Efficient Catalytic Oxidation Research Articles

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.

Immobilised Ruthenium Complexes for the Electrooxidation of 5-Hydroxymethylfurfural.

Abundantly available biomass-based platform chemicals, including 5-hydroxymethylfurfural (HMF), are essential stepping stones in steering the chemical industry away from fossil fuels. The efficient catalytic oxidation of HMF to its diacid derivative, 2,5-furandicarboxylic acid (FDCA), is a promising research area with potential applications in the polymer industry. Currently, the most encouraging approaches are based on solid-state catalysts and are often conducted in basic aqueous media, conditions where HMF oxidation competes with its decomposition. Efficient molecular catalysts are practically unknown for this reaction. In this study, we report on the synthesis and electrocatalysis of surface-bound molecular ruthenium complexes for the transformation of HMF to FDCA under acidic conditions. Catalyst immobilisation on mesoporous indium tin oxide electrodes is achieved through the incorporation of phosphonic acid anchoring groups. Screening experiments with HMF and further reaction intermediates revealed the catalytic route and bottlenecks in the catalytic synthesis of FDCA. Utilising these immobilised electrocatalysts, FDCA yields of up to 85 % and faradaic efficiencies of 91 % were achieved, without any indication of substrate decomposition. Surface analysis by X-ray photoelectron spectroscopy (XPS) post-electrocatalysis unveiled the desorption of the catalyst from the electrode surface as a limiting factor in terms of catalytic performance.

Efficient Catalytic Oxidation of Ethylene at 0 °C on an in Situ Carbon Modified Pt Catalyst Supported on SBA-15.

The design of efficient catalysts for catalytic ethylene (C2H4) oxidation is of crucial importance for extending the shelf life of fruits and vegetables. Herein, a carbon modified SBA-15 supported Pt catalyst (Pt/CSBA-15) was prepared in situ by a facile solid phase grinding-infiltration-inert atmosphere calcination method. Characterization results reveal that in the Pt/CSBA-15 catalysts thin carbon layers are successfully formed in the hexagonal pores of SBA-15. Additionally, Pt particles are well dispersed in the channels of SBA-15, and Pt/CSBA-15 has a smaller Pt particle size than the catalyst without carbon modification (i.e., Pt/SBA-15). O2 is more feasibly adsorbed and activated on small-sized Pt particles, and in situ formed carbon species enhance the hydrophobicity of catalysts. As a result, both 3Pt/CSBA-15 and 5Pt/CSBA-15 are able to maintain 100% conversion of 50 ppm of C2H4 for more than 7 h at 0 °C. 3Pt/CSBA-15 even achieves 81.5% C2H4 conversion and 71.6% CO2 yield after 20 h, exhibiting much more prominent catalytic performances than 3Pt/SBA-15. DFT calculations and in situ FTIR measurements confirm that small-sized Pt particles possess strong O2 affinity to promote O2 adsorption, and in situ formed hydrophobic carbon layers efficiently suppress competitive H2O adsorption. Such a unique one-step catalyst preparation method for regulating the size of metal particles and the hydrophobicity of catalysts can be perfectly utilized to develop simple and efficient hydrophobic catalysts applied in low-temperature oxidation of C2H4.

Pd Single-Atom Loaded Ce-Zr Solid Solution Catalysts Prepared by Flame Spray Pyrolysis for Efficient CO Catalytic Oxidation.

Single-atom catalysts (SACs) exhibit remarkable catalytic activity at each metal site. However, conventionally synthesized single-atom catalysts often possess low metal loading, thereby constraining their overall catalytic performance. Here, a flame spray pyrolysis (FSP) method for the synthesis of a single-atom catalyst with a high loading capacity of up to 1.4wt.% in practice is reported. CeZrO2 acts as a carrier and provides a large number of anchoring sites, which promotes the high-density generation of Pd, and the strong interaction between the metal and the support avoids atom aggregation. Pd-CeZrO2 series catalysts have excellent CO oxidation performance. When 0.97wt.% Pd is added, the catalytic activity is the highest, and the temperature can be reduced to 120°C. This work presented here demonstrates that FSP, as an inherently scalable technique, allows for elevating the single-atom loading to achieve an increase in its catalytic performance. The method presented here more options for the preparation of SACs.

Efficient catalytic oxidation of VOCs by a Pd-Pt/SiO2 catalyst: The cooperative catalysis of dual metal sites

Volatile organic compounds (VOCs) are one of the main pollutants produced in industrial processes. Catalytic oxidation is an effective method to eliminate VOCs, and the key lies in designing efficient metal catalyst. In this work, Pd-Pt/SiO2 bimetallic catalysts were designed and prepared by the immobilization method, and their performances for toluene oxidation were evaluated. The addition of Pt into the catalyst elevated markedly the reduction of Pd active sites, leading to abundant electron-deficient Pd0 and electron-rich Pt0 in the Pd2Pt1 catalyst, which were confirmed by TEM, CO pulse adsorption and in-situ XPS. As revealed by O2-TPD and toluene-TPD characterization, the cooperative effect of electron-deficient Pd0 and electron-rich Pt0 in Pd2Pt1 catalyst facilitated the activation of O2 and toluene, thus enhanced greatly its activity. A conversion of 90% (T90) for toluene was achieved over Pd2Pt1 catalyst at 165 ℃, and the apparent activation energy (Ea) over Pd2Pt1 catalyst was lower than that over other Pd-Pt bimetallic and monometallic Pd or Pt catalysts. Additionally, the reaction mechanism was studied by In-situ DRIFTS, the results showed that the toluene oxidation passed successively benzyl alcohol, benzaldehyde, benzoic acid and maleic anhydride, then maleic anhydride was further oxidized to CO2 and water.

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.

Constructing oxygen vacancy-enriched Fe3O4@MnO2 core–shell nanoplates for highly efficient catalytic oxidation of H2S in blast furnace gas

The rational design of catalyst structures holds paramount significance for realizing efficient catalytic reactions. In this study, an Fe3O4@MnO2 core–shell catalyst was successfully synthesized using a facile one-pot method and applied in the selective oxidation of H2S in blast furnace gas. The introduction of the MnO2 shell suppressed the further growth and aggregation of Fe species, leading to outstanding catalytic stability. Simultaneously, abundant oxygen vacancies facilitated the adsorption and activation of oxygen, thereby enhancing H2S oxidation. Experimental results revealed that the Fe3O4@MnO2 catalyst (Fe/Mn = 4:1) displayed 100 % H2S conversion and 95.7 % sulfur selectivity at 150 °C in a humid gas stream containing O2 and CO. Remarkably, no discernible decline in catalytic activity was observed after 170 h of operation, indicating the promising industrial prospects of this catalyst. This study provides an effective strategy for designing efficient and stable desulfurization catalysts.

A novel concept and design for highly efficient photoelectrocatalytic materials with high performance, stability, and charge transport properties: development of an innovative next-generation green technology.

In semiconductors, generating charges via catalysis is a highly challenging task and characteristic of heterojunction photoanodes. A dithiophene-4,8-dione spin-coated film layer has a positive effect on the holes (positive charge carriers) for a long time in BHJ films in the solid state of materials. The photoexcited holes created in the BHJ film can persist for long periods of time, which is beneficial for catalytic reactions. In this study, a photoanode is electrically coupled to a hydrogen gas-evolving platinum cathode. When the photoanode is electrically coupled to a H2 gas evolving Pt cathode, curiously long-lived hole polaron states are observed on the timescale of seconds under operational conditions. These long-lived holes play a crucial role in enhancing the hydrogen peroxide oxidation performance of the film overlayer spin-coated onto the photoanode. The spin-coated film overlayer on the photoanode achieves the best oxidation performance for hydrogen peroxide of approximately 6.5 mA cm-2 at 1.23 VRHE without the need of a catalyst. This demonstrates the effectiveness of the overlayer in improving the catalytic performance of the photoanode with a better efficiency of 17.5% when using 851 nm excitation. This indicates that a relatively high percentage of incident photons at that specific wavelength is converted into photocurrent by the photoanode. This approach can lead to more efficient oxidation catalysis as demonstrated in the case of hydrogen peroxide oxidation.

Cobalt phthalocyanine (CoPc) anchored on Ti3C2 MXene nanosheets for highly efficient selective catalytic oxidation.

Quinclorac is an important precursor for pharmaceutical, agricultural, and synthetic chemistry. The state-of-the-art synthesis of quinclorac via condensation, chlorination and oxidative hydrolysis often uses homogeneous catalysts and strong acid oxidant agents to promote the catalytic oxidation, which requires huge manpower input for the late-stage purification process and is usually environmentally unfriendly. In this work, we successfully fabricated a stable cobalt phthalocyanine (CoPc) Co-based composite (CoPc/Ti3C2) by anchoring CoPc on the surface of Ti3C2 nanosheets for the selective oxidation of 3,7-dichloro-8-dichloro methyl quinoline (3,7-D-8-DMQ) into quinclorac. More impressively, CoPc/Ti3C2-4.5%-Mn-Br exhibits a high selectivity of 91.8% for the catalytic oxidation of 3,7-D-8-DMQ to quinclorac in acetic acid, with a quinclorac yield of 87.5%, which is approximately 2.46 times higher than that of pristine CoPc-Mn-Br. The obtained heterogeneous catalytic system shows good reusability. Detailed mechanistic investigations reveal that the system works through the free radical mechanism via the formation of Co2+/Co3+ redox cycles. This work provides a new understanding for the stabilization of reaction intermediates and facilitates the design of catalysts for selective catalytic oxidation.

A Review of the Preparation of Environmentally Friendly Titanium-Based Nano-Oxidation Materials

In recent years, water environmental pollution and a series of environmental health issues caused by it have posed severe challenges to the green ecological and healthy development under the guidance of the “Carbon peaking and carbon neutrality” goals. Among them, water pollution dominated by typical pollutants has been continuously concerned due to its high detectability, environmental persistence, and complex governance. However, traditional water treatment technologies still have significant limitations in effectively removing such complex organic pollutants. Therefore, the development of efficient and reliable novel catalytic oxidation systems is urgently needed. Environmental functional materials, due to their diverse structures and almost limitless possibilities for functional design, can effectively contribute to the construction of the above-mentioned novel catalytic oxidation systems. In particular, advanced oxidation systems based on environmentally friendly titanium-based nanomaterials have shown excellent application prospects in adsorption and accelerated catalytic breakdown of organic pollutants and have good environmental friendliness. Therefore, this paper reviews the advantages of titanium-based nanomaterials and systematically outlines the preparation methods of practical TiO2-based nano-oxidation materials and novel MXene-Ti-based nano-oxidation materials.

Monolithic catalysts loaded with ZIF-derived Co3O4 on copper foam for the catalytic oxidation of toluene: the impact of synthetic methods

Monolithic catalysts loaded with ZIF-derived dodecahedral Co3O4 on copper foam for the efficient catalytic oxidation of toluene.

Expression of concern: Palladium supported on mixed-metal-organic framework (Co-Mn-MOF-74) for efficient catalytic oxidation of CO.

Expression of Concern for 'Palladium supported on mixed-metal-organic framework (Co-Mn-MOF-74) for efficient catalytic oxidation of CO' by Reda S. Salama et al., RSC Adv., 2021, 11, 4318-4326, https://doi.org/10.1039/D0RA09970H.

A new {P4Mo6}-based complex as a highly efficient heterogeneous catalyst for the oxidation of alkylbenzenes under mild conditions

A new {P4Mo6}-based manganese complex was prepared under solvothermal conditions for efficient catalytic oxidation of diphenylmethane.

Correction and removal of expression of concern: Palladium supported on mixed-metal-organic framework (Co-Mn-MOF-74) for efficient catalytic oxidation of CO.

[This corrects the article DOI: 10.1039/D0RA09970H.].

Efficient catalytic oxidation of biomass to formic acid coupled with low-energy formaldehyde production from methanol

Efficient catalytic aerobic oxidation of biomass to formic acid coupled with low-temperature formaldehyde production from methanol has been developed with the vanadium-substituted heteropoly acid as a catalyst.

Green and efficient catalytic oxidation of ethylbenzene to acetophenone over cobalt oxide supported on a carbon material derived from sugar.

The use of biomass as a carbon source to support metal oxides has significant advantages in environmental protection and reducing the cost of the catalyst. The critical point lies on the development of highly active and recyclable catalysts. In this study, sugar was used as a carbon source, and cobalt oxide was loaded via an in situ method and an impregnation method to prepare the catalyst, respectively. The catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, Raman, in situ electron paramagnetic resonance (in situ EPR) and N2 adsorption-desorption. The characterization results show that the macroporous carbon-supported cobalt oxide catalyst prepared by the in situ method contains CoOx nanoparticles on the support, but the dispersion of cobalt oxide on the support is more uniform compared with the catalyst prepared by the impregnation method. The catalytic performance of the prepared catalyst was evaluated through the oxidation of ethylbenzene (EB) to acetophenone (AP) as a probe reaction. Under the optimized reaction conditions, temperature (T) = 80 °C, m(catalyst) : m(EB) = 0.15, n(H2O2) : n(EB) : n(KBr) = 14.4 : 1 : 0.1, t = 8 h, and V(EB) : V(CH3COOH) = 1 : 10, the conversion of EB and the selectivity of AP were 84.1% and 81.3%, respectively. CoOx/SC-10-in situ exhibits improved reactivity of EB oxidation owing to cobalt ions on the carbon support that promote the free radical and acid catalytic reaction pathway. The cobalt oxide catalyst supported by biomass carbon has decent recycling and regeneration ability, which provides a new idea for the application of biomass.

Surface engineering of ternary mixed transition metal oxides for highly efficient catalytic oxidation of low concentration VOCs

With the widespread application of waterborne painting process, effective removal technologies for low concentration volatile organic compounds (VOCs) is a major concern of the painting industries due to the low mass transfer efficiency. This work presents a unique approach for the molecular-level preparation of precious-metal-free mixed aliovalent-substituted, CeCuOx binary oxide and NiO-modified yNi/CeCuOx ternary mixed metal oxide catalysts. In addition, the excellent catalytic selectivity (no catalytic activity decreases under 5.0 vol% water vapor) of the catalysts was successfully achieved by microstructures optimization and grafting octadecyltrichlorosilane (OTS). Its catalytic activity in the oxidation of toluene at low concentrations (50 ppm) was studied. The 3Ni/CeCuOx sample exhibits the best performance, which achieve 90 % catalytic oxidation of toluene at 197 °C without using noble metals. This results from that the ternary doping and the growth of NiO increases the specific surface area, active lattice oxygen species, activates molecular oxygen species, and provides more catalytic sites, which improve the adsorption and catalysis of toluene. Furthermore, the catalytic stability of the catalysts is also significantly improved by the addition of the hydrophobic coating. Therefore, the unique catalysts have great potential in practical applications for low concentration VOCs removal of painting industries.

Copper on charcoal: TEMPO free Cu0 nanoparticles catalyzed aerobic oxidation of alcohols

A highly efficient and Tempo-free catalytic aerobic alcohol oxidation method has been developed using charcoal-supported Cu0 nanoparticles（Cu-A） in conjunction with pyridine. Various alcohols, bearing different functional groups, can be readily oxidized to their corresponding ketones and aldehydes under mild conditions.

Atomically Dispersed Co on N-Doped Porous Carbon for the Highly Efficient Catalytic Oxidation of Aromatic Alcohols to Acids and Nitriles

Atomically Dispersed Co on N-Doped Porous Carbon for the Highly Efficient Catalytic Oxidation of Aromatic Alcohols to Acids and Nitriles

APPLICATION OF FENTON'S HETEROGENEOUS SYSTEM FOR THE TREATMENT OF ORGANIC-CONTAINING WASTEWATER

With the growth of the Earth's population, the problem of the shortage of clean water is becoming global. And for the survival of humanity, it is necessary to significantly reduce the amount of harmful wastewater that pollutes the environment. Wastewater polluted with organic substances, usually produced by the production of dyes and the food industry, causes great damage to the environment.
 The expediency of catalytic oxidation for the treatment of organic-containing effluents has been theoretically substantiated. As a catalyst, it is proposed to use new nanostructured composites of the «core-shell» type based on transition metal oxides (CoFe2O4/SiO2/CuO) for the Fenton system. The oxidizing agent in this system is H2O2, which is used in «green technologies».
 It was investigated that the degree of destruction of the dye methylene blue (MB) depends on the composition of the catalyst, the ratio of the concentrations of the catalyst and dye, and the presence of a preliminary stage of dye adsorption.
 The investigated catalyst was tested on simulated dairy wastewater (SDW). The research was carried out in a barbotage-type apparatus (Schott filter). For the system «dairy wastewater – CoFe2O4/SiO2/CuO – О2– Н2О2», the degree of dairy wastewater treatment is 63 %, and residual COD value is 39,52 mgO2/dm3. It was established that in the process of purification by the CoFe2O4/SiO2/CuO catalyst, active oxidizing compounds are formed, which significantly intensify the process.
 Thus, there are reasons to assert that the prospect of developing a highly efficient catalytic oxidation technology in the Fenton system for the treatment of wastewater containing organic pollutants. And the results obtained and the conclusions drawn about the technological feasibility of using CoFe2O4/SiO2/CuO as a catalyst can find practical application for the implementation of technological schemes closed behind water and in other wastewater treatment technologies, in particular food production.