Surface engineering of biochar toward simultaneously generating superamphiphilicity and catalytic activity for strengthening Pickering interfacial catalysis.

Multifunctional carbon materials have revealed distinctive features and excellent performance in the field of catalysis. However, the facile fabrication of bifunctional carbon materials with special wettability and catalytic activity remains a grand challenge in Pickering emulsion catalysis. Herein, we reported one-step construction of bifunctional biochar with superamphiphilicity and catalytic activity directly from the thermolysis of sawdust and 1-butyl-3-methylimidazolium tetrafluoroborate for enhancing the oxidation of benzyl alcohol in Pickering emulsion. Co-doping of B and F enhanced the hydrophilicity of biochar, and the oleophilicity of biochar was kept simultaneously. Conversion became 4 times using bifunctional biochar compared with blank results during the oxidation of benzyl alcohol. More interestingly, the turnover frequency (TOF) value using bifunctional biochar enhanced 61% than that employing N-doped superamphiphilic carbon without catalytic activity. Catalytic activities of bifunctional biochar could be ascribed to the existence of different chemical bonds containing the element B. This work paves a path toward rational design of bifunctional biochar materials with special wettability and catalytic activity for greatly enhancing the liquid-liquid biphasic reaction efficiencies.

Kinetic Model for Denitration Reaction Process of Cylindrical Single-Base Gun Propellant.

As a new type of progressive energy release propellant, nitro gradiently distributed propellant (NGDP) was prepared by a denitration reaction between a denitration reagent and the propellant to remove the energy-containing functional group (-O-NO2) from the surface of the propellant. The kinetics of the denitration reaction determines distribution of the nitrate group in the surface layer of NGDP, which further affects the combustion progressivity. In this paper, the kinetic model for the denitration reaction process of the cylindrical single-base gun propellant was studied by the shrinking unreacted core model (SUC model). The energy change of the propellant particles before and after the denitration reaction was used to evaluate the denitration rates, which were used to fit the proposed SUC cylindrical model. The results show that the rate-controlling step of the denitration reaction process is largely dependent on the concentration of the denitration reagent. At low concentrations (the concentration of the denitration reagent was 6%), the denitration reaction process was controlled by the chemical reaction, and the activation energy was found to be 48.40 kJ·mol-1. When the concentration increased (the concentration of the denitration reagent was 15%), the rate-controlling step changed to a solid product layer diffusion control with an activation energy of 84.77 kJ·mol-1. The kinetic models obtained in this study can provide theoretical guidance for the controlled preparation of NGDP with good combustion progressivity.

One-Step Fabrication of Recyclable Konjac Glucomannan-Based Magnetic Nanoparticles for Highly Efficient Cr(VI) Adsorption.

Recently, the natural polymer polysaccharide konjac glucomannan (KGM) has received attention as a promising adsorbent in water treatment due to its low toxicity, cost-effectiveness and biocompatibility. However, the high-level water absorbency of KGM makes it difficult to recover in water treatment. In this study, by combining KGM with magnetic nanoparticles, KGM-based magnetic nanoparticles (KGM-Fe3O4 NPs) with excellent adsorption properties and recyclability for heavy metals were prepared using an one-step precipitation method. The as-prepared KGM-Fe3O4 NPs have a spherical morphology of superparamagnetism with a small particle size (ca. 7.0 nm) and a large specific surface area (160.1 m2·g-1). Taking Cr(VI) as the target heavy metal ion, the above nanoparticles have a high adsorption capacity and fast adsorption rate for Cr(VI). The pseudo-second order kinetic model is more suitable to describe the adsorption process of Cr(VI) by KGM-Fe3O4 NPs, and the maximum adsorption capacity of Cr(VI) onto KGM-Fe3O4 NPs was calculated to be 41.67 mg·g-1 using the Langmuir isotherm model. In addition, KGM-Fe3O4 NPs with adsorbed heavy metal ions can be quickly recovered from a solution, regenerated, and reused in the next cycle. KGM-based Fe3O4 nanoparticles are promising adsorbents that show significant reusability for the removal of metal ions in water and wastewater treatment.

Highly efficient C(CO)-C(alkyl) bond cleavage in ketones to access esters over ultrathin N-doped carbon nanosheets.

Selective oxidative cleavage of the C(CO)-C bond in ketones to access esters is a highly attractive strategy for upgrading ketones. However, it remains a great challenge to realize this important transformation over heterogeneous metal-free catalysts. Herein, we designed a series of porous and ultrathin N-doped carbon nanosheets (denoted as CN-X, where X represents the pyrolysis temperature) as heterogeneous metal-free catalysts. It was observed that the fabricated CN-800 could efficiently catalyze the oxidative cleavage of the C(CO)-C bond in various ketones to generate the corresponding methyl esters at 130 °C without using any additional base. Detailed investigations revealed that the higher content and electron density of the graphitic-N species contributed to the excellent performance of CN-800. Besides, the high surface area, affording active sites that are more easily accessed, could also enhance the catalytic activity. Notably, the catalysts have great potential for practical applications because of some obvious advantages, such as low cost, neutral reaction conditions, heterogeneous nature, high efficiency, and broad ketone scope. To the best of our knowledge, this is the first work on efficient synthesis of methyl esters via oxidative esterification of ketones over heterogeneous metal-free catalysts.

Efficient synthesis of cyclic carbonates from CO2 under ambient conditions over Zn(betaine)2Br2: experimental and theoretical studies.

It is very interesting to synthesize high value-added chemicals from CO2 under mild conditions with low energy consumption. Here, we report that a novel catalyst, Zn(betaine)2Br2, can efficiently promote the cycloaddition of CO2 with epoxides to synthesize cyclic carbonates under ambient conditions (30 °C, 1 atm). DFT calculations provide important insights into the mechanism, particularly the unusual synergistic catalytic action of Zn2+, Br- and NR4+, which is the critical factor for the outstanding performance of Zn(betaine)2Br2. The unique features of the catalyst are that it is cheap, green and very easy to prepare.

Quasi-square-shaped cadmium hydroxide nanocatalysts for electrochemical CO2 reduction with high efficiency.

Powered by a renewable electricity source, electrochemical CO2 reduction reaction is a promising solution to facilitate the carbon balance. However, it is still a challenge to achieve a desired product with commercial current density and high efficiency. Herein we designed quasi-square-shaped cadmium hydroxide nanocatalysts for CO2 electroreduction to CO. It was discovered that the catalyst is very active and selective for the reaction. The current density could be as high as 200 mA cm-2 with a nearly 100% selectivity in a commonly used H-type cell using the ionic liquid-based electrolyte. In addition, the faradaic efficiency of CO could reach 90% at a very low overpotential of 100 mV. Density functional theory studies and control experiments reveal that the outstanding performance of the catalyst was attributed to its unique structure. It not only provides low Cd-O coordination, but also exposes high activity (002) facet, which requires lower energy for the formation of CO. Besides, the high concentration of CO can be achieved from the low concentration CO2 via an adsorption-electrolysis device.

Highly Efficient Oxidative Cyanation of Aldehydes to Nitriles over Se,S,N-tri-Doped Hierarchically Porous Carbon Nanosheets.

Oxidative cyanation of aldehydes provides a promising strategy for the cyanide-free synthesis of organic nitriles. Design of robust and cost-effective catalysts is the key for this route. Herein, we designed a series of Se,S,N-tri-doped carbon nanosheets with a hierarchical porous structure (denoted as Se,S,N-CNs-x, x represents the pyrolysis temperature). It was found that the obtained Se,S,N-CNs-1000 was very selective and efficient for oxidative cyanation of various aldehydes including those containing other oxidizable groups into the corresponding nitriles using ammonia as the nitrogen resource below 100 °C. Detailed investigations revealed that the excellent performance of Se,S,N-CNs-1000 originated mainly from the graphitic-N species with lower electron density and synergistic effect between the Se, S, N, and C in the catalyst. Besides, the hierarchically porous structure could also promote the reaction. Notably, the unique feature of this metal-free catalyst is that it tolerated other oxidizable groups, and showed no activity on further reaction of the products, thereby resulting in high selectivity. As far as we know, this is the first work for the synthesis of nitriles via oxidative cyanation of aldehydes over heterogeneous metal-free catalysts.

Fabrication of Superamphiphilic Carbon Using Lignosulfonate for Enhancing Selective Hydrogenation Reactions in Pickering Emulsions.

Superamphiphilic materials have great potential to enhance the mass transfer between phases in liquid-liquid catalysis due to their special affinities. Constructing superamphiphilic surfaces that possess superhydrophilic and superhydrophobic properties simultaneously has been a tough assignment. So, exploration of simple methods to prepare such materials using renewable and abundant feedstocks is highly desired. Here, we reported an effective strategy to construct superamphiphilic carbon directly from sodium lignosulfonate, which is a renewable resource from paper industry wastes. From the characterization of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) for superamphiphilic carbon, we found that element C was responsible for the hydrophobic nature and the existence of O and S endowed the carbon with hydrophilic characteristics. Further, micro/nanohierarchical pores were found beneficial for the superamphiphilicity of carbon. Meantime, in the selective hydrogenation of styrene, phenylacetylene, and cis-stilbene in liquid-liquid systems, conversion became double using superamphiphilic carbon compared with blank results, and the yields were three times more than those in blank experiments. The reasons were that superamphiphilic carbon induced the formation of Pickering emulsions and enriched the reactants around catalysts, as concluded by the characterization of confocal laser scanning microscopy and relating contrastive experiments. This work revealed a different route to obtain superamphiphilic carbon and provided a diverse perspective to promote Pickering emulsion catalysis by the superamphiphilicity of carbon.

Production of Piperidine and δ-Lactam Chemicals from Biomass-Derived Triacetic Acid Lactone.

Piperidine and δ-Lactam chemicals have wide application, which are currently produced from fossil resource in industry. Production of this kind of chemicals from lignocellulosic biomass is of great importance, but is challenging and the reported routes give low yield. Herein, we demonstrate the strategy to synthesize 2-methyl piperidine (MP) and 6-methylpiperidin-2-one (MPO) from biomass-derived triacetic acid lactone (TAL) that is produced microbially from glucose. In this route, TAL was firstly converted into 4-hydroxy-6-methylpyridin-2(1H)-one (HMPO) through facile aminolysis, subsequently HMPO was selectively transformed into MP or MPO over Ru catalysts supported on beta zeolite (Ru/BEA-X, X is the molar ratio of Si to Al) via the tandem reaction. It was found that the yield of MP could reach 76.5 % over Ru/BEA-60 in t-BuOH, and the yield of MPO could be 78.5 % in dioxane. Systematic studies reveal that the excellent catalytic performance of Ru/BEA-60 was closely correlated with the cooperative effects between active metal and acidic zeolite with large pore geometries. The related reaction pathway was studied on the basis of control experiments.

Highly efficient removal of Cr(VI) from water based on graphene oxide incorporated flower-like MoS2 nanocomposite prepared in situ hydrothermal synthesis.

An efficient adsorbent for the treatment of Cr(VI) was simply fabricated by combining graphene oxide with MoS2 nanosheets via in situ hydrothermal process with CTAB as the surfactant. The experimental results indicated that the agglomeration of the MoS2 nanosheets are reduced and uniformly grown on the graphene sheet during the in situ hydrothermal process, and the introduction of graphene oxide provided higher specific surface area and abundant oxygenic groups. Based on this, the removal efficiency of Cr(VI) onto MoS2/rGO was 75.9% at pH 2.0, which was higher than that of bulk MoS2 (61.0%). On account of Sips adsorption isotherm model, the highest uptake capacity of MoS2/rGO toward Cr(VI) reached 80.8 mg g-1. The adsorption kinetic consequences showed that the chemisorption process was the control step, and the removal mechanism for Cr(VI) is redox and adsorption; in this way, the adsorbed Cr(VI) was partially reduced to Cr(III). Furthermore, this as-prepared adsorbent also presented satisfying reusability for removal of Cr(VI) and can be used for the selective removal of Cr(VI) in the presence of NO3-. In short, it may provide a potential route to enhance the adsorption property of MoS2 toward heavy metals through incorporating with GO, which would expand the applications of MoS2 in the field of treatment of the heavy metal wastewater.

Highly efficient removal of heavy metal ions by carboxymethyl cellulose-immobilized Fe3O4 nanoparticles prepared via high-gravity technology.

The aim of this study is to explore facile and large-scale method for the preparation of magnetic adsorbent materials with high-efficient heavy metal removal performance. Here, based on the process intensification of high-gravity technology, the carboxymethyl cellulose-immobilized Fe3O4 nanoparticles (CMC-Fe3O4) were continuously synthesized via impinging stream-rotating packed bed. With a theoretical production rate of 2.35 kg h-1, the as-prepared CMC-Fe3O4 exhibited better adsorption capacity and faster rate for Pb(II) than those of pure Fe3O4, and the maximum adsorption capacity of Pb(II) reached up to 152.0 mg g-1. It was found that the adsorption data of Pb(II) onto CMC-Fe3O4 fit well to pseudo-second order kinetic model and Langmuir isotherm model. Moreover, the as-prepared adsorbent exhibited good reusability after five adsorption-desorption cycles. Overall, the high-gravity technology can be employed for the preparation of high-performance nano-adsorbent and has a great potential in the application of heavy metal removal.

Removal of heavy metal ions by magnetic chitosan nanoparticles prepared continuously via high-gravity reactive precipitation method.

This study aimed to provide a continuous method for the preparation of magnetic Fe3O4/Chitosan nanoparticles (Fe3O4/CS NPs) that can be applied to efficient removal of heavy metal ions from aqueous solution. Using a novel impinging stream-rotating packed bed, the continuous preparation of Fe3O4/CS NPs reached a theoretical production rate of 3.43kg/h. The as-prepared Fe3O4/CS NPs were quasi-spherical with average diameter of about 18nm and saturation magnetization of 33.5emu/g. Owing to the strong metal chelating ability of chitosan, the Fe3O4/CS NPs exhibited better adsorption capacity and faster adsorption rates for Pb(II) and Cd(II) than those of pure Fe3O4. The maximum adsorption capacities of Fe3O4/CS NPs for Pb(II) and Cd(II) were 79.24 and 36.42mgg-1, respectively. In addition, the Fe3O4/CS NPs shown excellent reusability after five adsorption-desorption cycles. All the above results provided a potential method for continuously preparing recyclable adsorbent with a wide prospect of application in wastewater treatment.

Ionic liquid [OMIm][OAc] directly inducing oxidation cleavage of the ß-O-4 bond of lignin model compounds.

We explored the oxidation reactions of lignin model compounds directly induced by ionic liquids under metal-free conditions. In this work, it was found that ionic liquid 1-octyl-3-methylimidazolium acetate as a solvent could promote the aerobic oxidation of lignin model compound 2-phenoxyacetophenone (1) and the yields of phenol and benzoic acid from 1 could be as high as 96% and 86%, respectively. A possible reaction pathway was proposed based on a series of control experiments. An acetate anion from the ionic liquid attacked the hydrogen from the ß-carbon thereby inducing the cleavage of the C-O bond of the aromatic ether. Furthermore, it was found that 2-(2-methoxyphenoxy)-1-phenylethanone (4) with a methoxyl group could also be transformed into aromatic products in this simple reaction system and the yields of phenol and benzoic acid from 4 could be as high as 98% and 85%, respectively. This work provides a simple way for efficient transformation of lignin model compounds.

Electrochemical Sensing toward Trace As(III) Based on Mesoporous MnFe2O4/Au Hybrid Nanospheres Modified Glass Carbon Electrode.

Au nanoparticles decorated mesoporous MnFe2O4 nanocrystal clusters (MnFe2O4/Au hybrid nanospheres) were used for the electrochemical sensing of As(III) by square wave anodic stripping voltammetry (SWASV). Modified on a cheap glass carbon electrode, these MnFe2O4/Au hybrid nanospheres show favorable sensitivity (0.315 µA/ppb) and limit of detection (LOD) (3.37 ppb) toward As(III) under the optimized conditions in 0.1 M NaAc-HAc (pH 5.0) by depositing for 150 s at the deposition potential of -0.9 V. No obvious interference from Cd(II) and Hg(II) was recognized during the detection of As(III). Additionally, the developed electrode displayed good reproducibility, stability, and repeatability, and offered potential practical applicability for electrochemical detection of As(III) in real water samples. The present work provides a potential method for the design of new and cheap sensors in the application of electrochemical determination toward trace As(III) and other toxic metal ions.

Free radical reaction promoted by ionic liquid: a route for metal-free oxidation depolymerization of lignin model compound and lignin.

Ionic liquid 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BnMIm][NTf2]) can promote the generation of the ˙OOH free radical and thereby efficiently transformed the ß-O-4 lignin model compound 2-phenoxyacetophenone into benzoic acid and phenol using O2 as the oxidant. Furthermore, the IL-based metal-free catalytic system can also depolymerize other lignin model compounds and organosolv lignin effectively.

Acceleration of disproportionation of aromatic alcohols through self-emulsification of reactants in water.

Exploration of new and effective routes to conduct organic reactions in water using the special properties of water/organics is of great importance. In this work, we performed the disproportionation of various aromatic alcohols in water and in different organic solvents. It was demonstrated that the disproportionation reactions of the alcohols were accelerated more effectively in water than organic-solvent-based or solvent-free reactions. A series of control experiments were conducted to study the mechanism of the accelerated reaction rate in water. It was shown that the reactants could emulsify the reactant/water systems at the reaction conditions owing to their amphiphilic nature. The regularly orientated reactant molecules at the water/reactant droplet interface improved the contact probability of the reactive groups and the Pd nanocatalysts, which is one of the main reasons for the enhanced reaction rate in water. Controlling the self-emulsification of amphiphilic reactant/water systems has great application potential for optimizing the rate and/or selectivity of many organic reactions.

Pd(II) immobilized on mesoporous silica by N-heterocyclic carbene ionic liquids and catalysis for hydrogenation.

In this work we synthesized Pd(II) immobilized on mesoporous silica by N-heterocyclic carbene (NHC) ionic liquids (ILs) with different alkyl chain lengths. The catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), low-angle X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen sorption. The catalysts were used for the hydrogenation of alkenes and allyl alcohol. The results indicated that the catalysts were very active, selective, and stable. The selectivity for the hydrogenation of allyl alcohol to 1-propanol increased with the increase of the alkyl chain length of the ILs. The effect of supercritical CO(2) (scCO(2)) on the hydrogenation of allyl alcohol was also studied, and it was demonstrated that scCO(2) could enhance the selectivity of the reaction considerably. The XPS study showed that the valence of Pd(II) remained unchanged under hydrogenation conditions.

Shape controlled synthesis of palladium nanocrystals by combination of oleylamine and alkylammonium alkylcarbamate and their catalytic activity.

The shape of Pd nanocrystals (NCs) can be controlled by combination of oleylamine (OAm) and alkylammonium alkylcarbamate (AAAC), and Pd spheres, tetrahedra and multipods have been synthesized. The multipods and tetrahedra are much more active than the spheres for hydrogenation reactions.

Synthesis of dimethylformamide from CO2, H2 and dimethylamine over Cu/ZnO.

Cheap and simple Cu/ZnO catalysts are very effective and recyclable for the synthesis of dimethylformamide (DMF) from CO(2), H(2), and dimethylamine, and a yield of 97% can be reached.