The article contains sections titled: 1. Introduction 2. Fundamentals 2.1. Chemical Rates 2.2. Relative Degree of Conversion 2.3. Selectivity and Yield 3. Microkinetics 3.1. Elementary Reactions 3.1.1. Fundamentals 3.1.2. Influence of Temperature 3.1.3. Influence of Concentration 3.2. Chemical Equilibria 3.3. Complex Reaction Schemes 3.3.1. Fundamentals 3.3.2. Polymerization Reactions 3.3.2.1. Conversion ‐ Time Curve 3.3.2.2. Radical Intermediates Concentration 3.3.3. Heterogeneous Catalytic Reactions 3.3.3.1. Monomolecular Reactions 3.3.3.2. Bimolecular Reactions 3.3.4. Biochemical Reactions 4. Macrokinetics: Single‐Phase Systems 4.1. Introduction 4.2. Macromixing 4.2.1. Residence‐Time Distribution (RTD) 4.2.2. Batch Reactor (BR) 4.2.3. Plug‐Flow Reactor (PFR) 4.2.4. Continuous, Ideally Stirred Tank Reactor (CISTR) 4.3. Micromixing 4.4. Sequence of Mixing 5. Macrokinetics: Multiphase Systems‐Part I: Mass Transfer without Reaction 5.1. Introduction 5.2. Penetration Models 5.3. Stagnant Film Model 5.4. Mass‐Transfer Coefficients 6. Macrokinetics: Multi‐phase Systems‐Part II: Mass Transfer with Reaction 6.1. Mass Transfer with Reaction in Series 6.1.1. Introduction 6.1.2. Monomolecular First‐Order Kinetics 6.1.3. Arbitrary Monomolecular Kinetics 6.1.4. Multiple Phases 6.1.5. Bimolecular Reactions 6.1.6. Case Study: Shrinking Core Model 6.1.7. Selectivities of Multiple Reactions 6.1.7.1. Introduction 6.1.7.2. Parallel Reactions 6.1.7.3. Consecutive Reactions 6.1.7.4. Complex Reaction Schemes 6.2. Mass Transfer with Simultaneous Reaction 6.2.1. Introduction 6.2.2. Reaction of Gases in Porous Solids 6.2.2.1. Introduction 6.2.2.2. Monomolecular First‐Order Kinetics 6.2.2.3. Monomolecular Arbitrary Kinetics 6.2.2.4. Bimolecular Reactions 6.2.2.5. Anisotropic Catalyst Pellets 6.2.3. Reactions of Gases in Liquids‐Part I: Gaseous Reactants Only 6.2.3.1. Introduction 6.2.3.2. Higbie Penetration Model 6.2.3.3. Surface Renewal Model 6.2.3.4. Stagnant Film Model 6.2.3.5. Comparison of Models for First‐Order Kinetics 6.2.3.6. Comparison of Hatta Numbers with Thiele Moduli 6.2.3.7. Hatta Numbers for Arbitrary Kinetics 6.2.3.8. Case Study: Ideally Mixed Gas ‐ Liquid Reactors 6.2.3.9. Selectivities of Multiple Reactions 6.2.4. Reactions of Gases in Liquids‐Part II:Reactants from both the Gas and the Liquid 6.2.4.1. Introduction 6.2.4.2. Slow Reaction 6.2.4.3. Fast Reaction 6.2.4.4. Instantaneous Reaction 6.2.4.5. Van Krevelen ‐ Hoftijzer Approximation 6.2.4.6. Arbitrary Kinetics 6.2.4.7. Selectivities of Multiple Reactions 6.3. Combination of Simultaneous and Series Mass Transfer and Reaction 7. Macrokinetics: Multiphase Systems‐Part III: Mass and Heat Transfer with Reaction 7.1. Introduction 7.2. Mass and Heat Transfer with Reaction in Series 7.2.1. Particle Mass and Heat Balances 7.2.2. Particle Multiplicity 7.3. Mass and Heat Transfer with Simultaneous Reaction 7.3.1. Frank ‐ Kamenetzki Approximation 7.3.2. Thiele Moduli and Hatta Numbers

Reasons are given why the axial dispersion in a gas flowing through a packed bed may be influenced by the elasticity -or compressibility -of the fluid. To support this hypothesis, experiments have been done in a packed column at pressures from 0.13 to 2.0 MPa. The elasticity E of a gas is proportional to the pressure P and the compressibility to 1 / P . The axial dispersion coefficients as determined were found to be a function of the pressure in the packed bed in the turbulent flow region of 3 < Re, < 150 if the Bodenstein number is plotted as a function of the particle Reynolds number. This is shown to be an artifact. The pressure influence is eliminated, if is plotted versus the ratio of the kinetic forces over the elastic forces eu2/E. Regrettably, Bo,,, seems to be independent of eu2/E. For the moment we only can conclude that in the turbulent region is a unique function of the velocity of the gas which flows through the packed bed. Although the fact that a constant Bo value is obtained when plotted against eu2/E, the experimental results are so intriguing we wanted to make them public already now. The experimental work proceeds.

Packed beds are essentially heterogeneous on a pellet scale. For random packed beds this heterogeneity causes a statistical character both on a pellet and bed scale. We discuss experimental results which deal with bed-scale statistics. For packed beds on a laboratory scale, the results indicate that the beclscale statistical behaviour introduces a spread up to a factor of three in correlations for the effective radial heat conductivity, ,&, and the heat transfer coefficient at the wall, a,. This spread of a factor of three roughly equals the spread between correlations available in the literature. For cooled tubular reactors the statistical spread in the behaviour of the individual tubes will have a large influence on reactor operation.

In earlier studies the behavior of single catalyst pellets of Pd on alumina has been investigated for the reaction of acetylene in an ethylene stream with hydrogen. Particle runaway, temperature over‐ and undershoots and chemically induced temperature oscillations have been observed. After that, the steady state and dynamic behavior of an adiabatic packed bed reactor has been studied experimentally. Temperature profiles of both the gas and solid phase as well as local temperature differences between the two phases were measured. Also here the temperature in the reaction zone exhibited oscillatory behavior. On addition of CO, the oscillations disappeared and the selectivity improved. For a given set of operating conditions, there existed a relatively small range of CO contents with good selectivity and satisfactory conversion. This range depends strongly on the inlet temperature. The dynamic response of the reactor to changes in the CO content showed a considerable wrong‐way behavior. This high sensitivity to fluctuations in the CO content, found for our experimental reactor, indicates a probable cause for a thermal runaway in industrial practice. Recommendations for a stable reactor operation are given.

Al~tract--Many studies have been conducted on the effective heat conductivity (2eft) and the heat transfer coef~cient at the wall (~w) inside packed beds. It has been mentioned that the values of )~ff and ~w are changed when a chemical reaction occurs in the packed bed. We give an explanation for such a phenomenon. The properties 2of f and ew are lumped parameters which usually are determined by both the measured temperature profiles and the model used to calculate the temperature profiles from 2off and ew. If either the experimental data are wrong or the model is erroneous the error will manifest itself in the values of ~.~ff arid ew-At least a part of the change in the values of 2~rf and ew due to a chemical reaction is caused by the fact that a homogeneous model with catalyst and gas having the same temperature is chosen, whereas a heterogeneous model with cata!yst and gas having different temperatures should be used. If no reaction occurs the catalyst and gas will have the same temperature and the homogeneous model yields a good description. Hence, when fitting temperature profiles with this model the correct values of 2 m and ew are found. If reaction does occur the catalyst and the gas will have different temperatures because the heat of reaction must be transferred from the catalyst to the gas. If, despite this fact, a homogeneous model is used to calculate the temperature profiles, an error is introduced which is reflected in the values of 2~ and ~. As a consequence we create an apparent dependence of ).,ff and ew on the reaction rate. We derive criteria to determine which model must be used. We discuss results presented in the literature on the dependence of 2¢f e and e~ on the chemical reaction. The explanation is both qualitative and quantitative. INTRODUCTIONSeveral studies have been conducted on the effective heat conductivity (2~ff) and the heat transfer coefficient at the wall (~w) inside packed beds [-see, for example, Damk6hler (1937), Zehner (1973, Hennecke and Schliinder (1973), Lerou and Froment (1977), Schlfinder (1966, 1978, Bauer (1977), Dixon and Cresswell (1979) and Hofmann (1979a, b)]. To this purpose models were developed for heat transfer inside packed beds. With these models the temperature profiles inside packed beds were fitted by varying 2elf and ~w. Thus the values of ~eff and ~w obtained in the literature are best-fit values. Several authors reported that 2eff and ~ are dependent on a chemical reaction occurring inside the packed bed [-see for example, Hofmann (1979b) and Chao et al. (1973)]. It is hardly likely that this dependence can be explained by experimental errors. It could also be possible that )let f and. c~w are affected by chemical reaction in some physico-chemical way. However, to our knowledge there is no indication whatsoever that can support this vision. The most probable explanation is that the model we use to fit 2ef¢ and ce w yields wrong results when chemical reaction occurs. Since 2ef f and ~ are fit parameters, an error in the model used will manifest ...