CHEMICAL REACTION ENGINEERING APPLICATIONS in NON-TRADITIONAL TECHNOLOGIES a Textbook Supplement

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CHEMICAL REACTION ENGINEERING APPLICATIONS IN NON-TRADITIONAL TECHNOLOGIES A Textbook Supplement

PHILLIP E. SAVAGE, STEVEN BLAINE University of Michigan ond approach is to incorporate examples dealing with Ann Arbor, MI 48109-2136 non-traditional technologies in each of the core un dergraduate courses. This second approach has the ecent years have witnessed an expansion of advantage of more easily integrating the new tech R chemical engineering activity in areas such as nologies with fundamental principles and obviating materials processing (e.g., microelectronics, super the need to find additional room in an already conductors, composites) and biotechnology. This crowded curriculum. expansion has been accompanied by a reduction in A barrier to weaving examples from new tech chemical engineering opportunities in the more tra nologies into existing courses, however, is that most ditional areas of petroleum processing and commod chemical engineering textbooks, though good at pre ity chemicals. senting fundamental principles, generally do not These events have led to much introspection in provide examples and applications from non the chemical engineering community. One effect on traditional technologies. Thus, the instructor is forced education has been a new and widely-recognized to identify and develop such examples on his own. In need to broaden the technological base of under some cases the problem has been recognized and graduate education. Students must be exposed to steps have been taken to provide instructors with chemical engineering applications in the frontier useful materials. A good example is the book Chemi areas in addition to continued exposure to applica cal Engineering Education in a Changing Environ tions in traditional petroleum processing and petro ment1 11 which provides the proceedings of a confer chemical applications. ence sponsored jointly by the Engineering Founda tion, the National Science Foundation, and the Ameri One approach to providing the necessary expo can Institute of Chemical Engineers. It presents a sure is to develop elective courses dealing with spe large number of problems that deal with non cific technologies (e.g., biochemical technology, mi traditional technologies, along with their solutions. croelectronics processing, polymer processing). A sec- The problems are intended for use as examples in

Phillip Savage is an assistant professor of ChE at the lectures or as homework assignments. Another ex University of Michigan. He received his BS from Penn ample is a set of articles on microelectronics process State and his MChE and PhD degrees from the Uni ing that recently appeared in Chemical Engineering versity of Delaware. His research interests are in re 12 61 action pathways, kinetics, and mechanisms. Education. - This paper describes a set of educational materi als that we have developed which deal with chemical engineering applications in "emerging" technologies. These materials take the form of a textbook supple Steven Blaine received a BSChE from the University ment. Our goal was to develop materials for use in a of Florida in 1986 and a MSE in chemical engineering chemical reaction engineering course. Thus, we se from the University of Michigan in 1988. Currently, he is a candidate for the PhD in chemical engineering at lected examples from microelectronics processing and the University of Michigan © Copyright ChE Division, ASEE 1991 150 Chemical Engineering Education A barrier to weaving examples from new technologies into existing courses ... is that most chemical engineering textbooks, though good at presenting fundamental principles, generally do not provide examples and applications from non-traditional technologies. Thus, the instructor is forced to identify and develop such examples on his own.

biochemical technology that illustrate key concepts Nauman gives a brief and largely qualitative discus in kinetics and reaction engineering. Here we will sion of reaction engineering issues in the fabrication describe the organization and content of our text of electronic devices. Fogler provides a few problems book supplement and show how it can be integrated dealing with chemical vapor deposition at the end of into an undergraduate reaction engineering course. his chapter on heterogeneous reactions, along with A copy of the supplement can be obtained by writing three problems (without solutions) concerning mi to the authors. croelectronics fabrication in an appendix. An encouraging trend, evident in the table, is MOTIVATION FOR DEVELOPING THE that the most recent books have the most material COURSEPACK relevant to biotechnology and microelectronics proc essing. This trend will certainly continue as new and We began developing the materials described in revised textbooks are published. Fogler's second edi this paper in the spring of 1988. At that time there were very few such educational materials available tion, for instance, has an expanded treatment of to the chemical engineering community even though these topics. it was quite clear that examples from microelectron Our desire to integrate examples from non ics processing (for instance) could easily be used to traditional technologies into the traditional chemi illustrate key reaction engineering principles. Un cal reaction engineering course and the omission of fortunately, existing textbooks provided very few ap such examples in most texts motivated our work in plications ofreaction engineering principles to prob developing a textbook supplement. This supplement lems encountered in microelectronics processing and took the form of a spiral-bound coursepack that the biotechnology. students could purchase for a nominal fee from a Table 1 lists several reaction engineering texts local copying center. and the number of pages each devotes to these two particular technologies. As can be seen, many of the OVERVIEW AND ORGANIZATION OF THE texts completely omit any reaction engineering ap COURSEPACK plications in these technologies. Hill and Fogler, however, include several pages on enzyme kinetics. The coursepack comprises two main sections. One Nauman likewise covers Michaelis-Menten kinetics, deals with microelectronics processing and the other and he also includes a few pages on fermentation. with biochemical technology. The microelectronics processing section contains three chapters, and the Reaction engineering applications in microelec topics covered are chemical vapor deposition, plasma tronics processing are much more scarce, however. etching, and the thermal oxidation of silicon. The biochemical technology section contains two chap TABLE 1 ters: one concerns fermentation and bioreactor de Textbooks and Non-Traditional Technologies sign and the second discusses catalysis by immobi lized enzymes. Pages Devoted to Author Biotechnology Microelectronics Each of the chapters comprises three sections: Introduction, Applications of Chemical Reaction Carberry (1976)171 0 0 Engineering, and Problems. The first section intro Hill (1977)181 7 0 duces one particular aspect of an emerging technol Holland and Anthony (1979)1•1 0 0 ogy and provides background material necessary for Butt (1980)1101 0 0 the subsequent sections. The second section illus Smith (1981)111 1 0 0 trates, via examples, how established reaction engi Fogler (1986)112 1 8 3 neering principles can be applied to this particular Nauman (1987)1131 11 3 aspect of the technology. Detailed derivations are Froment and Bischoff (1990)1141 0 0 often omitted, and the student is expected to refer to

Summer 1991 151 the textbook for basic explanations of the principles. with heterogeneous reaction kinetics. In this section The final section provides several problems that al we use the standard Langmuir-Hinshelwood-Hougen low the students to use what they have learned in Watson formalism to derive a rate law for deposition the earlier sections. of polycrystalline silicon from silane. This example illustrates the application of elementary reactions We have designed this textbook supplement so (adsorption, desorption, surface reaction) and the that it can be easily integrated into a chemical reac concept of a rate-limiting step. tion engineering class. The coursepack is structured so that the chemical reaction engineering principles The third application in the CVD chapter in that are being employed are clearly evident within volves an analysis of reaction and diffusion in a the applications section of each chapter. Table 2 horizontal, multiple-wafer-in-tube, low-pressure CVD summarizes the general reaction engineering prin reactor. The reactor contains a large number of closely ciples emphasized in each chapter in the coursepack. spaced wafers upon which it is desired to deposit a thin, uniform film. The direction of flow of the gase Organizing the coursepack around reaction ous reactants is normal to the wafer surface so diffu engineering principles facilitates the integration of sion is the dominant mode of transport between the relevant examples from non-traditional technologies wafers. Mathematically, this problem is identical to into the traditional course. For example, the con that ofreaction and diffusion in a porous, cylindrical cepts involved in the design of an isothermal CSTR catalyst particle. Thus, the principles of coupled rate can be illustrated using a rate law for cell growth processes (i.e., diffusion and surface reaction) can be kinetics as well as one for a generic reaction such as applied in this case, and the Thiele modulus and the A • B + C. Additionally, the key ideas behind the concept of an effectiveness factor emerge quite natu derivation of rate laws for heterogeneous catalytic rally. reactions (i.e., Langmuir-Hinshelwood-Hougen-Wat son kinetics) can also be applied to derive rate ex The final application in the CVD chapter pressions for chemical vapor deposition processes. deals with chemical equilibrium for the reaction

• As a final example, transport and reaction in the SiH4 <=> S\ .> + 2H2 Here, we calculate the equilib inter-wafer region of a horizontal plasma etching rium constant for the reaction and then use it to reactor is amendable to the same type of analysis show that the reactor pressure and temperature and employed in modeling diffusion and reaction in a the feed stream composition determine the direction catalyst particle. in which the reaction occurs. That is, some operating conditions can lead to etching (i .e., removal of silicon To illustrate more fully the manner in which the from the surface) whereas other conditions can lead coursepack can be integrated into the reaction engi to deposition of Si. This example illustrates the im neering class, consider the chapter on chemical va portance of thermodynamics in chemical reaction por deposition which features four different applica engineering. tions of chemical kinetics and reaction engineering: collisional activation of gas-phase reactions, hetero One of the pedagogical benefits of using examples geneous reaction kinetics, diffusion and reaction, and from non-traditional technologies alongside their chemical equilibrium. more traditional counterparts is that doing so helps to emphasize the importance of the underlying physi The illustration of the first principle uses the cal and chemical phenomena rather than the spe- • , reaction SiH4 SiH2 + H2 which can ocur in the gas phase during the CVD of polycrystalline silicon from silane. Here we employ the simple Lindemann mecha TABLE2 nism for unimolecular reactions and the pseudo Reaction Engineering Principles in Coursepack steady-state approximation to derive a rate law for the reaction. The rate equation clearly shows that Principles ---- Chapter---- Sil icon the reaction can be second order in silane at low Plasma Oxida- Ferman- Enzy me pressures and first order at high pressures. This CVD Etching tion tation Ca talysis example can be used in the reaction engineering Reactor Modeling v' v' v' v' course to reinforce the concepts of elementary reac Chemical Equilibrium v' tion steps, active centers, and the steady-state ap Reaction Kinetics v' v' v' proximation. Diffusion and Reaction v' v' v' The second application in the CVD chapter deals 152 Chemical Engineering Education cific example that is being used to illustrate the phenomena. For instance, when students begin to REVIEW: Numerical Methods realize that the same set of principles can be used to Continued from page 144 understand the behavior of a fixed-bed catalytic until a steady state is reached. Another interesting reactor and the behavior of a low-pressure, chem feature of the book is its excellent compilation of ical vapor deposition reactor, then they are be problems. ginning to focus on those fundamental principles rather than on the specific technological applica The reviewer has serious doubts whether a stu tions. As a result, the students obtain a deeper ap dent can truly appreciate the chemical engineering preciation for the general applicability of chemical orientation of the book at the sophomore level-one engineering science. can easily get weighted down by new concepts which can divert the attention away from the numerical SUMMARY techniques themselves. It would be better to use this text at the senior level, after a student has been We have developed a textbook supplement that exposed to the basic courses in chemical engineer facilitates the integration of examples from non ing. But at that level, one could possibly introduce traditional technologies into a reaction engineer the orthogonal collocation method, which is quite ing course. These educational materials provide a popular now but which does not find a place in this means for introducing students to the application of text. Also, one could then do more justice to the chemical reaction engineering principles in micro stiffness of ODE's (although some introductory dis electronics and biochemical technology. The cussion exists on stability criteria for IVP's) and to coursepack has been used in classes at The Univer finite element techniques. sity of Michigan, and the student evaluations have been generally favorable. Overall, this book will satisfy the demands of undergraduate chemical engineering students who ACKNOWLEDGEMENT usually have difficulty in understanding the presen tations in more general texts. With some additional The work described in this paper was supported material incorporated by an instructor, it could be by a Faculty Development Grant from the Univer an excellent text at the senior level. Some instruc sity of Michigan Center for Research on Learning tors can possibly use this as a text at earlier stages and Teaching. in the curriculum. 0

REFERENCES 1. Sandler, S.I., and B.A. Finlayson, eds, Chemical Engineer Nfi• books received ) ing Education in a Changing Environment, Engineering Foundation, New York, NY (1988) Computational Quantum Chemistry, by Alan Hinchliffe; John 2. Anderson, T.J., Chem. Eng. Ed., 24, 26 (1990) Wiley & Sons, 1 Wiley Dr., Somerset, NJ 08875-1272; 112 pages, 3. Hess, D.W. , Chem. Eng. Ed., 24, 34 (1990) $34.95 (1988) 4. McConica, C.M., Chem. Eng. Ed., 24, 38 (1990) Diffusion and Convection in Porous Catalysts, Webster and Strie 5. Takoudis, C.G., Chem. Eng. Ed., 24, 42 (1990) der, eds; AIChE, 345 East 47th St., New York, NY 10017; 96 6. Orazem, M.E., Chem. Eng. Ed., 24, 48, (1990) pages; $20 members, $35 Others (1988) 7. Carberry, J .J ., Chemical and Catalytic Reaction Engineer ing, McGraw-Hill Book Company, New York, NY (1976) Separation Technology, Li and Strathmann, eds; AIChE, 345 8. Hill, C.G., An Introduction to Chemical Engineering Ki East47th St., New York, NY 10017; 633 pages; $50 Members, $70 netics and Reactor Design, John Wiley & Sons, Somerset, Others (1988) NJ (1977) 9. Holland, C.D., and R.G. Anthony, Fundamentals ofChemi Environmental Management Handbook: Toxic Chemical Materi cal Reaction Engineering, Prentice-Hall, Englewood Cliffs, als and Wastes, by Kokoszka and Flood; Marcel Dekker, Inc., 270 NJ (1979) Madison Ave., New York NY 10016; 656 pages, $125 (1989) 10. Butt, J.B., Reaction Kinetics and Reactor Design, Pren tice-Hall, Englewood Cliffs, NJ (1980) Fatty Acids in Industry: Processes, Properties, Derivatives, Appli 11. Smith, J .M., Chemical Engineering Kinetics, McGraw-Hill cations, edited by Johnson and Fritz; Marcel Dekker, Inc., 270 Book Company, New York, NY (1981) Madison Ave., New York, NY 10016; 688 pages, $150 (1989) 12. Fogler, H.S., Elements of Chemical Reaction Engineering, Prentice Hall, Englewood Cliffs, NJ (1986) Droll Science, compiledby Robert L. Weber; The Humana Press 13. Nauman, E.B., Chemical Reactor Design, John Wiley and Inc., PO Box 2148, Clifton, NJ 07015; 352 pages, $22.50 (1987) Sons, Somerset, NJ (1987) 14. Froment, G.F., and K.B. Bischoff, Chemical Reactor Analy How to Write and Publish a Scientific Paper, 3rd edition, by sis and Design, John Wiley and Sons, Somerset, NJ (1990) Robert A. Day; Oryx Press 2214 North Central at Encanto, Phoe 0 nix, AZ 85004; 224 pages, $21.95 (1988)

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