An effective electrocatalyst for ethanol oxidation: Pt-modified IrCu alloy nanoparticle

There is a growing interest in ethanol oxidation electrochemistry as it plays an important role in renewable energy technologies. The goal of this work was to develop active multifunctional catalyst materials for ethanol oxidation. Here, a carbon-supported Pt-modified IrCu alloy electrocatalyst (Pt–IrCu/C) was prepared by a two-step method. X-ray diffraction and transmission electron microscope showed that the Pt–IrCu/C has a two-phase structure: Pt nanoparticle-modified IrCu alloy. The Pt–IrCu/C catalyst was found to have not only a large electrochemically active specific area (S _EAS) but also good CO oxidation ability for oxidation of ethanol compared to the commercial Pt/C electrocatalyst using cyclic voltammetry. Furthermore, the Pt current density of Pt–IrCu/C was more than 1.6 times as high as that of Pt/C for ethanol oxidation. The Pt–IrCu/C catalyst also exhibited more efficient usage of Pt and enhanced the stability of ethanol electro-oxidation compared with a Pt/C catalyst.     

原子层沉积技术沉积的FeOx包裹层显著提高Pd/C催化剂在甲酸分解放氢反应中的催化活性

Hydrogen generation from formic acid (FA) has received significant attention.The challenge is to obtain a highly active catalyst under mild conditions for practical applications.Here atomic layer deposition (ALD) of FeO_x was performed to deposit an ultrathin oxide coating layer to a Pd/C catalyst,therein the FeO_x coverage was precisely controlled by ALD cycles.Transmission electron microscopy and powder X-ray diffraction measurements suggest that the FeO_x coating layer improved the thermal stability of Pd nanoparticles (NPs).X-ray photoelectron spectroscopy measurement showed that deposition of FeO_x on the Pd NPs caused a positive shift of Pd3d binding energy.In the FA dehydrogenation reaction,the ultrathin FeO_x layer on the Pd/C could considerably improve the catalytic activity,and Pd/C coated with 8 cycles of FeO_x showed an optimized activity with turnover frequency being about 2 times higher than the uncoated one.The improved activities were in a volcanoshape as a function of the number of FeO_x ALD cycles,indicating the coverage of FeO_x is critical for the optimized activity.In summary,simultaneous improvements of activity and thermal stability of Pd/C catalyst by ultra-thin FeO_x overlayer suggest to be an effective way to design active catalysts for the FA dehydrogenation reaction.     

Studies on the preparation and ethanol gas sensing properties of spinel Zn0.6Mn0.4Fe2O4 nanomaterials

Zn_1−xMn_xFe₂O₄ (x = 0, 0.2 and 0.4) nanomaterials were synthesized by sol–gel citrate method and studied structural and gas sensing properties. The structural characteristics of synthesized nanomaterials were studied by X-ray diffraction measurement (XRD) and transmission electron microscope (TEM). The results revealed that the particle size is in the range of 30–35 nm for Mn–Zn ferrite with good crystallinity. The gas sensing properties were studied towards reducing gases like LPG, CH_4, CO and ethanol and it is observed that Mn–Zn ferrite shows high response to ethanol at relatively lower operating temperature. The Zn_0.6Mn_0.4Fe₂O₄ nanomaterial shows better sensitivity towards ethanol at an operating temperature 300 °C. Incorporation of 1.5 wt.% Pd improved the sensitivity, selectivity, response time and reduced the operating temperature from 300 °C to 230 °C for ethanol sensor. The response time of 200 ppm ethanol in air is about 10s.     

Effect of the degree of alloying of PtRu/C (1:1) catalysts on ethanol oxidation

The effect of alloying degree on the ethanol oxidation activity of a PtRu/C catalyst with a Pt/Ru atomic ratio of 1:1 was investigated by measurements in a half-cell and in a single direct ethanol fuel cell. The increase of the amount of Ru alloyed from one third to two thirds of the total Ru content in the catalyst clearly resulted in a decrease of the ethanol oxidation activity. As the amount of the highly active hydrous ruthenium oxide was near the same, the lower activity of the PtRu/C catalyst with higher alloying degree was mainly ascribed to the presence of an excessive number of Ru atoms around Pt active sites, hindering ethanol adsorption on Pt sites. The reduced ethanol adsorption could be also related to the decreased Pt–Pt bond distance and to the electronic effects by alloying.     

Zn-Y/BEA上乙醇一步法制1，}3-丁二烯的反应机理及优异催化剂筛选

随着beta分子筛负载双金属催化剂的开发,乙醇一步法制1,3-丁二烯}取得了突破性进展. 然而,从乙醇到丁二烯的反应机理复杂,尚未完全阐明,也缺乏基于中心金属原子的催化剂筛选. 本文采用密度泛函理论计算方法,系统地研究了乙醇在Zn-Y/BEA催化剂上一步法制丁二烯的机理. 结果表明,乙醇脱氢更倾向于在Zn位点进行,决速步骤的反应热仅为0.77 eV;羟醇缩合生成丁二烯更倾向于在Y位点进行,决速步骤的反应热仅为0.69 eV. 基于所揭示的反应机理,选择了六种元素代替Y来筛选用于该反应的Zn-M/BEA(M=Sn、Nb、Ta、Hf、Zr、Ti)的优良组合. 结果表明,与其他六种催化剂相比,Zn-Y/BEA仍是最优选的催化剂,Zn-Zr/BEA、Zn-Ti/BEA和 Zn-Sn/BEA也是乙醇转化为丁二烯的可行催化剂. 本工作不仅揭示了Zn-Y/BEA催化乙醇一步法制丁二烯的反应机理,而且为该反应提供了其他可能的催化剂选择.     

Hydrogenation of p-chloronitrobenzene on Ni–B Nanometal Catalysts

A series of Ni–B catalysts were prepared by mixing nickel acetate in 50% ethanol/water or methanol/water solution. The solution of sodium borohydride (1 M) in excess amount to nickel was then added dropwise into the mixture to ensure full reduction of nickel cations. The mol ratio of boron to nickel in mother solution was 3 to 1. The effects of preparation conditions such as temperature, stirring speed, and sheltering gas on the particle size, surface compositions, electronic states of surface atoms and catalytic activities of the Ni–B catalysts were studied. Ranel nickel catalyst was included for comparison. These catalysts were characterized by N₂ sorption, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalysts were tested for liquid phase hydrogenation of p-chloronitrobenzene. All of the catalysts prepared in this study had nanosized particles. The preparation condition has significant influence on the particle size and surface compositions of the catalyst. The Ni–B catalyst was passivated by boron; therefore it was more stable than Raney nickel and did not catch fire after exposure to air. The catalysts prepared under N₂ flow could suppress the oxidation of Ni by the dissolved oxygen in water and had metallic state of nickel. The catalyst prepared with vigorous stirring at 25°C under N₂ stream yielded the smallest particles and resulted in the highest activity. It was much more active than the Raney nickel catalyst. The reaction condition also has pronounced effect on the hydrogenation activity. Using methanol as the reaction solvent increased p-chloronitrobenzene conversion to a large extent, compared to that using ethanol as the reaction medium. The selectivity of main product (p-chloroaniline) was greater than 99% on all of the Ni–B catalysts.     

Modeling Sorption Behavior for Ethanol/Water Mixtures in a Cross-linked Polydimethylsiloxane Membrane Using the Flory-Huggins Equation

The sorption behaviors of aqueous ethanol solutions in a polydimethylsiloxane (PDMS) membrane at 25°C were investigated in this study. The sorption isotherms for the ethanol and water binary mixtures were experimentally determined. The water uptake reached a maximum at a concentration of 80 wt% ethanol, and the partial water uptakes were even higher than the pure water solubility for 10–95 wt% ethanol solutions in the PDMS membrane, which implies the presence of a strong synergistic effect due to the ethanol copermeant. The Flory-Huggins equation was utilized to predict the sorption levels at various ethanol/water compositions. The binary Flory-Huggins interaction parameters obtained from pure solvent sorption experiments (χ_iM ) and the ethanol/water vapor liquid equilibrium data (χ ₁₂) were used in the construction of the model for predicting the partial penetrant solubilities. Using constant χ_ij parameters could not render satisfactory predictions; therefore, concentration-dependent expressions for either χ ₁₂ or χ_iM were employed to improve the prediction power. We found that constant or concentration dependent χ ₁₂ parameters had little impact on the predicted sorption, whereas the modified concentration-dependent χ_iM values greatly improved the modeling precision.     

Green approaches via nanocatalysis with nanoporous materials: Functionalization of mesoporous materials for single site catalysis

Among the various green keys, catalysis, especially using heterogeneous catalysts, has been powerfully applied to achieve greener chemical processes. Here are presented nanoporous materials which have mesoporosity with the functional groups on the inner pore walls. The materials were synthesized via a rather greener process, such as microwave synthesis, and over these nanocatalysts some of the green chemical reactions were carried out with high activities and selectivities. Cobalt species has been successfully functionalized and stabilized as a Co(III) complex onto SBA-15 support and proven to be an active catalyst in alkylaromatic oxidation with molecular oxygen, styrene epoxidation with tert-butyl hydroperoxide (TBHP), and allylic oxidation of cycloolefins with H₂O₂. Short-channeled amino-functionalized SBA-15 catalyst with hexagonal plate morphology was synthesized directly by using microwave synthesis from the co-condensation of aminopropyl triethoxysilane (APTES) and sodium metasilicate under a strong acidic condition. The catalyst showed high catalytic activity in liquid-phase Knoevenagel condensation reactions, due to easy diffusion and mass transfer of substrates into the short mesopore channel. The HO₃S–SBA-15 was prepared by grafting of mercaptopropyl trimethoxysilane onto the calcined mesoporous silica surface and subsequently oxidized with H₂O₂. The resulting catalyst was applied as a Bronsted solid-acid catalyst for the esterification of oleic acid with methanol.     

Hydrogen production over a commercial Pd/Al2O3 catalyst for fuel cell utilization

In order to produce a hydrogen stream for fuel cell utilization, the study of the ethanol steam reforming process over an alumina supported palladium commercial catalyst was carried out. The effect of the reaction temperature, the H₂O/C₂H₆O molar ratios and the contact time on catalytic activity and stability was studied. It was found that even at very low temperature values complete ethanol conversion was possible. Hydrogen selectivities up to 98% were obtained at temperature values close to 625 °C. It was also observed that for different reactant molar ratios carbon monoxide concentration exhibits a minimum at a temperature value close to 450 °C. Furthermore, carbon formation was found to be negligible even for H₂O/C₂H₆O molar ratios equal to the stoichiometric one. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15–21, 2002     

Effect of ferroelectric polarization on the adsorption and reaction of ethanol on BaTiO3

The effect of ferroelectric polarization on the adsorption and reaction of ethanol on BaTiO₃ was studied using temperature-programmed desorption (TPD). Consistent with previous studies for methanol, the reactive sticking coefficient for ethanol on the surfaces of the ferroelectric, tetragonal phase of BaTiO₃ was found to be dependent on the orientation of the ferroelectric domains with a higher sticking coefficient on the c⁺ surface relative to the c⁻ surface. TPD peak shapes and the relative product yields were also found to be polarization dependent suggesting that ferroelectric polarization may affect the intrinsic reactivity of the surface.     

Ultrasound-assisted lipase-catalyzed transesterification of soybean oil in organic solvent system

This work reports the transesterification of soybean oil with ethanol using two commercial immobilized lipases under the influence of ultrasound irradiation. The experiments were performed in an ultrasonic water bath, following a sequence of experimental designs to assess the effects of temperature, enzyme and water concentrations, oil to ethanol molar ratio and output irradiation power on the reaction yield. Results show that ultrasound-assisted lipase-catalyzed transesterification of soybean oil with ethanol might be a potential alternative route to conventional alkali-catalyzed method, as high reaction yields (∼90 wt.%) were obtained at mild irradiation power supply (∼100 W), and temperature (60 °C) in a relatively short reaction time, 4 h, using Lipozyme RM IM as catalyst. The repeated use of the catalyst under the optimum experimental condition resulted in a decay in both enzyme activity and product conversion after two cycles. The use of Novozym 435 led to lower conversions (about 57%) but the enzyme activity was stable after eight cycles of use, showing, however, a reduction in product conversion after the forth cycle.     

The study of deNOx catalyst in low temperature using nano-sized supports

The present study pertains to a vanadium/titania-based catalyst for removing nitrogen oxides at a relatively low temperature window. More specially, the present study relates to a vanadium/titania-based catalyst containing VO_x (x < 2.5) and having excellent ability to remove nitrogen oxides at a wide temperature window, particularly at a relatively low temperature window and a process for removing nitrogen oxides using the same. In this study, various TiO₂ supports have been tested to determine the role of support. Raw TiO₂ were examined a variety of physical properties. Also comparing with commercial V₂O₅/TiO₂ catalyst, the activity of various VO_x (x < 2.5)/TiO₂ in this study have quite different values.To find the source of lattice oxygen in vanadium oxides, the effect of calcination conditions on the removal efficiency of nitrogen oxides was examined. When nitrogen instead of air was introduced as a balance gas in calcination step, the activity of catalysts in this study was not changed. That may indicate the source of lattice oxygen in vanadium oxides as that of TiO₂. The results of X-ray photoelectron spectroscope (XPS) revealed that after vanadium oxides loaded the support, TiO₂ was reduced to Ti₂O₃, etc. In the test of calcination temperature of a variety of vanadium/titania-based catalysts, it has been found that TiO₂ supports affects the optimal calcination temperature, indicating that the difference of crystal structure, defect and binding energy in TiO₂ may make inherent VO_x (x < 2.5)/V₂O₅ molar ratios, respectively. Its ratio seems to be an index of activity.     

In Vivo3D LocalizedC Spectroscopy Using Modified INEPT and DEPT

The 3D localized¹³C spectroscopy methods LINEPT and LODEPT, which are modifications of INEPT and DEPT, are proposed. As long as a¹³C inversion pulse (180-degree pulse) is applied at 1/(4J) before the proton echo time in LINEPT and a¹³C excitation pulse (90-degree pulse) is applied at 1/(2J) before the proton echo time in LODEPT, the proton echo time can be set to any value longer than 1/(2J) in LINEPT and longer than 1/Jin LODEPT. As a result, the proton and the¹³C pulses can be applied separately and these proton pulses can be made slice-selective pulses. These localization features of LINEPT and LODEPT were evaluated using a phantom consisting of a cylinder filled with ethanol placed inside another cylinder filled with oil, and localized ethanol spectra could be obtained.In vivo3D localized¹³C spectra from the brain of a monkey could be obtained using decoupled LINEPT, and glutamate C-4 appeared directly after the administration of glucose C-1, followed by the appearance of glutamate C-2, C-3 and glutamine C-2, C-3, C-4.     

Investigation of oxide catalysts activity in the NOx neutralisation with organic reductants

Temperature-programmed desorption of NO (TPD) and temperature-programmed reduction of NO by propene and ethanol (TPSR) over the catalyst with redox properties and the structure of spinels - Co₃O₄ and CoFe₂O₄ - were investigated.The TPD experiments can determine the temperature range in which the deNO_x proceeds and provide information about the heat of adsorption of NO on the surface of catalysts. The values of the adsorption heat are much higher in the case of the catalyst with weaker redox properties (CoFe₂O₄), because of stronger bonds between the adsorbate and the surface of catalyst. The TPD and TPSR experiments show that ethyl alcohol is a more active reductant in the deNO_x process than propene. The maximum of NO_x conversion is higher with ethyl alcohol used as a reductant in both cases of investigated catalysts. Moreover, the temperature of the maximum degree of NO_x reduction is lower in the case of alcohol used as an reductant. Co₃O₄ is a more active and suitable catalyst for the deNO_x process than CoFe₂O₄.     

Ag-deposited silica-coated Fe3O4 magnetic nanoparticles catalyzed reduction of p-nitrophenol

In this paper, a novel approach was successfully developed for advanced catalyst Ag-deposited silica-coated Fe₃O₄ magnetic nanoparticles, which possess a silica coated magnetic core and growth active silver nanoparticles on the outer shell using n-butylamine as the reductant of AgNO₃ in ethanol. The as-synthesized nanoparticles have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectra (FT-IR), vibration sample magnetometer (VSM), and have been exploited as a solid phase catalyst for the reduction of p-nitrophenol in the presence of NaBH₄ by UV-vis spectrophotometry. The obtained products exhibited monodisperse and bifunctional with high magnetization and excellent catalytic activity towards p-nitrophenol reduction. As a result, the as-obtained nanoparticles showed high performance in catalytic reduction of p-nitrophenol to p-aminophenol with conversion of 95% within 14 min in the presence of an excess amount of NaBH₄, convenient magnetic separability, as well as remained activity after recycled more than 6 times. The Fe₃O₄@SiO₂-Ag functional nanostructure could hold great promise for various catalytic reactions.     

A study of the effect of different catalysts for the efficient CVD growth of carbon nanotubes on silicon substrates

We report on the identification of efficient combinations of catalyst, carbon feedstock, and temperature for the ethanol chemical vapour deposition (CVD) growth of single-wall carbon nanotubes (SWCNTs) onto silicon substrates.Different catalyst preparations, based on organometallic salts (Co, Fe, Mo, Ni acetate, and bimetallic mixtures), have been spin coated onto thermally grown silicon dioxide on silicon chips to perform tests in a temperature range between 500 and 900 °C.The samples have been then characterized by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy. Assuming the growth of high-quality isolated nanotubes as target, the ratio in Raman spectra between the intensity of the G peak and of the D peak has been used as the main parameter to evaluate the performance of the catalytic process. A comparison made for both single metals and bimetallic mixtures points out best conditions to achieve efficient CVD growth of SWCNTs.     

三维金属有机骨架/石墨烯水凝胶均相降解纤维素为小分子酸的研究

通过在三维还原氧化石墨烯孔径中原位生长ZIF-8纳米粒子,制备了三维金属有机骨架/石墨烯催化剂.这种ZIF-8/rGO纳米复合材料同时具有介孔和微孔,并且拥有高比表面积和大量催化位点,是生物质转化的理想催化剂.将纤维素溶解于氢氧化钠水溶液中,在水热条件下,使用这种催化剂,纤维素可以被充分降解转化.纤维素转化率可以达到100%,其主要产物是甲酸,产率最高可达93.66%.催化剂还可以被回收,重复使用依然具有很好的催化效果.     

Synergistic effects of ultrasonication and ethanol washing in controlling the stoichiometry,phase-purity and morphology of rare-earth doped ceria nanoparticles

Over a period of last thirty years, use of ethanol has been historically reported for obtaining nanopowders with low agglomeration for various oxide systems. In addition to these benefits, we show for the first time that treatments in ethanol medium coupled with an ultrasonication step can impart crucial additional advantages in controlling the phase purity and stoichiometry/composition for such systems. This is an important issue especially for any complex multicationic oxide nanoparticles system and hence we selected one of the most popular catalyst systems of doped-ceria (CeO₂) nanoparticles with very high (50%) level of rare-earth (lanthanum) doping for this case study. The effect of an ultrasonication combined ethanol treatment was compared with the other solvent media (pure water and ethanol) without ultrasonication. The underlying mechanism for this process involves lowering the deprotonation rate in ethanol medium which eventually reduces the condensation of the individual metal oxides while the ultrasonication ensures the reproducibility of the synthesis by providing a homogeneous colloidal solution for each washing stages. This novel modification in synthesis of nanoparticles aims to provide meaningful solutions in optimising the phase, composition and morphology of multicationic complex system of nanocrystals.     

Synthesis and properties of magnetic and luminescent Fe3O4/SiO2/Dye/SiO2 nanoparticles

A simple and reproducible method was developed to synthesize a novel class of Fe₃O₄/SiO₂/dye/SiO₂ composite nanoparticles. As promising candidates for use in bioassays, the obtained nanoparticles have an average diameter of 30 nm, and the thickness of the outer shell of silica could be tuned by changing the concentration of the silicon precursor tetraethyl orthosilicate during the synthesis. These multifunctional nanoparticles were found to be highly luminescent, photostable and superparamagnetic. The luminescence intensity of the nanoparticles was increased as the dye concentration was increased in the preparation process. The color of the luminescence was successfully tuned by incorporating different dyes into the nanoparticles. The measurements of the emission spectra indicated that relative to the dye molecules dissolved in ethanol, the emission of the dye-doped nanoparticles exhibited either a red shift or a blue shift, to which a tentative explanation was given.     

合成Pb(OH)2/rGO催化剂用于催化转化糖为乳酸

Pb²⁺离子可以作为高效的催化剂用于降解糖为乳酸, 但是为了降低暴露Pb²⁺离子于环境中的风险,最好的办法是把铅固定在一个固体催化剂上．报道了一个简单的制备Pb(PbO₂)/石墨烯复合固体催化剂的方法,可以得到石墨烯负载的纳米铅催化剂,铅颗粒的尺寸在2～5 nm．获得的催化剂可以在水中用于降解葡萄糖、果糖甚至纤维素,产物主要为乳酸．对于果糖、乳酸的产率为58.7% (433 K,2.5 MPa N₂);当直接使用纤维素为原料,无额外酸、碱催化剂时,乳酸的产率可以达到31.7%.