Chemical reaction engineering Subject

Thus Chapter 2 discusses the phenomenology and basic concepts of classical promotion, a subject quite familiar to catalysis and surface science researchers and graduate students, at a level which should be comfortable to electrochemists, solid state ionics and chemical reaction engineering researchers. 

A book like the present one, which is not intended as a textbook for students, cannot be written by a single author. In fact, it is a multidisciplinary subject and the authors have not tried to omit all jargon and the flavour of the various disciplines involved. The consequence, of course, is that parts are not easy to understand for chemists, while others are difficult for chemical reaction engineers. It is hoped that this book will strongly contribute to bridging the gap between chemists and chemical engineers in the field. The authors will be grateful for comments from the readers. 

In summary, computational quantum mechanics has reached such a state that its use in chemical kinetics is possible. However, since these methods still are at various stages of development, their routine and direct use without carefully evaluating the reasonableness of predictions must be avoided. Since ab initio methods presently are far too expensive from the computational point of view, and still require the application of empirical corrections, semiempirical quantum chemical methods represent the most accessible option in chemical reaction engineering today. One productive approach is to use semiempirical methods to build systematically the necessary thermochemical and kinetic-parameter data bases for mechanism development. Following this, the mechanism would be subjected to sensitivity and reaction path analyses for the determination of the rank-order of importance of reactions. Important reactions and species can then be studied with greatest scrutiny using rigorous ab initio calculations, as well as by experiments. 

Third, we will add brief historical perspectives to the subject so that students can see the context fi-om which ideas arose in the development of modem technology. Further, since the job markets in chemical engineering are changing rapidly, the student may perhaps also be able to see from its history where chemical reaction engineering might be heading and the causes and steps by which it has evolved and will continue to evolve. 

This is the fun (and frustration) of chemical reaction engineering. While thermodynamics, mass and heat transfer, and separations can be said to be finished subjects for many engineering apphcations, we have to reexamine every new reaction system from first principles. You can find data and construct process flowsheets for separation units using sophisticated computer programs such as ASPEN, but for the chemical reactors in a process these programs are not much help unless you give the program the kinetics or assume equihhrium yields. 

It is our belief that a course in chemical reaction engineering should introduce all undergraduate students to aU these topics. This is an ambitious task for a one-semester course, and it is therefore essential to focus carefully on the essential aspects. Certainly, each of these subjects needs a full course to lay out the fundamentals and to describe the reaction systems peculiar to them. At the same time, we beheve that a course that considers chemical reactors in a unified fashion is essential to show the common features of the diverse chemical reactors that our students will be called on to consider. 

We regard the essential aspects of chemical reaction engineering to include multiple reactions, energy management, and catalytic processes so we regard the first seven chapters as the core material in a course. Then the final five chapters consider topics such as environmental, polymer, sohds, biological, and combustion reactions and reactors, subjects that may be considered optional in an introductory course. We recommend that an instmctor attempt to complete the first seven chapters within perhaps 3/4 of a term to allow time to select from these topics and chapters. The final chapter on multiphase reactors is of course very important, but our intent is only to introduce some of the ideas that are important in its design. 

Most texts strive to be encyclopedias of a subject from which the instmctor takes a small fi action in a course and that are to serve as a future reference when a student later needs to learn in detail about a specific topic. This is emphatically not the intent of this text. First, it seems impossible to encompass aU of chemical reaction engineering with less than a Kirk-Othmer encyclopedia. Second, the student needs to see the logical flow of the subject in an introductory course and not become bogged down in details. Therefore, we attempt to write a text that is short enough that a student can read aU of it and an instmctor can cover most of it in one course. This demands that the text and the problems focus carefully. The obvious pitfall is that short can become superficial, and the readers and users will decide that difference. 

A further characteristic of chemical reaction engineering is its facility in refining concepts. It is a derived characteristic, stemming from the mathematical component of the subject, but it has been typical of its development since the distinction between stability and sensitivity was first drawn (34). There have been lapses, alas, as in the case of an expository paper (52) which, to judge by the demand for offprints, proved quite useful, but which rated a very low Watkins number (53), for its title was "On the stability criteria of chemical reaction engineering" while its burden was as much the multiplicity criteria as the stability conditions. But there has been a steady incorporation of precisely defined concepts as for example in the burgeoning study of... 

The reason for me reminding you of these foundations is to draw attention to the scarcity of further models beyond these two basic types. The bubbling gas fluidised bed is one of the very few additional models albeit a much more complicated one and necessarily more limited in application. This is why it is such a fascinating subject to chemical reaction engineers. 

This chapter gives an introduction to the subject of chemical reaction engineering. The first part introduces basic definitions and concepts of chemical reaction engineering and chemical kinetics and the importance of mass and heat transfer to the overall chemical reaction rate. In the second part, the basic concepts of chemical reactor design are covered, including steady-state models and their use in the development... 

After many years, chemical reaction engineering has developed a paradigm classic papers that are universally admired, basic assumptions and analysis, successful applications of principles to particular problems, and standard textbooks and curricula that are generally accepted. Chemical reaction engineering is not yet completely matured and thus has not been reduced to restatements of old results and remeasurements with greater accuracy. The innovation processes continue to develop. New needs of society, such as synthetic fuels, and new technical opportunities, such as recombinant DNA, will keep this subject vigorous for many years to come. 

The analysis and design of multiphase reactors is probably the most widely researched subject in the area of chemical reaction engineering at the present time. While the subject of two-phase reactor design (i.e., gas-solid and gas-liquid) has been extensively reviewed in numerous texts, no similar treatment of three-phase (i.e., gas-liquid-solid) reactor design is available. 

The problem of bubble motion in a liquid is fundamental in chemical reaction engineering because about 25% of all chemical reactions occur in bi-phase systems. As we have shown, the gas-liquid two-phase flow prevailing in a bubble column is extremely complex. It is dominated by a rich variety of logical configurations and exhibits inherent unsteadiness. As a consequence, the modelling of this flow is an attractive subject and constitutes an excellent subject for stochastic modelling. 

The Proceedings of the Second European Symposium on Chemical Reaction Engineering were published as Volume 14 of the Journal Chemical Engineering Science while the present work was in press. It should be said that this symposium contains more that is germane to our subject than it has been possible to indicate here. 

With the assurance that analysis and synthesis, like theory and experiment, are complementary rather than competitive, let us take a general look at the territory we wish to explore. The subject is also referred to as chemical reaction engineering or applied chemical kinetics, and the latter suggests that we should first make the distinction between... 

The material offered in this chapter is only a condensed treatment of basic elements of chemical reactor engineering needed to approach a process design problem. The reader should have already a good knowledge of this discipline. As study or refreshment material, we recommend in the first place the classical textbooks due to Levenspiel (recent edition in 1999) and Fogler (1992). Other remarkable books have been published by Carberry (1976), Westerterp, van Swaaij and Beenackers (1984), as well as by Froment and Bishop (new edition in 1990). More advanced treatment of different subjects in chemical reaction engineering can be found in the monograph edited by Carberry and Varma (1987) with contributions of experts in each field. 

One of the most important areas for application of concepts discussed in the previous section is the selection of polymerization reactors. The properties of polymers depend on their molecular weight distribution (M WD) and so the design should ultimately use this as its basis. The subject is a vast one, and so only the basic concepts will be briefly discussed. Several excellent reviews now exist, covering various aspects of the area from a chemical reaction engineering viewpoint see Shinnar and Katz, Keane, and Gerrens, [18, 19, 20]. The latter presents a masterful survey of the effects of the choice of reactor type. 

Of course, many fine books have been written on the subject of catalysis. To study how to design reactors to achieve the desired selectivity, several outstanding textbooks are available consider, for example. Elements of Chemical Reaction Engineering (Fogler, 1986) and The Engineering of Chemical Reactions (Schmidt, 1998). 

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