Search

Determining the effect of crystal facets on reaction performance is essential for designing an efficient propane oxidation catalyst. Herein, α-MnO2 nanowires with exposed (110), (211), (310) and (200) facets were proposed, and their crystal facet-dependent reactivity to propane oxidation was investigated. The resultant α-MnO2 nanowires with predominantly exposed (110) facets showed the maximum propane oxidation activity (T90 = 262.1 °C), oxidation rate, and turnover frequency (at 230 °C), and high stability during the oxidation of propane. In situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the oxidation to form carboxylates is the decisive step; therefore, the production of reactive oxygen species is very important. The results from density of states computations revealed that the lowest electron energy was present in the (110) facet, which helps in the generation of reactive oxygen species and the regulation of the surface valence of Mn. The characterization and calculation results indicated that the (110) facets are conducive to forming oxygen vacancies, which allowed the activation and adsorption of O2 and propane, resulting in significantly enhanced propane oxidation activity. Apart from offering new insights about the structure–activity relationship of α-MnO2 with different facets exposed for short-chain volatile oxidation reactions, this study proposes a technique that can be used for improving other manganese-based catalyst oxidation systems. [ABSTRACT FROM AUTHOR]

In this paper, an efficient method to fabricate Al-based metal organic framework (Al-MOF) MIL-96 crystals with controllable size and morphology, by mixing other forms of reactants to replace the coordination modulators or capping agents, is presented. The size and morphology of the MIL-96 crystals can be selectively varied by simply altering the ratio of dual reactants via their hydrolysis reaction. All the samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and nitrogen sorption. Then based on the BFDH theory, a mechanism for the impact of hydrolysis of reactants on the crystal size and morphology is presented and discussed. We also evaluated the performance of these MOFs as sorbents for capturing CO2, and they all show enhanced adsorption properties compared with the bulk material, displaying high adsorption capacities on CO2 at atmospheric pressure and ambient temperature. [ABSTRACT FROM AUTHOR]

NiMo catalysts were prepared using Waugh-type NiMo heteropolycompounds as active phase precursors and evaluated in hydrodesulfurization (HDS) of dibenzothiophene (DBT). These catalysts were compared with corresponding reference catalysts prepared from the conventional precursors (ammonium heptamolybdate and nickel nitrate). Prepared catalysts were characterized by N physisorption, XRD, FT-IR, H-TPR, DRIFT of CO adsorption and HRTEM techniques. It was found that NiMo catalysts prepared from Waugh-type NiMo HPCs showed higher performance in HDS of DBT than their counterparts. Possible reasons of this result were discussed. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

ABSTRACT Self-emulsified water-borne epoxy curing agent of nonionic type was prepared using triethylene tetramine (TETA) and derivative of epoxy resin as a capping agent, which was synthesized by liquid epoxy resin (E51) and polyethylene glycol (PEG), and the curing agent possessed emulsification and curing properties at the same time. The curing agent with good property of emulsifying liquid epoxy resin could be obtained under the condition of the molar ratio of PEG : E51 : TETA as 0.8 : 1 : 3.5 at 80°C for 5 h. The mean particle size of the emulsion liquid was about 220 nm with the prepared curing agent and epoxy resin at the mass ratio of 1 : 3. The structure of the emulsion-type curing agent was confirmed by FTIR and 1H NMR spectra, and the mechanism of cured film formation was also analyzed by SEM photographs. The cured film prepared by the emulsion-type curing agent and epoxy resin under ambient cure conditions showed good properties even at high staving temperature. This study provides useful suggestions for the application of the water-borne epoxy resins in coating industry. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2652-2659, 2013 [ABSTRACT FROM AUTHOR]

Abstract: Hierarchically organized γ-AlOOH hollow spheres with nanoflake-like porous surface texture have been successfully synthesized via an ionic liquid-assisted hydrothermal synthesis method in citric acid monohydrate (CAMs). It was found that ionic liquid [bmim]+Cl− played an important role in the morphology of the product due to its strong interactions with reaction particles. The samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM). The results show that the product has narrow particle size distribution (500–900nm particle diameter range), high specific surface area (240.5m2/g) and large pore volume (0.61cm3/g). The corresponding γ-Al2O3 hollow spheres can be obtained by calcining it at 550°C for 3h. The proposed formation mechanism and other influencing factors of the γ-AlOOH hollow sphere material, such as reaction temperature, reaction duration, CAMs and urea, have also been investigated. [Copyright &y& Elsevier]

[Display omitted] • MnO 2 treated by urea-H 2 O 2 exhibits great photocatalytic propane oxidation activity. • H 2 O 2 treatment increase active sites to thermal catalytic performance. • The photocatalytic performance improvement is related to photogenerated electrons. • A new photothermal synergetic catalysis mechanism was proposed. Photothermal catalysis has an advantage in effective and economical elimination technology of volatile organic compounds (VOCs) in the ascendant. Herein, various surface defect engineering routes were adopted to enhance the low-temperature propane oxidation of δ-MnO 2. Compared to reducing etchants urea and vitamin C, δ-MnO 2 treated with urea - H 2 O 2 exhibited an excellent thermal (T 90 = 240 ℃) and photothermal (T 90 = 196 ℃) activities of propane oxidation. Urea - H 2 O 2 treatment provided high concentration of Mn4+ and surface-active oxygen (Mn4+-O sur) species as surface-active sites, and produced numerous oxygen vacancies to improve charge separation and superoxide species generation capacity. Thus, the photothermal conversion efficiency and low-temperature reducibility were remarkably enhanced. Furthermore, the photothermal synergistic catalytic mechanism was proposed based on in-situ diffuse reflectance infrared Fourier transform spectroscopy and control experiments. The strategy here offered insight into the rational design of efficient transition catalysts, and in-depth understanding of the photothermal catalytic VOCs removal mechanism. [ABSTRACT FROM AUTHOR]

Abstract: A simple and novel synthesis process, one-step ionic liquid-assisted hydrothermal synthesis route, has been developed in the work to synthesize Bohemithe (γ-AlOOH) with flower-like structure. The samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM). Ionic liquid [Omim]+Cl−, as a template, plays an important role in the morphology and pore structure of the products due to its strong interactions with reaction particles. With the increase in the dosage of ionic liquid [Omim]+Cl−, the morphology of the γ-AlOOH was changed from initial bundles of nanosheets (without ionic liquid) into final well-developed monodispersed 3D flower-like architectures ([Omim]+Cl−=72mmol). The pore structure was also altered gradually from initial disordered slit-like pore into final relatively ordered ink-bottle pore. Furthermore, the proposed formation mechanism and other influencing factors such as reaction temperature and urea on formation and morphology of the γ-AlOOH have also been investigated. [Copyright &y& Elsevier]

Abstract: Activated carbon supported iron catalysts derived from pine bark were prepared by different methods using a microwave reactor. The catalyst samples were characterized by physical adsorption of N2, Fourier Transform Infrared (FTIR) spectroscopy, and Transmission Electron Microscopy (TEM). The catalyst activity was evaluated for catalytic wet peroxide oxidation of phenol at 50°C. The results showed that the catalyst prepared by preloading the metal precursor to deashed biomass before carbonization and activation in a microwave reactor possessed much higher reactivity than catalyst prepared from other methods. The acid washing to remove ash from biomass eliminated the adverse effect of metals contained in the ash on catalyst, modified the biomass tissue which favored the catalyst dispersion on the biomass. The metal pre-loading to biomass led to a more uniform dispersion of catalyst on activated carbon. The microwave treatment saved energy, shortened preparation time. High catalytic activity for the catalytic wet peroxide oxidation of phenol was observed for catalyst samples prepared from pre-loading the active metal to pre-deashed bark samples. [Copyright &y& Elsevier]

Abstract: A new method for the preparation of presulfided eggshell MoS2/Al2O3 catalysts was developed and the catalysts thus prepared were comprehensively characterized and evaluated in terms of their performance in selective hydrodesulfurization (HDS) of FCC gasoline. Using this method, the eggshell thickness of the catalysts with sharp boundary could be easily regulated by controlling the spreading time and/or the temperature of the Mo precursor ([NH3CH2CH2NH3]2MoS4). The characterization by energy-dispersive spectrometry, X-ray diffraction, and high-resolution transmission electron microscopy indicated that the active phase structures, the particle sizes along the basal direction and the stacking degrees of MoS2 particles on eggshell MoS2/Al2O3 catalysts were similar to these on uniform MoS2/Al2O3 catalysts. Moreover, the results of temperature-programmed reduction and Fourier transformed infrared spectroscopy showed that the method used for the preparation of eggshell catalysts did not affect the nature or number of the MoS2 active sites compared to these of uniform catalysts. The evaluation of the eggshell catalysts performance, along with corresponding uniform catalysts, in selective HDS of FCC gasoline demonstrated while significant effect of intra-particle diffusion resistance in uniform catalysts was present, the eggshell catalysts remarkably reduced such diffusion effect due to a decreased reactant diffusion path, thus showing higher HDS selectivity. [ABSTRACT FROM AUTHOR]