Catalytic Activity of Ceria-Zirconia Nanostructured Materials Prepared via Reversed Microemulsion Method

Single-phase homogeneous Ce1-x ZrxO2 solid versed microemulsion method. The structural properties solutions with various compositions were synthesized using the reand performance of Ce1- xZrxO2 were studied using XRD, BET, SEM, HRTEM, TPR and CO oxidation measurements. The results show that in the range of x = 0.4 - 0.5 and x = 0.6 - 1.0, the solid solutions posses the cubic and the tetragonal phase structure, respectively, Solids obtained by the reversed microemulsion method were more homogeneous on the whole range of composition, XRD investigations of the prepared materials did not show segregation of cerium or zirconium oxides, Highly uniform nanosize solid solution particles of ceria-zirconia with high specific area （146.7 m^2·g^-1） were attained under the conditions of this study. The TPR results and CO oxidation measurements indicate that the performance of the CeO2-ZrO2 mixed oxides is strongly related to the composition and structure of the oxides. Enhancement of the activity was found for the catalyst prepared by reversed microemulsion method as compared to the sample prepared by sol-gel method.

Preparation and Characterization of CeO_2-ZrO_2 Solid Solution Ultrafine Particles Using Reversed Microemulsion

Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is （146.7 m^2·g^-1）, which is higher than the surface area for sol-gel prepared sample （59.5m^2·g^-1）. HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.

Selenium Nanoparticles Prepared from Reverse Microemulsion Process

Selenium nanoparticles were prepared by a reverse microemulsion system. Sodium selenosulfate was used as selenium source. The results showed that hydrochloric acid concentration and reaction temperature had great influence on the morphology of products. The crystalline selenium nanowires and amorphous selenium nanorods were obtained in given condition.

Reverse Microemulsion Synthesis and Characterization of Pd-Ag Bimetallic Alloy Catalysts Supported on Al_2O_3 for Acetylene Hydrogenation

Pd-Ag bimetallic alloy nanoparticles were synthesized by the reverse microemulsion method, and then deposited on A1203 to form the supported catalyst. The nanoparticles of Pd-Ag and Pd-Ag/AI203 samples were characterized by UV/ Vis, HRTEM, EDX, XRD, and XPS. The test results indicated that Pd-Ag bimetallic alloy nanoparticles with a size of about 2 nm and a face-centered cubic （fcc） structure were formed in the measured area of microemulsion. The growth of nanopar- ticles was effectively limited within the droplet of micoremulsion. TEM image exhibited that the Pd-Ag alloy nanoparticles were well-dispersed on the A1203 support. The catalytic performance of various catalysts for selective hydrogenation of acetylene showed that a higher acetylene conversion and selectivity to ethylene upon acetylene hydrogenation was achieved on a nano-sized Pd-Ag bimetallic catalyst with a Pd/Ag alloy supported molar ratio of 1：1.5.

Preparation of Ni nanoparticles plating by electrodeposition using reverse microemulsion as template

Ni nanoparticles plating was prepared in reverse microemulsion. The deposition was carried out through the Brownian motion of water pools in the reverse microemulsion and the adsorption of water pools on the electrode surface. Effects of electrolytic parameters on the size of Ni particles were studied. The performances of hydrogen evolution and hydrogen storage of the Ni nanoparticles plating electrode were also investigated. The results indicate that the size of Ni nanoparticles decreases with the increase of Ni2+ concentration and the decrease of current density. The electrochemical activity of Ni nanoparticles plating electrode is much higher than that of bulk Ni electrode.

Facile Preparation and Formation Mechanism of Uniform Silver Nanoparticles Using OP-10 as Emulsifier in Reverse Microemulsion

Using the polymerizable hydrophobic styrene monomer as the dispersion medium and the traditional nonionic surfactant OP-10 as emulsifier, stable silver nanoparticles of narrow size distribution were prepared by a reverse （w/o） microemulsion method. The powder X-ray diffraction （XRD） pattern indicated that the obtained silver nanoparticles were of face-centered cubic structure. The results of the transmission electron microscopy （TEM） show that the final silver nanoparticles are of spherical structure with an average diameter of 15.2 nm and of a Gaussian distribution. The internal high-ordered structure of silver nanoparticles was characterized by the field-emission high-resolution transmission electron microscopy （FEHRTEM）, indicating that the silver is monocrystalline and it has only one nucleation site during the formation process of a nanoparticle. The time-resolved UV-visible absorption spectra was used to monitor the process of the reaction in situ. The results show that the concentration of silver nanoparticles increases but the size changes little and the morphology transforms from obvious ellipsoidal shape to nearly spherical shape during the process. The experimental results indicate that the droplets’ dynamic exchange which is closely related to the nature of surfactant film is the control factor of the kinetics. The dynamic exchange mechanism of silver nanoparticle formation is proposed to involve continual encounter of two separate droplets forming transient fused dimer in which the chemical reaction occurs followed by re-separation without combination. Attributed to the dual role of surfactant in the nanoparticle formation, tailored nanoparticles can be successfully synthesized in control in the premise of a certain stability of reverse microemulsion.

Poly(ethylene oxide) Solubilization in Reverse Microemulsion:Conductivity and UV-Vis Spectra Studies

The effect of poly (ethylene oxide) (PEO) on the w/o microemulsion is studied. The addition of PEO induces a decrease of attractive interaction between droplets in reverse microemulsion. Due to the absence of interaction between cationic surfactant and neutral polymer, the polymer molecules are forced into the interior of water core, avoiding the interfacial region.

Electrochemical synthesis of polyaniline in reverse microemulsion

The electro-polymerization behavior of aniline in reverse(W/O) microemulsion was investigated. The experiment results show that the cyclic voltammetry polymerization behavior of aniline in W/O microemulsion is different from that in aqueous solution remarkably. With the increase of scan cycle, the oxidation potential shifts positively and the reduction potential shifts negatively, i.e., the redox potential difference increases. H+ apparent concentration affects the aniline polymerization evidently. When H+ concentration is lower than 0.08 mol/L, the electro-polymerization of aniline is difficult. With the increase of H+ concentration, the polymerization current of aniline increases gradually. Only when H+ concentration is high enough(0.5 mol/L), aniline can be well electro-polymerized. Moreover, under the same condition, the aniline polymerization current in W/O microemulsion is higher than that in aqueous solution. The scanning electron microscopy image shows that the deposited polyaniline(PANI) has uniform fiber morphology with diameter of about 100 nm. Further study result suggests that the electrochemical activity of the PANI in HCl is similar to that of the PANI prepared in aqueous solution.

Study on hexaaluminate MnLaAl_(11)O_(19-δ) catalyst for catalytic combustive reaction of dimethyl ether as a new fuel

Study on catalytic combustive reaction of dimethyl ether as a new fuel was presented.Hexaaluminate catalysts were used to reduce ignition temperature so that dimethyl ether completely combusted at low temperature.Hexaaluminate catalysts MnLaAl_(11)O_(19-δ)were prepared by reverse microemulsion method.Crystalline phase and structure of the catalyst were analysed by means of TG-DTA,XRD and BET.The results show that the hexaalunminate is of magnetoplumbite structure when La is taken as mirror plane cation.Hexaalunminate phase is formed slowly via 1050℃calcined for 4 h and it can keep hexaaluminate phase and high surface area of 48 m^(2)·g^(-1)even calcined at 1200℃for 2 h.Catalytic activity of MnLaAl_(11)O_(19-δ)was tested in combustion reaction of dimethyl ether.It shows that hexaaluminate is of high activity with T_(10%)at 170℃and almost 100%conversion at 370℃.

Effect of Preparation Methods on Activation of Catalysts BaNi0.2Mn0.8Al11O19-δ for Dimethyl Ether Combustion

Catalytic combustion of dimethyl ether （DME） over hexaaluminate catalyst BaNi0.2Mn0.8Al11O19-δ has been investigated. The catalysts were prepared with the sol-gel method and reverse microemulsion method respectively and characterized by thermogravimetry-differential thermal analysis, X-ray diffraction and transimission electron microscope. It was found that the formation of Mn, Ni modified hexaaluminate was a relatively slow process via two solid state reactions and spinel structure was a transition phase. At the same calcined temperature and time, the catalyst prepared with the reverse microemulsion method could form the hexaaluminate phase more easily than that prepared with the sol-gel method. The catalyst BaNi0.2Mn0.8Al11O19-δ prepared with the reverse micro-emulsion method appeared a plate-like morphology, while it appeared a needle-like morphology when using the sol-gel method. The catalytic activities of catalysts BaNi0.2Mn0.8Al11O19-δ prepared with two different methods for DME combustion were tested. It showed that catalyst prepared with the reverse microemulsion method had better catalytic activity, i.e. T10% of DME had decreased by 45℃, about 90% conversion of diemthyl ether at 380℃.

Effect of Preparation Method on Surface Area and Crystalline Form of CeO_2-ZrO_2 Solid Solution

The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m^2·g^(-1), and that calcined at 900 ℃ for 6 h is 88 m^2·g^(-1). The sample with tetragonal symmetry Ce_(0.5)Zr_(0.5)O_2 phase has a higher stability.

Electrochemical capacitance of nanostructured ruthenium- doped tin oxide Sn1-xRuxO2 by the microemulsion method

Synthesis of nanostructured Ru-doped SnO2 was successfully carried out using the reverse microemulsion method. The phase purity and the crystallite size were analyzed by XRD. The surface morphology and the microstructure of synthesized nanoparticles were analyzed by SEM and TEM. The vibration mode of nanoparticles was investigated using FTIR and Raman studies. The electrochemical behavior of the Ru- doped SnO2 electrode was evaluated in a 0.1 mol/L Na2SO4 solution using cyclic voltammetry. The 5% Ru-doped SnO2 electrode exhibited a high specific capacitance of 535.6 Fig at a scan rate 20 mV/s, possessing good conductivity as well as the electro- cycling stability. The Ru-doped SnO2 composite shows excellent electrochemical properties, suggesting that this composite is a promising material for supercapacitors.