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Chinese Journal of Catalysis
2015, Vol. 36, No. 11
Online: 02 November 2015


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Jia and co-workers in their Article on pages 1811–1817 reported that two copper complex-modified polyoxometalates [Cu(bipy)]₄[Mo₁₅O₄₇]·2H₂O and [Cu(bix)][(Cubix)(δ-Mo₈O₂₆)_0.5] are active and stable catalysts for the epoxidation of olefins with tert-butyl hydroperoxide as oxidant. Their excellent stability is attributed to the presence of stable coordination bonds between the molybdenum oxide and copper complex.

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Table of Contents for VOL.36 No.11 2015, 36 (11):  0-0.  Abstract ( 171 )   PDF (4435KB) ( 713 )

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Graphene derivatives supported nanocatalysts for oxygen reduction reaction Ilkeun Lee, Ji Bong Joo, Mohammadreza Shokouhimehr 2015, 36 (11):  1799-1810.  DOI: 10.1016/S1872-2067(15)60971-8 Abstract ( 354 )   [Full Text(HTML)] () PDF (1694KB) ( 910 )   Very recent progress on the graphene derivatives supported variable nanocatalysts for oxygen reduction reaction (ORR) in fuel cell is reviewed. First, common electrochemical techniques to characterize graphene-based electrocatalysts are mentioned. Second, recent updates on graphene-derived electrocatalysts are introduced. In this part, both electrochemical activity and stability of Pt catalysts can be improved when they are supported by reduced graphene oxide (RGO). Other noble-metal catalysts including Pd, Au, and Ag showing comparable performance have been investigated. The stability of Pd catalyst is enhanced by RGO or few-layered graphene support. Synthetic approaches for Au or Ag catalysts supported on graphene oxide are discussed. In addition, non-noble transition metals in N4-chelate complexes can reduce oxygen electrochemically. Fe and Co are cheap alternative catalysts for ORR. In most cases, the stability and tolerance issues are overcome well, but their overall performances don't seem to surpass Pt/C catalyst yet.

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Catalytic epoxidation of olefin over supramolecular compounds of molybdenum oxide clusters and a copper complex Hongcheng Gao, Yan Yan, Xiaohong Xu, Jiehui Yu, Huiling Niu, Wenxiu Gao, Wenxiang Zhang, Mingjun Jia 2015, 36 (11):  1811-1817.  DOI: 10.1016/S1872-2067(15)60919-6 Abstract ( 346 )   [Full Text(HTML)] () PDF (732KB) ( 718 )   The catalytic epoxidation of olefin was investigated on two copper complex-modified molybdenum oxides with a 3D supramolecular structure, [Cu(bipy)]4[Mo15O47]·2H2O (1) and [CuI(bix)][(CuIbix) (δ-MoVI8O26)0.5] (2) (bipy = 4,4'-bipyridine, bix = 1,4-bis(imidazole-1-ylmethyl)benzene). Both compounds were catalytically active and stable for the epoxidation of cyclooctene, 1-octene, and styrene with tert-butyl hydroperoxide (t-BuOOH) as oxidant. The excellent catalytic performance was attributed to the presence of stable coordination bonds between the molybdenum oxide and copper complex, which resulted in the formation of easily accessible Mo species with high electropositivity. In addition, the copper complex also acted as an active site for the activation of t-BuOOH, thus improving these copper complex-modified polyoxometalates.

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Kinetics and mechanism of thymine degradation by TiO2 photocatalysis L. Elsellami, N. Hafidhi, F. Dappozze, A. Houas, C. Guillard 2015, 36 (11):  1818-1824.  DOI: 10.1016/S1872-2067(15)60967-6 Abstract ( 306 )   [Full Text(HTML)] () PDF (476KB) ( 792 )   The advanced oxidation processes were examined toward the degradation of thymine (C5H6N2O2), a type of nucleic acid from the pyrimidine family. As observed, the photodegradation of thymine over TiO2 photocatalyst was rapid and significant in aqueous solution under UV irradiation. Different parameters were studied, including the adsorption of thymine onto TiO2 photocatalyst, the kinetics of degradation, and the effect of pH on the photocatalytic properties of thymine degradation. Additionally, the mineralization of the products obtained upon thymine photodegradation was studied. The disappearance and mineralization rates of thymine during the photocatalytic process were also compared and discussed. The mineralization of nitrogen was also investigated, and the identification of the intermediate products was established. Finally, electronic density calculations were used to propose possible chemical pathways for the photodegradation of thymine over TiO2 photocatalyst under UV irradiation.

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Catalytic role of Cu(I) species in Cu2O/CuI supported on MWCNTs in the oxidative amidation of aryl aldehydes with 2-aminopyridines H. N. Hareesh, K. U. Minchitha, N. Nagaraju, N. Kathyayini 2015, 36 (11):  1825-1836.  DOI: 10.1016/S1872-2067(15)60964-0 Abstract ( 216 )   [Full Text(HTML)] () PDF (1193KB) ( 926 )   Cu2O and CuI were supported on multiwalled carbon nanotubes (MWCNTs) using a wet impregnation method, and the resulting materials were fully characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, transmission electron microscopy, and temperature-programmed desorption with ammonia analysis. The results of these experiments revealed that Cu2O and CuI were deposited on the MWCNTs in the cubic and γ phases, respectively. These results also showed that the Cu-containing MWCNTs exhibited weak to strong electron-accepting (Lewis acidic) properties. The catalytic activities of these materials were studied for the synthesis of biologically significant N-(pyridin-2-yl)benzamides via the oxidative amidation of aryl aldehydes with 2-aminopyridines. The yields of the products were in the range 50%-95% with 100% selectivity. Notably, the CuI/MWCNT catalyst was much more effective than the Cu2O/MWCNT catalyst with respect to the isolated yield of the product, although the latter of these two catalysts exhibited much better recyclability. A preferential interaction was observed between the polar nature of the acid-activated MWCNTs and the ionic Cu2O compared with covalent CuI. The differences in these interactions had a significant impact on the rate of the nucleophilic attack of the amino group of 2-aminopyridine substrate on the carbonyl group of the aryl aldehyde.

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The role of alkali promoters in enhancing the direct N2O decomposition reactivity over NiO catalysts Bahaa M. Abu-Zied, Abdullah M. Asiri 2015, 36 (11):  1837-1845.  DOI: 10.1016/S1872-2067(15)60963-9 Abstract ( 206 )   [Full Text(HTML)] () PDF (600KB) ( 607 )   Direct N2O decomposition has been investigated over bare NiO and a series of its alkali-promoted catalysts. These catalysts were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy. XPS analysis revealed that surface nickel is present in three forms: metal particles, NiO and Ni(OH)2. It is suggested that nickel(0) valent atoms are essential for the interaction with N2O molecules at the catalyst surfaces. Bare NiO exhibited a very low N2O decomposition reactivity. However, the alkali-containing catalysts exhibited a marked activity enhancement.

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Synthesis and characterization of hierarchical nanoporous HY zeolites from acid-activated kaolin Peter Adeniyi Alaba, Yahaya Muhammad Sani, Wan Mohd Ashri Wan Daud 2015, 36 (11):  1846-1851.  DOI: 10.1016/S1872-2067(15)60962-7 Abstract ( 201 )   [Full Text(HTML)] () PDF (526KB) ( 660 )   Hierarchical nanoporous HY zeolites were synthesized from acid-activated kaolin. The hierarchical factor (HF) was maximized by varying the aging and crystallization time. This was achieved by maximizing the external surface area without greatly reducing the micropore volume. The resulting products were characterized using X-ray diffraction (XRD), X-ray fluorescence, N2 adsorption, and NH3 temperature-programmed desorption. The nanoporous HY zeolite with the highest HF was obtained by aging for 48 h and a crystallization time of 24 h. The acidity and crystallinity varied depending on the operating parameters. Incorporation of an appropriate amount of NaCl was also vital in maximizing the HF, crystallinity, and acidity. The sample crystallinities were determined by comparing their XRD peak intensities with those of a conventional Y zeolite. The results show that optimizing this process could lead to a widely acceptable commercial route for HY zeolite production.

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Efficient preparation of Zr(IV)-salen grafted mesoporous MCM-41 catalyst for chemoselective oxidation of sulfides to sulfoxides and Knoevenagel condensation reactions Maryam Hajjami, Farshid Ghorbani, Sedighe Rahimipanah, Safoora Roshani 2015, 36 (11):  1852-1860.  DOI: 10.1016/S1872-2067(15)60968-8 Abstract ( 318 )   [Full Text(HTML)] () PDF (528KB) ( 635 )   Zr(IV)-salen-MCM-41 was prepared by reaction of NH2-MCM-41 with salicylaldehyde to afford Schiff base ligands. Thereafter, ZrOCl2·8H2O was reacted with the Schiff base ligands for complex formation. The structural properties of the synthesized materials were investigated by a number of analytical techniques including X-ray diffraction, N2 sorption-desorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscpopy, and energy dispersive X-ray spectroscopy. Catalytic studies of the mesoporous materials functionalized with Zr(IV)-Schiff base complexes were investigated and extended to selective oxidation of sulfides to sulfoxides and the Knoevenagel condensation reactions of aldehydes with malononitriles and ethyl cyanoacetate. Additionally, catalyst recycling of the Zr-salen-MCM-41 materials was also studied.

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Alkali-metal-modified ZSM-5 zeolites for improvement of catalytic dehydration of lactic acid to acrylic acid Chuan Yuan, Huayan Liu, Zekai Zhang, Hanfeng Lu, Qiulian Zhu, Yinfei Chen 2015, 36 (11):  1861-1866.  DOI: 10.1016/S1872-2067(15)60970-6 Abstract ( 437 )   [Full Text(HTML)] () PDF (557KB) ( 806 )   Various ZSM-5 zeolites modified with alkali metals (Li, Na, K, Rb, and Cs) were prepared using ion exchange. The catalysts were used to enhance the catalytic dehydration of lactic acid (LA) to acrylic acid (AA). The effects of cationic species on the structures and surface acid-base distributions of the ZSM-5 zeolites were investigated. The important factors that affect the catalytic performance were also identified. The modified ZSM-5 catalysts were characterized using X-ray diffraction, temperature-programmed desorptions of NH3 and CO2, pyridine adsorption spectroscopy, and N2 adsorption to determine the crystal phase structures, surface acidities and basicities, nature of acid sites, specific surface areas, and pore volumes. The results show that the acid-base sites that are adjusted by alkali-metal species, particularly weak acid-base sites, are mainly responsible for the formation of AA. The KZSM-5 catalyst, in particular, significantly improved LA conversion and AA selectivity because of the synergistic effect of weak acid-base sites. The reaction was conducted at different reaction temperatures and liquid hourly space velocities (LHSVs) to understand the catalyst selectivity for AA and trends in byproduct formation. Approximately 98% LA conversion and 77% AA selectivity were achieved using the KZSM-5 catalyst under the optimum conditions (40 wt% LA aqueous solution, 365 ℃, and LHSV 2 h-1).

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Synergistic effect of cobalt and copper on a nickel-based modified graphite electrode during methanol electro-oxidation in NaOH solution Tayebe Rostami, Majid Jafarian, Somaieh Miandari, Mohammad G. Mahjani, Fereydoon Gobal 2015, 36 (11):  1867-1874.  DOI: 10.1016/S1872-2067(15)60959-7 Abstract ( 245 )   [Full Text(HTML)] () PDF (1078KB) ( 568 )   The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution (0.1 mol/L). The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It was found that, in the presence of methanol, the modified Ni-based ternary alloy electrode (G/NiCuCo) exhibited a significantly higher response for methanol oxidation compared to the other samples. The anodic peak currents showed a linear dependency on the square root of the scan rate, which is a characteristic of a diffusion controlled process. During CA studies, the reaction exhibited Cottrellin behavior and the diffusion coefficient of methanol was determined to be 6.25×10-6 cm2/s and the catalytic rate constant, K, for methanol oxidation was found to be 40×107 cm3/(mol·s). EIS was used to investigate the catalytic oxidation of methanol on the surface of the modified electrode.

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One-pot synthesis of a hierarchical microporous-mesoporous phosphotungstic acid-HKUST-1 catalyst and its application in the selective oxidation of cyclopentene to glutaraldehyde Xinli Yang, Liming Qiao, Weilin Dai 2015, 36 (11):  1875-1885.  DOI: 10.1016/S1872-2067(15)60972-X Abstract ( 326 )   [Full Text(HTML)] () PDF (670KB) ( 1120 )   A hierarchical microporous-mesoporous metal-organic framework of HKUST-1(Cu)-encapsulated phosphotungstic acid (HPW) material, referred to as HPWs@Meso-HKUST-1, is prepared by a one-pot synthesis method using cetyltrimethylammonium bromide as the supramolecular template. The addition of HPWs to the synthesis mixture of hierarchical porous HKUST-1 results in the direct encapsulation of HPWs inside the mesopores of the HKUST-1 structure, with a homogeneous distribution over the HKUST-1 crystals, which is confirmed by XRD, FT-IR, N2 adsorption, UV-Vis DRS, and TEM. FT-IR-CO adsorption experiments indicated that additional Lewis acid sites were present in the HPWs@Meso-HKUST-1 sample. The novel heterogeneous catalyst demonstrates excellent catalytic performance for the selective oxidation of cyclopentene (CPE) to glutaraldehyde (GA) using tert-butyl hydroperoxide and acetonitrile (MeCN) as the oxidant and solvent, respectively. The high activity of the catalyst is attributed to the mesostructure of the catalyst and the nature and appropriate abundance of the HPWs—being highly dispersed with the addition of Lewis sites. After a reaction for 36 h, the 30% wt% HPWs@Meso-HKUST-1 catalyst exhibits a CPE conversion of 92.5% and a high GA yield of 73%. Furthermore, the HPWs@Meso-HKUST-1 material is sufficiently stable to prevent the leaching of HPWs, and behaves as a true heterogeneous catalyst that can be repeatedly recycled without sustaining a loss of activity and selectivity in the selective oxidation of CPE.

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Highly dispersed V2O5/TiO2 modified with transition metals (Cu, Fe, Mn, Co) as efficient catalysts for the selective reduction of NO with NH3 Xin Zhao, Lei Huang, Hongrui Li, Hang Hu, Jin Han, Liyi Shi, Dengsong Zhang 2015, 36 (11):  1886-1899.  DOI: 10.1016/S1872-2067(15)60958-5 Abstract ( 437 )   [Full Text(HTML)] () PDF (1201KB) ( 928 )   Different transition metals were used to modify V2O5-based catalysts (M-V, M = Cu, Fe, Mn, Co) on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in the vanadium species and the formation of vanadates on the TiO2 support, and increased the amount of surface acid sites and the strength of these acids. The strong acid sites might be responsible for the high N2 selectivity at higher temperatures. Among these catalysts, Cu-V/TiO2 showed the highest activity and N2 selectivity at 225-375 ℃. The results of X-ray photoelectron spectroscopy, NH3-temperature-programmed desorption, and in-situ diffuse reflectance infrared Fourier transform spectroscopy suggested that the improved performance was probably due to more active surface oxygen species and increased strong surface acid sites. The outstanding activity, stability, and SO2/H2O durability of Cu-V/TiO2 make it a candidate to be a NOx removal catalyst for stationary flue gas.

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Effects of structures of molybdenum catalysts on selectivity in gas-phase propylene oxidation Martin Šustek, Blažej Horváth, Ivo Vávra, Miroslav Gál, Edmund Dobročka, Milan Hronec 2015, 36 (11):  1900-1909.  DOI: 10.1016/S1872-2067(15)60961-5 Abstract ( 402 )   [Full Text(HTML)] () PDF (1213KB) ( 683 )   Molybdenum-based catalysts for the gas-phase oxidation of propylene with air were investigated. Various types of silica-supported molybdenum oxide and molybdenum-bismuth mixed oxide catalysts were prepared from inorganic and organometallic molybdenum precursors using wet impregnation and physical vapor deposition methods. The epoxidation activities of the prepared catalysts showed direct correlations with their nanostructures, which were identified using transmission electron microscopy. The appearance of a partly or fully crystalline molybdenum oxide phase, which interacted poorly with the silica support, decreased the selectivity for propylene oxide formation to below 10%; non-crystalline octahedrally coordinated molybdenum species anchored on the support gave propylene oxide formations greater than 55%, with 11% propylene conversion. Electrochemical characterization of molybdenum oxides with various morphologies showed the importance of structural defects. Direct promotion by bismuth of the epoxidation reactivities over molybdenum oxides is disputed.

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Facile preparation of nanocrystal-assembled hierarchical mordenite zeolites with remarkable catalytic performance Yangyang Yuan, LinyingWang, Hongchao Liu, PengTian, Miao Yang, Shutao Xu, ZhongminLiu 2015, 36 (11):  1910-1919.  DOI: 10.1016/S1872-2067(15)60960-3 Abstract ( 298 )   [Full Text(HTML)] () PDF (1089KB) ( 780 )   The present study reports a novel strategy to fabricate nanocrystal-assembled hierarchical MOR zeolites. This is the first demonstration of hierarchical MOR without preferential growth along the c-axis, which facilitates mass transfer in the 12-membered ring channels of MOR zeolite for the conversions involving bulky molecules. The facile method involves the combined use of tetraethylammonium hydroxide (TEAOH) and commercial surfactants, in which TEAOH is essential for the construction of nanocrystal assemblies. The surfactant serves as a crystal growth-inhibiting agent to further inhibit nanocrystalline particle growth, resulting in enhanced mesoporosity. The hierarchical MOR assembled particles, constructed of 20-50-nm crystallites, exhibit superior catalytic properties in the alkylation of benzene with benzyl alcohol compared with the control sample, as the hierarchical MOR possesses a larger external surface area and longer c-axis dimension. More importantly, the material shows improved activity and stability in the dimethyl ether carbonylation to methyl acetate reaction, which is a novel route to produce ethanol from syngas.

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Carbon monoxide oxidation on copper manganese oxides prepared by selective etching with ammonia Lei Shi, Zhen-Hao Hu, Gao-Ming Deng, Wen-Cui Li 2015, 36 (11):  1920-1927.  DOI: 10.1016/S1872-2067(15)60947-0 Abstract ( 350 )   [Full Text(HTML)] () PDF (3068KB) ( 625 )   A series of copper manganese oxides were prepared using a selective etching technique with various amounts of ammonia added during the co-precipitation process. The effect of the ammonia etching on the structure and catalytic properties of the copper manganese oxides was investigated using elemental analysis, nitrogen physisorption, X-ray powder diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, and O2 temperature-programmed desorption combined with catalytic oxidation of CO. It was found that ammonia can selectively remove copper species from the copper manganese oxides, which correspondingly generates more defects in these oxides. An oxygen spillover from the manganese to the copper species was observed by H2 temperature-programmed desorption, indicating that ammonia etching enhanced the mobility of lattice oxygen species in these oxides. The O2 temperature-programmed desorption measurements further revealed that ammonia etching improved the ability of these oxides to release lattice oxygen. The improvement in redox properties of the copper manganese oxides following ammonia etching was associated with enhanced catalytic performance for CO oxidation.

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Seed-induced synthesis of small-crystal TS-1 using ammonia as alkali source Teng Xue, Huaping Liu, Yimeng Wang, Haihong Wu, Peng Wu, Mingyuan He 2015, 36 (11):  1928-1935.  DOI: 10.1016/S1872-2067(15)60955-X Abstract ( 321 )   [Full Text(HTML)] () PDF (860KB) ( 823 )   Small-crystal TS-1 was synthesized via a seed-induced approach using ammonia as the alkali source and tetrapropylammonium bromide as an auxiliary structure-directing agent. The TS-1 samples were characterized using X-ray diffraction, N2 adsorption-desorption, Fourier-transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. The use of the colloidal seed reduced the crystal size, and an appropriate amount of silicalite-1 seed assisted Ti incorporation into the TS-1 framework. This method reduces the cost of TS-1 synthesis because a significantly smaller amount of tetrapropylammonium hydroxide is used. The catalytic performance of the synthesized small-crystal TS-1 samples in cyclohexanone ammoximation was better than that of bulk TS-1 as a result of improved diffusion and a larger number of active tetrahedral Ti centers.

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Electrochemically reduced graphene oxide with enhanced electrocatalytic activity toward tetracycline detection Yanyan Xu, Mingming Gao, Guohui Zhang, Xinhua Wang, Jiajia Li, Shuguang Wang, Yuanhua Sang 2015, 36 (11):  1936-1942.  DOI: 10.1016/S1872-2067(15)60956-1 Abstract ( 449 )   [Full Text(HTML)] () PDF (538KB) ( 574 )   An electrochemically reduced graphene oxide sample, ERGO-0.8V, was prepared by electrochemical reduction of graphene oxide (GO) at -0.8 V, which shows unique electrocatalytic activity toward tetracycline (TTC) detection compared to the ERGO-1.2V (GO applied to a negative potential of -1.2 V), GO, chemically reduced GO (CRGO)-modified glassy carbon electrode (GC) and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8V-modified glass carbon electrode (GC/ERGO-0.8V) were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L. Physical characterizations with Fourier transform infrared (FT-IR), Raman, and X-ray photoelectron spectroscopies (XPS) demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8V electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.

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Black TiO2(B)/anatase bicrystalline TiO2-x nanofibers with enhanced photocatalytic performance Licheng Li, Kangzhong Shi, Rui Tu, Qi Qian, Dong Li, Zhuhong Yang, Xiaohua Lu 2015, 36 (11):  1943-1948.  DOI: 10.1016/S1872-2067(15)60946-9 Abstract ( 244 )   [Full Text(HTML)] () PDF (540KB) ( 740 )   Black TiO2(B)/anatase bicrystalline TiO2-x nanofibers were synthesized from a porous titanate derivative by calcination in H2, and were characterized using field-emission scanning electron microscopy, Raman spectroscopy, N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, ultraviolet-visible diffuse reflection spectroscopy and photoluminescence measurements. Characterization results showed that no Ti3+ was present on the surface of black bicrystalline TiO2-x and oxygen vacancies were distributed in the bulk of both TiO2(B) and anatase phases. The O/Ti atom stoichiometric ratio of black bicrystalline TiO2-x was estimated to be 1.97 from the difference of mass loss between black bicrystalline TiO2-x and white bicrystalline TiO2 without oxygen vacancies. The photocatalytic activity of black bicrystalline TiO2-x was 4.2 times higher than that of white bicrystalline TiO2 and 10.5 times higher than that of anatase TiO2. The high photocatalytic activity of black bicrystalline TiO2-x was attributed to its effective separation of electrons and holes, which may be related to the effects of both bicrystalline structure and oxygen vacancies. Black bicrystalline TiO2-x also exhibited good photocatalytic activity after recycling ten times. The black bicrystalline TiO2-x nanofibers show potential for use in environmental and energy applications.

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Amine-grafted on lanthanide metal-organic frameworks: Three solid base catalysts for Knoevenagel condensation reaction Yanwei Ren, Jiaxian Lu, Ou Jiang, Xiaofei Cheng, Jun Chen 2015, 36 (11):  1949-1956.  DOI: 10.1016/S1872-2067(15)60945-7 Abstract ( 280 )   [Full Text(HTML)] () PDF (589KB) ( 904 )   A post-synthetic modification strategy has been used to prepare three solid base catalysts, including Er(btc)(ED)0.75(H2O)0.25 (2, btc = 1,3,5-benzenetricarboxylates, ED = 1,2-ethanediamine), Er(btc)(PP)0.55(H2O)0.45 (3, PP = piperazine), and Er(btc)(DABCO)0.15(H2O)0.85 (4, DABCO = 1,4- diazabicyclo[2.2.2]octane), by grafting three different diamines onto the coordinatively unsaturated Er(III) ions into the channels of the desolvated lanthanide metal-organic framework (Er(btc)). The resulting metal-organic frameworks were characterized by elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and N2 adsorption. Based on its higher loading ratio of the diamine, as well as its greater stability and porosity, catalyst 2 exhibited higher catalytic activity and reusability than catalysts 3 and 4 for the Knoevenagel condensation reaction. The catalytic mechanism of 2 has also been investigated using size-selective catalysis tests.

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Synthesis of K-doped three-dimensionally ordered macroporous Mn0.5Ce0.5Oδ catalysts and their catalytic performance for sootoxidation Xuehua Yu, Zhen Zhao, Yuechang Wei, Jian Liu, Jianmei Li, Aijun Duan, Guiyuan Jiang 2015, 36 (11):  1957-1967.  DOI: 10.1016/S1872-2067(15)60949-4 Abstract ( 260 )   [Full Text(HTML)] () PDF (1660KB) ( 724 )   A series of K-doped Mn0.5Ce0.5Oδ (K-MCO) catalysts with three-dimensionally ordered macroporous (3DOM) structure and different K loadings were successfully synthesized using simple methods. These catalysts exhibited well-defined 3DOM nanostructure, which consisted of extensive interconnecting networks of spherical voids. The effects of the calcination temperature and calcination time on the morphological characteristics and crystalline forms of the catalysts were systematically studied. The catalysts showed high catalytic activity for the combustion of soot. 3DOM 20% K-MCO-4h catalyst, in particular, showed the highest catalytic activity of all of the catalysts studied (e.g., T50 = 331 ℃ and SmCO2 = 95.3%). The occurrence of structural and synergistic effects among the K, Mn, and Ce atoms in the catalysts was favorable for enhancing their catalytic activity towards the combustion of diesel soot. Furthermore, the temperatures required for the complete combustion of the soot (<400 ℃) were well within the exhaust temperature range (175-400 ℃), which means that the accumulated soot can be removed under the conditions of the diesel exhaust gas. These catalysts could therefore be used in numerous practical applications because they are easy to synthesize, exhibit high catalytic activity, and can be made from low cost materials.

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Ultrafine metal nanoparticles loaded on TiO2 nanorods: Synthesis strategy and photocatalytic activity Weijiong Dai, Junqing Yan, Ke Dai, Landong Li, Naijia Guan 2015, 36 (11):  1968-1975.  DOI: 10.1016/S1872-2067(15)60954-8 Abstract ( 384 )   [Full Text(HTML)] () PDF (964KB) ( 749 )   Ultrafine noble metal nanoparticles (Pt, Pd, or Au) co-catalyst loaded on the surface of rutile and brookite TiO2 were prepared via a simple photo-deposition strategy under high vacuum conditions. The properties of the prepared samples were determined by different characterization techniques, including X-ray diffraction, transmission electron microscopy, diffuse reflectance ultraviolet-visible spectroscopy, and photoluminescence spectroscopy. The photocatalytic performance of the samples was evaluated by monitoring the reforming of methanol. Co-catalyst loading greatly improved the photocatalytic activity of TiO2. Specifically, Pt-TiO2 displayed the highest photocatalytic activity among all samples studied, followed by Pd-TiO2 and then Au-TiO2. Furthermore, this photocatalytic behavior was not influenced by the intrinsic nature of the TiO2 semiconductor photocatalyst. Similar photocatalytic activity trends were achieved with both sets of noble metal-loaded photocatalysts prepared using rutile and brookite TiO2 as supports. By examining the physicochemical and photocatalytic properties, the factors controlling the photocatalytic activity of the noble metal-loaded TiO2 samples were discussed in detail.

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Enhanced CO oxidation over potassium-promoted Pt/Al2O3 catalysts: Kinetic and infrared spectroscopic study Huanhuan Liu, Aiping Jia, Yuwang, Mengfei Luo, Jiqing Lu 2015, 36 (11):  1976-1986.  DOI: 10.1016/S1872-2067(15)60950-0 Abstract ( 277 )   [Full Text(HTML)] () PDF (745KB) ( 602 )   A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents (51.6 kJ/mol for 0.42K-2.0Pt/Al2O3 and 63.6 kJ/mol for 2.0Pt/Al2O3). The CO reaction orders were higher for the K-containing catalysts (about -0.2) than for the K-free ones (about -0.5), with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.

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Sonocatalytic activity of LuFeO3 crystallites synthesized via a hydrothermal route Ming Zhou, Hua Yang, Tao Xian, Yang Yang, Yunchuan Zhang 2015, 36 (11):  1987-1994.  DOI: 10.1016/S1872-2067(15)60941-X Abstract ( 393 )   [Full Text(HTML)] () PDF (611KB) ( 764 )   LuFeO3 crystallites of different sizes and morphologies were synthesized via a hydrothermal route. The sonocatalytic properties of the as-synthesized samples were investigated by degrading various organic dyes, including acid orange 7 (AO7), rhodamine B (RhB), methyl orange (MO), and methylene blue (MB), under ultrasonic irradiation, revealing that they exhibit excellent sonocatalytic activity toward the degradation of these dyes. Particularly, the synthesized bar-like particles with lengths of ~3 μm and widths of ~1 μm have the highest sonocatalytic activity, and the degradation percentage of AO7 reaches 89% after 30 min of sonocatalysis. The effects of inorganic anions such as Cl-, NO3-, SO42-, PO43-, and HCO3- on the sonocatalysis efficiency were investigated. Hydroxyl radicals (·OH) detected by fluorimetry using terephthalic acid as a probe molecule were found to be produced over the ultrasonic-irradiated LuFeO3 particles. The addition of ethanol, which acts as a ·OH scavenger, leads to quenching of ·OH radicals and a simultaneous decrease in the dye degradation. This suggests that ·OH is the dominant active species responsible for the dye degradation.

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Pt nanoparticles entrapped in ordered mesoporous carbons: An efficient catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives Junrui Li, Xiaohong Li, Yue Ding, Peng Wu 2015, 36 (11):  1995-2003.  DOI: 10.1016/S1872-2067(15)60937-8 Abstract ( 358 )   [Full Text(HTML)] () PDF (756KB) ( 633 )   Pt nanoparticles entrapped in ordered mesoporous CMK-3 carbons with p6mm symmetry were prepared using a facile impregnation method, and the resulting materials were characterized using X-ray diffraction spectroscopy, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The Pt nanoparticles were highly dispersed in the CMK-3 with 43.7% dispersion. The Pt/CMK-3 catalyst was an effective catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives under the experimental conditions studied here. The Pt/CMK-3 catalyst was more active than commercial Pt/C catalyst in most cases. A highest turnover frequency of 43.8 s-1 was measured when the Pt/CMK-3 catalyst was applied for the hydrogenation of 2-methyl-nitrobenzene in ethanol under optimal conditions. It is worthy of note that the Pt/CMK-3 catalyst could be recycled easily, and could be reused at least fourteen times without any loss in activity or selectivity for the hydrogenation of nitrobenzene in ethanol.

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SnO2 nano-sheet as an efficient catalyst for CO oxidation Honggen Peng, Yue Peng, Xianglan Xu, Xiuzhong Fang, Yue Liu, Jianxin Cai, Xiang Wang 2015, 36 (11):  2004-2010.  DOI: 10.1016/S1872-2067(15)60926-3 Abstract ( 256 )   [Full Text(HTML)] () PDF (737KB) ( 623 )   Polycrystalline SnO2 fine powder consisting of nano-particles (SnO2-NP), SnO2 nano-sheets (SnO2-NS), and SnO2 containing both nano-rods and nano-particles (SnO2-NR+NP) were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR+NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active (110) facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.

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Synthesis, characterization and catalytic reactivity of pentacoordinate iron dicarbonyl as a model of the [Fe]-hydrogenase active site Tianyong Zhang, Liao Sheng, Qiusheng Yang, Shuang Jiang, Yanhong Wang, Chaohui Jin, Bin Li 2015, 36 (11):  2011-2019.  DOI: 10.1016/S1872-2067(15)60920-2 Abstract ( 323 )   [Full Text(HTML)] () PDF (947KB) ( 620 )   Two mono iron complexes Fe(CO)2PR3(NN) (R = Cy (3), Ph (4), NN = o-phenylenediamine dianion ligand, N2H2Ph2-) derived from the ligand substitution of Fe(CO)3I2PR3 by the NN ligand were isolated and structurally characterized by single crystal X-ray diffraction. They have a similar first coordination sphere and oxidation state of the iron center as the [Fe]-hydrogenase active site, and can be a model of it. IR demonstrated that the effect of the NN ligand on the coordinated CO stretching frequencies was due to its excellent electron donating ability. The reversible protonation/deprotonation of the NN ligand was identified by infrared spectroscopy and density functional theory computation. The NN ligand is an effective proton acceptor as the internal base of the cysteine thiolate ligand in [Fe]-hydrogenase. The electrochemical properties of complexes 3, 4 were investigated by cyclic voltammograms. Complex 3 catalyzed the transfer hydrogenation of benzoquinone to hydroquinone effectively under mild conditions.

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Highly selective production of phenol from benzene over mesoporous silica-supported chromium catalyst: Role of response surface methodology in optimization of operating variables Milad Jourshabani, Alireza Badiei, Negar Lashgari, Ghodsi Mohammadi Ziarani 2015, 36 (11):  2020-2029.  DOI: 10.1016/S1872-2067(15)60898-1 Abstract ( 240 )   [Full Text(HTML)] () PDF (3817KB) ( 661 )   A Cr/SBA-16 catalyst was prepared using Cr(NO3)3 as a precursor and mesoporous silica SBA-16 as a support via a simple impregnation method. The catalyst was characterized using wide-angle X-ray diffraction (XRD), low-angle XRD, N2 adsorption-desorption, transmission electron microscopy, and ultraviolet-visible spectroscopy. The catalyst activity was investigated in the direct hydroxylation of benzene to phenol using H2O2 as the oxidant. Various operating variables, namely reaction temperature, reaction time, amount of H2O2, and catalyst dosage, were optimized using central composite design combined with response surface methodology (RSM). The results showed that the correlation between the independent parameters and phenol yield was represented by a second-order polynomial model. The high correlation coefficient (R2), i.e., 0.985, showed that the data predicted using RSM were in good agreement with the experimental results. The optimization results also showed that high selectivity for phenol was achieved at the optimized values of the operating variables: reaction temperature 324 K, reaction time 8 h, H2O2 content 3.28 mL, and catalyst dosage 0.09 g. This study showed that RSM was a reliable method for optimizing process variables for benzene hydroxylation to phenol.

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High selectivity to p-chloroaniline in the hydrogenation of p-chloronitrobenzene on Ni modified carbon nitride catalyst Teng Fu, Pei Hu, Tao Wang, Zhen Dong, Nianhua Xue, Luming Peng, Xuefeng Guo, Weiping Ding 2015, 36 (11):  2030-2035.  DOI: 10.1016/S1872-2067(15)60904-4 Abstract ( 422 )   [Full Text(HTML)] () PDF (1325KB) ( 671 )   A nanocomposite composed of Ni modified carbon nitride was synthesized and used in the hydrogenation of p-chloronitrobenzene. H/D exchange demonstrated that the hydrogen chemisorbed on the surface of this nanocomposite catalyst had a hydrogen atom density of 0.65/nm2. It was active for hydrogenation but its activity was inferior to the hydrogen adsorbed on a Ni/Al2O3 catalyst. Catalytic tests showed that this catalyst possessed a lower activity than Ni/Al2O3 but the selectivity towards p-chloroaniline was above 99.9%. Even at high conversion, the catalyst maintained high selectivity, which was attributed to the unique surface property of the catalyst and the absence of a site for the adsorption of p-chloronitrobenzene, which prevents the C-Cl bond from breaking.

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Catalytic synthesis of diethyl carbonate with supported Pd-Cu bimetallic nanoparticle catalysts: Cu(I) as the active species Pingbo Zhang, Yan Zhou, Mingming Fan, Pingping Jiang 2015, 36 (11):  2036-2043.  DOI: 10.1016/S1872-2067(15)60973-1 Abstract ( 254 )   [Full Text(HTML)] () PDF (1201KB) ( 797 )   Cupric oxide (CuO) and copper-cuprous oxide (Cu-Cu2O) nanoparticles were prepared by a simple hydrothermal method for the synthesis of diethyl carbonate (DEC) from ethanol. During these syntheses, varying NaOH and glucose concentrations were applied to explore and pinpoint the active species. It was found that PdCl2/CuO and PdCl2/Cu-Cu2O both catalysts exhibited good thermal stability and morphology. The results of catalytic tests showed that the catalysts prepared with 5 mol/L NaOH show superior catalytic performances because of their lower extent of agglomeration. It is noteworthy that the PdCl2/Cu-Cu2O catalysts were the most active, especially the PdCl2/Cu-Cu2O catalyst prepared with 10 mmol glucose and having a higher Cu2O concentration. In Pd(II)-Cu(II) (PdCl2/CuO) catalysts, there is an induction period, during which Pd(II) is reduced to Pd(0), that must occur prior to electron transfer between Pd and Cu, and this can slow the catalytic reaction. To further pinpoint the active species, PdCl2/Cu-Cu2O catalysts with different Cu2O contents were prepared by controlling the dosages of glucose. The maximum DEC yield obtained with these catalysts was 151.9 mg·g-1·h-1, corresponding to an ethanol conversion of 7.2% and 97.9% DEC selectivity on an ethanol basis. Therefore, it was concluded that Cu+ was the active species in this catalytic system, possibly because a higher proportion of Cu+ reduces the Pd2+ concentration and limits the CO oxidation side reaction, thus increasing DEC selectivity. In addition, Cu+ promotes electron transfer between Pd and Cu without an induction period, which could also promote the catalytic activity.

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Author Index 2015, 36 (11):  2044-2044.  Abstract ( 175 )   [Full Text(HTML)] () PDF (259KB) ( 388 )