishing an efficient electron transfer process in alcohol catalytic oxidation.

Synthesis, Characterization, and Application of a Polyoxometalates‐Based CuII Complex for Efficient Catalytic Oxidation and Electrochemical Detection

AbstractThe development of eco‐friendly, high‐efficiency polyoxometalates (POMs) catalysts is vital for advancing catalytic oxidation and electrochemical detection in environmental protection. Herein, a POM‐based CuII‐containing complex with the molecular formula [H(4‐AP)]8[Cu2(H2O)4(P2Mo5O23)2]·8H2O (1) (4‐AP = 4‐aminopyridine) is synthesized using the hydrothermal method, and the crystal structure is determined by single X‐ray diffraction (SXRD), infrared (IR) spectroscopy, and powder X‐ray diffraction (PXRD). Structurally, complex 1 exhibits a one dimension (1D) chain arrangement, composed of CuII ions and Strandberg‐type (P2Mo5O23)6− anionic clusters. These 1D chains are further interconnected through [H(4‐AP)]+ ligands, resulting in the formation of a two dimension (2D) supramolecular network. Complex 1 serves as an outstanding heterogeneous catalyst for the oxidation of methyl phenyl sulfide (MPS), demonstrating a remarkable conversion rate of 99% for MPS and a selectivity of 98% toward methyl phenyl sulfoxide (MPSO). In addition to its catalytic capabilities, complex 1 is also employed in the electrochemical detection of FeIII and CrVI ions, with low limits of detection (LODs) at 4.92 µm for FeIII and 7.82 µM for CrVI.

Efficient catalytic oxidation of formaldehyde by defective g–C3N4–anchored single-atom Pt: A DFT study

Indoor volatile formaldehyde is a serious health hazard. The development of low-temperature and efficient nonhomogeneous oxidation catalysts is crucial for protecting human health and the environment but is also quite challenging. Single-atom catalysts (SACs) with active centers and coordination environments that are precisely tunable at the atomic level exhibit excellent catalytic activity in many catalytic fields. Among two-dimensional materials, the nonmagnetic monolayer material g-C3N4 may be a good platform for loading single atoms. In this study, the effect of nitrogen defect formation on the charge distribution of g-C3N4 is discussed in detail using density functional theory (DFT) calculations. The effect of nitrogen defects on the activated molecular oxygen of Pt/C3N4 was systematically revealed by DFT calculations in combination with molecular orbital theory. Two typical reaction mechanisms for the catalytic oxidation of formaldehyde were proposed based on the Eley-Rideal (E-R) mechanism. Pt/C3N4–V3N was more advantageous for path 1, as determined by the activation energy barrier of the rate-determining step and product desorption. Finally, the active centers and chemical structures of Pt/C3N4 and Pt/C3N4–V3N were verified to have good stability at 375 K by determination of the migration energy barriers and ab initio molecular dynamics simulations. Therefore, the formation of N defects can effectively anchor single-atom Pt and provide additional active sites, which in turn activate molecular oxygen to efficiently catalyze the oxidation of formaldehyde. This study provides a better understanding of the mechanism of formaldehyde oxidation by single-atom Pt catalysts and a new idea for the development of Pt as well as other metal-based single-atom oxidation catalysts.

Regulating surface properties of Co3O4@MnO2 catalysts through Co3O4-MnO2 interfacial effects for efficient toluene catalytic oxidation

Interface engineering between Co3O4 and MnO2 shows distinct advantages in regulating the surface properties of catalysts. However, there is still doubt about whether the interfacial effects originate from the interaction between heterogeneous metals and Co3+ or Co2+. Herein, Co3O4-MnO2 interface was successfully constructed on Co3O4 primarily exposed different crystal planes to design Co ions that were directly linked to MnO2 at Co3O4-MnO2 interface. Combining the results of systematic characterizations and catalytic performance evaluation, it is found that the oxidative decomposition of toluene over Co3O4@MnO2 catalysts is significantly accelerated in comparison with the pristine Co3O4, which can be attributed to the greatly increased Co3+ and adsorbed oxygen species as well as specific surface area after the successful construction of Co3O4-MnO2 heterointerface. However, Co3O4-MnO2 interface shows much greater influence on Co3O4@MnO2-100 where Co ions mainly exist in the form of Co2+ than that on Co3O4@MnO2-110 dominated by Co3+. Furthermore, catalytic performance evaluation results illustrate that the T90 of Co3O4@MnO2-110 has only decreased by 11 °C compared to Co3O4-110, while the T90 of Co3O4@MnO2-100 is 50 °C lower than that of Co3O4-100. Therefore, based on the above results it speculates that the strong interaction between MnO2 and Co3O4 at Co3O4-MnO2 hetero-interface may originate more from the synergistic effect between MnO2 species and Co2+ ions. In addition, the in-situ DRIFTS demonstrate that the oxidation of toluene over Co3O4@MnO2 catalysts follows the path of toluene → benzaldehyde → benzoate → maleic anhydride → water and carbon dioxide.

Highly Dispersed Ni Atoms and O3 Promote Room-Temperature Catalytic Oxidation.

Transition metal oxides are promising catalysts for catalytic oxidation reactions but are hampered by low room-temperature activities. Such low activities are normally caused by sparse reactive sites and insufficient capacity for molecular oxygen (O2) activation. Here, we present a dual-stimulation strategy to tackle these two issues. Specifically, we import highly dispersed nickel (Ni) atoms onto MnO2 to enrich its oxygen vacancies (reactive sites). Then, we use molecular ozone (O3) with a lower activation energy as an oxidant instead of molecular O2. With such dual stimulations, the constructed O3-Ni/MnO2 catalytic system shows boosted room-temperature activity for toluene oxidation with a toluene conversion of up to 98%, compared with the O3-MnO2 (Ni-free) system with only 50% conversion and the inactive O2-Ni/MnO2 (O3-free) system. This leap realizes efficient room-temperature catalytic oxidation of transition metal oxides, which is constantly pursued but has always been difficult to truly achieve.

A colorimetric sensor for rapid discrimination of tea polyphenols and tea authentication based on Rh-decorated Pd nanocubes with high peroxidase-like activity

The rapid development of nanozymes has offered substantial opportunities for the fields of biomedicine, chemical sensing, and food safety. Among these applications, multichannel sensors, with the capability of simultaneously detecting multiple target analytes, hold promise for the practical application of nanozymes in chemical sensing with high detection efficiency. In this study, Rh-decorated Pd nanocubes (Pd–Rh nanocubes) with significantly enhanced peroxidase-like activity are synthesized through the mediation of underpotential deposition (UPD) and subsequently employed to develop a multichannel colorimetric sensor for discriminating tea polyphenols (TPs) and tea authentication. Based on a single reactive unit of efficient catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine dihydrochloride (TMB), the nanozyme-based multichannel colorimetric sensor responds to each analyte in as short as 1 min. With the aid of principal component analysis (PCA) and hierarchical cluster analysis (HCA), various TPs and types of tea can be accurately identified. This work not only provides a new type of simply structured and highly active nanozymes but also develops a concise and rapid multichannel sensor for practical application in tea authentication and quality inspection.

Deep understanding the formation of MnCoOx in-situ grown on foam nickel towards efficient lean methane catalytic oxidation

Methane is the second largest greenhouse gas in the world, with a stronger greenhouse effect than carbon dioxide. The efficient elimination of methane in the atmosphere has important engineering significance in slowing down global temperature rise, energy resource utilization, collaborative control of pollutants, and promoting technological innovation. In this work, a general hydrothermal synthesis method was introduced to in-situ construct four different morphologies of MnCoOx (including rod-, spherical-, filamentous- and bulk-shape) on foam nickel (NF). The synthesis of MnCoOx/NF with different morphologies was due to changes in NF pretreatment conditions and precipitants, which affected the nucleation and growth rates of MnCoOx, ultimately resulting in different morphologies. When the four different morphologies of MnCoOx/NF were used as catalysts for lean methane catalytic oxidation, MnCoOx/NF-r exhibited the best excellent catalytic activity, and the T90 occurred at 428 °C in space velocity of 48,000 mL g−1 h−1. Such an outstanding performance was attributed to the unique properties of the MnCoOx/NF-r including the larger surface area and more oxygen vacancies for providing more active sites and a higher oxygen migration rate, which was very beneficial for improving the catalytic oxidation performance of methane.

Four-channel catalytic micro-reactor based on alumina hollow fiber membrane for efficient catalytic oxidation of CO

The traditional automotive catalytic converter using commercial ceramic honeycomb carriers has many problems such as high back pressure, low engine efficiency, and high usage of precious metals. This study proposes a four-channel catalytic micro-reactor based on alumina hollow fiber membrane, which uses phase inversion method for structural molding and regulation. Due to the advantages of its carrier, it can achieve lower ignition temperature under low noble metal loading. With Pd/CeO2 at a loading rate of 2.3% (mass), the result showed that the reaction ignition temperature is even less than 160 °C, which is more than 90 °C lower than the data of commercial ceramic substrates under similar catalyst loading and airspeed conditions. The technology in turn significantly reduces the energy consumption of the reaction. And stability tests were conducted under constant conditions for 1000 hours, which proved that this catalytic converter has high catalytic efficiency and stability, providing prospects for the design of innovative catalytic converters in the future.

Highly enhanced direct catalytic oxidation of cyclohexane to adipic acid by prussian blue analogues-derived C, N doped CuCo composite catalysts

The oxidation of cyclohexane to produce adipic acid suffered from the inefficient and polluting two-step process. We introduce the CuCo Prussian blue analogues derived in situ C, N doped CuCo composite catalysts in the selective oxidation of cyclohexane. Due to the in-situ doping of C and N elements in the form of active graphite carbon and pyridine nitrogen, the oxygen vacancy content and the ability to activate oxygen are improved. The one-step efficient catalytic oxidation of cyclohexane to adipic acid was realized due to the excellent electron transfer performance between C, N elements and metals.

Preparation of MnO2@MPIA catalysts with a controlled oxygen vacancy for the efficient catalytic oxidation of formaldehyde at room temperature

δ-MnO2 catalysts have attracted much attention because of the abundance of oxygen vacancies (OVs) on the surface to achieve efficient catalytic oxidation of volatile organic compounds (VOCs) such as formaldehyde (HCHO). However, the recycling and regeneration of powdered δ-MnO2 nano-catalysts still limits the practical application of the catalysts. Here, the surface of aramid fiber (MPIA) was treated by corona activation to introduce reactive groups, such as -OH, and -COOH. These reactive groups can promote the exposure of more Mn3+ on the surface of loaded δ-MnO2 to produce OVs. Meanwhile, the strong interactions between the activated MPAI and δ-MnO2 was formed, which helped to improve the stability and cyclic regeneration of the fiber-based δ-MnO2 catalysts. The effects of Mn3+ and OVs on the catalytic performance of δ-MnO2 were targeted and characterized by SEM, XPS and BET. The pathways of HCHO removal by OVs on the δ-MnO2 surface and the relative free energies of the corresponding intermediates were also explored. The results revealed that optimizing the morphology of MPIA surface-loaded δ-MnO2 can obtain a higher concentration of oxygen vacancies, with excellent HCHO removal efficiency at room temperature and high catalytic activity even after multiple cycle regeneration.

Density functional theory-based screening of Ti4C3O2-loaded single atoms for efficient selective catalytic oxidation of formaldehyde

Indoor formaldehyde (HCHO) pollution poses a major risk to human health. Low-temperature catalytic oxidation is an effective method for HCHO removal. The high activity and selectivity of single atomic catalysts provide a possibility for the development of efficient non-precious metal catalysts. In this study, the most stable single-atom catalyst Ti–Ti4C3O2 was screened by density functional theory among many single atomic catalysts with two-dimensional (2D) monolayer Ti4C3O2 as the support. The computational results show that Ti–Ti4C3O2 is highly selective to HCHO and O2 in complex environments. The HCHO oxidation reaction pathways are proposed based on the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. According to the reaction energy and energy span models, the E-R mechanism has a lower maximum energy barrier and higher catalytic efficiency than the L-H mechanism. In addition, the stability of the Ti–Ti4C3O2 structure and active center was verified by diffusion energy barrier and ab initio molecular dynamics simulations. The above results indicate that Ti–Ti4C3O2 is a promising non-precious metal catalyst. The present study provides detailed theoretical insights into the catalytic oxidation of HCHO by Ti–Ti4C3O2, as well as an idea for the development of efficient non-precious metal catalysts based on 2D materials.

Highly efficient catalytic oxidation of toluene by amorphous/microcrystalline mixed-phase MnO2

Amorphous transition metal oxides exhibit considerable potential in the catalytic oxidation of volatile organic compounds (VOCs) owing to their distinctive surface properties. In this study, we achieved the modulation of the crystalline structure of manganese oxides by employing various C3 alcohols (alcohols with three carbons) with distinct hydroxyl types during the reduction process with potassium permanganate. Subsequently, a series of characterization techniques were employed to assess the catalytic performance of the prepared MnO2 in the oxidation of toluene. Notably, the MnO2-G obtained from glycerol presented excellent catalytic activity (T90 = 219 °C), stability, and water resistance. The unique amorphous/microcrystalline state of MnO2-G exposed more phase boundaries, and the unsaturated coordination structure facilitated the generation of additional defective sites, favoring the adsorption and activation of oxygen. Furthermore, the mixed-crystalline state induced the elevated Mn3+ content on the surface of MnO2-G, leading to elongation of the Mn-O bond due to the pronounced Jahn-Teller effect of Mn3+. Consequently, the synergistic effects of the mixed crystalline state contributed to the efficient catalytic oxidation of toluene at relatively low temperatures. Additionally, the conversion pathway of toluene on MnO2-G was further revealed by in situ DRIFTS.

Zeolitic imidazolate framework@hydrogen titanate nanotubes for efficient adsorption and catalytic oxidation of organic dyes and microplastics

Metal-organic frameworks (MOFs) have significant promise as materials for many environmental applications, namely in the realm of water treatment. In this study, we produced a nanocomposite material by combining zeolitic imidazolate frameworks (ZIF-67) with hydrogen titanate nanotubes (HTNT) at ambient temperature. The materials, namely HTNT, ZIF-67, and HTNT@ZIF-67, were analyzed and employed for the adsorption and catalytic oxidation of water pollutants such as organic dyes (fluorescein acid (FL), Rhodamine B (RhB), direct blue I (DB), and basic fuchsin (BF)) and microplastics extracted from personal care and cosmetics products. The HTNT@ZIF-67 nanocomposite exhibited dye removal efficiencies of 99% and 97% for adsorption and catalytic oxidation by hydrogen peroxide (H2O2), respectively. ZIF-67 exhibits the most rapid disintegration rate among the tested substances, with rates of 517, 439, 1764, 1764, and 1621 mL/min·g for H2O2 and H2O2 in the presence of FL, RhB, DB, and BF, respectively. The catalytic degradation process may be used for up to six cycles, while maintaining an efficiency of 78%. Catalysts based on ZIF-67, such as HTNT@ZIF-67, show great potential for removal targeting organic contaminants such dyes and microplastics.

Synthesis of Mo-Ta bimetallic oxide catalyst with crystal phase regulation strategy for efficient catalytic oxidation of 4,6-DMDBT in diesel

Oxidative desulfurization (ODS) technology mainly involves selectively oxidizing sulfides in diesel fuel into sulfone utilizing highly efficient catalysts to prepare clean fuel, especially using molecular oxygen as an oxidant. Bimetallic oxide is a feasible catalyst for the ODS process owing to its superior catalytic activity. Herein, a series of molybdenum-tantalum bimetallic oxide catalysts (MoTaOx) with different crystalline phases were successfully fabricated by co-precipitation combined with calcinating at different temperatures. The characterization experimental results manifested that the calcination temperature observably affected the formation of crystalline phase of MoTaOx as well as the catalytic activity. Meanwhile, the activity tests demonstrated that the MoTaOx-750 catalyst exhibited outstanding sulfur removal efficiency on 4,6-DMDBT in ODS system, achieving ultra-deep desulfurization (100 %) within 9 h at 120 °C. The excellent oxidative desulfurization activity was attributed to the synergistic effect of Mo-Ta bimetal exposing more active centers. Finally, a possible reaction mechanism was proposed and the obtained catalyst showed a long-life utilization without deteriorating rather noticeably in catalytic activity after 26 cycles.

ZIF-67-derived Co@NC as an efficient catalyst for magnesium sulfite oxidation in the flue gas desulfurization process

Magnesium desulfurization is a wet flue gas desulfurization (WFGD) technology widely used in China, however, the low oxidation rate of magnesium sulfite (MgSO3), a byproduct of WFGD, causes the subsequent oxidation and crystallization process to require amount energy. Here, we prepared a cobalt-based nitrogen-doped porous carbon catalyst (Co@NC) using ZIF-67 as a precursor for the efficient catalytic oxidation of MgSO3 generated during magnesium desulfurization. The performance of Co@NC catalysts obtained at an optimal calcination temperature of 650 °C showed that the catalysts with oxidation rates up to 0.1332 mmol·L−1·s−1 of MgSO3 were considerably better than those previously studied, which outperformed the catalysts described in earlier research by a considerable margin. Further studies revealed that the Co@NC’s exceptional catalytic activity was attributed to both its special porous structure and the exposed active Co sites in the organic skeleton. The uniformly dispersed Co species act as the active sites of the Co@NC that can be fully contacted with the reactant. The presence of 0.5 g·L−1 Co@NC increases the MgSO3 oxidation rate by about 14 times compared to the noncatalytic benchmark. A practical tactic is furnished by this research for energy saving and emission reduction in the WFGD process, especially for the efficient oxidation and resource conversion of the by-product MgSO3.

Efficient Photothermal Catalytic Oxidation Enabled by Three-Dimensional Nanochannel Substrates.

Photothermal catalysis exhibits promising prospects to overcome the shortcomings of high-energy consumption of traditional thermal catalysis and the low efficiency of photocatalysis. However, there is still a challenge to develop catalysts with outstanding light absorption capability and photothermal conversion efficiency for the degradation of atmospheric pollutants. Herein, we introduced the Co3O4 layer and Pt nanoclusters into the three-dimensional (3D) porous membrane through the atomic layer deposition (ALD) technique, leading to a Pt/Co3O4/AAO monolithic catalyst. The 3D ordered nanochannel structure can significantly enhance the solar absorption capacity through the light-trapping effect. Therefore, the embedded Pt/Co3O4 catalyst can be rapidly heated and the O2 adsorbed on the Pt clusters can be activated to generate sufficient O2- species, exhibiting outstanding activity for the diverse VOCs (toluene, acetone, and formaldehyde) degradation. Optical characterization and simulation calculation confirmed that Pt/Co3O4/AAO exhibited state-of-the-art light absorption and a notable localized surface plasmon resonance (LSPR) effect. In situ diffuse reflectance infrared Fourier transform spectrometry (in situ DRIFTS) studies demonstrated that light irradiation can accelerate the conversion of intermediates during toluene and acetone oxidation, thereby inhibiting byproduct accumulation. Our finding extends the application of AAO's optical properties in photothermal catalytic degradation of air pollutants.

Electron-rich ruthenium nanoparticles on nitrogen-doped carbon for the efficient catalytic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid

Modulating the electronic structure of metal nanoparticles (NPs) demonstrates to be useful for the optimization of the catalytic performance. Herein, electron-sufficient ruthenium NPs were successfully constructed on a nitrogen-doped carbon support (Rux-NC), which displayed excellent catalytic activity for the oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). Especially, a high FDCA yield of 97% was implemented over Ru2.0/NC catalyst in water. The FDCA productivity in this case is also as high as 4.8 molFDCA‧molRu−1‧h−1, which value exceeds most of the previous reported Ru-based catalysts for the production of FDCA. It has been disclosed that the Ru2.0/NC was endowed with high N content and abundant electron-rich Ru0 NPs evoked by the electronic interactions between the NC support the Ru NPs. These facts greatly contribute to the activation of O2, and accelerate the oxidation both of the hydroxymethyl and aldehyde groups of HMF to the carboxyl one. This work provides new understanding for the development of effective Ru-based catalysts for the catalytic oxidation reactions by the electronic structure regulation strategy.

Catalytic wet peroxide oxidation of organic dye with in-situ generated H2O2 over bifunctional Fe-Pt@Pd/SiO2 catalyst prepared by double-metal complex salt approach

While the Fenton reaction is efficient in wastewater treatment, the intrinsic problem of the dosage-dependent process poses another burden on ecosystem. Herein, we propose a highly efficient and environmentally-benign catalytic wet peroxide oxidation (CWPO) of methyl orange (MO) using in-situ generated H2O2 from hydrogen and air instead of ready-made H2O2. Pt@Pd/SiO2 and Pd@Pt/SiO2 catalysts were prepared by double-metal complex salt approach, and they were combined with soluble Fe salt (CWPO-I) or impregnated Fe (CWPO-II). The MO degradation rate of Pt@Pd/SiO2 for CWPO-I was 2.5 times faster than that of the conventional PdPt/SiO2. This can be rationalized in terms of Pd-enriched surface with strong interaction between Pt and Pd. Moreover, bifunctional Fe-Pt@Pd/SiO2 catalyst demonstrated outstanding activity in promoting CWPO-II with in-situ generated H2O2, even outperforming its counterpart with ready-made H2O2. This new approach offers an efficient water remediation method free from addition and generation of any undesirable chemicals affecting environment.

Development of Molybdenum oxide Promoted CeO2−SiO2 Mixed‐oxide Catalyst for Efficient Catalytic Oxidation of Benzylamine to N‐Benzylidenebenzylamine

AbstractThis study explores a rational synthesis of a molybdenum‐promoted Ce−Si mixed oxide catalyst (MoO3/CeO2−SiO2) to regulate synergies between MoO3 and SiO2 dopant on CeO2, achieving high selectivity in solvent‐free catalytic oxidative coupling of amines to imines using molecular O2 as the oxidant. Comparative efficiency tests were conducted with bare CeO2, CeO2−SiO2, and MoO3/CeO2 catalysts. Characterization techniques, including XRD, Raman spectroscopy, N2‐adsorption‐desorption analysis, FTIR, NH3−TPD, TEM, and XPS, were employed to assess textural properties, acidic features, promoter and dopant dispersion in CeO2 lattice, and oxygen defects. Mo/Ce−Si catalyst exhibited superior acidic sites and a higher concentration of Ce3+ ions (Iu/ITotal), indicating increased oxygen vacancies. This catalyst demonstrated exceptional performance in the oxidative coupling of benzylamine, providing higher conversion and selectivity to the corresponding imine. Remarkably, the Mo/Ce−Si catalyst maintained consistent performance over five recycling runs. The catalyst also proved effective for the selective oxidative coupling of various amine substrates with diverse steric and electronic properties. Experimental results confirmed a plausible reaction mechanism within the concise catalyst design.

A novel square-shaped Zr-substituted polyoxotungstate for the efficient catalytic oxidation of sulfide to sulfone

A novel square-shaped Zr-substituted polyoxotungstate for the efficient catalytic oxidation of sulfide to sulfone