Formation Of Active Species Research Articles

Mechanistic Study of Asymmetric Alkynylation of Isatin-Derived Ketimine Mediated by a Copper/Guanidine Catalyst.

In this work, we performed a mechanistic study of asymmetric alkynylation of isatin-derived N-Boc ketimine that was first reported by Feng, Liu, and co-workers (Chem. Commun. 2018, 54, 678-681). Guanidine-amide promoted the formation of highly nucleophilic copper acetylene species by abstracting the terminal proton of phenylacetylene with an imine moiety. The guanidinium salt-Cu(I) complex was the most active species in the addition of the C═N bond, in which copper acetylene coordinated to the O atom of the amide moiety, and the isatin-derived ketimine substrate was activated by hydrogen bonding as well as tert-butoxycarbonyl···Cu(I) coordination. Due to weak interaction between Cu(I) and the Ph group in the amide of guanidine, as well as the repulsion between the tert-butyl group in ketimine and the cyclohexyl group in guanidine, the copper acetylene preferred to attack isatin-derived ketimine from the re-face, leading to the S-configuration product with excellent stereoselectivity. The affinity of the counterion for the Cu(I) center in the copper salt affected the deprotonation of phenylacetylene and the formation of guanidinium salt active species. In contrast to CuBr and CuCl, the combination of CuI with aniline-derived guanidine-amide exhibited high catalytic activity and a chiral induction effect, contributing to a high turnover frequency (9.70 × 10-4 s-1) in catalysis and ee%.

Plasmon-promoted oxygen evolution catalysis with Ag nanocrystals loaded α-Co(OH)2 nanosheets

Exploration of low-cost and high efficiency oxygen evolution reaction (OER) electrocatalysts is very important for the large-scale industrial application of alkaline water splitting driven by electricity. The present promising cobalt-based catalysts still leave room to meet the activity requirement. Here, a composite catalyst of α-Co(OH)2/Ag was synthesized by a simple photochemical deposition route, which was designed to improve the electrocatalytic activity for OER. Moreover, a photoinduced surface plasmon on Ag particles was found to further enhance the catalytic performance under low power of laser irradiation. Loading of silver nanocrystals on α-Co(OH)2 nanosheets can decrease the overpotential towards OER for 10 mA cm−2 from 320 to 288 mV, this value can be further decreased of 45 mV under 1000 mW of laser irradiation with a wavelength of 532 nm. The derivation of the catalyst during the OER process was examined, which indicates the structural transformation from α-Co(OH)2 to CoOOH. The photoinduced surface plasmon modulates the electronic structure of cobalt sites, facilitates the formation of active cobalt species, and induces the enhancement of catalytic activity. These findings may give some hints for plasmon-induced electrocatalysis and the design of advanced electrocatalysts.

Effect of ferric ions on surface sulfidization of hemimorphite and implications for xanthate adsorption

• Addition of Fe 3+ weakened the surface activity of hemimorphite. • The sulfidization of hemimorphite was depressed in the presence of Fe 3+ . • Adsorption of xanthate on hemimorphite surfaces was hindered by Fe 3+ . The existence of ferric ions (Fe 3+ ) in the pulp solution will severely affect the surface properties and flotation performance of targeted minerals, so its specific effect on the interaction of flotation reagents with the mineral surface must be understood. In this work, the effect of Fe 3+ on the surface sulfidization of hemimorphite was investigated, and the interaction mechanism of Fe 3+ with the hemimorphite surface was clarified. The results of time-of-flight secondary-ion mass spectrometry and X-ray photoelectron spectroscopy indicated that the addition of Fe 3+ before sulfidization generated Fe–OOH species and hindered the formation of active sulfide species on hemimorphite particles. Infrared spectroscopy and contact-angle measurements showed that the addition of Fe 3+ was detrimental to the adsorption of xanthate species on hemimorphite particles, prohibiting the formation of hydrophobic hemimorphite surfaces in the Fe 3+ –sulfidization–xanthate system. Thus, the presence of Fe 3+ in the pulp of hemimorphite was not conducive to the formation of the desired sulfidization products and stable adsorption layers of xanthate on its surface, resulting in unsatisfactory floatability of zinc oxide minerals containing hemimorphite.

Hierarchical heterostructure consists of Al3+ doped NiFe2O4 nanocubes on NiCo2O4 nanosheets for efficient electrocatalytic water splitting

Spinels are advanced electrocatalysts for oxygen evolution reaction (OER) due to oxophilic properties, however, their research in the field of hydrogen evolution reaction (HER) or overall water splitting (OWS) is rarely reported. In this paper, a hierarchical heterostructure electrocatalyst consists of Al3+ doped NiFe2O4 nanocubes on NiCo2O4 nanosheet arrays (A-NCO@NFO/NF) was successfully prepared for electrocatalytic OWS. The preparing strategy is conducting [Fe(CN)6]3− anion exchange and Al3+ cation doping of NiCo(OH)x grown on nickel foam (NF) accompanied by subsequent air calcination. HRTEM confirmed that the successful formation of NCO/NFO heterointerface and the incorporation of Al3+ into the lattices of NCO and NFO. XPS indicated that the NCO/NFO heterojunction promotes the electron transfer from Ni to Fe, which is favorable for the adsorption of H+ during the HER process, and the Al3+ facilitates the electron transfer from Fe to Co, which is favorable for the formation of CoOOH active species during the OER process. The HER and OER overpotentials of the electrocatalyst are only 178 mV and 159 mV, respectively, and a current density of 10 mA cm−2 can be achieved with only 1.61 V applied during the OWS process, also with excellent stability for 25 h. This study provides a new idea for designing spinel-based green composite electrocatalysts.

Computational Exploration of the Synergistic Anticancer Effect of a Multi-Action Ru(II)-Pt(IV) Conjugate.

An in-depth computational study of the ability of a recently proposed multi-action Ru(II)–Pt(IV) conjugate to act as a photosensitizer in photodynamic therapy (PDT) and chemotherapeutic drugs is presented here. The investigated complex is characterized by a polypyridyl Ru(II) chromophore linked to a Pt(IV) complex that, acting as a prodrug, should be activated by reduction releasing the Ru-based chromophore that can absorb light of proper wavelength to be used in PDT. The reaction mechanism for active species formation has been fully elucidated by means of density functional theory and its time-dependent extension. The reduction mechanism, assisted by ascorbate, of the Pt(IV) prodrug to the Pt(II) active species has been explored, taking into consideration all the possible modes of attack of the reductant for releasing the axial ligands and affording active cisplatin. Given the similarity in the photophysical properties of the chromophore linked or not to the Pt(IV) complex, both the Ru(II)–Pt(IV) conjugate precursor and the Ru(II) chromophore should be able to act as PDT photosensitizers according to type I and type II photoprocesses. In particular, they are able to generate singlet oxygen cytotoxic species as well as auto-ionize to form highly reactive O2–• species.

Inorganic Salts and Dehydrating Agents Cooperatively Promoted Ru-Catalyzed Ethylene Methoxycarbonylation Using CO2 as a CO Surrogate

The use of CO2 as a CO surrogate for the carbonylation of olefin has attracted considerable attention due to its abundance, readily availability, nontoxicity, and recyclability. In this work, we describe the synthesis of methyl propionate (MPA), a key intermediate for methyl methacrylate in the commercial Lucite Alpha process, by the ruthenium-catalyzed methoxycarbonylation of ethylene with CO2 as a carbonyl source. An efficient approach to producing MPA has been developed by adding metal halide promoters and dehydrating agents. Control experiments suggest that the NHC-Ru-hydride may be the real active species formed in situ by the reaction of Ru3(CO)12 with ionic liquid (IL). NMR data demonstrate that inorganic salts favor the formation of active species, which is an important issue for their promotion effect. In terms of the strategy to overcome chemical equilibrium by the addition of dehydrating agents and IL participation in the formation of NHC-Ru-hydride active species, a tasked IL containing a siloxyl group was employed to Ru-catalyze the methoxycarbonylation of ethylene, which showed higher catalytic efficiency in comparison to IL without a siloxyl group.

Investigation of La0.6Sr0.4Co1-xNixO3-δ (x=0, 0.2, 0.4, 0.6, 0.8) catalysts on solid oxide fuel cells anode for biogas dry reforming

The introduction of catalyst on anode of solid oxide fuel cell (SOFC) has been an effective way to alleviate the carbon deposition when utilizing biogas as the fuel. A series of La0.6Sr0.4Co1-xNixO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8) oxides are synthesized by sol-gel method and used as catalysts precursors for biogas dry reforming. The phase structure of La0.6Sr0.4Co1-xNixO3-δ oxides before and after reduction are characterized by X-ray diffraction (XRD). The texture properties, carbon deposition, CH4 and CO2 conversion rate of La0.6Sr0.4Co1-xNixO3-δ catalysts are evaluated and compared. The peak power density of 739 mW cm−2 is obtained by a commercial SOFC with La0.6Sr0.4Co0.4Ni0.6O3-δ catalyst at 850 °C when using a mixture of CH4: CO2 = 2:1 as fuel. This shows a great improvement from the cell without catalyst for internal dry reforming, which is attributed to the formation of NiCo alloy active species after reduction in H2 atmosphere. The results indicate the benefits of inhibiting the carbon deposition on Ni-based anode through introducing the La0.6Sr0.4Co0.4Ni0.6O3-δ catalyst precursor. Additionally, the dry reforming technology will also help to convert part of the exhaust heat into chemical energy and improve the efficiency of SOFC system with biogas fuel.

Seacat - Catalysts for Direct Seawater Electrolysis

With current technology, the direct electrolysis of seawater struggles with ACSFRs (active chlorine species formation reactions), including the ClER (chlorine evolution reaction), competing with the formation of gaseous oxygen on the anode side. The corrosive and poisonous chlorine compounds produced in the ClER pose a significant issue, essentially destroying the electrolyser in a short period of time. Since the purification of seawater requires both energy and increased investment and maintenance costs, today water electrolysis is often not economically feasible in regions with no fresh water access.This marks the starting point of this PhD project. The primary goal of this thesis is the development and demonstration of a catalyst suitable for direct electrolysis of seawater to hydrogen and oxygen, without the formation of Cl2.Nickel based layered double hydroxides (Ni-LDH) and oxyhydroxides (Ni-OOH), particularly when doped with other transition metals, have shown very high catalytic activity with respect to the OER. If sufficient current densities under practical conditions (1A/cm2, < 80 °C, stable for several thousand hours) below the thermodynamic onset potential of the ClER of around 1.7 V could be reached, an active suppression of the ClER is not necessarily needed.Initially, we investigate potential highly active mixed-metal LDH catalysts for the OER in sea water splitting, which are synthesized by a particularly simple, quick and efficient procedure proposed by Li et al. in 2020. Based on their work, we conduct a screening study of 36 unique compounds derived from abundantly available transition metals (Ni, Fe, Mn, Cr, Co, Cu, Zn, Al). The LDHs are coated onto a Ni foam substrate by a two-step dip coating process from metal nitrate solutions. In a first approach, we only consider compounds consisting of two transition metals with equal molar ratios. We then investigate their catalytic activity as well as the long term stability for up to 1000 hours in industrially relevant (60 – 80°C, 6M KOH) fresh water and sea water conditions, particularly regarding catalyst poisoning effects of the sea water constituents on the catalyst.We then give an outlook on the next step in the project, which will be to make use of the simple synthesis procedure by implementing it into an autonomous lab robot setup. The robot platform will comprise all steps of the experiment from synthesis over electrochemical testing, data analysis and machine learning based optimization. This way, we will showcase the potential of combining high-throughput screening with AI-assisted materials discovery. As a proof-of-concept, the robot will reproduce the initial screening study that was carried out manually. Subsequently, autonomous data analysis and synthesis optimization functionality will be implemented and the robot will run several iterations of closed-loop catalyst optimization experiments without human interaction.

Dual Ligand Enabled Nondirected C-H Chalcogenation of Arenes and Heteroarenes.

Chalcogenide motifs are present as principal moieties in a vast array of natural products and complex molecules. Till date, the construction of these chalcogen motifs has been restricted to either the use of directing groups or the employment of a large excess of electronically activated arenes, typically employed as a cosolvent. Despite being highly effective, these methods have their own limitations in the step economy and the deployment of an excess amount of arenes. Herein, we report the evolution of a catalytic system employing arene-limited, nondirected thioarylation of arenes and heteroarenes using a complimentary dual-ligand approach. The reaction is controlled by a combination of steric and electronic factors, and the utilization of a suitable ligand enables the generation of products on a complimentary spectrum to that generated by classical methods. The combination of ligands remains imperative in the reaction protocol with theoretical calculations pointing towards a monoprotected amino acid ligand being crucial in the concerted metalation deprotonation (CMD) mechanism by a characteristic [5,6]-palladacyclic transition state, while the pyridine moiety assists in the active catalyst species formation and product release. Combined experimental and computational mechanistic investigations point toward the C-H activation step being both regio- and rate-determining. Interestingly, oxidative addition of the diphenyl disulfide substrate is found to be unlikely, and an alternative transmetalation-like mechanism involving the Pd-Ag heterometallic complex is proposed to be operative.

Reconstruction of Electronic Structure of MOF-525 via Metalloporphyrin for Enhanced Photoelectro-Fenton Process

Photoelectro-Fenton (PEF) process can continuously promote the occurrence of Fenton reaction and the generation of active species, which is an advanced oxidation technology for pollutant degradation. However, the lack of bifunctional catalysts restricts the development of PEF technology. In this study, the electronic rearrangement MOF-525 modified by metalloporphyrin (named MOF-525-Fe/Zr) was prepared, to load on the carbon felt as a novel cathode catalyst, which is used in PEF process. A series of characterization and photoelectric chemical properties tests combined with DFT calculation showed that the modification of MOF-525 could not only have the large specific surface area and multistage pore structure but also co-stimulate the metal-to-ligand charge transfer (MLCT) and ligand-to-cluster charge transfer (LCCT) by photoelectric synergy. These charge transitions provide periodic electron donor-acceptor conduction paths in MOF-525-Fe/Zr, which can improve the active species formation and transfer efficiency. Owing to their favorable pore and electronic structure as well as stability, MOF-525-Fe/Zr shows great promise for the application in the catalytic process of PEF. Sulfamethoxazole (SMX) degradation was enhanced by MOF-525-Fe/Zr with the TOC removal rate above 75% both in river water and tap water. Finally, the reasonable pathway of PEF catalytic degradation of SMX was proposed by HPLC-MS analysis. In conclusion, this study provides a new idea for reconstructing the electronic structure of MOFs catalyst and broadening the practical application of PEF technology.

Hydrophobic interaction of V12 bowl-type dodecavanadates with alkyl ammonium cations

The V12 dodecavanadate, [V12O32]4−, that is one of a dominant polyoxovanadate species in non-aqueous media, was investigated focusing on the interaction of alkyl chains on its counter cations. Although the presence of such a species is not reported in any biological system, the unique V12 bowl anions have exhibited a host-guest property to accommodate a biologically active anion such as a halide, a cyanide or an azide for its delivery to the system. The nonpolar interactions between alkyl chains and the surface oxygen atoms on the V12 is of significance in the host-guest property and the reactivity of the V12. In the solid state, a tetraethyl ammonium (TEA) cation approached 3 Å above the cavity of the V12 via non-covalent interaction showing the lid effect. This interaction induces a distortion of its flexible framework even in a solution state. From the solution state 51V NMR and IR spectra, the orientation of an azide in the cavity was altered between TEA and tetra-n-butyl ammonium (TBA) salts. The modification of the non-covalent interaction also affected an oxidative catalytic performance with H2O2. The rate of the formation of active species of a TEA salt of [V12O32(Br)]5− was shorter than that of a TBA salt.

Tailoring the local environment of silver in SSZ-13 zeolites for low-temperature catalytic oxidation of ammonia

Supported Ag catalysts have shown great potential in selective catalytic oxidation of ammonia (NH3-SCO) for the depletion of harmful ammonia emissions. However, the lack of effective ways to control the proportional population of active Ag species in/on the support has been the major limitation to their catalytic performance. Herein, the electronic properties, stability, and dispersion of Ag species were rationally tuned by tailoring the micro-environment of SSZ-13 zeolite supports. The influence of the local environment of Ag species in SSZ-13 on their catalytic behavior during NH3-SCO reaction was extensively investigated by comprehensive characterizations. Results obtained have shown that SSZ-13 (31s) with moderate ion-exchange sites, a large external surface area and abundantly accessible defect sites are beneficial to the stabilization and dispersion of the Ag active sites which trigger the formation of plentiful active Ag0 species. The Ag0 species are immobilized on SSZ-13(31s) with high metal dispersion which facilitates the activation of oxygen and the dehydrogenation of adsorbed NH3, thus exhibiting excellent low-temperature activity and hydrothermal stability in the NH3-SCO reaction. This work deepens the understanding on the effect of support towards the engineering of active metal species and provides a facile strategy for the preparation of highly efficient metal-based catalysts.

Synergistically enhanced solar light‐driven degradation of hazardous food colorants by ultrasonically derived MgFe2O4/S‐doped g‐C3N4 nanocomposite: A Z‐scheme system‐based heterojunction approach

Magnesium ferrite/sulfur‐doped graphitic nitride (MFO/SCNNS) heterostructure has been developed via sonication‐assisted deposition of zero‐dimensional MFO over the surface of two‐dimensional SCN nanosheets. Additionally, the prepared nanocomposite material has been characterized by several analytical characterization techniques including XRD, Fourier transform infrared (FT‐IR), high‐resolution transmission electron microscopy (HR‐TEM), selected‐area electron diffraction (SAED), energy‐dispersive spectrometry (EDS), Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM), UV–Vis. spectroscopy, electron spin resonance(ESR), and X‐ray photoelectron spectroscopy (XPS) which indicated the existence of strong interfacial interactions via heterojunction formation between MFO and SCNNS. The as prepared nanocomposite, especially MFO:SCNNS (1:1) (having 1:1 mass ratio of MFO to SCNNS), offered impressive photo‐response for the complete degradation of Erythrosine B and Indigo Carmine within 30 min under direct solar light irradiation. The enhanced photoactivity of the MFO:SCNNS (1:1) was also confirmed by the photoluminescence, photocurrent and electrochemical impedance spectroscopy. The Mott–Schottky analysis also depicts the formation of p‐n heterojunction at the interface of MFO and SCNNS, responsible for the enhanced photoactivity. Additionally, the degradation process has also been studied using mass spectrometry, UV–Vis, and ESR spectral analysis. The trapping experiments were also conducted to confirm the formation of active radical species during the photodegradation reaction. Furthermore, the nanocomposite photocatalytic material offered excellent stability and reusability and thus can serve as an effective candidate for environmental remediation application such as real waste water treatment.

Exceptional middle latitude electron precipitation detected by balloon observations: implications for atmospheric composition

Abstract. Energetic particle precipitation leads to ionization in the Earth's atmosphere, initiating the formation of active chemical species which destroy ozone and have the potential to impact atmospheric composition and dynamics down to the troposphere. We report on one exceptionally strong high-energy electron precipitation event detected by balloon measurements in geomagnetic midlatitudes on 14 December 2009, with ionization rates locally comparable to strong solar proton events. This electron precipitation was possibly caused by wave–particle interactions in the slot region between the inner and outer radiation belts, connected with still poorly understood natural phenomena in the magnetosphere. Satellite observations of odd nitrogen and nitric acid are consistent with widespread electron precipitation into magnetic midlatitudes. Simulations with a 3D chemistry–climate model indicate the almost complete destruction of ozone in the upper mesosphere over the region where high-energy electron precipitation occurred. Such an extraordinary type of energetic particle precipitation can have major implications for the atmosphere, and their frequency and strength should be carefully studied.

Coking- and Sintering-Resistant Ni Nanocatalysts Confined by Active BN Edges for Methane Dry Reforming

Methane dry reforming (MDR) has attracted significant attention for effectively consuming greenhouse gases and producing valuable syngas. The development of coking- and sintering-resistant catalysts is still a challenge. Herein, highly active Ni nanocatalysts confined by the active edges of boron nitride have been originally developed, and the coking- and sintering-resistant MDR mechanism has also been unraveled. The active edges of boron nitride consisted of boundary BOx species interact with Ni nanoparticles (NPs), which can contribute to the activation of both CH4 and CO2. The etching of BN is restrained under the buffer of boundary BOx species. Operando spectra reveal that the formation and conversion of active bicarbonate species is accelerated by the boundary BOx species. The complete decomposition of CH4 is suppressed, and thus the coke formation is restricted. The functional groups of active BN edges are confirmed to stabilize the Ni NPs and facilitate the MDR reaction. This work provides a novel approach for the development of coking- and sintering-resistant catalysts for MDR.

Toward enhanced oxygen evolution on NaBH4 treated Ba0.5Sr0.5Co0.8Fe0.2O3−δ nanofilm: Insights into the facilitated surface reconstruction

The oxygen evolution reaction (OER) is the main obstacle to overall water splitting and therefore the focus of recent research. Perovskite oxides have been regarded as promising OER catalysts due to their superior activity and compositional flexibility. In this work, a nanofilm of Ba0.5Sr0.5Co0.8Fe0.2O3−δ deposited on nickel foam (BSCF-NF) was fabricated by pulsed laser deposition (PLD), and the real-time dynamic surface change was observed by in situ Raman spectroscopy. In addition, a surface reductive strategy is applied to BSCF-NF, which is then demonstrated to facilitate the formation of active species on B-site cations, resulting in enhanced OER activity. The reconstruction activation potential of BSCF-NF is reduced after the reductive treatment. The correlation between surface electron structure and catalytic activity is established and discussed. This work provides not only a facile strategy for promoting the formation of active species but also an in-depth understanding of the fundamental processes of surface reconstruction and the origins behind the improved OER performance for perovskite catalysts.

Electronic Metal-Support Interactions Between CuxO and ZnO for CuxO/ZnO Catalysts With Enhanced CO Oxidation Activity.

Metal-support interaction has been one of the main topics of research on supported catalysts all the time. However, many other factors including the particle size, shape and chemical composition can have significant influences on the catalytic performance when considering the role of metal-support interaction. Herein, we have designed a series of CuxO/ZnO catalysts as examples to quantitatively investigate how the metal-support interaction influences the catalytic performance. The electronic metal-support interactions between CuxO and ZnO were regulated successfully without altering the structure of CuxO/ZnO catalyst. Due to the lower work function of ZnO, electrons would transfer from ZnO to CuO, which is favorable for the formation of higher active Cu species. Combined experimental and theoretical calculations revealed that electron-rich interface result from interaction was favorable for the adsorption of oxygen and CO oxidation reaction. Such strategy represents a new direction to boost the catalytic activity of supported catalysts in various applications.

Degradation mechanism of surface hydrophobicity by ferrous ions in the sulfidization flotation system of smithsonite

Metal ions commonly exist in the flotation pulp, which will affect the mineral surface properties and lead to a change in the mineral floatability. In this work, the effect of Fe2+ on the flotation behavior of smithsonite was investigated, and the interaction mechanism of Fe2+ with the smithsonite surface in the sulfidization flotation system was clarified. The results of microflotation tests showed that the presence of Fe2+ can greatly reduce the flotation recovery of smithsonite. The results of zeta-potential measurement, time-of-flight secondary-ion mass spectrometry, and X-ray photoelectron spectroscopy indicated that addition of Fe2+ before sulfidization generated FeOOH species and hindered formation of active sulfide species on smithsonite. The results of infrared spectroscopy and contact-angle measurement showed that addition of Fe2+ was harmful for adsorption of the collector on smithsonite, and it was difficult to obtain hydrophobic smithsonite surfaces in the Fe2+–sulfidization–xanthate flotation system. Considering the above results, the presence of Fe2+ depressed adsorption of sulfide ions and the collector on smithsonite, making smithsonite show poor floatability, and it was difficult to obtain the ideal flotation recovery of smithsonite.

Enhanced degradation of emerging contaminants by permanganate/quinone process: Case study with bisphenol A

Permanganate (Mn(VII)) is widely used as a mild oxidant in water treatment. However, the reaction rates of some emerging contaminants with Mn(VII) are extremely low. In this study, benzoquinone (BQ), a redox mediator with the important component in dissolved organic matter (DOM), enhanced the oxidation of bisphenol A (BPA) by Mn(VII) in a wide pH range of 4.0-10.0. The redox cycle of BQ would produce semiquinone radicals, which could act as ligands to stabilize the formed Mn(III) in the system to promote the oxidation of BPA. Notably, the presence of BQ might promote the formation of MnO2. A novel mechanism was proposed that singlet oxygen (1O2), Mn(III)-ligands (Mn(III)-L) and in-situ formed MnO2 were the main contributors to accelerate BPA degradation in the Mn(VII)/BQ system. Under acidic conditions, the in-situ formed MnO2 involved in the redox reaction and part of the Mn(IV) was reduced to Mn(III), indicating that the electron transfer of BQ promoted the formation of active Mn species and enhanced the Mn(VII) oxidation performance. Semiquinone radicals generated by BQ transformation would couple with the hydrogen substitution products of BPA to inhibit BPA self-coupling and promote the ring-opening reactions of BPA. Mn(VII)/BQ had better effect in raw water than in pure water, indicating that the Mn(VII)/BQ system has high potential for practical application. This study provided insights into the role of DOM in enhancing the Mn(VII) oxidation in water treatment.

Enhanced recycling performance of bimetallic Ir-Re/SiO2 catalyst by amberlyst-15 for glycerol hydrogenolysis

Abstract Recycling performance of heterogeneous catalysts is of crucial importance especially for a batch reaction system. In this work, we demonstrate a strategy for enhancing recycling performance of Ir-Re/SiO2 catalyst synergized with amberlyst-15 in glycerol hydrogenolysis to produce 1,3-propanediol. Comprehensive characterization results reveal that the Re sites in the Ir-Re/SiO2 catalyst undergo irreversible segregation and oxidation. These hinder the formation of active Re-OH species and thus contribute to a complete and irreversible deactivation. However, the introduction of amberlyst-15 into the reactant mixture can restrain the oxidation process of Re sites and favor the formation of Re-OH species, and thus significantly enhance the catalytic recycling performance. The results demonstrated here could guide the development of excellent bimetallic catalysts with the desirable recycling performances for the reaction.