Coordination of multi-scales in chemical engineering

Chemical Engineering Science 62 (2007) 3326 – 3334 www.elsevier.com/locate/ces

Coordination of multi-scales in chemical engineering James Wei ∗ Department of Chemical Engineering, Princeton University, A36 Engineering Quadrangle, Princeton, NJ 08544-5263, USA Received 30 May 2006; received in revised form 8 September 2006; accepted 22 September 2006 Available online 24 March 2007

Abstract The work of chemical engineers involves an enormous range of scales: from molecules in nano-meters to the globe in mega-meters, and from molecular rotation in pico-seconds to global warming in giga-seconds. However, most chemical engineers are specialists in only one or two scales, and coordination is needed to ensure harmony and productivity in service to the human condition. There are three historic successful methods of coordination: (a) a single all-knowing generalist, (b) the volunteer cooperation among specialists, and (c) the hierarchical command of specialists. The numerous opportunities and threats today urgently require coordination among scales, and the volunteer cooperation method seems the most appropriate for the future since the complexities of the problems involved transcend the competence of any single organization. 䉷 2007 Elsevier Ltd. All rights reserved. Keywords: Length scale; Time scale; Molecule; Crystallite; Particle; Equipment; Plant; Globe; Single entrepreneur; Volunteer cooperation; Command hierarchy

1. The work of chemical engineering in length and time scales The work of chemical engineers involves the dimensions of length, mass, and time, over a tremendous range of scales. The sciences at each scale are different, and the phenomena obey different laws and thus different equations are at work. The education of chemical engineers exposed them to some extent in all scales, but their professional competences are usually concentrated on only one or two scales. Let us start by looking at the six scales involved in Fig. 1: (a) a decane molecule approaching the LTA zeolite opening has a length of 1.3 nm and a diameter of 0.4 nm, (b) the zeolite crystallites have a diameter of 5 m, (c) the catalyst pellets that contain the zeolite crystallites have a diameter of 3 mm, (d) the catalytic reactor has a height of 20 m, (e) the refinery at Paulsboro, NJ, covers an area with a diameter of 2 km, and (f) the globe of the whole earth has a diameter of 1.2 × 107 m. The chemical engineers are responsible for the design and operation in the scales from the zeolite crystallites to the refinery, but their work is strongly influenced and controlled by events in the molecular and the global scales. ∗ Tel.: +1 609 258 5618; fax: +1 609 258 0211.

E-mail address: [email protected]. 0009-2509/$ - see front matter 䉷 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2006.09.049

(a) Let us start our journey from the smallest molecular scale, and work our way up to the global scale. The decane molecule is some 1.3 nm in length, and has a diameter of about 0.4 nm. The decane molecule is approaching a zeolite crystal of Linde A with numerous circular openings or windows lined with eight oxygen atoms with a diameter of 0.4 nm. The molecule is driven by thermal forces to translate, rotate, and vibrate. It cannot enter the zeolite channel unless it is translated to a position directly at the channel, and rotated so that it is oriented to be parallel to the zeolite channel. The speed of the translation is controlled by the kinetic theory of gases, and is about 200 m/s in room temperature (Bird et al., 1960). In a dense gas or a liquid, the speed would be slowed down by collisions with other molecules, and turn from free flight into diffusion. The speed of this rotation is controlled by the quantum mechanics, which involve solving the Schrodinger equation H  = E. In the vacuum, the rotation time is of the order of 10−11 s (McQuarrie and Simon, 1999). After achieving the appropriate position and orientation, a molecule can enter the channel only if the molecular diameter is smaller than the channel diameter. A molecule can enter a zeolite window only if the molecule has a smaller diameter than the window. To be more precise, whether a molecule can enter a window depends on the “footprint” of the molecule, which is the two-dimensional projection of all the atoms in the most favorable orientation

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Fig. 1. Six scales of chemical engineering. Upper left, the globe has diameter 1.2 × 107 m; upper middle, an oil refinery at Paulsboro, NJ, has diameter 2 × 103 m; upper right, a fluid cracking reactor has a height of 20 m; lower left, catalyst particles with diameter 3 × 10−3 m; lower middle, zeolite crystallites with diameter 2 × 10−6 m; lower right, decane molecule approaching LTA zeolite window with diameter 0.5 × 10−9 m.

encased in their individual van der Waal radii, in comparison with the size of the opening of the zeolite window. Since both the molecule and the zeolite structure are flexible, especially at elevated temperatures, it is often possible to squeeze in a molecule that has a diameter that is 10–20% larger than the diameter of the zeolite window. Such entry involves activation energy of distorting a number of parameters in the molecule from their equilibrium positions, including the van der Waal radii of the outer atoms, the bond lengths and angles, and the bond torsions. The selectivity of a catalyst, such as the ability of

a zeolite to crack normal paraffin but not the branched paraffin, plays a critical role in increasing the octane number of gasoline and in lowering the pour point of lubricating oil (Chen et al., 1989). (b) A zeolite crystallite is created by crystallization from solution, and is often several microns in diameter (International Zeolite Association, 2006). A very large crystal is not suitable for catalysis, when the diffusion time is excessive in comparison with the reaction time. The diffusion time of a molecule into the zeolite channels is measured by d = (R 2 /D), where R is

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the crystal radius and D is the diffusivity. Diffusion in zeolites is often in the configurational regime, when the molecule is constantly in contact with the solid walls, and the diffusivity can range from 10−5 to 10−14 cm2 /s (Weisz, 1973). On the other hand, the reaction time is often given as the reciprocal of the first-order kinetic rate constant, r = (1/k). The ratio of the diffusion time to the reaction time √ is the square of the Thiele modulus of the catalyst,  = R k/D, and giving rise to the familiar effectiveness factor  = (3/2 )( coth  − 1). When the value of the Thiele modulus is much larger than 1, the effectiveness factor becomes much smaller than 1. For a reaction time of .01 s, and the radius of the zeolite crystal is 5 m, then the diffusivity should be above 10−8 cm2 /s. For situations when the diffusivity is much less than this value, one has to make smaller crystals or accept smaller efficiency. (c) A catalyst particle is manufactured as a composite material, consisting of zeolite crystallites with binders that are porous for diffusion, and mechanically strong to withstand the crushing pressure of a packed bed or the grinding action of a fluidized bed. The packed bed favors larger particles to achieve a modest pressure drop per foot of packed bed, controlled by the Ergun equation (Fogler, 2006) dP G =− dL gD p



1− 3



 150(1 − ) + 1.75G . Dp

On the other hand, a smaller particle diameter gives better contact, and thus better heat and mass transfer between fluid and catalyst, and the surface to volume ratio of a sphere is (6/Dp ). The compromise in requirements for a small pressure drop with a large surface to volume ratio often results in particles that are several millimeters in diameter, and the contact time between fluid and particles is of the order of a second. The fluidized bed favors particles that are less than 1 mm in diameter, to suit the multi-phase fluid dynamics. (d) In the manufacturing of useful chemicals and fuels, the two pieces of equipment that hold center stage are the reactor that converts raw material and intermediate into products, and the separator that separates and purifies the desired product from byproducts and waste streams. A continuous flow catalytic reactor, a most characteristic chemical reactors, is often designed to withstand high temperatures and pressures. The economy of scale favors ever larger reactors, where the cost of production is often scaled by the 2/3 power of the size of the reactor. The upper end of the size of the reactor is tempered by the size of the demand, and the cost of shipping the product to a list of geographically distributed customers at long distances. Reactions are generally faster at elevated temperatures, while the thermodynamic equilibrium concentration of the favored product may be better at the higher or the lower temperature, but the cost of metallurgy and heating favors the lower temperatures. The designs of reactors are done with the help of reactor models such as the piston flow reactor, the continuous stirred tank reactor, and the fluidized bed reactor (Meyers, 2004). (e) A modern oil refinery can be the size of a small city, and is located at sites that are convenient for the delivery of raw material from oil fields and other sources, as well as the trans-

port of products to customers. The Paulsboro NJ refinery has a diameter of 2 km, which is on the south banks of the Delaware River for the arrival of ocean going tankers, and also connected by railroad tracks and interstate highways. The Baytown TX refinery is even larger, with a surface area of 10 km2 . Every day, the refinery management determines what type and how much crude oil and supplies it should take in, how to operate the various pieces of equipment to manufacture and store which products at what quantity, and where to ship the various refinery products to many customers and destinations, by methods including pipeline, barges, trucks and trains, in order to fulfill all contractual agreements and to achieve the highest profit for the company. All of these must be run with safety and the public law in mind. The principal tool for doing the daily to weekly balance and optimization is the linear program, which has been in operation for half a century now (Taha, 1992). The longer range design and operations of a refinery is helped by largescale simulation programs such as the ASPEN PLUS, which dates from the 1980s. (f) The globe has a diameter of 12 000 km. The 6.5 billion people on board include all the chemical engineers and fellow workers, all their customers and stockholders, as well as their suppliers, their neighbors, their critics, and their governments. The chemical engineers need the approval and support of all these people, and must dance to their requirements in order to survive and to prosper. The globe is being burdened by a number of problems, including the ozone hole and global warming stemming from the emission of chlorofluorocarbons, carbon dioxide, and other gases (Smart and Fernandez, 1994). The oil refinery consumes an enormous quantity of energy in its operations, which is powered mostly by burning oil and gas, and the products shipped are mostly intended to be burned to produce carbon dioxide. Global warming is a slow process that involves the large-scale atmospheric and oceanic circulations on earth, the absorption of thermal radiations by atmospheric gases, the emission of these gases from natural and manmade sources, the removal of these gases from the atmosphere by natural processes such as rainfall and ocean absorption. The globe is enormous, and changes can take a century to reach its full effect (IPCC, 2004). Long-range climate models are very large enterprises, involved some of the largest computers in the world, conducted at places such as the Geophysical Fluid Dynamics Laboratory at Princeton, New Jersey, and the NASA Goddard Institute at Columbia University. Chemical engineers have limited competence in this scale. A few of these phenomena in each scale are summarized in Table 1. For each scale, a typical phenomenon is shown as well as the appropriate length and time scales, and the controlling equations. It would be instructive to put all six scales in a single graph, which should be in the log–log scale, which is given in Fig. 2 to see the big picture. The x-axis shows the time from 10−18 s (atto-second) to 1012 s (tera-seconds), covering 30 orders of magnitude. The y-axis shows the length from 10−12 (femto-meter) to 109 m (giga-meter), covering 21 orders of magnitude. The diagonal lines are lines of constant speed measured in m/s. There is no natural phenomenon faster than the speed of light, which has the value of c = 3 × 108 m/s. The

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Table 1 Six scales of chemical engineering Scale

Phenomenon

Length scale (m) −9

Primary expertise University

10

Zeolite crystal

Balance of reaction and diffusion times, catalyst effectiveness Balance of fluid–solid contact with pressure drop Convert feed into products by appropriate reaction and selectivity Balance and optimization of raw material intake and product output Global warming ozone hole

2 × 10−6 m, 2 m

10−3 s, 1 ms

3 × 10−3 m, 3 mm

1s

Schrödinger’s equation, kinetic theory of gas Thiele modulus, effectiveness factor Ergun equation

2 × 10 m, 20 m

1 h, 3.6 × 103 s

Piston flow rector

Corporate engineering department

103 m, 2 km

A day, 8.6 × 104 s

Linear programming

Corporate manufacturing department

1.2 × 107 m, 12 000 km

100 years, 3.2 × 109 s

Ocean and atmospheric flow, thermal radiation, removal of greenhouse gases and CFC

University, government, NGO, volunteer

Glope

s, 10 ps

Controlling equations

Translation and rotation, to enter zolite channel

Refinery

10

−11

Molecule

Catalyst particle Reactor

m, 1 nm

Time scale (s)

University corporate basic and applied research Corporate development

Fig. 2. Speed of events. The horizontal axis is time covering 30 orders of magnitude, and the vertical axis is length covering 21 orders of magnitude.

wavelengths of the electromagnetic radiations range from nanometer for X-ray to mega-meter for radio waves. The events chosen that take place in the six scales of Table 1 mostly fall between the speed for the line of 1 mm/s to 1 m/s, except for the molecular event of translation and rotation in vacuum which is much faster. In a dense gas or liquid, these translations and

rotations would slow down. What are the slowest events that we encounter in engineering? One candidate would be that of metal corrosion and fading of paint under sunlight, which may be as slow as 1 mm/year. In fact, when you plot the length and the lifespan of animals from men to mouse, the points lie close to that of the corrosion line.

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2. Successful historic models of coordination of the scales The scientific disciplines appropriate for understanding and solving problems in the six scales are quite different, and it is an arduous task and a mark of distinct professional attainment to achieve mastery of even one of these scales. When an engineer is assigned to a problem that involves one of these scales, the appropriate equations are retrieved and used extensively to solve the problems in hand. Engineers usually concentrate on their own areas of expertise and scale, and do not concern themselves with the work of other engineers. You let other people fix their own problems. The only reason to wander outside your own sphere of competence would be when you encounter a great opportunity or threat. Opportunity rises when there are ways to combine expertise in several scales to achieve new objectives and capabilities, leading to fame and riches. Great advances take place by taking risks, and not by following the usual paths. Threat rises when the existing system is no longer functional, and the house is on fire. There are so many new opportunities and threats in our time, so that some engineers must give up the luxury of thinking exclusively in one scale, and to find ways to coordinate the other scales. The long-term mission of any professional is service to mankind and making an impact on the world, but the shortterm rewards can be generalized as personal fame and fortune. A chemical engineer in academia has many masters and sources of funding, and can pick and choose problems to work on, and tends to favor problems that are publishable in prestigious journals to impress peers at other universities. The chemical engineer in a corporation needs to work on assigned problems, and is motivated to produce solutions that would impress the management. The management in turn has to serve the customers and impress the stock holders, as well as please the public and the government. The chemical engineer in government holds an intermediate position in effort and reward. The science of the smallest molecular scale and the largest global scale are almost exclusively in the province of the university and government workers. In the scales from zeolite crystal to refinery, corporate people play the dominant role, in mastering the appropriate intellectual tools and in providing innovative solutions, with the crucial and supplemental help of publications and consultations from university and government people. Within a corporation, the work from zeolite crystal to oil refinery is usually distributed among departments that handle operations in increasing larger scales: Basic and Applied Research, Development, Engineering, and Manufacturing. Sometimes, a successful young researcher from Basic Research may be transferred later to the Development and other departments. Arthur D. Little once said that “Chemical engineers make their discoveries in small scales, but their profits in large scales.” Within a corporation, the main pattern is people tend to develop knowledge and skill at one scale, and stay there for most of their careers. This can be compared with the music world where a few violin players become viola players, but oboe players never become tympani players. How are all these players coordi-

nated, so harmony is the result when they play together, instead of noise and chaos? Let us consider some highly successful historic methods of coordination. They are shown in Fig. 3, from the virtuoso solo performance of a master organ player, to the voluntary democratic association of the string quartet, and to the hierarchical command structure of the symphony orchestra. 2.1. The organ model: synthetic mauve Fig. 3 shows an organ as a marvelous instrument with many different types of pipes designed to make different voices, which are reached by four manuals or keyboards, plus a footboard for the feet. A single organist knows all the pipes and their capabilities, pulls this set of stops and closes others, and plays all five keyboards with both hands as well as both feet. The performance of a virtuoso organist can remind one of the Hindu gods with numerous arms. It is a marvel to encounter a single person who can carry out an entire enterprise, all the way from molecular discovery to scale-up, to manufacturing and marketing, and to do it well. In the year 1856, the chemical industry consisted of the manufacture of only a few inorganic chemicals, such as soda ash and sulfuric acid. William Perkin was an 18-year-old school boy, and he was at home during Easter holiday vacation to do experiments in his home laboratory, to develop synthetic quinine for malaria. He tried to oxidize aniline obtained from coal tar with potassium dichromate, and he found a dark precipitate in his test tube. He did not throw it away, as he treated it with ethyl alcohol and dipped a piece of silk in it, and found a brilliant purple color. This color is historically associated with Tyrian purple extracted from murex from the Eastern Mediterranean, a dye worth more than gold and used to dye the robes of Roman emperors as a symbol of authority, and senators can afford only one stripe. So what would an 18-year-old boy, who achieved mastery in the molecular scale, plan to with this discovery? One option is to publish the result, rest on the acclaim, and go on to other research projects. However, he had a different idea. With the support of his father and brother, he investigated whether English and French textile manufacturers would find this dye useful, how to develop a product that would be sellable to them, how to scale up the manufacturing from a test tube to a bucket and then to a large reactor, how to obtain sufficient quantities of aniline as raw material, how to purify the dye which he called mauve, how to build a factor to manufacture the product, and how to obtain contracts and to ship products to textile manufacturers, and how to find finance for this enterprise before income rolls in. In this venture, he had to teach himself the knowledge and skills required in all of these scales with great success. As a consequence, he was the founder of the modern chemical industry (Garfield, 2000). Are there other examples of a manytalented generalist who can learn the essentials and coordinate all activities among the scales under one skull? Charley Chaplin and Orson Welles may be examples of multi-scale people who can conceive of a story, write the play, act as the principal actor, produce and direct the movie.

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Fig. 3. Models of integration. The organ is under the command of one mind. The string quartet is a temporary volunteer organization that works by consultation and consent. The symphony orchestra is a long-term hierarchical command organization, under the will of the conductor.

2.2. The string quartet model: penicillin The string quartet is the result of a voluntary association of four players, which may be for a single performance or for a longer period of association. The four players get together to decide which piece of music to practice and to perform, what should be the order of the pieces at a concert, which concert hall at what date, what should be the tempo and how loud. When you watch a performance, you will notice that the first violin is frequently, but not always, the first among equals. They watch the expressions in each other’s eyes, so they can start a piece at the same moment of time, and keep the same tempo. When the melody goes to the cello, the violins soften their voices in accompaniment and not in competition for attention. Throughout the piece, they help each other out by timely nods and bow movements, and they end up by bowing together to the audience, as an egalitarian and voluntary group. After each performance, they can decide to break up and never play together again, or to get together to play again at another day. The history of the development of penicillin can be compared to the string quartet model, of a number of individual virtuosi playing their voluntary individual roles, without a single coordinating authority. In 1928, the bacteriologist Alexander Fleming was working in a dusty laboratory in St. Mary’s Hospital Medical School of London, and he was growing colonies of staphylococcus cultures in many Petri dishes. When he returned from a vacation, he found that colonies of staphylococcus failed to grow in rings around areas that had been accidentally contaminated by the green mold Peicillium

notatum. He found a substance in this mold that prevented bacteria growth, even when it is diluted 800 times. He was aware of the significance of his discovery, but he lacked the knowledge and equipment of a chemist or a chemical engineer, and he was unable to extract enough pure penicillin to identify the active compound involved. Pure penicillin is very unstable, and he was not able to obtain sufficient quantity to test whether it would cure sicknesses on animals or humans. His work was published, but languished for a dozen years till it was picked up by Howard Florey and Ernst Chain, chemists at Oxford University. They were motivated by German firebombing of London in World War II, and in 1939 they studied a number of antibacterial substances and decided to concentrate on penicillin. They were able to grow enough penicillin, and purified it for animal testing, and found that it is very effective. But in Britain during the World War II, they lack the industrial backing to produce penicillin in large quantities to make a difference in human illnesses. In the summer of 1941, Florey came to the US to ask for help from the National Research Council, and was sent to the Northern Regional Research Laboratory of the US Department of Agriculture in Peoria Illinois. They moved the fermentation scheme from a solid surface to liquid corn steep-lactose, and the productivity increased by a factor of a hundred. They realized that different strains of mold produce different quantities of penicillin, and after a world-wide search they found a rotten cantaloupe in a grocery store in Peoria that had the best yield of penicillin, and the yield went up 15 times. The US Office of Scientific Research and Development under Vannevar Bush took an interest in this project. A consortium of pharmaceutical

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companies was summoned, including Abbott, Lederle, Merck, Pfizer, and Squibb in 1941 to assume the challenge of industrial scale development. Productivity took a giant leap when it moved from one hundred thousand one-liter shake flasks to the 10 000 gallon deep tank fermentation method. The solvent extraction method, with pH swing from acid to alkaline, to recover the dilute concentrations of penicillin was developed by Podbielnak and Shell. Natural penicillin is fragile and has a half-life of 2.5 h even when cooled to 0 ◦ C. The method of freeze drying places the penicillin in −30 ◦ C at 0.1 torr, to sublimate and remove the water content, which preserves penicillin for extended periods of time. The War Production Board took a great interest in the project, and ample stock became available of D-Day 1944, when the allied forces landed on Normandy Beach, and some millions of units of penicillin were on hand to take care of the wounded. During his Nobel ceremony, Arthur Fleming said Florey said in 1949, “Too high tribute cannot be paid to the enterprise and energy with which the American manufacturing firms tackled the large-scale production of the drug. Had it not been for their efforts, there would certainly not have been sufficient penicillin by D-Day in Normandy in 1944 to treat all severe casualties, both British and American” (Elder, 1970). A large number of players took place in this drama, and they do not belong to the same organization, and they work sometimes in sequence and sometimes in parallel. There was really not a single authority supervising this drama, although the US Office of Scientific Republic and Development can take some credit for financing some of the development steps involved, and the War Product Board can take credit for overseeing the manufacturing scale. For the most part, the players were volunteers, driven by scientific curiosity and the desire to make a difference. The necessity of the war was also a glue in the speed and scale of this drama. Since the players did not play on the stage at the same instance of time, this drama may also be compared to a relay foot race, where one player ran for a distance, and handover the baton to another player, and so forth. This is also the model of most modern motion pictures and Silicon Valley dot.com start-ups, where a group of people get together to make a single movie or software, made a lot of money, and then disband and perhaps start other enterprises. 2.3. The symphony model: nylon The symphony is a hierarchical organization with the conductor at the top of the pyramid. He hired all the individual players, examined their past experiences, and gave them auditions; later on, he would assign them to hierarchical positions, such as the 10th chair in the first violin section with 20 players. He decides on when to have a concert, what pieces will be played at which concert hall, which soloist should be recruited when he wants to do a concerto, and schedules a number of rehearsals. On the day of the concert, the orchestra members are all assembled when he arrives last and takes a solo bow. Then he decides when to start the music, how fast and loud it should be; and he cues the individual players on when they should start playing, he hushes the orchestra when he wants pianissimo, he

speeds up his baton beat when he wants presto. At the end, he takes a solo bow again, but he singles out individual players for special applauses, and then he asks all the players to stand up. The history of the development of nylon can be compared to the symphony orchestra, all under the direction of the DuPont Company that paid for all the players and assigned tasks to them at each step of the way. In 1926, the nature of polymer as the joining of repeating units of monomers was still being debated. Charles Stine started at DuPont started a radical proposal to do basic research to discover new scientific facts, instead of the tradition policy of applying previously established scientific facts to practical problems. In 1928, he hired a young chemist from Harvard with the name of Wallace Carothers, and promised him complete freedom in research. Carothers wanted to prove that polymers were made of repeating units of monomers, and he achieved it by condensing a di-acid with –COOH at both ends, together with a dihydric alcohol with –OH on both ends, to make polyester of unlimited length. He and Julian Hill achieved a molecular weight of 6000, which he called the condensation polymer. In 1930, with the help of a molecular still to remove the byproduct of water, using a 16carbon di-acid and a 3-carbon dihydric alcohol, he was able to achieve a much higher molecular weight of 12 000, which can be drawn to produce a fiber of melting point below 100 ◦ C. It was quickly decided by the management that this polymer should be developed as a substitute to silk, as a new product is expected to be expensive to produce, and it takes only 10 g of $2/pound polymer to make a pair of stockings. But a pair of stockings needs to be ironed, which means that the melting point of the polymer must be above 200 ◦ C. A decision was made by the research team to switch from di-alcohol to di-amine as reactant, as amides tend to have much higher melting points than esters. A polyamide was developed in 1934 from a 5-carbon di-amine and a 10-carbon di-acid, to have melting points of 200 ◦ C, which was still too low. There is a poor raw material supply of decane from either coal or oil; however, the six carbon compound of benzene is plentiful from both coal and oil. Thus the development effort was directed toward a six-carbon di-acid and a six-carbon di-amine, which resulted during 1935 in nylon-66 with a melting point of 250 ◦ C, which is excellent. Many other technical problems had to be solved by the development and engineering workers, such as the spinning of the fiber from the melt instead of from solution, the method of dying the nylon to desired colors, etc. The entire development effort took 10 years, and nylon made its debut in 1940. This was a virtuoso development effort all the way from discovery to manufacturing, under the hierarchical command structure of the DuPont Company (Hounshell and Smith, 1988). What are other examples of all developments under one roof? Old movie studios such as MGM and Warner Brothers used to have lifelong contracts with the principal actors, directors, musicians, as well as cameraman and stunt people. After a movie is made, the staff is retained for yet another movie, and they do not have the freedom to work for another producer without special permission. But even the big studios are not totally self-sufficient, as they usually buy original books by independent authors.

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3. Contemporary coordination for future opportunities and threats How do we approach the question of coordination in future developments, and which of the historic models remain relevant in the 21st century? Let us examine a few contemporary examples to show what seems to be working and what needs improvements. 3.1. Inter-disciplinary research It is sometimes said that all the exciting frontiers of research today are inter-disciplinary, such as Nano-bio-environmental Engineering. Indeed, there are many such opportunities to be explored. There are people who have learned how to operate in several scales and prospered. The original concept of chemical engineering education was to combine competence of molecular scale applied chemistry with equipment scale mechanical engineering, which was a very successful concept that is still here today. That is why the chemical engineering curriculum has more required courses than any other engineering discipline. There were many other occasions when opportunity requires the grafting on of other disciplines and scales to the chemical engineering education. One of the success stories of today is in the field of controlled drug delivery with Robert Langer, who learned about polymer synthesis and properties as a graduate student in chemical engineering, and later worked at the Children’s Hospital with Judah Folkman to learn about medical problems. His synthesis of polymers for the controlled release of drugs in the human body has revolutionized the pharmaceutical industry, and gave comfort to numerous patients around the world. We certainly hope to have many more such multi-tasking virtuoso organist and mauve inventors, but we would be sorely disappointed if we sit around and wait for them to appear at a steady and adequate rate. For each multi-talented virtuoso that we can find, there are many more volunteer partnerships, of the string quartet model, that have succeeded. The field of Biomedical Engineering is highly populated with partners who pooled their expertise in different fields of Science and Engineering, and thus different scales of operation, and found innovative solutions to pressing problems. There are many federally funded programs that specifically support inter-disciplinary cooperation, and some would argue that there are too many and too narrowly focused. It remains to be seen whether such earmark of inter-disciplinary research for support is an effective method to encourage innovations. The sponsorship of more pre-proposal mixers for workers in different scales to get together and discuss may be as effective as a singles bar. Environmental Engineering also require chemical engineers to learn about the environment in the local, continental, and global scales, or to cooperate with environmental people, to develop solutions to problems. 3.2. New drug development It is sometimes said that the big pharmaceutical companies are now mainly working in the scales of drug development, animal and clinical testing, manufacturing, financing, and mar-

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keting. The task of drug discovery falls now mainly on the shoulders of university researchers and start-up companies. This is a development that follows the spectacular rise of dot.com innovators who became billionaires in their 30 s, by licensing or selling their discoveries to the large corporations. In new drugs, the development to manufacturing scales are still managed on the symphony model, of hierarchical command structure; but the relation between the drug discoverers and the big pharmaceutical companies would resemble the string quartet model, of voluntary associations for mutual benefit, for a single drug development and not necessarily for long-term associations. This coordination, or the lack of coordination, can be very dysfunctional. Some would describe the current string quartet model is not working well, as the big pharmaceutical companies have downsized their drug discovery programs, or failed to recruit the most creative graduates, but the connection to new discoveries from the universities and the start-up companies have not materialized in sufficient quality and quantity. We hear about lament about the empty pipelines in drug development, where there are not enough drugs arriving on time for either the company profit plans or the world needs. A partial return to the symphony and nylon model, and a vigorous re-establishment of in-house discovery, may be a solution to address this disconnect. 3.3. Global warming and ozone hole The hydrochlorofluorocarbons (HCFC) were developed by Thomas Midgley in 1928 in response to the need for refrigerants that are neither flammable nor toxic, to replace the more dangerous sulfur dioxide and ammonia in use at that time. The first successful ones were based on methane, and were given two numbers, such as 12: the number of fluorine NF is the last number of 2, and the number of hydrogen NH is the first number minus 1, or 0. The hard-core CFCs have no hydrogen, so they have names such as 11 and 12. The soft-core HFCs have no chlorine, so they have names such as 14 and 23 where the two digits add up to 5. After many decades of unparalleled success of marketing these compounds as refrigerants, air conditioning fluids, blowing agents, fire extinguishers, and cleaning fluids for computer, the HCFC were under fire for their role in the ozone hole, due to their inert nature which made them immune to atmospheric degradation. They rose to the stratosphere, and the chlorine in HCFC began attacking the ozone layer which deprives the earth from protection from ultraviolet radiation, especially in the Antarctic regions. Since the signing of the Montreal Protocol, the CFC are scheduled to cease production and use, to be replaced by the HCFC and eventually the HFC which do not contain chlorine. Thomas Midgley knew nothing about the ozone hole, and could not have predicted the global consequences of his molecular inventions. The HFCs were developed as replacements for the HCFC, which are based on ethane and have names such 134 and 125. The last digit is still the number of fluorine, and the last two digits add up to 7. The currently approved replacement is HFC-134a which is CF3 CH2 F, with no ozone depletion potential or ODP, but a global warming potential or GWP of 1300 in comparison with the same mass of carbon dioxide,

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which is still very high. The HFC-152a which is CH3 CHF2 is also without ODP and a much lower GWP of 140; however, it is flammable due to the abundance of hydrogen atoms. The manufacturing of these new HFC compounds are much more difficult than the older HCFC compounds, involving more than one fluorination steps of chlorinated ethylene with catalysts such as SbCl5 and TiCl4 . The separation of the multiple reaction products can be difficult, and there is hope that due to the differences in the diameters of these molecules, it is possible to find zeolites that would separate these compounds easily. This is due to the fact that the chlorine ion is much larger in diameter than the fluorine or the hydrogen ions. There is very little coordination in finding solutions to global scale problems, which originates from molecular scale events. Due to neglect, this problem is not well coordinated according to the string quartet model, and we are a long way from satisfactory solutions. In comparison, we can think of a number of musicians sharing barbecue on a faculty picnic, and some of them are found in groups discussing possible cooperation: perhaps some groups will form as a consequence and make harmonious music together—as a result, perhaps nothing much will happen and the parties remain as disconnected individuals. Can anything be done to speed up this process, and to make fruitful cooperation? Would the penicillin model work again, and we need a World Environmental Council who would not only tell us that doom is on the way, but also supply resources to support a range of research, from pie-in-the-sky basic research to applied research, till corporations can find profit motive and takeover. Where is the political leadership to put together such a Council, and to provide it with adequate funding to get the enormous job done? 4. Conclusions The different scales of chemical engineering, from fundamental knowledge in the molecular scale to the ozone hole in the global scale, are usually carried out by different experts with appropriate knowledge and skill for that scale, who can be compared with musicians who are virtuosi in different instruments. There are three historically successful models of coordination of players to make harmonious music: (a) the organ model of a single multi-talented man such as Perkin in the development of mauve, (b) the string quartet model of temporary voluntary cooperation among players such as in the development of penicillin, and (c) the symphony model of hierarchical command structure such as DuPont in the development of nylon.

The need for coordination among these scales is most evident in the face of opportunity and threat in the modern world. Such coordination is very rarely carried out successfully by a single generalist who can be creative in all scales, but far more often in the model of many specialists cooperating in a string quartet, or the model of command structure of a symphony. In the future, modern threats such as the ozone hole and the global warming transcend the responsibilities and competencies of a single unit, be it university, corporation, or government, so the recommended model of coordination is that of the string quartet: for benefit to each participant and by negotiations and consensus. However, in the case of pharmaceutical discoveries and of global warming, the string quartet coordination is insufficient, as some of the needed participants do not have deep pockets to finance their ways. We are in need of the revival a seldom used model of coordination, involving the intervention of a beneficial foundation. The contraceptive pill was developed under as grant from Katharine McCormick, since Gregory Pincus and his colleagues were unable to find grants to support their research. We need the Bill Gates and the Warren Buffets of the world to finance much needed research projects, which have been unable to obtain support from governments and industries. References Bird, R.B., Stewart, W.E., Lightfoot, E.N., 1960. Transport Phenomena. Wiley, New York. Chen, N.Y., Garwood, W.E., Dwyer, F.G., 1989. Shape Selective Catalysis in Industrial Applications. Marcel Dekker, New York. Elder, A.L., 1970. The history of penicillin production. In: Chemical Engineering Progress Symposium Series, vol 66. American Institute of Chemical Engineers, New York. Fogler, H.S., 2006. Elements of Chemical Reaction Engineering. PrenticeHall, Upper Saddle River, NJ. Garfield, S., 2000. Mauve: How One Man Invented a Color that Changed the World. Faber and Faber, London. Hounshell, D.A., Smith, J.K., 1988. Science and Corporate Strategy: DuPont R&D 1902–1980. Cambridge University Press, Cambridge, UK. Intergovernmental Panel on Climate Change (IPCC), 2004. Third Assessment Report. US Government Printing Office. International Zeolite Association, 2006. Atlas of Zeolite Structure. http://www.iza-structure.org/database/. McQuarrie, D.A., Simon, J.D., 1999. Molecular Thermodynamics. University Science Books, Sausalito, CA. Meyers, R.A. (Ed.), 2004. Handbook of Petroleum Refining Processes. McGraw-Hill, New York. Smart, B.E., Fernandez, R.E., 1994. Fluorinated aliphatic compounds. In: Kirk–Othmer Encyclopedia of Chemical Technology. Wiley, New York. Taha, H., 1992. Operations Research. Macmillan, New York. Weisz, P.B., 1973. Chemical Technology 498, 3.