Olefin Polymerization

Download Olefin Polymerization PDF Online Free

Author :
Publisher : Wiley-VCH
ISBN 13 : 9783527317424
Total Pages : 0 pages
Book Rating : 4.3/5 (174 download)

DOWNLOAD NOW!


Book Synopsis Olefin Polymerization by : Walter Kaminsky

Download or read book Olefin Polymerization written by Walter Kaminsky and published by Wiley-VCH. This book was released on 2006-08-18 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an enormous velocity, olefin polymerization has expanded to one of the most significant fields in polymers since the first industrial use about 50 years ago. In 2005, 100 million tons of polyolefins were produced - the biggest part was catalyzed by metallorganic compounds. The Hamburg Macromolecular Symposium 2005 with the title "Olefin Polymerization" involved topics such as new catalysts and cocatalysts, kinetics, mechanism and polymer reaction engineering, synthesis of special polymers, and characterization of polyolefins. The conference combined scientists from different disciplines to discuss latest research results of polymers and to offer each other the possibility of cooperation. This is reflected in this volume, which contains invited lectures and selected posters presented at the symposium.

Iron and Cobalt Catalysts

Download Iron and Cobalt Catalysts PDF Online Free

Author :
Publisher : MDPI
ISBN 13 : 303928388X
Total Pages : 414 pages
Book Rating : 4.0/5 (392 download)

DOWNLOAD NOW!


Book Synopsis Iron and Cobalt Catalysts by : Wilson D. Shafer

Download or read book Iron and Cobalt Catalysts written by Wilson D. Shafer and published by MDPI. This book was released on 2020-06-23 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the turn of the last century when the field of catalysis was born, iron and cobalt have been key players in numerous catalysis processes. These metals, due to their ability to activate CO and CH, haev a major economic impact worldwide. Several industrial processes and synthetic routes use these metals: biomass-to-liquids (BTL), coal-to-liquids (CTL), natural gas-to-liquids (GTL), water-gas-shift, alcohol synthesis, alcohol steam reforming, polymerization processes, cross-coupling reactions, and photocatalyst activated reactions. A vast number of materials are produced from these processes, including oil, lubricants, waxes, diesel and jet fuels, hydrogen (e.g., fuel cell applications), gasoline, rubbers, plastics, alcohols, pharmaceuticals, agrochemicals, feed-stock chemicals, and other alternative materials. However, given the true complexities of the variables involved in these processes, many key mechanistic issues are still not fully defined or understood. This Special Issue of Catalysis will be a collaborative effort to combine current catalysis research on these metals from experimental and theoretical perspectives on both heterogeneous and homogeneous catalysts. We welcome contributions from the catalysis community on catalyst characterization, kinetics, reaction mechanism, reactor development, theoretical modeling, and surface science.

Pincer Compounds

Download Pincer Compounds PDF Online Free

Author :
Publisher : Elsevier
ISBN 13 : 0128129328
Total Pages : 756 pages
Book Rating : 4.1/5 (281 download)

DOWNLOAD NOW!


Book Synopsis Pincer Compounds by : David Morales-Morales

Download or read book Pincer Compounds written by David Morales-Morales and published by Elsevier. This book was released on 2018-04-11 with total page 756 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pincer Compounds: Chemistry and Applications offers valuable state-of-the-art coverage highlighting highly active areas of research—from mechanistic work to synthesis and characterization. The book focuses on small molecule activation chemistry (particularly H2 and hydrogenation), earth abundant metals (such as Fe), actinides, carbene-pincers, chiral catalysis, and alternative solvent usage. The book covers the current state of the field, featuring chapters from renowned contributors, covering four continents and ranging from still-active pioneers to new names emerging as creative strong contributors to this fascinating and promising area. Over a decade since the publication of Morales-Morales and Jensen's The Chemistry of Pincer Compounds (Elsevier 2007), research in this unique area has flourished, finding a plethora of applications in almost every single branch of chemistry—from their traditional application as very robust and active catalysts all the way to potential biological and pharmaceutical applications. - Describes the chemistry and applications of this important class of organometallic and coordination compounds - Includes contributions from global leaders in the field, featuring pioneers in the area as well as emerging experts conducting exciting research on pincer complexes - Highlights areas of promising and active research, including small molecule activation, earth abundant metals, and actinide chemistry

Catalysis with Earth-abundant Elements

Download Catalysis with Earth-abundant Elements PDF Online Free

Author :
Publisher : Royal Society of Chemistry
ISBN 13 : 178801118X
Total Pages : 431 pages
Book Rating : 4.7/5 (88 download)

DOWNLOAD NOW!


Book Synopsis Catalysis with Earth-abundant Elements by : Uwe Schneider

Download or read book Catalysis with Earth-abundant Elements written by Uwe Schneider and published by Royal Society of Chemistry. This book was released on 2020-10-30 with total page 431 pages. Available in PDF, EPUB and Kindle. Book excerpt: Considering the limited resources of our planet, earth-abundant elements will have to be explored increasingly in the future. This book highlights the uses of the most earth-abundant elements in catalysis and will be of interest to graduates, academic researchers and practitioners in catalysis.

Sustainable Organic Synthesis

Download Sustainable Organic Synthesis PDF Online Free

Author :
Publisher : Royal Society of Chemistry
ISBN 13 : 1839162031
Total Pages : 602 pages
Book Rating : 4.8/5 (391 download)

DOWNLOAD NOW!


Book Synopsis Sustainable Organic Synthesis by : Dr Stefano Protti

Download or read book Sustainable Organic Synthesis written by Dr Stefano Protti and published by Royal Society of Chemistry. This book was released on 2021-10-29 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent years have seen huge growth in the area of sustainable chemistry. In order to meet the chemical needs of the global population whilst minimising impacts on health and the environment it is essential to keep reconsidering and improving synthetic processes. Sustainable Organic Synthesis is a comprehensive collection of contributions, provided by specialists in Green Chemistry, covering topics ranging from catalytic approaches to benign and alternative reaction media, and innovative and more efficient technologies.

Manganese Catalysis in Organic Synthesis

Download Manganese Catalysis in Organic Synthesis PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 3527347305
Total Pages : 372 pages
Book Rating : 4.5/5 (273 download)

DOWNLOAD NOW!


Book Synopsis Manganese Catalysis in Organic Synthesis by : Jean-Baptiste Sortais

Download or read book Manganese Catalysis in Organic Synthesis written by Jean-Baptiste Sortais and published by John Wiley & Sons. This book was released on 2021-12-20 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Manganese Catalysis in Organic Synthesis A must-read reference for anyone interested in catalyst design and sustainable organic synthesis In Manganese Catalysis in Organic Synthesis, distinguished researcher Jean-Baptiste Sortais delivers an insightful and robust overview of the use of manganese in homogenous catalysis. The editor includes papers from authoritative academics describing the organometallic precursors used to develop manganese catalysts and covers critical applications in organic synthesis, including reduction to oxidation reactions, C-C, C-N, C-X bond formation reactions, cross-coupling reactions, C-H bond activation to dihydroxylation and epoxidation reactions. Manganese Catalysis in Organic Synthesis is a practical resource for every organic chemist in academia and industry with an interest in non-noble metal catalysis, organic synthesis, and sustainable chemistry. It is intuitively and clearly organized, covering the most important synthetic procedures using homogenous manganese catalysts. It is also the ideal companion to works like Cobalt Catalysis in Organic Synthesis, Nickel Catalysis in Organic Synthesis, and Iron Complexes in Catalysis. Readers will also enjoy: Thorough introductions to organometallic manganese compounds in organic synthesis and manganese-catalyzed hydrogenation and hydrogen transfer reactions A comprehensive exploration of manganese-catalyzed hydrogen borrowing reactions and dehydrogenative coupling reactions Practical discussions of manganese-catalyzed hydrosilylation and hydroboration reactions and manganese-catalyzed electro- and photocatalysis transformations In-depth examinations of manganese-catalyzed C-H oxygenation reactions and manganese-catalyzed organometallic C-H activation Insightful treatments of manganese-catalyzed cross-coupling processes and manganese(III) acetate mediated cyclizations Perfect for catalytic, organic, and pharmaceutical chemists, Manganese Catalysis in Organic Synthesis deserves a place in the libraries of researchers and professionals interested in catalyst design and sustainable organic synthesis.

Modern Carbonyl Chemistry

Download Modern Carbonyl Chemistry PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 3527613277
Total Pages : 632 pages
Book Rating : 4.5/5 (276 download)

DOWNLOAD NOW!


Book Synopsis Modern Carbonyl Chemistry by : Junzo Otera

Download or read book Modern Carbonyl Chemistry written by Junzo Otera and published by John Wiley & Sons. This book was released on 2008-11-21 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: The carbonyl group is undoubtedly one of the most important functional groups in organic chemistry, both in its role as reactive center for synthesis or derivatisation and as crucial feature for special structural or physiological properties. Vast and profound progress has been made in all aspects modern carbonyl chemistry. These achievements are, however, rather dispersed in the literature and it is often not easy for the researcher obtain a comprehensive overview of a relevant topic. Modern Carbonyl Chemistry overcomes this inconvenience by collating the information for appropriate themes. In this work internationally renowned experts and leaders in the field have surveyed recent aspects and modern features in carbonyl chemistry, such as cascade-reactions, one-pot-syntheses, recognition, or site differentiation.

Hydrogen Transfer Reactions

Download Hydrogen Transfer Reactions PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 3319430513
Total Pages : 393 pages
Book Rating : 4.3/5 (194 download)

DOWNLOAD NOW!


Book Synopsis Hydrogen Transfer Reactions by : Gabriela Guillena

Download or read book Hydrogen Transfer Reactions written by Gabriela Guillena and published by Springer. This book was released on 2016-09-27 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.

C-X Bond Formation

Download C-X Bond Formation PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 3642120733
Total Pages : 198 pages
Book Rating : 4.6/5 (421 download)

DOWNLOAD NOW!


Book Synopsis C-X Bond Formation by : Arkadi Vigalok

Download or read book C-X Bond Formation written by Arkadi Vigalok and published by Springer. This book was released on 2010-06-30 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents: Kilian Muñiz: Transition Metal Catalyzed Electrophilic Halogenation of C-H bonds in alpha-Position to Carbonyl Groups; Arkadi Vigalok * and Ariela W Kaspi: Late Transition Metal-Mediated Formation of Carbon-Halogen Bonds; Paul Bichler and Jennifer A. Love*: Organometallic Approaches to Carbon-Sulfur Bond Formation; David S. Glueck: Recent Advances in Metal-Catalyzed C-P Bond Formation; Andrei N. Vedernikov: C-O Reductive Elimination from High Valent Pt and Pd Centers; Lukas Hintermann: Recent Developments in Metal-Catalyzed Additions of Oxygen Nucleophiles to Alkenes and Alkynes; Moris S. Eisen: Catalytic C-N, C-O and C-S bond formation promoted by organoactinide complexes.

Hydroformylation for Organic Synthesis

Download Hydroformylation for Organic Synthesis PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 3642450598
Total Pages : 233 pages
Book Rating : 4.6/5 (424 download)

DOWNLOAD NOW!


Book Synopsis Hydroformylation for Organic Synthesis by : Maurizio Taddei

Download or read book Hydroformylation for Organic Synthesis written by Maurizio Taddei and published by Springer. This book was released on 2014-07-08 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Role of Metals and Ligands in Organic Hydroformylation, by Luca Gonsalvi, Antonella Guerriero, Eric Monflier, Frédéric Hapiot, Maurizio Peruzzini. Hydroformylation in Aqueous Biphasic Media Assisted by Molecular Receptors, by Frédéric Hapiot, Hervé Bricout, Sébastien Tilloy, Eric Monflier. Asymmetric Hydroformylation, by Bernabé F. Perandones, Cyril Godard, Carmen Claver. Domino Reactions Triggered by Hydroformylation, by Elena Petricci, Elena Cini. Rhodium-Catalyzed Hydroformylation in Fused Azapolycycles Synthesis, by Roberta Settambolo. Hydroformylation in Natural Product Synthesis, by Roderick W. Bates, Sivarajan Kasinathan.

CO2 Hydrogenation Catalysis

Download CO2 Hydrogenation Catalysis PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 3527346635
Total Pages : 322 pages
Book Rating : 4.5/5 (273 download)

DOWNLOAD NOW!


Book Synopsis CO2 Hydrogenation Catalysis by : Yuichiro Himeda

Download or read book CO2 Hydrogenation Catalysis written by Yuichiro Himeda and published by John Wiley & Sons. This book was released on 2021-06-28 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: A guide to the effective catalysts and latest advances in CO2 conversion in chemicals and fuels Carbon dioxide hydrogenation is one of the most promising and economic techniques to utilize CO2 emissions to produce value-added chemicals. With contributions from an international team of experts on the topic, CO2 Hydrogenation Catalysis offers a comprehensive review of the most recent developments in the catalytic hydrogenation of carbon dioxide to formic acid/formate, methanol, methane, and C2+ products. The book explores the electroreduction of carbon dioxide and contains an overview on hydrogen production from formic acid and methanol. With a practical review of the advances and challenges in future CO2 hydrogenation research, the book provides an important guide for researchers in academia and industry working in the field of catalysis, organometallic chemistry, green and sustainable chemistry, as well as energy conversion and storage. This important book: Offers a unique review of effective catalysts and the latest advances in CO2 conversion Explores how to utilize CO2 emissions to produce value-added chemicals and fuels such as methanol, olefins, gasoline, aromatics Includes the latest research in homogeneous and heterogeneous catalysis as well as electrocatalysis Highlights advances and challenges for future investigation Written for chemists, catalytic chemists, electrochemists, chemists in industry, and chemical engineers, CO2 Hydrogenation Catalysis offers a comprehensive resource to understanding how CO2 emissions can create value-added chemicals.

Organometallic Chemistry and Catalysis

Download Organometallic Chemistry and Catalysis PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 3540461280
Total Pages : 598 pages
Book Rating : 4.5/5 (44 download)

DOWNLOAD NOW!


Book Synopsis Organometallic Chemistry and Catalysis by : Didier Astruc

Download or read book Organometallic Chemistry and Catalysis written by Didier Astruc and published by Springer Science & Business Media. This book was released on 2007-08-02 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume covers both basic and advanced aspects of organometallic chemistry of all metals and catalysis. In order to present a comprehensive view of the subject, it provides broad coverage of organometallic chemistry itself. The catalysis section includes the challenging activation and fictionalization of the main classes of hydrocarbons and the industrially crucial heterogeneous catalysis. Summaries and exercises are provides at the end of each chapter, and the answers to these exercises can be found at the back of the book. Beginners in inorganic, organic and organometallic chemistry, as well as advanced scholars and chemists from academia and industry will find much value in this title.

Applications of Metal-Organic Frameworks and Their Derived Materials

Download Applications of Metal-Organic Frameworks and Their Derived Materials PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 1119650984
Total Pages : 496 pages
Book Rating : 4.1/5 (196 download)

DOWNLOAD NOW!


Book Synopsis Applications of Metal-Organic Frameworks and Their Derived Materials by : Inamuddin

Download or read book Applications of Metal-Organic Frameworks and Their Derived Materials written by Inamuddin and published by John Wiley & Sons. This book was released on 2020-06-10 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal–organic frameworks (MOFs) are porous crystalline polymers con­structed by metal sites and organic building blocks. Since the discovery of MOFs in the 1990s, they have received tremendous research attention for various applications due to their high surface area, controllable mor­phology, tunable chemical properties, and multifunctionalities, including MOFs as precursors and self-sacrificing templates for synthesizing metal oxides, heteroatom-doped carbons, metal-atoms encapsulated carbons, and others. Thus, awareness and knowledge about MOFs and their derived nanomaterials with conceptual understanding are essential for the advanced material community. This breakthrough new volume aims to explore down-to-earth applications in fields such as bio­medical, environmental, energy, and electronics. This book provides an overview of the structural and fundamental properties, synthesis strate­gies, and versatile applications of MOFs and their derived nanomaterials. It gives an updated and comprehensive account of the research in the field of MOFs and their derived nanomaterials. Whether as a reference for industry professionals and nanotechnologists or for use in the classroom for graduate and postgraduate students, faculty members, and research and development specialists working in the area of inorganic chemistry, materials science, and chemical engineering, this is a must-have for any library.

Manganese Catalysis in Organic Synthesis

Download Manganese Catalysis in Organic Synthesis PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 3527826114
Total Pages : 368 pages
Book Rating : 4.5/5 (278 download)

DOWNLOAD NOW!


Book Synopsis Manganese Catalysis in Organic Synthesis by : Jean-Baptiste Sortais

Download or read book Manganese Catalysis in Organic Synthesis written by Jean-Baptiste Sortais and published by John Wiley & Sons. This book was released on 2021-08-31 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: Manganese Catalysis in Organic Synthesis A must-read reference for anyone interested in catalyst design and sustainable organic synthesis In Manganese Catalysis in Organic Synthesis, distinguished researcher Jean-Baptiste Sortais delivers an insightful and robust overview of the use of manganese in homogenous catalysis. The editor includes papers from authoritative academics describing the organometallic precursors used to develop manganese catalysts and covers critical applications in organic synthesis, including reduction to oxidation reactions, C-C, C-N, C-X bond formation reactions, cross-coupling reactions, C-H bond activation to dihydroxylation and epoxidation reactions. Manganese Catalysis in Organic Synthesis is a practical resource for every organic chemist in academia and industry with an interest in non-noble metal catalysis, organic synthesis, and sustainable chemistry. It is intuitively and clearly organized, covering the most important synthetic procedures using homogenous manganese catalysts. It is also the ideal companion to works like Cobalt Catalysis in Organic Synthesis, Nickel Catalysis in Organic Synthesis, and Iron Complexes in Catalysis. Readers will also enjoy: Thorough introductions to organometallic manganese compounds in organic synthesis and manganese-catalyzed hydrogenation and hydrogen transfer reactions A comprehensive exploration of manganese-catalyzed hydrogen borrowing reactions and dehydrogenative coupling reactions Practical discussions of manganese-catalyzed hydrosilylation and hydroboration reactions and manganese-catalyzed electro- and photocatalysis transformations In-depth examinations of manganese-catalyzed C-H oxygenation reactions and manganese-catalyzed organometallic C-H activation Insightful treatments of manganese-catalyzed cross-coupling processes and manganese(III) acetate mediated cyclizations Perfect for catalytic, organic, and pharmaceutical chemists, Manganese Catalysis in Organic Synthesis deserves a place in the libraries of researchers and professionals interested in catalyst design and sustainable organic synthesis.

Organic Reactions, Volume 101

Download Organic Reactions, Volume 101 PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 1119644747
Total Pages : 993 pages
Book Rating : 4.1/5 (196 download)

DOWNLOAD NOW!


Book Synopsis Organic Reactions, Volume 101 by :

Download or read book Organic Reactions, Volume 101 written by and published by John Wiley & Sons. This book was released on 2020-01-23 with total page 993 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 101st volume in this series for organic chemists in academia and industry presents critical discussions of widely used organic reactions or particular phases of a reaction. The material is treated from a preparative viewpoint, with emphasis on limitations, interfering influences, effects of structure and the selection of experimental techniques. The work includes tables that contain all possible examples of the reaction under consideration. Detailed procedures illustrate the significant modifications of each method.

Oxidative Cross-Coupling Reactions

Download Oxidative Cross-Coupling Reactions PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 3527681019
Total Pages : 240 pages
Book Rating : 4.5/5 (276 download)

DOWNLOAD NOW!


Book Synopsis Oxidative Cross-Coupling Reactions by : Aiwen Lei

Download or read book Oxidative Cross-Coupling Reactions written by Aiwen Lei and published by John Wiley & Sons. This book was released on 2016-08-12 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first handbook on this emerging field provides a comprehensive overview of transition metal-catalyzed coupling reactions in the presence of an oxidant. Following an introduction to the general concept and mechanism of this reaction class, the team of authors presents chapters on C-C cross-coupling reactions using organometallic partners, C-Heteroatom bond forming reactions via oxidative couplings, and C-H couplings via C-H activation. The text also covers such groundbreaking topics as recent achievements in the fields of C-C and C-X bond formation reactions as well as C-H activation involving oxidative couplings. With its novel and concise approach towards important building blocks in organic chemistry and its focus on synthetic applications, this handbook is of great interest to all synthetic chemists in academia and industry alike.

Catalysis without Precious Metals

Download Catalysis without Precious Metals PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 3527632409
Total Pages : 296 pages
Book Rating : 4.5/5 (276 download)

DOWNLOAD NOW!


Book Synopsis Catalysis without Precious Metals by : R. Morris Bullock

Download or read book Catalysis without Precious Metals written by R. Morris Bullock and published by John Wiley & Sons. This book was released on 2011-08-02 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written for chemists in industry and academia, this ready reference and handbook summarizes recent progress in the development of new catalysts that do not require precious metals. The research thus presented points the way to how new catalysts may ultimately supplant the use of precious metals in some types of reactions, while highlighting the remaining challenges. An essential copanion for organic and catalytic chemists, as well as those working with/on organometallics and graduate students. From the contents: * Catalysis Involving the H' Transfer Reactions of First-Row Transition Metals * Catalytic Reduction of Dinitrogen to Ammonia by Molybdenum Complexes * Molybdenum and Tungsten Catalysts for Hydrogenation, Hydrosilylation and Hydrolysis * Iron in Catalytic Alkene and Carbonyl Hydrogenation Reactions * Olefin Oligomerizations and Polymerizations Catalyzed by Iron and Cobalt Complexes * Cobalt and Nickel Catalyzed Reactions Involving C-H and C-N Activation Reactions * Development of Molecular Electrocatalysts for H2 Oxidation and Production Based on Inexpensive Metals * Nickel-Catalyzed Reductinve Couplings and Cyclizations * Copper-Catalyzed Ligand Promoted Ullmann-Type Coupling Reactions * Copper-Catalyzed Azide-Alkyne Cycloaddition * "Frustrated Lewis Pairs": A Metal-Free Strategy for Hydrogenation Catalysis