Ferdi Schüth

Publications of Ferdi Schüth

• Solvent-Free Catalytic Depolymerization of Cellulose to Water-Soluble Oligosaccharides.

  Authors: Niklas Meine, Roberto Rinaldi, Ferdi Schüth

  ChemSusChem. 04/2012;

  The use of cellulose is hampered by difficulties with breaking up the biopolymer into soluble products. Herein, we show that the impregnation of cellulosic substrates with catalytic amounts of aThe use of cellulose is hampered by difficulties with breaking up the biopolymer into soluble products. Herein, we show that the impregnation of cellulosic substrates with catalytic amounts of a strong acid (e.g., H(2) SO(4) , HCl) is a highly effective strategy for minimizing the contact problem commonly experienced in mechanically assisted, solid-state reactions. Milling the acid-impregnated cellulose fully converts the substrate into water-soluble oligosaccharides within 2 h. In aqueous solution, soluble products are easily hydrolyzed at 130 °C in 1 h, leading to 91 % conversion of the glucan fraction of α-cellulose into glucose, and 96 % of the xylans into xylose. Minor products are glucose dimers (8 %), 5-hydroxymethylfurfural (1 %) and furfural (4 %). Milling practical feedstocks (e.g., wood, sugarcane bagasse, and switchgrass) also results to water-soluble products (oligosaccharides and lignin fragments). The integrated approach (solid-state depolymerization in combination with liquid-phase hydrolysis) could well hold the key to a highly efficient "entry process" in biorefinery schemes.

• A strategy for the synthesis of mesostructured metal oxides with lower oxidation States.

  Authors: Harun Tüysüz, Claudia Weidenthaler, Ferdi Schüth

  Chemistry (Weinheim an der Bergstrasse, Germany). 03/2012; 18(16):5080-6.

  A detailed study on the pseudomorphic conversion of ordered mesoporous Co(3) O(4) and ferrihydrite into CoO and Fe(3) O(4) , respectively, by using alcohol/water vapor as a gentle reducing agent isA detailed study on the pseudomorphic conversion of ordered mesoporous Co(3) O(4) and ferrihydrite into CoO and Fe(3) O(4) , respectively, by using alcohol/water vapor as a gentle reducing agent is described. The reduction conditions for the transformation were optimized. In addition, the first one-pot synthesis of mesostructured CoO by using nanocasting with cubic ordered silica as a hard template is demonstrated.

• Synthesis, Crystal Structures, and Hydrogen-Storage Properties of Eu(AlH(4))(2) and Sr(AlH(4))(2) and of Their Decomposition Intermediates, EuAlH(5) and SrAlH(5).

  Authors: André Pommerin, Aron Wosylus, Michael Felderhoff, Ferdi Schüth, Claudia Weidenthaler

  Inorganic chemistry. 03/2012; 51(7):4143-50.

  Complex Eu(AlH(4))(2) and Sr(AlH(4))(2) hydrides have been prepared by a mechanochemical metathesis reaction from NaAlH(4) and europium or strontium chlorides. The crystal structures were solved fromComplex Eu(AlH(4))(2) and Sr(AlH(4))(2) hydrides have been prepared by a mechanochemical metathesis reaction from NaAlH(4) and europium or strontium chlorides. The crystal structures were solved from powder X-ray diffraction data in combination with solid-state (27)Al NMR spectroscopy. The thermolysis pathway was analyzed in detail, allowing identification of new intermediate EuAlH(5)/SrAlH(5) compounds. Rehydrogenation experiments indicate that the second decomposition step is reversible.

• Surface diels-alder reactions as an effective method to synthesize functional carbon materials.

  Authors: Helena Kaper, Agnes Grandjean, Claudia Weidenthaler, Ferdi Schüth, Frédéric Goettmann

  Chemistry (Weinheim an der Bergstrasse, Germany). 02/2012; 18(13):4099-106.

  The post-synthesis chemical modification of various porous carbon materials with unsaturated organic compounds is reported. By this method, amine, alcohol, carboxylate, and sulfonic acid functionalThe post-synthesis chemical modification of various porous carbon materials with unsaturated organic compounds is reported. By this method, amine, alcohol, carboxylate, and sulfonic acid functional groups can be easily incorporated into the materials. Different carbonaceous materials with surface areas ranging from 240 to 1500 m(2)  g(-1) and pore sizes between 3.0 and 7.0 nm have been studied. The resulting materials were analyzed by elemental analysis, nitrogen sorption, FTIR spectroscopy, zeta-potential measurements, thermogravimetric analysis, photoelectron spectroscopy, and small-angle X-ray scattering. These analyses indicated that the degree of functionalization is dependent on the nature of the dienophile (reactivity, steric hindrance) and the porosity of the carbon material. As possible applications, the functionalized carbonaceous materials were studied as catalysts in the Knoevenagel reaction and as adsorbents for Pb(2+) from aqueous solution.

• Co3O4-SiO2 nanocomposite: a very active catalyst for CO oxidation with unusual catalytic behavior.

  Authors: Chun-Jiang Jia, Manfred Schwickardi, Claudia Weidenthaler, Wolfgang Schmidt, Satu Korhonen, Bert M Weckhuysen, Ferdi Schüth

  Journal of the American Chemical Society. 06/2011; 133(29):11279-88.

  A high surface area Co(3)O(4)-SiO(2) nanocomposite catalyst has been prepared by use of activated carbon as template. The Co(3)O(4)-SiO(2) composite, the surface of which is rich in silica and Co(II)A high surface area Co(3)O(4)-SiO(2) nanocomposite catalyst has been prepared by use of activated carbon as template. The Co(3)O(4)-SiO(2) composite, the surface of which is rich in silica and Co(II) species compared with normal Co(3)O(4), exhibited very high activity for CO oxidation even at a temperature as low as -76 °C. A rather unusual temperature-dependent activity curve, with the lowest conversion at about 80 °C, was observed with a normal feed gas (H(2)O content ~3 ppm). The U-shape of the activity curve indicates a negative apparent activation energy over a certain temperature range, which has rarely been observed for the heterogeneously catalyzed oxidation of CO. Careful investigation of the catalytic behavior of Co(3)O(4)-SiO(2) catalyst led to the conclusion that adsorption of H(2)O molecules on the surface of the catalyst caused the unusual behavior. This conclusion was supported by in situ diffuse reflectance Fourier transform infrared (DRIFT) spectroscopic experiments under both normal and dry conditions.

• Structurally designed synthesis of mechanically stable poly(benzoxazine-co-resol)-based porous carbon monoliths and their application as high-performance CO2 capture sorbents.

  Authors: Guang-Ping Hao, Wen-Cui Li, Dan Qian, Guang-Hui Wang, Wei-Ping Zhang, Tao Zhang, Ai-Qin Wang, Ferdi Schüth, Hans-Josef Bongard, An-Hui Lu

  Journal of the American Chemical Society. 06/2011; 133(29):11378-88.

  Porous carbon monoliths with defined multilength scale pore structures, a nitrogen-containing framework, and high mechanical strength were synthesized through a self-assembly ofPorous carbon monoliths with defined multilength scale pore structures, a nitrogen-containing framework, and high mechanical strength were synthesized through a self-assembly of poly(benzoxazine-co-resol) and a carbonization process. Importantly, this synthesis can be easily scaled up to prepare carbon monoliths with identical pore structures. By controlling the reaction conditions, porous carbon monoliths exhibit fully interconnected macroporosity and mesoporosity with cubic Im3m symmetry and can withstand a press pressure of up to 15.6 MPa. The use of amines in the synthesis results in a nitrogen-containing framework of the carbon monolith, as evidenced by the cross-polarization magic-angle-spinning NMR characterization. With such designed structures, the carbon monoliths show outstanding CO(2) capture and separation capacities, high selectivity, and facile regeneration at room temperature. At ~1 bar, the equilibrium capacities of the monoliths are in the range of 3.3-4.9 mmol g(-1) at 0 °C and of 2.6-3.3 mmol g(-1) at 25 °C, while the dynamic capacities are in the range of 2.7-4.1 wt % at 25 °C using 14% (v/v) CO(2) in N(2). The carbon monoliths exhibit high selectivity for the capture of CO(2) over N(2) from a CO(2)/N(2) mixture, with a separation factor ranging from 13 to 28. Meanwhile, they undergo a facile CO(2) release in an argon stream at 25 °C, indicating a good regeneration capacity.

• Yolk-shell gold nanoparticles as model materials for support-effect studies in heterogeneous catalysis: Au, @C and Au, @ZrO2 for CO oxidation as an example.

  Authors: Carolina Galeano, Robert Güttel, Michael Paul, Pablo Arnal, An-Hui Lu, Ferdi Schüth

  Chemistry (Weinheim an der Bergstrasse, Germany). 06/2011; 17(30):8434-9.

  The use of nanostructured yolk-shell materials offers a way to discriminate support and particle-size effects for mechanistic studies in heterogeneous catalysis. Herein, gold yolk-shell materialsThe use of nanostructured yolk-shell materials offers a way to discriminate support and particle-size effects for mechanistic studies in heterogeneous catalysis. Herein, gold yolk-shell materials have been synthesized and used as model catalysts for the investigation of support effects in CO oxidation. Carbon has been selected as catalytically inert support to study the intrinsic activity of the gold nanoparticles, and for comparison, zirconia has been used as oxidic support. Au, @C materials have been synthesized through nanocasting using two different nonporous-core@mesoporous-shell exotemplates: Au@SiO(2)@ZrO(2) and Au@SiO(2)@m-SiO(2). The catalytic activity of Au, @C with a gold core of about 14 nm has been evaluated and compared with Au, @ZrO(2) of the same gold core size. The strong positive effect of metal oxide as support material on the activity of gold has been proved. Additionally, size effects were investigated using carbon as support to determine only the contribution of the nanoparticle size on the catalytic activity of gold. Therefore, Au, @C with a gold core of about 7 nm was studied showing a less pronounced positive effect on the activity than the metal oxide support effect.

• Controlled nanostructures for applications in catalysis.

  Authors: Ferdi Schüth

  Physical chemistry chemical physics : PCCP. 02/2011; 13(7):2447-8.

• Colloidal metal nanoparticles as a component of designed catalyst.

  Authors: Chun-Jiang Jia, Ferdi Schüth

  Physical chemistry chemical physics : PCCP. 02/2011; 13(7):2457-87.

  Recent advances in the synthesis of colloidal metal nanoparticles of controlled sizes and shapes that are relevant for catalyst design are reviewed. Three main methods, based on colloid chemistryRecent advances in the synthesis of colloidal metal nanoparticles of controlled sizes and shapes that are relevant for catalyst design are reviewed. Three main methods, based on colloid chemistry techniques in solution, i.e., chemical reduction of metal salt precursors, electrochemical synthesis, and controlled decomposition of organometallic compounds and metal-surfactant complexes, are used to synthesize metal nanoparticles. Their catalytic activity and selectivity depend on the shape, size and composition of the metal nanoparticles, and the support effect, as shown for many reactions in quasi-homogeneous and heterogeneous catalysis. A specially designed type of thermally stable catalysts--"embedded" metal catalysts, in which metal nanoparticles are isolated by porous support shells so that metal sintering is effectively avoided at high temperatures, are also introduced. The utilization of pre-prepared colloidal metal nanoparticles with tuned size, shape and composition as components of designed catalysts opens up new field in catalysis.

• Structurally designed synthesis of mechanically stable poly(benzoxazine-co-resol)-based porous carbon monoliths and their application as high-performance CO2 capture sorbents

  Authors: Guang-Ping Hao, Wen-Cui Li, Dan Qian, Guang-Hui Wang, Wei-Ping Zhang, Tao Zhang, Ai-Qin Wang, Ferdi Schüth, Hans-Josef Bongard, An-Hui Lu

  J. Am. Chem. Soc. 01/2011;

• High-temperature stable, iron-based core-shell catalysts for ammonia decomposition.

  Authors: Mathias Feyen, Claudia Weidenthaler, Robert Güttel, Klaus Schlichte, Ulrich Holle, An-Hui Lu, Ferdi Schüth

  Chemistry (Weinheim an der Bergstrasse, Germany). 01/2011; 17(2):598-605.

  High-temperature, stable core-shell catalysts for ammonia decomposition have been synthesized. The highly active catalysts, which were found to be also excellent model systems for fundamentalHigh-temperature, stable core-shell catalysts for ammonia decomposition have been synthesized. The highly active catalysts, which were found to be also excellent model systems for fundamental studies, are based on α-Fe(2)O(3) nanoparticles coated by porous silica shells. In a bottom-up approach, hematite nanoparticles were firstly obtained from the hydrothermal reaction of ferric chlorides, L-lysine, and water with adjustable average sizes of 35, 47, and 75 nm. Secondly, particles of each size could be coated by a porous silica shell by means of the base-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) with cetyltetramethylammonium bromide (CTABr) as porogen. After calcination, TEM, high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray (EDX), XRD, and nitrogen sorption studies confirmed the successful encapsulation of hematite nanoparticles inside porous silica shells with a thickness of 20 nm, thereby leading to composites with surface areas of approximately 380 m(2)  g(-1) and iron contents between 10.5 and 12.2 wt %. The obtained catalysts were tested in ammonia decomposition. The influence of temperature, iron oxide core size, possible diffusion limitations, and dilution effects of the reagent gas stream with noble gases were studied. The catalysts are highly stable at 750 °C with a space velocity of 120,000 cm(3)  g(cat)(-1)  h(-1) and maintained conversions of around 80 % for the testing period time of 33 h. On the basis of the excellent stability under reaction conditions up to 800 °C, the system was investigated by in situ XRD, in which body-centered iron was determined, in addition to FeN(x), as the crystalline phase under reaction conditions above 650 °C.

• An integrated catalytic approach to fermentable sugars from cellulose.

  Authors: Roberto Rinaldi, Philip Engel, Jochen Büchs, Antje C Spiess, Ferdi Schüth

  ChemSusChem. 10/2010; 3(10):1151-3.

• Spatially and size selective synthesis of Fe-based nanoparticles on ordered mesoporous supports as highly active and stable catalysts for ammonia decomposition.

  Authors: An-Hui Lu, Joerg-Joachim Nitz, Massimiliano Comotti, Claudia Weidenthaler, Klaus Schlichte, Christian W Lehmann, Osamu Terasaki, Ferdi Schüth

  Journal of the American Chemical Society. 10/2010; 132(40):14152-62.

  Uniform and highly dispersed γ-Fe(2)O(3) nanoparticles with a diameter of ∼6 nm supported on CMK-5 carbons and C/SBA-15 composites were prepared via simple impregnation and thermal treatment. TheUniform and highly dispersed γ-Fe(2)O(3) nanoparticles with a diameter of ∼6 nm supported on CMK-5 carbons and C/SBA-15 composites were prepared via simple impregnation and thermal treatment. The nanostructures of these materials were characterized by XRD, Mössbauer spectroscopy, XPS, SEM, TEM, and nitrogen sorption. Due to the confinement effect of the mesoporous ordered matrices, γ-Fe(2)O(3) nanoparticles were fully immobilized within the channels of the supports. Even at high Fe-loadings (up to about 12 wt %) on CMK-5 carbon no iron species were detected on the external surface of the carbon support by XPS analysis and electron microscopy. Fe(2)O(3)/CMK-5 showed the highest ammonia decomposition activity of all previously described Fe-based catalysts in this reaction. Complete ammonia decomposition was achieved at 700 °C and space velocities as high as 60,000 cm(3) g(cat)(-1) h(-1). At a space velocity of 7500 cm(3) g(cat)(-1) h(-1), complete ammonia conversion was maintained at 600 °C for 20 h. After the reaction, the immobilized γ-Fe(2)O(3) nanoparticles were found to be converted to much smaller nanoparticles (γ-Fe(2)O(3) and a small fraction of nitride), which were still embedded within the carbon matrix. The Fe(2)O(3)/CMK-5 catalyst is much more active than the benchmark NiO/Al(2)O(3) catalyst at high space velocity, due to its highly developed mesoporosity. γ-Fe(2)O(3) nanoparticles supported on carbon-silica composites are structurally much more stable over extended periods of time but less active than those supported on carbon. TEM observation reveals that iron-based nanoparticles penetrate through the carbon layer and then are anchored on the silica walls, thus preventing them from moving and sintering. In this way, the stability of the carbon-silica catalyst is improved. Comparison with the silica supported iron oxide catalyst reveals that the presence of a thin layer of carbon is essential for increased catalytic activity.

• Highly active iron oxide supported gold catalysts for CO oxidation: how small must the gold nanoparticles be?

  Authors: Yong Liu, Chun-Jiang Jia, Jun Yamasaki, Osamu Terasaki, Ferdi Schüth

  Angewandte Chemie (International ed. in English). 08/2010; 49(33):5771-5.

• Accessing ultrashort reaction times in particle formation with SAXS experiments: ZnS precipitation on the microsecond time scale.

  Authors: Wolfgang Schmidt, Patrick Bussian, Mika Lindén, Heinz Amenitsch, Patrik Agren, Michael Tiemann, Ferdi Schüth

  Journal of the American Chemical Society. 05/2010; 132(19):6822-6.

  Precipitation of zinc sulfide particles is a very rapid process, and monitoring of the particle growth is experimentally very demanding. Applying a liquid jet flow cell, we were able to follow zincPrecipitation of zinc sulfide particles is a very rapid process, and monitoring of the particle growth is experimentally very demanding. Applying a liquid jet flow cell, we were able to follow zinc sulfide particle formation on time scales down to 10(-5) s. The flow cell was designed in such a way that data acquisition on the microsecond time scale was possible under steady-state conditions along a liquid jet (tubular reactor concept), allowing SAXS data accumulation over a time scale of minutes. We were able to monitor the growth of zinc sulfide particles and found experimental evidence for very rapid particle aggregation processes within the liquid jet. Under the experimental conditions the particle growth is controlled by mass transfer: i.e., the diffusion of the hydrogen sulfide into the liquid jet.

• Regioselectively controlled synthesis of colloidal mushroom nanostructures and their hollow derivatives.

  Authors: Mathias Feyen, Claudia Weidenthaler, Ferdi Schüth, An-Hui Lu

  Journal of the American Chemical Society. 05/2010; 132(19):6791-9.

  In this study, a facile and controllable synthetic route for the fabrication of mushroom nanostructures (Fe(x)O(y)@PSD-SiO(2)) and their hollow derivatives has been established. The synthesisIn this study, a facile and controllable synthetic route for the fabrication of mushroom nanostructures (Fe(x)O(y)@PSD-SiO(2)) and their hollow derivatives has been established. The synthesis consists of partial coating of Fe(x)O(y) (Fe(3)O(4) or Fe(2)O(3)) with polymer spheres, followed by attaching silica hemispheres. The surface-accessible Fe(x)O(y) nanoparticles on the Janus-type Fe(x)O(y)@PSD nanospheres are key for directing the growth of the silica hemisphere on the Fe(x)O(y)@PSD seeds. The size and the porosity of the silica hemispheres are tunable by adjusting the amount of TEOS used and addition of a proper surfactant in a Stober-type process. After the iron oxide cores were leached out with concentrated HCl, mushroom nanostructures with hollow interiors were obtained, where the morphology of the hollow interior faithfully replicates the shape of the iron oxide core previously filling this void. This synthetic strategy provides a controllable method for the large-scale preparation of asymmetric colloidal nanostructures which could serve as building blocks for the assembly of new types of nanostructures.

• Substrate size-selective catalysis with zeolite-encapsulated gold nanoparticles.

  Authors: Anders B Laursen, Karen T Højholt, Lars F Lundegaard, Søren B Simonsen, Stig Helveg, Ferdi Schüth, Michael Paul, Jan-Dierk Grunwaldt, Søren Kegnaes, Claus H Christensen, Kresten Egeblad

  Angewandte Chemie (International ed. in English). 04/2010; 49(20):3504-7.

• Acid Hydrolysis of Cellulose as the Entry Point into Biorefinery Schemes.

  Authors: Roberto Rinaldi, Ferdi Schüth

  ChemSusChem. 03/2010; 3(3):296.

• Easy synthesis of hollow polymer, carbon, and graphitized microspheres.

  Authors: An-Hui Lu, Wen-Cui Li, Guang-Ping Hao, Bernd Spliethoff, Hans-Josef Bongard, Bernd Bastian Schaack, Ferdi Schüth

  Angewandte Chemie (International ed. in English). 02/2010; 49(9):1615-8.

• Ex-post size control of high-temperature-stable yolk-shell Au, @ZrO(2) catalysts.

  Authors: Robert Güttel, Michael Paul, Ferdi Schüth

  Chemical communications (Cambridge, England). 02/2010; 46(6):895-7.

  Yolk-shell catalysts have attracted interest in both academia and industry, since they combine high-temperature stability with a reduced complexity for kinetic and mechanistic investigations. ThisYolk-shell catalysts have attracted interest in both academia and industry, since they combine high-temperature stability with a reduced complexity for kinetic and mechanistic investigations. This contribution presents a possibility to adjust the size of an active gold core inside a porous zirconia shell via an ex-post-modification approach.