Catalytic Oxidation Properties Research Articles

Effect of Al and Zn on Oxygen Evolution Reaction of (FeCoNiMnCu)3O3.2

AbstractBecause of its low cost and abundant sources, hydrogen serves as a clean energy alternative capable of successfully substituting fossil fuels. A highly efficient method for generating hydrogen energy currently is by the electrolysis of water. The oxygen‐extraction reaction (OER), a component of water electrolysis, requires a complex chemical pathway that involves multiproton and multielectron interactions. To enhance reaction efficiency in the OER process, catalysts are crucial; thus, the search for high‐performance, cost‐effective catalysts is underway. This experimental study involved the enhancement of the five‐membered high‐entropy oxide (FeCoNiMnCu)3O3.2 by incorporating a sixth group element (Zn, Al). The organization, morphology, and OER properties were analyzed following the preparation utilizing a mechanical ball milling process. A series of rock salt‐type hexagonal high entropy oxides with differing ball milling durations were synthesized to investigate the influence of the production method on the surface shape and catalytic properties of high entropy oxides. The results indicated that the single‐phase rock salt structure of (FeCoNiMnCuAl)3O3.5, a high‐entropy oxide, exhibited significantly altered diffraction peaks, hence improving OER performance. Optimization of the preparation technique revealed that a 72‐h ball milling duration resulted in an overpotential of merely 293 mV and an electrochemically active surface area approximately double that of the other milling durations.

Construction of Multiphase Concave Tetrahedral PdInMo Nanocatalyst for Enhanced Alcohol Oxidation

AbstractHeterogeneous palladium‐based catalysts show excellent catalytic properties for electrocatalytic oxidation of alcohols, but the construction of such heterogeneous catalysts is a challenge. Here, a multiphase tetrahedral PdInMo nanocatalyst is prepared by a one‐pot reaction method. And the multiphase tetrahedral PdInMo nanocatalyst consists of a face‐centered cubic structure and an intermetallic structure. Due to the oxygen affinity of indium and molybdenum atoms, the interface defects of internal multiphase structure, and intermetallic structure, the multiphase concave tetrahedral PdInMo nanocatalyst shows enhanced catalytic efficiency in the electrocatalytic oxidation reaction of methanol and ethanol. Compared with commercial Pd/C catalysts, PdIn0.117Mo0.037 nanocatalyst has the best mass activity and specific activity. In electrocatalysis of methanol oxidation, the mass activity (2205.57 mA mgPd−1) and specific activity (6.67 mA cm−2) are 4.81 and 3.40 times than that of a commercial Pd/C nanocatalyst (458.5 mA mgPd−1, 1.96 mA cm−2), respectively. In the electrocatalysis of ethanol oxidation, the mass activity (2668.49 mA mgPd−1) and specific activity (8.11 mA cm−2) are 4.06 and 3.14 times than that of the commercial Pd/C nanocatalyst (655.83 mA mgPd−1, 2.58 mA cm−2), respectively. This study provides a reference for the design of highly efficient palladium catalysts for alcohol oxidation.

Catalytic properties of trivalent rare-earth oxides with intrinsic surface oxygen vacancy

Oxygen vacancy (Ov) is an anionic defect widely existed in metal oxide lattice, as exemplified by CeO2, TiO2, and ZnO. As Ov can modify the band structure of solid, it improves the physicochemical properties such as the semiconducting performance and catalytic behaviours. We report here a new type of Ov as an intrinsic part of a perfect crystalline surface. Such non-defect Ov stems from the irregular hexagonal sawtooth-shaped structure in the (111) plane of trivalent rare earth oxides (RE2O3). The materials with such intrinsic Ov structure exhibit excellent performance in ammonia decomposition reaction with surface Ru active sites. Extremely high H2 formation rate has been achieved at ~1 wt% of Ru loading over Sm2O3, Y2O3 and Gd2O3 surface, which is 1.5–20 times higher than reported values in the literature. The discovery of intrinsic Ov suggests great potentials of applying RE oxides in heterogeneous catalysis and surface chemistry.

Synthesis and characterization of bagasse cellulose-based quaternary ammonium peroxyphosphotungstate and their catalytic properties for cyclohexene oxidation in the absence of any solvent

Bagasse cellulose, an industrial waste byproduct of sugar production, was demonstrated to be a viable solid support for a solid-phase ionic oxidation catalyst enabling organic solvent-free aqueous reaction conditions and facile catalyst recovery. Bagasse cellulose-supported quaternary ammonium peroxyphosphotungstate was synthesized from bagasse cellulose-supported quaternary ammonium chloride, phosphotungstic acid, and hydrogen peroxide. The chemical structure of this material was characterized by SEM, XRD, FT-IR, XPS, and 13C NMR, revealing stability of the cellulose matrix to the catalyst loading conditions and effective dispersion of the acicular catalyst crystals throughout the matrix. High catalytic activity of this synthetic complex was demonstrated in the oxidation of cyclohexene to 1,2-cyclohexanediol with hydrogen peroxide in the absence of solvent. Optimized conditions providing trans-1,2-cyclohexanediol with 86.2 % selectivity were 12 wt% catalyst and 4 mL/g 30 % H2O2 (vs. cyclohexene) at 50 °C for 10 h.

Intelligent optimization of steam gasification catalysts for palm oil waste using support vector machine and adaptive transition marine predator algorithm

The present study investigates the optimization of the steam gasification process for the conversion of palm oil waste into environmentally friendly energy, utilizing the catalytic properties of calcium oxide and coal bottom ash. The objective of our research is to investigate the enhancement of the conversion process by employing a machine-learning approach. Specifically, we utilize a support vector machine (SVM) to model and evaluate the impact of different operational parameters on the resulting gas mixture. One notable feature of this study involves the incorporation of an adaptive marine predator algorithm (AMPA) into the SVM framework, aiming to enhance the predicted precision and efficiency of the model. The primary focus of this study revolves around the development of an intelligent optimization framework that surpasses conventional machine learning techniques, hence providing a more dynamic and efficient strategy for process improvement. The SVM model’s performance, as assessed against experimental benchmarks, exhibits a notable degree of predictive accuracy and substantial concurrence with observed data. This increase in performance indicates that our methodology has the potential to make a significant contribution to the enhancement of renewable catalysts in gasification processes. The findings of this study could potentially have significant ramifications for the advancement of renewable energy production and the creation of intelligent systems in complicated industrial applications.

Influence of Copper Powder Structure on the Catalytic Properties of Cerium Oxide

Influence of Copper Powder Structure on the Catalytic Properties of Cerium Oxide

Cerium/sulfur co-doped spinel iron-cobalt oxide@carbon interconnected mesh networks as superior peroxymonosulfate activator for tetracycline degradation

Transition metal spinel oxides have potential applications in activating peroxymonosulfate (PMS) to generate reactive substances for degrading organics in polluted water. However, many catalytic materials have low efficiency, indicating the need for advancements in material design. In this study, we present the one-step fabrication of Ce, S-codoped spinel iron-cobalt oxide@carbon (Ce-FeCo2O4@SxC) with interconnected mesh networks for efficient PMS activation in degrading tetracycline hydrochloride (TCH). Among the Ce-FeCo2O4@SxC samples, Ce-FeCo2O4@S1.5C demonstrates the highest catalytic performance, achieving a TCH degradation efficiency of 97.2 % in 30 min. Moreover, the catalytic system also exhibits anti-interference abilities against various anions and shows universality in degrading organic pollutants. Characterization and experimental tests confirm the co-existence of radical (SO4•−, •OH and O2•−) and non-radical pathways (1O2 and direct electron transfer), with 1O2 identified as the primary reactive species. Three plausible pathways for TCH removal are proposed based on detected intermediate products. Toxicity evaluation reveals a significant reduction in the toxicity of the original TCH solution during the degradation process with the PMS activator. This study introduces a simple yet effective co-doping strategy to enhance the catalytic properties of spinel oxides for PMS activation in degrading organic contaminants in aquatic environments.

Nickel oxide electroplating and electrode surface modification for electrochemical detection of glutamate

The electrochemical behavior and catalytic properties of nickel oxide (NiOx) are enhanced through cathodic electroplating and subsequent electrochemical activation in an alkaline aqueous electrolyte. The electrochemical detection of ʟ-glutamate becomes feasible by introducing an amine group through immobilizing APTES ((3-aminopropyl)triethoxysilane) on the NiOx surface, resulting in a positive charge. The synergistic effect of electrochemically activated electroplated NiOx and the APTES-modified surface facilitates the effective electrochemical detection of trace ʟ-glutamate. The APTES-activated NiOx electrode exhibits a linear detection range of 0.2 nM to 2 mM for glutamate. This relatively wide concentration range is promising for the analysis of human biological fluids.

Enhancing the catalytic properties of a biochar-supported copper oxide in nitric oxide selective reduction with hydrogen

Enhancing the catalytic properties of a biochar-supported copper oxide in nitric oxide selective reduction with hydrogen

Kinetic Analysis of the Non‐Monotonic Response of Ethene Hydrogenation Rates to Ceria Surface Reduction

AbstractThe precise effect of oxide understoichiometry on bulk oxide catalytic properties continues to remain a subject of intense investigation. Of specific interest in this regard is the role of oxygen vacancies present on bulk ceria catalysts that have recently been reported to represent a more cost‐effective alternative to the more toxic and expensive catalysts used industrially for the selective hydrogenation of acetylene to ethylene. Contrasting claims as to the effect of surface reduction on hydrogenation rates exist in the open literature, with vacancy formation attributed, in separate studies, either a favorable or a deleterious role in effecting hydrogenation turnovers. We report here the non‐monotonic behavior of ethene hydrogenation rates that subsumes both of these trends as a function of degree of surface reduction over a sufficiently large range of pre‐reduction temperatures. Steady state transient kinetic and isotopic exchange data combined with in‐situ titration experiments suggest that this non‐monotonic trend can be attributed not to a change in either the kinetic relevance of specific elementary steps or the hydrogenation mechanism, but rather to site requirements that stipulate the need for two distinct, proximal sites. We also show that the sensitivity of hydrogenation rates to surface reduction can be altered by varying ceria surface termination, with the more open (110) and (100) surfaces exhibiting a less asymmetric effect of surface reduction on ethene hydrogenation rates.

Delafossite CuGaO2-Based Chemiresistive Sensor for Sensitive and Selective Detection of Dimethyl Disulfide.

Dimethyl disulfide (DMDS) is a common odor pollutant with an extremely low olfactory threshold. Highly sensitive and selective detection of DMDS in ambient humid air background, by metal oxide semiconductor (MOS) sensors, is highly desirable to address the increased public concern for health risk. However, it has still been a critical challenge up to now. Herein, p-type delafossite CuGaO2 has been proposed as a promising DMDS sensing material owing to its striking hydrophobicity (revealed by water contact angle measurement) and excellent partial catalytic oxidation properties (indicated by mass spectroscopy). The present CuGaO2 sensor shows a selective DMDS response, with satisfied humidity resistance performance and long-term stability at a relatively low operation temperature of 140 °C. An ultrahigh response of 100 to 10 ppm DMDS and a low limit of detection of 3.3 ppb could be achieved via a pulsed temperature modulation strategy. A smart sensing system based on a CuGaO2 sensor has been developed, which could precisely monitor DMDS vapor in ambient humid air, even with the presence of multiple interfering gases, demonstrating the practical application capability of MOS sensors for environmental odor monitoring.

Monodispersed ZIF-67 in situ nucleated on CoAl-LDH nanosheets for efficient carbamazepine degradation via activation of peroxymonosulfate

Abundant exposed ligand-unsaturated sites of Co have been found to enhance the catalytic oxidation property of ZIF-67 material for peroxymonosulfate (PMS) catalysis. Nevertheless, serious stacking of ZIF-67 still poses a challenge to its application. Herein, we employed a specific in situ growth strategy to establish an LDHNS@ZIF-67 composite based on morphology modulation and performance optimization for carbamazepine (CBZ) degradation. ZIF-67 crystals were successfully grown in situ via nucleating on the CoAl-LDH nanosheets (LDHNSs) substrate surface, which facilitated the crystals’ dispersion. LDHNS@ZIF-67 (0.1 M) was optimized to display outstanding PMS catalytic activity for CBZ degradation, with almost 100% degradation in 5 min (PMS dose, 0.2 mM, catalyst dose, 25 mg/L, and CBZ concentration, 5 ppm). Quenching and electron paramagnetic resonance (EPR) tests confirmed that both radical substances (SO4•-) and nonradical substances (1O2) dominated the reaction system. As the active site, Co(II) ions on the LDHNS@ZIF-67 (0.1 M) surface effectively promoted active substance formation. The intermediate degradation products and pathways for CBZ were investigated. Toxicity assessment for CBZ and its intermediates was conducted. This work will broaden the application of ZIF-67 materials in advanced oxidation process design based on persulfate.

VOx@ graphene electro-catalysts for water splitting and dopamine sensing

Vanadium oxide@graphene (VOG) composites were synthesized using facile hydrothermal method by varying the synthesis time from 6 to 24 h. The samples with best catalytic characteristics were reprepared by replacing graphene oxide with N-doped graphene in the initial hydrothermal reaction. The role of graphene/N-doped graphene in determining the catalytic properties of vanadium oxide was effectively studied using various characterizations viz. X-ray diffraction, Fourier Transform Infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Maximum hydrogen evolution reaction (HER) activity with high current density of –31.07 mA/cm2 (Tafel slope = 162 mVdec−1) has been achieved for VONG-24 sample, indicating Volmer reaction as rate determining step. The high electrochemical surface area (ECSA) of VOG-24 sample in 1 M KOH corroborated the enhanced current density of 144.90 mA/cm2 (Tafel slope = 83 mVdec−1) for maximum oxygen evolution reaction (OER) activity. The VOG12/GCE sample with a 0.29 μM limit of detection (LOD) proved to be the best electrochemical sensor for dopamine (DA) in a wide linear detection range i.e., 1–150 μM. Both catalytic as well as sensor responses of VOG samples were deeply influenced by the amount of O-species along with relative ratios of the V3+, V4+ and V5+. The nature of the graphene in the initial mixture emerged as a crucial parameter in tailoring the vanadium valence state content in the composites.

CHEMISORPTION-CATALYTIC PROPERTIES OF ZINC OXIDE IN THE PROCESS OF REDUCTION OF PROPYL MERCAPTAN

In this work, the adsorption and catalytic properties of zinc oxide, which it exhibits in the process of desulfurization of propyl mercaptan, are studied. It is shown that zinc oxide obtained by ammonia-carbonate technology has a specific surface area of 40.34 m2/g. Nitrogen adsorption-desorption isotherms refer to type IV according to the IUPAC classification, which is typical for mesoporous materials. The calculation of the pore size distribution shows that ZnO contains pores with a diameter of 2 to 40 nm. The characteristics of the chemisorption-catalytic activity of zinc oxide are given. It has been established that during the catalytic reduction of C3H7SH with hydrogen, the formation and absorption of H2S with the formation of zinc sulfide occur. In this case, depending on the time of operation, there is a gradual decrease in the average size of crystallites of the ZnO phase and an increase in the size of crystallites of the zinc sulfide phase. The study of catalytic activity in the hydrogenation reaction of propyl mercaptan with hydrogen was studied during the full cycle of ZnO operation at temperatures of 350 and 400 °C in a flow-type installation. The stages of the process of interaction of the components of the gas mixture (propyl mercaptan and hydrogen sulfide) with zinc oxide are revealed. It is shown that in the initial period of ZnO operation, intense absorption of hydrogen sulfide occurs with the formation of a zinc sulfide phase. The appearance of hydrogen sulfide at the outlet of the catalytic reactor is fixed after 100-200 min of operation. The second stage is characterized by a rapid increase in the concentration of hydrogen sulfide at the outlet of the catalytic reactor with a simultaneous decrease in the concentration of propyl mercaptan. The third stage occurs after 450-550 min of operation and is characterized by the constancy of the composition of the gas mixture at the outlet of the reactor.

Dual Pt atoms stabilized by an optimized coordination environment for propane dehydrogenation

Tailoring atomically dispersed catalysts by various methods has been the subject of intense current research in heterogeneous catalysis. In this work, the structural stability and propane dehydrogenation performance of Pt-TiO2 catalysts with single, dual, and triple Pt atoms doped on the reduced TiO2 surface have been examined. Experimental results indicate the atomically dispersed Pt is thermally very stable and shows exceptionally high activity (TOFpropane = 4.93 s−1) and selectivity (∼98.5 %) for the dehydrogenation reaction. The recently developed machine-learning-based SSW-NN method is then employed to explore the global potential energy surface of the atomically dispersed Pt atom-doped TiO2, which suggests that the single and dual Pt atoms can be tightly held by the vacancies created on the reduced transition-metal oxide, as confirmed by DFT + U calculated energetics. After that, advanced characterization techniques are used in conjunction with microkinetic analysis to establish the quantitative structure–activity relationships. It is found that the dual-Pt-atom structure with two Pt atoms embedded in adjacent Ti and O vacancies is the only active ensemble that dramatically promotes the CH bond activation and hydrogen recombination, as compared to single Pt atoms accommodated by either Ti or O vacancies. These results provide new and direct evidence in support of the idea that specific function can be imparted to specific active sites by tuning their coordination environments, which makes it possible to tailor the catalytic properties of metal oxides to a particular reaction such as propane dehydrogenation.

Effect of Mn2+ substitution on catalytic properties of Fe3-xMnxO4 nanoparticles synthesized via co-precipitation method

Mn-substituted magnetite samples Fe3-xMnxO4 (x = 0.0; 0.02; 0.05; 0.1; 0.15; 0.2; 0.25) were synthesized using the co-precipitation method. X-ray diffraction patterns confirmed the formation of pure, well-crystallized manganese ferrite with a cubic spinel structure. The crystallites size increases sharply for the minimum degrees of substitution, with a subsequent tendency to decrease with the growth of manganese ions content. The catalytic properties of Fe3-xMnxO4 were investigated for the degradation of oxytetracycline (ОТС) and inactivate E. coli. There is a correlation between particle size and catalytic activity. The Fe2.95Mn0.05O4 sample exhibited the highest catalytic activity in the destruction of OTC. The effect of electromagnetic heating (EMH) on the catalytic properties of iron oxides were investigated. The Fe2.9Mn0.1O4 sample with electromagnetic heating achieved 100 % efficiency in decomposing 5 mg/L of OTC. Fe3-xMnxO4 samples reduce the number of Gram-negative bacteria E. coli at concentrations of 104 and 106 CFU/mL. Electromagnetic heating experiments demonstrated high performance, achieving inactivation of 6 logs of E. coli in the presence of Fe2.98Mn0.02O4 and Fe2.95Mn0.05O4 catalysts within 135 minutes. Studies on ecotoxicity have shown that Daphnia magna is a sensitive bioindicator of residual H2O2 concentration. An increase in the Mn2+ content in the synthesized catalysts resulted in a decrease in the toxicity of purified water. The study suggests that Mn-substituted magnetite catalysts are effective materials for catalytic decomposition of OTC and inactivation of E. coli bacteria.

Synthesis of Mixed La–Al Oxides by Treatment in a Water Fluid Medium and Their Catalytic Properties in Methane Oxidation

Synthesis of Mixed La–Al Oxides by Treatment in a Water Fluid Medium and Their Catalytic Properties in Methane Oxidation

Catalytic oxidation properties of 3D printed ceramics with Bouligand structures

Catalytic oxidation properties of 3D printed ceramics with Bouligand structures

Ethanol-Coordinated Dioxidomolybdenum(VI) Complexes with Aroylhyrazone Ligands: Synthesis, Spectroscopic Characterization, Crystal structures and Catalytic Oxidation Property

Two new dioxidomolybdenum(VI) complexes, [MoO2L1(EtOH)] (1) and [MoO2L2(EtOH)] (2), derived from the aroylhydrazone ligands N’-(2-hydroxyl-3-methoxybenzylidene)-3-methylbenzohydrazide (H2L1) and 4-fluoro-N’-(2-hydroxylbenzylidene) benzohydrazide (H2L2), respectively, were prepared in ethanol under ambient temperature. Both complexes were characterized by elemental analysis, IR and UV-Vis spectroscopy, as well as single crystal X-ray determination. The Mo atoms in the complexes are in octahedral coordination. Crystal structures of the complexes are stabilized by hydrogen bonds. The catalytic property for epoxidation of styrene by both complexes was studied.

Hydrogen production from biomass via moving bed sorption-enhanced reforming: Kinetic modeling and process simulation

This study explored a process intensification approach for hydrogen production through biomass gasification. Sorption-enhanced reforming (SER) in an autothermal countercurrent moving bed reformer is proposed as an alternative to multiple units traditionally required for syngas conditioning. This process utilizes the selective sorption and catalytic properties of calcium oxide to integrate multiple reforming reactions into a moving bed reactor. A multistage kinetic model was used to analyze and optimize the key operating parameters of the reformer. Results showed that the moving bed reformer completely converts all tars and increases the hydrogen concentration of syngas from 23 mol% to 80 mol% (dry basis). A comparison between equally sized models showed that the moving bed reformer outperforms a fluidized bed reformer under similar conditions. Simulation of the entire process showed that the hydrogen yield of the proposed SER process is 5% higher than the conventional process. In addition, the proposed process produces surplus electricity, while the conventional process has a 26% power deficit. The overall efficiency of the proposed process is 3.5% higher than the conventional process. The improved process efficiency, coupled with the potentially lower costs of a streamlined process, indicates that the proposed process is a promising route for green hydrogen production.