Search

Supported gold (Au) catalysts appear attractive for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol, a promising method for eliminating 4-NP pollutant in water media. Selecting an appropriate support is a crucial step for obtaining supported Au catalysts with excellent activity. Herein, we demonstrate for the first time that cyanuric acid-based material (CAM) is an appropriate support material, where Au/CAM catalysts catalyze the 4-NP reduction in water at room temperature. The reaction time for complete conversion of 4-NP can be reduced by ~ 10 times to even two orders of magnitude compared to some other reported supported Au catalysts and depending on the reaction conditions used. Moreover, CAM can be obtained using an extremely simple and green synthesis method. [ABSTRACT FROM AUTHOR]

Oil shale (OS) is a particularly promising alternative fossil fuel source. However, very different from coal, its inorganic mineral content is very high. The organic matters (mainly kerogen) are finely distributed in the inorganic minerals. Therefore, the minerals may affect the processing of OS, whose elucidation is critical to the choice of processing conditions. In this work, different minerals (SiO2, CaCO3, and Al2O3) were added to OS with different mass ratios of OS to mineral, respectively. Then, the thermogravimetric (TG) technique was employed to analyze the reaction behavior of these different OS/mineral mixtures in N2and in air for studying the influence of minerals on the OS pyrolysis in N2(i.e., retorting) and on the OS combustion in air. The results show that CaCO3and Al2O3have a promoting effect on both pyrolysis and combustion of OS, and they can decrease the reaction activation energy of both kinds of processes. However, SiO2has an inhibitive effect and can increase the reaction activation energy for both kinds of processes. It is hoped that the present study can further increase the understanding toward the effect of different minerals on the OS reactions. [ABSTRACT FROM PUBLISHER]

Oil shale (OS), from which petroleum-like shale oil can be obtained via retorting, is one of the most promising alternative fossil fuels due to its huge reserve. A main obstacle to OS retorting is the required high-energy input, particularly for underground retorting. Recently a low-energy-input route via self-heating retorting (SHR) was developed (Guo et al., 2013 and 2014). However, its unclear reaction mechanism hinders its further development. Herein, the reaction mechanism of SHR was analyzed by using Huadian OS and thermal analysis techniques. The results suggest anaerobic retorting (AR) used for preparing shale oil produces substantial residual carbon (RC) byproduct, and the heat contained in RC is more than the energy input needed by an AR process. While in SHR process, by reaction-kinetics control, part of kerogen is first pyrolized into oil and RC before exposed to air, and then RC in-situ reacts with the diffused air to release heat for progressing SHR and replacing external heat supply. In-situ utilizing RC by SHR process partly explains why SHR itself provides heat to increase retorting temperature but without obviously lost shale-oil yield. [ABSTRACT FROM AUTHOR]

Recently a facile low-energy-input retorting route but without marked loss in the shale-oil yield is developed, which is achieved by a self-heating effect, that is, spontaneously increasing retorting temperature in the absence of external heat provision (Guo et al., 2013, 2014). In this work, the applicability of self-heating retorting (SHR) process to three Chinese oil shales from different places (i.e., Longkou, Huadian and Fushun) is studied. Of these three oil shales, Fushun oil shale is associated with coal and was previously abandoned during coal mining due to its not high kerogen or oil content. The results show that it’s hard for Fushun oil shale to obtain satisfying self-heating effect, while Longkou or Huadian oil shale with higher kerogen or oil content shows satisfactory SHR. However, by adding suitable amounts of Longkou or Huadian oil shale into Fushun oil shale, a satisfying self-heating effect can be obtained as well. Thus, the relatively low-grade Fushun oil shale can also be well utilized to produce shale oil via this facile SHR route. Moreover, to utilize Fushun oil shale with a greener SHR process, the process can be performed by co-retorting Fushun oil shale with pine needles, a kind of renewable biomass. This finding also provides a new starting point for exploring plentiful biomass resources to utilize low-grade oil shale to produce oil in the future work. [ABSTRACT FROM AUTHOR]

Caustic calcined magnesia (main component is MgO) can be used to produce Mg(OH) 2 by ammonium-circulation method (reaction steps: (1) MgO + 2NH 4 + → Δ Mg 2 + + 2NH 3 ↑ + H 2 O and (2) Mg 2 + + 2NH 3 ↑ + 2H 2 O → Mg(OH) 2 ↓ + 2NH 4 + ; Overall: MgO + H 2 O → Mg(OH) 2 ↓). NH 4 Cl, NH 4 NO 3 and (NH 4 ) 2 SO 4 have exhibited the ability to be used as a circulation medium. In this work, ammonium acetate (NH 4 Ac) was investigated as a circulation medium. The purity of the used caustic calcined magnesia (i.e., MgO content) is 85 wt.%. The results show that NH 4 Ac is a much more efficient circulation medium than NH 4 Cl, NH 4 NO 3 or (NH 4 ) 2 SO 4 is. Step (1) in the ammonium-circulation method can be significantly accelerated if NH 4 Ac is used as the circulation medium. The reason for the high efficiency of NH 4 Ac was also analyzed. By using NH 4 Ac as the circulation medium, rose petal-like Mg(OH) 2 precipitate can be prepared in the presence of polyethylene glycol. The purity of the prepared Mg(OH) 2 is more than 99 wt.%. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the minerals of Huadian oil shale on a low-energy input retorting route was studied. This special retorting route was achieved by a self-heating effect, that is, spontaneously increasing retorting temperature in the absence of external heat provision (Guo et al., 2013) [12]. Oil shale was first demineralized with HCl, HNO3 or HF before used in the self-heating retorting. The oil shales treated with different acids, and their corresponding semicokes attained after retorting were also characterized. The results showed that using HF-treated oil shale produces the best self-heating effect and the highest oil yield. Using HNO3-treated oil shale also promotes the self-heating effect. While using HCl-treated oil shale remarkably worsens the self-heating effect, but it gives a higher oil yield than using HNO3-treated or raw oil shale. The reasons are also analyzed. Although different acid treatments affect the self-heating effect differently, all the attained oils mainly consist of various hydrocarbons, however, the product distributions are different. [Copyright &y& Elsevier]

A processusing plentiful and inexpensive caustic calcined magnesia(CCM; main component is MgO) to prepare lamellar MH of high purityis described. The process begins with the reaction of MgO in CCM withNH4NO3at ∼100 °C to produce ammoniagas and Mg(NO3)2solution and the subsequentfiltration of Mg(NO3)2solution to remove impurities(e.g., SiO2). Then, the obtained ammonia is introducedinto the Mg(NO3)2solution to produce MH precipitateand NH4NO3. After the MH precipitate is separatedby filtration, the filtrate containing NH4NO3is returned to the initial step. The overall reaction of this processis the hydration of MgO to MH. Therefore, this process is called theapparent-hydration method. This apparent-hydration method overcomesthe disadvantages of the true hydration method, such as the inabilityto remove impurities. A crucial finding is that, because of the presenceof trace SO42–in the obtained Mg(NO3)2solution, a MH product with a narrow particlesize distribution cannot be produced. After removal of the SO42–with Ba(NO3)2,lamellar MH with a narrow particle size distribution can be synthesizedat 120 °C in one step. This work provides a promising route tothe use of CCM to prepare MH. [ABSTRACT FROM AUTHOR]

Abstract: Au, Pd and Au-Pd alloy are deposited on porous steel fiber matrices via sputtering technique. By this technique the preparation of the heterogeneous catalysts is clean, simple and fast as noble metal complexes, solvents or reducing agents are not needed. The studied Au-Pd catalyst exhibits good activity in the aerobic oxidation of benzyl alcohol and benzyl amines. Especially in the oxidation of benzyl amines, the Au-Pd catalyst shows a great synergistic enhancement in the activity. [Copyright &y& Elsevier]

Abstract: Through-porous steel fiber matrix with high specific surface area and self-support strength was examined as the support of TiO2 film photocatalyst. TiO2 was uniformly and conformally deposited onto the surface of the metal skeleton of the porous steel fiber matrix via atomic layer deposition method so that the porosity as well as gas permeability of the matrix is maintained. For further improving the photocatalytic activity, noble metals (Au and Pt/Pd alloy) were sputtered onto the surface of TiO2 photocatalyst. The photodegradation of methyl orange was used for evaluating the photocatalytic properties. The results show that compared with TiO2 films deposited on flat Si wafers, TiO2 films on the porous support display higher photocatalytic activities, owing to their higher specific surface areas. The photocatalytic activity of TiO2 on porous support was not enhanced by Au, while it was remarkably improved by Pt/Pd. The TiO2 photocatalysts were also analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. [Copyright &y& Elsevier]

Multi-walled carbon nanotube (MWCNT)/polythiophene (PTh) composites have been prepared by in situ chemical oxidative polymerization. PTh is synthesized onto the sidewalls of the MWCNTs, which play a role as hard templates for PTh to produce one-dimensional nanostructures. The morphology and structures of the MWCNT/PTh composites are characterized by High-resolution transmission electron microscopy, x-ray diffraction, and Fourier transform infrared spectrometry. Their electrical property and thermal stability are determined using vector network analyzer and thermal gravimetric analyzer. Moreover, the mechanism of MWCNT/PTh nanowire formation is described. The studies show that the composites are nanowires with core-shell structure, in which the outer shells and inner cores are formed by PTh and MWCNTs, respectively. The addition of MWCNTs does not change the backbone structure of PTh and affect the amorphous condition of PTh very slightly, however, it improves the electrical conductivity and thermal stability of PTh. [ABSTRACT FROM AUTHOR]

Abstract: Polyaniline(PANi)/Fe3O4 nanocomposites have been prepared via in situ chemical oxidative polymerization directed with cationic surfactant cetyltrimethylammonium bromide (CTAB). The studies show that PANi can coat Fe3O4 nanoparticles. CTAB can produce insoluble substance with initiator of polyreaction, and plays a very important role for the coating of Fe3O4 nanoparticles by PANi. Many Fe3O4 nanoparticles are bald without being coated by PANi when CTAB is replaced by anionic surfactant, so anionic surfactant can not play the role of CTAB. [Copyright &y& Elsevier]

Abstract: A water/oil microemulsion system having been successfully used for synthesizing polyaniline(PANi) nanoparticles, was employed for preparing PANi/multi-walled carbon nanotube (MWCNT) nanocomposites via in situ chemical oxidative polymerization. The structures and the electrical property of PANi/MWCNT nanocomposites were also studied. The studies showed that PANi could coat MWCNTs to form nanocables with core–shell structure, and the backbone structure of PANi was not damaged by the introduction of MWCNTs. The conductivities of PANi/MWCNT nanocomposites were higher than that of PANi. Moreover, a model was supposed to be used for describing a PANi/MWCNT nanocable formation by in situ microemulsion polymerization. [Copyright &y& Elsevier]

Three ionic liquids (ILs) with acetate anion (1-hexyl-3-methylimidazolium acetate, [HMIM][OAC]; 1-octyl-3-methylimidazolium acetate, [OMIM][OAC]; and 1-decyl-3-methylimidazolium acetate, [DMIM][OAC]) were studied as entrainers for separating the benzene-methanol binary azeotrope. Isobaric vapor-liquid equilibrium (VLE) data for the ternary systems of benzene + methanol + IL were measured at 101.3 kPa. The VLE data were well correlated by using the nonrandom two-liquid (NRTL) model. The relative volatility of benzene to methanol is enhanced with the increase in IL content. The azeotropic phenomenon of benzene-methanol mixture can be completely eliminated when IL content reaches a specific value. After the azeotropy of benzene-methanol mixture is completely eliminated, the separation ability of the three ILs follows the order [HMIM][OAC] > [OMIM][OAC] > [DMIM][OAC]. The separation abilities of the three ILs were further analyzed with the help of their σ-profiles. [ABSTRACT FROM AUTHOR]

The chemical formula of basic zinc chloride is Zn5(OH)8Cl2 · H2O (denoted as ZHC). It is a new type of zinc source additive, widely used in the feed industry. In this article, micron‐sized hexagonal flake ZHC with a diameter of 10–60 µm is directly prepared by ammonia precipitation method using ZnCl2 as raw material. The products are characterized and analyzed by X‐ray diffraction, scanning electron microscopy, and laser particle size analyzer. The effects of reaction temperature, ammonia flow rate, aging time, and reactant concentration on the product morphology are studied. Under the optimum reaction conditions, the ZnCl2 concentration is 2.0 mol L−1, NH3 flow rate is 300 mL min−1, the reaction time is 1 h, the reaction temperature is 80 °C, and the aging time is 5 h. Lastly, the yield reaches 49.06%. The growth habit of ZHC is theoretically analyzed by the Morphology program. The calculation results are in good agreement with the experimental results. The change of (003) crystal plane exposure caused by temperature is an important reason for the non‐ideality of macroscopic morphology. [ABSTRACT FROM AUTHOR]

As shown herein, selectivity of aerobic oxidation of benzyl alcohol with gold nanoparticles dispersed on Al 2 O 3 support is solvent-controlled. Using different solvents, the reaction was directed toward a variety of products: benzaldehyde, benzoic acid or benzoic esters were selectively produced from benzyl alcohol depending on the conditions. In toluene, benzaldehyde was produced with high selectivity, while quantitative conversion to benzoic acid was achieved in alkaline water. In methanol, methyl benzoate was produced with very high yield. Moreover, activity of the catalyst was dramatically improved without loss of selectivity in biphasic media; with a toluene/alkaline water system the highest TOF for benzoic acid synthesis was close to 5200 h −1 , selectivity being 98%. [ABSTRACT FROM AUTHOR]

Three acetate-based ionic liquids (ILs) (tetraethylammonium acetate, [N 2,2,2,2 ][AC]; 1‑butyl‑2,3-dimethylimidazolium acetate, [BMMIM][AC]; or tributyl-methylammonium acetate, [N 4,4,4,1 ][AC]) were used to separate the 2-butanone-ethanol azeotropic mixture as entrainer. The separation abilities of the three ILs were compared by measuring isobaric vapor-liquid equilibrium (VLE) data of the 2-butanone + ethanol + IL ternary systems at 101.3 kPa. The VLE data were well correlated through the use of the nonrandom two-liquid (NRTL) model. The azeotrope of 2-butanone + ethanol binary system is entirely eliminated when the concentration of IL achieves a certain value. The minimum mole fractions of the three ILs to completely eliminate azeotropic phenomena are 0.0146, 0.0166 and 0.0240, respectively. The breaking azeotropic capacities of the three ILs are better than that previously reported in the literatures. According to the average relative volatility, after the azeotropic point is thoroughly eliminated, the order of the separation capability of the three ILs is as below: [N 2,2,2,2 ][AC] > [BMMIM][AC] > [N 4,4,4,1 ][AC]. The σ-profiles were used to further explore the separation mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Co-filled carbon nanotubes composites were synthesized via using a simple and efficient wet chemistry solution method. The samples were characterized by transmission electron microscopy. Microwave-absorbing properties were investigated by measuring complex permittivity and complex permeability of the absorber in a frequency range of 2–18GHz. The reflection loss (R.L.), matching frequency (f m) and matching thickness (d m) were calculated using the theory of the absorbing wall. The electromagnetic properties and microwave-absorbing characteristics effects of the modified carbon nanotubes by the encapsulation of metal Co were investigated. A matching thickness is found corresponding to a matching frequency. The maximum reflection loss is about −39.32dB and the bandwidth corresponding to the reflection loss below −10dB is 3.47GHz. With increasing thickness, the maximum reflection loss shifts to lower frequency. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes encapsulated Fe nanowire composites were synthesized via pyrolyzing of ferrocene. The reflection loss (R.L.), matching frequency (f m) and matching thickness (d m) were calculated using the theory of the absorbing wall. The electromagnetic properties and microwave-absorbing characteristic effects by the encapsulation of metal Fe were investigated in a frequency range of 8–18 GHz. With matching thickness of 3.5 mm, the maximum reflection loss is about −22.73 dB for the absorber. The bandwidth corresponding to the reflection loss below −10 dB is more than 4.22 GHz. With increasing thickness, the peak value of the reflection loss shifts to a lower frequency. [Copyright &y& Elsevier]

Abstract: Fe-filled carbon nanotubes were prepared reliably and economically via pyrolyzing of ferrocene and activated carbon. The sample was characterized by high-resolution transmission electron microscopy, electron diffraction and fast Fourier transforms. The complex relative permittivity and permeability parameters were measured in a frequency range of 2–18GHz and microwave absorbing behavior was investigated. The sample exhibits the maximum reflection loss and the widest bandwidth of below −5dB is −11.29dB and 4.13GHz (matching thickness=2.5mm), respectively. [Copyright &y& Elsevier]

Polymorphism- or morphology-controllable synthesis of CaCO 3 is of significance. Usually only calcite CaCO 3 can be obtained from the ordinary CO 2 -Ca(OH) 2 solution route; the very low solubility of Ca(OH) 2 also causes many defects with this route. The route by CaCl 2 and Na 2 CO 3 exhibits some advantages, but the consumption of Na 2 CO 3 is a deficiency. Therefore, this work studies the precipitation of CaCO 3 with CaCl 2 in NH 3 -CO 2 aqueous solution, which will make the overall reaction “CaCO 3   →   CaCO 3 ” if tracing the origin of the reactants. A main focus of the present work is to elucidate how to obtain various CaCO 3 polymorphs with different morphologies through this synthesis system and the corresponding crystal growth mechanism. The results show that, just by simply regulating the reaction conditions, all three anhydrous CaCO 3 polymorphs with various morphologies (e.g., cubic, lamellar, spherical, needle-like and branched) can be obtained in the absence of any additives. The crystal growth process can be well explained based on either Ostwald ripening or dissolution-recrystallization mechanism, depending on the reaction conditions. In addition, the rare phase transition of metastable vaterite to metastable aragonite can also be obtained from the present synthesis system, besides the usual phase transition of vaterite to the most thermodynamically stable calcite. This work provides the essential theoretical support for further developing a green process for CaCO 3 production by using various calcium-containing carbonate minerals, such as limestone, calcite and dolomite. [ABSTRACT FROM AUTHOR]

Rational structure design of anode materials plays crucial roles in the continuous improvement of electrochemical lithium storage performance for high performance lithium-ion batteries (LIBs). In this study, a novel hierarchical straw-sheaf-like Co 3 O 4 (Co 3 O 4 -SSL) composed of numerous strongly tied nanoneedles was successfully synthesized with hydrothermal route by a charge-driven self-assembly strategy. Material characterizations indicated that typical length of nanoneedles was about 10 µm and the average diameter was about 80 nm. Mechanism studies implied that positively charged diallyldimethylammonium chloride (DDA) molecules played a key role in the formation of straw-sheaf-like structures. Impressively, when Co 3 O 4 -SSL was investigated as anode materials for electrochemical lithium storage, high specific capacity (e.g. 842.9 mAh g −1 after 300 cycles tested at 500 mA g −1 ), superior cycling stability (e.g. capacity retention of about 100% over 300 cycles) and excellent rate capability (e.g. 707 mAh g −1 tested at 3000 mA g −1 ) were achieved in the repeated charging-discharging cycles, demonstrating great potentials in energy storage materials. The proposed synthetic strategy is appealing in electrode structure design for next generation LIBs. [ABSTRACT FROM AUTHOR]

Use oxide-supported catalyst in green solvent, hot water : Au is anchored on oxide via Au┄O-M interaction (M = Fe, Ti, etc). Basic aqueous catalytic system may destruct a part of O M bonds into oxygen vacancies and weaken Au/support interaction, causing leaching and aggregation of Au. Three simple methods synergistically improve reusability of catalyst. [Display omitted] • Three facile ways synergistically improve catalyst reusability in green solvent, water. • They raise support stability and Au/support interaction to reduce leaching and aggregation of Au. • Nano supports interact with Au more strongly, and are more stable in hot basic water. • Nano TiO 2 is more stable due to the stronger surface Ti O bond, in line with BOLS theory. Obtaining reusable catalysts and using water as a green solvent still remain huge challenges. Various oxides are frequently used as the support, however, the aqueous catalytic systems, particularly in hot basic water, may decrease their stability and thus cause leaching or aggregation of the supported metal nanoparticles (NPs). In this work, three very simple methods in catalyst preparation are demonstrated to greatly improve the reusability of oxide-supported catalysts in 100 °C basic water, by systematically studying a series of oxides as well as carbons as support of gold (Au) NPs and employing Suzuki-Miyaura cross-coupling (SMCC) reaction as a probe. These methods are prerequisites for obtaining both excellent activity and recyclability. Absence of any of them will badly improve leaching or aggregation of Au NPs. The reasons for the synergistically improved reusability are also elucidated in details. Though it's extremely hard to thoroughly overcome leaching in hot water, this work achieves the application of Au/oxide to SMCC reaction in water with higher utilization efficiency of Au than some reported work in organic solvent or with other supports. The present work can serve as supplementary strategies to assist in designing high-performance oxide-supported catalysts for varieties of similar aqueous systems. [ABSTRACT FROM AUTHOR]

• Isobaric VLE data of ternary for cyclohexane-ethanol containing IL ([N 1,8,8,8 [Ac], [DMIM][AC] or [C16MIM]) were determined at 101.3kPa. • Temperature dependence of some thermophysical properties (heat capacity, viscosity and density) of the three ILs were determined at 101.3kPa and 333.15-363.15 K. • The measured data were well correlated. Some important topics and issues related to possible extractive distillation separation of cyclohexane + ethanol system using ionic liquids (ILs) are presented in this manuscript. Three ILs with acetate anion (methyl-trioctyl-ammonium acetate [N 1,8,8,8 [Ac], 1-decyl-3-methyl-imidazolium acetate [DMIM][Ac] and 1-hexadecyl-3-methyl-imidazolium acetate [C 16 MIM][Ac]) were selected as entrainers. The vapor–liquid phase equilibrium (VLE) data for cyclohexane + ethanol + ILs system were determined at 101.3 kPa and correlated by Wilson and NRTL models. The separation effect of these ILs on the basis of the NRTL model follows this order: [N 1,8,8,8 [Ac] > [DMIM][Ac] > [C 16 MIM][Ac]. The binary VLE data of the cyclohexane-ethanol mixture obtained by this device were compared with previously published data and tested by the Herington thermodynamic consistency test. Temperature dependence of some thermophysical properties (density, viscosity and heat capacity) of these ILs were obtained and correlated within the range of possible distillation operating temperatures. [ABSTRACT FROM AUTHOR]