Efficient Oxidation Catalysts Research Articles

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.

Highly Efficient Ce and Co Codoped OMS-2 Catalyst for NO Oxidation

Highly Efficient Ce and Co Codoped OMS-2 Catalyst for NO Oxidation

Hydrophobic modification of zeolite-supported platinum catalysts for complete oxidation of toluene

Zeolite-supported noble metal nanoparticles have been reported as active catalysts for complete oxidation of volatile organic compounds (VOCs) due to the combination of advantages of zeolite supports and noble metal species, where introducing more Al species (reduction of SiO2/Al2O3 ratios, SAR) and increasing hydrophobicity for zeolite supports are favorable for the complete oxidation of VOCs. Unfortunately, introduction of more Al species in the zeolite frameworks normally reduces the hydrophobicity of zeolite crystals. To overcome this problem, we rationally synthesize hydrophobic zeolites with low SAR by anchoring methyl group, exhibiting exceptionally catalytic performances in the complete oxidation of toluene at very low temperature (T90 at 144 °C) after loading Pt species (1 wt%). Characterizations of the catalysts show a vital role of hydrophobic zeolites for adsorption of more toluene and fast desorption of water. The strategy for preparation of hydrophobic zeolite-supported noble metal catalysts might offer an alternative way to develop highly efficient heterogeneous catalysts for the complete oxidation of VOCs in the future.

H2 production based on a ternary mixture of commercial CuO-NiO-TiO2 in a solar pilot plant

Glycerol is a by-product in biodiesel production (in the range of g·L−1), so its photoreforming by photocatalysis is a way of valorising it. TiO2 in photocatalysis has been widely studied, although its efficiency is limited by the high energy band gap, and the electron-hole recombination. Its combination with different semiconductors should improve charge separation, extending also the absorption from UV to visible light. Cu and Ni oxides are two of the most efficient low-cost transition metal oxide catalysts. Experiments were carried out in a 25 L pilot plant connected to a compound parabolic solar collector. Different combinations of the three semiconductors, based on the concentration of each metal on TiO2 (Me, 5%, 7.2% and 10%) were evaluated. Evonik P25-TiO2, CuO and NiO were combined by mechanical mixing. Hydrogen was quantified by a micro gas chromatograph, and copper and nickel leaching by ICP-MS. The best hydrogen production (0.060 mMol kJ−1) was attained with a proportion of 10:1 of TiO2:MeO, that corresponds to a total metal concentration of 7.2 wt%, being Cu and Ni in the same proportion. Metal content in solution increased as the reaction progressed, but Ni lixiviation of <0.012 mg L−1 was not significant. Significant Cu leaching (>1 mg L−1) was observed. This article presents novel results, in a solar pilot plant, for determining which ternary mixture can give better results, as well as metal leaching into water. Handling relevant volume of water in anoxic conditions can help to understand the application of this technology for the production of hydrogen.

Light-induced in-situ transformation from MOF to construct heterostructured Co3O4/Co catalyst for efficient photothermal catalytic oxidation

The construction of hybrid nanocatalysts with enhanced active surfaces/interfaces is crucial for the catalytic oxidative removal of volatile organic compounds (VOCs). In this study, we report an in-situ conversion approach to synthesize a heterostructured Co3O4/Co catalyst (Co@NC-0.5) for efficient photothermal catalytic oxidation of acetone. The catalysts were prepared by pyrolyzing a mixture of ZIF-67 and melamine. The exposed cobalt species underwent in-situ oxidation to form a Co3O4/Co heterostructure under photothermal conditions. This unique catalyst structure exhibited over 90 % conversion within 16 min under full solar spectrum irradiation and excellent reusability with continuous maintenance of 100 % acetone conversion rate after nine cycles performance tests. Notably, its specific mass activity under thermocatalytic conditions was 2.13 times higher than that of Co3O4. Our work provides a facile and effective strategy for developing highly active and durable non-precious metal catalysts suitable for various photothermal catalytic reactions.

Efficient activation of peroxymonosulfate for trichloroethylene degradation by cobalt ferrites anchored on CeO2 surfaces: Radical to non-radical pathway shift

This research investigates the unique configuration of cobalt ferrite (Co1.5Fe1.5O4) anchored onto the surface of cerium dioxide (CeO2), which effectively activates peroxymonosulfate (PMS) to degrade trichloroethylene (TCE). Co1.5Fe1.5O4-CeO2/PMS was able to completely degrade 5 mg/L of TCE by comparison between PMS and the components of the prepared composites. In addition, the Co1.5Fe1.5O4-CeO2/PMS system was highly adaptable to pH and aqueous substrates. Quenching experiments combined with ESR spectroscopy results demonstrated that ·OH, SO4·-, O2·-, and 1O2 in the system play an important role in degrading TCE. The Co1.5Fe1.5O4-CeO2/PMS system can maintain 90% degradation efficiency for various pollutants (TCE, carbon tetrachloride (CT), dichloromethane (DCM), 2,4-dichlorophenoxyacetic acid (2,4-D)) as well as the actual wastewater, and the multiple cycling experiments have verified that the Co1.5Fe1.5O4-CeO2/PMS has a good stability. XPS comparisons before and after the reaction revealed that cobalt ferrite exhibited a unique transition from the radical pathway to the non-radical pathway during TCE degradation after the introduction of CeO2. This pathway shift can be attributed to the synergistic interaction between cobalt ferrite and CeO2, which adjusts the electronic structure, facilitates the activation of PMS, and generates more reactive oxygen species to decompose TCE. This research offers valuable insights into the design of efficient advanced oxidation catalysts for the removal of organic pollutants from water and the optimization of degradation pathways.

Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides

Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides

Cobalt-nitrogen co-doped porous carbon sphere as highly efficient catalyst for liquid-phase cyclohexane oxidation with molecular oxygen and the active sites investigation

Cobalt-nitrogen co-doped porous carbon sphere as highly efficient catalyst for liquid-phase cyclohexane oxidation with molecular oxygen and the active sites investigation

Facet-dependent peroxymonosulfate activity and mechanism of CuO for degradation of organic pollutants

CuO is currently used as an effective activator for peroxymonosulfate (PMS), which exhibits complex radical, nonradical, or both activation pathways. However, there exists a knowledge gap concerning the relationship between CuO exposed facets and the PMS activation pathway, which should require further investigation. This study employed a simple and facile hydrothermal method to controllably prepare CuO samples with exposed {010} and {001} facets (referred to as CuO-010 and CuO-001, respectively). The main aim was to further study the facet-dependent PMS activation mechanism. The experimental results showed that the CuO-001 exhibited significantly higher activation efficiency than the CuO-010 due to the different surface atomic arrangement. Furthermore, scavenging experiments and EPR analyses revealed that CuO-010 exhibited both radical (SO4•− and •OH) and non-radical (1O2) pathways, synergistically degraded tetracycline (TC) and 4-nitrophenol (4-NP). Conversely, the CuO-001 displayed non-radical (1O2) and Cu(Ⅲ) intermediates, collaborating to oxidize the degradation of TC and 4-NP. More importantly, the generated 1O2 species and Cu(Ⅲ) intermediates exhibited a preference for reacting with amino or phenolic compounds containing electron-rich functional groups. Moreover, the CuO-001 also showed excellent resistance to anion interference, stability, and compatibility of a wide pH range. The outcomes of this study provide new insights into the comprehensiveness facet-dependent activation of PMS and the design of efficient metal oxide catalysts using the facet strategy for effective degradation of amino/phenolic pollutants in wastewater.

Regulating Au coverage for the direct oxidation of methane to methanol

The direct oxidation of methane to methanol under mild conditions is challenging owing to its inadequate activity and low selectivity. A key objective is improving the selective oxidation of the first carbon-hydrogen bond of methane, while inhibiting the oxidation of the remaining carbon-hydrogen bonds to ensure high yield and selectivity of methanol. Here we design ultrathin PdxAuy nanosheets and revealed a volcano-type relationship between the binding strength of hydroxyl radical on the catalyst surface and catalytic performance using experimental and density functional theory results. Our investigations indicate a trade-off relationship between the reaction-triggering and reaction-conversion steps in the reaction process. The optimized Pd3Au1 nanosheets exhibits a methanol production rate of 147.8 millimoles per gram of Pd per hour, with a selectivity of 98% at 70 °C, representing one of the most efficient catalysts for the direct oxidation of methane to methanol.

Anchoring of Copper(II)-Schiff Base Complex in SBA-15 Matrix as Efficient Oxidation and Biomimetic Catalyst.

A new mononuclear Cu(II) complex [Cu(L2)(H2O)2], where L is the Schiff base 2-[2-(3-bromopropoxy)benzylideneamino] benzoic acid, was synthesized and covalently anchored onto an amino-functionalized SBA-15 mesoporous silica in order to obtain an efficient heterogeneous catalyst. The elemental, structural, textural and morphological characterization confirmed the coordination of the central Cu(II) ion with two ligands and two H2O molecules in the synthesized complex and its successful immobilization into the inner pore surface of the NH2-functionalized support without the loss of the mesoporous structure. The catalytic activity of the free or immobilized Cu(II) complex was tested in the oxidation of cyclohexene with H2O2 under an air atmosphere and the dismutation reaction of the superoxide radical anions with very good results. In addition, catalyst reuse tests claim its suitability in alkene oxidation processes or as a biomimetic catalyst.

Unraveling FeOx Nanoparticles Confined on Fibrous Mesoporous Silica Catalyst Construction and CO Catalytic Oxidation Performance

Catalytic oxidation is used to control carbon monoxide (CO) emissions from industrial exhaust. In this study, a mesoporous silica material, KCC-1, was synthesized and used as a carrier with a high specific surface area to confine active component FeOx nanoparticles (NPs), and the CO catalytic oxidation performance of x%Fe@KCC-1 catalysts (x represents the mass loading of Fe) was studied. The experimental results showed that due to its large specific surface area and abundant mesopores, the FeOx NPs were highly dispersed on the surface of the KCC-1 carrier. The particle size of FeOx was very small, resulting in strong interactions between FeOx NPs and KCC-1, which enhanced the catalytic oxidation reaction on the catalyst. The FeOx loading improved the CO adsorption capability of the catalyst, which facilitated the catalytic oxidation of CO, with the 7%Fe@KCC-1 catalyst achieving 100% CO conversion at 160 °C. The CO catalytic removal mechanism was investigated by a combination of in-situ DRIFTS and DFT calculations. This study advances scientific understanding of the application potential of nano-catalysts in important oxidation reactions and provides valuable insights into the development of efficient CO oxidation catalysts.

Construction of Pd/Mn3O4 heterojunction catalyst for efficient photothermal synergetic catalytic propane total oxidation

Photothermal synergistic low-temperature catalytic volatile organic compounds (VOCs) degradation has an advantage on energy efficiency and reduction of carbon emissions. Herein, an impregnation-pyrolysis-oxidation strategy was adopted to synthesize Pd/Mn3O4 heterojunction catalyst. Under photothermal synergistic conditions, 0.60Pd/Mn3O4 catalyst exhibited an excellent activity for propane total oxidation, with a T90 value of 219.1 ℃, which was 115.3 ℃ lower than that of Mn3O4. Enhancement effect of the heterojunction structure on photothermal synergy was detected by various characterization techniques and density functional theory calculation. The presence of Pd species enhanced the low-temperature reducibility of Mn3O4. Meanwhile, O2 molecules were more easily activated at the Pd sites and overflow to the surface of Mn3O4 for reaction. Besides, the formation of p-n junction between Pd species and Mn3O4 in heterojunction structure promoted the charge separation and the migration of carriers, and boosted the generation of oxygen free radical, resulting in a significant improvement in photothermal catalytic activity. Overall, this study provided new strategy and deep insight for constructing heterojunction to enhance photothermal catalytic performance of VOC elimination.

2D surfaces twisted to enhance electron freedom toward efficient advanced oxidation processes

Two-dimensional (2D)-interface engineering for designing effective electron-rich catalyst center is pivotal in manipulating the catalytic behaviors and activity, but still challenging. Here, we’ve successfully twisted the surfaces of the 2D layered FeOCl, fulfilling the targeted fine-tuning of its Fe sites. The obtained new catalyst can boost peroxymonosulfate activation for reactive species with much lower energy barriers and efficiently oxidized target organic with almost 41 orders of magnitude faster reaction kinetics than pristine FeOCl. The increased degree of freedom of electron around Fe site has been identified as the key driver. The distorted geometry structure around Fe has led to an increased polarization of charge distribution, associating with less symmetric electron valence cloud and higher electron mobility. Thus, the twisted surfaces enable a much enhanced interfacial charge transfer between Fe site and the electron-deficient peroxymonosulfate. This work highlights the concept of twisted surface construction toward efficient advanced oxidation catalyst design.

Chitosan –NH2 derived efficient Co3O4 catalyst for styrene catalytic oxidation: Simultaneously regulating particle size and Co valence

In this study, a Co3O4 catalyst is synthesised using the chitosan-assisted sol–gel method, which simultaneously regulates the grain size, Co valence and surface acidity of the catalyst through a chitosan functional group. The complexation of the free –NH2 complex inhibits particle agglomeration; thus, the average particle size of the catalyst decreases from 82 to 31 nm. Concurrently, Raman spectroscopy, hydrogen temperature-programmed reduction, electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy experiments demonstrate that doping with chitosan N sources effectively modulates Co2+ to promote the formation of oxygen vacancies. In addition, water washing after catalyst preparation can considerably improve the low-temperature (below 250 °C) activity of the catalyst and eliminate the side effects of alkali metal on catalyst activity. Moreover, the presence of Brønsted and Lewis acid sites promotes the adsorption of C8H8. Consequently, CS/Co3O4-W presents the highest catalytic oxidation activity for C8H8 at low temperatures (R250 °C = 8.33 μmol g−1 s−1, WHSV = 120,000 mL hr−1∙g−1). In situ DRIFTS and 18O2 isotope experiments demonstrate that the oxidation of the C8H8 reaction is primarily dominated by the Mars–van Krevelen mechanism. Furthermore, CS/Co3O4-W exhibits superior water resistance (1- and 2- vol% H2O), which has the potential to be implemented in industrial applications.

Unveiling the mechanism of thermal catalytic oxidation of HCHO from the kiln exhaust gas using Sc-decorated Cr2CO2-MXenes

Sc/Cr2CO2 is a novel efficient thermal catalyst for HCHO oxidation.

A phosphorus-doped carbon material derived from a sodium alginate/phosphoric acid hydrogel as an efficient catalyst for catalytic oxidation of furfural to maleic acid

A phosphorus-doped carbon material (PC-700) with high content of P was derived through the calcination of the alginate-H3PO4 xerogel. PC-700 exhibited excellent catalytic activity for the production of maleic acid from furfural in aqueous solution.

Optimization of 5-hydroxymethylfurfural oxidation via photo-enzymatic cascade process

Trametes versicolor's laccase (LacTV) was efficient catalyst in HMF oxidation to FDCA. Its use in an enzymatic and photocatalytic cascade process permitted a 40-fold increase in FDCA productivity compared to traditional enzymatic batch systems.

A soft molecular single-source precursor approach to synthesize a nanostructured Co9S8 (pre)catalyst for efficient water oxidation and biomass valorization

A nanocrystalline Co9S8 (pre)catalyst derived from a novel {CoIIS4} complex is reported for the oxygen evolution reaction (OER) and selective biomass valorization. During OER, Co9S8 reconstructs completely into a CoOOH active phase via S-leaching.

Ru nanoclusters supported on a bimodal N,S-doped mesoporous carbon: an efficient and reusable catalyst for selective aerobic oxidation of alcohols and amines

Ru nanoparticles supported on a bimodal N, S-doped mesoporous carbon catalyzing the oxidation of various alcohols and amines, giving the respective aldehydes/ketones and nitriles/imines in high yields and selectivity.