REACTION ENGINEERING CONSIDERATIONS

The kinetic and catalytic parameters of the reaction involved as well as the design and operating variables of the membrane reactor all play important roles in the reactor performance. They will be treated in some detail in this chapter. 

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In the field of chemical reaction engineering considerable efforts are devoted to tackling the problem of limited selectivities with which intermediates can be produced in coupled parallel-series reactions. Typical and important examples are partial oxidations where the formation of undesired side products or total oxidation products significantly reduces process efficiencies. Despite the progress achieved in the field of catalysis, many important industrial reactions still suffer from not satisfying conversion-selectivity relationships [52],... 

Since chemical reaction engineering considerations apply to nondcterministic as well as deterministic methods they will be briefly dealt with separately. The interaction of chemical kinetics and transport processes and their effect on catalyst activity and selectivity in reaction networks will be emphasized. Some attention will be also paid to catalyst deactivation. 

Oxidation processes may rely on pH adjustment to enhance the chemical reaction. Figure 16 illustrates the typical configuration of a chemical oxidation process. The m or engineering considerations for chemical oxidation include reaction kinetics, mass transfer, by-products, temperature, oxidant concentration, pH and vent gas scrubbing. 

These operations are characterized by different reaction engineering properties. The transport of momentum, heat, and mass take place by different rates in the different operations, and the yield and selectivity obtained for a given chemical reaction will depend upon the type of operation employed. The operations also differ with respect to more loosely defined characteristics, such as ease of operation, and it can be noted in particular that some operations have been studied with considerably more thoroughness than others, and may consequently be designed with greater accuracy and reliability. 

A more general model of gas-liquid-particle processes than those that have so far appeared in the literature would, it seems, be of considerable interest as a basis for comparing the reaction-engineering properties of the several types of gas-liquid-particle operations, and as a means for analyzing operations with finite liquid flow (for example, trickle-flow operation and gas-liquid fluidization). 

Reaction kinetics, catalyst handling, mass and heat transfer, corrosion and many other practical industrial chemistry and engineering considerations impact the success of scaleup from lab to commercial for batch processing. Since the starting point for scaleup studies is the ultimate intended commercial unit, the professional should scaledown from the design parameters and constraints of the proposed commercial unit. 

The field of chemical reaction engineering (CRE) is intimately and uniquely connected with the design and scale-up of chemical reacting systems. To achieve the latter, two essential elements must be combined. First, a detailed knowledge of the possible chemical transformations that can occur in the system is required. This information is represented in the form of chemical kinetic schemes, kinetic rate parameters, and thermodynamic databases. In recent years, considerable progress has been made in this area using computational chemistry and carefully... 

In this introductory chapter, we first consider what chemical kinetics and chemical reaction engineering (CRE) are about, and how they are interrelated. We then introduce some important aspects of kinetics and CRE, including the involvement of chemical stoichiometry, thermodynamics and equilibrium, and various other rate processes. Since the rate of reaction is of primary importance, we must pay attention to how it is defined, measured, and represented, and to the parameters that affect it. We also introduce some of the main considerations in reactor design, and parameters affecting reactor performance. These considerations lead to a plan of treatment for the following chapters. 

In this chapter, we return to the main theme of this book, chemical reaction engineering (CRE). We amplify some of the general considerations introduced in Chapter 1, before the detailed consideration of quantitative design methods in Chapter 12 and subsequent chapters. 

Chapter 11 Preliminary Considerations in Chemical Reaction Engineering... 

Our treatment of Chemical Reaction Engineering begins in Chapters 1 and 2 and continues in Chapters 11-24. After an introduction (Chapter 11) surveying the field, the next five Chapters (12-16) are devoted to performance and design characteristics of four ideal reactor models (batch, CSTR, plug-flow, and laminar-flow), and to the characteristics of various types of ideal flow involved in continuous-flow reactors. Chapter 17 deals with comparisons and combinations of ideal reactors. Chapter 18 deals with ideal reactors for complex (multireaction) systems. Chapters 19 and 20 treat nonideal flow and reactor considerations taking this into account. Chapters 21-24 provide an introduction to reactors for multiphase systems, including fixed-bed catalytic reactors, fluidized-bed reactors, and reactors for gas-solid and gas-liquid reactions. 

CSD modelling based on population balance considerations may be applied to crystalliser configurations other than MSMPR(37) and this has become a distinct, self-contained branch of reaction engineering)56,59,60 73). 

Such global reaction expressions can be found for oxidation of a range of hydrocarbon fuels [107], They may be useful for engineering considerations but should be used very cautiously. Global reaction rates are only valid in a narrow range of conditions and cannot be extrapolated with any confidence. 

Modeling the monolith Some methodological considerations (with S.T. Lee). Paper presented at the Fourth International-Sixth European Symposium on Chemical Reaction Engineering, Heidelberg, 6-8 April 1976. 

It is explosive, and distillation, even under reduced pressure as described, may be dangerous [1]. A Hungarian patent describes a safe procedure for in-situ generation of the ester, azeotropic dehydration and subsequent metal-catalysed reaction with 1,3-dienes to give alkyl cyclopropanecarboxylates [2]. A calorimetric study and consequent engineering considerations for industrial scale use of solutions of this reagent have been described [3]. It is claimed it does not detonate [4]. 

The reaction engineering in the MTG plant centered on how deep the catalyst bed had to be to avoid premature methanol break-through. The decision that the minimum bed depth had to be 2.5 meters eliminated radial reactors from consideration. 

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