Publisher Correction: A universal principle for a rational design of single-atom electrocatalysts Nat. Catal. Pub Date : 2018-07-20 Haoxiang Xu, Daojian Cheng, Dapeng Cao, Xiao Cheng Zeng
Publisher Correction: A universal principle for a rational design of single-atom electrocatalysts Publisher Correction: A universal principle for a rational design of single-atom electrocatalysts, Published online: 20 July 2018; doi:10.1038/s41929-018-0127-0 Publisher Correction: A universal principle for a rational design of single-atom electrocatalysts
Au25 clusters as precursors for the synthesis of AuPd bimetallic nanoparticles with isolated atomic Pd-surface sites Mol. Catal. Pub Date : 2018-07-21 Atal Shivhare, Robert W.J. Scott
This study documents the synthesis of Al2O3-supported AuPd bimetallic nanoparticles with isolated atomic Pd-surface sites using Au25(SC8H9)18 clusters as starting precursors. Here, previously synthesized thiolate protected AuPd bimetallic clusters were supported on Al2O3 and subjected to thermal and LiBH4 treatments. Extended X-ray absorption fine structure (EXAFS) analysis shows that thermal and LiBH4 treatments of Al2O3 supported AuPd bimetallic clusters result in the formation of AuPd/Al2O3 bimetallic nanoparticles with isolated atomic Pd-surface sites. EXAFS data also shows that Pd atoms present on the surface were still bonded with thiolate stabilizers. Finally, AuPd/Al2O3 catalysts were tested for the hydrogenation of allyl alcohol. Data show that while Au25/Al2O3 materials were inactive for the hydrogenation reaction, Al2O3 supported AuPd bimetallic clusters were catalytically active. The catalytic activity was further enhanced after thermal and LiBH4 treatment and this was attributed to the enhanced access of substrates to surface Pd sites.
Silk fibroin-based hydrogels as a protective matrix for stabilization of enzymes against pH denaturation Mol. Catal. Pub Date : 2018-07-21 Yueying Han, Sihan Yu, Lichao Liu, Shijia Zhao, Tianxiao Yang, Yajing Yang, Yunming Fang, Shanshan Lv
A significant challenge remains to protect proteins (including enzymes) from inactivation against pH. This study investigated stabilization against pH denaturation of carbonic anhydrase (CA) in silk fibroin (SF)-based hydrogels. CA was immobilized into SF-based hydrogels by a Ru(II) mediated photochemical method, giving rise to ∼100% immobilization efficiency and >60% activity of the free enzyme at the optimum pH value of 8. At an unfavorable acidic pH value of 3, the immobilized CA achieved >20% of the initial activity and ∼8% in the second cycle even after 12 h storage, while the free enzyme lost its activity completely. Fourier transform infrared spectroscopy (FTIR) results suggested that the protective effect of the SF-based hydrogels on the pH stability of CA could be attributed to unique structural feature of the SF molecules, enabling strong intermolecular interactions between SF and CA, and thus increasing protein rigidity against pH denaturation. The same approach was applied to lysozyme and xylanase, and achieved protein stabilization of both enzymes at an unfavorable basic pH value of 9. The SF-based hydrogels demonstrated great potential as a promising matrix for protein immobilization against pH denaturation.
Novel catalyst based on mono- and di-vanadium substituted Keggin polyoxometalate incorporated in poly(acrylic acid-co-acrylamide) polymer for the oxidation of sulfides Mol. Catal. Pub Date : 2018-07-20 Romina A. Frenzel, Gustavo P. Romanelli, Luis R. Pizzio
Composite materials based on [PVxW12-xO40](3+x)− with x = 1 or 2 (PVW and PV2W respectively), included in poly(acrylic acid-co-acrylamide) gel (PAACA), were synthesized. The samples were characterized by different techniques such as FT-IR, 31P MAS-NMR, 51V-NMR, XRD, DTA-TGA, UV–vis DRS, and the acidic properties were estimated by means of potentiometric titration with n-butylamine. Samples containing 10, 20 and 30% (w/w) of polyoxotungstovanadate (POTV) were prepared by inclusion of the POTV in the polymer during its synthesis. According to Fourier transform infra-red and magic angle spinning-nuclear magnetic resonance studies, the predominat anion present in the samples is [PVxW12-xO40](3+x)−, and there is no evidence of its decomposition during the synthesis of hybrid materials and the drying step. According to XRD results, these anions are greatly dispersed in the PAACA or present as amorphous phases. UV–vis DRS data reveal that the samples synthesized using POTV with two vanadium atoms (PAACA-PV2W) exhibit lower values of absorption edge energy than those prepared using PVW (PAACA-PVW), which correlates with a higher oxidizing capacity. The potentiometric titration shows strong acid sites of the hybrid materials, and their number increases with the number of vanadium atoms and with the amount of POTV incorporated in the PAACA grid. The hybrid materials prepared by inclusion of POTV during the polymer synthesis exhibit appropriate physicochemical features to catalyze the oxidation of diphenyl sulfide (DPS) to its sulfone employing acetonitrile as solvent H2O2 as a green oxidant. The samples with 30% w/w of POVT, which show higher catalytic performance, are suitable for the DPS oxidation and can be reused without remarkable drop of their catalytic activity. Furthermore, they show high activity as a catalyst in the oxidation reaction of 4,4´-diamino diphenyl sulfide to the corresponding sulfone (dapsone) used for malaria treatment.
Highly photocatalytic activity of porous skeleton structure AlON powder synthesized by CRN under ultraviolet-light irradiation Mol. Catal. Pub Date : 2018-07-20 Jianxin Xu, Yingchun Shan, Xiannian Sun, Jiujun Xu, Hongming Yin, Liang Wang, Weiwei Wang
A large-sized (∼20 μm) pure aluminum oxynitride (AlON) powder characterized by its porous skeleton structure was synthesized by carbothermal reduction and nitridation (CRN) method using α-Al2O3. The photocatalytic performance of the obtained AlON powder was studied under ultraviolet-light in methylene blue (MB) solution. In 40 ml MB solution doped with 30 mg as-synthesized AlON powder, a photogradation efficiency as high as 97% was measured after irradiating 120 min, and 80% MB was mineralized by determining the total organic carbon (TOC) in the solution, i.e., mineralization is the main degradation mode of MB in the solution due to the added AlON powder. Further radical scavenger’s experiments reveal that both h+ and OH were the dominant reactive species in the photogradation process of MB by the AlON powder. It should be pointed out that the specific surface area of the obtained AlON powder is smaller than that of solid small-sized powder (∼800 nm) due to its porous skeleton structure. However, the measured photogradation efficiency of the obtained AlON powder is slightly higher than the reported value, which is mainly attributed to light reflection and scattering within its skeleton. The as-synthesized AlON powder has excellent dispersibility for its large particle size. Moreover, the obtained AlON powder also exhibits high reusability. Therefore, the obtained large-sized porous skeleton structure pure AlON powder is an efficient and promising photocatalyst.
Synthesis of oxygen vacancy-rich black TiO2 nanoparticles and the visible light photocatalytic performance Mol. Catal. Pub Date : 2018-07-20 Lijuan Han, Bitao Su, Gang Liu, Zheng Ma, Xingcai An
The oxygen vacancy-rich black TiO2 (B-TiO2) consisted of compactly and densely stacked nanoparticles was prepared by thermal treatment amorphous Ti(OH)x in vacuum. A series of characterization were used to investigate the structure, light absorption ability and chemical environment of samples. Phenol was used to evaluate the photocatalytic performance of the materials under visible light irradiation. The results show that the removal rate constant of B-TiO2 in visible light reaches to 0.1316 h−1, is the 5.2 times of P25, exhibiting excellent photocatalytic performance. The excellent photocatalytic performance of B-TiO2 possibly results from the large amounts of oxygen vacancies and the special structure. The large amounts of oxygen vacancies expand the visible light scope. And, the compactly and densely stacked nanoparticles aggregation exhibit large specific areas, plentiful pores and high separation efficiency of photogenerated electrons-holes so that the photocatalytic performance of B-TiO2 is enhanced drastically.
Exploring the impact of zeolite porous voids in liquid phase reactions: The case of glycerol etherification by tert-butyl alcohol J. Catal. (IF 6.759) Pub Date : 2018-07-20 C. Miranda, J. Urresta, H. Cruchade, A. Tran, M. Benghalem, A. Astafan, P. Gaudin, T.J. Daou, A. Ramírez, Y. Pouilloux, A. Sachse, L. Pinard
The role of acidity (nature, concentration, strength) and textural properties in the etherification of glycerol with tert-butyl alcohol was studied for a wide range acid catalysts, such as Amberlyst® 15, silica, alumina, silica alumina and four type of zeolite, i.e. FAU, MOR, ∗BEA and MFI. The etherification of glycerol by tert-butyl alcohol is a thermodynamically limited reaction that occurs through a successive reaction sequence and follows an Eley-Rideal type mechanism. We found major evidence that glycerol etherification is not only a function of the amount of Brønsted acid sites, but that it further proceeds via a product shape selectivity mechanism. Indeed, the formation of di-substituted ethers appears at very low conversions for zeolites compared to meso- and macroporous acid catalysts. ∗BEA and MFI zeolites feature similar confining voids and resulting thus in similar intrinsic acid strengths (as proved by n-hexane cracking), but differ in the connectivity (4 vs. 6 channels) and access to these voids (0.54 vs. 0.67 nm), which leads to diffusion issues, notably for the MFI zeolite.
Catalytic performance of phase-pure M1 MoVNbTeOx/CeO2 composite for oxidative dehydrogenation of ethane J. Catal. (IF 6.759) Pub Date : 2018-07-20 Dan Dang, Xin Chen, Binhang Yan, Yakun Li, Yi Cheng
The introduction of cerium oxide to phase-pure M1 MoVNbTeOx with CeO2 loading from 0 up to 90 wt.% results in highly active catalysts for oxidative dehydrogenation of ethane (ODHE). These catalysts are characterized with BET, ICP, XRD, TEM, SEM and XPS techniques and tested for ODHE process. The results show that the increase of active site, V5+, is one of the dominant factors to improve the ethane conversion. In addition, the easier re-oxidation of V4+ to V5+ due to the presence of Ce4+ makes an extra contribution to the increase of turn-over frequency. Among all the catalysts, M1 catalyst with 30 wt.% CeO2 loading obtains the best productivity of 0.69 kgC2H4/kgcat·h while the corresponding performance of phase-pure M1 catalyst is 0.34 kgC2H4/kgcat·h at 400 °C with the contact time of 18.52 gcat·h/molC2H6. It is further demonstrated that M1/CeO2 catalyst (e.g., with 50 wt.% CeO2 as a representative) loading remains highly active after 3 cycles of refreshment in situ, and its crystal structure and surface morphology keep stable compared to the fresh catalyst.
Cobalt-iron (oxides) water oxidation catalysts: Tracking catalyst redox states and reaction dynamic mechanism J. Catal. (IF 6.759) Pub Date : 2018-07-20 Jianfang Meng, Zhenduo Cui, Xianjin Yang, Shengli Zhu, Zhaoyang Li, Kezhen Qi, Lirong Zheng, Yanqin Liang
Developing earth-abundant materials to replace the traditional noble metals in water splitting to meet industrial requirements remains a challenge. Cobalt-iron (oxides) have been widely studied as electrocatalysts for the oxygen evolution reaction (OER), yet our understanding of the OER dynamic reactivity related to the oxidation state changes as well the adsorption energies of surface species on the metal surface linked to the water oxidation are not well-documented. In this work, a facile chemical reduction process is developed for preparation of Co-only, Co3Fe7 alloy, and Fe-only catalysts. We use X-ray photoelectron spectroscopy (XPS) and in-situ X-ray absorption spectroscopy (XAS) to evaluate metal valences and the dynamics of the oxidation state changes of the electrocatalysts in 0.1 M KOH solution, which disclose that about 20% of the Co centers get oxidized in Co-only from the oxidation state of +2 to +3/+4, while only 1% reach to +3 valence for the Co3Fe7 catalyst under cyclic voltammetry (CV) operation. The small edge changes of Fe centers in Fe-only result in negligible changing the oxidation state. Density-functional theory (DFT) calculation predicts the mechanism of OER performance, which indicates that the OER activity largely relies on the metal oxidation states on the surface of catalysts. Co3O4 on the surface of Co-only catalyst presenting the most positive d-band center and the fewest eg electron contributes to the highest OER activity. Fe-only coated by γ-Fe2O3 shows the lowest OER performance due to the weakest oxygen adsorption energy of γ-Fe2O3 as well as the poor electrical conductivity of FeOOH evolved after operation. Co3Fe7 exhibiting medium OER activity is aroused by the co-existence of CoO and γ-Fe2O3, wherein Co2+ is less active than Co3+. Introducing Fe in Co matrix could depress the formation of Co cations with high oxidation state in as-prepared catalysts, which is not favorable for oxygen production.
Influence of confining environment polarity on ethanol dehydration catalysis by Lewis acid zeolites J. Catal. (IF 6.759) Pub Date : 2018-07-19 Jason S. Bates, Rajamani Gounder
Lewis acidic Sn centers isolated within Beta zeolite frameworks catalyze bimolecular ethanol dehydration to diethyl ether, yet with kinetic behavior sensitive to the hydrophobic character of their confining microporous voids. Sn sites in open ((HO)-Sn-(OSi)3) and closed (Sn-(OSi)4) configurations, quantified from infrared spectra of adsorbed CD3CN before and after reaction, convert to structurally similar intermediates during ethanol dehydration catalysis (404 K) and revert to their initial configurations after regenerative oxidation treatments (21% O2, 803 K). Dehydration rate data (404 K, 0.5–35 kPa C2H5OH, 0.1–50 kPa H2O) measured on ten low-defect (Sn-Beta-F) and high-defect (Sn-Beta-OH) zeolites were described by a rate equation that was derived from mechanisms identified previously by density functional theory calculations and simplified using microkinetic modeling to identify kinetically-relevant pathways and intermediates. Polar hydroxyl defect groups located in the microporous environments that confine Sn sites preferentially stabilize reactive (ethanol-ethanol) and inhibitory (ethanol-water) dimeric intermediates over monomeric ethanol intermediates. As a result, equilibrium constants (404 K) for ethanol-water and ethanol-ethanol dimer formation are 3–4× higher on Sn-Beta-OH than on Sn-Beta-F, consistent with insights from single-component (302 K) and two-component (303 K, 403 K) ethanol and water adsorption measurements. Intrinsic dehydration rate constants (404 K) were identical, within error, among Sn-Beta-OH and Sn-Beta-F zeolites; thus, measured differences in dehydration turnover rates solely reflect differences in prevalent surface coverages of inhibitory and reactive dimeric intermediates at active Sn sites. The confinement of Lewis acidic binding sites within secondary microporous environments of different defect density confers the ability to discriminate surface intermediates on the basis of polarity, providing a design strategy to accelerate turnover rates and suppress inhibition by water.
First principles, microkinetic, and experimental analysis of Lewis acid site speciation during ethanol dehydration on Sn-Beta zeolites J. Catal. (IF 6.759) Pub Date : 2018-07-20 Brandon C. Bukowski, Jason S. Bates, Rajamani Gounder, Jeffrey Greeley
Density functional theory calculations are combined with kinetic measurements of ethanol dehydration to diethyl ether to identify the relative catalytic contributions of structurally distinct speciations of Sn sites in zeolite Beta frameworks. The structural complexities of the Beta framework require nonstandard techniques for entropy and energy calculations, including consideration of anharmonic effects in vibrational modes, employment of quasi-harmonic densities of states methods to evaluate entropies, and use of hybrid density functionals to evaluate binding energies. Calculated energies and entropies are used to construct a microkinetic model that is iteratively refined to identify all kinetically and thermodynamically sensitive reaction steps and intermediates which are subsequently treated with the higher-level methods. The rate and equilibrium constants obtained from this tiered approach agree well with measured reaction orders in ethanol and water. Site balances provide evidence for the interconversion of Sn sites between “closed” configurations that are tetra-coordinated to the framework, open configurations formed by hydrolysis that are tri-coordinated to the framework and contain a hydroxyl ligand and proximal silanol group (“hydroxy-open”), and open tri-coordinate configurations formed by reaction with ethanol, yielding an ethoxy ligand and proximal silanol group (“ethoxy-open”). Closed, hydroxy-open, and ethoxy-open Sn sites adsorb ethanol via distinct modes and react via distinct pathways, with the consequence that prevalent dehydration pathways depend on the speciation of Sn sites under reaction conditions. The kinetic modeling indicates that, under the conditions studied (404 K, 0.5–35 kPa ethanol, 0.1–50 kPa water), bimolecular dehydration on the closed Sn site is the sole kinetically-relevant step, and ethanol, ethanol-ethanol dimers, and ethanol-water dimers are the most abundant surface intermediates. These results highlight the importance of considering the distribution of heteroatom coordination modes to zeolite frameworks under reaction conditions, as well as pathways for their interconversion in the presence of reacting molecules, to obtain more robust mechanistic and kinetic interpretations of catalytic pathways in Lewis acid zeolites.
Deactivation of Sn-Beta during Carbohydrate Conversion Appl. Catal. A Gen. (IF 4.521) Pub Date : 2018-07-21 William N.P. van der Graaff, Christiaan H.L. Tempelman, Frank C. Hendriks, Javier Ruiz-Martinez, Sara Bals, Bert M. Weckhuysen, Evgeny A. Pidko, Emiel J.M. Hensen
The deactivation of Sn-Beta zeolite catalyst during retro-aldolization and isomerization of glucose is investigated. Confocal fluorescence microscopy reveals that retro-aldolization of glucose in CH3OH at 160 °C is accompanied with the build-up of insoluble oligomeric deposits in the micropores, resulting in a rapid catalyst deactivation. These deposits accumulate predominantly in the outer regions of the zeolite crystals, which points to mass transport limitations. Glucose isomerization in water is not only accompanied by the formation of insoluble deposits in the micropores, but also by the structural degradation of the zeolite due to desilication and destannation. Enhanced and sustained catalytic performance can be achieved by using ethanol/water mixtures as the reaction solvent instead of water.
Selective photodegradation of paracetamol by molecularly imprinted ZnO nanonuts Appl. Catal. B Environ. (IF 11.698) Pub Date : 2018-07-20 Maria Cantarella, Alessandro Di Mauro, Antonino Gulino, Luca Spitaleri, Giuseppe Nicotra, Vittorio Priviter, Giuliana Impellizzeri
Photocatalysis-based technologies are currently striving to find a methodology able to selectively catch, and degrade specific organic contaminants. To solve this problem, we propose molecularly imprinted ZnO nanonuts as new nanomaterial. In this work, ZnO have been imprinted, through a chemical method, with one of the most diffused analgesic-antipyretic drugs: acetaminophen (commonly called “paracetamol”), today considered as an emergent environmental pollutant. The molecularly imprinted nanonuts have been characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) adsorption-desorption of N2, X-ray diffraction analyses (XRD), high-resolution transmission scanning electron microscopy (HR-S/TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Thanks to the accurate performed characterization, the interaction between ZnO and paracetamol has been elucidated. The photodegradation of paracetamol in aqueous solution has been demonstrated under UV light irradiation. The selectivity of the photodegradation process has been additionally investigated thanks to the comparison with the degradation of methyl orange (MO) and phenol, another two common water pollutants. Imprinted ZnO nanonuts have shown a great affinity and selectivity for the paracetamol, being able to degrade all the paracetamol present in the solution in 3 hrs. This work offers a new, economic, and easy way to prepare molecularly imprinted ZnO nanonuts with high specificity, relevant in the contexts of environmental protection.
Low-temperature NOx trapping on alkali or alkaline earth metal modified TiO2 photocatalyst Catal. Today (IF 4.667) Pub Date : 2018-07-20 Kazuki Tamai, Saburo Hosokawa, Hiroyuki Asakura, Kentaro Teramura, Tsunehiro Tanaka
Low-temperature NOx trapping was demonstrated on alkali (Na, K, Rb, and Cs) or alkaline earth metal (Mg, Ca, Sr, and Ba)-modified anatase TiO2 photocatalysts (M-TiO2). The modification enhanced the NOx-trapping efficiency of bare TiO2 as well as the NOx storage capacity (NSC). The NSC depended on the modified metal species. Cs-TiO2 and Ba-TiO2 showed a comparable capacity (179 and 187 μmol g−1, respectively) with a conventional NOx-trapping catalyst, Pt/Ba/Al2O3 (176 μmol g−1). XRD and XPS revealed the modification effect on the structures and the surface properties of M-TiO2. Alkali TiO2 promoted the sintering of TiO2 and significantly increased the electron density of the TiO2 surface, while alkaline earth TiO2 suppressed the sintering and slightly changed the surface properties. The adsorption strength of NOx was evaluated from the NOx-TPD of the as-synthesized catalyst. For alkaline earth TiO2, stronger NOx adsorption increased the NOx-trapping efficiency. In addition, in-situ DRIFT measurements clearly showed the difference between adsorbed NOx species in M-TiO2. Alkaline earth TiO2 traps NOx on Ti sites, whereas alkali TiO2 traps NOx mainly on alkali sites. NOx trapping on Ti sites for alkaline earth TiO2 was effective for photocatalytic NOx trapping with high efficiency at low temperature.
Enhanced Activity and Stability of a Carbon‐Coated Alumina‐Supported Pd Catalyst in the Dehydrogenation of a Liquid Organic Hydrogen Carrier, Perhydro 2‐(n‐methylbenzyl)Pyridine ChemCatChem (IF 4.674) Pub Date : 2018-06-22 Jinho Oh; Tae Wan Kim; Kwanyong Jeong; Ji Hoon Park; Young‐Woong Suh
Highly Efficient Aromatic C−H Oxidation with H2O2 in the Presence of Iron Complexes of the PDP Family ChemCatChem (IF 4.674) Pub Date : 2018-06-19 Nikolay V. Tkachenko; Roman V. Ottenbacher; Oleg Y. Lyakin; Alexandra M. Zima; Denis G. Samsonenko; Evgenii P. Talsi; Konstantin P. Bryliakov
Peptide‐Gold Nanoparticle Conjugates as Sequential Cascade Catalysts ChemCatChem (IF 4.674) Pub Date : 2018-07-20 Dorian Jamal Mikolajczak; Beate Koksch
Combining bio‐ and chemocatalysis in one pot is a challenging task due to the necessity to ensure compatible reaction conditions, as well as reagent tolerance, for the catalytic components. Here we present a peptide‐gold nanoparticle conjugate that combines esterase (biocatalysis) and hydrogenation (chemocatalysis) activities under the same set of aqueous reaction conditions. The self‐assembled peptide‐monolayer acts as an esterase mimic and shows positive cooperativity in substrate binding, an important feature used by nature to regulate catalytic activities of enzymes. The gold nanoparticle surface catalyzes the reduction of a nitro‐containing substrate to an amine product. This study opens up a new avenue in the design of peptide‐metal nanoparticle catalysts with enzyme‐like properties for efficient one‐pot reactions.
Understanding the CO Oxidation on Pt Nanoparticles Supported on MOFs by Operando XPS ChemCatChem (IF 4.674) Pub Date : 2018-07-20 Xiaolei Fan; Reza Vakili; Emma Gibson; Sarayute Chansai; Shaojun Xu; Peter Wells; Christopher Hardacre; Alex Walton; Nadeen Al-Janabi
Metal‐organic frameworks (MOFs) are playing a key role in developing the next generation of heterogeneous catalysts. In this work, near ambient pressure X‐ray photoelectron spectroscopy (NAP‐XPS) is applied to study in operando the CO oxidation on Pt@MOFs (UiO‐67) and Pt@ZrO2 catalysts, revealing the same Pt surface dynamics under the stoichiometric CO/O2 ambient at 3 mbar. Upon the ignition at ca. 200°C, the signature Pt binding energy (BE) shift towards the lower BE (from 71.8 to 71.2 eV) is observed for all catalysts, confirming metallic Pt nanoparticles (NPs) as the active phase. Additionally, the plug‐flow light‐off experiments show the superior activity of the Pt@MOFs catalyst in CO oxidation than the control Pt@ZrO2 catalyst with ca. 28% drop in the T50% light‐off temperature, as well as high stability, due to their sintering‐resistance feature. These results provide evidence that the uniqueness of MOFs as the catalyst supports lies in the structural confinement effect.
Squaramide‐IRMOF‐16 Analogue for Catalysis of Solvent‐Free, Epoxide Ring‐Opening Tandem and Multicomponent Reactions ChemCatChem (IF 4.674) Pub Date : 2018-07-20 Claudia Vignatti; Javier Luis-Barrera; Vincent Guillerm; Inhar Imaz; Ruben Mas-Ballesté; José Alemán; Daniel Maspoch
Tandem and multicomponent one‐pot reactions are highly attractive because they enable synthesis of target molecules in a single reaction vessel. However, they are difficult to control, as they can lead to the formation of many undesired side‐products. Herein we report the use of metal‐organic framework (MOF) pores decorated with organocatalytic squaramide moieties to confine ring‐opening epoxide reactions of diverse substrates. Controlled mono‐addition or tandem reactions inside the pores yield 1,2‐aminoalcohols or 1,2,2'‐aminodialcohols, respectively, in good yields. In addition, this squaramide‐functionalised MOF enables catalysis of higher‐complexity multicomponent reactions such as the catalytic ring‐opening of two different epoxides by a single amine to afford 1,2,2'‐aminodialcohols.
Ethylene oligomerization to select oligomers on Ni‐ETS‐10 ChemCatChem (IF 4.674) Pub Date : 2018-07-20 Jay Thakkar; Xinyang Yin; Xueyi Zhang
The oligomerization of short alkenes (ethylene and propylene) can be used for producing commodity chemicals. Various catalysts have been used for alkene oligomerization, among which ordered microporous catalysts are thermally and mechanically stable, and are already established for large‐scale industrial applications. In this work, we demonstrate ethylene oligomerization reaction on a microporous titanosilicate ETS‐10 (Engelhard Titanosiliate‐10) exchanged with Ni2+ (Ni‐ETS‐10). We demonstrate a template‐free and fluoride‐free ETS‐10 synthesis method that does not produce impurities commonly seen in hydrothermal ETS‐10 synthesis. Ni‐ETS‐10 showed high C2 conversion rate, high selectivity to C4 and high stability comparing to other microporous catalysts investigated in this work for ethylene oligomerization reaction.
Enhancement of the electrocatalytic activity of thienyl‐substituted iron porphyrin electropolymers by a Hangman effect ChemCatChem (IF 4.674) Pub Date : 2018-07-20 Bettina Neumann; Robert Götz; Pierre Wrzolek; Frieder Wolfram Scheller; Inez Weidinger; Matthias Schwalbe; Ulla Wollenberger
The thiophene‐modified iron porphyrin FeT3ThP and the respective iron Hangman porphyrin FeH3ThP, incorporating a carboxylic acid hanging group in the second coordination sphere of the iron center, were electropolymerized on glassy carbon electrodes using 3,4‐ethylenedioxythiophene (EDOT) as co‐monomer. Scanning electron microscopy images and Resonance Raman spectra demonstrated incorporation of the porphyrin monomers into a fibrous polymer network. Porphyrin/polyEDOT films catalyzed the reduction of molecular oxygen in a four‐electron reaction to water with onset potentials as high as + 0.14 V vs. Ag/AgCl in an aqueous solution of pH 7. Further, FeT3ThP/polyEDOT films showed electrocatalytic activity towards reduction of hydrogen peroxide at highly positive potentials, which was significantly enhanced by introduction of the carboxylic acid hanging group in FeH3ThP. The second coordination sphere residue promotes formation of a highly oxidizing reaction intermediate, presumably via advantageous proton supply, as observed for peroxidases and catalases making FeH3ThP/polyEDOT films efficient mimics of heme enzymes.
Effect of acidity of HZSM-5/MCM-41 hierarchical zeolite on its catalytic performance in supercritical catalytic cracking of n-dodecane: Experiments and mechanism Catal. Sci. Technol. (IF 5.365) Pub Date : 2018-07-20 Xiaochao Xian, Chao Ran, Peng Yang, Yirong Chu, Shuo Zhao, Lichun Dong
The effect of the acidity of HZSM-5/MCM-41 hierarchical zeolite on its catalytic performance in the supercritical catalytic cracking of n-dodecane was investigated by controlled ion exchange with NaCl solution under ultrasonic conditions. XRD and nitrogen adsorption-desorption results showed that the crystal and porous properties were not affected, while NH3-TPD, probe reaction of n-hexane cracking and temperature-programmed surface reaction(TPSR) of n-dodecane demonstrated that strong Brønsted acid sites were replaced by Na+ (weak Lewis acid sites) to different extents with varying concentrations of NaCl solution. Although the initial conversion of n-dodecane during the supercritical catalytic cracking was slightly reduced, the stability was greatly enhanced by ion exchange. An ultrastable catalyst with no obvious deactivation within 3 h of time on stream (TOS) was obtained by ion exchange with 0.8 M NaCl solution. A mechanism describing the role of the acid sites residing in both micropores and mesopores of the hierarchical catalyst was proposed based on the coke analysis.
Versatile etherification of alcohols with allyl alcohol by a titanium oxide-supported molybdenum oxide catalyst: gradual generation from titanium oxide and molybdenum oxide Catal. Sci. Technol. (IF 5.365) Pub Date : 2018-07-20 Yoshihiro Kon, Tadahiro Fujitani, Takuya Nakashima, Toru Murayama, Wataru Ueda
Etherification using allyl alcohol to produce allyl ether via dehydration is a fundamental technique for producing fine chemicals that can be applied to electronic devices. We demonstrate a sustainable method to synthesize allyl ethers from allyl alcohol with various alcohols up to a 91% yield, with water as the sole by-product. In this reaction, the active catalyst is gradually generated as the reaction proceeds through the simple mixing of TiO2 and MoO3. The dispersion of MoO3 at the spent catalyst has been observed by XRD, HAADF-STEM, and STEM-EDS mapping. This catalyst shows excellent catalytic activity by virtue of the highly dispersed nature of MoO3 supported on TiO2, which is reusable at least five times. According to a mechanistic study including the measurement of XPS of MoO3 on TiO2 and the control experiments using SiO2 and Al2O3 supports, the suitable reducibility of MoO3 to coordinate the allyl moiety on TiO2 seems to be a key factor for high-yielding syntheses of various allyl ethers even under heterogeneous reaction conditions. The reaction mechanism is considered to be as follow: σ-allyl species are formed from dehydration of the allyl alcohol, followed by a nucleophilic attack by another alcohol against the σ-allyl carbon to give allyl ethers. The developed catalytic system should be suitable for easily handled syntheses of allyl ethers due to the employment of commercially available MoO3 and TiO2 with halide- and organic solvent-free reaction conditions.
Mechanistic insights into hydrodeoxygenation of phenol on bimetallic phosphide catalysts Catal. Sci. Technol. (IF 5.365) Pub Date : 2018-07-16 Varsha Jain, Yolanda Bonita, Alicia Brown, Anna Taconi, Jason C. Hicks, Neeraj Rai
Hydrogenation of CO2 into hydrocarbons: enhanced catalytic activity over Fe-based Fischer–Tropsch catalysts Catal. Sci. Technol. (IF 5.365) Pub Date : 2018-07-13 Feng Jiang, Bing Liu, Shunshun Geng, Yuebing Xu, Xiaohao Liu
Controlling the redox properties of nickel in NiO/ZrO2 catalysts synthesized by sol–gel Catal. Sci. Technol. (IF 5.365) Pub Date : 2018-07-09 Jaime S. Valente, M. Valle-Orta, Héctor Armendáriz-Herrera, R. Quintana-Solórzano, Paz del Angel, J. Ramírez-Salgado, J. R. Montiel-López
One-pot combustion fabrication of grain-like mesoporous intra-heterostructure BixOyClz nanophotocatalyst with substantial solar-light-driven degradation of antibiotic ofloxacin: influence of various fuels Catal. Sci. Technol. (IF 5.365) Pub Date : 2018-06-21 Maryam Shabani, Mohammad Haghighi, Davood Kahforoushan
Synthesis of α,β‐dicarbonylhydrazones by aerobic manganese‐catalysed oxidation. Adv. Synth. Catal. (IF 5.123) Pub Date : 2018-07-20 Carlos J. Carrasco; Francisco Montilla; Eleuterio Álvarez; Agustin Galindo
A practical, simple, and efficient manganese‐catalysed oxidation of C(sp2)‐H bond in readily available β‐carbonylenehydrazine under aerobic conditions has been developed. This protocol exhibits a wide range of functional group tolerance in β‐carbonylenehydrazines to afford α,β‐dicarbonylhydrazones. Experimental and theoretical results suggest that the reaction very likely proceeds through a radical pathway via a hydrogen‐atom‐transfer process promoted by a MnIII species.
An Industrial Perspective on Counter Anions in Gold Catalysis: On Alternative Counter Anions Adv. Synth. Catal. (IF 5.123) Pub Date : 2018-07-20 Jasmin Schießl; Jürgen Schulmeister; Angelino Doppiu; Eileen Wörner; Matthias Rudolph; Ralf Karch; A. Stephen K. Hashmi
A comparison of versatile counter anions was investigated by means of a variety of well‐known test reactions representing the key reactivity patterns of homogeneous gold catalysis, the catalytic activity was monitored by GC and 1H NMR. As previously reported, the counter anion influence is usually more pronounced than the corresponding ligand effect. Due to this, the study is focused on the investigation of counter anions so far not included from investigation of homogeneous gold‐catalyzed reactions. The examinations using so far neglected counter anions (BArF4) , [B(C6F5)4] , [Al(OC(CF3)3)4]‐ and [B(C6F5)3(OAcF)]‐ showed surpassing or at least similar catalytic activities as the commonly used counter anions. The expanded use of counter anions can occupy an important role in future concerning catalyst optimization in gold catalysis.
Cobalt(III)–Catalyzed C–H Activation: Counter Anion Triggered Desilylative Direct ortho‐Vinylation of Secondary Benzamides Adv. Synth. Catal. (IF 5.123) Pub Date : 2018-07-20 Nachimuthu Muniraj; Kandikere Prabhu
A Co(III)‐catalyzed counter anion triggered desilylative direct ortho‐vinylation of secondary benzamides has been reported. The reaction furnished the alkenylated product, exclusively, and no formation of the possible cyclic products was observed. Mechanistic studies suggest that counter anion, [SbF6]‐, plays a crucial role in the desilylation. The utility of alkynyl silanes instead of terminal alkynes turned out to be a potential and practical approach to obtain the corresponding vinylated products. The developed methodology is compatible with a variety of functional group
Radical C‐H‐Amination of Heteroarenes using Dual Initiation by Visible Light and Iodine Adv. Synth. Catal. (IF 5.123) Pub Date : 2018-07-20 Nicola Lucchetti; Anastasia Tkacheva; Serena Fantasia; Kilian Muniz
A novel light‐induced C─H amination of heteroarenes can be accomplished with preformed iodine(III) reagents as the combined oxidant and nitrogen source. The reaction requires the use of a small amount of molecular iodine, which under photochemical activation generates in situ an iodine(I) reagent as the initiator of the radical amination reaction. A total of 32 examples exemplify the broad scope of the transformation.
Mild Access to N‐Formylation of Primary Amines using Ethers as C1 Synthons under Metal‐Free Conditions Adv. Synth. Catal. (IF 5.123) Pub Date : 2018-07-20 Mohana Reddy Mutra; Ganesh Kumar Dhandabani; Jeh-Jeng Wang
A new synthetic protocol has been developed for the synthesis of N‐formamide derivatives using ethers as a C1 synthon under metal‐free reaction conditions. The reaction is proposed to proceed through C‐H functionalization, C‐O cleavage, and C‐N bond formation. This protocol is applicable to a variety of primary amines resulting in N‐ formamides in moderate to good yields. 1,4‐dioxane was chosen as best C1 synthon after screening with various ethers. Mechanistic studies disclosed that the reaction proceeds through a radical pathway. While using α‐amino ketones a α‐alkylation product was formed rather than formylation. By replacing dioxane with Tetramethylethylenediamine (TMEDA) under standard conditions also gave the N‐formamide derivatives in moderate yields.
Hexapod PtRuCu Nanocrystalline Alloy for Highly Efficient and Stable Methanol Oxidation ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Shengfeng Xue, Wentao Deng, Fang Yang, Jinlong Yang, Ibrahim Saana Amiinu, Daping He, Haolin Tang, Shichun Mu
Suppression of Hydrogen Evolution Reaction in Electrochemical N2 Reduction Using Single-Atom Catalysts: A Computational Guideline ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Changhyeok Choi, Seoin Back, Na-Young Kim, Juhyung Lim, Yong-Hyun Kim, Yousung Jung
A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)3 Grafted onto γ-Alumina and Silica ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Kai C. Szeto, Zachary R. Jones, Nicolas Merle, César Rios, Alessandro Gallo, Frederic Le Quemener, Laurent Delevoye, Régis M. Gauvin, Susannah L. Scott, Mostafa Taoufik
Role of Surface Hydroxyl Species in Copper-Catalyzed Hydrogenation of Ketones ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Jenoff E. De Vrieze, Joris W. Thybaut, Mark Saeys
Stereo- and Regioselectivity in Catalyzed Transformation of a 1,2-Disubstituted Vicinal Diol and the Corresponding Diketone by Wild Type and Laboratory Evolved Alcohol Dehydrogenases ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Dirk Maurer, Thilak Reddy Enugala, Emil Hamnevik, Paul Bauer, Malin Lüking, Dušan Petrović, Heidi Hillier, Shina C. L. Kamerlin, Doreen Dobritzsch, Mikael Widersten
Metathetic Oxidation of 2-Butenes to Acetaldehyde by Molecular Oxygen Using the Single-Site Olefin Metathesis Catalyst (≡SiO)2Mo(═O)2 ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Frédéric Le Quéméner, Samir Barman, Nicolas Merle, Maha A. Aljuhani, Manoja K. Samantaray, Youssef Saih, Kai C. Szeto, Aimery De Mallmann, Yury Minenkov, Kuo-Wei Huang, Luigi Cavallo, Mostafa Taoufik, Jean-Marie Basset
Visible-Light-Mediated Methane Activation for Steam Methane Reforming under Mild Conditions: A Case Study of Rh/TiO2 Catalysts ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Hui Song, Xianguang Meng, Zhou-jun Wang, Zhuan Wang, Hailong Chen, Yuxiang Weng, Fumihiko Ichihara, Mitsutake Oshikiri, Tetsuya Kako, Jinhua Ye
Design of Interfacial Sites between Cu and Amorphous ZrO2 Dedicated to CO2-to-Methanol Hydrogenation ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Shohei Tada, Shingo Kayamori, Tetsuo Honma, Hiromu Kamei, Akane Nariyuki, Kenichi Kon, Takashi Toyao, Ken-Ichi Shimizu, Shigeo Satokawa
We examined the formation mechanism of active sites on Cu/ZrO2 specific towards CO2-to-methanol hydrogenation. The active sites on Cu/a-ZrO2 (a-: amorphous) were more suitable for CO2-to-methanol hydrogenation than those on Cu/t-ZrO2 (t-: tetragonal) and Cu/m-ZrO2 (m-: monoclinic). When a-ZrO2 was impregnated with a Cu(NO3)2･3H2O solution and then calcined under air, most of the Cu species entered a-ZrO2, leading to the formation of a Cu-Zr mixed oxide (CuaZr1-aOb). The H2 reduction of the thus-formed CuaZr1-aOb led to the formation of Cu nanoparticles on a-ZrO2, which can be dedicated to CO2-to-methanol hydrogenation. We concluded that the selective synthesis of CuaZr1-aOb, especially amorphous CuaZr1-aOb, is a key feature of the catalyst preparation. The preparation conditions of the amorphous CuaZr1-aOb specific towards CO2-to-methanol hydrogenation is as follows: (i) Cu(NO3)2･3H2O/a-ZrO2 is calcined at low temperature (350 °C in this study) and (ii) the Cu loading is low (6 and 8 wt% in this study). Via these preparation conditions, the characteristics of a-ZrO2 for the catalysts remained unchanged during the reaction at 230 °C. The latter preparation condition is related to the solubility limit of Cu species in a-ZrO2. Accordingly, we obtained the amorphous CuaZr1-aOb without forming crystalline CuO particles.
Engineering Ni3+ Cations in NiO Lattice at Atomic Level by Li+ Doping: the Roles of Ni3+ and Oxygen Species for CO Oxidation ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Xianglan Xu, Lin Li, Jin Huang, Hua Jin, Xiuzhong Fang, Wenming Liu, Ning Zhang, Hongming Wang, Xiang Wang
To investigate the Li+ doping effect on the structure and reactivity of NiO, a series of NiO catalysts doped by Li+ cations have been synthesized and probed by using CO oxidation as a model reaction. With the combination of experimental methods and DFT calculations, it has been revealed that the Li+ cations preferentially replace the lattice Ni2+ cations instead of directly refilling the Ni2+ vacancies in the cubic NiO lattice to form a solid solution structure below the lattice capacity. For samples possessing a pure solid solution phase, the Ni3+ cation amount increases with the increasing of lattice Li+ cation content, hence inducing the formation of larger quantities of surface mobile oxygen species. In addition, the surface reducibility and the CO adsorption and activation ability can be enhanced, accompanying the easier formation of surface oxygen vacancies and the extraction of surface active oxygen. Therefore, the intrinsic CO oxidation activity can be remarkably enhanced. In contrast, by the addition of excess Li+ cations above the lattice capacity, Li+ is present as an additional surface Li2CO3 phase, which degrades the activity of the catalysts evidently because of the loss of lattice Ni3+ cations and active oxygen sites. It is concluded in this paper that the best catalyst can be tailored at atomic level by engineering the maximum amount of Ni3+ cations in the NiO lattice matrix with a pure solid solution phase by Li+ addition.
Molecular Catalysis of Electrochemical Reactions. Cyclic Voltammetry of Systems Approaching Reversibility ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Jean-Michel Savéant
Efforts to design catalytic schemes approaching reversibility in which, the catalyst is active for both the oxidation and reduc-tion processes are attracting active attention boosted by recent successes. Kinetic analysis of such systems, by of electrochemi-cal techniques such as cyclic voltammetry (CV) would contrib-ute to establish reliable mechanisms. So far, the relationships required to achieve this task have been restrained to irreversible catalytic schemes. The purpose of the present communication is to fill this gap. As a preliminary contribution, the analysis is limited to simple on-electron-one step schemes so as to set out the main features of the competition between catalytic reaction and diffusion transport of catalyst and substrates. Emphasis is put on S-shaped CV responses, which offer the best opportunities to accessing the detailed kinetic information forming the basis of mechanisms determination
Understanding Surface-Mediated Electrochemical Reactions: CO2 Reduction and Beyond ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Marco Dunwell, Wesley W Luc, Yushan Yan, Feng Jiao, Bingjun Xu
Understanding reaction pathways and mechanisms for electrocatalytic transformation of small molecules, e.g., H2O, CO2 and N2, to value-added chemicals is critical to enabling the rational design of high-performing catalytic systems. Tafel analysis is widely used to gain mechanistic insights, and in some cases, has been used to determine the reaction mechanism. In this Perspective, we discuss the mechanistic insights that can be gained from Tafel analysis and its limitations using the simplest 2-electron CO2 reduction reaction to CO on Au and Ag surfaces as an example. By comparing and analyzing existing as well as additional kinetic data, we show that the Tafel slopes obtained on Au and Ag surfaces in the kinetically controlled region (low overpotential) are consistently ~59 mV dec-1, regardless of whether catalysts are polycrystalline or nanostructured in nature, suggesting that the initial electron transfer (CO2 + e- CO2-) is unlikely to be the rate-limiting step. In addition, we demonstrate how initial mechanistic assumptions can dictate experimental design, the result of which could in turn bias mechanistic interpretations. Therefore, as informative as Tafel analysis is, independent experimental and computational techniques are necessary to support a proposed mechanism of multi-electron electrocatalytic reactions, such as CO2 reduction.
Titania-Silica Catalysts For Lactide Production From Renewable Alkyl Lactates: Structure-Activity Relations ACS Catal. (IF 11.384) Pub Date : 2018-07-20 Rik De Clercq, Michiel Dusselier, Claude Poleunis, Damien P. Debecker, Lars Giebeler, Steffen Oswald, Ekaterina Makshina, Bert F. Sels
Different Ti-Si catalysts, viz. TiO2 supported on amorphous SiO2 or Si-MCM-41, TiO2-SiO2 xerogels and Ti-zeolites (TS-1 and Ti-beta) were compared in terms of activity and selectivity for the direct conversion of methyl lactate to lactide in the gas phase. Except for Ti-beta, all catalysts exhibit a high lactide selectivity of 88-92% at conversions below 50 %. From DR UV-VIS spectroscopy, it is evidenced that the catalytic activity of tetrahedral TiO4 sites is higher than of polymerized TiO5 or octahedral TiO6 counterparts, irrespective of the catalyst structure, an analysis supported by ToF-SIMS measurements. A kinetic analysis shows that the catalytic activity is proportional to the number of vacant sites on the catalyst surface. Thus, the activity increase observed for tetrahedral TiO4 sites may be attributed to an increased number of vacant sites (e.g. two for TiO4, zero for TiO6). Lactide productivity thus highly benefits from an increased dispersion of Ti-sites on the catalyst surface, and could be increased by a factor of 2.5 (up to 10 gLD gcat-1 h-1) when TiO2 is dispersed on a Si-MCM-41 support, with higher surface areas than amorphous SiO2 gels.
In situ immobilized palladium nanoparticles on surface of poly-methyldopa coated-magnetic nanoparticles (Fe3O4@PMDA/Pd): A magnetically recyclable nanocatalyst for cyanation of aryl halides with K4[Fe(CN)6] J. Catal. (IF 6.759) Pub Date : 2018-07-19 Hojat Veisi, Saba Hemmati, Parisa Safarimehr
Poly-methyldopa (PMDP)-coated Fe3O4 nanoparticles (Fe3O4@PMDP) have been synthesized through a simple and green procedure. In the present study, for the first time, Pd nanoparticles were successfully deposited using Fe3O4@PMDP as a core-shell magnetic coordinator and stabilizer agent. In this protocol, Pd ions were adsorbed on surfaces of Fe3O4@PMDP through immersion of the PMDP-coated Fe3O4 nanoparticles into a palladium plating bath. Next, they were reduced in situ to palladium nanoparticles using PMDP’s N-containing groups and reducing ability. The structure, morphology and physicochemical properties of the synthesized nanoparticles were characterized by different analytical techniques such as energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscope (FESEM), Fourier-transform infrared spectroscopy (FT-IR) spectroscopy, high resolution transmission electron microscopy (HR-TEM), inductively coupled plasma (ICP), thermo gravimetric analysis (TGA), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS). Core-shell Fe3O4@PMDP/Pd(0) nanoparticles showed excellent catalytic performance as a reusable nanocatalyst for cyanation of aryl iodides and bromides with K4[Fe(CN)6] as the cyanating agent. The nitriles were obtained in good to excellent yield and the catalyst can be recycled and reapplied up to seven times with only very slight decrease in its catalytic performance.
Cu-doped ZnO as efficient photocatalyst for the oxidation of arsenite to arsenate under visible light Appl. Catal. B Environ. (IF 11.698) Pub Date : 2018-07-19 V. Vaiano, G. Iervolino, L. Rizzo
In this work, photocatalytic oxidation of As(III) to As(V) by ZnO photocatalyts doped with Cu was investigated under visible light. Photocatalysts were successfully prepared by precipitation method. The obtained samples were characterized by N2 adsorption at −196 C, X-Ray fluorescence analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV–vis reflectance analysis. In particular, according to XRD analysis, all samples showed an hexagonal wurtzite structure with average crystallite sizes approximately in the range 32-33 nm. The doping with Cu allowed to obtain a decrease of band gap energy from 3.2 eV, typical of pure ZnO, to 2.92 eV. Photocatalytic oxidation tests under visible light showed that undoped ZnO is not able to oxidize the As(III) present in solution, while the complete conversion of As(III) to As(V) was achieved in the presence of Cu doped ZnO photocatalyst. The best photocatalytic activity was observed with ZnO doped with 1.08 mol% of Cu (1.08Cu_ZnO), within 120 min of exposure to visible light irradiation. The same result was observed under solar simulated radiation. Photocatalytic tests were carried out also in real drinking water and complete oxidation of As(III) to As(V) by 1.08Cu_ZnO photocatalyst was achieved in 120 minutes under both visible light (emitted by LEDs) and solar simulated radiation.
Advances in catalytic/photocatalytic bacterial inactivation by nano Ag and Cu coated surfaces and medical devices Appl. Catal. B Environ. (IF 11.698) Pub Date : 2018-07-19 Sami Rtimi, Dionysios D. Dionysiou, Suresh C. Pillai, John Kiwi
The design, synthesis, fundamentals and evaluation of 2D/3D antimicrobial surfaces are addressed in detail in the current review. Recent advances in the antimicrobial mechanism, kinetics and properties of Ag, Cu and Ag-Cu surfaces in the dark and under light irradiation are described and discussed. The structure-reactivity relations in the catalyst/photocatalyst layers were described by way of the surface characterization and the observed antibacterial kinetics. Escherichia coli (E. coli) and Methicillin resistant Staphylococcus aureus MRSA bacteria are selected as model pathogens to evaluate the antimicrobial inactivation kinetics. The separate antimicrobial properties of ions and the antimicrobial surface-contact effects are presented in a detailed way. The interfacial charge transfer (IFCT) mechanism and the identification of the most relevant reactive oxygen species (ROS) leading to bacterial disinfection are considered. The recently developed monitoring of the changes of the film surface potential (Eigenvalues) during bacterial inactivation and the redox reactions associated with catalyst/photocatalyst surfaces are also presented. The potential for practical applications of these innovative 2D films and 3D sputtered medical devices in health-care facilities are accounted for in the present review.
Direct synthesis of 2,5-diformylfuran from carbohydrates via carbonizing polyoxometalate based mesoporous poly(ionic liquid) Catal. Today (IF 4.667) Pub Date : 2018-07-19 Qian Wang, Wei Hou, Tongsuo Meng, Qian Hou, Yu Zhou, Jun Wang
A promising atom-effective heterogeneous catalyst derived from the partial carbonization of polyoxometalate based mesoporous poly(ionic liquid) was constructed for the direct (one-pot and one-step) conversion of carbohydrates into 2,5-diformylfuran (DFF). The carbon precursor was synthesized through the free radical copolymerization of carboxylic acid functional ionic liquid and divinyl benzene, followed by the ion-exchange with heteropolyacid H5PMo10V2O40 to introduce heteropolyanions. Partial carbonization dramatically enhanced the acid and oxidation properties, rendering the greatly strengthened activity in both the degradation of fructose into 5-hydroxymethylfurfural (HMF) and oxidation of HMF into DFF. As a result, the catalyst exhibited remarkable performance in the direct synthesis of DFF from fructose in a one-pot and one-step reaction, offering a high yield of 87.3% and a maximum turnover number (TON) of 77.7. The catalyst was facilely recovered and reused without apparent deactivation. The one-pot and one-step conversion of glucose into DFF reached the highest yield of 51.2% so far. Other carbohydrates such as inulin and sucrose were also effectively transformed into DFF, displaying good substrate compatibility.
Catalytic transfer hydrogenation of bio-based furfural by palladium supported on nitrogen-doped porous carbon Catal. Today (IF 4.667) Pub Date : 2018-07-19 Pillaiyar Puthiaraj, Kyoungsoo Kim, Wha-Seung Ahn
Highly porous carbon was prepared via a zeolite hard templating route. Subsequent melamine treatment produced nitrogen-functionalized carbon (NPC), which was used as a support to anchor Pd nanoparticles (Pd/NPC) of sizes 2-4 nm using the chemical reduction method. Various analytical techniques were used to characterize the textural properties, structure, and chemical nature of the catalyst. Pd/NPC was then employed as a catalyst for the transfer hydrogenation of biomass-derived furfural (FF) to furfuryl alcohol (FFA) with alcohol as a hydrogen donor, and the effect of temperature, hydrogen donor species, reaction time, and catalysts loading were investigated. The Pd/NPC catalyst was reusable up to five times without any apparent loss of its activity and selectivity. A possible mechanistic pathway for the catalytic transfer hydrogenation of FF over Pd/NPC catalyst was proposed.
A review on dry reforming of methane in aspect of catalytic properties Catal. Today (IF 4.667) Pub Date : 2018-07-19 Won-Jun Jang, Jae-Oh Shim, Hak-Min Kim, Seong-Yeun Yoo, Hyun-Seog Roh
Because the whole world is under threat from climate change, 195 countries decided to reduce greenhouse gas (GHG) emissions by adopting the “Paris Agreement”. The mitigation and utilization of GHG have become the most significant challenges in the area of green energy research. One feasible solution is the reforming of methane with carbon dioxide (called dry reforming of methane, DRM) that converts the two main GHGs (CO2 and CH4) into synthesis gas (H2 and CO), which is a resource for the manufacture of useful value-added products. The main issue that needs to be addressed for DRM is the deactivation of catalysts by sintering and carbon formation. Design of a viable catalyst that exhibits high catalytic activity and stability, as well as resistance against deactivation, could be accomplished by making appropriate choices of active metal, support, promoter, structure and methods for preparation and activation. Numerous studies and reviews have dealt with various aspects of DRM. This review focuses on the physicochemical properties of the pertinent catalysts and their role in the catalytic performance needed for DRM. Specifically, the interaction between components, dispersion, particle size, basicity, oxygen storage capacity, reducibility, porosity and surface area are discussed. This study provides the understanding of catalytic properties and their correlation with catalytic performance needed for the rational design of catalysts and suitable for DRM.
The promotional role of Nd on Mn/TiO2 catalyst for the low-temperature NH3‑SCR of NOx Catal. Today (IF 4.667) Pub Date : 2018-07-19 Jun Huang, He Huang, Hongtao Jiang, Licheng Liu
A series of rare-earth metal doped 30% Mn-3% RE/TiO2 (RE = Ce, Sm, Nd, Er, Y) catalysts were prepared by adopting two step incipient wetness impregnation method and investigated for the low-temperature SCR of NOx with NH3. It was found that 3% of rare earth elements (Nd, Er, Y) was added to 30% Mn/TiO2 catalyst even could increase the catalytic performance at the low temperature, in addition to usual used Ce and Sm. And the promoting effect of Nd was among the most significant. Then the 30%Mn-3%Nd/TiO2 catalyst was synthesized by another two methods, Coprecipitation and Sol-gel, for a comparative study. Various techniques were applied to characterize the catalysts. The catalysts prepared by Coprecipitation and Sol-gel method exhibited higher surface area and smaller average particle size in comparison with catalyst prepared by impregnation with TiO2 support. The addition of Nd made surface area and dispersion of MnOx species increase. It also led both the content of amorphous MnO2 and the content of crystalline Mn2O3 to decrease, but the proportion of MnOx species with low oxidation state increased. H2-TPR results showed that the low temperature reduction peak of MnOx was shifted to much lower temperatures with the doping of Nd, which improved the redox property of the catalysts. The all characteristics shown above could well explain the promotional role of Nd doping in the 30%Mn-3%Nd/TiO2 catalyst, that improved the low temperature SCR catalytic activity.
Enhanced visible-light-induced photocatalytic degradation and disinfection activities of oxidized porous g-C3N4 by loading Ag nanoparticles Catal. Today (IF 4.667) Pub Date : 2018-07-19 Jing Xu, Qiuzhu Gao, Xiaojuan Bai, Zhouping Wang, Yongfa Zhu
Herein, Ag nanoparticles (AgNPs) were loaded on oxidized porous g-C3N4 (PCNO) via photo-assisted reduction method. Compared with PCNO, Ag/PCNO plasmonic photocatalysts possessed remarkably enhanced photocatalytic performances in both pollutant degradation and disinfection under visible light irradiation. The optimum photocatalytic activity of Ag/PCNO at a loading amount of 2.0 wt% (Ag-2/PCNO) on amaranth degradation was almost 2.4 times as fast as that of PCNO. Additionally, Ag-2/PCNO could inactivate about 99.4% of Staphylococcus aureus (S. aureus) cells after 3 h of irradiation, whereas only about 29.6% of S. aureus cells were inactivated by PCNO. The enhancement of photocatalytic activities for Ag/PCNO composites could be ascribed to the combination of the SPR effect of AgNPs and the synergistic effect from PCNO molecules, which resulted in enhanced absorption in visible-light region, improved charge transfer, and reduced charge recombination. Moreover, h+ and O2− were the dominate reactive species for Ag/PCNO composites to remove azo pigments and pathogenic bacteria efficiently during the photocatalytic process.
Efficient oxidative dehydrogenation of ethanol by VOx@MIL-101: on par with VOx/ZrO2 and much better than MIL-47(V) Catal. Today (IF 4.667) Pub Date : 2018-07-19 Bulánek Roman, Čičmanec Pavel, Kotera Jiří, Boldog Ishtvan
The possibility to apply metal organic framework (MOF) based catalysts for oxidation reaction in gas phase was explored. Catalytic activity of the vanadium oxide catalyst incorporated in MIL-101(Cr) as support was investigated in gas phase ethanol oxidative dehydrogenation (EtOH-ODH) and compared to that of MIL-47(V) metal organic framework material containing vanadium as central metal in the framework structure and to a classical VOx/ZrO2 supported vanadium oxide catalyst. It was found that vanadium species, incorporated in MIL-101(Cr) support by a variant of vapor deposition method, are stabilized in the form of well dispersed VOx species (no vanadium pentoxide clusters was detected in the catalyst). The obtained VOx@MIL-101(Cr) catalyst exhibited high selectivity towards acetaldehyde (up to 99%) at reaction temperatures not exceeding 200 °C. The catalytic activity of VOx@MIL-101(Cr) catalyst reached an activity level comparable to that of the classical VOx/ZrO2 catalyst, but the specific productivity of acetaldehyde (3 kgAA kgcat-1 h-1) was higher by 75% compared with productivity on VOx/ZrO2 due to much higher content of vanadium species, which could be hosted by the MOF. On the other hand, MIL-47(V) catalyst exhibited negligible activity seemingly due to coordinatively saturated character of the vanadium centers and/or too high stability of the VIV oxidation state. This proof-of-concept study proved that application of MOF materials as host matrices for heterogeneous catalysts aiming oxidation reaction in gas phase could be efficient as demonstrated on the example of oxidative dehydrogenation of ethanol.
Excellent visible-light driven photocatalyst of (Al, Ni) co-doped ZnO structures for organic dye degradation Catal. Today (IF 4.667) Pub Date : 2018-07-19 I. Neelakanta Reddy, Ch. Venkata Reddy, Jaesool Shim, Bhargav Akkinepally, Migyung Cho, Kisoo Yoo, Dongseob Kim
(Al, Ni) co-doped ZnO nanostructures were synthesized by a simple ball-milling method. The samples prepared were extensively characterized using standard techniques. X-ray diffraction analysis confirmed the coexistence of Al and Ni in the ZnO sites. The pollutant photodegradation performances of the materials were assessed by studying the removal of methyl orange and Congo red under visible-light illumination. Of the photocatalysts prepared, 2%Al-2%Ni-ZnO was found to be the most active for pollutant degradation, effecting 100% removal of MO within 30 min under visible-light illumination. This excellent catalytic activity was attributed to the strong absorption of visible light and effective separation of photoinduced charge carriers. In addition, radical-scavenging experiments were conducted to identify the key reactive species formed in the reaction, allowing a mechanistic rationale for the superior photocatalytic activity of 2%Al-2%Ni-ZnO to be proposed.
Improvement of NH3-SCR performance and SO2 resistance over Sn modified CeMoOx electrospun fibers at low temperature Catal. Today (IF 4.667) Pub Date : 2018-07-19 Zhifei Hao, Yongli Jiao, Qiang Shi, He Zhang, Sihui Zhan
A series of novel Sn modified CeMoOx electrospun fibers were fabricated using a combination method of sol-gel process and electrospinning technique for the selective catalytic reduction (SCR) of NO with NH3. The performances of fresh and sulfated Sn modified CeMoOx catalysts in the presence of different amount of SO2 at low temperature were investigated. Characterization of these catalysts aimed at elucidating the effect of additive. The catalyst had a Sn/(Sn + Ce + Mo) = 0.2 M ratio showed the widest SCR activity improvement with near 100% NOx conversion at 225–450 °C with a gas hourly space velocity of 100 000 h−1. X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the chemisorbed oxygen species that may facilitate NO oxidation to NO2. H2-TPR and NH3-TPD characterization showed that the catalysts have better redox ability and higher Brønsted acid sites, which is also enhanced by Sn modification. Combined with the adsorption and transient reaction studied from in situ DRIFTs spectra suggested a “fast SCR” reaction route, i.e., the more active NH4+ ions react with gaseous NO2 molecules, which primarily occurred on the surface of either the fresh or sulfated Sn/0.2-CeMoOx. Furthermore, as compared to CeMoOx, the sulfated Sn/0.2-CeMoOx sample obtained even smaller grain size, better redox ability, higher Brønsted acid sites and more chemisorbed oxygen species, which were contributed to the excellent SO2 resistance.
Evolution of active sites during selective oxidation of methane to methanol over Cu-CHA and Cu-MOR zeolites as monitored by operando XAS Catal. Today (IF 4.667) Pub Date : 2018-07-20 Elisa Borfecchia, Dimitrios K. Pappas, Michael Dyballa, Kirill A. Lomachenko, Chiara Negri, Matteo Signorile, Gloria Berlier
The local structural and electronic properties of Cu sites during the direct conversion of methane to methanol with molecular oxygen was followed by X-ray absorption spectroscopy (XAS) on a set of Cu-zeolites with different topology (large pore MOR and small pore CHA frameworks) and similar chemical composition (Si/Al ∼ 11 and 12, respectively). Two low loading (LL) and high loading (HL) samples were prepared by ion exchange, and their methanol productivity measured in laboratory fixed bed reactor tests, resulting in selectivity higher than 85%. Both Cu-MOR samples outperformed Cu-CHA ones, resulting in 0.28 and 0.26 molCH3OH/molCu for the LL (Cu/Al = 0.13) and HL (Cu/Al = 0.36) samples, vs 0.10 and 0.17 molCH3OH/molCu for LL and HL Cu-CHA, respectively (Cu/Al = 0.16 and 0.49). The evolution of Cu oxidation state and local coordination environment was followed in all the reaction steps (O2 activation, flush with He, CH4 dosage and subsequent CH3OH desorption by applying a wet stream) both during temperature changes (ramp in O2 up to 500 °C, cooling to 200 °C for subsequent steps, etc.) and in steady-state conditions. Strong similarities were observed in the local structure of Cu sites in all samples, which showed similar redox dynamics during O2 activation and subsequent cooling to 200 °C. Even though only qualitative considerations can be made on the overall spectral evolution, XANES indicates that not all the Cu(I) formed during CH4 loading belongs to active sites.
Cu2O/TiO2 nanoparticles as visible light photocatalysts concerning C(sp2)–P bond formation Catal. Sci. Technol. (IF 5.365) Pub Date : 2018-06-28 Mona Hosseini-Sarvari, Fattaneh Jafari, Afshan Mohajeri, Nasim Hassani
Control and Switching of Charge-Selective Catalysis on Nanoparticles by Counterions ACS Catal. (IF 11.384) Pub Date : 2018-07-19 Qiang Zhuang, Zhijie Yang, Yaroslav I. Sobolev, Wiktor Beker, Jie Kong, Bartosz A. Grzybowski
Palladium-Catalyzed Aerobic Homocoupling of Alkynes: Full Mechanistic Characterization of a More Complex Oxidase-Type Behavior ACS Catal. (IF 11.384) Pub Date : 2018-07-19 Alberto Toledo, Ignacio Funes-Ardoiz, Feliu Maseras, Ana C. Albéniz
Existence of an Electrochemically Inert CO Population on Cu Electrodes in Alkaline pH ACS Catal. (IF 11.384) Pub Date : 2018-07-19 Charuni M. Gunathunge, Vincent J. Ovalle, Yawei Li, Michael J. Janik, Matthias M. Waegele
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