Johannes A Lercher

Publications of Johannes A Lercher

• Stabilizing catalytic pathways via redundancy - selective reduction of microalgae oil to alkanes.

  Authors: Baoxiang Peng, Xiaoguo Yuan, Chen Zhao, Johannes A Lercher

  Journal of the American Chemical Society. 04/2012;

  A new route to convert crude microalgae oils using ZrO2 promoted Ni catalysts into diesel-range alkanes in a cascade reaction is presented. Ni nanoparticles catalyze the selective cleavage of C-O ofA new route to convert crude microalgae oils using ZrO2 promoted Ni catalysts into diesel-range alkanes in a cascade reaction is presented. Ni nanoparticles catalyze the selective cleavage of C-O of fatty acid esters leading to the hydrogenolysis of triglycerides. Hydrogenation of the resulting fatty acids to aldehydes (rate determining step) is uniquely catalyzed via two parallel pathways, one via aldehyde formation on metallic Ni and the second via a synergistic action by Ni and ZrO2 through adsorbing the carboxylic groups at the oxygen vacancies of ZrO2 to form carboxylates and subsequently abstracting α-hydrogen atom to produce ketene, which is in turn hydrogenated to aldehydes and decarbonylated on Ni nanoparticles.

• Inside back cover: towards quantitative conversion of microalgae oil to diesel-range alkanes with bifunctional catalysts (angew. Chem. Int. Ed. 9/2012).

  Authors: Baoxiang Peng, Yuan Yao, Chen Zhao, Johannes A Lercher

  Angewandte Chemie (International ed. in English). 02/2012; 51(9):2253.

  Hydrocarbon biodiesel can be quantitatively achieved on Ni/HBeta zeolite from crude algae oil in batch or continuous-flow reactors. In their Communication on page 2072 ff., J. Lercher et al. describeHydrocarbon biodiesel can be quantitatively achieved on Ni/HBeta zeolite from crude algae oil in batch or continuous-flow reactors. In their Communication on page 2072 ff., J. Lercher et al. describe the kinetics, reaction pathways, and fundamental chemistry of the elementary steps of the cascade hydrogenation reaction on algae oil. This approach opens new possibilities to produce sulfur-free high-grade green transportation fuels from microalgae on a large scale.

• Upgrading Pyrolysis Oil over Ni/HZSM-5 by Cascade Reactions.

  Authors: Chen Zhao, Johannes A Lercher

  Angewandte Chemie (International ed. in English). 01/2012;

  Bio-oil to hydrocarbon oil: An active, selective, and stable catalyst (Ni supported in zeolite HZSM-5) allows the conversion of a wide variety of CO and CO bonds in n-hexane-extracted pyrolysis oilBio-oil to hydrocarbon oil: An active, selective, and stable catalyst (Ni supported in zeolite HZSM-5) allows the conversion of a wide variety of CO and CO bonds in n-hexane-extracted pyrolysis oil into hydrocarbons through a cascade of hydrogenation, hydrolysis, dehydration, and dehydroaromatization reactions. Quantitative yields of C(5) -C(9) gasoline-range hydrocarbons are obtained under mild conditions in water.

• Towards quantitative conversion of microalgae oil to diesel-range alkanes with bifunctional catalysts.

  Authors: Baoxiang Peng, Yuan Yao, Chen Zhao, Johannes A Lercher

  Angewandte Chemie (International ed. in English). 11/2011; 51(9):2072-5.

  Diesel oil from microalgae oil: An approach for selective conversion of crude microalgae oil to diesel-range alkanes is reported using Ni nanoclusters supported on zeolite catalysts. The cascade ofDiesel oil from microalgae oil: An approach for selective conversion of crude microalgae oil to diesel-range alkanes is reported using Ni nanoclusters supported on zeolite catalysts. The cascade of catalyzed reactions for microalgae oil conversion is based on a metal-catalytic function for the integrated hydrogenolysis, hydrogenation, and decarbonylation as well as an acid-catalytic function for dehydration and isomerization.

• Selective modification of the acid-base properties of ceria by supported Au.

  Authors: Manuela C I Bezen, Cornelia Breitkopf, Nadia El Kolli, Jean-Marc Krafft, Catherine Louis, Johannes A Lercher

  Chemistry (Weinheim an der Bergstrasse, Germany). 06/2011; 17(25):7095-104.

  Au supported on CeO(2) prepared by deposition-precipitation with urea leads to a basic catalyst. Au acts in two ways as surface modifier. First, Au selectively interacts with Ce(4+) cations by eitherAu supported on CeO(2) prepared by deposition-precipitation with urea leads to a basic catalyst. Au acts in two ways as surface modifier. First, Au selectively interacts with Ce(4+) cations by either blocking access to or reducing Ce(4+) to Ce(3+). Second, the resulting Au atoms (presumably as Au(+) ions) act as soft, weak Lewis acid sites stabilizing carbanion intermediates and enhancing hydride abstraction in the dehydrogenation of alcohols. In consequence, the thus-synthesized basic catalyst catalyzes the dehydrogenation of propan-2-ol to acetone with high efficiency and without notable deactivation. Additionally, the dehydration pathway of propan-2-ol is eliminated, as Au also quantitatively blocks access to strongly acidic Ce(4+) ions or reduces them to Ce(3+).

• Towards quantitative catalytic lignin depolymerization.

  Authors: Virginia M Roberts, Valentin Stein, Thomas Reiner, Angeliki Lemonidou, Xuebing Li, Johannes A Lercher

  Chemistry (Weinheim an der Bergstrasse, Germany). 04/2011; 17(21):5939-48.

  The products of base-catalyzed liquid-phase hydrolysis of lignin depend markedly on the operating conditions. By varying temperature, pressure, catalyst concentration, and residence time, the yieldThe products of base-catalyzed liquid-phase hydrolysis of lignin depend markedly on the operating conditions. By varying temperature, pressure, catalyst concentration, and residence time, the yield of monomers and oligomers from depolymerized lignin can be adjusted. It is shown that monomers of phenolic derivatives are the only primary products of base-catalyzed hydrolysis and that oligomers form as secondary products. Oligomerization and polymerization of these highly reactive products, however, limit the amount of obtainable product oil containing low-molecular-weight phenolic products. Therefore, inhibition of concurrent oligomerization and polymerization reactions during hydrothermal lignin depolymerization is important to enhance product yields. Applying boric acid as a capping agent to suppress addition and condensation reactions of initially formed products is presented as a successful approach in this direction. Combination of base-catalyzed lignin hydrolysis with addition of boric acid protecting agent shifts the product distribution to lower molecular weight compounds and increases product yields beyond 85%.

• Co and Mn polysiloxanes as unique initiator-catalyst-systems for the selective liquid phase oxidation of o-xylene.

  Authors: Tobias Förster, Stephan A Schunk, Andreas Jentys, Johannes A Lercher

  Chemical communications (Cambridge, England). 01/2011; 47(11):3254-6.

  Co and Mn polysiloxanes are unique catalyst/initiator systems for the liquid phase oxidation of o-xylene showing higher activity than Co naphthenates, which is related to the weak interaction of theCo and Mn polysiloxanes are unique catalyst/initiator systems for the liquid phase oxidation of o-xylene showing higher activity than Co naphthenates, which is related to the weak interaction of the polar products with the hydrophobic surface as well as the absence of hydroxyl groups and surrounding oxygenates limiting radical quenching.

• Combined TPRx, in situ GISAXS and GIXAS studies of model semiconductor-supported platinum catalysts in the hydrogenation of ethene.

  Authors: Sonja A Wyrzgol, Susanne Schäfer, Sungsik Lee, Byeongdu Lee, Marcel Di Vece, Xuebing Li, Sönke Seifert, Randall E Winans, Martin Stutzmann, Johannes A Lercher, Stefan Vajda

  Physical chemistry chemical physics : PCCP. 06/2010; 12(21):5585-95.

  The preparation, characterization and catalytic reactivity of a GaN supported Pt catalyst in the hydrogenation of ethene are presented in this feature article, highlighting the use of in situThe preparation, characterization and catalytic reactivity of a GaN supported Pt catalyst in the hydrogenation of ethene are presented in this feature article, highlighting the use of in situ characterization of the material properties during sample handling and catalysis by combining temperature programmed reaction with in situ grazing incidence small-angle X-ray scattering and X-ray absorption spectroscopy. The catalysts are found to be sintering resistant at elevated temperatures as well as during reduction and hydrogenation reactions. In contrast to Pt particles of approximately 7 nm diameter, smaller particles of 1.8 nm in size are found to dynamically adapt their shape and oxidation state to the changes in the reaction environment. These smaller Pt particles also showed an initial deactivation in ethene hydrogenation, which is paralleled by the change in the particle shape. The subtle temperature-dependent X-ray absorbance of the 1.8 nm sized Pt particles indicates that subtle variations in the electronic structure induced by the state of reduction by electron tunnelling over the Schottky barrier between the Pt particles and the GaN support can be monitored.

• Hydrodeoxygenation of bio-derived phenols to hydrocarbons using RANEY Ni and Nafion/SiO2 catalysts.

  Authors: Chen Zhao, Yuan Kou, Angeliki A Lemonidou, Xuebing Li, Johannes A Lercher

  Chemical communications (Cambridge, England). 01/2010; 46(3):412-4.

  A simple, green, cost- and energy-efficient route for converting phenolic components in bio-oil to hydrocarbons and methanol has been developed, with nearly 100% yields. In the heterogeneousA simple, green, cost- and energy-efficient route for converting phenolic components in bio-oil to hydrocarbons and methanol has been developed, with nearly 100% yields. In the heterogeneous catalysts, RANEY Ni acts as the hydrogenation catalyst and Nafion/SiO(2) acts as the Brønsted solid acid for hydrolysis and dehydration.

• Highly selective catalytic conversion of phenolic bio-oil to alkanes.

  Authors: Chen Zhao, Yuan Kou, Angeliki A Lemonidou, Xuebing Li, Johannes A Lercher

  Angewandte Chemie (International ed. in English). 02/2009; 48(22):3987-90.

  Oil and water: A new energy-efficient and atom-economical catalytic route for the production of alkanes and methanol by upgrading the phenolic fraction of bio-oil has been developed. The one-potOil and water: A new energy-efficient and atom-economical catalytic route for the production of alkanes and methanol by upgrading the phenolic fraction of bio-oil has been developed. The one-pot aqueous-phase hydrodeoxygenation process is based on two catalysts facilitating consecutive hydrogenation, hydrolysis, and dehydration reactions.

• Enhancement of Sorption Processes in the Zeolite H-ZSM5 by Postsynthetic Surface Modification.

  Authors: Stephen J Reitmeier, Oliver C Gobin, Andreas Jentys, Johannes A Lercher

  Angewandte Chemie (International ed. in English). 01/2009;

• Methyl chloride production from methane over lanthanum-based catalysts.

  Authors: Simon G Podkolzin, Eric E Stangland, Mark E Jones, Elvira Peringer, Johannes A Lercher

  Journal of the American Chemical Society. 04/2007; 129(9):2569-76.

  The mechanism of selective production of methyl chloride by a reaction of methane, hydrogen chloride, and oxygen over lanthanum-based catalysts was studied. The results suggest that methaneThe mechanism of selective production of methyl chloride by a reaction of methane, hydrogen chloride, and oxygen over lanthanum-based catalysts was studied. The results suggest that methane activation proceeds through oxidation-reduction reactions on the surface of catalysts with an irreducible metal-lanthanum, which is significantly different from known mechanisms for oxidative chlorination. Activity and spectroscopic measurements show that lanthanum oxychloride (LaOCl), lanthanum trichloride (LaCl3), and lanthanum phases with an intermediate extent of chlorination are all active for this reaction. The catalyst is stable with no noticeable deactivation after three weeks of testing. Kinetic measurements suggest that methane activation proceeds on the surface of the catalyst. Flow and pulse experiments indicate that the presence of hydrogen chloride is not required for activity, and its role appears to be limited to maintaining the extent of catalyst chlorination. In contrast, the presence of gas-phase oxygen is essential for catalytic activity. Density-functional theory calculations suggest that oxygen can activate surface chlorine species by adsorbing dissociatively and forming OCl surface species, which can serve as an active site for methane activation. The proposed mechanism, thus, involves changing of the formal oxidation state of surface chlorine from -1 to +1 without any changes in the oxidation state of the underlying metal.

• SOx storage materials under Lean-Rich cycling conditions--Part II: influence of Pt, H2O, and cycling time.

  Authors: Hendrik Dathe, Peter Haider, Andreas Jentys, Johannes A Lercher

  The journal of physical chemistry. B. 01/2007; 110(51):26024-32.

  The role of Pt and the influence of the reaction conditions during lean-rich cycling experiments were studied on a second generation SOx trapping material. The combination of the Generalized 2-DThe role of Pt and the influence of the reaction conditions during lean-rich cycling experiments were studied on a second generation SOx trapping material. The combination of the Generalized 2-D Correlation Analysis, 2-D Sample-Sample Correlation Analysis, and Factor Analysis using the MCR-ALS technique was applied to identify the reactive species. Transient surface sulfate species were formed under oxidative reaction conditions (lean mode) and decomposed under reducing reaction conditions (rich operation mode). The reduction of this species was identified to be the main contribution to the SO2 release observed under dynamic flow conditions. Pt facilitates the formation of sulfates but also catalyzes the reduction of the transient surface sulfate species leading to a higher amount of SO2 released under rich conditions. In the presence of water, this effect was diminished, which was found to be mainly a result of the suppressed formation of surface sulfate species caused by the faster transport of SO2 into the bulk phase of the SOx trapping component (BaCO3). Increasing the time under reducing conditions in the cycles leads to an enhanced reduction of the surface during rich conditions. The presence of water did not influence the bulk type species. It is proposed that for effective SO2 storage materials, strong SOx adsorption sites on the surface, the presence of water, and a short time under reducing conditions are essential.

• Formation of solvent cages around organometallic complexes in thin films of supported ionic liquid.

  Authors: Carsten Sievers, Oriol Jimenez, Thomas E Müller, Stefan Steuernagel, Johannes A Lercher

  Journal of the American Chemical Society. 12/2006; 128(43):13990-1.

  The first experimental evidence for the formation of ordered three-dimensional structures in solutions of organometallic complexes in a thin film of supported ionic liquid was obtained. The orderingThe first experimental evidence for the formation of ordered three-dimensional structures in solutions of organometallic complexes in a thin film of supported ionic liquid was obtained. The ordering effect leads to drastically reduced mobility of ionic liquid and complex molecules.

• Markownikoff and anti-Markownikoff hydroamination with palladium catalysts immobilized in thin films of silica supported ionic liquids.

  Authors: Oriol Jimenez, Thomas E Müller, Carsten Sievers, Andreas Spirkl, Johannes A Lercher

  Chemical communications (Cambridge, England). 08/2006;

  The concept of immobilising organometallic complexes in a thin film of supported ionic liquids was utilised to synthesise novel bi-functional catalysts combining soft Lewis acidic and strong BrønstedThe concept of immobilising organometallic complexes in a thin film of supported ionic liquids was utilised to synthesise novel bi-functional catalysts combining soft Lewis acidic and strong Brønsted acidic functions; the materials showed exceptional catalytic activity for the addition of aniline to styrene, providing the Markownikoff product under kinetically controlled conditions and mainly the anti-Markownikoff product in the thermodynamic regime.

• SO(x) storage materials under lean-rich cycling conditions. Part I: Identification of transient species.

  Authors: Hendrik Dathe, Peter Haider, Andreas Jentys, Johannes A Lercher

  The journal of physical chemistry. B. 07/2006; 110(22):10729-37.

  The SO(x) uptake of second generation sulfur trapping materials was studied by in situ IR spectroscopy under lean-rich cycling conditions. The combination of advanced chemometric methods includingThe SO(x) uptake of second generation sulfur trapping materials was studied by in situ IR spectroscopy under lean-rich cycling conditions. The combination of advanced chemometric methods including generalized 2D correlation analysis, 2D sample-sample correlation analysis, and multivariate curve resolution with alternating least squares allowed the detection of the species involved in the storage process. The formation of the bulk sulfate species was always accompanied by the consumption of carbonates. The reduction of a transient surface sulfate species was identified as the key parameter in the storage process under dynamic conditions. Three distinct reaction regimes were differentiated on the industrial materials under SO(x) trapping conditions being imperceptible from conventional spectra.

• On the trapping of SOx on CaO-Al2O3-based novel high capacity sorbents.

  Authors: Hendrik Dathe, Andreas Jentys, Peter Haider, Ellen Schreier, Rolf Fricke, Johannes A Lercher

  Physical chemistry chemical physics : PCCP. 05/2006; 8(13):1601-13.

  Calcium-aluminum mixed oxide based materials doped with Na and Mn were explored as sulfur trapping materials. The materials showed a three times higher total storage capacity and a higher time onCalcium-aluminum mixed oxide based materials doped with Na and Mn were explored as sulfur trapping materials. The materials showed a three times higher total storage capacity and a higher time on stream with complete SO2 removal compared to a second generation SOx trapping material which was mesoporous with calcium mainly present in oxidic form. Combining in situ XANES at the S K-edge and IR spectroscopy the key properties of the storage materials and the affiliated storage processes were identified. CaO-Al2O3 acts as the primary support and storage component, while Na+ cations adjust the base strength and enhances the storage capacity. Manganese cations provide the appropriate oxidation capacity in absence and presence of up to 10% water. The transport into the bulk phase, which is markedly influenced by a layer of sorbed water, is the rate-limiting step in presence of Mn cations. In the absence of manganese cations the oxidation step appears controlling the rate. The overall reaction network, identified by in situ IR spectroscopy and the 2D Correlation Analysis, is similar on all materials.

• Spectroscopic characterization of cobalt-containing mesoporous materials.

  Authors: Torbjørn Vrålstad, Wilhelm R Glomm, Magnus Rønning, Hendrik Dathe, Andreas Jentys, Johannes A Lercher, Gisle Oye, Michael Stöcker, Johan Sjöblom

  The journal of physical chemistry. B. 04/2006; 110(11):5386-94.

  Cobalt-containing mesoporous materials that have been prepared using different procedures have been comparatively characterized by transmission electron microscopy/energy-dispersive X-rayCobalt-containing mesoporous materials that have been prepared using different procedures have been comparatively characterized by transmission electron microscopy/energy-dispersive X-ray spectroscopy (TEM/EDS), extended X-ray absorption fine structure spectroscopy (EXAFS), X-ray absorption near edge spectroscopy (XANES), and ultraviolet-visible (UV-vis), near-infrared (NIR), and mid-infrared (mid-IR) spectroscopies, and the results provide new insights into the local environment and properties of cobalt in this type of material. TEM/EDS analyses have shown that tetraethyl orthosilicate (TEOS) may be less appropriate as a silicon source during the syntheses of cobalt-containing mesoporous materials, because the distribution of cobalt throughout the framework may become uneven. EXAFS has been determined to be the most suitable method for direct verification of framework incorporation, by identifying silicon as the backscatterer in the second shell. Such a direct verification may not be obtained using UV-vis spectroscopy. From EXAFS analyses, it is also possible to distinguish between surface-bound and framework-incorporated cobalt. There is a good agreement between the results obtained from XANES and UV-vis regarding the coordination symmetry of cobalt in the samples. The presence of cobalt in the silica framework has been determined to create Lewis acid sites, and these acid sites are suggested to be located at tetrahedral cobalt sites at the surface.

• In situ S K-edge X-ray absorption spectroscopy for understanding and developing SOx storage catalysts.

  Authors: Hendrik Dathe, Andreas Jentys, Johannes A Lercher

  The journal of physical chemistry. B. 12/2005; 109(46):21842-6.

  In situ S K-edge XANES experiments were carried out on second-generation SO(x)() trapping materials under oxidizing and reducing conditions. The experiments clearly show that the strong release ofIn situ S K-edge XANES experiments were carried out on second-generation SO(x)() trapping materials under oxidizing and reducing conditions. The experiments clearly show that the strong release of SO(2) under rich conditions at plug flow conditions is caused by the facilitated reduction of sulfite species on Pt. In the absence of Pt the sulfite species were stable under reducing conditions, while maintaining a similar total SO(2) uptake capacity. Thus, SO(x)() trapping materials without a noble metal are a clearly better option. The enhancing effect on the SO(x)() storage process of water present in the gas mixture is attributed to the formation of a higher sulfate fraction in the samples. The application of the in situ S K-edge XANES technique clearly reveals new information and insights on the behavior of the sulfur in the trapping process compared to that from the ex situ measurements and is therefore essential for designing new SO(x)() trapping materials.

• Oxidative activation of n-butane on sulfated zirconia.

  Authors: Xuebing Li, Katsutoshi Nagaoka, Laurent J. Simon, Roberta Olindo, Johannes A Lercher, Alexander Hofmann, Joachim Sauer

  Journal of the American Chemical Society. 12/2005; 127(46):16159-66.

  Catalytic activation and conversion of light alkanes by sulfated zirconia is unequivocally shown to be initiated by producing small concentrations of olefins. This occurs via stoichiometric oxidativeCatalytic activation and conversion of light alkanes by sulfated zirconia is unequivocally shown to be initiated by producing small concentrations of olefins. This occurs via stoichiometric oxidative dehydrogenation of butane by SO3 or pyrosulfate groups to butene (present mostly as alkoxy groups), water, and SO2. Thermal desorption and in situ IR spectroscopy have been used to determine all three reaction products. The concentration of butene formed determines both the catalytic activity of sulfated zirconia as well as the deactivation via formation of oligomers. The thermodynamics of the oxidative dehydrogenation of n-butane by different SZ surface structures has been examined by density functional (DFT) calculations. The calculations show that pyrosulfate or re-adsorbed SO3 species have the highest oxidizing ability.