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In this paper, the effect of the hierarchical arrangement of nanocrystallites on CO oxidation and soot combustion activity has been investigated. Hierarchically structured star-shaped particles (HS stars) were compared with microemulsion-derived, loosely arranged nanoparticles (NPs). Star-like Ce0.9REE0.1O1.95 mixed oxides were synthesized by oxidative thermolysis of Ce0.9REE0.1(HCOO)3 mixed formates. The study of the synthesis, structure and catalytic activity of the porous, star-like ceria-based mixed oxides was presented for the first time. It was shown that each level of the hierarchical structure of the star-like mixed oxides has its own functionality and it is vulnerable to modifications. In-depth characterization of as-synthesized ceria allowed determination of the relationship between the hierarchically structured nature of the material and its catalytic activity in CO oxidation and soot combustion. It was concluded that the presence of the 3D structure composed of ceria nanocrystals significantly improves the stability and catalytic activity of the star-like material in comparison to the nanopowder. Moreover, introduction of the trivalent RE ion into the ceria structure led to further improvement of the CO oxidation performance. Finally, the key–lock catalysis concept was applied to explain the enhanced activity of the hierarchically structured star-shaped ceria particles as a catalyst in the soot combustion process in comparison to nanocrystalline CeO2. [ABSTRACT FROM AUTHOR]

In this paper, the heterogeneous nature of an amorphous SiO2 support, the exceptional properties of polyamidoamine dendrimers (PAMAM), and the unique properties of pincer ligands (NNN type) were combined for immobilization of a triazine-derived Cu(II)-NNN pincer complex onto the dendritic nanoparticle supports. All of the prepared samples in each step were fully characterized and compared by several techniques, including FTIR, TGA–DTG, elemental analysis (EA), SEM, and TEM. In this regard, two different methods were applied and used for the synthesis and growth of a PAMAM dendrimer onto the SiO2 support via the divergent synthesis method (without and with the catalyst). In the presence of a tetrabutylammonium bromide (TBAB) catalyst, dendritic supports were prepared in a shorter time with better growth. Subsequently, a symmetric and neutral tridentate NNN-pincer ligand derived from trichloro-1,3,5-triazine/2-aminopyridine was immobilized on each of these dendritic nanoparticle supports. The successful immobilization of a pincer ligand on the nanoparticle dendritic support was also supported by the techniques mentioned above. Finally, the reaction of each prepared support with copper(II) chloride at room temperature resulted in the formation of immobilized Cu(II)-NNN pincer complexes as partially supported by EPR and UV-vis spectroscopy. The loading of the copper ions for each sample was measured by ICP/OES analysis. Among the five final immobilized ligands, the NNN pincer-G′1-SiO2 (G′1 = the first generation of PAMAM dendrimers prepared via the second method) showed more suitable ability for copper adsorption. [ABSTRACT FROM AUTHOR]

The catalytic properties of metal–organic frameworks (MOFs) containing triangular Fe(III) clusters in the promotion of organic syntheses and photocatalysis applications have been receiving substantial attention for decades. These clusters are appealing due to the strong Lewis acidity afforded by coordinatively unsaturated sites upon the removal of solvent from the framework. In this paper, triangular Fe(III) cluster-based MOFs were shown to be highly efficient heterogeneous catalysts for the solvent-free one-pot condensation of 2-aminobenzamide and alcohols to form quinazolin-4-ones under microwave irradiation. The Fe-MOF catalysts ranging from microporous to mesoporous structures with a variety of geometrical pore structures were investigated. Because of the open accessible spaces for reactants and high density of active sites, MOF-907, built from trimer Fe clusters and a mixture of two linkers, was more effective than other Fe(III)-MOFs. The catalyst can be used for a broad substrate scope and recycled several times without a significant drop-off in its activity. [ABSTRACT FROM AUTHOR]

In this paper, a new visible-light harvesting photocatalyst denoted as g-C3N4/γ-Fe2O3/TiO2/Pd was successfully fabricated and fully characterized by different techniques including FT-IR, XPS, XRD, TEM, SEM, elemental mapping, VSM, DRS, and ICP analysis. The as-prepared catalyst was utilized as an efficient magnetically separable photocatalyst in the fluoride-free Hiyama and Suzuki–Miyaura cross-coupling reactions at room temperature under visible light irradiation. By using this approach good to excellent yields of biaryls were achieved from the reaction of various aryl iodides/bromides and even chlorides as highly challenging substrates, which are more available and cheaper than aryl iodides and bromides, with triethoxyphenylsilane or phenylboronic acid. The superior photocatalytic activity of g-C3N4/γ-Fe2O3/TiO2/Pd could be attributed to the synergistic catalytic effects of Pd nanoparticles and g-C3N4/γ-Fe2O3/TiO2. Utilizing a sustainable and safe light source, no need to use any additive or heat, using an eco-friendly solvent and long-term stability and magnetic recyclability of the catalyst for at least seven successive runs are the advantages that support the current protocol towards green chemistry. [ABSTRACT FROM AUTHOR]

A Cu-based bimetallic hollow structure can be effectively used to enhance the selective oxidation and electrocatalytic activity of a catalyst and to reduce its cost. In this paper, we developed a facile and scalable method for the construction of CuAu bimetallic hollow particles from Cu2O nanoparticle aggregates (NPAs). The synthetic process includes Au growth on the Cu2O NPA surface and silica encapsulation, which is followed by polyol reduction of Cu2O, calcination in air and etching of the SiO2 layer. The obtained hollow CuAu NPs (average diameter of 540 nm and wall thickness of 60 nm) outperform hollow Cu NPs in terms of catalytic activity in the reduction of 4-nitrophenol by NaBH4 in aqueous solution. The activity factors (K = 354 and 255 s−1 g−1) are 2.4 and 1.7 times larger than that of the hollow Cu catalyst, depending on the Au content in the CuAu particles. In addition, the prepared catalyst was stable in the reaction system and can be recycled via centrifugation without a significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

This paper reports for the first time the preparation of Co3O4 nanorods by simple hydrothermal and annealing methods, which are doped with polyoxometalates that act as an intermediary in electronic transmission to accelerate electron transport. The designed H3PW12O40(PW12)/Co3O4–Cu2S composite film was prepared by the screen printing method to boost its efficiency as the counter electrode for quantum dot-sensitized solar cells, where the preparation process is simple and inexpensive. PW12/Co3O4–Cu2S (Jsc = 16.60 mA cm−2, Voc = 0.636 V, Rct = 0.32 Ω and FF = 0.436) shows better electrocatalytic performance compared to the original Co3O4 and Cu2S. Accordingly, the photoelectric conversion efficiency of PW12/Co3O4–Cu2S is 4.67%, which is 10%, 46%, 55.6%, and 72% higher than those of Co3O4–Cu2S (4.2%), Cu2S (2.54%), PW12/Co3O4 (2.07%), and Co3O4 (1.30%), respectively. Electrochemical impedance spectroscopy and Tafel measurements performed on two CE symmetric virtual cells proved the excellent electrocatalytic activity of PW12/Co3O4–Cu2S. Therefore, this composite film can be used as an alternative option for QDSSC counter electrodes. [ABSTRACT FROM AUTHOR]

para-Xylene (PX) is a basic building block of polyethylene terephthalate, which is currently produced from petroleum resources. Developing a renewable route to PX is highly desirable to address both economic and environmental concerns. Several attempts used noble metal catalysts, e.g. Pd/Al2O3, to synthesize PX from biomass-derived 4-methyl-3-cyclohexene-1-carboxaldehyde (4-MCHCA), but suffered from a severe decarbonylation reaction, resulting in toluene as the main product. In this paper, we report an FeOx modification strategy to suppress the decarbonylation reaction on a Pd/Al2O3 catalyst, leading to a drastic shift in selectivity towards PX with a yield up to 81% via a cascade dehydroaromatization–hydrodeoxygenation (DHA–HDO) pathway. Characterization and control experiments revealed that the electron density of Pd sites decreased in an FeOx-modified Pd/Al2O3 catalyst compared to Pd/Al2O3, thus tuning the preferential adsorption mode of the substrate from η2-(C,O), the key transition state of the decarbonylation reaction, to the η1-(O) mode that favors the hydrodeoxygenation process. Notably, this designed catalyst is highly stable and is readily applicable in the selective synthesis of a broad range of desired aromatic chemicals via the same DHA–HDO pathway from cyclohex-3-enecarbaldehyde derivatives. Overall, this work develops a controllable catalyst modification strategy that tailors an efficient catalyst for petroleum-independent bio-PX synthesis. [ABSTRACT FROM AUTHOR]

This paper reports on a binuclear Co(II)Pc which exhibits a previously unknown extremely high catalytic activity for the oxidation of a thiol to the corresponding disulfide. The high activity is explained by an electronic contact between the two Co centres in the complex. [ABSTRACT FROM AUTHOR]

Iron-catalysed 1,2-acyl migration of tertiary α-azido ketones and 2-azido-1,3-dicarbonyl compounds provides a simple and atom-economical approach toward enamides and isoquinolones. This paper reports two catalyst systems for these transformations which employ iron(II) complexes [Fe(dpbz)]Br2 (dpbz = 1,2-bis(diphenylphosphino)benzene) and FeBr2/Et3N, respectively. [Fe(dpbz)]Br2 was found to be highly effective at converting 2-azido-2,3-dihydro-1H-inden-1-ones to isoquinolones. The reagent combination of FeBr2/Et3N, on the other hand, exhibited a broader catalytic scope, owing to the beneficial effect of Et3N. This latter catalyst system enables 2-azido-2-methyl-1,3-dicarbonyl compounds to be converted to the corresponding enamides under mild conditions in good yields. [ABSTRACT FROM AUTHOR]

This paper reports a possible mechanism of acetic acid formation from CO2, CH3I and H2 in aqueous media and the central role played by a water-soluble Rh-based electron storage catalyst. In addition to water-solubility, we also report the crystal structures of two presumed intermediates. These findings together reveal (1) the advantage of water, not only as a green solvent, but also as a reactive Lewis base to extract H+ from H2, (2) the role of the metal (Rh) centre as a point for storing electrons from H2 and (3) the importance of an electron-withdrawing ligand (quaterpyridine, qpy) that supports electron storage. [ABSTRACT FROM AUTHOR]

Cobalt has been extensively studied as an effective catalyst for the electrooxidation of sodium borohydride. However, there is still the problem of the low catalytic activity of cobalt catalysts. The improvement in the catalytic activity of cobalt for the electrooxidation of sodium borohydride has become a challenge. In this paper, a novel catalyst Co–P alloy was supported on a copper foam (CF) substrate by a one-step electrodeposition method. In the electrodeposition process, a Co–P/CF electrode with a three-dimensional (3D) porous structure was successfully prepared using hydrogen bubbles as a dynamic template. Through the physical characterization of Co–P/CF, it was proven that the doping of P element produced more Co clusters on the surface of the electrode, which resulted in more active sites. These characteristics were very beneficial for NaBH4 electrooxidation. The electrochemical characterization confirmed that the electrocatalytic activity of Co–P/CF for NaBH4 was better than that of Co/CF. At room temperature, for the Co–P/CF in 2.0 mol dm−3 NaOH + 0.20 mol dm−3 NaBH4 solution, the oxidation current density reached 1795 mA cm−2 at −0.20 V (vs. Ag/AgCl), which was higher than that previously reported the literature. [ABSTRACT FROM AUTHOR]

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]

An effective and safe route is proposed to prepare supported Mo2C-based catalysts from organic–inorganic hybrids, which exhibit high activity and stability for producing H2from methanol catalytic decomposition. [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]

The preceding paper (Dalton Trans., 2008, DOI: 10.1039/b806100a) describes the logical development of a chemical mechanism for the catalysis of hydrogenation of N2to 2NH3that occurs at the Fe7MoS9Nc(homocitrate) cofactor (FeMo-co) of the enzyme nitrogenase. The mechanism uses a single replenishable path for serial supply of protons which become H atoms on FeMo-co, migrating to become S–H and Fe–H donors to N2and to the intermediates that follow. This chemical catalysis at FeMo-co is distinctly intramolecular: transition states and reaction profiles for the preferred 21 step pathway were presented. This paper describes a number of alternative intermediates and pathways that were considered in developing the mechanism. These results reveal further relevant principles of the reactivity of hydrogenated FeMo-co, and the reasons why these pathways are less likely to be part of the mechanism. The intramolecular character of the mechanism, and the relatively small distances over which H atoms transfer, lead to expectations of extensive quantum mechanical hydrogen tunneling as part of the catalytic rate enhancement. This possibility is supported by comparisons of reaction profiles with those for enzyme reactions for which tunneling is established. [ABSTRACT FROM AUTHOR]

Methane gas is known to be the most destructive greenhouse gas. The current world reserves of natural gas, which contains mainly methane, are also still underutilized due to high transportation costs. Thus, considerable interest is presently shown in conversion of methane to transportable liquid fuels and chemicals of importance to the petrochemical industry. The catalytic methylation of aromatics is one possible new route for converting methane to more valuable higher hydrocarbons. This paper provides a general overview of the recent work that we and other researchers have done on the utilisation of methane for catalytic methylation of aromatic compounds and for direct coal liquefaction for the production of liquid hydrocarbons. In particular, the paper presents a detailed description of more recent substantial experimental evidence that we have provided for the requirement of oxygen as a stoichiometry reactant for benzene methylation with methane over moderately acidic zeolite catalysts. The reaction, which has been termed “oxidative methylation”, was thus postulated to involve a two-step mechanism involving intermediate methanol formation by methane partial oxidation, followed by benzene methylation with methanol in the second step. However, strongly acidic zeolites can cause cracking of benzene to yield methylated products in the absence of oxygen. The participation of methane and oxygen, and the effective use of zeolite catalysts in this methylation reaction definitely have some positive green chemistry implications. Thus, the results of these previous studies are also discussed in this review in light of the principles and tools of green chemistry. Various metrics were used to evaluate the greenness, cost-effectiveness, and material and energy efficiency of the oxidative methylation reaction. [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]

Understanding the kinetics of olefin polymerization with Ziegler–Natta and related catalysts means identifying the main kinetic parameters such as kp and concentration of active sites. The high-pressure quenched-flow technique could be an absolute method for counting active sites and for activation studies of molecular catalysts. A kinetic study of metallocene catalysts and a phenoxy-imine titanium catalyst in the first instants of polymerization is presented in this paper. [ABSTRACT FROM AUTHOR]

As more and more novel catalyst systems are being developed for the dehydration of carbohydrates, especially glucose, an effective way to separate the dehydration product 5-hydroxylmethylfurfural (5-HMF) is also required for industrial manufacturing. In this paper, for the first time, we have developed a process called EIVRD (entrainer-intensified vacuum reactive distillation) to separate 5-HMF from the dehydration solutions of carbohydrates catalyzed by a metal chloride/1-methyl-3-octyl imidazolium chloride ([OMIM]Cl) ionic liquid, in which high vacuity and entrainers were applied to intensify the distillation of 5-HMF as well as the dehydration of fructose or glucose. In such an EIVRD process, the average recoveries of 5-HMF dehydrated from fructose and glucose are around 93% and 88%, respectively. The recycling of the catalyst system in the EIVRD process is so convenient that the recovery and actual yield of 5-HMF is successfully repeated during the whole five recycled reactions. [ABSTRACT FROM AUTHOR]

Ionic liquids are of great interest as potential solvents/catalysts for the production of fuels and chemicals from lignocellulosic biomass. Attention has focused particularly on the pretreatment of lignocellulose to make the cellulose more accessible to enzymatic hydrolysis. Any biomass processing requires a reduction in the size of the harvested biomass by chipping and/or grinding to make it more amenable to chemical and biological treatments. This paper demonstrates that significant energy savings can be achieved in the grinding of pine wood chips when the ionic liquid is added before the grinding operation. We show that this is due to the lubricating properties of the ionic liquids and not to physico-chemical modifications of the biomass. A brief impregnation of the chipped biomass results in higher savings than a longer treatment. [ABSTRACT FROM AUTHOR]

Carbosilylation is a straightforward procedure to install both silyl and organic functional groups onto organic molecules. For example, allylsilylation of alkenes with allylsilanes affords 5-silyl-1-pentene derivatives. In this review paper, catalytic allylsilylations and arylsilylations of alkenes, alkynes, and cyclic acetals are summarized. Specific catalyses of Lewis and Brønsted acids, such as HfCl4 and proton-exchanged montmorillonite, will be discussed. Intramolecular reactions as well as intermolecular allyl- and arylsilylations have been achieved. In the case of the Brønsted acid catalyst, cationic Si species generated and acted as catalytically active species. The structure of the cationic Si species depends on the type of Brønsted acid used. A disilyl cation was proposed as the catalytically active site for carbosilylations of alkenes and alkynes, while a monomeric Si species was active for allylsilylation of cyclic acetals. [ABSTRACT FROM AUTHOR]

In this paper, the effect of particle size on Laser-Induced Breakdown Spectroscopy (LIBS) analysis of mesoporous V–SiO2catalyst samples was investigated. The measurements were realized on three LIBS devices with different parameters. Concentrations of V in samples used for LIBS experiments previously determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) varied from 1.2 to 4.7 w/w%. Granulometry of silica samples was modified by two grinding methods (conventional vibration mill and cryogenic mill) and three sets of samples with different particle size distributions were obtained. Ground samples were then deposited in the form of a thin layer on the adhesive tape and analysed by LIBS. Curves describing the relationship between the vanadium concentration and the corresponding intensity of LIBS signal (C–Icurves) were constructed for all three groups of samples, with different granulometry profiles measured with three different LIBS devices. The C–Icurves for samples with narrow particle size distribution showed the highest values of slopes. Detection limits achieved were in the range 0.063–0.012% (w/w). The best LOD values were obtained for samples with the lowest mean particle size. [ABSTRACT FROM AUTHOR]

In this paper we report on the one-pot transformation of glycerol into acrylic acid, catalyzed by W/V mixed oxides, with hexagonal tungsten bronze (HTB) structure. The reaction requires two different catalyst functions, i.e., an acid one, which is given by W oxide, and an oxidizing one, given by the V ions incorporated within the WO3 lattice. W–O bronze is very active and moderately selective in acrolein formation, but yields only traces of acrylic acid. The incorporation of increasing amounts of V inside the hexagonal tungsten bronze structure, with the development of a monophasic compound, allows the consecutive oxidation of acrolein into acrylic acid. An optimal atomic ratio between W and V equal to V/(W + V) = 0.12–0.21 made it possible to obtain an acrylic acid yield of 25% (with selectivity to residual acrolein of 11%). However, during reaction under the oxygen-containing feed, the V4+ incorporated into the hexagonal bronze structure underwent a slow oxidation into V5+, which caused a progressive decline of selectivity to acrylic acid and a concomitant increase of COx formation; the hexagonal structure however was stable during lifetime experiments. On the other hand, in the absence of oxygen a very rapid deactivation of the catalyst occurred, with a decrease in selectivity to acrolein and increase in heavy by-products. [ABSTRACT FROM AUTHOR]

Exploitation of hydrogen as an energy carrier requires the development of systems for its storage and delivery. Formic acid has been proposed as valuable hydrogen carrier compound, due to its relatively high hydrogen content (53 g L−1), the latter being easily and cleanly released in catalytic reactions under mild conditions (HCOOH → H2 + CO2). Ionic liquids are interesting solvents for homogeneous catalyzed formic acid decomposition systems as their extremely low volatility avoids solvent contamination of the produced hydrogen stream. In this paper an outstandingly simple, robust and active catalyst system is presented, namely RuCl3 dissolved in 1-ethyl-2,3-dimethylimidazolium acetate (RuCl3/[EMMIM][OAc]). This system proved to be fully recyclable over 10 times. Turnover frequencies (TOF) of 150 h−1 and 850 h−1 were obtained at 80 °C and 120 °C, respectively. [ABSTRACT FROM AUTHOR]

Free-standing one-dimensional (1D) wires, two-dimensional (2D) platelets (triangular and hexagonal in shape) of iridium (Ir) and iridium dioxide (IrO2) with open-ends and flower-like structures have been prepared successfully in the absence of a catalyst or template by a simple annealing process. This paper describes the first examples of the growth of 1D Ir wires and 2D Ir platelets. The Ir wires and platelets grown at an angle on sapphire were over a few tens of micrometres long. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) observations revealed that Ir wires and IrO2rods are grown in the preferential orientation along [110] and [001] directions, respectively. The probable growth models for the formations of the Ir and IrO2nanostructures are proposed. Electrical measurements indicated that the highly crystalline Ir wires had a low resistivity and exhibited electronic transport properties similar to bulk Ir. The failure current density was greater than 1 × 108A cm−2. This value is comparable to that reported for Pt nanobelts (1 ×107A cm−2) and silver nanobeams (1.8 × 108A cm−2). These unique Ir wires are attractive nanoscale building blocks for potential use as electrodes in nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Non-toxic DAlCs, especially lighter dimethyl- and diethyl-carbonate, are regarded as very green alkylating reagents, particularly when coupled with metal-exchanged Y- and X-faujasites as catalysts. These reactions are selective, free from wastes or byproducts, and often require no additional solvent other than the carbonate. Nonetheless, this paper demonstrates that the operating temperature and the nature of the faujasite must be carefully chosen in order to avoid DAlC decomposition. In fact, at temperatures ranging from 150 to 240 °C, faujasites can promote decarboxylation of light DAlCs to the corresponding ethers CH3OCH3and CH3CH2OCH2CH3plus CO2. Heavier DAlCs (dipropyl- and dioctyl-carbonate) undergo a similar decomposition pathway, followed by further reactions to the corresponding alcohols (n-propanol and n-octanol) and alkenes [propylene and octene(s)]. These transformations not only consume DAlCs, but also give rise to dangerously flammable ethers, as well as undesirable alcohols, alkenes and CO2. The present work reports an original investigation of the decarboxylation of DAlCs on faujasites with the aim of providing operative boundaries to the experimental conditions to minimise unwanted decomposition. The reaction is strongly affected by the nature of the catalyst: the more basic zeolites, NaX and CsY, are by far more active systems than NaY and LiY. However, solid K2CO3proves to be rather inefficient. The temperature also plays a crucial role: for example, the onset of the decarboxylation of DMC requires a temperature of ∼30 °C lower than that for DEC and DPrC. Overall, awareness that certain zeolites cause decomposition of DAlCs under conditions similar to the ones used for DAlC-promoted alkylations allows determination of the correct experimental boundaries for a safer and more productive use of DAlCs as alkylating agents. [ABSTRACT FROM AUTHOR]

Furfural production through traditional processes is accompanied by acidic waste stream production and high energy consumption. Modern furfural production process concepts will have to consider environmental concerns and energy requirements besides economics, moreover will have to be integrated within widened biorefinery concepts. In this paper, some particular aspects of the chemistry of d-xylose reaction to furfural are addressed, with the aim to clarify the reaction mechanism leading to furfural and to define new green catalytic pathways for its production. Specifically, reducing the use of mineral acids is addressed by the introduction of alternative catalysts. In this sense, chloride salts were tested in dilute acidic solutions at temperatures between 170 and 200 °C. Results indicate that the Cl−ions promote the formation of the 1,2-enediol from the acyclic form of xylose, and thus the subsequent acid catalyzed dehydration to furfural. For this reason the presence of Cl−ions led to significant improvements with respect to the H2SO4case. The addition of NaCl to a 50 mM HCl aqueous solution gave 90% selectivity to furfural. Among the salts tested FeCl3showed very interesting preliminary results, producing exceptionally high xylose reaction rates. [ABSTRACT FROM AUTHOR]

This contribution reports about an in situFT-IR investigation and the catalytic reactivity of Mg/Me3+mixed oxides (Me = Cr, Fe, or Al; Mg/Me = 2, atomic ratio) in the gas-phase methylation of phenol with methanol. It is the second of two papers concerning the mentioned systems, and its purpose is twofold: to confute the classic and not accurate theory concerning the reaction mechanism, and to propose a novel interpretation based on the combined use of catalytic tests and in situmolecular spectroscopy. Results here reported highlight that: (i) the reaction mechanism in phenol methylation, when catalysed by basic systems, is not a classical electrophylic substitution, as generally reported in the literature, but proceeds through the formation of formaldehyde as an intermediate, and (ii) the catalytic behaviour in respect to both methanol and phenol reactants is strictly dependent on catalyst features. Although all investigated systems exhibit a basic-type behaviour with regard to phenol, which dissociates to yield an adsorbed phenolate species, the distribution of phenolic compounds obtained with the Mg/Al/O catalyst was that typically observed with acid catalysts, with prevailing formation of anisole when the reaction was carried out below 350 °C and of mono and poly-C-alkylated compounds when the reaction temperature was above 350 °C. On the contrary, the reactivity shown by both Mg/Fe/O and Mg/Cr/O systems was that reported in the literature as typical of mixed oxides possessing basic features. The extent of methanol decomposition into light compounds was maximum in the case of Mg/Fe/O catalysts, because of the pronounced redox behaviour typical of Fe3+species, whereas neither methanol dehydrogenation nor decomposition were ever observed with Mg/Al/O up to 400 °C. Reactivity tests and spectroscopic experiments hinted for methanol dehydrogenation to formaldehyde as the first step in the ring-methylation of phenol with Mg/Cr/O and Mg/Fe/O: in that case, o-cresol and 2,6-xylenol were the only reaction products. But, with Mg/Al/O systems, for which no methanol dehydrogenation occurred, the formation of anisole was due to the synergistic effect of stronger basic features and the presence of Lewis acidic sites, that facilitate the reaction between phenol and methanol after activation over the two different types of catalytic sites. [ABSTRACT FROM AUTHOR]

An efficient method for dispersing active metal colloidal nanoparticles onto supports uniformly is revealed in this paper. The critical feature of this method is to separate the stabilizer simply with the phase-switch function of scCO2; with it the highly dispersed Pd colloidal catalysts were prepared, and the forming procedure is analyzed and discussed in detail. The present work not only overcame the common difficulties of removing the stabilizers in the preparation of supported colloidal particles, but also provided a facile and green process for preparing supported metal colloidal nanoparticles with using the environmentally benign solvent of scCO2. [ABSTRACT FROM AUTHOR]

A series of α-acyloxyacrylate esters are candidate monomers for bio-based polymers, converted from biomass feedstock. Polymers from these monomers are useful materials for bio-based plastics showing high heat resistance and transparency. In this paper, a new efficient method for α-acyloxyacrylate ester synthesis with a strong inorganic acid, heteropolyacid, is presented. The reaction in the presence of the heteropolyacid catalyst was carried out in liquid phase under mild conditions and showed higher productivity than that of the conventional synthesis with a typical organic acid, p-toluenesulfonic acid. Among the various heteropolyacids examined, α-Keggin-type tungsten-based phosphotungstic acid, H3PW12O40, showed the best performance, suggesting that the acid strength of the heteropolyacid is the crucial property for this reaction. We also found that pyruvate ester was consecutively converted into α-acyloxyacrylate ester via2,2-diacyloxypropionate ester. [ABSTRACT FROM AUTHOR]

While the purification of carbon nanotubes may be considered as an already sorted matter, their use in some highly demanding fields such as electrochemistry, biological studies or magnetism may be precluded by the remaining catalyst and carbonaceous impurities. For these purposes, the widely-used purification methods need to be improved. In this paper, a comprehensive study of the well-known gas-phase purification procedure of single wall nanotubes (SWNTs) is performed, which aims at depicting the nature and the amount of the remaining impurities, of both the catalyst and carbon types, and at getting insights into its mechanism. This has been achieved by cross-referencing data emerging from transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), electron diffraction, magnetization measurements, X-ray diffraction (XRD) and Raman spectroscopy. We demonstrate that this method can lead to the elimination of the largest part of the impurities while maintaining fairly good yields. According to the mechanistic picture we have drawn, we suggest some possible improvement to the procedure that should lead to fully purified SWNTs with limited subsequent losses. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed transformations of aryl halides and pseudo-halides involving carbonylation, carbon–carbon and carbon–heteroatom bond-forming reactions, etc. are very well documented, and have already been reviewed several times. The metal-catalyzed activation of benzylic derivatives is much less described. However, during the last decades, a number of papers have shown the interest offered by benzylic derivatives (halides, carbonates, acetates, phosphonates) in selective catalytic reactions for organic synthesis, most of them in the presence of palladium catalysts. The purpose of this tutorial review is to highlight selected examples of palladium-catalyzed transformations involving reactive benzylic derivatives. [ABSTRACT FROM AUTHOR]

The carbonylation of methanol to acetic acid is a hugely important catalytic process, and there are considerable cost and environmental advantages if a process could be designed that was tolerant of hydrogen impurities in the CO feed gas, while eliminating by-products such as propionic acid and acetaldehyde altogether. This paper reports on an investigation into the application of rhodium complexes of several C4 bridged diphosphines, namely BINAP, 1,4-bis(diphenylphosphino)butane (dppb), bis(diphenylphosphino)xylene (dppx) and 1,4-bis(dicyclohexylphosphino)butane (dcpb) as catalysts for hydrogen tolerant methanol carbonylation. An investigation into the structure, reactivity and stability of pre-catalysts and catalyst resting states of these complexes has also been carried out in order to understand the observations in catalysis. Rh(i) carbonyl halide complexes of each of the ligands have been prepared from both [Rh2(CO)4Cl2] and dimeric μ-Cl-[Rh(L)Cl]2 complexes. These Rh(i) carbonyl complexes are either dimeric with bridging phosphine ligands (dppb, dcpb, dppx) or monomeric chelate complexes. The reaction of the complexes with methyl iodide at 140 °C has been studied, which has revealed clear differences in the stability of the corresponding Rh(iii) complexes. Surprisingly, the dimeric Rh(i) carbonyls react cleanly with MeI with rearrangement of the diphosphine to a chelate co-ordination mode to give stable Rh(iii) acetyl complexes. The Rh acetyls for L = dppb and dppx have been fully characterised by X-ray crystallography. During the catalytic studies, the more rigid dppx and BINAP ligands were found to be nearly 5 times more hydrogen tolerant than [Rh(CO)2I2]−, as revealed by by-product analysis. The origin of this hydrogen tolerance is explained based on the differing reactivities of the Rh acetyls with hydrogen gas, and by considering the structure of the complexes. [ABSTRACT FROM AUTHOR]

Recently, sulfated zirconia has received considerable attention as a potential solid acid catalyst to replace problematic homogeneous acid catalysts. In this paper, the preparation and properties of acid catalysts obtained by grafting ziconia with atomic precision on MCM-41 mesoporous silica were studied. TEM and potential titration characterizations revealed that ZrO2/MCM-41 with monolayer coverage can be obtained using this grafting technique. Sulfated ZrO2/MCM-41 exhibits improved thermal stability than that of bulk sulfated zirconia, as evidenced by temperature programmed characterizations and XRD analysis. Temperature programmed reaction of isopropanol was used to evaluate the acidity of sulfated ZrO2/MCM-41. It was found that the acid strength of sulfated ZrO2/MCM-41 with monolayer coverage is weaker than bulk sulfated zirconia but stronger than SiO2–Al2O3, a common strong acid catalyst. [ABSTRACT FROM AUTHOR]

This paper provides a viable, reproducible and robust method for immobilising hydroxyl tethered iridium–rhodium complexes. The materials have been shown to be both effective and recyclable in the process of catalytic transfer hydrogenation with minimal metal leaching. [ABSTRACT FROM AUTHOR]

In this paper, polymer nanocapsules embedded with noble metal nanoparticles and showing a good catalytic activity were prepared by a novel and convenient method. [ABSTRACT FROM AUTHOR]

As a dual-functional catalyst for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), Ru clusters have great potential, but there are certain difficulties regarding their stability on the substrate and the tunability of their electronic environment. Here, the S doped graphited biochar aerogel electrocatalyst was designed and synthesized using terrestrial lignin and algal polysaccharide as a carbon substrate. The Ru clusters were anchored on the S-doped carbon aerogel (P-Ru/SC) by carefully designing the Ru-S bond via a novel plasma assisted high temperature carbonization treatment. The optimized P-Ru/SC-2 catalyst exhibits excellent electrocatalytic performance for the HER and OER, achieving ultra-small overpotentials of 119.6 mV and 193.4 mV at 10 mA cm-2. The dual-electrode requires only 1.47 V to reach 10 mA cm-2. It is worth noting that a large number of S sites on graphited carbon can strongly interact with the Ru clusters, significantly improving the catalytic activity and stability for the HER and OER. [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]