Catalytic Oxidation Research Articles

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.

A rational construction of FexOy-N-ZSM-5 catalyst with graphene structures and FeNx sites for the selective catalytic oxidation of triethylamine

Stabilizing metal species at the atomic level and tuning their catalytic properties is a significant challenge. Herein, an N-doped FexOy-N-ZSM-5 catalyst with layered and chain-like graphene structures is reported. The catalyst can selectively catalyze the oxidation of triethylamine (TEA) with an efficiency of 99.7 % at 240 °C, and maintain an N2 yield of 97.6 % over the reaction temperature range of 240–360 °C. The results indicate that the layered graphene in the catalyst provide anchor sites for active Fe, while the abundant chain-like graphene act as connectors between ZSM-5 and the layered graphene, offering ample opportunities for TEA and its intermediates to contact the catalyst surface. This increases the number of active sites on the catalyst, thereby enhancing the catalytic performance of FexOy-N-ZSM-5. Notably, due to the interaction between FeOx and FeNx species, FexOy-N-ZSM-5 exhibits excellent thermal stability and water resistance, demonstrating promising potential for practical.

Reactive adsorption and catalytic oxidation of gaseous hydrogen sulfide using a prototype air purifier built with bismuth-doped titanium dioxide

A prototype air purifier (AP) module has been constructed using bismuth-doped titanium dioxide (Bix-P25: x(%) as Bi/Ti molar ratios of 1.1, 2.1, 3.3, 5.3, and 8.7). The reactive adsorption property of Bix-P25 materials is evaluated against H2S gas at a recirculation rate of 160 L min−1 in a 17 L closed chamber. The AP (Bi5.3-P25) exhibits superior performance against 10 ppm H2S in dry air under dark conditions (i.e., without light irradiation), with a removal efficiency (XH2S)= 99% in 5 mins, reaction kinetic rate (r (at X = 10%))= 7.3 mmol h−1g−1, and partition coefficient= 0.18 mol kg−1 Pa−1. As such, its superiority is evident over the reference AP (P25) filter with XH2S < 10%. The clean air delivery rate (CADR) of AP (Bi5.3-P25) increases noticeably from 9.9 to 17.8 L min−1 with increasing relative humidity (RH) from 0 to 80%, respectively. In contrast, the CADR decreases from 9.9 to 5.8 L min−1 as the H2S increases from 10 to 20 ppm. According to density functional theory (DFT), the presence of H2O vapor enhances the hydroxylation of Bix-P25 surface to promote H2S mineralization through the formation of TiS3 (i.e., thermodynamic reaction of S atom with the catalytic surface). Complete removal of H2S on the Bi5.3-P25 surface is also confirmed consistently through gas chromatography-mass spectrometry (GC-MS), in-situ diffuse reflection infrared spectroscopy (in-situ DRIFTS), and elemental analysis (EA). This work represents the first utilization of Bix-P25 materials fabricated on an AP platform toward the desulfurization of H2S at room temperature (RT). The practical utility of Bix-P25 is overall validated by its eminent role in reactive adsorption and catalytic oxidation (RACO) of H2S from the air.

Strongly active and environmentally friendly WO3/C3N4 photocatalysts for converting cyclohexane to cyclohexanone under ambient conditions

C–H bond activation under mild conditions remains a great challenge in the chemical industry, while catalytic cyclohexane oxidation is inefficient and often requires organic solvents and strong oxidants. This study constructed a C3N4/WO3 Z-type heterojunction catalyst to efficiently convert cyclohexane into cyclohexanone and cyclohexanol (KA oil) through aqueous phase oxidation by O2 under visible light irradiation. With strong redox performance and high photogenerated carrier separation ability, the proposed composite catalyst can produce the key active species for cyclohexane oxidation in the H2O–O2 system. The reaction mechanism was clarified through experiment and DFT theory calculation. Cyclohexane was converted into cyclohexyl radical under the action of ·OH, and ·O2− converted most products into cyclohexanone. The catalyst can be recycled under optimized process conditions while reaching a KA oil yield of 139.73 μmol g−1 h−1 and a selectivity of 93.1%.

Resourceful exploitation of sedimentary clay: Designing a dual-chambered borosilicate glass reactor system for the efficient treatment of malachite green and phenol through SCRT adsorption and 5%Fe@SRCT catalysis via CWPO, with evaluation of seed germination and fish survival.

This study presents an innovative double-walled borosilicate glass reactor system for the efficient treatment of liquid and gaseous wastewater. This reactor system allows precise temperature control, continuous pH monitoring, and controlled dosing of reagents to optimize reaction conditions. Detailed characterization was carried out by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), BET (specific surface area) analysis, point of zero charge (PZC), and scanning electron microscopy (SEM) for the SCR, SCRT, and 5%Fe@SCRT materials. For Malachite Green adsorption, SRCT demonstrated a maximum adsorption capacity of 39.78 ±0.5mg/g using the Langmuir isotherm model and followed pseudo-second-order kinetics. Optimum conditions for adsorption were found to be: an initial concentration of 50 ppm, an adsorbent dosage of 1g/l, a pH of 8.5, and a temperature of 50°C. For the catalytic oxidation of phenol, 5%Fe@SRCT achieved a remarkable removal rate of 99.9±0.1% under optimum conditions (50 ppm phenol, 1g/l catalyst dosage, pH3.5, H2O2 concentration 8.7mM, and temperature 70°C). Intermediates identified during the reaction included hydroquinone, benzoquinone, catechol, and resorcinol, with degradation occurring over a 60-minute reaction period. The 5%Fe@SCRT material showed excellent reusability in the removal of phenol by catalytic oxidation, with no significant loss of efficiency over three cycles, while the SRCT underwent three cycles of regeneration for the adsorption of Malachite Green. Scavenger tests confirmed the involvement of hydroxyl radicals in the catalytic oxidation process. In addition, fish survival tests after catalytic oxidation of phenol by 5%Fe@SRCT showed no impact on fish, underlining the environmental safety of this process. In addition, germination tests after decolorization of MG by SRCT demonstrated a good effect with no negative impact, reinforcing the ecological value of this innovative technology. These results highlight the innovative use of SCRT and 5%Fe@SCRT as versatile materials for environmental remediation, exploiting their effective adsorption capacities and efficient catalytic oxidation performance within the proposed double-walled borosilicate glass reactor system. PRACTITIONER POINTS: The study demonstrates the effectiveness of an innovative reactor system employing SRCT adsorbent and Fe@SRCT catalyst for efficient removal of malachite green and phenol from wastewater. Environmental impact assessment, including seed germination and fish survival evaluation, validates the method's eco-friendly potential. Implementation of this approach could significantly contribute to sustainable water treatment practices.

Anchoring PdOx clusters on defective alumina for improved catalytic methane oxidation

Evolution of the Pd active centers in size and spatial distribution leads to an irreversible deactivation in many high-temperature catalytic processes. This research demonstrates the use of a defective alumina (Al2O3-x) as catalyst support to anchor Pd atoms and suppress the growth of Pd clusters in catalytic methane oxidation. A combination of operando spectroscopy and density functional theory (DFT) calculations provide insights into the evolution of Pd species and reveals distinct catalytic methane oxidation mechanisms on Pd single atoms, clusters, and nanoparticles (NPs). Among these Pd species, the cluster active centers are found to be the most favorable participants in methane oxidation due to their high dispersion, high content of Pd2+ oxidation state, and resistance to deactivation by carbonates, bicarbonates, and water. The Pd/Al2O3-x catalyst shows increased stability with respect to a Pd/Al2O3 counterpart during simulated aging in alternating reducing and oxidizing conditions due to stronger interactions with the support. This study demonstrates that defect engineering of non-reducible supports can constrain the evolution of active centers, which holds promising potential for widespread utilization across diverse industrial catalytic processes, including various hydrogenation and oxidation reactions.

Formal kinetics of catalytic oxidation of diesel paraffin-naphthenic fraction in the presence of carbon nanotubes containing Co, Mn and Fe

This study identified the formal kinetics of aerobic oxidation of the paraffin-naphthenic fraction of diesel fuel in the presence of multi-walled carbon nanotubes (MWCNTs) containing three transition metals—Fe, Co, and Mn. The synthesis of metal-containing multi-walled carbon nanotubes (M@MWCNTs) was carried out by pyrolysis of cyclohexane in the presence of ferrocene (CVD synthesis), followed by sequential doping of the resulting iron-containing carbon nanotubes Fe@MWCNTs with Co and Mn clusters. The resulting Fe–Co–Mn@MWCNT samples were identified using electron microscopy (SEM, TEM) and elemental analysis. The resulting carbon nanotubes were found to have a diameter of 30–60 nm and length of 500–800 μm. Iron clusters were observed to be present within the channels, while Co and Mn particles were observed to be present in the outer space of the nanotubes. The formal kinetic regularities of the dearomatized diesel fraction aerobic oxidation promoted by M@MWCNT additives were studied. It has been demonstrated that metal-nanocarbon additives effectively catalyze the oxidation process in the absence of hydroperoxides, resulting in thermal decomposition. The introduction of Co and Mn clusters into the nanotube structure has been observed to enhance catalytic activity. A catalytic oxidation scheme is currently under consideration, with corresponding effective oxidation rates being determined. It is postulated that these findings may prove useful in the estimation of effective nano-catalytic systems for the oxidative conversion of multicomponent hydrocarbon feedstocks.

Simulation study on the oxidation performance of low-concentration methane preheating direct current catalytic oxidation plant considering thermal radiation

In this study, the process of catalytic oxidation of methane considering radiative heat transfer was simulated using FLUENT computational software to study the effect of thermal radiation on the oxidation performance of the simulated device, and to investigate the extent to which radiative heat transfer affects the oxidation performance of the device under different operating conditions. The results show that the extent to which thermal radiation affects the oxidative performance of the equipment increases with increasing inlet temperature. When the intake temperature reaches 900K, its proportion is close to 45 %. At the same time, as the inlet gas temperature increases, the maximum reaction temperature of the oxidation unit is 1154 K, and the methane conversion rate reaches up to 89 %. The main factor affecting the oxidation performance of the unit at this time is radiation heat transfer. The extent to which thermal radiation affects the oxidative performance of the device diminishes with increasing inlet velocity. When the wind speed reaches 2 m/s, the proportion of radiative heat transfer is only 10 %, the maximum reaction temperature of the plant falls to 993 K, and the methane conversion rate drops to 68 %. At this time, the main factor affecting the oxidation performance of the plant is convective heat transfer. The influence of thermal radiation on oxidation performance gradually diminishes with an increase in intake velocity, and the proportion of radiative heat transfer decreases continuously. At methane concentrations above 1 %, the proportion of radiative heat transfer is less than 25 per cent, the maximum reaction temperature of the unit increases to 1087 K, and the methane conversion rises to 88 %. At this point, the main factor affecting the oxidation performance of the plant is convective heat transfer.

Treatment of Crude Phosphoric Acid Using Activated Carbon-Based Nanocomposites Integrated with Catalytic Wet Peroxide Oxidation

Treatment of Crude Phosphoric Acid Using Activated Carbon-Based Nanocomposites Integrated with Catalytic Wet Peroxide Oxidation

Strong water-resistant Co-Mn solid solution derived from bimetallic metal–organic frameworks for catalytic destruction of toluene

The construction of Co-Mn mixed metal oxides catalysts derived from bimetallic MOFs has great significance for catalytic destruction of toluene. Hence, a series of CoaMnbOx-MOFs with different physicochemical properties were successfully synthesized via pyrolysis of Co-Mn bimetallic MOFs. Attributing to the higher specific surface area, more active sites (Co3+ and Mn3+), stronger reducibility and abundant defect sites, the as-prepared Co1Mn1Ox-MOFs dispalyed an optimal catalytic performance, especially the excellent water vapor resistance. The result of the In Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy demonstrated that toluene can be degraded at relatively low temperatures (＜100 °C). Benzyl alcohol, benzaldehyde, benzoic acid and maleic anhydride were the main intermediate products in toluene degradation process. This work reveals the value of bimetallic MOFs derived Co-Mn oxides for toluene oxidation and presents a novel avenue for designing mixed metal oxide catalysts with potential applications in VOCs catalytic oxidation.

Ultrafast flowing oxidation reactions in the CoTiO3/TiO2 heterojunction assembled on ceramic membranes: Properties and electron shuttle mechanism

In this study, a novel catalytic ceramic membrane (CCM) applied to couple peroxymonosulfate (PMS) to degrade organic pollutants in wastewater were synthesized by sol–gel method. The CCM was surface-loaded by CoTiO3/TiO2 heterojunction nanoparticles as catalytic layer, achieving an instantaneous oxidation efficiency of 90 % for bisphenol A (BPA, 10 mg/L). The electron shuttle process in the CoTiO3/TiO2 heterojunction was confirmed by theoretical calculations, and strong adsorption (Eads = -5.28 eV) was observed between catalysts and PMS. Differential charge density further suggested the trend of electron transfer from the catalytic layer to the vicinity of PMS, causing an elongation of the peroxy bond of PMS from 1.482 Å to 1.794 Å, which led to the generation of SO4•− and ·OH. Typical non-radical featured by 1O2 was also found in the membrane-base catalytic oxidation system. Finally, the degradation pathways of BPA were elucidated, and the toxicities of degradation products were found to be decreased significantly. The CoTiO3/TiO2 heterojunction modified CCMs couple with PMS could form an efficient synergistic coupling system, which has excellent oxidation to various organic pollutants. This research on the properties and mechanism of the CCMs could provide technical and theoretical backing for efficient oxidation treatment of dissolved organic pollutants in wastewater.

Supported Co3O4 catalyst on modified UiO-66 by Ce4+ for completely catalytic oxidation of toluene

Creating a new low-temperature catalyst in decreasing the emission of volatile organic compounds (VOCs) has great significance under different industrial production situations. In particular, the Zr-UiO-66 is optimized by different amounts of cerium, which not only enhances the physicochemical stability but also increases the number of active sites of CexZryUiO-66. Furthermore, the catalysts with Co3O4 nanoparticles supported on CexZryUiO-66 were successfully prepared via impregnation method. In the process of toluene degradation, the Co/Ce1Zr2-UiO-66 attains a 90% conversion rate at 210 °C with a space velocity of 60000 mL/(g·h) and toluene concentration at 1000×10–6. Meanwhile, the carbon dioxide selectivity reaches 100% at 218 °C. The Co/Ce1Zr2-UiO-66 shows great water resistance (3 vol% H2O). Multiple characterization methods were used to figure out the physicochemical properties of the catalysts. It is found that the addition of an appropriate amount of cerium can enhance stability of UiO-66 and surface lattice oxygen proportion. Additionally, the stronger electron transfer between Ce4+ and Co2+ enables the Co/Ce1Zr2-UiO-66 to possess more active surface oxygen species and Co3+ cationic species in all samples.

Highly Stable MOFs-Derived Cu–Co Composite Metal Oxides for Catalytic Oxidation of Toluene

CuCoOx was prepared by in situ pyrolysis of Cu2+ partially substituted MOF-74 precursor with Co-MOF as a template for catalytic oxidation of toluene. T90 (the temperature corresponding conversion of 90%) was only 212°C, at 1000 ppm toluene and weight hourly space velocity (WHSV) of 36 000 mL g–1 h–1. In addition, the conversion was maintained above 97% for 74 h of continuous reaction at 260°C. Even if after 2400 ppm 1,2-dichloroethane (1,2-DCE) poisoning for 2 h, the toluene conversion was still up to 93%, demonstrating excellent stability and resistance to deactivation of catalyst. Furthermore, The high activity and stability of CuCoOx could be attributed to the large specific surface area as well as the high Co2+/Co3+, Cu2+/Cu+, and Olatt/Oads molar ratios.

Synergistic catalytic degradation of benzene and toluene on spinel MMn2O4 (M[dbnd]Co, Ni, Cu) catalysts

Owing to the complexity of multicomponent gases, developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging. The spinel MMn2O4 (MCo, Ni, or Cu) catalysts were successfully synthesized via the sol–gel method and tested for their catalytic performance for simultaneous degradation of benzene and toluene. The CuMn2O4 sample exhibited the best catalytic performance, the conversion of benzene reached 100 % at 350 °C, and toluene conversion reached 100 % at 250 °C. XRD, N2 adsorption-desorption, HRTEM-EDS, ED-XRF, Raman spectroscopy, H2-TPR, NH3-TPD, O2-TPD and XPS were used to characterize the physical and chemical properties of MMn2O4 catalysts. The excellent redox properties, high concentration of surface Mn4+, and adsorption of oxygen species over the CuMn2O4 sample facilitated the simultaneous and efficient removal of benzene and toluene. Additionally, in situ DRIFTS illustrated the intermediate species and reaction mechanism for the synergetic catalytic oxidation of benzene and toluene. Notably, as an effective catalytic material, spinel oxide exhibited excellent synergistic degradation performance for benzene and toluene, providing some insight for the development of efficient multicomponent VOC catalysts.

Performance of catalytic wet oxidation on thermochemical aqueous effluents assessed by FT-ICR MS

Aqueous phase (AP) is frequently observed in bio-oil from biomass thermochemical conversion or as an upgrading coproduct. However, AP contains high organic content that can be toxic and that must be reduced or removed to be then treated in existing wastewater plants. A promising method to upgrade these APs is the catalytic wet peroxide oxidation (CWPO) that was applied here on APs of both hydrothermal liquefaction and pyrolysis bio-oils from softwood and hardwood. Efficiency of the CWPO was assessed by investigating the molecular composition of raw and treated APs by ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization (ESI) in negative- and positive-ion modes. Combination of FT-ICR MS and multivariate statistical analyses evidenced efficiency of the process with new compounds resulting from the oxidative depolymerization, characterized by lower unsaturation degree and molecular weight, and higher oxygen atom count. Refractory compounds were also observed, which are notably characterized by high unsaturation degrees. Interestingly, both detection modes were shown to be complementary for the understanding of the CWPO process. ESI (-) allowed to assess the completion of the oxidation process in detecting carboxylic acid conversion products and to specifically evidence refractory products. ESI (+) was informative on the CWPO process, especially on the conversion of the basic compounds, with the decrease of the detected species. Eventually, softwood AP was shown to be more reluctant to CWPO than the hardwood one.

Catalytic Complete Oxidation of Ethyl Acetate on MnOx/MgAl2O4 Catalysts

Catalytic Complete Oxidation of Ethyl Acetate on MnOx/MgAl2O4 Catalysts

Enhanced catalytic performance and antichlorine poisoning over Cu-doped cobalt oxide nanosheets for chlorobenzene oxidation

The degradation of Chlorinated volatile organic compounds (CVOCs) by catalytic oxidation forms toxic products, and catalysts may be poisoned by chlorine at low temperatures. To address this, a Cu-assisted strategy is proposed for enhancing the catalytic degradation of chlorobenzene (CB) over cobalt oxide nanosheets. The Cu-doped Co3O4 catalysts exhibited lower T90 values (temperatures with 90 % conversion) and improved stability compared to the unmodified catalyst. These results were attributed to strong metal-metal interactions between Cu species and cobalt oxide nanosheets, which showed a high specific surface area, reduced binding energy of lattice oxygen, higher surface oxygen concentration, and more surface Co3+ species. These properties promoted low-temperature catalytic activity. In addition, the disappearance of Cu2+ satellite peak after the catalyst is used, indicating that the Cu2+ also contributes to the catalytic activity. Furthermore, the in situ FTIR spectra provided details about the reaction mechanism of CB degradation over Cu-doped cobalt oxide nanosheets. The oxygen vacancy generation and the surface absorption of chlorine-containing intermediates were calculated using density functional theory calculations. This study provides new insight into novel pathways for catalyst design aimed at CB degradation.

Challenging design of highly active Pt/CeO2–TiO2/ZSM-5 catalysts for VOCs low-temperature removal

Four Pt/CeO2–TiO2/ZSM-5 catalysts with different Pt species dispersion states and acidic properties were designed, and key factors affecting the oxidation activity of various VOCs (benzene, DCE, ethyl acetate and acetonitrile as typical organic compounds of aromatic hydrocarbon and halogen/oxygen/nitrogen-containing VOCs, respectively) were identified in the present work. The strength of the acid and oxidation sites on the surface of catalysts and their synergistic interaction play a crucial role. Highly dispersed Pt species and its strong redox ability promote low-temperature oxidation of benzene. A synergistic interaction between the acid and oxidation sites is required to achieve high DCE oxidation activity. An abundance of surface acid sites (particularly strong acid sites) favors the adsorption and dechlorination to form vinyl chloride of DCE, and the strong redox ability of oxidation sites would accelerate the deep oxidation of intermediates (such as vinyl chloride and acetic acid, etc.). For ethyl acetate or acetonitrile oxidation, the strong acidic property of the catalyst plays a prior role for their catalytic oxidation, which facilitates the low-temperature hydrolysis of ethyl acetate or acetonitrile. This work provides a significant thought to design and synthesize high activity catalysts for low-temperature oxidation of various VOCs pollutants.

Coordination-Adaptive Molecular Platform for Catalytic Water Oxidation

Coordination-Adaptive Molecular Platform for Catalytic Water Oxidation

Adjustment mechanism of Co3+ performance in Co3O4-LaOx catalyst for high-efficiency catalytic combustion of toluene

This study employed the sol–gel method to fabricate Co-La catalysts under various calcination temperatures were used to the catalytic oxidation of toluene. The investigation on the impact of calcination temperature on the Co3+ content and the resultant catalytic activity was studied. The CoLa-550 catalyst (calcined at 550 °C) exhibited the highest concentration of Co3+ and optimal catalytic performance for toluene oxidation (T90 = 195 °C). In situ DRIFTS technology confirmed the ring-opening of benzoic acid was the rate-determining step. Comprehensive analyses utilizing XPS, H2-TPR, and O2-TPD revealed the significance of optimizing Co3+ content to enhance catalytic activity. This research provided crucial theoretical and experimental support for the development of efficient non-noble metal catalysts.