We describe here the results of a high throughput screening study for direct methanol fuel cell (DMFC) anode catalysts consisting of new elemental combinations with an optical high-throughput screening method, which allows the quantitative evaluation of the electrochemical activity of catalysts. The method is based on the fluorescence of protonated quinine generated during electrooxidation of methanol. The high-throughput screening included noble-metal free binary and ternary mixed oxides of the elements Al, Co, Cr, Cu, Fe, Mn, Mo, Nb, Ni, Ta, Ti, Zn, and Zr in the oxidized form as well as after prior reduction in hydrogen. In addition 318 ternary and quaternary Pt-containing materials composed out of the mixed oxides of Bi, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, La, Mn, Mo, Nb, Nd, Ni, Pr, Sb, Sn, Ta, Te, Ti, V, Zn, and Zr with a molar Pt-ratio of 10% and 30% were screened. Validation and long time experiments of the hits were performed by cyclovoltammetry (CV). The microstructural stability of the electrode preparations of the lead compositions was studied by X-ray diffraction (XRD) pattern analysis.

We describe here the development of an optical high-throughput screening method for direct methanol fuel cell catalysts based on the fluorescence of protonated quinine generated during electro-oxidation of methanol. The design of the working electrode allows the parallel quantification of the fluorescence development for up to 60 materials. For the preparation of the working electrode a coating routine has been developed, which allows the use of sol–gel derived materials. Due to the required stability of the electrode catalysts towards the acidic polymer membrane, a fast optical pre-screening method for acid stable materials has been developed. The electrochemical high-throughput system has been validated with Pt-Ru catalysts. Automation of data acquisition and data processing led to a fast and reliable high-throughput screening setup.

The influence of different dopants in varying contents on the activity and selectivity of Ni-based methanation catalysts under proton exchange membrane fuel cell (PEMFC) relevant conditions (hydrogen-rich gas reformate with low concentrations of CO and excess CO2) Was investigated. The modification of Ni100Ox, with 2.2 mol% of Re resulted in a catalyst highly inactive for both the methanation of CO and CO2 while the addition of Zr led to an enhanced CO and CO2 methanation activity. Further modification of Zr10Ni90Ox with small amounts of Re caused a drastically decreased reactivity towards the undesired hydrogenation of CO2 while that for CO was practically unchanged. Solo methanation experiments unambiguously reveal that this increase in selectivity is based on a loss of the intrinsic CO2 reactivity and not necessarily associated with any competition for active sites between the different kinds of carbon oxides. A detailed study of the impact of the compositional variations on structural and chemical properties was performed using nitrogen physisorption, hydrogen chemisorption, temperature-programmed reduction (TPR), temperature-programmed desorption experiments of (CO2 KO2 TPD), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) as well as TEM. As a part of the catalytically active Ni particles, Re changes the surface of the catalyst resulting in drastically altered catalytic properties while Zr or the Ni-ZrO2 interfacial region seems to play a decisive role in the activation of the CO molecule. (C) 2009 Elsevier B.V. All rights reserved.

High-throughput synthesis and screening techniques were used in the search for and optimization of new autoreduction catalysts for the CO2 reforming of methane. Diverse libraries had been synthesized via three different modified sol-gel methods using a synthesis robot and library design software. The catalyst libraries were screened for catalytic activity and stability in a simple high-throughput reactor system at 600 degrees C connected to a micro-gas chromatograph for product analysis. During generations I and 2, more than 5000 highly diverse mixed oxides were tested for potential catalytic activity. Ni10Ce90Ox demonstrated effective activity and stability among nonprecious metal catalysts without a prereduction step. In a conventional study, two advantages (i.e., rapid startup operation and high coking resistance) of Ni10Ce90Ox were noted relative to the well-known Ni/Al2O3, but deactivation was recognized. To reduce deactivation of Ni10Ce90Ox, catalyst libraries with additional dopants were prepared and examined during generations 3 and 4. Among these, (Al-5, Al-15, Zr-15)Ni10Ce90-yOx, in which metal nitrate was used as a dopant precursor, and (Al-15, Zr-5, Zr-15)Ni10Ce90-yOx, in which metal alkoxide was used, exhibited comparable activity and strongly reduced deactivation compared with Ni10Ce90Ox. Good performance of the best new catalysts, particularly Al15Ni10Ce75Ox, in which aluminium alkoxide was used as a dopant precursor, and Zr15Ni10Ce75Ox, in which zirconium dinitrate oxide was used, was found in high-throughput studies and confirmed in conventional experiments. (c) 2005 Elsevier Inc. All rights reserved.

Laser-interference structuring of sol–gel films without organic photopolymerization provides a single-step method for the production of periodic surface structures (see Figure) in titania–silica mixed-oxide films. The dependency of the structure depth and homogeneity, measured by white-light interferometry, on process parameters such as laser fluence and number of laser pulses has been evaluated. A mechanism for structure formation is proposed.

The details of a simple high-throughput reactor, developed for primary screening of catalyst libraries, are described with the special application of screening by MS. All elements of the reactor are addressed individually. The use of the reactor is demonstrated with a model study of oxidative dehydrogenation of butane. 200 mixed oxides based on silica, titania, zirconia and alumina have been evaluated in a single high-throughput experiment (HTE) and a procedure for identification of promising candidates is outlined. Conventional experiments have been used to confirm, that highly selective catalysts as well as materials catalyzing total oxidation can be reliably distinguished by the type of HTE described here.

The extent and effects of leaching of amorphous microporous and mesoporous V- and Ti-containing silica catalysts during selective oxidation reactions with t-butyl hydroperoxide and hydrogen peroxide have been investigated under aqueous and water free reaction conditions. Nanoparticles of catalyst were found to obscure the analysis of the nature of the reactions. These particles, present in all experiments, cannot be removed by filtration or centrifuging and falsely contribute to apparent leaching. With the V-containing materials leaching leads to homogeneous V-species, which at least contribute, in all cases studied, to the overall reactivity. True leaching contributions are dependent on solvent, substrate and oxidant, and therefore, cannot be generalized. With the Ti-containing catalysts leaching is strongly dependent on reaction conditions.

One should not underestimate the capability of the combinatorial method in solid-state chemistry; this is the opinion of the author. Combinatorial chemistry can provide a large number of new compounds, but once the components that are interesting for a certain application have been successfully selected, the techniques of conventional catalysis and materials research are required. The strengths of conventional chemistry lie in the optimization, systematic modification, and improvement of new lead structures. In contrast, discovery is the potential strength of combinatorial chemistry. Careful design is most important for the synthesis of useful libraries, since the diversity of the periodic table is much too large to be accessed comprehensively or systematically by such large libraries.

Poly(vinylpyrrolidone) (PVP)-stabilized Pt clusters (1.4 nm average particle size) were embedded in an amorphous microporous titania-silica mixed oxide (AMM-(Si30Ti)-Si-Me) by means of a modified sol-gel procedure. The Pt particles were shown by transmission electron microscopy to retain their approximate original average diameter. The catalytic activity of the Pt-colloid-containing titania-silica mixed oxide catalysts was tested with the hydrogenation of 2-hexyne at 1 bar in decane or 1-propanol in a batch reactor. Selectivities to cis/trans-2-hexene were higher than those for PVP-stabilized colloids dispersed in the liquid phase. In colloidal dispersions of the PVP-stabilized catalyst in propanol, an initial a-hexene selectivity of 80% at a conversion of < 10% fell to ca. 45% at 100% conversion. With the AMM-supported catalyst, a 2-hexene selectivity of > 94% was observed at hexyne conversions up to 50%, and at complete conversion a selectivity to 2-hexenes of 88% was achieved (cis-2-hexene selectivity of 91%), Thermal treatment of the platinum-containing AMM-(Si30Ti)-Si-Me in an oxygen atmosphere leads to the removal of the protective PVP shell surrounding the colloids inside the sol-gel material, as detected by C-13-MAS NMR spectroscopy, resulting in an increase in both surface area and Pt particle size. The resulting catalysts showed lower selectivity for 2-hexene. A control experiment showed that the presence of PVP was responsible for the high selectivities to cis/trans-2-hexene exhibited by the AMM-supported colloidal Pt catalysts.

The thermal stability of the Al-Zr mixed oxides has been studied over the whole range of composition. The effect of temperature treatment on porosity, crystallinity, and microstructure has been investigated (Ar adsorption-isotherms, HR-TEM, EDX, XRD, DRIFTS). The effect of impregnation and doping on the temperature stability of these oxides is shown. An amorphous porous Al-Zr mixed oxide, stabilized with 5% Si oxide and whose microstructure is stable up to 1400 degrees C with no indication of phase separation or nanocrystal formation, was prepared. The study shows, that amorphous mixed oxides may be a promising new approach to the development of high-temperature stable porous materials.

In 2-mm microreactors the activity and selectivity of catalyst library components can be monitored directly by robot-controlled mass spectrometry (the principle setup is shown in the scheme). A maximum of 60 seconds per library component are required.

Amorphous microporous mixed oxides of indium and silicon (AMM-InxSi) have been prepared by our acid-catalyzed sol-gel method. The materials are amorphous with a narrow pore-size distribution with pore widths around 0.7 nm, a surface area about 500-800 m2 g-1 (BET) and contain homogeneously distributed In-centers in the silicon matrix (XRD, TEM, EXAFS). These materials have been found to be excellent catalysts for the oxidative dimerization of propene with air to 1,5-hexadiene with high selectivity. The best reaction conditions found are gas phase, normal pressure at 550-600°C. Propene conversion has reached 10% with selectivities >80%.

We here describe how to design vanadium-centred active sites at the inner surfaces of both well defined microporous and well defined mesoporous siliceous hosts. Each type of vanadia-silica catalyst has been extensively characterised (in regard to surface area, pore size and hydrophobicity) and X-ray absorption spectroscopy establishes the active site for these conversions to be a vanadyl group. These centres are catalytically active under mild conditions for both the epoxidation of a typical alkene and the selective oxidation of a typical alkane. Placing methyl groups in the vicinity of this active site significantly enhances the catalytic performance towards epoxidation.

In a 8-μL multichambered microreactor (the photo shows the components) material libraries can be produced in a simple manner through combinatorial hydrothermal synthesis. In a model experiment the synthesis of the zeolite TS-1 has been varied combinatorially. The resulting library is characterized directly by automated microdiffraction.

A silicalite-1 nanophase material with an elementary particle size of 18-100 nm is synthesized from clear solution and isolated and purified using supercentrifugation. The nanopowder is characterized in detail using scanning electron microscopy, high-resolution transmission electron microscopy, attenuated force microscopy, Si-29 magic angle spinning NMR, C-13 cross polarization magic angle spinning NMR, X-ray diffraction, dinitrogen physisorption, and thermogravimetric analysis and compared with micrometer-sized silicalite-1. The nanosized and micrometer-sized materials have many common properties including the refined structure and the nature and concentrations of tetrapropylammonium species incorporated during the synthesis. Unique properties of the nanophase are a splitting of the characteristic framework vibration at 550 cm(-1) into a doublet at 555 and 570 cm(-1), a high concentration of defect sites, and a strain in the crystallites along the "a" crystallographic direction. The nanophase exhibits a two-stage dinitrogen physisorption in the low-pressure region, ascribed to adsorptions in micropores created by the stacking of the nanoparticles in addition to adsorptions in the intracrystalline micropores.

Catalytically active microporous thin film membranes were prepared by dip coating of an asymmetric ceramic support membrane in a Na2PtCl6containing sol based on Ti(OiPr)4. After drying and calcination, the membrane (thickness of the top layer, 0.2–0.4 μm) shows separation properties typical for microporous membranes with low defect concentration (nanofiltration). After activation with hydrogen at 250°C the membranes exhibit a hydrogenation activity significantly higher than those of comparable batch catalysts. At conditions of reaction control and limitation of hydrogen availability, 2-hexyne is semihydrogenated with such a membrane with 100% selectivity tocis-2-hexene. 1,3-Hexadiene is semihydrogenated selectively to 1-hexene. The unusual selectivity observed is attributed to the prevention of back-mixing through the use of the membrane contactor.

Ti‐ and V‐containing amorphous glasses with inner surfaces of several hundred m2g−1 and pore diameters of 0.7 nm can be prepared by a sol‐gel process. Like zeolites, these amorphous microporous mixed oxides AMM‐MxSi show catalytic shape‐selectivites. The epoxidation of alkenes with tert‐butylhydroperoxide on Ti‐containing glasses is catalyzed size‐selectively. In the hydrocracking test of decane, these materials show a product distribution that indicates the presence of Brønstedt centers in a shape‐selective environment, as well as tubular pores, the lack of additional cavities, and an effective pore size comparable to those of 10‐ and 12‐ring zeolites.

A novel polymeric organosilicon gel with the composition [MeSi(NCN)1.5]n synthesized by the reaction of MeSiCl3 with Me3Si–N=C=N–SiMe3 is reported. The reaction is performed without any solvent and with catalytic amounts of pyridine and provides highly cross-linked poly(methylsilsesquicarbodi-imide) in the form of a stable non-oxidic gel with unusual low open porosity (<1 m2 g−1). The Si–C–N gel transforms to an amorphous silicon carbonitride ceramic, SiC1.1N1.6, by the thermally induced ceramization at 1200 °C in inert atmosphere (argon). The gel-derived silicon carbonitride is thermally stable up to 1450 °C. The synthesis, characterization and pyrolysis behavior of the new polyorganosilicon gel is discussed. © 1997 John Wiley & Sons, Ltd.

Two molecules of the title compound, C 13 H 9 C 16 NO 4 .C 7 H 8 , are aggregated pairwise by hydrogen bonding. The O...O hydrogen-bond distance is 2.647 (2) A.