HANDBOOK SECOND EDITION Edited by Martyn V. Twigg BSc, PhD, CChem., FRSC Catalytic Systems Division Johnson Matthey Plc. Formerly at the Catalysis Centre ICI Chemicals & Polymers Ltd MANSON PUBLISHING
Preface 16 Chapter 1. Fundamental Principles M.S. Spencer 1.1. Fundamentals of Heterogeneous Catalysis 17 1.1.1. Introduction 17 1.1.2. The Roleof Catalysis 18 1.1.2.1. Ammonia Synthesis 18 1.1.2.2. Ammonia Oxidation 19 1.1.3. The Nature of the Catalytic Process 23 1.1.4. Catalyst Activity 24 1.1.5. Catalyst Selectivity 26 1.1.6. Steps in the Catalytic Process 27 1.1.7. Adsorption and Desorption 29 1.1.8. Catalyst Design 32 1.2. Catalyst Manufacture 34 1.2.1. Introduction 34 1.2.2. Unsupported Metals 34 1.2.3. Fused Catalysts 35 1.2.4. Wet Methods of Catalyst Manufacture 37 1.2.5. Fundamentals of Precipitation Processes 38 1.2.6. Catalyst Manufacture by Precipitation Processes 40 1.2.7. Impregnation Processes 41 1.2.8. Forming Stages 43 1.3. Catalyst Testing 48 1.3.1. Introduction 48 1.3.2. Chemical and Physical Properties 49 1.3.3. Bulk Chemical Properties 49 1.3.4. Surface Chemical Properties 50 1.3.5. Physical Properties 52 1.3.6. Catalyst Performance 55 1.3.7. Coarse Laboratory Screening 56 1.3.8. Fine Laboratory Screening 58 1.3.9. Semi-technical Catalyst Testing 60 1.3.10. Reaction Kinetics 61 1.3.11. Catalyst Ageing 65 1.3.12. Mechanism of the Catalytic Reaction 66
1.3.12.1. Ammonia Synthesis 67 1.3.12.2. Methanol Synthesis 68 1.4. Catalyst in Use 69 1.4.1. Introduction 69 1.4.2. Pretreatment and Activation 69 1.4.3. Loss of Catalyst Performance 73 1.4.4. Physical Causes of Decay 76 1.4.5. Poisoning by Impurities in Feeds or Catalysts 77 1.4.6. Poisoning by Reactants or Products 81 1.4.7. Interactions in Catalyst Deactivation 82 Chapter2. Process Design, Rating and Performance W.J. Lywood 2.1. Design of Catalytic Reactors 85 2.1.1. Operating Temperature and Pressure 87 2.1.1.1. Desulphurization Reactor 87 2.1.1.2. Steam Reformers 87 2.1.1.3. Water-gas Shift Reactors 88 2.1.1.4. Methanation Reactor 89 2.1.1.5. Ammonia and Methanol Synthesis Reactors 89 2.1.2. Converter Types 90 2.1.2.1. Single Adiabatic Bed 90 2.1.2.2. Quench Converter 91 2.1.2.3. Inter-bed Cooling 91 2.1.2.4. ICI High-conversion Reactor 96 2.1.2.5. Tube-cooled Reactor 96 2.1.2.6. Steam-raising Reactor 96 2.1.3. Catalyst Life 96 2.1.4. Optimum Catalyst Size and Shape 101 2.1.4.1. Voidage 101 2.1.4.2. Catalyst Particle Size 103 2.1.5. Design Conversion of Reactor 105 2.1.6. Calculation of Catalyst Volume 107 2.1.6.1. Catalyst Volume for Low concentration Reactant Being Removed 107 2.1.6.2. Catalyst Volume for Low concentration Product Being Formed 108 2.1.6.3. Equilibrium Concentrations 109 2.1.6.4. Rate Constants 119 2.1.7. Vessel Dimensions 119 2.2. Reactor Rating 121
2.2.1. Optimum Operating Temperature 121 2.3. Catalyst Performance 123 2.3.1. Fall in Apparent Catalyst Activity 123 2.3.1.1. Poisoning/Sintering 123 2.3.1.2. Poor Gas Distribution 124 2.3.1.3. Poor Mixing of Reactants 124 2.3.2. Increase in Pressure Drop 125 2.3.2.1. Breakage or Erosion of Catalyst Particles 125 2.3.2.2. Disintegration of Catalyst Particles 125 2.3.2.3. Deformation of Catalyst Particles 126 2.3.2.4. Carry-over onto Catalyst Bed 126 2.3.2.5. Collapse of Bed Support 126 2.3.3. Measurement of Performance 126 2.3.3.1. Analysis 126 2.3.3.2. Mass Balance 127 2.3.3.3. Catalyst-bed Temperature Rises 127 2.3.3.4. Catalyst-bed Temperature Profiles 127 2.3.3.5. Radioactive Tracing 127 2.3.3.6. Pressure Drop 127 2.3.4. Quantifying Catalyst Performance 127 2.3.4.1. Composition at the Exit from the Reactor 128 2.3.4.2. Approach to Equilibrium 128 2.3.4.3. Activity or Active Volume of Catalyst 128 2.3.5. Calculation of Catalyst Performance 128 2.3.5.1. Reactor Exit Composition 129 2.3.5.2. Calculation of Approach to Equilibrium 130 2.3.5.3. Calculation of Activity or Active Volume from Composition 132 2.3.5.4. Calculation of Activity or Active Volume from Temperature Profiles 133 2.3.6. Application of Methods to Ammonia and Methanol Catalysts 134 2.3.6.1. Desulphurizer 135 2.3.6.2. Primary and Secondary Reformer 135 2.3.6.3. High Temperature Shift 136 2.3.6.4. Low Temperature Shift 136 2.3.6.5. Methanator 136 2.3.6.6. Ammonia and Methanol Synthesis Converter 137 2.4. Computer Programs 137 2.4.1. Reasons for Using Computer Calculations 137 2.4.1.1. Accurate Calculations 137 2.4.1.2. Non-isothermal Reactors 138 2.4.1.3. Multiple Reactions 138 2.4.1.4. Optimization 138 2.4.1.5. Simulation 138 2.4.2. Types of Computer Programs 138
Chapter3. Handling and Using Catalysts in the Plant D.R. Goodman 3.1. Introduction 140 3.2. Catalyst Storage 140 3.3. Drum Handling 141 3.4. Intermediate Bulk Containers and Socks 142 3.5. Sieving Catalyst 149 3.6. Catalyst Charging 150 3.6.1. Pre-charging Checks 150 3.6.2. Charging Vessels 151 3.6.3. Charging Ammonia Converters 155 3.6.4. Charging Reformer Tubes 156 3.7. Catalyst Reduction 161 3.7.1. Reduction of Reforming Catalyst 162 3.7.1.1. Typical Reduction with Steam and Natural Gas 163 3.7.1.2. Reduction with Gas Recirculation 164 3.7.2. Reduction of High-temperature Shift Catalyst 165 3.7.2.1. Typical Reduction of High-temperature Shift Catalyst 166 3.7.3. Reduction of Low-temperature Shift Catalyst 166 3.7.3.1. Typical Reduction of Low-temperature Shift Catalyst 170 3.7.4. Reduction of Methanation Catalyst 171 3.7.5. Reduction of Ammonia Synthesis Catalyst 171 3.7.5.1. Typical Reduction of a Tube-cooled Ammonia Converter 173 3.7.5.2. Typical Reduction of a Multibed Quench Converter... 174 3.8. Catalyst Shutdown and Restarts 175 3.9. Catalyst Regeneration 176 3.9.1. Regeneration of Reforming Catalyst 176 3.9.2. Regeneration of High-temperature Shift Catalyst 177 3.9.3. Regeneration of Low-temperature Shift Catalyst 177 3.9.4. Washing of Methanation Catalyst 177 3.9.5. Regeneration of Ammonia Synthesis Catalyst 178 3.10. Blanketing of Reduced Catalyst 178 3.11. Catalyst Stabilization 179 3.11.1. Stabilization of Reforming Catalyst 180 3.11.2. Stabilization of High-temperature Shift Catalyst 180
3.11.3. Stabilization of Low-temperature Shift Catalyst 181 3.11.4. Stabilization of Methanation Catalyst 182 3.11.5. Stabilization of Ammonia Synthesis Catalyst 183 3.12. Catalyst Discharge 183 3.12.1. General 183 3.12.2. Discharge of Pyrophoric Catalyst 184 3.12.3. Top Discharge 185 3.12.4. Blanketing Pyrophoric Catalyst During Vacuum Extraction.. 186 3.12.5. Discharge of Ammonia Synthesis Catalyst 186 3.13. Re-use of Discharged Catalyst 187 3.14. Disposal of Used Catalyst 188 3.15. Safety Precautions 188 Chapter 4. Feedstock Purification P.J.H. Carnell 4.1. Introduction 191 4.2. Feedstocks for Ammonia, Methanol and Hydrogen Production 192 4.2.1. Natural Gas 192 4.2.2. Associated Gas, Natural Gas Condensates and LPG 193 4.2.3. Naphtha 194 4.2.4. Refinery Off Gases and Electrolytic Hydrogen 194 4.2.5. Coal Gasification and Coke Oven Gas 194 4.2.6. Mixed Feeds 195 4.3. Desulphurization 196 4.3.1. Processes for Single-stage Sulphur Removal 196 4.3.2. Processes fortwo-stage Sulphur Removal 198 4.4. Thermal Dissociation of Sulphur Compounds 199 4.5. Hydrogenolysis of Sulphur Compounds 200 4.6. Carbonyl Sulphide 203 4.7. Cobalt Molybdate Catalysts 204 4.7.1. Presulphiding Cobalt Molybdate Catalyst 205 4.7.2. Other Reactions Over Cobalt Molybdate Catalyst 206 4.8. Nickel Molybdate Catalysts 207 4.9. Physical Form of Cobalt and Nickel Molybdate Catalysts 207 4.10. Replacement and Discharging of Cobalt and Nickel Molybdate Catalysts 208
4.11. Zinc Oxide 209 4.11.1. Background to Zinc Oxide Absorbents 209 4.11.2. Thermodynamics and Reaction Kinetics 209 4.11.3. Formulation of Commercial Zinc Oxide 211 4.11.4. Use of Test Reactors to Assess Zinc Oxide Absorbents 211 4.11.5. Effect of Temperature, Pressure and Space Velocity on Efficiency of Zinc Oxide Absorbents 213 4.11.6. Effect of Gas Composition 216 4.11.7. Effect ofreactor Design 217 4.11.8. Other Desulphurization Uses for Zinc Oxide 219 4.11.9. Impurities in Zinc Oxide 220 4.12. Dechlorination 220 4.12.1. Chloride Sources and Absorbents 220 4.12.2. Operating Conditions 222 4.13. Removal of Silica and Fluoride 223 4.14. Demetallization 223 4.15. Denitrification 224 Chapter 5. Steam Reforming D.E. Ridler, M.V. Twigg 5.1. History 225 5.2. Feedstock and Feedstock Pretreatment 226 5.2.1. Natural Gas 227 5.2.2. Naphthas 228 5.3. Chemistry of Steam Reforming 230 5.3.1. Thermodynamics 230 5.3.2. Kinetics 239 5.4. Design of Steam Reforming Catalysts 244 5.4.1. Selectivity 244 5.4.2. Thermal Stability 244 5.4.3. Physical Properties 244 5.4.4. Nickel as a Steam Reforming Catalyst 244 5.4.5. Supports for Nickel Steam Reforming Catalysts 249 5.4.6. Carbon Formation on Reforming Catalysts 250 5.5. Secondary Reforming 253 5.6. Catalyst Dimensions 254 5.7. Uses of Catalytic Steam Reforming 256
5.7.1. Ammonia Synthesis 256 5.7.2. Methanol Synthesis 258 5.7.3. Oxo Synthesis Gas 259 5.7.4. Reducing Gas 260 5.7.5. Town Gas 261 5.7.6. Substitute Natural Gas (SNG) 263 5.8. Practical Aspects of Steam Reformers 264 5.8.1. Containing the Catalyst 267 5.8.2. Reactant Gas Distribution 269 5.8.3. Firing the Reformer 270 5.8.4. Expansion and Contraction of Reformer Tubes 271 5.8.5. Facilities to Charge and Discharge Catalyst 273 5.8.6. Designing a Reformer for Efficient Operation 274 5.8.7. Catalyst Reduction 274 5.8.7.1. Reduction with Hydrogen 275 5.8.7.2. Reduction with Ammonia 275 5.8.7.3. Reduction with Methanol 276 5.8.7.4. Reduction with Natural Gas 276 5.8.7.5. Reduction with Other Hydrocarbons 276 5.8.7.6. Reduction After Shutdown 277 5.9. Factors Affecting the Life of Reforming Catalyst 277 5.10. Catalyst Poisons 278 5.10.1. Sulphur 278 5.10.2. Arsenic 278 5.11. Hot Bands in Natural Gas Reformers 280 Chapter 6. The Water-gas Shift Reaction L. Lloyd, D.E. Ridler, M.V. Twigg 6.1. Introduction 283 6.2. Thermodynamics 285 6.3. Kinetics and Mechanism 288 6.3.1. Kinetics Over HT Shift Catalyst 288 6.3.2. Kinetics Over LT Shift Catalyst 289 6.3.3. Mechanism of the Catalytic Water-gas Shift Reaction 290 6.4. Converter Design 291 6.5. High-temperature Shift 293 6.5.1. High-temperature Shift Catalyst Formulation 293 6.5.2. Diffusion Effects and Pellet Si'ze 295
6.5.2.1. Effect of Pellet Size on Activity 295 6.5.2.2. Effect of Pellet Sizeon Pressure Drop 296 6.5.3. Reduction of HT Shift Catalyst 298 6.5.4. Operation of HT Shift Catalyst 302 6.5.5. Poisoningand Deactivation 304 6.5.6. Reoxidation and Discharge 306 6.6. Low-temperature Shift 308 6.6.1. General 308 6.6.2. Low Temperature Shift Catalyst formulation 309 6.6.3. Diffusion Effects and Pellet Size 312 6.6.4. Reduction of LT Shift Catalyst 314 6.6.4.1. General Considerations 314 6.6.4.2. Once-through Reductions 317 6.6.4.3. Recycle Reduction Systems 318 6.6.4.4. Commissioning Reduced Catalyst 319 6.6.5. Operation and Monitoring Performance 320 6.6.6. Deactivation and Poisoning 324 6.6.6.1. Deactivation 324 6.6.6.2. Sulphur Poisoning 326 6.6.6.3. Chloride and Other Poisons 328 6.6.7. Oxidation and Discharge 330 6.6.8. GuardBeds 331 6.6.9. Economics of Operation 335 6.7. Recent Developments 335 6.7.1. Sulphur-tolerant Shift Catalysts 335 6.7.2. Operation at Very Low Steam Ratios 338 Chapter 7. Methanation B.B. Pearce, M.V. Twigg, C. Woodward 7.1.Introduction 340 7.2. Methanation in Ammonia and Hydrogen Plants 341 7.2.1. Methanation Equlibria 344 7.2.2. Kinetics and Mechanisms 347 7.2.3. Catalyst Formulation 352 7.2.4. Physical Properties of Methanation Catalysts 358 7.2.5. Catalyst Reduction 359 7.2.6. Catalyst Poisons 360 7.2.7. Predictionof Catalyst Life 362 7.2.8. Operating Experience 365 7.3. Metiianation in Hydrogen Streams for Olefin Plants 367
7.4. Substitute Natural Gas (SNG) 368 7.4.1. Oil-based Routes to SNG 368 7.4.2. Coal-based Routes to SNG 372 7.4.2.1. Lurgi Coal/SNG Process 373 7.4.2.2. HICOM Coal/SNG Process 374 7.4.2.3. Other Developments 376 7.5. Heat Transfer Applications 378 7.5.1. The EVA-ADAM Project 378 Chapter 8. Ammonia Synthesis J.R. Jennings, S.A. Ward 8.1. Introduction 384 8.2. Thermodynamics of Ammonia Synthesis 388 8.2.1. Theoretical Aspects 388 8.2.2. Process Consequences 390 8.2.3. The Synthesis Loop 391 8.3. Ammonia Synthesis Catalysts 393 8.3.1. The Iron Component 394 8.3.2. Promoters 395 8.3.2.1. Structural Promoters 395 8.3.2.2. Electronic Promoters 398 8.4. Catalyst Reduction 400 8.4.1. Typical Plant Procedure 400 8.4.2. Prereduced Catalysts 402 8.4.3. Economics of Prereduced Catalyst 404 8.5. Poisoning and Deactivation 404 8.5.1. Introduction 404 8.5.2. Temporary Poisoning in Ammonia Converters 406 8.5.3. Permanent Poisoning in Ammonia Converters 407 8.6. Kinetics and Mechanism 409 8.6.1. Temkin Kinetics 409 8.6.2. Effect of Catalyst Size 411 8.6.3. Implications on Process Design 412 8.6.4. Reaction Mechanism 413 8.7. Plant Operation 415 8.7.1. General Considerations 415 8.7.2. Circulation 418 8.7.3. Hydrogen/Nitrogen Ratio 420 8.7.4. Influence of Inert Gas Concentration and Purge Rate 420
8.8. Commercial Ammonia Converters 423 8.8.1. General Considerations 8.8.1.1. Flow Type 423 424 8.8.1.2. Temperature Control and Heat Recovery 425 8.8.2. Quench Converter 8.8.3. Indirectly Cooled Multi-bed Converter 426 433 8.8.4. Tube-cooled Converter 433 8.9. The Future 439 Chapter 9. Methanol Synthesis G.W. Bridger, M.S. Spencer 9.1.Introduction 441 9.2. Thermodynamic Aspects 9.2.1. Methanol Formation 442 442 9.2.2. Selectivity 444 9.3. The Methanol Synthesis Process 9.3.1. The Synthesis Loop 446 446 9.3.2. Make-up Gas Composition 452 9.4. Methanol Synthesis Catalysts 9.4.1. High-pressure Catalysts 453 453 9.4.2. Low-pressure Catalysts 455 9.5. Selectivity and Poisons 460 9.6. Mechanisms and Kinetics 462 9.6.1. Reaction Mechanism 462 9.6.2. Kinetics 467 9.7. Recent Developments 467 Chapter 10. Catalytic Oxidations P. Davies, R.T. Donald, N.H. Harbord 10.1. Introduction 469
10.2. Ammonia Oxidation 470 10.2.1. History of Nitric Acid Production 470 10.2.1.1. Routes from Atmospheric Nitrogen 470 10.2.1.2. Ammonia Oxidation 471 10.2.2. Chemistry of the Modern Process 477 10.2.3. The Chemistry of Absorption 477 10.2.4. Nitric Oxide Oxidation Chemistry 478 10.2.5. Ammonia Oxidation Chemistry 479 10.2.6. Modern Plants 482 10.2.7. The Burner Gauze Platinum/Rhodium Catalyst 484 10.2.7.1. Gauze Activation 484 10.2.7.2. Gauze Deactivation and Cleaning 488 10.2.7.3. Metal Recovery 489 10.3. Methanol Oxidation 490 10.3.1. Introduction 490 10.3.2. The Silver-catalysed Process 490 10.3.2.1. Silver-catalysed Reactions 493 10.3.2.2. Selectivity 494 10.3.2.3. Poisoning 494 10.3.2.4. Composition of Reaction Gases 497 10.3.3. The Metal Oxide-catalysed Process 499 10.3.3.1. Metal Oxide-catalysed Reactions 501 10.3.3.2. Composition of Reaction Gases 502 10.3.4. Future Process Developments 502 10.4. Sulphur Dioxide Oxidation 503 10.4.1. Introduction 503 10.4.2. Thermodynamics 503 10.4.2.1. Equilibrium Calculations 503 10.4.2.2. Application to the Contact Process 506 10.4.3. The Contact Process 507 10.4.3.1. Vanadium Catalysts 508 10.4.3.2. The Modern Sulphuric Acid Plant 510 10.4.4. Mechanisms and Kinetics 511 10.4.5. Catalyst Poisoning 514 10.4.6. Disposal of Used Vanadium Catalysts 517 10.4.7. Possible Further Developments 517 Appendices 1. Further Reading 519 2. Numerical Examplesof the Use of Equations Derived in Chapter 2... 525 3. ICI Catalysts for the Production of Hydrogen, Ammonia and Methanol 528 4. Pigtail Nipping 530 5. ICI Technical Publications 532 6. Equilibrium Constants: for the Methane-Steam Reaction at Various Temperatures 537 7. Equilibrium Constants: for the CO Conversion Reaction (Shift) at Various Temperatures 543
8. Nomograph of Selected Properties of Ammonia 549 9. Thermodynamic Properties of Elements and Compounds at 298.15K 550 10. Physical Properties of Methanol 553 11. Approximate Boiling Ranges of Hydrocarbon Feedstocks 554 12. Monitoring Steam Reformer Tube Wall Temperature 555 13. Heat Released During Catalyst Reduction 557 14. Heat Released During Catalyst Oxidation 558 15. Temperature Conversions 559 16. Specific Heats of Catalysts 561 17. Atomic Weights of the Common Elements 562 18. Measurement of Pressure Drop Across Steam Reformer Tubes 565 19. Charging Primary Steam Reformer Catalyst a Case Study 568 20. Equilibrium Constants for the Reaction for Zinc Oxide with Hydrogen Sulphide 572 21. Temperature Measurements in Catalyst Bed 574 References 576 Index 591 *