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Chinese Journal of Catalysis
2017, Vol. 38, No. 5
Online: 18 May 2017


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Li et al.reported two doping systems,Cu doped NiO and Ni doped CuO on pages 767-774.The atomic ratio of Cu,Ni and O in the two systems is the same but the crystal phase of the two semiconductors remains unchanged. After modification,both the two doping systems turned into magnetic photocatalytic materials with high activity,which can be easily recycled as well.

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Table of Contents for VOL.38 No.5 2017, 38 (5):  0-0.  Abstract ( 158 )   PDF (1557KB) ( 579 )

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LSDA+U study on the electronic and anti-ferromagnetic properties of Ni-doped CuO and Cu-doped NiO Yujie Li, Fan Yang, Ying Yu 2017, 38 (5):  767-774.  DOI: 10.1016/S1872-2067(17)62796-7 Abstract ( 491 )   [Full Text(HTML)] () PDF (576KB) ( 846 )   Doping is an effective way to improve the activity of photocatalysts. The effect of doping on the magnetic properties of some photocatalysts that are easily recycled was studied using the local spin density approximation (LSDA)+U method on typical divalent metal oxide semiconductors CuO, NiO, Ni-doped CuO, and Cu-doped NiO. It is found that the influence of Ni doping on the spatial structure of CuO and that of Cu doping on the spatial structure of NiO are negligible because of the similar radii of Ni2+ and Cu2+. The valence band and conduction band for Ni-doped CuO are clearly spin-split, corresponding to a net effective magnetic moment of μeff = 1.66 μB. This may improve the photocatalytic efficiency and raise the recycle rate of photocatalysts. In the Cu-doped NiO system, the presence of Cu 3d states near to the Fermi level increases the width of the valence band and narrows the band gap with respect to that in pure NiO. Beyond the Cu 3d states, within the band gap, appear two energy levels around the Fermi level, which may effectively separate the electron-hole pair and also lead to enhanced absorption of visible light and infrared light. It can be concluded that the observed changes in the band structure may be helpful for improving the activity of photocatalysts and the doped systems have net magnetic moments, meaning that they are easily recycled and can be reused.

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Gold-catalyzed addition reaction between creatinine and isatin: A sustainable and green chemistry approach for the diastereoselective synthesis of 3-substituted-3-hydroxyisatins K. Parthasarathy, T. Ponpandian, C. Praveen 2017, 38 (5):  775-783.  DOI: 10.1016/S1872-2067(17)62812-2 Abstract ( 403 )   [Full Text(HTML)] () PDF (669KB) ( 773 )   The aldolization of various isatins with creatinine under gold catalysis in water has been developed. The reaction is operationally simple as the products can be isolated by simple filtration without requiring tedious solvent extraction and column chromatographic techniques. The generality of this methodology is showcased through the reactions of a wide range of isatin derivatives with creatinine to afford the respective aldol products in excellent yields with complete syn-selectivity. The scope of this chemistry is further extended to a tandem reaction involving isatins, creatinine and malononitrile to afford multicomponent products in excellent yields with complete anti-selectivity. The antioxidant potency of the synthesized compound was assessed by a spectrophotometric method, which revealed that three compounds containing halogen atoms (2c, 2d and 2e) were the most active compared with the standard.

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Enantioselective synthesis of quaternary α-aminophosphonates by organocatalytic Friedel–Crafts reactions of indoles with cyclic α-ketiminophosphonates Zhong Yan, Xiang Gao, Yong-Gui Zhou 2017, 38 (5):  784-792.  DOI: 10.1016/S1872-2067(17)62804-3 Abstract ( 289 )   [Full Text(HTML)] () PDF (661KB) ( 726 )   An efficient asymmetric Friedel–Crafts reaction has been developed for the synthesis of optically active quaternary α-aminophosphonates with up to 98% ee. The synthesis involves the reaction of cyclic α-ketiminophosphonates with indoles using an H8-BINOL-derived chiral phosphoric acid (CPA) catalyst that bears electron-withdrawing 3,5-ditrifluoromethylphenyl substituents on its 3- and 3'-positions. This Friedel–Crafts reaction of cyclic α-ketiminophosphonates was also successful with pyrrole.

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In-plasma catalytic degradation of toluene over different MnO2 polymorphs and study of reaction mechanism Ting Wang, Si Chen, Haiqiang Wang, Zhen Liu, Zhongbiao Wu 2017, 38 (5):  793-804.  DOI: 10.1016/S1872-2067(17)62808-0 Abstract ( 483 )   [Full Text(HTML)] () PDF (2174KB) ( 1256 )   α-, β-, γ- and δ-MnO2 catalysts were synthesized by a one-step hydrothermal method, and were utilized for the catalytic oxidation of toluene in a combined plasma-catalytic process. The relationship between catalytic performance and MnO2 crystal structures was investigated. It was noted that the toluene removal efficiency was 32.5% at the specific input energy of 160 J/L when non-thermal plasma was used alone. The α-MnO2 catalyst showed the best activity among the investigated catalysts, yielding a toluene conversion of 78.1% at the specific input energy of 160 J/L. For β-MnO2, γ-MnO2 and δ-MnO2, removal efficiencies of 47.4%, 66.1% and 50.0%, respectively, were achieved. By powder X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, Brunauer-Emmett-Teller, H2 temperature-programmed reduction and X-ray photoelectron spectroscopy analyses, it was concluded that the tunnel structure, the stability of the crystal in plasma, the Mn–O bond strength of MnO2 and the surface-chemisorbed oxygen species played important roles in the plasma-catalytic degradation of toluene. Additionally, the degradation routes of toluene in non-thermal plasma and in the plasma-catalytic process were also studied. It was concluded that the introduction of MnO2 catalysts enabled O3, O2, electrons and radical species in the gas to be adsorbed on the MnO2 surface via a facile interconversion among the Mn4+, Mn3+ and Mn2+ states. These four species could then be transported to the toluene or intermediate organic by-products, which greatly improved the toluene removal efficiency and decreased the final output of by-products.

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Cobalt carbonyl ionic liquids based on the 1,1,3,3-tetra-alkylguanidine cation: Novel, highly efficient, and reusable catalysts for the carbonylation of epoxides Wei Zhang, Feng Han, Jin Tong, Chungu Xia, Jianhua Liu 2017, 38 (5):  805-812.  DOI: 10.1016/S1872-2067(17)62824-9 Abstract ( 549 )   [Full Text(HTML)] () PDF (552KB) ( 819 )   A series of novel cobalt carbonyl ionic liquids based on 1,1,3,3-tetra-alkyl-guanidine, such as [1,1-dimethyl-3,3-diethylguanidinium][Co(CO)4] (3a), [1,1-dimethyl-3,3- dibutylguanidinium] [Co(CO)4] (3b), [1,1-dimethyl-3,3-tetramethyleneguanidinium][Co(CO)4] (3c), and [1,1- dimethyl-3,3-pentamethyleneguanidinium] [Co(CO)4] (3d), were synthesized in good yields and were also characterized using infrared spectroscopy, ultraviolet-visible spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, 13C NMR spectroscopy, high‐resolution mass spectrometry, differential scanning calorimetry, and thermogravimetric analysis. The four compounds exhibited high thermal and chemical stability. In addition, the catalytic performance of these compounds was investigated in the carbonylation of epoxides, with 3a exhibiting the best catalytic activity without the aid of a base as the additive. The catalyst could be reused at least six times without significant decreases of the selectivity or conversion rate. Moreover, the catalyst system exhibited good tolerance with terminal epoxides bearing alkyl, alkenyl, aryl, alkoxy, and chloromethyl functional groups.

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Effect of Pd doping on CH4 reactivity over Co3O4 catalysts from density-functional theory calculations Chengcheng Zhao, Yonghui Zhao, Shenggang Li, Yuhan Sun 2017, 38 (5):  813-820.  DOI: 10.1016/S1872-2067(17)62817-1 Abstract ( 419 )   [Full Text(HTML)] () PDF (1066KB) ( 1230 )   Palladium oxide (PdOx) and cobalt oxide (Co3O4) are efficient catalysts for methane (CH4) combustion, and Pd-doped Co3O4 catalysts have been found to exhibit better catalytic activities, which suggest synergism between the two components. We carried out first-principles calculations at the PBE+U level to investigate the Pd-doping effect on CH4 reactivity over the Co3O4 catalyst. Because of the structural complexity of the Pd-doped Co3O4 catalyst, we built Pd-doped catalyst models using Co3O4(001) slabs with two different terminations and examined CH4 reactivity over the possible Pd-O active sites. A low energy barrier of 0.68 eV was predicted for CH4 dissociation over the more reactive Pd-doped Co3O4(001) surface, which was much lower than the 0.98 and 0.89 eV that was predicted previously over the more reactive pure Co3O4(001) and (011) surfaces, respectively. Using a simple model, we predicted CH4 reaction rates over the pure Co3O4(001) and (011) surfaces, and Co3O4(001) surfaces with different amounts of Pd dopant. Our theoretical results agree well with the available experimental data, which suggests a strong synergy between the Pd dopant and the Co3O4 catalyst, and leads to a significant increase in CH4 reaction rate.

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Facile synthesis of S-doped reduced TiO2-x with enhanced visible-light photocatalytic performance Zhenyu Huang, Zhenggang Gao, Shanmin Gao, Qingyao Wang, Zeyan Wang, Baibiao Huang, Ying Dai 2017, 38 (5):  821-830.  DOI: 10.1016/S1872-2067(17)62825-0 Abstract ( 439 )   [Full Text(HTML)] () PDF (979KB) ( 1378 )   A different approach to synthesize visible-light-active sulfur (S)-doped reduced titania (S-TiO2-x) using thiourea dioxide as both the S source and reductant was developed. The structure, morphology, and optical and electronic properties of the as-prepared S-TiO2-x samples were examined by multiple techniques, such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, Brunauer-Emmett-Teller and photocurrent measurements, and electrochemical impedance spectroscopy. The photocatalytic activity of S-TiO2-x was evaluated by photodegradation of organic Rhodamine B under visible-light irradiation. The degradation rate of Rhodamine B by S-TiO2-x obtained by calcination was about 31, 2.5, and 3.6 times higher than those of pure TiO2, pristine TiO2-x, and S-doped TiO2, respectively. In addition, the as-prepared S-TiO2-x exhibited long-term stable photocatalytic performance in the degradation of Rhodamine B under visible-light illumination. This report reveals a new approach to prepare stable and highly efficient solar light-driven photocatalysts for water purification.

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Synergetic photo-epoxidation of propylene with molecular oxygen over bimetallic Au–Ag/TS-1 photocatalysts Naixu Li, Bin Yang, Ming Liu, Yong Chen, Jiancheng Zhou 2017, 38 (5):  831-844.  DOI: 10.1016/S1872-2067(17)62832-8 Abstract ( 407 )   [Full Text(HTML)] () PDF (1466KB) ( 986 )   Au–Ag bimetallic nanoparticle-supported microporous titanium silicalite-1 catalysts were prepared via a hydrothermal-immersion method, and their structures were examined. These materials serve as efficient catalysts for the photosynthesis of propylene oxide via the epoxidation of propene. The Au/Ag mass ratio and reaction temperature were demonstrated to have significant effects on the catalytic activity and selectivity of propylene oxide. The optimal formation rate (68.3 μmol/g·h) and selectivity (52.3%) toward propylene oxide were achieved with an Au:Ag mass ratio of 4:1. Notably, the strong synergistic effect between Au and Ag resulted in superior photocatalysis of the bimetallic systems compared with those of the individual systems. A probable reaction mechanism was proposed based on the theoretical and experimental results.

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Performance enhancement mechanism of Mn-based catalysts prepared under N2 for NOx removal: Evidence of the poor crystallization and oxidation of MnOx Kai Qi, Junlin Xie, De Fang, Fengxiang Li, Feng He 2017, 38 (5):  845-852.  DOI: 10.1016/S1872-2067(17)62814-6 Abstract ( 316 )   [Full Text(HTML)] () PDF (936KB) ( 1030 )   Among multitudinous metal-oxide catalysts for the selective catalytic reduction of NOx with NH3 (NH3-SCR), Mn-based catalysts have become very popular and developed rapidly in recent years because of its superior low-temperature denitrification activity, mainly originating from multi-valence of Mn. Most studies suggest that the catalytic activity of multi-component oxides is superior to that of single-component catalysts owing to the synergistic effect among the metallic elements in such materials, of which more attentions have been given to Ce as an additive owing to its powerful oxygen storage capacity, redox ability and its ready availability. As the core of SCR technology, the research points in catalyst development at the present stage of all researchers in countries mainly centralize on the optimization of active components, carriers, calcination temperature, calcination time and temperature-raising procedure, giving little thought to the effects of the calcination atmosphere. In the present work, Ce-modified Mn-based catalysts were prepared by a simple impregnation method. The effects of the calcination atmosphere (N2, air or O2) on the performance of the resulting materials during NH3-SCR and its causes of the differences were subsequently investigated and characterized using various analytical methods. Data obtained from X-ray diffraction, thermogravimetry and temperature-programmed reduction with hydrogen show that calcination under N2 reduces both the degree of oxidation and crystallization of the MnOx. Scanning electron microscopy also demonstrates that the use of N2 inhibits the growth of grains and increases the dispersion of the catalysts. In addition, the results of temperature-programmed desorption with ammonia indicate that catalysts calcined under N2 exhibit a greater quantity of acid sites. Finally, X-ray photoelectron spectrometry and activity results demonstrate that MnOx in the lower valence states is more favorable for NH3-SCR reactions. In conclusion, catalysts calcined under N2 show superior performance during NH3-SCR for NOx removal, allowing NO conversions up to 94% at 473 K.

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Brønsted-acidic ionic liquids as efficient catalysts for the synthesis of polyoxymethylene dialkyl ethers Heyuan Song, Meirong Kang, Fuxiang Jin, Guoqin Wang, Zhen Li, Jing Chen 2017, 38 (5):  853-861.  DOI: 10.1016/S1872-2067(17)62816-X Abstract ( 331 )   [Full Text(HTML)] () PDF (589KB) ( 968 )   Acetalation of formaldehyde (HCHO) with dialkyl formal or aliphatic alcohol to prepare polyoxymethylene dialkyl ethers (RO(CH2O)nR, n ≥ 1) catalyzed by Brønsted-acidic ionic liquids has been developed. The correlation between the structure and acidity activity of various ionic liquids was studied. Among the ionic liquids investigated, 1-(4-sulfonic acid)butyl-3-methylimidazolium hydrogen sulfate ([MIMBs]HSO4) exhibited the best catalytic performance in the reaction of diethoxymethane (DEM1) with trioxane. The influences of ionic liquid loading, molar ratio of DEM1 to HCHO, reaction temperature, pressure, time, and reactant source on the catalytic reaction were explored using [MIMBs]HSO4 as the catalyst. Under the optimal conditions of n([MIMBs]HSO4):n(DEM1):n(HCHO) = 1:80:80, 140℃, and 4 h, the conversion of HCHO and selectivity for DEM2-8 were 92.6% and 95.1%, respectively. The [MIMBs]HSO4 catalyst could be easily separated and reused. A feasible mechanism for the catalytic performance of [MIMBs]HSO4 was proposed.

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Quaternary-ammonium-immobilized polystyrenes as efficient and reusable heterogeneous catalysts for synthesis of cyclic carbonate: Effects of linking chains and pendent hydroxyl group Xiaoming Yan, Xuan Ding, Yu Pan, Xiaowei Xu, Ce Hao, Wenji Zheng, Gaohong He 2017, 38 (5):  862-871.  DOI: 10.1016/S1872-2067(17)62819-5 Abstract ( 393 )   [Full Text(HTML)] () PDF (1550KB) ( 1113 )   Spherical polystyrene-supported ammonium salts containing different linking chains between the support and ammonium groups were prepared as efficient and easily reusable heterogeneous catalysts for the cycloadditions of CO2 and epoxides. The effects of the length of the linking chains and a hydroxyl group pendent on the linking chain on the catalytic performance of ionic liquid immobilized catalysts and their mechanisms were studied through experiments and density functional theory calculations. It was found that, compared with a short linking chain, a long chain can make the halogen anion more negative and provide a larger contact area of the catalysts with the reactants, thus enhancing the reaction kinetics. The hydroxyl group can stretch the C–O bonds of the epoxides, promoting the reaction thermodynamics. As a result, for the cycloaddition of propylene oxide, the yield of propylene carbonate is much higher for the catalyst with a long linking chain (yield: 91.4%) compared with the yield for that with a short chain (yield: 70.9%), and is further increased in the presence of pendent hydroxyl groups (yield: 98.5%). The catalyst also shows a high catalytic activity even at mild temperature and good reusability (yield: ≥ 96% for 10 cycles), and the selectivity is always above 99%.

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Synthesis of ZSM-5 monoliths with hierarchical porosity through a steam-assisted crystallization method using sponges as scaffolds Tiejing Hu, Jian Liu, Changyan Cao, Weiguo Song 2017, 38 (5):  872-878.  DOI: 10.1016/S1872-2067(17)62828-6 Abstract ( 574 )   [Full Text(HTML)] () PDF (698KB) ( 992 )   Self-supporting ZSM-5 crystals with hierarchical porosity were prepared through a steam-assisted crystallization method using sponges as rigid scaffolds. The synthesized materials were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy, solid-state nuclear magnetic resonance spectroscopy and ammonia temperature-programmed desorption. The ZSM-5 monoliths exhibited high crystallinities, hierarchical porous structures and strong acidities. They showed superior catalytic performance in the liquid-phase esterification reaction between benzyl alcohol and hexanoic acid.

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Synthesis of propylene glycol ethers from propylene oxide catalyzed by environmentally friendly ionic liquids Cong Zhao, Shengxin Chen, Ruirui Zhang, Zihang Li, Ruixia Liu, Baozeng Ren, Suojiang Zhang 2017, 38 (5):  879-889.  DOI: 10.1016/S1872-2067(17)62831-6 Abstract ( 457 )   [Full Text(HTML)] () PDF (799KB) ( 1305 )   A series of acetate ionic liquids were synthesized using a typical two-step method. The ionic liquids were used as environmentally benign catalysts in the production of propylene glycol ethers from propylene oxide and alcohols under mild conditions. The basic strengths of the ionic liquids were evaluated by determination of their Hammett functions, obtained using ultraviolet-visible spectroscopy, and the relationship between their catalytic activities and basicities was established. The catalytic efficiencies of the ionic liquids were higher than that of the traditional basic catalyst NaOH. This can be attributed to the involvement of a novel reaction mechanism when these ionic liquids are used. A possible electrophilic-nucleophilic dual activation mechanism was proposed and confirmed using electrospray ionization quadrupole time-of-flight mass spectrometry. In addition, the effects of significant reaction parameters such as concentration of catalyst, molar ratio of alcohol to propylene oxide, reaction temperature, and steric hindrance of the alcohol were investigated in detail.

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Chiral BINAP-based hierarchical porous polymers as platforms for efficient heterogeneous asymmetric catalysis Tao Wang, Yuan Lyu, Kai Xiong, Wenlong Wang, Hao Zhang, Zhuangping Zhan, Zheng Jiang, Yunjie Ding 2017, 38 (5):  890-898.  DOI: 10.1016/S1872-2067(17)62826-2 Abstract ( 384 )   [Full Text(HTML)] () PDF (665KB) ( 1011 )   Two vinyl-functionalized chiral 2,2’-bis(diphenylphosphino)-1,1’-binaphthyl (BINAP) ligands, (S)-4,4’-divinyl-BINAP and (S)-5,5’-divinyl-BINAP, were successfully synthesized. Chiral BINAP-based porous organic polymers (POPs), denoted as 4-BINAP@POPs and 5-BINAP@POPs, were efficiently prepared via the copolymerization of vinyl-functionalized BINAP with divinyl benzene under solvothermal conditions. Thorough characterization using nuclear magnetic resonance spectroscopy, thermogravimetric analysis, extended X-ray absorption fine structure analysis, and high-angle annular dark-field scanning transmission electron microscopy, we confirmed that chiral BINAP groups were successfully incorporated into the structure of the materials considered to contain hierarchical pores. Ru was introduced as a catalytic species into the POPs using different synthetic routes. Systematic investigation of the resultant chiral Ru/POP catalysts for heterogeneous asymmetric hydrogenation of β-keto esters revealed their excellent chiral inducibility as well as high activity and stability. Our work thereby paves a path towards the use of advanced hierarchical porous polymers as solid chiral platforms for heterogeneous asymmetric catalysis.

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Sr-doping effects on La2O3 catalyst for oxidative coupling of methane Linna Cong, Yonghui Zhao, Shenggang Li, Yuhan Sun 2017, 38 (5):  899-907.  DOI: 10.1016/S1872-2067(17)62823-7 Abstract ( 389 )   [Full Text(HTML)] () PDF (909KB) ( 1104 )   Density-functional theory calculations were carried out to study the strontium (Sr)-doping effect on methane activation over a lanthanum-oxide (La2O3) catalyst for the oxidative coupling of methane (OCM) using the cluster model. Eight Sr-doped La2O3 cluster models were built from pure La2O3 clusters that were used previously to model the La2O3 catalyst. These form two distinct categories, namely, those without a radical character (LaSrO2(OH), La2SrO4, La3SrO5(OH), and La5SrO8(OH)) and those with a radical character (LaSrO3, La2SrO4(OH), La3SrO6, and La5SrO9). The potential-energy surface for CH4 activation to form a CH3 radical at different Sr–O and La–O pair sites on these Sr-doped La2O3 clusters was calculated to study the Sr-doping effect on the OCM catalytic activity. CH4 physisorption and chemisorption energies, and activation barriers, and CH3 desorption energies were predicted. Compared with the pure La2O3 clusters, in general, the Sr-doped La2O3 clusters are thermodynamically and kinetically more reactive with CH4. For the Sr-doped La2O3 clusters without the radical character, the Sr–O pair site is more reactive with CH4 than the La–O pair site, although a direct release of the CH3 radical is also highly endothermic as in the case of the pure La2O3 clusters. In contrast, for the Sr-doped La2O3 clusters with a radical character, the activation of CH4 at the oxygen radical site and the release of the CH3 radical are much easier. Thus, our calculations suggest that the Sr dopant prompts the OCM catalytic activity of the La2O3 catalyst by providing a highly active oxygen-radical site and by strengthening the basicity of the M–O pair site, which leads to lower CH4 activation energies and lower CH3 desorption energies.

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Synthesis of isosorbide-based polycarbonates via melt polycondensation catalyzed by quaternary ammonium ionic liquids Wei Sun, Fei Xu, Weiguo Cheng, Jian Sun, Guoqing Ning, Suojiang Zhang 2017, 38 (5):  908-917.  DOI: 10.1016/S1872-2067(17)62822-5 Abstract ( 471 )   [Full Text(HTML)] () PDF (756KB) ( 1407 )   A series of quaternary ammonium ionic liquids (ILs) were synthesized and employed as catalysts for the production of poly(isosorbide carbonate) (PIC) from diphenyl carbonate and isosorbide via a melt polycondensation process. The relationship between the anions of the ILs and the catalytic activities was investigated, and the readily-prepared IL tetraethylammonium imidazolate (TEAI) was found to exhibit the highest catalytic activity. After optimizing the reaction conditions, a PIC with a weight-average molecular weight (Mw) of 25600 g/mol was obtained, in conjunction with an isosorbide conversion of 92%. As a means of modifying the molecular flexibility and thermal properties of the PIC, poly(aliphatic diol-co-isosorbide carbonate)s (PAIC)s were successfully synthesized, again using TEAI, and polymers with Mw values ranging from 29000 to 112000 g/mol were obtained. 13C NMR analyses determined that the PAIC specimens had random microstructures, while differential scanning calorimetry demonstrated that each of the PAICs were amorphous and had glass transition temperatures ranging from 50 to 115℃. Thermogravimetric analyses found Td-5% values ranging from 316 to 332℃ for these polymers. Based on these data, it is evident that the incorporation of linear or cyclohexane-based diol repeating units changed the thermal properties of the PIC.

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Investigation of low-temperature hydrothermal stability of Cu-SAPO-34 for selective catalytic reduction of NOx with NH3 Xiao Xiang, Pengfei Wu, Yi Cao, Lei Cao, Quanyi Wang, Shutao Xu, Peng Tian, Zhongmin Liu 2017, 38 (5):  918-927.  DOI: 10.1016/S1872-2067(17)62836-5 Abstract ( 394 )   [Full Text(HTML)] () PDF (612KB) ( 947 )   The low-temperature hydrothermal stabilities of Cu-SAPO-34 samples with various Si contents and Cu loadings were systematically investigated. The NH3 oxidation activities and NH3-selective catalytic reduction (SCR) activities (mainly the low-temperature activities) of all the Cu-SAPO-34 catalysts declined after low-temperature steam treatment (LTST). These results show that the texture and acid density of Cu-SAPO-34 can be better preserved by increasing the Cu loading, although the hydrolysis of Si–O–Al bonds is inevitable. The stability of Cu ions and the stability of the SAPO framework were positively correlated at relatively low Cu loadings. However, a high Cu loading (e.g., 3.67 wt%) resulted in a significant decrease in the number of isolated Cu ions. Aggregation of CuO particles also occurred during the LTST, which accounts for the decreasing NH3 oxidation activities of the catalysts. Among the catalysts, Cu-SAPO-34 with a high Si content and medium Cu content (1.37 wt%) showed the lowest decrease in NH3-SCR because its Cu2+ content was well retained and its acid density was well preserved.

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One-step synthesis of pyruvic acid from glycerol oxidation over Pb promoted Pt/activated carbon catalysts Chen Zhang, Tao Wang, Yunjie Ding 2017, 38 (5):  928-938.  DOI: 10.1016/S1872-2067(17)62835-3 Abstract ( 768 )   [Full Text(HTML)] () PDF (1462KB) ( 991 )   One-step production of pyruvic acid through selective oxidation of glycerol was investigated using lead promoted platinum/activated carbon (Pb-Pt/AC) catalysts under mild conditions. The results of N2 physisorption, X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy revealed that the alloy phases of PtPb and PtxPb were favorable for pyruvic acid production from glycerol oxidation, whereas the Pb3(CO3)2(OH)2 and surface Pb0 species inhibited the glycerol conversion. The loading of Pb and the catalyst preparation method (including impregnation and deposition precipitation) affected the formation of different metal species. Pyruvic acid was obtained at a yield of 18.4% on a 5.0 wt% Pb-5.0 wt% Pt/AC catalyst prepared by co-deposition precipitation method and 500℃ argon treatment.

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Enhancement of the formic acid electrooxidation activity of palladium using graphene/carbon black binary carbon supports Meiying Lv, Wenpeng Li, Huiling Liu, Wenjuan Wen, Guang Dong, Jinghua Liu, Kaichen Peng 2017, 38 (5):  939-947.  DOI: 10.1016/S1872-2067(17)62834-1 Abstract ( 314 )   [Full Text(HTML)] () PDF (889KB) ( 905 )   Combinations of graphene (Gr) and carbon black (C) were employed as binary carbon supports to fabricate Pd-based electrocatalysts via one-pot co-reduction with Pd2+. The electrocatalytic performance of the resulting Pd/Gr-C catalysts during the electrooxidation of formic acid was assessed. A Pd/Gr0.3C0.7 (Gr oxide:C = 3:7, based on the precursor mass ratio) electrocatalyst exhibited better catalytic performance than both Pd/C and Pd/Gr catalysts. The current density generated by the Pd/Gr0.3C0.7 catalyst was as high as 102.14 mA mgPd-1, a value that is approximately 3 times that obtained from the Pd/C (34.40 mA mgPd-1) and 2.6 times that of the Pd/Gr material (38.50 mA mgPd-1). The anodic peak potential of the Pd/Gr0.3C0.7 was 120 mV more negative than that of the Pd/C and 70 mV more negative than that of the Pd/Gr. Scanning electron microscopy images indicated that the spherical C particles accumulated on the wrinkled graphene surfaces to form C cluster/Gr hybrids having three-dimensional nanostructures. X-ray photoelectron spectroscopy data confirmed the interaction between the Pd metal and the binary Gr-C support. The Pd/Gr0.3C0.7 also exhibited high stability, and so is a promising candidate for the fabrication of anodes for direct formic acid fuel cells. This work demonstrates a simple and cost-effective method for improving the performance of Pd-based electrocatalysts, which should have potential industrial applications.