CATALYTIC SCIENCE SERIES VOL. 10 Series Editor: Graham J. Hutchings Concepts in Syngas Manufacture Jens Rostrup-Nielsen Lars J. Christiansen Haldor Topsoe A/S, Denmark Imperial College Press
Contents Preface Part I Basic Principles 1 Routes to Syngas 3 1.1 General trends 3 1.1.1 Towards focus and sustainability 3 1.1.2 Direct or indirect conversion 10 1.2 Manufacture by steam reforming of hydrocarbons 14 1.2.1 Reactions and thermodynamics 14 1.2.2 Product gas composition 26 1.2.3 Thermodynamics of higher hydrocarbons 30 1.2.4 The tubular reformer 31 1.2.5 Carbon formation. Higher hydrocarbons 34 1.2.6 Non-tubular reforming 36 1.3 Other manufacture routes 38 1.3.1 Partial oxidation 38 1.3.2 Autothermal reforming 41 1.3.3 Catalytic partial oxidation 43 1.3.4 Air-blown technologies and membranes 48 1.3.5 Choice of technology 49 1.4 Other feedstocks 51 1.4.1 Alcohols, oxygenates 51 1.4.2 Coal, gasification 55 1.4.3 Biomass 63 1.5 Gas treatment 64 1.5.1 Purification 64 1.5.2 Water gas shift 67 1.5.3 Acid gas removal 70 2 Syngas Applications 73 2.1 Thermodynamic framework for syngas processes 73 2.1.1 Syngas properties 74 2.1.2 Synthesis process properties 79 2.1.3 Process analysis 80 2.2 Hydrogen 85 2.2.1 Routes to hydrogen 85 2.2.2 Hydrogen by steam reforming of hydrocarbons 87 vii
viii Concepts in Syngas Manufacture 2.2.3 The steam export problem 92 2.2.4 Membrane reforming 94 2.2.5 Hydrogen via catalytic partial oxidation (CPO) 95 2.3 Fuel cells 96 2.3.1 Fuel processing system 96 2.3.2 Internal reforming 99 2.3.3 Process schemes for SOFC 104 2.4 CO rich gases 105 2.4.1 Town gas 105 2.4.2 Oxogas 106 2.4.3 Reducing gas 110 2.5 Ammonia 112 2.6 Methanol and synfuels 117 2.6.1 Methanol as intermediate 117 2.6.2 Methanol plant 118 2.6.3 Methanol via gasification 123 2.6.4 Combined syntheses and co-production 124 2.6.5 Fischer Tropsch synthesis 127 2.6.6 SNG 134 2.7 Chemical recuperation 138 Part II Steam Reforming Technology 3 Technology of Steam Reforming 143 3.1 Early developments 143 3.2 Steam reforming reactors 146 3.2.1 Role of catalyst 146 3.2.2 The tubular reformer 149 3.2.3 Scale-up of steam reforming technology 153 3.2.4 Plant measurements 154 3.2.5 Reformer temperature measurements 157 3.3 Modelling of steam reforming reactors 159 3.3.1 Two-dimensional reactor model 162 3.3.2 Heat transfer in the two-dimensional model 168 3.3.3 Heat transfer parameters in syngas units 171 3.3.4 Pressure drop 176 3.3.5 Convective reformers 178 3.3.6 Tubular reformer furnace chamber 181 3.3.7 Tubular reforming limits of Operation 187 3.3.8 Micro-scale steam reforming reactors 189 3.4 Modelling of the catalyst particle 191 3.4.1 Catalyst particle model 192 3.4.2 Effective diffusion coefficients 195
Contents ix 3.4.3 Simulation of a hydrogen plant reformer 197 3.5 Reaction kinetics 199 3.5.1 Industrial rates and the scale-down problem 199 3.5.2 Intrinsic kinetics. Steam reforming of methane 204 3.5.3 Steam reforming of higher hydrocarbons 210 3.5.4 CO2 reforming 212 4 Catalyst Properties and Activity 213 4.1 Catalyst structure and stability 213 4.1.1 Reactions with the support 213 4.1.2 Activation and nickel surface area 216 4.2 Nickel surface area 219 4.2.1 Measurement of nickel surface area 219 4.2.2 Nickel surface area and catalyst preparation 224 4.2.3 Sintering 224 4.3 Catalyst activity 227 4.3.1 Group VIII metals 227 4.3.2 Non-metal catalysts 228 4.3.3 Thermal reactions catalytic steam cracking 230 5 Carbon and Sulphur 233 5.1 Secondary phenomena 233 5.2 Carbon formation 233 5.2.1 Routes to carbon 233 5.2.2 Carbon from reversible reactions 241 5.2.3 Principle of equilibrated gas 247 5.2.4 Principle of actual gas and steady-state equilibrium 252 5.3 Steam reforming of higher hydrocarbons 257 5.3.1 Whisker carbon in tubular reformer 257 5.3.2 Catalyst promotion 260 5.3.3 "Gum formation" in prereformers 264 5.3.4 Carbon from pyrolysis 270 5.3.5 Regeneration of coked catalyst 273 5.4 Sulphur poisoning of reforming reactions 275 5.4.1 Chemisorption of hydrogen sulphide 275 5.4.2 Chemisorption equilibrium 277 5.4.3 Dynamics of sulphur poisoning 281 5.4.4 Regeneration for sulphur 282 5.4.5 Impact of sulphur an reforming reactions 285 5.5 Sulphur passivated reforming 288 5.6 Other poisons 293 6 Catalysis of Steam Reforming 295 6.1 Historical perspective 295 6.2 The role of step sites 298
x Concepts in Syngas Manufacture 6.3 Geometric or electronic effects 305 6.4 Metal activity. Micro-kinetics 307 6.5 The parallel approach 311 Appendix 1 Enthalpy of formation 313 Appendix 2 Chemical equilibrium constants 317 Notation and Abbreviation 323 References 331 Author index 357 Subject index 369