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In this study, a novel magnetically recoverable Fe3O4@SiO2–BenzIm-Fc[Cl]/BiOCl nano-composite was synthesized using a simple chemical co-precipitation method. This is the first time that a magnetic nano-catalyst bearing ionic liquid, ferrocene and BiOCl is synthesized. The Fe3O4@SiO2–BenzIm-Fc[Cl]/BiOCl nano-composite was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FE-SEM) techniques. The catalytic activities of the novel magnetic nano-composite were evaluated in one-pot three-component synthesis of a wide variety of 2-amino-3-cyano-4H-chromene derivatives under ultrasound irradiation. A simple, facile and highly efficient ultrasound-assisted method was developed to synthesize 4H-chromene derivatives via one-pot, three-component reaction of aldehyde, malononitrile and active phenolic compounds (2-naphthol, 1-naphthol, 3-(dimethylamino)phenol, resorcinol and orcinol) at room temperature. The reaction of aldehyde, malononitrile and orcinol is newly introduced in this paper. The ultrasound-assisted synthesis protocol that was studied in this article exhibits some notable advantages such as short reaction times, operational simplicity, green reaction conditions, high yields and easy work-up and purification steps. In addition, the novel magnetic nano-composite could be easily recovered by an external magnetic field and reused for six-reaction cycles without significant loss of its catalytic activity. [ABSTRACT FROM AUTHOR]

A reduced graphene oxide–V2O5 nanocomposite was synthesized by a low temperature surfactant free hydrothermal method and its MFC performance was assessed. The structural properties of the synthesized nanocomposite were studied by X-ray diffraction. Field emission scanning electron microscopy of the nanocomposite revealed a wrinkled paper-like structure of rGO and a nanobelt-like structure of V2O5. This study estimated the viability of the graphene-based nanocomposite rGO–V2O5 as a novel cathode catalyst in single chamber air-cathode MFCs. A series of MFCs with different catalyst loadings were produced. The electrochemical behavior of the MFCs was calculated by cyclic voltammetry. The MFCs with the rGO–V2O5 nanocomposite cathode exhibited superior maximum power densities (83%) to those with the pure V2O5 cathodes. The rGO–V2O5 with a double-loaded nanocomposite catalyst achieved an enhanced power density of 1668 ± 11 mW m−2 and an OCP of 698 ± 4 mV, which was 83% of that estimated for the Pt/C 2004 ± 15 mW m−2 nanocomposite cathode. The significant increase in power density suggests that the reduced graphene oxide–V2O5 nanocomposite is a promising material for MFC applications. The CV result showed good agreement with the MFC result. The prepared rGO–V2O5 nanocomposite cathode, particularly with a double loading catalyst, is promising as a sustainable low-cost green material for stable power generation and long-term operation of MFCs. [ABSTRACT FROM AUTHOR]

In this paper, the Keplerate nanoball iso-polyoxomolybdate {Mo132} supported on activated carbon (AC) has been synthesized and evaluated as a new, green and cost-effective catalyst for the oxidative desulfurization of a model fuel containing dibenzothiophene (DBT). The {Mo132}/AC catalysts, which were prepared with various {Mo132} contents, were characterized using FT-IR, XRD, SEM, EDX, ICP-OES, H2-TPR and nitrogen adsorption/desorption isotherms. Experimental evaluations showed that the catalyst was highly efficient in the removal of DBT using hydrogen peroxide (H2O2) as the oxidant, which could result in a sulfur removal of up to 99.5% (or even more than that) under optimum reaction conditions. The factors affecting the process including catalyst dosage, temperature, O/S molar ratio, reaction time and initial sulfur content were evaluated, and the optimum operating conditions were determined. In addition, the new catalyst was recoverable and the recovered {Mo132}/AC demonstrated a relatively similar catalytic activity to the fresh one. According to the results of GC-MS analysis, a sulfone species was found to be the only product of DBT oxidation by H2O2 over {Mo132}/AC. Moreover, a mechanism for the oxidative desulfurization of DBT by the new catalyst was proposed. The present study suggested that the {Mo132}/AC composite could be used as an efficient catalyst for the deep oxidative desulfurization and removal of refractory sulfur compounds in fossil fuels. [ABSTRACT FROM AUTHOR]

A new material, MgAl-LDHs/Al2O3 fiber (abbreviated as MAF), was prepared using the classical hydrothermal method with a modification in this paper. The influence of different pH values on the structure and catalytic performance of catalysts for propane dehydrogenation was studied. The as-prepared materials were characterized by XRD, SEM, TEM, SAED, N2-physisorption, NH3-TPD, and TPO. Experimental results show that the pH value of the solution directly controlled the vertical growth of LDH sheets on Al2O3 fibers. After the suitable growth of LDH sheets, the dispersed state of active metal Pt was improved and the sizes were stabilized successfully at high temperature. Due to the effect of these LDH sheets, the BET surface and the regular pore system of the PtSn/15MAF catalysts were enhanced compared with the PtSn/CPMA catalysts. Finally, the propane dehydrogenation performance indicates that, when the pH was equal to 8.5, the catalysts (PtSn/15MAF) showed the highest conversion, selectivity and stability. [ABSTRACT FROM AUTHOR]

In this paper, tris(hydroxymethyl)methylene ammonium acetate supported on GO as a new multifunctional heterogeneous catalyst was synthesized. After its characterization by different techniques such as FT-IR, TEM, FESEM, EDS, XPS, solid-state MAS NMR and elemental analysis, it was used as an efficient catalyst for the synthesis of hexahydroquinolines (HHQs) via a one-pot multi-component reaction. Different HHQs were synthesized in the presence of this heterogeneous metal-free catalyst in good to high yields at room temperature under solvent-free conditions. The catalyst was easily separated and reused at least five times without significant loss of activity. The acidic nature of GO improved the catalytic activity of the supported ILs and also provided heterogeneity to the ILs. This is the first report for the synthesis of HHQs in the presence of a multifunctional heterogeneous catalyst. [ABSTRACT FROM AUTHOR]

In this paper, magnetic Fe3O4@SiO2@mSiO2 microspheres with core–shell structure were chosen as a catalyst support, then hyperbranched polyglycerol (HPG) was successfully grafted onto the exterior surface and mesopore wall of this material under the catalysis of isopropanol aluminum. Subsequently, the terminal hydroxyl groups of HPG were successfully transformed into carboxyl groups after modification with succinic anhydride. Ultimately, palladium nanoparticles (Pd NPs) were successfully anchored onto the surface of the aforementioned magnetic Fe3O4@SiO2@mSiO2 microspheres with high density carboxylic HPG, nanocrystallization by the complexation between Pd2+ ions and carboxyl groups and the subsequent reduction, a novel Fe3O4@SiO2@mSiO2-HPG-COOH-Pd(0) supported catalyst was successfully obtained. This novel supported Pd NP catalyst is very conducive to the transference and exchange of each component in the reaction system for the orderly mesoporous opening structure. Furthermore, the introduction of a magnetism nucleus can provide convenient magnetic separation. More importantly, the numerous terminal carboxyl groups on the surface of the magnetic Fe3O4@SiO2@mSiO2 microspheres can provide plenty of sufficient binding sites for Pd NPs, and the unique hyperbranched structure is very conducive to capture uniformly dispersed nanosized palladium and can effectively enhance the catalytic activity and stability. Research indicates that this novel supported Pd NP catalyst not only possesses extremely high Pd NPs loading capacity but also shows remarkable catalytic activity to the Suzuki cross-coupling reaction between aryl halides and phenylboronic acid. Simultaneously, the catalytic activity of this supported catalyst did not show evident loss after being used at least eight times. [ABSTRACT FROM AUTHOR]

The structure of doped ceria plays an important role in its chemical reactivity and catalytic performance. However, for the majority of the dopants studied, whether a monophasic solid solution is formed or not is typically determined only by standard X-ray diffraction (XRD). In-depth structural characterization is lacking. In this paper we have prepared Zn-doped ceria nanocrystals exhibiting twice the oxygen storage capacity (OSC) of pure ceria. X-ray photoelectron spectroscopy (XPS) shows that the material is chemically inhomogeneous with zinc enrichment in the surface layer. X-ray fluorescence (XRF) reveals significant compositional inhomogeneity of the material after annealing in air at 1300 °C for 24 h. The standard structural characterization of this material using room temperature XRD and transmission electron microscopy (TEM) fails to reveal its correct phase composition. Based on clear evidence from in situ high temperature XRD we show that, after calcination at 500 °C, the material is not monophasic: X-ray amorphous ZnO is present within the material. The amorphous ZnO crystallizes at 800 °C and undergoes second-stage incorporation at even higher temperatures. This second-stage incorporation is not complete after annealing and trace amounts of ZnO remain according to synchrotron-based XRD. Our work provides valuable insight into the incorporation mechanism of zinc into the ceria lattice, and in particular, raises some doubts on the phase compositions reported in many previous studies on doped ceria. [ABSTRACT FROM AUTHOR]

The present review paper deals with the development of catalytic systems in water in the presence of micelles obtained by addition of surfactants, focusing on the effects of these simple, economic, and green reaction media on important aspects like recyclability, activity, product and substrate selectivity. Contributions from 2005 to 2014 are surveyed with particular emphasis on emerging findings and directions in the field of catalysis. Surfactants enable formation of nanosized apolar aggregates in bulk water where the catalysts and reagents can be dissolved thanks to weak intermolecular interactions like the hydrophobic effect and ion pairing operating in a more concentrated system compared to the bulk solvent. While in the past the use of surfactants was a straightforward approach to enable solubilization of reaction mixtures in water, nowadays specific interactions between substrates, catalysts and micelles are investigated by means of NMR and other techniques to better understand the molecular basis of this kind of supramolecular catalysis. Specifically designed surfactants to engineer micelles in order to compete efficiently with traditional catalysis in organic solvents are nowadays available. [ABSTRACT FROM AUTHOR]

Biomass conversion is potentially important for producing renewable fuels and chemicals in the future, and the nanoporous materials as acidic, basic, or metallic catalysts play important roles in the biomass conversion. This paper briefly summarizes recent developments on the nanoporous material-based catalysts used for biomass conversion, including mesoporous/macroporous resins, mesoporous metal oxides, microporous/mesoporous carbons, mesoporous silicas, hierarchically mesoporous polydivinylbenzene, and microporous zeolites. Due to their superior thermal and hydrothermal stability, controllable acidity, and relatively easy introduction of mesoporosity into the crystals, compared with other nanoporous catalysts, zeolites have good opportunities for application in biomass conversion. [ABSTRACT FROM AUTHOR]

The active species distribution of zeolites significantly influences the catalytic performance. In this paper, titanium silicalite-1 (TS-1) was synthesized from silica sol, TiCl3 and NH3 with tetrapropyl ammonium bromide (TPAB) as the template agent. Modification with ethanolamine altered the distribution of Ti species in TS-1 particles. Some large voids as 50 × 70 nm and 70 × 110 nm existed in the inner part of modified TS-1 crystals and were responsible for improved diffusion properties and accessibility to active sites. The modified TS-1 was examined in continuous cyclohexanone ammoximation. A high conversion of cyclohexanone (98%) and oxime selectivity (100%) was still maintained after the test reaction had been carried out up to 410 h. The modified TS-1 is able to serve as a stable catalyst for continuous cyclohexanone ammoximation. [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NOx) and soot which come from vehicle engine exhausts cause serious environmental pollution and human health problems. Recently, the catalytic purification technology, particularly the simultaneous catalytic removal of soot and NOx, has received more and more attention. For this technology, the key is to develop highly efficient and robust catalysts. Due to the unique chemical and structural properties of layered double hydroxides (LDHs), LDH-derived catalysts have shown great potential, and much effort has been devoted to this type of catalyst. In this manuscript, we reviewed the latest progress in the LDH derived catalysts by classifying the LDH precursors according to the number of metals into binary, ternary, and quaternary, and discussed their advantages and disadvantages in detail. We hope that this review paper could provide a clearer picture of this topic and theoretical support for its better development. [ABSTRACT FROM AUTHOR]

Development of magnetic nanoparticles (MNPs) for use as supports and exploration of their applications in aqueous catalysis represent an important branch of green chemistry as they enable environmentally friendly and sustainable catalytic processes. Besides the significant merit of easily recovering magnetic nanoparticles from reaction systems, various strategies through surface modification, grafting and selfassembly offer a broad range of approaches for constructing magnetically recoverable heterogeneous catalysts. In this review, we focus on the green catalytic processes and summarize recent advances in organic transformations catalyzed by magnetically recoverable catalysts (MRCs). This paper is divided into two main parts: the first part provides background information on the general preparation, modifications, and characterization, where the modifications of various magnetic nanoparticles through coating with silica, carbon, metal, or polymer are also presented. The second part provides a basic outline of aqueous catalysis based on water-only or water-and-organic solvent cosolvent systems, in which numerous types of organic transformations are catalyzed by magnetically recoverable catalysts. Lastly, perspectives for further development of magnetically recoverable heterogeneous catalysts in aqueous catalysis are addressed. [ABSTRACT FROM AUTHOR]

Nowadays, the vigorous development of biomass catalytic valorization is gradually moving towards a promising era. Integrating nitrogen elements into biomass catalytic systems promises more possibilities for upgrading the roadmap of biomass feedstocks. The amination of lignin to cyclohexylamine and its derivatives is a potential alternative to the fossil-based pathway. One-pot catalytic amination of lignin model compounds is challenging and inefficient due to their structural characteristics. Concerning the amination pathway, cyclohexanone and cyclohexanol are important intermediates. Based on this, we discuss the structural preferences of catalysts in the selective hydrogenation process, as well as the amination process of cyclohexanone and cyclohexanol to guide the design of catalysts for the one-pot amination of lignin. Then, the catalytic amination systems are deeply analyzed based on their catalytic conditions. Finally, according to the current development status of lignin amination, the challenges and prospects are proposed for a better lignin valorization. [ABSTRACT FROM AUTHOR]

Homogenization of heterogeneous catalysts is a valuable and interesting research topic. Porous polypyridine-oxadiazole (PPO), as not only a carrier but also a ligand, was designed and synthesized from pyridine-oxadiazole and 1-iodo-4-vinylbenzene. Iridium was anchored onto the skeleton of this polymer (ligand) through coordination bonds. This porous polypyridine-oxadiazole iridium catalyst (PPO-Ir) was clearly characterized by XRD, BET, EDS, HRTEM, SEM, and XPS, and revealed high catalytic activity for the reaction of dimethyl-6-aminouracil with benzyl alcohols, 1,3-dimethylbarbituric acid with benzyl alcohols and 2-aminobenzylamine and benzyl alcohols through dehydrogenation and the borrowing hydrogen strategy with alcohol or water as the solvent. In addition, this PPO-Ir catalyst could be recycled and reused without a manifest loss of catalytic activity for at least five times and revealed potential application value. The mechanism explorations were further conducted to clarify this PPO-Ir and these transformations. [ABSTRACT FROM AUTHOR]

The present report focuses on the solvent effect on furfural production from xylose in biphasic systems with methods including combined experiments, molecular dynamics (MD) simulations and density functional theory (DFT) calculations. Six most effective and commonly used biphasic solvents for furfural production were comparatively analyzed and discussed based on the kinetic study, partition coefficient, degradation behavior of furfural in organic solvents, distribution of solvent molecules around xylose/furfural molecules, hydrogen bonding, moving trajectories of xylose/furfural, and the solvation free energy. During the hydrothermal reaction of xylose to furfural in biphasic systems, it was found that the conversion efficiency of biphasic systems can be ordered as DCM/H2O > 2-MTHF/H2O > 2-butanol/H2O ≈ MIBK/H2O > CPME/H2O > toluene/H2O according to the xylose conversion and furfural yield, which are dominated by the solvation free energy (ΔGsol) of furfural in organic solvents, and also be affected by three other factors, namely, the maximum solubility of furfural in organic solvents, the ΔGsol value of organic solvents in water, and the side reaction of furfural in organic solvents. The degradation rate of furfural in 2-butanol was detected to be the fastest, and molecular dynamics simulation data showed that the hydrogen bonding between furfural and 2-butanol may accelerate the degradation of furfural. DCM has excellent extraction ability for furfural, and the maximum furfural yield in the DCM/H2O system (81.64%) is much higher than that in other systems during the hydrothermal reaction without additional catalysts. [ABSTRACT FROM AUTHOR]

Lignin nanosizing has received much interest as it offers new potential for value-added applications of the currently under-utilized lignin biopolymers. However, conventional lignin nanosizing technologies often rely on the use of large amounts of toxic organic solvents, and a time-consuming dialysis process that is required to remove the solvents. Herein, we present a novel and effective approach using a binary system consisting of green γ-valerolactone (GVL) and glycerol solvents to prepare lignin nanospheres (LNS) without lignin modification and additional dialysis processes. The rationale of LNS formation lies in the emulsification of uniform lignin-containing GVL droplets in glycerol by a process consisting of (1) heating to 80 °C, and (2) cooling to room temperature. Through this simple process, we obtained very high LNS yield (over 90%), with narrow size distribution (about 275 nm) by using maple kraft lignin as the raw material. This lignin nanosizing approach is universal when applied to different sources/types of lignins. The as-prepared LNS were further applied as a green reducing agent and carrier for the synthesis of Pd nanoparticles (NPs) in a facile in situ reduction process. Pd@LNS exhibited significantly enhanced catalytic capacity in the hydrogen evolution from formic acid and in the reduction of Cr(VI) to Cr(III) compared with bare Pd NPs. The Pd@LNS catalyst demonstrated high recyclability owing to the good chemical stability of LNS and robust loading of Pd NPs on LNS. Consequently, this work offers a green, universal and effective approach for LNS fabrication and presents a promising application of LNS as metal NP carriers for catalysis purposes. [ABSTRACT FROM AUTHOR]

We demonstrate a lamellar NiMoCo@CuS catalyst, showing not only an excellent catalyst performance (η100@72 mV and a Tafel slope of 47 mV dec−1), but also a good stability (20 mA cm−2@30 hours), outperforming the NiMo system and noble Pt. [ABSTRACT FROM AUTHOR]

Single-atom catalysts are emerging as primary catalysts for many reactions due to their 100% utilization of active metal centers leading to high catalytic efficiencies. Herein, we report the use of a single-atom Co catalyst for the oxidative cleavage of the β-O-4 bonds of lignin model compounds at a low oxygen pressure. Under the optimized reaction conditions, the conversion of 2-(2-methoxyphenoxy)-1-phenylethanol up to 95% with high selectivities was achieved with a variety of substrates investigated. The reusability of the Co catalyst with a high catalytic efficiency indicates its potential application in the oxidative cleavage of C–O bonds. [ABSTRACT FROM AUTHOR]

The conversion of renewable biomass resources into fuels, polymers, and fine chemicals provides solutions for the growing shortage of fossil resources, environmental pollution and a possible crisis in energy supply. 5-Hydroxymethylfurfural (HMF) is an important biomass-derived platform chemical, and its selective oxidation to multifunctional molecules such as 2,5-diformylfuran (DFF) remains an ongoing challenge. The present work reports a sustainable, cost-effective, and highly efficient catalytic system for directly transforming HMF to DFF that afforded ＞99% DFF yield under relatively mild reaction conditions. The reaction was catalyzed by naturally abundant and non-noble Fe–Co based catalysts derived from a metal–organic framework (MIL-45b) employed as a sacrificial template. The unique hollow structure of the nanomaterial favored the adsorption of HMF and quick desorption of the formed DFF from the catalyst surface, leading to a high yield of DFF that could be comparable to that obtained with noble metal catalysts under similar conditions. The catalyst could also be easily recovered and reused up to six runs without any significant loss in reactivity. [ABSTRACT FROM AUTHOR]

A simple and highly efficient nanostructured catalyst system comprising magnetic Co nanoparticles stabilized by N-doped carbon composite (Co/C–N) was synthesized by one-pot thermal decomposition of a Co-containing MOF. The catalysts were characterized by temperature programmed desorption (TPD), N2 physical adsorption, powder X-ray diffraction (PXRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electronic microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The catalytic activity of Co/C–N materials was investigated in the selective aerobic oxidation of alcohols in neat water under an atmospheric pressure of air and base-free conditions. As compared to those prepared by traditional impregnation methods, Co/C–N exhibited an efficient performance with significantly improved catalytic activities. Besides conferring high activity and selectivity to the target products, the proposed catalytic system featured a broad substrate scope for both aryl and alkyl alcohols. Furthermore, the magnetically recoverable Co/C–N catalyst could be easily separated from the reaction system by using an external magnetic field and reused at least five times without any significant loss in catalytic efficiency under the investigated conditions. [ABSTRACT FROM AUTHOR]