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Manganese oxide (MnO2) exhibits excellent activity for volatile organic compound oxidation. However, it is currently unknown whether lattice oxygen or adsorbed oxygen is more conducive to the progress of the catalytic reaction. In this study, novel hollow highly dispersed Pt/Copper modified-MnO2 catalysts were fabricated. Cu2+ was stabilized into the δ-MnO2 cladding substituting original K+, which produced lattice defects and enhance the content of adsorbed oxygen. The 2.03 wt% Pt Cu0.050-MnO2 catalyst exhibited the highest catalytic activity and excellent stability for toluene and benzene oxidation, with T100 = 160 °C under high space velocity (36,000 mL g−1 h−1). The excellent performance of catalytic oxidation of VOCs is attributed to the abundant adsorbed oxygen content, excellent low-temperature reducibility and the synergistic catalytic effect between the Pt nanoparticles and Cu0.050-MnO2. This study provides a comprehensive understanding of the Langmuir–Hinshelwood (L-H) mechanism occurring on the catalysts.

A series of Ce1–xTixO2 mixed oxide catalysts were synthesized by sol-gel method and then loading of noble metal (M=Pt, Rh, Ru) was used for soot oxidation. Ti-doped Ce1–xTixO2 catalysts (x is the molar ratio of Ti/(Ti + Ce) and ranges from 0.1 to 0.5) exhibit much better oxidation performance than CeO2 catalyst, and the Ce0.9Ti0.1O2 catalyst calcined at 500 °C has the best catalysis activity. Each noble metal (1 wt%) was supported on Ce0.9Ti0.1O2 (M/C9T1) and the properties of the catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, Brunauer–Emmett–Teller (BET) method, and H2-temperature programmed reduction (H2-TPR) results. Results show that the introduction of Ti into CeO2 forming Ti-O-Ce structure enhances the catalytic activity and increases the number of oxygen vacancies at the catalyst surface. The noble metal is highly dispersed over Ce0.9Ti0.1O2, and M/C9T1 catalysts present enhanced activity in comparison to Ce0.9Ti0.1O2. It is found that noble metals can greatly increase the activity of the catalyst and the oxidation rate of soot resulting from noble metals can enhance the electron transfer capacity and oxygen adsorption capacity of the catalyst. A small amount of Ti doping in CeO2 can significantly improve the activity of the catalyst, while a large amount of Ti reduces the performance of the catalyst because a large amount of Ti is enriched on the surface of the catalyst, which hinders the contact and reaction between the catalyst and the soot.

Spherical CeO2 synthesized by the hydrothermal process was used as support to prepare Pt/WO3/CeO2, and the effects of tungsten (W) contents on activity, stability and polychlorinated by-products was investigated to understand the role of W for vinyl chloride (VC) catalytic oxidation. The introduction of 12 wt% W to Pt/CeO2 (P12WC) exhibits the highest catalytic activity with 90% conversion of VC at 250 °C, meanwhile the stability improves and the polychlorinated by-products in the tail gas significantly decrease due to the removal of dissociated Cl species in the formation of HCl. The beneficial effects of W on Pt/CeO2 are closely related to the chemical state of Pt, redox and surface acid sites distribution. The doping W not only makes Pt disperse evenly on the support with the high valence, but also weakens the interaction between Pt and CeO2 by the formation of Pt-O-W and Pt-O-W-O-Ce species, which facilitates oxygen mobility. In addition, the modification of W species also significantly increases the surface acidity amount and changes the distribution of acid sites.

The temperature of waste gas in refuse transfer station, airport smoking area, and RTO terminal is low, which needs deep oxidation. Catalytic ozonation is one of the most effective treatment techniques in these scenarios. In this study, we reported that catalysts were modified under the condition of magnetic field to simulate the low temperature dynamic conditions of low concentration toluene for catalytic ozonation. This paper aims to explore the relationship between oxygen vacancy and active oxygen species, and the specific pathways of toluene oxidation. The study found that citric acid can enhance the synergistic effect between Mn and Ce, and promote the generation of oxygen vacancies. The surface molecule adsorption oxygen is more conducive to catalytic oxidation than subsurface atom adsorption oxygen. Finally, we proposed the main pathways of toluene in this reaction system, which runs through the whole process of the reaction.

Electrochemically deposited sensors and DNA biosensors have been widely used in the food industry, and various other fields due to their high sensitivity, fast response, easy operation, no pollution, and low price. A rare earth electrochemically deposited gadolinium ferricyanide thin film modified glassy carbon electrode, and the investigation of electrocatalytic oxidation of guanine by GaHCF/GCE is reported. We deposited electrochemically a rare earth terbium ferricyanide thin film modified glassy carbon electrode. OH was investigated through various characteristics such as capacitance–voltage, Differential Pulse Voltammetric and many more by the comparison of catalytic oxidation signal of guanine with ·OH in Fenton reaction.

A novel iron-coordinated conducting polymer is synthesized, followed by the preparation of Fe3N nanoparticle-embedded sulfur and nitrogen-doped carbon (Fe3N/SNC) nanostructures via a one-step polymer pyrolysis strategy, which can exceptionally catalyze the oxygen reduction reaction (ORR) in both alkaline and acidic media, and the oxidation of catecholamines. To synthesize the metal coordinated polymer, FeCl3 is used as an oxidant and metal source for the polymerization of 3′,4′-diamino-terthiophene (DAT) to form poly-FeDAT. It is subsequently pyrolyzed at 900 °C to attain the Fe3N/SNC catalyst. The Fe3N/SNC electrocatalyst exhibit a more positive onset (0.985 V vs RHE), half-wave potentials (0.848 V), a higher limiting current density (5.47 mAcm−2), alcohol resistance and durability than the benchmark Pt/C in 0.1 M KOH, and it is comparable to Pt/C in 0.1 M HClO4. It also displays exceptional performance for the catalytic oxidation of catecholamines and AP, which results in simultaneous detection of DA and AP in trace amounts (the detection limits were 110 nM and 270 nM (S/N = 3) for each species, respectively). The unique catalytic activity is ascribable to the presence of pyridinic-N, graphitic-N, and Fe–N along with thiophene-S in the carbon, resulting in catalytically enhanced electron transfer from Fe3N to N, S doped carbon.

Transition metal clusters have been used for water oxidation with high catalytic efficiency. However, they are water soluble and often used homogeneously rather than heterogeneously. Herein, a water soluble octanuclear Cu(II) cluster was heterogenized through binding with α-undecatungstosilicate [α-SiW11O39]8- via electrostatic effect. Octanuclear cluster [Cu8(dpk·OH)8(OAc)4]4+ (dpk·OH = monoanion of the hydrated, gem-diol form of di-2-pyridyl ketone) was transformed into insoluble [Cu8(dpk·OH)8(OAc)4]2@[α-SiW11O39] (1) composite. This composite catalyzes water electro-oxidation efficiently with an onset potential of only 370 mV and attains a catalytic current density of 1 mA/cm2 at low overpotential of 580 mV with a Tafel slope value of 62 mV/decade at near-neutral pH. Electrochemical measurements and spectroscopy characterization indicate this composite remains stable and active after prolonged electrolysis experiments. This work reveals that electrostatic interaction between transition metal complexes and polyoxoanions is a feasible and convenient method to synthesized efficient heterogenized homogeneous water oxidation catalyst (WOCs).

Formaldehyde is an important air pollutant and its removal is essential to protect human health and meet environmental regulations. Ag-based catalyst has a considerable potential for HCHO oxidation in low temperature range. The valence state of Ag is one of the key roles in formaldehyde catalytic oxidation. However, its effect on activity is still ambiguous. Non-thermal plasma and conventional calcination were employed to regulate Ag valence state in this study. Three Ag-Co/CeO2 catalysts with totally different distribution of Ag species were obtained. A special mixed Ag valence state, ~50% Agδ+ with a few Ag0 and Ag+, was achieved by plasma activation. It had the merits of both good activity and stability. A close relationship between Ag valence state and the activity for HCHO oxidation was established. The activity of different Ag species follows the order: Agδ+ + Ag0 + Ag+ > Agδ+ > Ag0 > Ag+.

International audience; Two hydroxyapatite supported CuO (10 wt% Cu) catalysts were prepared using the wet impregnation method via the conventional process and with the addition of native β-cyclodextrin using Cu(NO3)2.3H2O as copper precursor and adopting a ratio of β-cyclodextrin to copper of 0.1. After the impregnation step, the materials were dried at 80 °C and calcined in flowing dry air at 400 °C. The copper supported materials were characterized in the dried state and after calcination by means of conventional methods including X-ray diffraction, TG-MS, H2-TPR-MS, Raman spectroscopy, UV-vis-DR, ToF-SIMS and XPS. It was found that β-cyclodextrin hasd a profound impact on the final properties of the catalysts, both in terms of reducibility and dispersion of active species. It is suggested that at the early stages of the calcination, some hydroxyl groups of the β-CD units in close contact with Ca2+ of hydroxyapatite could play the role of spacers between the copper-based entities thus minimizing the aggregation process of the CuO nanoparticles. Finally, these copper oxide catalysts prepared from β-cyclodextrin were able to oxidize toluene more efficiently than the conventional catalyst. The copper oxide particles generated by the thermal decomposition of Cu2(OH)3(NO3) were smaller than those formed with copper nitrate alone and exhibited a higher reducibility, two key determinants for VOC total oxidation on transition metal oxides.

Cu-containing Beta zeolites (Cu-Beta) are straightforwardly synthesized in a one-pot method without template, where the crucial step is the co-hydrolysis/condensation of silica source and copper salt at the moderate acidic condition. In the solvent-free oxidation of cyclohexane with molecular oxygen (O2), the best cyclohexane conversion result (9.7%) with a KA-oil (cyclohexanone and cyclohexanol) selectivity of 94.1% is obtained over Cu-Beta(100). Structure—activity relationship analysis indicates that the isolated tetrahedral framework Cu2+ species and chemisorption oxygen species in high concentration on the catalyst surface enhannce the catalic performance. In addition, the catalyst can be easily separated and still remain stable after recycling five times, providing new insights into catalysts design for the catalytic oxidation of cyclohexane to KA-oil.

CuO–CeO2 (Cu–Ce) catalyst with a CuO/CeO2 mass ratio of 1 prepared by a sol–gel method is used in the CO catalytic oxidation reaction in the actual industrial sulfur-containing atmosphere. At a reaction temperature of 200 °C, the catalyst exhibits quite different stability under sulfur-containing and sulfur-free conditions. When 30 ppm SO2 was added to the feed gas, the Cu–Ce catalyst had an initial CO conversion rate of 100%, gradually decreasing after 26 h, and this catalyst completely deactivated at about 50 h. However, the CO conversion rate of the catalyst under sulfur-free conditions could be nearly maintained at 100% within the measured time range (60 h). The results of IR, Raman, and XPS characterizations proved that the accumulation of cerium sulfate on the Cu–Ce catalyst would cover the active sites of the catalyst, eventually leading to the complete deactivation of the catalyst, which provides favorable evidence for the actual industrial anti-sulfur application.

Two novel Ti-oxo wheel cluster substituted silicotungstates (STs) [H2N(CH3)2]9H9[Ti6O6(SiW10O37)3]·11H2O (1) and [H2N(CH3)2]16H10[Ti10O11(SiW10O37)2(SiW9O35)2]·14H2O (2) have been made by hydrothermal reactions. The polyoxoanion of 1 is a ring-shaped trimer where a Ti6O6 ({Ti6}) wheel cluster is encapsulated by three divacant [SiW10O37]10- (SiW10O37) fragments. However, 2 is built by two divacant SiW10O37 units and two rare trivacant [SiW9O35]12- (SiW9O35) fragments and further installs an unprecedented Ti10O11 ({Ti10}) double-wheel cluster. To the best of our knowledge, 2 is rare in POM chemistry. Studies on the catalytic oxidation properties reveal that 1 exhibits high catalytic activity toward the oxidation of various sulfides using H2O2 as an oxidant. Furthermore, 1 can be facilely recycled and reused for at least five cycles without obvious loss of catalytic activity.

A detailed reaction mechanism and kinetic model have been developed to study the catalyzed oxidation of ethylbenzene. The model is used to compute the time profiles of ethylbenzene and three products: acetophenone, benzaldehyde, and benzoic acid. The kinetic model is evaluated on three different reported studies for ethylbenzene oxidation with iron- and cobalt-based catalysts using tert-butyl hydrogen peroxide as an oxygen source, in solventless condition and at various experimental conditions. The model shows good fit for the concentration profiles with time and with the change in parameters like ethylbenzene-to-tBHP ratio and temperature. Activation energy and pre-exponential factors are calculated from Arrhenius plots using the values of rate constants derived using the proposed model. It was established that the excess amount of oxidant in the reaction mixture leads to over-oxidation products, which was not captured experimentally. The hypothesis is supported with the simulation results from modified model.

MnO2 nanorods with exposed (110), (100), or (310) facets were prepared and investigated for catalytic oxidation of chlorobenzene, then the (110)-exposed MnO2 nanorod was screened as the candidate parent and further modified by Pt and/or Mo with different contents. The loading of Pt enhanced activity and versatility of the pristine MnO2, but the polychlorinated byproducts and Cl2 were promoted, conversely, as the decoration of Mo inhibited the polychlorinated byproducts and improved durability. Determination of structure and properties suggested that Pt facilitated the formation of more oxygen vacancies/Mn3+ and surface adsorbed oxygen weakened the bonds of surface lattice oxygen, while Mo stabilized surface lattice oxygen and increased acid sites, especially Bronsted acid sites. Expectedly, Pt and Mo bifunctionally modified MnO2 presented a preferable activity, selectivity, and durability along with the super resistance to H2O, high-temperature, and HCl, and no prominent deactivation was observed within 30 h at 300 °C under dry and humid conditions, even at high-temperature aging at 600 °C and HCl-pretreatment (7 h). In this work, the optimized Mo and Pt codecorated MnO2 was considered a promising catalyst toward practical applications for catalytic oxidation of actual Cl-VOCs emissions.

To achieve “waste controlled by waste”, a novel wet process using KMnO4/copper converter slag slurry for simultaneously removing SO2 and NOx from acid-making tail gas was proposed. Through the solid-liquid separation for copper slag slurry, the liquid-phase part has a critical influence on removing NOx and SO2. Also, the leached metal ions played a crucial role in the absorption of SO2 and NOx. Subsequently, the effects of single/multi-metal ions on NOx removal was investigated. The results showed that the leached metal from copper converter slag (Al3+, Cu2+, and Mg2+) and KMnO4 had a synergistic effect on NOx removal, thereby improving the NOx removal efficiency. Whereas Fe2+ had an inhibitory effect on the NOx removal owing to the reaction between Fe2+ and KMnO4, thereby consuming the KMnO4. Besides, SO2 was converted to SO42− completely partly due to the liquid catalytic oxidation by metal ions. The XRD and XPS results indicated that the Fe (II) species (Fe2SiO4, Fe3O4) in copper slag can react with H+ ions with the generation of Fe2+, and further consumed the KMnO4, thereby resulting in a decrease in the NOx removal. The characterization of the slags and solutions before and after reaction led us to propose the possible mechanisms. The role of copper slag is as follows: (1) the alkaline substances in copper slag can absorb SO2 and NO2 by KMnO4 oxidation. (2) copper slag may function as a catalyst to accelerate SO2 conversion and improve NOx removal by synergistic effect between leached metal ions and KMnO4.

Electrocatalytic oxidation of ammonia is an appealing, low-temperature process for the sustainable production of nitrites and nitrates that avoids the formation of pernicious N2O and can be fully powered by renewable electricity. Currently, however, the number of known efficient catalysts for such a reaction is limited. The present work demonstrates that copper-based electrodes exhibit high electrocatalytic activity and selectivity for the NH3 oxidation to NO2− and NO3− in alkaline solutions. Systematic investigation of the effects of pH and potential on the kinetics of the reaction using voltammetric analysis andin situ Raman spectroscopy suggest that ammonia electrooxidation on copper occurrs via two primary catalytic mechanisms. In the first pathway, NH3 is converted to NO2− via a homogeneous electrocatalytic process mediated by redox transformations of aqueous [Cu(OH)4]−/2− species, which dissolve from the electrode. The second pathway is the heterogeneous catalytic oxidation of NH3 on the electrode surface favoring the formation of NO3−. By virtue of its nature, the homogeneous-mediated pathway enables higher selectivity and was less affected by electrode poisoning with the strongly adsorbed “N” intermediates that have plagued the electrocatalytic ammonia oxidation field. Thus, the selectivity of the Cu-catalyzed NH3 oxidation towards either nitrite or nitrate can be achieved through balancing the kinetics of the two mechanisms by adjusting the pH of the electrolyte medium and potential.

Oxidation of the N–phosphonomethyl iminodiacetic acid (PMIDA) with hydrogen peroxide in a two-phase system (aqueous phase—organic phase) in the presence of the [(Octn)3NMe]3{PO4[WO(O2)2]4} catalyst was studied and the kinetic parameters of this reaction were determined. It was found that the PMIDA oxidation with aqueous H2O2 proceeds only in the presence of the catalyst giving PMIDA N-oxide as the main product. Under the studied conditions, the reaction orders with respect to the reagents (PMIDA and H2O2) and the catalyst were found to be the first. The apparent activation energy of the reaction for the temperature range of 313–343 K is 37 ± 3 kJ/mol.

A novel Ti-W-O-cluster-substituted tungstoantimonate (TA), [H2N(CH3)2]3Na4H9[{Ti6W4O18(OH)(H2O)3}(B-α-SbW9O33)3]·20H2O (1), has been made by hydrothermal reactions of trivacant [B-α-SbW9O33]9- units, Ti4+ cations, and WO42- anions in the presence of [H2N(CH3)2]·Cl and structurally characterized. Intriguingly, the polyoxoanion of 1 is constructed from three [B-α-SbW9O33]9- units and a previously unobserved decanuclear heterometallic Ti-W-O cluster [Ti6W4O18(OH)(H2O)3]11+ ({Ti6W4}) that is comprised of an octahedral [Ti6WO6(H2O)3]18+ cluster and an edge-sharing [W3O12(OH)]7- fragment via six W-O-Ti/W linkers. Furthermore, studies on the catalytic oxidation properties reveal that 1 possesses good catalytic activity toward the oxidation reactions of various sulfides and cyclooctene based on the environmentally friendly oxidant H2O2.

The CoxOy/AC catalysts were prepared by wet impregnation method for toluene oxidation removal from air. The thermal stability of cobalt nitrate and Co oxide on the activated carbon (AC) support sur...

Alkali metal potassium is conducive to structure promotion and electronic modulation in metal oxides. Here, K species was successfully introduced into α-MnO2 via in situ synthesis (Pre-K/MnO2) and hydrothermal impregnation method (Post-K/MnO2) with target to boost the low-temperature reactivity and deep destruction efficiency for toluene oxidation. Results reveal that Post-K/MnO2 possesses the highest catalytic activity with toluene (1000 ppm) totally mineralized at just 258 °C, achieving over 70 °C of temperature reduction than that of Pre-K/MnO2. K specie shows obvious charge transfer balance ability in MnO2, forming MnO6-K-MnO6 bridging bond and leading to more uniform energy of Mn-O bonds. High electron density of K+ can promote the activation of oxygen molecules, resulting in a better catalytic performance of toluene. Abundant Bronsted acid sites are beneficial for toluene adsorption and regeneration of hydroxyl on the surface, which promote the degradation of intermediates during toluene oxidation. Moreover, Post-K/MnO2 shows satisfied catalytic performance under different space velocities and initial concentrations and humid condition. Density functional theory (DFT) calculation revealed the situation of oxygen vacancy and toluene/oxygen adsorption energy in catalysts with different K doping locations. Results showed that the adsorption energy is stronger when K located in large tunnel (0.46 × 0.46 nm), and it is easier to form oxygen vacancy while K entered the small tunnel (0.33 × 0.33 nm). The present work paves new insights into the designing of efficient transition metal oxide catalyst for VOC deep purification.

Catalyst support is crucial to modulating and immobilizing the active metal phases and the catalytic performance can be optimized by the rational design of support. Herein, the hierarchical alumina microspheres with abundant coordinatively unsaturated pentacoordinated Al3+ (Al3+penta) sites were constructed by a facile solvothermal method and then employed as the support materials to anchor Pd species. XPS and NMR results revealed that Pd species were prone to the adsorption, dispersion and stabilization over Al3+penta sites by strong interaction in the form of Pd4+ species. During the catalytic oxidation process, the crystal structure and morphology of Pd/Al2O3 catalysts remained stable, but the surficial lattice oxygen and cationic Pd4+ species presented a distinct increase. In comparison with the fresh catalyst, the catalytic performance of the used Pd/Al2O3 catalysts exhibited a significant improvement and still kept unchanged even after the multiple consecutive catalytic process. The used Pd/Al2O3 catalyst also possessed the excellent water tolerance and almost 1000 ppm toluene at a weight hourly space velocity of 60 000 mL gcat−1 h−1 could be converted into nontoxic CO2 and H2O over the catalyst surface.

A chemiluminescence (CL) instrument was developed to understand the CL behavior of catalytic oxidation of CO and hydrocarbons, which are major processes occurring in catalytic converters. The instrument is based on the cooperation among a gas mixer, a custom-made CL analyzer, and an on-line gas chromatography. The concept of the CL method was formulated by thoroughly investigating the CL emission during the catalytic oxidation of CO and C3H6 in the presence of O2 and/or NO under both stoichiometric and non-stoichiometric conditions. All the oxidation reactions were found to be CL-active, where the CL intensity increased exponentially with the temperature. The steady-state measurements showed good linearity between the CL intensity and the reaction rates, demonstrating that the CL emission is a direct product of the reactions. It was also found that the CL intensity per CO2 production was different among the reactions, most plausibly due to both/either the presence of multiple CL processes and/or the difference in the heat of the reactions. Based on the linear correlation between the CL intensity and the reaction rate, a feasibility study was successfully demonstrated for rapid catalyst evaluation in C3H6 oxidation.

In this study, the effects of ammonia (NH3) were explored for catalytic oxidation of elemental mercury (Hg0) over CeO2/TiO2, CuO/TiO2, Fe2O3/TiO2, and V2O5-WO3/TiO2 catalysts. In the presence of 50 ppm NH3, the results showed that CuO/TiO2 catalysts could still maintain 98–100 % of Hg0 conversion in the range of 100–400 °C, while the catalytic performance of other catalysts was significantly inhibited by NH3 in the same temperature range. NH3 resistance was observed on CuO/TiO2 catalysts. The catalysts were further characterized by means of XRD, H2-TPR, XPS, NH3-TPD, BET, and in-situ DRIFTS. For the CuO/TiO2 catalysts, Cu(II) was the primary Cu species that conducive to the strong reducibility properties which beneficial for the catalytic performance. The mechanism of NH3 resistance in Hg0 oxidation over CuO/TiO2 catalysts was proposed. At low-temperature range (lower than about 250 °C), abundant weak acidic sites contributed to the superior Hg0 adsorption capacity. The Hg0 oxidation activity was enhanced correspondingly. At high-temperature range (about 250–400 °C), the Hg0 oxidation performance was mainly affected by the oxidation of NH3 and the products. The main product of NH3 oxidation was NO2, which could promote Hg0 oxidation activity.

The synthesis of a new RuII-based water oxidation catalyst is presented, in which a nitrophenyl group is introduced into the backbone of dpp via a pH-sensitive imidazole bridge (dpp = 2,9-di-(2′-pyridyl)-1,10-phenanthroline). This modification had a pronounced effect on the photophysical properties and led to the appearance of a significant absorption band around 441 nm in the UV–vis spectrum upon formation of the monoprotonated species under neutral conditions. Theoretical investigations could show that the main contributions to this band arise from transitions involving the imidazole and nitrophenyl motif, allowing us to determine the pKa value (6.8 ± 0.1) of the corresponding, twofold protonated conjugated acid. In contrast, the influence of the nitrophenyl group on the electrochemical properties of the catalytic center was negligible. Likewise, the catalytic performance of Ru(dppip-NO2) and its parent complex Ru(dpp) was comparable over the entire investigated pH range (dppip-NO2 = 2-(4-nitrophenyl)-6,9-di(pyridin-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline). This allowed the original catalytic properties to be retained while additionally featuring a functionalized ligand scaffold, which provides further modification opportunities as well as the ability to report the pH of the catalytic solution via UV–vis spectroscopy., Modification of water oxidation catalysts results in a pH-sensitive ligand scaffold. Detailed UV−vis spectroscopic and theoretical studies show that changes in the pH have a significant impact on the photophysical behavior of the compound. Despite this, electrochemical investigations suggest no significant alteration of the redox properties of the catalytic center and photocatalytic experiments reveal that the catalytic performance of the original complex could be retained.

Fracking flowback fluids treated via catalytic oxidization, flocculation, and sedimentation can be reinjected into low-permeability strata. Owing to their large-scale production during fracking operations, recycling such fluids would considerably mitigate freshwater wastage. However, having undergone catalytic oxidation and flocculation treatments, they are highly mineralized and must be desalinated before being reused as fracking fluids. In this study, we investigated the oxidation + flocculation + nanofiltration (NF) treatment process employed for flowback fluids and measured the ion removal and water recovery rates of an NF apparatus using simulated waters containing different ion types and concentrations. More than 94% of the calcium, magnesium, and sulfate ions contained in the simulated waters were removed via NF. With an influent sulfate ion concentration of less than 500 mg/L, the overall sulfate removal rate was greater than 90%. Although NF does not remove borate ions as efficiently as it removes other ions, the borate concentration was nevertheless significantly reduced. Moreover, high recovery rates were obtained for all simulated waters. The NF of a flowback fluid previously treated via oxidation and flocculation resulted in a permeate whose water quality indices satisfied all the requirements of recycled fracking fluids.

Combining the redox properties of Co and the acid properties of Nb in a Co3-Nb-Ox catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH3 (NH3-SCR). Co3O4 shows average activity, however, it exhibits a poor N2 selectivity. Nb2O5 is not active for NH3-SCR. However, the mixed Co3-Nb-Ox catalyst shows higher NO conversion and N2 selectivity than the single Co3O4 and Nb2O5 catalysts at 100–300 °C. The results of temperature programmed reduction by H2 and X-ray photoelectron (XP) spectra indicate that the addition of Nb changes the chemical states of Co and decreases the concentration of Co3+ and Oα, adjusting the activity for catalytic oxidation to a moderate level. This suppresses the formation of undesired N2O from the over-oxidation of NH3. Incorporation of Co and Nb into one solid synergistically couples their redox behavior and surface acidity, ensuring the high catalytic activity and N2 selectivity in NH3-SCR.

Zinc aluminate (ZnAl) was used as support to obtain a series of rhodium-modified Co-ZnAl catalysts for the catalytic oxidation of propane and naphthalene. The catalysts were characterized by various techniques including N2 adsorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), diffuse reflectance spectroscopy (DRS), FTIR and X-ray photoelectron spectroscopy (XPS), to correlate chemical and physical characteristics with catalytic properties. TPR and XPS techniques show the presence of segregated cobalt compounds, as well as cobalt species interacting with the support. Segregated cobalt species are considered responsible for the catalytic activity, due to their high reducibility. The addition of Rh promotes the reducibility of the cobalt compounds yielding to an increase in the surface content of Co2+. For propane oxidation, the best activity shown by the Rh(0.5)Co(5)-ZnAl sample could be associated with a synergic effect between rhodium and cobalt species. No specific effects were revealed due to the addition rhodium for the naphthalene oxidation.

4-Nitroacetophenone is an important intermediate for the manufacture of broad-spectrum antibiotics, in particular chloramphenicol. Existing methods of ketone synthesis are imperfect. The disadvantage of the simplest of them (the oxidation of 4-nitroethylbenzene by oxygen at atmospheric pressure and temperature of 135 °C, in the presence of manganese oxide) is the low yield and the need for the process in a heterogeneous environment. Therefore, the development of affordable and inexpensive ways to obtain 4-nitroacetophenone is an actual task. The aim of the work is to investigate the products and kinetics of the reaction of catalytic oxidation of 4-nitroethylbenzene by ozone in acetic acid and to develop a new low-temperature synthesis of 4-nitroacetophenone. Materials and methods. The experiments were used 4-nitroethylbenzene, 4-nitroacetophenone and 1-(4-nitrophenyl)ethanol by company Acros organics qualification “puriss.”; manganese (II) acetate qualification “puriss.”; as a solvent – glacial acetic acid by company Sigma qualification “puriss.”. A spectrophotometric method was used to continuously monitor the current concentration of ozone in the gas phase. A Teflon flow cell with quartz windows was installed in the measuring chamber of the SF-46 LOMO spectrophotometer, which allowed the measurement of the optical density of the gas flow in the UV region. The concentration of ozone at the inlet and outlet of the reactor was determined by recording the results on the potentiometer KSP-4 in the form of an ozonogram when passing ozone-containing gas through a cuvette at a wavelength of a monochromatic light source 254–256 nm. The quantitative content of the reaction mixture was performed using gas-liquid chromatography, calculations of the concentration of components were performed by the method of internal standard. Results. The products and kinetics of the reaction of ozone with 4-nitro-ethylbenzene in the presence of a catalyst – manganese (II) acetate were studied. It was found that at a temperature of 20 °C the oxidation process proceeds mainly along the side chain, while the yield of 4-nitroacetophenone reaches 98.5 %, also the system identified trace amounts of 1-(4-nitrophenyl)ethanol. This fact is explained by the fact that ozone under catalysis conditions preferably reacts not with the substrate, but with Mn (II) with the formation of the active form of Mn (IV) which, in turn, is reduced by reaction with 4-nitroethylbenzene, and thus initiates oxidation of the substrate. on the side chain. Conclusions. Catalytic oxidation of 4-nitroethylbenzene by ozone in acetic acid solution proceeds mainly along the side chain to form 4-nitroacetophenone with a yield of 98.5 %. The optimum reaction temperature is 20–30 °C, as its increase deepens the oxidation process and the ketone begins to be converted into 4-nitrobenzoic acid.

Presently, the treatment of four-way catalysts is important for reducing pollutant emissions from diesel engine exhaust, which is a major cause of urban haze. In this study, we prepared perovskite-type catalysts via the citric acid sol-gel method. Experiment results showed that K substitution at site A in LaMnO3 decreased the agglomeration of the catalysts effectively, increased the contact with the reaction gas, promoted the conversion of Mn3+ → Mn4+, and reduced the ignition temperature of soot. Ce substitution at the B-site in La0.5K0.5MnO3 produced a CeO2 phase and decreased the Mn4+/Mn3+ ratio to 0.49, which is conducive to improving the catalytic oxidation performance. The K and Ce co-doping had the best activation effect, which showed a low activation energy (10.87 KJ mol-1) and a high simultaneous removal rate of NO x (reaching 90% at 275 °C) and soot ignition at 250 °C under lean conditions.

Most of the current electrocatalysts for the methanol oxidation reaction are precious group metals such as Pt, Pd, and Ru. However, their use is limited due to their high cost, scarcity, and issues with carbon monoxide poisoning. We developed a simple method to prepare a nickel foam (NF)-based monolith electrode with a NiO nanosheet array structure as an efficient electrocatalyst toward the oxidation of methanol to produce formate. By a simple ultrasonic acid treatment and air oxidation at room temperature, an inert NF was converted to NiO/NF as a catalytically active electrode due to the uniform NiO nanosheet array that was rapidly formed on the surface of NiO/NF. In alkaline electrolytes containing methanol, the as-prepared NiO/NF catalysts exhibited a lower methanol oxidation reaction (MOR) potential of +1.53 V vs RHE at 100 mA cm-2 compared to that of inert NF samples. The difference in potentials between the EMOR and the EOER at that current density was found to be 280 mV, indicating that methanol oxidation occurred at lower potentials as compared to the oxygen evolution reaction (OER). We also observed that the NiO/NF could also efficiently catalyze the oxidation of CO without being poisoned by it. NiO/NF retained close to 100% of its initial activity after 20,000 s of methanol oxidation tests at high current densities above 200 mA cm-2. Because of the simple synthesis method and the enhanced catalytic performance and stability of NiO/NF, this allows methanol to be used as an OER masking agent for the energy-efficient generation of value-added products such as formic acid and hydrogen.

The interaction between Cu and Mn has been used to immobilize the Cu single-atom on MnO2 surface by redox-driven hydrolysis. Comprehensive structure and property characterizations demonstrate that the existence of an Cu-Mn interaction on the catalyst surface can effectively restrain the aggregation of Cu single atoms and improve carbon monoxide (CO) oxidation activity. The interaction of forming the Cu-O-Mn entity is beneficial for CO catalytic activity as the migration of reactive oxygen species and the coordination effect of active centers accelerate the reaction. In particular, 3%-Cu1 /MnO2 shows an oxygen storage capacity (OSC) value (342.75 μmol/g) more than ten times that of pure MnO2 (27.79 μmol/g) and has high CO catalytic activity (T90% =80 °C), it can maintain CO conversion of 95 % after 15 cycles. This work offers a reliable method for synthesizing Cu single-atom catalysts and deepens understanding of the interaction effect between single transition metal atoms and supports that can improve the catalytic activity of CO oxidation.

In this work, the commercial selective catalytic reduction (SCR) catalyst V2O5-MoO3/TiO2 was sulfureted with H2S to improve both its capability for elemental mercury (Hg0) removal at low temperatures and its resistance to SO2 and H2O. Hg0 removal over both V2O5-MoO3/TiO2 and sulfureted V2O5-MoO3/TiO2 involved the catalytic oxidation of Hg0 to HgCl2 and the chemical adsorption of gaseous Hg0; therefore, the effect of sulfuration on Hg0 chemical adsorption and the catalytic oxidation of Hg0 to HgCl2 over V2O5-MoO3/TiO2 and its resistance to SO2 and H2O were investigated using Hg balance analysis. Kinetic analysis showed that the rates of the chemical adsorption and oxidation of Hg0 were both in direct proportion to the concentration of physically adsorbed Hg0. The physical adsorption of gaseous Hg0 on V2O5-MoO3/TiO2 was remarkably promoted after sulfuration, and the physical adsorption of gaseous Hg0 over sulfureted V2O5-MoO3/TiO2 was scarcely inhibited by SO2 and H2O. Therefore, the performance of V2O5-MoO3/TiO2 for Hg0 removal and its resistance to SO2 and H2O were both improved after sulfuration. Even more remarkably, sulfureted V2O5-MoO3/TiO2 can adsorb gaseous HgCl2, which resulted from Hg0 oxidation. Therefore, sulfureted V2O5-MoO3/TiO2 showed an excellent performance to recover Hg0 from coal-fired power plants, which can then be converted to liquid Hg.

Simultaneous poisoning of sulfur + phosphorus on a platinum-based diesel oxidation catalyst was studied to gain a deeper understanding on the catalyst deactivation. Compared to a single poisoning (sulfur or phosphorus), the simultaneous poisoning had a severe effect on the catalyst activation: light-off temperature for 90% conversion of propene was not reached, this of carbon monoxide was much higher than expected, and the maximum conversion of nitrogen monoxide collapsed. With very comprehensive structural characterization by various methods (e.g. STEM-EDS, XPS, DRIFTS) used, we achieved to conclude an explanation for this. In the case of the S + P-poisoning of the catalyst, formed aluminum phosphate was found to block adsorption sites for sulfur species on alumina and sulfur adsorbs mainly on cerium oxides. In addition, sulfur species remain with and in the vicinity of the platinum particles blocking active sites. publishedVersion

Ceria supported platinum catalyst has now been widely studied due to its excellent activity for CO oxidation. However, the electron state of active metal center is still an open question. In this work, a ceria nanorod support was prepared and platinum (Pt) with 0.9 at% was deposited using an impregnation method to obtain Pt/CeO2 catalyst. With the help of “light-off” experiment and temperature-programmed reduction under CO (CO-TPR) test, the conclusion is proposed that the process of hydrogen reduction can enhance the activity of CO oxidation reaction for the generation of optimal active Pt site. An innovative near-situ X-ray absorption fine structure (XAFS) technique was used to investigate the chemical state of central Pt atom during the reaction process, clearly demonstrating that the high oxidized state of Pt does harm to the activity for CO oxidation while the relatively reductive Pt exhibits high activity, and the different oxidized state and chemical environment of Pt during every process has been identified. Furthermore, the activity of our Pt/CeO2 catalyst is superior to that of most of the previous reports about CO catalytic oxidation by Pt based catalyst. Moreover, the optimal active species (Pt–O4) have been identified after hydrogen reduction, which could be a possible key strategy to control the oxidation of Pt.

Catalytic oxidation is believed to be the most efficient method for indoor formaldehyde purification. Herein, we reported that the Pt/Na-ZSM-5 catalyst with low Pt loading (0.16 wt %) prepared by d...

Palladium and palladium-silver alloy nano catalysts were synthesized from aqueous precursor at room temperature via a single vessel chemical reduction and co-reduction methods in absence of capping agent. XPS analysis confirms the presence of Pd and Ag in the catalyst matrix. Microscopic analyses reveal spherical morphology of the catalyst in the nanoscale dimension. The electro-analytical investigation of the catalyst loaded on carbon electrode shows that the Pd4Ag nano alloy catalyst demonstrates marked improvement in electro-catalytic efficiency among all prepared catalysts for ethanol oxidation in alkali. The Pd4Ag/C catalyst shows the mass normalized peak current density of 522 mA mg−1Pd in cyclic voltammetric (CV) study, which is 1.97 times greater than that of similarly synthesized Pd/C (264.2 mA mg−1Pd) catalyst. Chronoamperometric and impedance analyses further establish the superiority of Pd4Ag/C catalyst. To discover the plausible mechanism, the CV study is typically extended to the intermediates like sodium acetate which reveals that though Pd is better for catalytic oxidation of intermediate than the best catalyst but the optimal OH− adsorption on the surface of the metal, favours catalytic oxidation of ethanol more on Pd4Ag catalyst. The mechanistic path of the reaction is anticipated by evaluating the ex-situ FTIR and chromatographic studies which explain the promotion of the formation of carboxylate in comparison to carbonate by Ag.

The aim of the paper is investigation of neutralization of solvent vapors of the brand 646 by an adsorption-catalytic method. The adsorption-catalytic method includes the following stages: adsorption of the solvent components by adsorbent, thermal desorption and periodic flameless catalytic oxidation of organic substances to carbon dioxide and water. Synthetic zeolite of the NaX brand was used as a sorbent, catalyst was porous Al2O3/SiO2 ceramic foam material with an active catalytic phase. Solvent contains aceton, toluene, butylacetate, ethanol, ethyl cellosolve, n-butanol. It is shown that the value of the sorption volume of zeolite for each class of compounds depends on the certain factors: the length and structure of the carbon skeleton, the position of the hydroxyl group (for alcohols and esters), number of methyl groups in the molecules (for benzene derivatives). The conversion of the mixed solvent components was 65.4–90.1 %.

H2S catalytic elimination via selective oxidation process has received considerable attention because it can transform highly toxic H2S into elemental sulfur under mild condition without thermodyna...

Formaldehyde is one of the hazardous indoor air pollutants which have harmful effects on humans, domestic animals, and environmental health. The goal of this study was to synthesize a Pt/Al2O3 coated on granular activated carbon (GAC), which is easily recoverable and can be used as an absorbent for formaldehyde removal from polluted indoor air. Moreover, the Pt/Al2O3 catalyst could achieve complete and stable HCHO oxidation at ambient temperature. The characteristic properties of the Pt/Al2O3/GAC sample were analyzed using scanning electron microscopy, energy-dispersive spectrometer, Fourier-transform infrared spectroscopy, and Brunauer–Emmett–Teller techniques. The Pt/Al2O3/GAC catalyst was investigated to determine the catalytic performance with regard to formaldehyde (HCHO) oxidation under different face velocity and initial formaldehyde concentration applicable to a building environment. It was revealed that the removal capacity of Pt/Al2O3 catalyst reached a maximum of 2.23 mg g−1 during 0.1 m s−1 face velocity and 0.75 ppm HCHO inlet concentration. Among zero-, first- and second-order reaction kinetic model, the correlation coefficient of the first-order reaction kinetic model (0.7948

Interaction of copper ions with Aβ peptides alters the redox activity of the metal ion and can be associated with neurodegeneration. Many studies deal with the characterization of the copper binding mode responsible for the reactivity. Oxidation experiments of dopamine and related catechols by copper(II) complexes with the N-terminal amyloid-β peptides Aβ16 and Aβ9, and the Aβ16[H6A] and Aβ16[H13A] mutant forms, both in their free amine and N-acetylated forms show that efficient reactivity requires the oxygenation of a CuI-bis(imidazole) complex with a bound substrate. Therefore, the active intermediate for catechol oxidation differs from the proposed “in-between state” for the catalytic oxidation of ascorbate. During the catechol oxidation process, hydrogen peroxide and superoxide anion are formed but give only a minor contribution to the reaction., The redox cycling of copper bound to amyloid-β peptide requires the generation of a Cu(I)-Aβ-catecholate complex. When copper(II) is confined in the N-terminal portion, its reduction is slow and causes a shift toward a bis-His coordination environment. The addition of catechol to the Cu(I)-bis(imidazole) complex results in a faster reaction with dioxygen. The reactive species for catechol oxidation does not correspond to the proposed “in-between state” for ascorbate oxidation.

Industrial catalysts usually encounter great challenges in Cl· deactivation, toxic by-products generation, and stability with a long running operation for catalytic oxidation of chlorinated volatile organic compounds (CVOCs). In this research, spinel-type oxides with transition metal substituted as active oxides supported on cordierite (Crd) was identified to catalytic degradation of chlorobenzene (CB). The Cu1.4Mn1.6O4 spinel-type oxides considered as the main active oxides have been identified, which were confirmed by XRD and TEM. The activities of these CuMxMn2−xO4 catalysts were markedly improved by lower calcining temperature and shorter time. CuCe0.25Mn1.75O4/Crd catalyst displayed the highest activity and good stability due to that CeO2 nano-rods structure conducive to increase the Oads amount, the dispersion of active oxides, the strength of weak acidity, the surface areas and pore volume. Moreover, spinel-type with CeO2 doping exhibited high performance in CVOCs elimination attributed to the high storage capacity of oxygen, plentiful oxygen vacancies, good efficiency in breaking C–Cl bond and the easy shuttles between Ce3+ and Ce4+, which were demonstrated by XPS. The results indicate that CeO2, Oads, and ·OH have beneficial effects on the removing Cl· into benzene, and then improving the ring-opening of CB for CB degradation.