Active Component Of Catalyst Research Articles

Asymmetric oxygen vacancies of self-supporting Co3O4/CuOx on Cu foam boosts propane total oxidation

As a low-cost and environmentally friendly transition metal oxides material, the Co3O4 has good catalytic activity for volatile organic compounds (VOCs) oxidation. However, the active components of powder cobalt-based catalysts may present uneven distribution and aggregation, thus affecting the catalytic efficiency. Herein, the Co/Cu-CF monolithic catalyst with asymmetric oxygen vacancies was developed through in-situ growth of Cu(OH)2 nanoarrays on Cu foam, which exhibits excellent performance for propane oxidation (T90 at 215 ℃). It is impressive that the catalyst shows satisfactory stability in terms of long-term, cyclic and water resistance. The results indicate that the existence of nanoarrays can provide a rich load surface and better disperse the active components, which effectively facilitates the interface interaction between cobalt and copper, inducing the generation of asymmetric oxygen vacancies. And, the activity of catalyst was significantly improved owing to the double activation effect of asymmetric oxygen vacancy on molecular oxygen and lattice oxygen. Therefore, this research offers a novel approach for designing efficient nanoarray monolithic catalysts for VOCs oxidation and other environmental applications.

Mechanism of the generation of benzaldehyde and benzoic acid on Pd (1 1 1) surface during the destruction of toluene: Verification of experiments and models

Catalytic oxidation technology is still the mainstream technology of VOCs treatment at present, and it is of great significance to study the main active components of catalysts and clarify the evolution and transformation process of intermediate products in the catalytic process for clarifying the reaction mechanism and guiding the catalyst design. Pd was identified as the main active component in catalytic oxidation of toluene, and the important intermediate products in the degradation of toluene, i.e., benzaldehyde and benzoic acid, were obtained through experiment and In-situ DRIFT spectra. However, the specific evolution process of intermediates is difficult to observe experimentally. The conversion of toluene on Pd (111) surface was studied by DFT calculation. Benzaldehyde was the most stable intermediate and benzoic acid was the most stable energy state of the reaction products. Then the activation energies and reaction energies of all possible reaction paths from toluene to benzaldehyde or benzoic acid were calculated, and the only transition state was obtained. Two pathways for the formation of benzaldehyde and benzoic acid were identified, in which the oxidation reaction after dehydrogenation may be the common rate-determining step of the two pathways, with a maximum energy barrier of 0.80 eV.

Progress in Degradation of Volatile Organic Compounds by Catalytic Oxidation: a Review Based on the Kinds of Active Components of Catalysts

Progress in Degradation of Volatile Organic Compounds by Catalytic Oxidation: a Review Based on the Kinds of Active Components of Catalysts

Key Role of Metal Oxide Support in Tuning Active Surface Components of Fe-Based Catalysts for CO2 Hydrogenation

Key Role of Metal Oxide Support in Tuning Active Surface Components of Fe-Based Catalysts for CO₂ Hydrogenation

Synthesis of Eugenol Ethyl Ether by Ethylation of Eugenol with Diethyl Carbonate over KF/γ-Al2O3 Catalyst

A KF/γ-Al2O3 solid base catalyst was prepared by wet impregnation and applied to the synthesis of eugenol ethyl ether (EEE) from eugenol and diethyl carbonate. By measuring the yield of eugenol ethyl ether, we investigated the effects of the catalyst active component, impregnation temperature, KF impregnation concentration, impregnation time, and calcination temperature on catalyst performance. The results showed that the KF/γ-Al2O3 catalyst can adequately facilitate the conversion of eugenol to EEE. The characterizations of the catalysts were examined by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterizations of EEE were examined by nuclear magnetic resonance spectrometry (H1-NMR), gas chromatography–mass spectrometer (GC-MS) and Fourier-transform infrared spectroscopy (FT-IR). It was found that the KF/Al2O3 catalyst (impregnation temperature 60 °C, KF impregnation concentration 40%, impregnation time 8 h, and calcination temperature 450 °C) showed the best effect. The yield of EEE remained 51.2% after recycling the supported catalyst three times.

Exploring the key components of Au catalyst during CO oxidation using TG-MS and operando DRIFTS-MS

Nano-Au has a good catalytic activity for CO oxidation, but its catalytic mechanism is still not clear. Here, CO oxidation on Au2O3 and its thermal decomposition products were studied using thermogravimetric-mass spectrometry (TG-MS) and operando diffuse reflectance infrared Fourier transform spectroscopy-mass spectrometry (DRIFTS-MS) to explore the key active components of Au catalyst for CO oxidation. The TG-MS results showed that Au2O3 decomposed to AuO at 210 °C and Au at 375 °C and was oxidized to form Au oxide above 375 °C. When Au2O3 decomposed into AuxOy (x>y) above 210 °C, the CO oxidation activity obviously increased. Au atoms in the Au-Au system serve as electron donor and CO adsorption sites. Au atom is oxidized to AuO by the O atom from O2 decomposition following the Epling-Xu decomposition mechanism. A schematic diagram of the key components of Au2O3 catalysts during CO oxidation was proposed based on TG-MS and operando DRIFTS-MS analysis results.

Full-crystalline monolithic EU-1 zeolite: sustainable synthesis and its applications in the hydroisomerization of ethylbenzene with meta-xylene

A novel strategy for the effective production of monolithic EU-1 zeolite as an active component of catalyst in C8 hydroisomerization.

Atomic Replacement of PtNi Nanoalloys within Zn-ZIF-8 for the Fabrication of a Multisite CO2 Reduction Electrocatalyst

Exploring the transformation/interconversion pathways of catalytic active metal species (single atoms, clusters, nanoparticles) on a support is crucial for the fabrication of high-efficiency catalysts, the investigation of how catalysts are deactivated, and the regeneration of spent catalysts. Sintering and redispersion represent the two main transformation modes for metal active components in heterogeneous catalysts. Herein, we established a novel solid-state atomic replacement transformation for metal catalysts, through which metal atoms exchanged between single atoms and nanoalloys to form a new set of nanoalloys and single atoms. Specifically, we found that the Ni of the PtNi nanoalloy and the Zn of the ZIF-8-derived Zn1 on nitrogen-doped carbon (Zn1-CN) experienced metal interchange to produce PtZn nanocrystals and Ni single atoms (Ni1-CN) at high temperature. The elemental migration and chemical bond evolution during the atomic replacement displayed a Ni and Zn mutual migration feature. Density functional theory calculations revealed that the atomic replacement was realized by endothermically stretching Zn from the CN support into the nanoalloy and exothermically trapping Ni with defects on the CN support. Owing to the synergistic effect of the PtZn nanocrystal and Ni1-CN, the obtained (PtZn)n/Ni1-CN multisite catalyst showed a lower energy barrier of CO2 protonation and CO desorption than that of the reference catalysts in the CO2 reduction reaction (CO2RR), resulting in a much enhanced CO2RR catalytic performance. This unique atomic replacement transformation was also applicable to other metal alloys such as PtPd.

Artificial formate oxidase reactivity with nano-palladium embedded in intrinsically microporous polyamine (Pd@PIM-EA-TB) driving the H2O2 – 3,5,3′,5′-tetramethylbenzidine (TMB) colour reaction

Surface cavities formed by molecularly rigid polymers of intrinsic microporosity affect catalytic processes. Palladium nanoparticles of typically 3 nm diameter are formed in an intrinsically microporous polyamine (PIM-EA-TB) by borohydride reduction. These particles are shown to indirectly catalyse the oxidative colour change of indicator dye 3,5,3′,5′-tetramethylbenzidine (TMB) in the presence of formic acid via formation of H2O2. Investigation reveals that oxygen reduction on the palladium is rate limiting with optimised H2O2 production at approximately pH 3 to 4, and first order in formate, followed by purely homogeneous TMB oxidation. The H2O2 production is therefore studied separately as a nanozyme-like catalytic process equivalent to formate oxidase reactivity, linked to the molecularly rigid polyamine host (PIM-EA-TB) providing ammonium sites (in molecularly rigid surface cavities) that enhance both (i) 2-electron formate oxidation and (ii) 2-electron oxygen reduction to H2O2. Beneficial effects of hydrophobic ClO4- anions are noted as indirect evidence for the effect of ammonium sites in surface cavities. A computational DFT model for the artificial formate oxidase reactivity is developed to underpin and illustrate the hypothesis of PIM-EA-TB as an active catalyst component with implications for future nanozyme sensor development.

3D spiderweb-like nanowire networks loading single-atom catalysts in capillary array as high-efficiency microreactor

Rapid fluid transport and high reaction efficiency are known as irreconcilable indicators for designing high-performance monolithic microreactors. Here, proceeding from microstructure design and single-atom catalysts (SACs) utilization simultaneously, we developed 3D spiderweb-like nanowire networks in wood capillary array owning high permeability integrated with successfully synthesized SACs as high-efficiency microreactor for organic pollutant removal from water. The 3D spiderweb-like nanowire networks could be obtained by noncovalent and physical entanglement interactions of ultralong and flexible PEG113-b-P4VP104 worm-like micelles forming loosened micro-aerogel in the wood capillary. Abundant nanowire networks in straight microchannels array allow vast quantities of catalyst active component loading sites and greatly increase contact reaction efficiency. Meanwhile, the grid-like porous structure of the nanowire networks preferably maintains good permeability of the wood capillary array. Furthermore, strong coordination interaction of pyridine in P4VP block and confinement effect from core-shell structured worm-like micelles afford uniformly distributed SACs with high density. As a proof of concept, we demonstrate an integration of unique microstructure from 3D spiderweb-like nanowire networks in wood capillary array and well dispersed Pd-N4/Fe-N4 SACs enables high removal efficiency for methylene blue and fast mass transfer for water. Importantly, this work provides a facile and scalable method for atomically dispersed catalysts, paving the way for designing high-performance microreactors in other potentially important reactions.

Heterogeneous catalytic ozonation by amorphous boron for degradation of atrazine in water

As one of the most promising and practical advanced oxidation processes (AOPs), the catalytic ozonation is triggered by the active components of catalyst, which are usually derived from metals or metal oxides. To avoid the metal pollution from catalyst, here the amorphous boron (A-boron) is used as a metal-free catalyst for catalytic ozonation to produce free radicals for effective degradation of atrazine (ATZ), the world-widely used herbicide and also a widespread pollutant in environment. A-boron exhibits an outstanding performance for catalytic ozonation to remove ATZ from water. As A-boron is introduced into ozonation, the degradation efficiency in 10 min is promoted to 97.1%, much higher than that of 15.1% under ozonation. The mechanism is that the B–B bonds and internal suboxide B in A-boron serve as the main active sites to donate electrons to accelerate ozone decomposition to produce reactive oxygen species (ROS), including •O2− and 1O2, and further enhance ATZ degradation via ROS reactions. Moreover, the A-boron is still highly active with a degradation efficiency of ATZ over 95% in 10 min even after four successive cycles. This work shows A-boron could be an alternative for the active components of metal or metal oxide in catalytic ozonation.

Removal of multi-pollutants in flue gas via a new approach based on dielectric barrier discharge coupling MnCu/Ti oxidation

A dielectric barrier discharge (DBD) coupling MnCu/Ti oxidation and postpositioned wet electrostatic precipitator (WESP) system was built. The experimental results showed that WESP can significantly enhance the simultaneous conversion efficiency(ηC) of NO, SO2 and Hg0 by the DBD coupling MnCu/Ti reactor. The best simultaneous removal efficiency(ηR) of NO, SO2 and Hg0 reached 94.5%, 100% and 100%, respectively. The ratio of catalyst active component (Mn/Cu) and catalyst filling amount were optimized. The effects of catalyst active component ratio, filling amount, flue gas component and energy density (SED) on the ηC of NO, SO2 and Hg0 were determined. The effect of sodium humate (HA-Na) in the cleaning water on the ηR was also illustrated. Besides, we clarified the absorption mechanism and how WESP corona discharge oxidized NO, SO2 and Hg0, as well as the removal of NO2, SO2, and SO3 by HA-Na. Product analysis showed that NO2, SO2 and SO3 were converted into NO3- and SO42-, part of HgO was converted into Hg2+ in the cleaning water, and a small amount of Hg(NO3)2 and HgSO4 were converted into Hg2+, NO3- and SO42-.

Preparation of goethite/nickel foam catalyst and its application in xylene degradation

In this paper, the xylene discharged from the chemical industry is taken as the research object. A composite catalyst with nickel foam as catalyst carrier and goethite as active component was prepared. And it was successfully applied to the low-temperature plasma synergistic supported catalyst catalytic for the removal of xylene. The results showed that the total removal efficiency of xylene was as high as 97.11% (from 700 to 20.23 ppm) and the COx selectivity was 87% under the optimal process conditions (calcination time of 5 min, power of 60 W, oxygen flow of 60 mL min−1, goethite loading of 5%). Meanwhile, this technology can efficiently degrade xylene, and the final ideal products are H2O and CO2, and light yellow solid substances including phenol, 1,4-benzoquinone and nitrophenol are produced.

Spectroscopy analysis of the active component of chromia-alumina dehydrogenation catalysts

The Ag1 Raman spectral line was used for the determination of the stress distribution in the active component of chromia-alumina catalysts.

Cu-Al OXIDE NANOCOMPOSITE-BASED EXTERNAL FILTERS FOR GAS PURIFICATION FROM PETROL AUTOMOBILE EXHAUST

Current exhaust gas catalytic converters are expensive as it makes use of precious metals such as Platinum (Pt), Palladium (Pd) and Rhodium (Rh) as active components in conversion catalysts. However, these converters do not convert all toxic gases (e.g.: CO, NOX, HC) into less harmful pollutants, before emitting them to atmosphere, particularly for automobiles with old petrol engines and fuel types (standard unleaded petrol) causing more air pollution. In this work, equimolar Copper – Aluminium oxide-based nanocomposites were synthesised using wet chemical synthesis method and its effectiveness as a catalyst for removal of NOx gas was explored. An external filter with the proposed catalyst was fitted to the tailpipe of a 350-cc petrol engine and the impact on exhaust gas emissions was assessed. Chemical growth, composition of the nanocomposites prepared and the relevant functional properties were characterized using X-Ray Diffraction, Adsorption studies and Gas Chromatography. Nanocomposite was deposited on ceramic substrate, which was then mounted inside housing and connected to the tailpipe for testing. Emission tests were carried out with and without the exhaust filter. A reduction in NOx along with CO and HC components of the exhaust gas by about 45, 33 and 12% respectively was obtained when the proposed nanocomposite was used to treat the tailpipe emissions.

Active Components of Catalysts of Methane Conversion to Synthesis Gas: Brief Perspectives

Methane transformation into more valuable products has attracted extensive attention. Synthesis gas is an important intermediate product in the chemical industry. Several syngas production methods are available, depending on the purpose of the industrial application. A major limitation of the processes is the rapid deactivation of the catalyst, which has been commonly attributed to the sintering of the active sites of catalyst and carbon formations on these sites, induced by methane decomposition and CO disproportionation. The catalyst consists of an active component and support. Ceria-based systems have been extensively employed as the support because of their unique redox properties and high oxygen storage capacity. The most promising approach is to design an excellent active site of the catalyst, based on noble or transition metals. A comparison of perspective active components, especially polymetallic components, is considered here.

Different transfer hydrogenation pathways of halogenated nitrobenzenes catalyzed by Fe-, Co- or Ni-based species confined in nitrogen doped carbon

In this work, by the simple pyrolysis of Fe2+, Co2+ or Ni2+ and 1,10-phenanthroline (Phen) complexes under the presence of activated carbon and dicyandiamide in nitrogen atmosphere, different nonprecious transition metal-based species that well confined in nitrogen doped carbon (M-N-C, M = Fe, Co or Ni) were prepared. The Fe-N-C showed the best catalytic performance for the transfer hydrogenation of halogenated nitrobenzenes. More importantly, through the catalytic results comparison of the three catalysts estimated by gas chromatography-mass spectrometer, two speculations might be presented for the reaction pathway depending on the catalyst used. The transfer hydrogenation reaction route over Fe-N-C might follow the indirect way like the Co-N-C and Ni-N-C. Another assumption was the Fe-N-C might go through the direct pathway in contrast to the Co-N-C and Ni-N-C which resulted in formation of azoxybenzene and azobenzene intermediates before complete conversion to aniline. Those differences were found to be correlated with the different valence states and active metal components in different catalysts. In addition, the optimal Fe-N-C could be efficiently recovered by using an applied magnetic field and reused without significant decrease of activity. Therefor the catalyst may possess important potential for the industrial application in the selective hydrogenation of halogenated nitrobenzenes.

State-of-the-Art Iridium-Based Catalysts for Acidic Water Electrolysis: A Minireview of Wet-Chemistry Synthesis Methods

With the increasing demand for clean hydrogen production, both as a fuel and an indispensable reagent for chemical industries, acidic water electrolysis has attracted considerable attention in academic and industrial research. Iridium is a well-accepted active and corrosion-resistant component of catalysts for oxygen evolution reaction (OER). However, its scarcity demands breakthroughs in catalyst preparation technologies to ensure its most efficient utilisation. This minireview focusses on the wet-chemistry synthetic methods of the most active and (potentially) durable iridium catalysts for acidic OER, selected from the recent publications in the open literature. The catalysts are classified by their synthesis methods, with authors’ opinion on their practicality. The review may also guide the selection of the state-of-the-art iridium catalysts for benchmarking purposes.

Recent Advances in Heterogeneous Catalysis for Ammonia Synthesis

AbstractEven after a century, ammonia (NH3) synthesis from nitrogen and hydrogen through Haber‐Bosch process is still energy intensive. Even with recently introduced second generation Ru based catalysts with superior performance over commercial Fe based catalysts, there is still place for upgrading with new approach using advanced materials in catalyst formulation. The alkali and alkaline metal promoted Ru supported carbon and metal oxide catalyst attracted attention at initial stage and extensively studied for NH3 synthesis in the 20th century. Until recently, advanced materials such as electrides, hydrides, nitrides, oxides and oxy‐hydrides‐nitrides studied as support and active component of catalyst fascinated much attention, with milder reaction conditions for NH3 synthesis. These materials with unique properties of reversible storage of electrons, hydrides, nitrides and oxygen vacancies enrich electron density on Ru catalyst and cleave N≡N bond with very low activation energy (<60 kJ/mol). The mechanistic understanding of these materials leads to the fact that activation N≡N bond is no more rate‐determining step (RDS). Instead, formation of N−H bond is RDS, pushing towards an innovative research directions and scientific basis for development of new catalysts. Enormous maturation of experimental and theoretical methods with improved precession over worldwide research effort helped in gaining a fundamental understanding of these materials in NH3 synthesis. The most of Ru supported on these advanced materials were better in performance compared to benchmark Cs−Ru/MgO and Ru/AC catalysts in NH3 synthesis. Insights on these materials and their mechanism are covered in this review, which digs towards finding a realistic catalyst for NH3 synthesis.

Efficient fenton-like degradation of ofloxacin over bimetallic Fe–Cu@Sepiolite composite

An effective method for increasing the utilization efficiency of active components in heterogeneous Fenton-like catalysts was provided. 1.5 at.% Fe–Cu bimetal on 1D sepiolite (Sep) (D-FeCu@Sep) with high dispersion and reduced chemical valence was prepared via complexation-carbonization process of glutathione. 93% of ofloxacin (OFX, a typical antibiotic of emerging concern) was degraded over D-FeCu@Sep without any extra energy input at the optimum conditions (100 mL 10 mg/L OFX, pH 5.0, 3.0 g/L catalyst and 0.03 M H2O2), which was enhanced by 2.3, 3.0 and 1.7 times compared with aggregated Fe–Cu on Sep (A-FeCu@Sep), monometallic Fe on Sep (D-Fe@Sep) and Fe–Cu on blocky Celite (D-FeCu@Celite), respectively. Moreover, it exhibited an excellent performance at a wide working pH range from acidic to neutral conditions (pH 3.2–7.2) with a satisfied stability. Based on the characterizations of X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H2-TPR) and electrochemical impedance spectroscopy (EIS), the proposed complexation-carbonization process of glutathione played an important role in the good Fenton performance of D-FeCu@Sep. The complexation of Fe and Cu ion by glutathione favors the high dispersion of Fe–Cu active component, afterward the reduced chemical valence results from carbonization process of glutathione. Moreover, the 1D nanofibrous structure of D-FeCu@Sep could greatly increase the surface electron transfer efficiency compared with D-FeCu@Celite. This study provides a method alternative to the heterogeneous Fenton chemistry by increasing the utilization efficiency of active components.