Showing papers on "Catalysis published in 2007"

Identification of active edge sites for electrochemical H2 evolution from MoS2 nanocatalysts.

Abstract: The identification of the active sites in heterogeneous catalysis requires a combination of surface sensitive methods and reactivity studies. We determined the active site for hydrogen evolution, a reaction catalyzed by precious metals, on nanoparticulate molybdenum disulfide (MoS2) by atomically resolving the surface of this catalyst before measuring electrochemical activity in solution. By preparing MoS2 nanoparticles of different sizes, we systematically varied the distribution of surface sites on MoS2 nanoparticles on Au(111), which we quantified with scanning tunneling microscopy. Electrocatalytic activity measurements for hydrogen evolution correlate linearly with the number of edge sites on the MoS2 catalyst.

Transformation of carbon dioxide.

Abstract: 4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

Liquid-phase catalytic processing of biomass-derived oxygenated hydrocarbons to fuels and chemicals.

Abstract: Biomass has the potential to serve as a sustainable source of energy and organic carbon for our industrialized society. The focus of this Review is to present an overview of chemical catalytic transformations of biomass-derived oxygenated feedstocks (primarily sugars and sugar-alcohols) in the liquid phase to value-added chemicals and fuels, with specific examples emphasizing the development of catalytic processes based on an understanding of the fundamental reaction chemistry. The key reactions involved in the processing of biomass are hydrolysis, dehydration, isomerization, aldol condensation, reforming, hydrogenation, and oxidation. Further, it is discussed how ideas based on fundamental chemical and catalytic concepts lead to strategies for the control of reaction pathways and process conditions to produce H(2)/CO(2) or H(2)/CO gas mixtures by aqueous-phase reforming, to produce furan compounds by selective dehydration of carbohydrates, and to produce liquid alkanes by the combination of aldol condensation and dehydration/hydrogenation processes.

Catalysis in ionic liquids

Abstract: 2.5. Stabilization of IL Emulsions by Nanoparticles 2623 3. Hydrogenations in ILs 2623 3.1. Hydrogenation on IL-Stabilized Nanoparticles 2623 3.1.1. Hydrogenation of 1,3-Butadiene 2623 3.1.2. Hydrogenation of Alkenes and Arenes 2624 3.1.3. Hydrogenation of Ketones 2624 3.2. Homogeneous Catalytic Hydrogenation in ILs 2624 3.3. Hydrogenation of Functionalized ILs 2625 3.3.1. Selective Hydrogenation of Polymers 2625 3.4. Asymmetric Hydrogenations 2626 3.4.1. Enantioselective Hydrogenation 2626 3.5. Role of the ILs Purity in Hydrogenation Reactions 2628

Catalytic Carbophilic Activation: Catalysis by Platinum and Gold π Acids

Abstract: The ability of platinum and gold catalysts to effect powerful atom-economic transformations has led to a marked increase in their utilization. The quite remarkable correlation of their catalytic behavior with the available structural data, coordination chemistry, and organometallic reactivity patterns, including relativistic effects, allows the underlying principles of catalytic carbophilic activation by π acids to be formulated. The spectrum of reactivity extends beyond their utility as catalytic and benign alternatives to conventional stoichiometric π acids. The resulting reactivity profile allows this entire field of catalysis to be rationalized, and brings together the apparently disparate electrophilic metal carbene and nonclassical carbocation explanations. The advances in coupling, cycloisomerization, and structural reorganization—from the design of new transformations to the improvement to known reactions—are highlighted in this Review. The application of platinum- and gold-catalyzed transformations in natural product synthesis is also discussed.

Carbon-Carbon Coupling Reactions Catalyzed by Heterogeneous Palladium Catalysts

Abstract: 4.4. Pd on Modified Silica 159 4.5. Pd on Clay and Other Inorganic Materials 159 5. Stille, Fukuyama, and Negishi Reactions 159 5.1. Stille Reactions 159 5.1.1. Pd on Carbon (Pd/C) 159 5.1.2. Palladium on KF/Al2O3 159 5.1.3. Pd on Modified Silica (SiO2/TEG/Pd) 159 5.2. Fukuyama Reactions 159 5.2.1. Pd on Carbon (Pd/C) 159 5.2.2. Pd(OH)2 on Carbon (Perlman’s Catalyst) 160 5.3. Pd/C-Catalyzed Negishi Reactions 160 6. Ullmann-Type Coupling Reactions 161 6.1. Pd/C-Catalyzed Aryl−Aryl Coupling 161 6.2. Pd/C-Catalyzed Homocoupling of Vinyl Halides 162

Direct Synthesis of Amides from Alcohols and Amines with Liberation of H2

Abstract: Given the widespread importance of amides in biochemical and chemical systems, an efficient synthesis that avoids wasteful use of stoichiometric coupling reagents or corrosive acidic and basic media is highly desirable. We report a reaction in which primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen (the only products) in high yields and high turnover numbers. This reaction is catalyzed by a ruthenium complex based on a dearomatized PNN-type ligand [where PNN is 2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine], and no base or acid promoters are required. Use of primary diamines in the reaction leads to bis-amides, whereas with a mixed primary-secondary amine substrate, chemoselective acylation of the primary amine group takes place. The proposed mechanism involves dehydrogenation of hemiaminal intermediates formed by the reaction of an aldehyde intermediate with the amine.

Borrowing hydrogen in the activation of alcohols

Abstract: Alcohols can be temporarily converted into carbonyl compounds by the metal-catalysed removal of hydrogen. The carbonyl compounds are reactive in a wider range of transformations than the precursor alcohols and can react in situ to give imines, alkenes, and α-functionalised carbonyl compounds. The metal catalyst, which had borrowed the hydrogen, then returns it to the transformed carbonyl compound, leading to an overall process in which alcohols can be converted into amines, compounds containing CC bonds and β-functionalised alcohols.

Activity of CeOx and TiOx Nanoparticles Grown on Au(111) in the Water-Gas Shift Reaction

Abstract: The high performance of Au-CeO2 and Au-TiO2 catalysts in the water-gas shift (WGS) reaction (H2O + CO-->H2 + CO2) relies heavily on the direct participation of the oxide in the catalytic process. Although clean Au(111) is not catalytically active for the WGS, gold surfaces that are 20 to 30% covered by ceria or titania nanoparticles have activities comparable to those of good WGS catalysts such as Cu(111) or Cu(100). In TiO(2-x)/Au(111) and CeO(2-x)/Au(111), water dissociates on O vacancies of the oxide nanoparticles, CO adsorbs on Au sites located nearby, and subsequent reaction steps take place at the metal-oxide interface. In these inverse catalysts, the moderate chemical activity of bulk gold is coupled to that of a more reactive oxide.

Platinum Nanoparticle Shape Effects on Benzene Hydrogenation Selectivity

Abstract: Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-H...Pt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral nanoparticles, whereas only cyclohexane was produced on cubic nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for cyclohexane production on cubic nanoparticles is 10.9 +/- 0.4 kcal/mol, while for cuboctahedral nanoparticles, the apparent activation energies for cyclohexane and cyclohexene production are 8.3 +/- 0.2 and 12.2 +/- 0.4 kcal/mol, respectively. These activation energies are lower, and corresponding turnover rates are three times higher than those obtained with single-crystal Pt surfaces.

Electrocatalysis of oxygen reduction and small alcohol oxidation in alkaline media

Abstract: We present here a critical review of several technologically important electrocatalytic systems operating in alkaline electrolytes. These include the oxygen reduction reaction (ORR) occurring on catalysts containing Pt, Pd, Ir, Ru, or Ag, the methanol oxidation reaction (MOR) occurring on Pt-containing catalysts, and the ethanol oxidation reaction (EOR) occurring on Ni–Co–Fe alloy catalysts. Each of these catalytic systems is relevant to alkaline fuel cell (AFC) technology, while the ORR systems are also relevant to chlor-alkali electrolysis and metal-air batteries. The use of alkaline media presents advantages both in electrocatalytic activity and in materials stability and corrosion. Therefore, prospects for the continued development of alkaline electrocatalytic systems, including alkaline fuel cells, seem very promising.

Synthesis and size-selective catalysis by supported gold nanoparticles: Study on heterogeneous and homogeneous catalytic process

Abstract: Core−shell nanocomposites (R−Au) bearing well-defined gold nanoparticles as surface atoms of variable sizes (8−55 nm) have been synthesized exploiting polystyrene-based commercial anion exchangers. Immobilization of gold nanoparticles, prepared by the Frens method, onto the resin beads in the chloride form is possible by the ready exchange of the citrate-capped negatively charged gold particles. The difficulty of nanoparticle loading, avoiding aggregation, has been solved by stepwise operation. Analysis of the gold particles after immobilization and successive elution confirm the unaltered particle morphology while compared to those of the citrate-capped gold particles in colloidal dispersion. It was observed that the rate of the reaction increases with the increase in catalyst loading, which suggests the catalytic behavior of the gold nanoparticles for the reduction of the aromatic nitrocompounds. The rate constant, k, was found to be proportional to the total surface area of the nanoparticles in the sys...

Biodiesel from sunflower oil by using activated calcium oxide

Abstract: This work studies the activity of activated CaO as a catalyst in the production of biodiesel by transesterification of triglycerides with methanol. Three basic aspects were investigated: the role of H 2 O and CO 2 in the deterioration of the catalytic performance by contact with room air, the stability of the catalyst by reutilization in successive runs and the heterogeneous character of the catalytic reaction. The characterization by X-ray diffraction (XRD), evolved gas analysis by mass spectrometry (EGA-MS) during heating the sample under programmed temperature, X-ray photoelectron (XPS) and Fourier transform-infrared (FT-IR) spectroscopies allowed to concluding that CaO is rapidly hydrated and carbonated by contact with room air. Few minutes are enough to chemisorb significant amount of H 2 O and CO 2 . It is demonstrated that the CO 2 is the main deactivating agent whereas the negative effect water is less important. As a matter of fact the surface of the activated catalyst is better described as an inner core of CaO particles covered by very few layers of Ca(OH) 2 . The activation by outgassing at temperatures ≥973 K are required to revert the CO 2 poisoning. The catalyst can be reused for several runs without significant deactivation. The catalytic reaction is the result of the heterogeneous and homogeneous contributions. Part of the reaction takes place on basic sites at the surface of the catalyst, the rest is due to the dissolution of the activated CaO in methanol that creates homogeneous leached active species.

Manganese oxide catalysts for NOx reduction with NH3 at low temperatures

Abstract: Manganese oxide catalysts prepared by a precipitation method with various precipitants were investigated for the low temperature selective catalytic reduction (SCR) of NOx with NH 3 in the presence of excess O 2 . Various characterization methods such as N 2 adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and X-ray absorption near edge structure (XANES) were conducted to probe the physical and chemical properties of MnOx catalysts. The active MnOx catalysts, precipitated with sodium carbonate and calcined in air at moderate temperatures such as 523 K and 623 K, have the high surface area, the abundant Mn 4+ species, and the high concentration of surface oxygen on the surface. The amorphous Mn 3 O 4 and Mn 2 O 3 were mainly present in this active catalyst. The carbonate species appeared to help adsorb NH 3 on the catalyst surface, which resulted in the high catalytic activity at low temperatures.

Palladium nanoparticles as efficient green homogeneous and heterogeneous carbon-carbon coupling precatalysts: a unifying view.

Abstract: Pd catalysis of C-C bond formations is briefly reviewed from the angle of nanoparticles (NPs) whether they are homogeneous or heterogeneous precatalysts and whether they are intentionally preformed or generated from a Pd derivative such as Pd(OAc)2. The most studied reaction is the Heck coupling of halogenoarenes with olefins that usually proceeds at high temperature (120-160 degrees C). Under such conditions, the PdII precursor is reduced to Pd0, forming PdNPs from which Pd atom leaching, subsequent to oxidative addition of the aryl halide onto the PdNP surface, is the source of very active molecular catalysts. Other C-C coupling reactions (Suzuki, Sonogashira, Stille, Negishi, Hiyama, Corriu-Kumada, Ullmann, and Tsuji-Trost) can also be catalyzed by species produced from preformed PdNPs. For catalysis of these reactions, leaching of active Pd atoms from the PdNPs may also provide a viable molecular mechanistic scheme. Thus, the term "PdNP catalysis of C-C coupling" used in this review refers to this function of PdNPs as precursors of catalytically active Pd species (i.e., the PdNPs are precatalysts of C-C coupling reactions).

Green Chemistry and Catalysis

Abstract: Preface. Foreword. 1 Introduction: Green Chemistry and Catalysis. 1.1 Introduction. 1.2. E Factors and Atom Efficiency. 1.3 The Role of Catalysis. 1.4 The Development of Organic Synthesis. 1.5 Catalysis by Solid Acids and Bases. 1.6 Catalytic Reduction. 1.7 Catalytic Oxidation. 1.8 Catalytic C-C Bond Formation. 1.9 The Question of Solvents: Alternative Reaction Media. 1.10 Biocatalysis. 1.11 Renewable Raw Materials and White Biotechnology. 1.12 Enantioselective Catalysis. 1.13 Risky Reagents. 1.14 Process Integration and Catalytic Cascades. References. 2 Solid Acids and Bases as Catalysts. 2.1 Introduction. 2.2 Solid Acid Catalysis. 2.2.1 Acidic Clays. 2.2.2 Zeolites and Zeotypes: Synthesis and Structure. 2.2.3 Zeolite-catalyzed Reactions in Organic Synthesis. 2.2.3.1 Electrophilic Aromatic Substitutions. 2.2.3.2 Additions and Eliminations. 2.2.3.3 Rearrangements and Isomerizations. 2.2.3.4 Cyclizations. 2.2.4 Solid Acids Containing Surface SO3H Functionality. 2.2.5 Heteropoly Acids. 2.3 Solid Base Catalysis. 2.3.1 Anionic Clays: Hydrotalcites. 2.3.2 Basic Zeolites. 2.3.3 Organic Bases Attached to Mesoporous Silicas. 2.4 Other Approaches. References. 3 Catalytic Reductions. 3.1 Introduction. 3.2 Heterogeneous Reduction Catalysts. 3.2.1 General Properties. 3.2.2 Transfer Hydrogenation Using Heterogeneous Catalysts. 3.2.3 Chiral Heterogeneous Reduction Catalysts. 3.3 Homogeneous Reduction Catalysts. 3.3.1 Wilkinson Catalyst. 3.3.2 Chiral Homogeneous Hydrogenation Catalysts and Reduction of the C= C Double Bond. 3.3.3 Chiral Homogeneous Catalysts and Ketone Hydrogenation. 3.3.4 Imine Hydrogenation. 3.3.5 Transfer Hydrogenation using Homogeneous Catalysts. 3.4 Biocatalytic Reductions. 3.4.1 Introduction. 3.4.2 Enzyme Technology in Biocatalytic Reduction. 3.4.3 Whole Cell Technology for Biocatalytic Reduction. 3.5 Conclusions. References. 4 Catalytic Oxidations. 4.1 Introduction. 4.2 Mechanisms of Metal-catalyzed Oxidations: General Considerations. 4.2.1 Homolytic Mechanisms. 4.2.1.1 Direct Homolytic Oxidation of Organic Substrates. 4.2.2 Heterolytic Mechanisms. 4.2.2.1 Catalytic Oxygen Transfer. 4.2.3 Ligand Design in Oxidation Catalysis. 4.2.4 Enzyme Catalyzed Oxidations. 4.3 Alkenes. 4.3.1 Epoxidation. 4.3.1.1 Tungsten Catalysts. 4.3.1.2 Rhenium Catalysts. 4.3.1.3 Ruthenium Catalysts. 4.3.1.4 Manganese Catalysts. 4.3.1.5 Iron Catalysts. 4.3.1.6 Selenium and Organocatalysts. 4.3.1.7 Hydrotalcite and Alumina Systems. 4.3.1.8 Biocatalytic Systems. 4.3.2 Vicinal Dihydroxylation. 4.3.3 Oxidative Cleavage of Olefins. 4.3.4 Oxidative Ketonization. 4.3.5 Allylic Oxidations. 4.4 Alkanes and Alkylaromatics. 4.4.1 Oxidation of Alkanes. 4.4.2 Oxidation of Aromatic Side Chains. 4.4.3 Aromatic Ring Oxidation. 4.5 Oxygen-containing Compounds. 4.5.1 Oxidation of Alcohols. 4.5.1.1 Ruthenium Catalysts. 4.5.1.2 Palladium-catalyzed Oxidations with O 2 . 4.5.1.3 Gold Catalysts. 4.5.1.4 Copper Catalysts. 4.5.1.5 Other Metals as Catalysts for Oxidation with O 2 . 4.5.1.6 Catalytic Oxidation of Alcohols with Hydrogen Peroxide. 4.5.1.7 Oxoammonium Ions in Alcohol Oxidation. 4.5.1.8 Biocatalytic Oxidation of Alcohols. 4.5.2 Oxidative Cleavage of 1,2-Diols. 4.5.3 Carbohydrate Oxidation. 4.5.4 Oxidation of Aldehydes and Ketones. 4.5.4.1 Baeyer-Villiger Oxidation. 4.5.5 Oxidation of Phenols. 4.5.6 Oxidation of Ethers. 4.6 Heteroatom Oxidation. 4.6.1 Oxidation of Amines. 4.6.1.1 Primary Amines. 4.6.1.2 Secondary Amines. 4.6.1.3 Tertiary Amines. 4.6.1.4 Amides. 4.6.2 Sulfoxidation. 4.7 Asymmetric Oxidation. 4.7.1 Asymmetric Epoxidation of Olefins. 4.7.2 Asymmetric Dihydroxylation of Olefins. 4.7.3 Asymmetric Sulfoxidation. 4.7.4 Asymmetric Baeyer-Villiger Oxidation. 4.5 Conclusion. References. 5 Catalytic Carbon-Carbon Bond Formation. 5.1 Introduction. 5.2 Enzymes for Carbon-Carbon Bond Formation. 5.2.1 Enzymatic Synthesis of Cyanohydrins. 5.2.1.1 Hydroxynitrile Lyases. 5.2.1.2 Lipase-based Dynamic Kinetic Resolution. 5.2.2 Enzymatic Synthesis of &alpha -Hydroxyketones (Acyloins). 5.2.3 Enzymatic Synthesis of &alpha -Hydroxy Acids. 5.2.4 Enzymatic Synthesis of Aldols (&beta -Hydroxy Carbonyl Compounds). 5.2.4.1 DHAP-dependent Aldolases. 5.2.4.2 PEP- and Pyruvate-dependent Aldolases. 5.2.4.3 Glycine-dependent Aldolases. 5.2.4.4 Acetaldehyde-dependent Aldolases. 5.2.5 Enzymatic Synthesis of &beta -Hydroxynitriles. 5.3 Transition Metal Catalysis. 5.3.1 Carbon Monoxide as a Building Block. 5.3.1.1 Carbonylation of R-X (CO "Insertion/R-migration"). 5.3.1.2 Aminocarbonylation. 5.3.1.3 Hydroformylation or "Oxo" Reaction. 5.3.1.4 Hydroaminomethylation. 5.3.1.5 Methyl Methacrylate via Carbonylation Reactions. 5.3.2 Heck-type Reactions. 5.3.2.1 Heck Reaction. 5.3.2.2 Suzuki and Sonogashira Reaction. 5.3.3 Metathesis. 5.3.3.1 Metathesis involving Propylene. 5.3.3.2 Ring-opening Metathesis Polymerization (ROMP). 5.3.3.3 Ring-closing Metathesis (RCM). 5.4 Conclusion and Outlook. References. 6 Hydrolysis. 6.1 Introduction. 6.1.1 Stereoselectivity of Hydrolases. 6.1.2 Hydrolase-based Preparation of Enantiopure Compounds. 6.1.2.1 Kinetic Resolutions. 6.1.2.2 Dynamic Kinetic Resolutions. 6.1.2.3 Kinetic Resolutions Combined with Inversions. 6.1.2.4 Hydrolysis of Symmetric Molecules and the "meso-trick." 6.2 Hydrolysis of Esters. 6.2.1 Kinetic Resolutions of Esters. 6.2.2 Dynamic Kinetic Resolutions of Esters. 6.2.3 Kinetic Resolutions of Esters Combined with Inversions. 6.2.4 Hydrolysis of Symmetric Esters and the "meso-trick." 6.3 Hydrolysis of Amides. 6.3.1 Production of Amino Acids by (Dynamic) Kinetic Resolution. 6.3.1.1 The Acylase Process. 6.3.1.2 The Amidase Process. 6.3.1.3 The Hydantoinase Process. 6.3.1.4 Cysteine. 6.3.2 Enzyme-catalysed Hydrolysis of Amides. 6.3.3 Enzyme-catalysed Deprotection of Amines. 6.4 Hydrolysis of Nitriles. 6.4.1 Nitrilases. 6.4.2 Nitrile Hydratases. 6.5 Conclusion and Outlook. References. 7 Catalysis in Novel Reaction Media. 7.1 Introduction. 7.1.1 Why use a solvent? 7.1.2 Choice of Solvent. 7.1.3 Alternative Reaction Media and Multiphasic Systems. 7.2 Two Immiscible Organic Solvents. 7.3 Aqueous Biphasic Catalysis. 7.3.1 Olefin Hydroformylation. 7.3.2 Hydrogenation. 7.3.3 Carbonylations. 7.3.4 Other C-C Bond Forming Reactions. 7.3.5 Oxidations. 7.4 Fluorous Biphasic Catalysis. 7.4.1 Olefin Hydroformylation. 7.4.2 Other Reactions. 7.5 Supercritical Carbon Dioxide. 7.5.1 Supercritical Fluids. 7.5.2 Supercritical Carbon Dioxide. 7.5.3 Hydrogenation. 7.5.4 Oxidation. 7.5.5 Biocatalysis. 7.6 Ionic Liquids. 7.7 Biphasic Systems with Supercritical Carbon Dioxide. 7.8 Thermoregulated Biphasic Catalysis. 7.9 Conclusions and Prospects. References. 8 Chemicals from Renewable Raw Materials. 8.1 Introduction. 8.2 Carbohydrates. 8.2.1 Chemicals from Glucose via Fermentation. 8.2.2 Ethanol. 8.2.2.1 Microbial Production of Ethanol. 8.2.2.2 Green Aspects. 8.2.3 Lactic Acid. 8.2.4 1,3-Propanediol. 8.2.5 3-Hydroxypropanoic Acid. 8.2.6 Synthesizing Aromatics in Nature's Way. 8.2.7 Aromatic -Amino Acids. 8.2.7 Indigo: the Natural Color. 8.2.8 Pantothenic Acid. 8.2.9 The &beta -Lactam Building Block 7-Aminodesacetoxycephalosporanic Acid. 8.2.9 Riboflavin. 8.3 Chemical and Chemoenzymatic Transformations of Carbohydrates into Fine Chemicals and Chiral Building Blocks. 8.3.1 Ascorbic Acid. 8.3.2 Carbohydrate-derived C3 and C4 Building Blocks. 8.3.3 5-Hydroxymethylfurfural and Levulinic Acid. 8.4 Fats and Oils. 8.4.1 Biodiesel. 8.4.2 Fatty Acid Esters. 8.5 Terpenes. 8.6 Renewable Raw Materials as Catalysts. 8.7 Green Polymers from Renewable Raw Materials. 8.8 Concluding Remarks. References. 9 Process Integration and Cascade Catalysis. 9.1 Introduction. 9.2 Dynamic Kinetic Resolutions by Enzymes Coupled with Metal Catalysts. 9.3 Combination of Asymmetric Hydrogenation with Enzymatic Hydrolysis. 9.4 Catalyst Recovery and Recycling. 9.5 Immobilization of Enzymes: Cross-linked Enzyme Aggregates (CLEAs). 9.6 Conclusions and Prospects. References. 10 Epilogue: Future Outlook. 10.1 Green Chemistry: The Road to Sustainability. 10.2 Catalysis and Green Chemistry. 10.3 The Medium is the Message. 10.4 Metabolic Engineering and Cascade Catalysis. 10.5 Concluding Remarks. References. Subject Index.

Base metal catalyzed dehydrogenation of ammonia-borane for chemical hydrogen storage.

Abstract: We report here the first example of a homogeneous first row transition-metal-based catalyst which is active for dehydrogenation of ammonia−borane, H3NBH3, a promising chemical hydrogen storage material. Addition of ammonia−borane to an active catalyst formed in situ from the reaction of Ni(cod)2 and 2 equiv of an appropriate N-heterocyclic carbene (NHC) rapidly evolves hydrogen at 60 °C. Using a gas burette to quantify the gas evolved, 29 of a possible 31 mL of H2 for 3 equiv of H2 was produced, equating to >2.5 equiv of H2 from ammonia−borane. Kinetic isotope effects of deuterated derivatives of ammonia−borane suggest that both N−H and B−H bonds are being broken in the rate-determining step(s).

Catalytic Direct Arylation of Heteroaromatic Compounds

Abstract: The direct intermolecular arylation reactions of heteroaromatic compounds such as pyrroles, furans, thiophenes, azoles, and pyridines with aryl halides using palladium or rhodium catalysts have sig...

Nanoparticles and Catalysis

Abstract: Transition-metal Nanoparticles in Catalysis: From Historical Background to the State of the Art Surfactant-stabilized Nanoparticles as Catalyst Precursors - Scientific Basis, Recent Developments and an Outlook Nanoparticle-catalysts Based on Nanostructured Polymers PAMAM-dendrimer Templated Catalysts Aerogel-supported Nanoparticles in Catalysis Transition-metal Catalysis in Imidazolium Ionic Liquids Carbon and Silicon Nanotubes-containing Catalysis Size-selective Synthesis of Nanostructured Metal- and Metal-oxide Colloids and their Use as Catalysts Multimetallic Nanoparticles Prepared by Redox Processes Applied in Catalysis The Role of Palladium Nanoparticles as Catalysts for Carbon-carbon Coupling Reactions Rhodium and Ruthenium Nanoparticles in Catalysis Supported Gold Nanoparticle as Oxidation Catalysts Gold Nanoparticle Catalyzed Oxidation in Organic Chemistry AuNP-catalyzed Propene Epoxidation by Dioxygen and Dihydrogen Gold Nanoparticles: Recent Advances in CO Oxidation NO Heterogeneous Catalysis Viewed from the Angle of Nanoparticles Hydrocarbon Catalytic Reactivity of Supported Nanometallic Particles Surface Organometallic Chemistry on Metallic NPs: Synthesis, Characterization and Application in Catalysis

Heterogeneous catalytic synthesis of ethanol from biomass-derived syngas.

Abstract: The selective catalytic conversion of biomass-derived syngas into ethanol is thermodynamically feasible at temperatures below roughly 350 °C at 30 bar. However, if methane is allowed as a reaction product, the conversion to ethanol (or other oxygenates) is extremely limited. Experimental results show that high selectivities to ethanol are only achieved at very low conversions, typically less than 10%. The most promising catalysts for the synthesis of ethanol are based on Rh, though some other formulations (such as modified methanol synthesis catalysts) show promise. (Critical review—173 references.)

Low Temperature CO Oxidation over Unsupported Nanoporous Gold

Abstract: Supported Au nanoclusters are well-known for their unusual properties in catalysis. We describe here that nanostructured porous Au made via dealloying represents a new class of unsupported catalysts with extraordinary activities in important reactions such as CO oxidation. Although nanoporous Au may contain some oxides on the surface, our results demonstrate that it is metallic Au that plays the main role in this catalytic reaction. Furthermore, this material has good low-temperature catalytic stability and is extremely CO tolerant.