Handbook Of Green Chemistry

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Handbook of Green ChemistryVolume 2Heterogenous CatalysisVolume Edited byRobert H. Crabtree

Related TitlesWasserscheid, P., Welton, T. (eds.)Ionic Liquids in Synthesis2nd Edition2008ISBN: 978-3-527-31239-9Sheldon, R. A., Arends, I., Hanefeld, U.Green Chemistry and Catalysis2007ISBN: 978-3-527-30715-9Cornils, B., Herrmann, W. A., Muhler, M., Wong, C. - H. (eds.)Catalysis from A - ZA Concise Encyclopedia3rd Edition2007ISBN: 978-3-527-31438-6Loupy, A. (ed.)Microwaves in Organic Synthesis2nd Edition2006ISBN: 978-3-527-31452-2Kappe, C. O., Stadler, A., Mannhold, R., Kubinyi, H., Folkers, G. (eds.)Microwaves in Organic and Medicinal Chemistry2005ISBN: 978-3-527-31210-8

Edited byPaul T. AnastasHandbook of Green Chemistry –Green CatalysisVolume 2Heterogenous CatalysisVolume Edited by Robert H. Crabtree

Series EditorProf. Dr. Paul T. AnastasYale UniversityCenter for Green Chemistry & Green Engineering225 Prospect StreetNew Haven, CT 06520USAVolume EditorProf. Dr. Robert H. CrabtreeYale UniversityDepartment of Chemistry225 Prospect St.New Haven, CT 06520USAGraphiker: AdamAll books published by Wiley-VCH are carefullyproduced. Nevertheless, authors, editors, andpublisher do not warrant the information containedin these books, including this book, to be free oferrors. Readers are advised to keep in mind thatstatements, data, illustrations, procedural details orother items may inadvertently be inaccurate.Library of Congress Card No.:applied forBritish Library Cataloguing-in-Publication DataA catalogue record for this book is available from theBritish Library.Bibliographic information published bythe Deutsche NationalbibliothekThe Deutsche Nationalbibliothek lists thispublication in the Deutsche Nationalbibliografie;detailed bibliographic data are available on theInternet at http://dnb.d-nb.de.# 2009 WILEY-VCH Verlag GmbH & Co. KGaA,WeinheimHandbook of Green ChemistryISBN (12 volumes):978-3-527-31404-1Set 1 Green Catalysis 978-3-527-31577-2Volume 1: Homogeneous CatalysisSet 2 Green Solvents978-3-527-31574-1Volume 2: Heterogeneous CatalysisSet 3 Green Processes 978-3-527-31576-5Volume 3: BiocatalysisSet 4 Green Products 978-3-527-31575-8The cover picture contains images from CorbisDigital Stock (Dictionary) and PhotoDisc, Inc./GettyImages (Flak containing a blue liquid).All rights reserved (including those of translation intoother languages). No part of this book may bereproduced in any form – by photoprinting,microfilm, or any other means – nor transmitted ortranslated into a machine language without writtenpermission from the publishers. Registered names,trademarks, etc. used in this book, even when notspecifically marked as such, are not to be consideredunprotected by law.Typesetting Thomson Digital, Noida, IndiaPrinting betz-druck GmbH, DarmstadtBinding Litges & Dopf GmbH, HeppenheimCover Design Adam-Design, WeinheimPrinted in the Federal Republic of GermanyPrinted on acid-free paperISBN: 978-3-527-32497-2

VContentsAbout the Editors XIIIList of Contributors 12.2Zeolites in Catalysis 1Stephen H. BrownIntroduction 1The Environmental Benefits of Zeolite-enabled Processes 2General Process Considerations 5Zeolite Fundamentals 6Other Properties 7Number of Acid Sites 8Acid Strength 8Reaction Mechanisms 8Hydrocarbon Cracking 8Oligomerization and Alkylation 12Isomerization 14Transalkylation of Aromatics 15Hydrogen Transfer or Conjunct Polymerization 18Mass Transport and Diffusion 21Zeolite Shape Selectivity 22Mass Transport Discrimination of Product Molecules 22Molecular Sieving 23Molecular Orientation 23Transition State Stabilization 25Organic Reaction Centers 26Counter Ion Mobility 29Conclusions 29References 29Sol–Gel Sulfonic Acid Silicas as Catalysts 37Adam F. Lee and Karen WilsonIntroduction 37Preparation of Meso–structured Silica Sulfonic Acid Catalysts 38Handbook of Green Chemistry, Volume 2: Heterogeneous Catalysis. Edited by Robert H. CrabtreeCopyright Ó 2009 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 978-3-527-32497-2

.3.32.4Templating Methods 38Cationic/Anionic Templates 38Neutral Templates 39Organically Functionalized Silica 39Characterization 40Grafting Methods 42Direct Preparation Methods 43Acid Strength of Sulfonic Acid Catalysts 44Phenyl- Versus Propylsulfonic Acids 45Fine Tuning the Catalytic Activity of Sulfonic Acid SilicasCooperative Effects 46Effect of Spectator Groups 48Application in Organic Transformations 49Condensation and Esterification 49Electrophilic Aromatic Substitution 51Miscellaneous Reactions 52Conclusions and Future Prospects 53References 553Applications of Environmentally Friendly TiO2 Photocatalysts inGreen Chemistry: Environmental Purification and Clean EnergyProduction Under Solar Light Irradiation 59Masaya Matsuoka and Masakazu AnpoIntroduction 59Principles of Photocatalysis 61Application of Photocatalysts in Green Chemistry: Solar EnergyConversion and Environmental Protection 62Water Splitting to Produce Pure Hydrogen as Clean Fuel 62Photocatalytic Reduction of CO2 with H2O (ArtificialPhotosynthesis) 64Direct Photocatalytic Decomposition of NO into N2 and O2 67Application to the Purification of Air Polluted with VariousOrganic Compounds 70Application to the Purification of Water Polluted with ToxicCompounds Such as Dioxins 71Superhydrophilic Properties of TiO2 Thin Films and TheirApplication in Self-cleaning Materials 72Development of Visible Light-responsive TiO2 Photocatalysts 73Modification of the Electronic State of TiO2 by Applying anAdvanced Metal Ion Implantation Method 73Design of Visible Light-responsive Ti/Zeolite Catalysts byApplying an Advanced Metal Ion Implantation Method 75Preparation of Visible Light-responsive TiO2 Thin-filmPhotocatalysts by an RF Magnetron Sputtering DepositionMethod .4.23.4.346

Contents3.5Conclusion 79References 794Nanoparticles in Green Catalysis 81Mazaahir KidwaiIntroduction 81Advanced Catalysis by Gold Nanoparticles 81Nickel Nanoparticles: a Versatile Green Catalyst 85Copper Nanoparticles: an Efficient Catalyst 87Bimetallic Nanoparticles in a Variety of Reactions 89References 3.16.3.26.46.4.16.4.1.16.4.1.2 Heterogreeneous Chemistry 93Heiko JacobsenIntroduction 93 Heterogreeneous Catalysis 96An Exemplarily Reaction – Catalysts for Hydrogen Productionfrom Biomass-Derived Hydrocarbons 97Transportation Fuels from Biomass – Catalytic Processing ofBiomass-derived Reactants 100Diesel Fuels from Biomass – Heterogreeneous Processes forBiodiesel Production 103Other Heterogreeneous Aspects of Catalysis 106Solid and Solid Acid Catalysts 106Recycling Catalysts 107One-pot Catalysis 108Photocatalysis 108Solvents for Green Catalysis 108Heterogreeneous Solvent Systems 109Solvent-free Heterogreeneous Chemistry 112Conclusion and Outlook 113References 114Single-site Heterogeneous Catalysts via Surface-boundOrganometallic and Inorganic Complexes 117Christophe CopéretIntroduction 117Generalities 117Hydrogenation and Hydrosilylation 119Hydrogenation 119Hydrosilylation 123Metathesis and Homologation Processes of Alkenes 124Alkene Metathesis 124Silica-supported Catalysts 124Alumina-supported Catalysts 127VII

.27.47.57.67.6.17.6.27.6.37.7Other Alkene Homologation Processes 128Direct Conversion of Ethene into Propene 128Cyclization of Dienes 129Metathesis, Dimerization, Trimerization and Other ReactionsInvolving Alkynes 129Alkyne Metathesis 129Dimerization and Trimerization of Alkynes 130Hydroamination of Alkynes 131Lewis Acid-catalyzed Reactions 131Silica-supported Group 4 Metals 131Reduction of Ketones Through Hydrogen Transfer 133Transesterification of Esters 134Silica-supported Group 3 Metals and Lanthanides 134Oxidation 135Single-site Titanium Species 135Single-site Zirconium Species 137Single-site Vanadium Species 137Single-site Tantalum Species 137Single-site Group 6 Species 138Single-site Iron Species 139Single-site Cobalt Species 141Alkane Homologation 141Alkane Hydrogenolysis 141Alkane Metathesis 143Alkane Cross-metathesis 146References 146Sustainable Heterogeneous Acid Catalysis by HeteropolyAcids 153Ivan KozhevnikovIntroduction 153Development of HPA Catalysts Possessing High ThermalStability 156Modification of HPA Catalysts to Enhance CokeCombustion 157Propene Oligomerization 158Friedel–Crafts Acylation 159Inhibition of Coke Formation on HPA Catalysts 161Reactions in Supercritical Fluids 163Cascade Reactions Using Multifunctional HPA Catalysts 165Synthesis of MIBK 166Hydrogenolysis of Glycerol to Propanediol 167Synthesis of Menthol from Citronellal 170Conclusion 172References 172

4.39.59.5.19.5.29.69.6.19.6.29.6.39.71010.1The Kinetics of TiO2-based Solar Cells Sensitized by Metal Complexes 175Anthony G. Fitch, Don Walker, and Nathan S. LewisIntroduction 175History 176DSSC Design 177Function of the DSSC 178Performance of a DSSC 179Kinetics Processes 180Charge Injection 181Recombination to the Dye 184Regeneration 187Conclusion 190References 192Automotive Emission Control: Past, Present and Future 197Robert J. Farrauto and Jeffrey HokeIntroduction 197The First Oxidation Catalysts (1975–80) 198Pollution Abatement Reactions for Gasoline-Fueled Engines 198Catalyst Materials 199Carriers 201Three-Way Catalysis (1980–present) 202Three-Way Catalysis 202Oxygen or Lambda Sensor 203Oxygen Storage Component 203Further Improvements in TWC 204Diesel Catalysis 206Controlling Diesel Emissions 206Diesel Emissions 207Diesel Oxidation Catalysts (DOCs): the Past 208Diesel Emission Control: the Future 210Catalytic Solutions for the Existing Diesel IC Engine 210The Homogeneous Charge Compression Ignition Engine (HCCI)and Advanced Engine Technology 213Fuel Cells and the Hydrogen Economy for TransportationApplications: the Future 217The Fuel Cell 217Fuel Cells for Transportation 218The Hydrogen Service Station 219Conclusions 220References 220Heterogeneous Catalysis for Hydrogen ProductionMorgan S. Scott and Hicham IdrissIntroduction 223223IX

2.610.2.710.310.3.110.3.210.3.310.3.410.4Renewable Energy 224Hydrogen 225Hydrogen from Ethanol Decomposition 226Catalytic Oxidation 228Steam Reforming 228Dry Reforming 229Water Gas Shift Reaction (WGSR) 229Catalytic Reforming of Methane 230Thermodynamics 230Catalysis 231The Noble Metals Pd and Rh 232Structure and Properties of Cerium Dioxide 233Noble Metal/Ceria Catalysts 235Adsorption of Ethanol 236Adsorption of Water 236Adsorption of Carbon Oxides 237Hydrides 237Catalytic Decomposition of Ethanol 238Ethanol on Metal Oxides 238Ethanol on a Noble Metal/Ceria Surface 239Catalytic Oxidation of Ethanol 242Catalytic Reforming of Ethanol 243Conclusions 244References 24511High-Throughput Screening of Catalyst Libraries for EmissionsControl 247Stephen Cypes, Joel Cizeron, Alfred Hagemeyer, and Anthony VolpeIntroduction 247Introduction to High-Throughput Heterogeneous Catalysis 247The Hierarchical Workflow in Heterogeneous Catalysis 248Applications to Green Chemistry 249Experimental Techniques and Equipment 250Overview of Hardware and Methodologies for CombinatorialHeterogeneous Catalysis 250Experimental High-Throughput Workflow for Low-TemperatureCO Oxidation and VOC Combustion 259Primary Synthesis Methods 260Secondary Synthesis Methods 260IR Thermography Reactor 261Multi-Channel Fixed-bed Reactor 263Experimental High-Throughput Workflow for NOx Abatement 263Primary Synthesis Methods 263Primary Screening Methods 263Data Analysis for NOx Abatement from SMS 3.3

.5.1Low-Temperature CO Oxidation and VOC Combustion 265NOx Abatement 273Conclusion 277Application of High-Throughput Screening to EmissionsControl 277Future Trends in Combinatorial Catalysis 278References 278Catalytic Conversion of High-Moisture Biomass to SyntheticNatural Gas in Supercritical Water 281Frédéric VogelIntroduction 281Heterogeneous Catalysis in Hydrothermal Medium at theOrigin of Life? 281Biomethane – a Green and Sustainable Fuel 282Energetic Potentials 283Nutrient Cycles 284Survey of Different Technologies for the Production of Methanefrom Carbonaceous Feedstocks 285Anaerobic Digestion 285Thermal Processes 286Water as Solvent and Reactant 288Solubility of Organic compounds and Gases 289Solubility of Salts 290The Role of Heterogeneous Catalysis 290Experimental Methods 290Thermodynamic Stability of Methane under HydrothermalConditions 291Main Reactions of Biomass Gasification 293Homogeneous, Non-catalyzed Pathways in HotCompressed Water 294Heterogeneously Catalyzed Pathways in Hot CompressedWater 297Active Metals Suited to Hydrothermal Conditions 298Methanation and Steam Reforming Catalysts 299Nickel 302Ruthenium 305Catalyst Supports Suited to Hydrothermal Conditions 306Deactivation Mechanisms in a Hydrothermal Environment 312Coke Formation 312Sintering 314Poisoning 314Continuous Catalytic Hydrothermal Process for the Productionof Methane 315Overview of Processes 315XI

XIIContents12.5.212.5.2.112.5.2.212.612.712.7.1PSI s Catalytic Hydrothermal Gasification Process 315Continuous Salt Precipitation and Separation 316Status 318Summary and Conclusions 318Outlook for Future Developments 319A Self-sustaining Biomass Vision (SunCHem) 319References 320Index325

XIIIAbout the EditorsSeries EditorPaul T. Anastas joined Yale University as Professor and servesas the Director of the Center for Green Chemistry and GreenEngineering there. From 2004–2006, Paul was the Director ofthe Green Chemistry Institute in Washington, D.C. UntilJune 2004 he served as Assistant Director for Environmentat the White House Office of Science and Technology Policywhere his responsibilities included a wide range of environmental science issues including furthering internationalpublic-private cooperation in areas of Science for Sustainability such as Green Chemistry. In 1991, he established the industry-governmentuniversity partnership Green Chemistry Program, which was expanded to includebasic research, and the Presidential Green Chemistry Challenge Awards. He haspublished and edited several books in the field of Green Chemistry and developedthe 12 Principles of Green Chemistry.Volume EditorRobert Crabtree took his first degree at Oxford, did his Ph.D.at Sussex and spent four years in Paris at the CNRS. He hasbeen at Yale since 1977. He has chaired the Inorganic Divisionat ACS, and won the ACS and RSC organometallic chemistryprizes. He is the author of an organometallic textbook, and isthe editor-in-chief of the Encyclopedia of Inorganic Chemistryand Comprehensive Organometallic Chemistry. He has contributed to C-H activation, H2 complexes, dihydrogen bonding, and his homogeneous tritiation and hydrogenationcatalyst is in wide use. More recently, he has combined molecular recognitionwith CH hydroxylation to obtain high selectivity with a biomimetic strategy.Handbook of Green Chemistry, Volume 2: Heterogeneous Catalysis. Edited by Robert H. CrabtreeCopyright Ó 2009 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 978-3-527-32497-2

XVList of ContributorsMasakazu AnpoOsaka Prefecture UniversityGraduate School of EngineeringDepartment of Applied ChemistryGakuen-chi, 1-1SakaiOsaka 599-8531JapanStephen H. BrownEMRE CSR1545 Route 22 EastAnnandale, NJ 08801USAJoel CizeronSymyx Technologies, Inc.3100 Central ExpresswaySanta Clara, CA 95051USAChristophe CopéretUniversité de LyonInstitut de Chimie de LyonLaboratoire C2P2 – ESCPE Lyon43 boulevard du 11 Novembre 191869616 VilleurbanneFranceStephen CypesSymyx Technologies, Inc.3100 Central ExpresswaySanta Clara, CA 95051USARobert J. FarrautoBASF Catalysts25 Middlesex–Essex TurnpikeIselin, NJ 08830USAAnthony G. FitchCalifornia Institute of TechnologyDivision of Chemistry and ChemicalEngineeringBeckman Institute and KavliNanoscience Institute210 Noyes Laboratory, 127–72Pasadena, CA 91125USAAlfred HagemeyerSüd-Chemie AGWaldheimer Strasse 1383052 BruckmühlGermanyJeffrey HokeBASF Catalysts25 Middlesex–Essex TurnpikeIselin, NJ 08830USAHandbook of Green Chemistry, Volume 2: Heterogeneous Catalysis. Edited by Robert H. CrabtreeCopyright Ó 2009 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 978-3-527-32497-2

XVIList of ContributorsHicham IdrissUniversity of AberdeenDepartment of ChemistryMeston WalkAberdeen, AB24 3EUUKHeiko JacobsenKemKom1215 Ursulines AvenueNew Orleans, LA 70116USAMazaahir KidwaiUniversity of DelhiDepartment of ChemistryGreen Chemistry Research LaboratoryDelhi 110007IndiaIvan KozhevnikovDepartment of ChemistryUniversity of LiverpoolLiverpool L69 7ZDUKAdam F. LeeUniversity of YorkDepartment of ChemistrySurface Chemistry and Catalysis GroupHeslingtonYork YO10 5DDUKNathan S. LewisCalifornia Institute of TechnologyDivision of Chemistry and ChemicalEngineeringBeckman Institute and KavliNanoscience Institute210 Noyes Laboratory, 127–72Pasadena, CA 91125USAMasaya MatsuokaOsaka Prefecture UniversityGraduate School of EngineeringDepartment of Applied ChemistryGakuen-chi, 1-1SakaiOsaka 599-8531JapanMorgan S. ScottUniversity of AucklandDepartment of ChemistryPrivate Bag 92019AucklandNew ZealandFrédéric VogelPaul Scherrer InstitutLaboratory for Energy and MaterialsCycles5232 Villigen PSISwitzerlandAnthony Volpe JrSymyx Technologies Inc.3100 Central ExpresswaySanta Clara, CA 95051USADon WalkerCalifornia Institute of TechnologyDivision of Chemistry and ChemicalEngineeringBeckman Institute and KavliNanoscience Institute210 Noyes Laboratory, 127–72Pasadena, CA 91125USA

List of ContributorsKaren WilsonUniversity of YorkDepartment of ChemistrySurface Chemistry and Catalysis GroupHeslingtonYork YO10 5DDUKXVII

j11Zeolites in CatalysisStephen H. Brown1.1IntroductionAcid catalysis as a modern science is less than 150 years old. From its inception, acidcatalysis has been explored as a means of producing fuels, lubes and petrochemicals.Ordinary homogeneous acids, both inorganic and organic, never proved industriallyuseful at temperatures much above 150 C. The first reports of aluminosilicate solidacid catalysts involved the use of clays after the turn of the century. The inspiration forthe first commercial synthetic aluminosilicate catalysts came from work done coprecipitating silicon and aluminum salts during WWI by a Sun Oil chemist [1]. TheBrønsted acid site in these materials is most often represented as in Scheme 1.1.Useful features of this novel type of acid versus homogeneous liquid acids were theirhigh temperature stability, moderate acidity (roughly equivalent to a 50% sulfuricacid solution), solid and non-corrosive character and regenerability by air oxidation.These features enabled acid catalyzed reactions of chemicals to be contemplated at agreatly extended range of temperatures (up to 600 C) and metallurgies.Scheme 1.1 The Brønsted acid site of an aluminosilicate.The first embodiments of many modern refining processes including heavy oilcracking, naphtha reforming and light gas oligomerization did not use catalysts [2].As soon as these thermal processes commercialized, exploration of the use of solidacid catalysts ensued naturally.Because of the key role played in the development of the automotive industry, heavyoil cracking to gasoline provided a focal point for the early development of heterogeneous acid catalysis. Temperatures above 400 C and pressures below 3 atmospheresare thermodynamically favorable for the conversion of heavy oils to light hydrocarbons rich in olefins. Acceptable heavy oil cracking rates are achieved without aHandbook of Green Chemistry, Volume 2: Heterogeneous Catalysis. Edited by Robert H. CrabtreeCopyright 2009 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 978-3-527-32497-2

j 1 Zeolites in Catalysis2catalyst at temperatures above 600 C. This was the basis of the thermal crackingprocess. Thermal cracking produces high yields of methane and aromatic hydrocarbons. The goal of researchers was to find a catalyst that could crack heavyhydrocarbons selectively to gasoline with only minimal formation of gases withmolecular weights of less than 30. Due to thermodynamic constraints, the catalysthad to be effective at a temperature above 400 C. In order to avoid unselectivethermal cracking, the catalyst had to be effective below 550 C.The discovery in the early 1920s by Houdry that acid activated clays were active andselective in this temperature window was a breakthrough [2]. In the 1930s and 1940smethods were developed and commercialized to produce high surface area manmade aluminosilicates that were significantly improved catalysts. Examination of thealuminosilicate catalysts led to the understanding that the active site was a Brønstedacid [3].At the time of the discovery of synthetic zeolites in the early 1950s, only two classesof solid Brønsted acids (solid phosphoric acid and aluminosilicates) were being usedcommercially to produce commodity fuels or petrochemicals [4]. The commercialization of silica-rich synthetic zeolites in their hydrogen form represented a breakthrough for scientists and organizations interested in the production of fuels, lubesand petrochemicals at temperatures above 200 C. Like amorphous aluminosilicates,zeolite Brønsted acid sites are active and stable up to 600 C. Shortly after UnionCarbide s discovery of synthetic zeolites in the late 1940s, Mobil Oil researchers incatalytic cracking of heavy oil investigated zeolites as potential catalysts [5]. Thezeolite known as faujasite (FAU) was found to be three to five orders of magnitudemore active than amorphous aluminosilicates. Unmodified, FAU was too active tobe useful. When the activity of FAU was tuned by ion exchange with rare earth cationsand/or by reducing aluminum content, it was found to have a dramatically differentselectivity to cracked products. Optimized samples of FAU zeolites produced almost5% less C2-gases and coke and increased gasoline yields by more than 10 wt%. Overthe course of the past 50 years, evolving heavy oil cracking catalysts and hardwarehave been continuously decreasing coke and C2-gas yields while increasing the yieldof gasoline.The commercialization of zeolite catalysts for heavy oil cracking unleashed thecreative abilities of every organization interested in producing fuels and petrochemicals using acid catalysts between 250 and 600 C. Close to 23 processes have beencommercialized (Table 1.1). About two-thirds of the processes had no real precedenceusing homogeneous acids. The other third involved displacement of homogeneousand amorphous acid catalysts. Introduction of zeolite catalysts for the production ofcommodities has proceeded at a steady pace. Each commercialization has providedan opportunity for zeolite scientists to find improved catalysts.1.1.1The Environmental Benefits of Zeolite-enabled ProcessesThe petroleum industry has been subject to environmental drivers for manydecades [6]. Innovations in technology, some driven by more restrictive regulations,

1.1 IntroductionTable 1.1 List of zeolite processes.ProcessReactor typeTemperature range, CToluene þ C9 þ aromaticsMSTDPCumene via transalkylationEthylbenzene via transalkylationEthylbenzeneCumeneFluid catalytic cracking (FCC)ZSM-5 in FCCGasoil hydrocrackingDistillate hydrocrackingDistillate dewaxingWax hydrocrackingWax hydroisomerizationGasoline octane enhancementReformate upgradingLight paraffin isomerizationButene isomerizationXylene isomerizationLight paraffin aromatizationMethanol to gasolineMethanol to olefinsAromatics feed –550300–400400–500150–250350–450have continuously increased the efficiency of refining processes. The trend is toproduce fuels having lower concentrations of heteroatoms and polynuclear aromatics(often referred to as clean fuels) that can be burned to carbon dioxide and water withincreasingly lower emissions of NOx, SOx and particulate byproducts.For decades, nearly the entire hydrocarbon content of a barrel of oil feeding arefinery or petrochemical complex has been converted to salable products or used forfuel at the manufacturing site. Distillation of crude oil largely splits it into streamswith the boiling ranges of the fuels sold to consumers and businesses (gasoline,diesel, fuel oil, etc.). The quantities of the streams produced by distillation rarelymatch market demand. Processes using zeolite catalysts have reduced the effortrequired to convert streams that are oversupplied by simple crude oil distillation intoundersupplied products. Optimized zeolite catalyzed processes are often hightechnology operations. Performance can be sensitive to the performance of neighboring units. Operating multiple zeolite-catalyzed processes can provide refinerswith an incentive to continuously work to bring the refinery closer to steady stateoperation. Adoption of these high technology processes and work practices hashelped refiners to steadily increase the amount of clean fuel products produced fromeach barrel of oil, thereby reducing emissions of CO2, NOx, SOx and particulates andincreasing energy efficiency.j3

j 1 Zeolites in Catalysis4Zeolite catalysts are remarkably efficient. Each weight unit of zeolite producesbetween 3000 and 500 000 weight units of fuel or petrochemical product before itslifetime ends and it is removed from catalyst service. As a result, relatively smallvolumes of spent zeolite catalysts are produced. There are often other uses for spentcatalysts, such as an ingredient for cement. In the many cases where reuse is anoption, there are little/no catalyst waste disposal costs.Catalytic cracking (also known as fluid catalytic cracking or FCC) is by far the mosteconomically important process in the refining and petrochemicals industry and willbe described in some detail to allow the green aspects to be highlighted. World wide,FCC units process almost 20 million bbl/day of feedstock (almost 30% of the crude oilproduced) and FCC catalysts generate 1 billion in sales [7]. The remarkableperformance of the FCC process is achieved by both optimizing the zeolite catalystand the reactor design. A schematic of an FCC unit is provided in Figure 1.1.The FCC catalyst spends most of its time in a large, cylindrical regeneration vesseltypically 15 meters in diameter and 40 meters tall holding 300 tons of a coarse powdercatalyst comprised of a bell-shaped distribution of spheres between 15 and 120microns in diameter. The vessel is typically held at 15–25 psig and 620 to 700 C. Air iscontinuously blown up from the bottom of the vessel and is carefully distributed toprovide uniform contacting with the solids. When properly engineered, up flowinggases mix with the coarse catalyst powder to form a mixture which behaves like afluid. The reaction carried out in the regeneration vessel is the combustion of thesolid carbonaceous reaction byproducts that accumulate on the catalyst during thecracking reaction. The FCC catalyst enters the isothermal, back-mixed regenerator atthe reaction temperature (about 550 C) and is heated to the regenerator temperatureby the heat of combustion of the coke.Because of its fluid-like properties in the presence of a flowing gas stream, thecatalyst will flow smoothly out of the bottom of the regenerator, up a 2 meter diameterFigure 1.1 FCC reactor process flow diagram.

1.2 General Process Considerationspipe (called a riser) where it contacts the heavy oil feedstock and then back into the topof the regeneration vessel. A typical catalyst circulation rate for a unit filled with 300tons of catalyst would be 3000 tons/hour. An average catalyst particle travels throughthe riser once every 5 or 6 minutes. Heavy oil feedstock is heated to about 300 C andsprayed into the circulating catalyst (620 to 700 C) at the bottom of the riser. Feedvaporization is accomplished by direct contact with the hot zeolite catalyst. Thegaseous product is removed utilizing cyclones at the top of the riser. Feedstock istypically fed into the riser at twice the total catalyst inventory and one fifth the catalystcirculation rate (e.g. catalyst circulation of 3000 tons/h and a feed throughput of600 tons/h). The total time of feedstock and catalyst contact is several seconds. About5 wt% of the feedstock (no more, no less) must be converted to the carbonaceoussolids (coke) that are required to provide the energy input needed to drive thefeedstock vaporization and the endothermic reaction. A typical catalyst particlecontains about 1 wt% coke on catalyst upon entering the regenerator.Thirty to fifty percent of a barrel of crude oil boils above the endpoint of gasolineand automotive diesel fuels. The FCC unit converts much of this material intogasoline and diesel fuels with roughly 80 wt% selectivity. Another 5 to 10% of the C4products are easily converted into high quality gasoline in a second step, resulting inan overall selectivity to gasoline and diesel fuels of 85 to 90%. Five wt% of the feed isconverted to coke which is used to supply most of the fuel for the unit (regenerat

Handbook of Green Chemistry ISBN (12 volumes): 978-3-527-31404-1 Set 1 Green Catalysis 978-3-527-31577-2 Volume 1: Homogeneous Catalysis Set 2 Green Solvents 978-3-527-31574-1 Volume 2: Heterogeneous Catalysis Set 3 Green Processes 978-3-527-31576-5 Volume 3: Biocatalysis Set 4 Green Product