The Separate Development of Chemical Engineering in Germany

14 The

Separate

Engineering

Development

in

of

Chemical

Germany

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 8, 2015 | http://pubs.acs.org Publication Date: June 1, 1980 | doi: 10.1021/ba-1980-0190.ch014

1

KARL SCHOENEMANN Technische Universität Darmstadt, D 6100 Darmstadt, Federal Republic of Germany Whereas in the United States chemical engineering has been developed as an autonomous discipline towards the end of the last century, it generally has been rejected in Germany until approximately 1960. Process development and plant design were done by teams of conventional chemists and mechanical engineers. During the last two decades inter national exchange of experience increased and finally brought about an approximation of standpoints. In Ger many today the field of American chemical engineering is covered by several professions with different educational backgrounds.

"T\uring the three and a half decades after World War II chemical -"^engineering, as developed in the United States, has been under much discussion in Germany (1-11). Until about thefirstpart of the 1960's the American concept generally has been rejected. The United States, which was at the beginning of chemical industrialization in the 1880's, already realized that conventional chem istry and mechanical engineering would not suffice for the novel tasks of developing chemical production processes and that the gap had to be closed by means of a new autonomous discipline. In Germany these tasks were solved through the teamwork of conventional chemists and mechanical engineers, both thinking in their own philosophy and working according to their own methods. As late as 1952, E. L. Piret (12) of the University of Minnesota, with his large amount of experience in education and industry, complained about the European lack of understanding with regard to the importance of chemical engineering for chemical industry: Current address: D 8730 Bad Kissingen, Heinrich von Kleist-Str. 2, West Germany. 0-8412-0512-4/80/33-190-249$05.75/l © 1980 American Chemical Society 1

In History of Chemical Engineering; Furter, W.; Advances in Chemistry; American Chemical Society: Washington, DC, 1980.

250

HISTORY O F C H E M I C A L E N G I N E E R I N G

" O n the continent one can count on the fingers of one hand the educational centers giving what approaches our con cept of chemical engineering education. At not one of these the student receives the integrated training . . . which we consider important. The professional status . . . existing in the field of chemistry and in the other branches of engineering on the continent and in America does not present nearly as sharp a contrast as in chemical engineering" (12).


Piret considers: ". . . the retarding influence of strongly entrenched interests and rigid tradition working within the universities and tech nical schools and even in the industries themselves to be worse . . . than the effects of World War II" (12). The federation of the German chemical industry still rejected the introduction of autonomous chemical engineering in 1954 (13). The contrast between the American and the German concept became obvious at the First European Conference of Chemical Engineering Education in London i n 1955. A t this conference the author was the only European representative who advocated the American concept (2, 5). In 1956, a group of American Fulbright lecturers gave their impression in a report i n Chemical and Engineering News (14) with the headlines: "Chemical Engineering N e w to the United Kingdom, Unknown in Germany— Germany Does Not Agree—Darmstadt Differs in A i m s . " After this culmination the contrast has turned more and more into a distinct approximation of the differing standpoints as a consequence of the growing international scientific exchange and of the increasing similarity of industrial tasks leading to similar technological solutions i n the various countries (15). However, the necessary linguistic and institutional measures have not been taken yet. As before, two great professional institutions exist i n Germany that represent chemical engineering scien tifically, economically, and socially: the Deutsche Gesellschaft fur Chemisches Apparatewesen ( D E C H E M A ) and the Gesellschaft fiir Verfehrenstechnik und Chemisches Ingenieurwesen (GVC). D E C H E M A is concerned more with the chemical aspects of chemical engineering while G V C with those of mechanical engineering (16). Both institutions have established very active working parties for the manifold branches of chemical engineering. Some of them have developed into joint units, each w i t h a common chairman. A t the universities both traditional lines of education, namely that of engineering with its mechanical, civil, and electrical divisions, and that of chemistry with its organic, inorganic, and physical divisions, have been continued, of course. D u r i n g the last few decades the departments of both faculties have, though maintaining their leading philosphy, con tributed to bridging the gap by establishing specialized branches that are



14.

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Chemical Engineering in Germany

251

designated by the chemists as "technical chemistry" and by the engineers as "verfahrenstechnik." A t the various universities the right understand ing of chemical engineering differs considerably. The German word "verfahrenstechnik," literally to be translated as process technics, can be misunderstood easily; Americans should not try to translate it. W h e n this expression was coined prior to W o r l d War I, it was practically identical with unit operations. Now it is used by engi neers to express that their methods can be applied to any type of industry such as mechanical, chemical, food, oil, and other industries. The German technical chemist by using this word means the development of a process whose core is the reactor which is decisive for the chemical conversion and thus for the whole arrangement of the plant for pro duction cost and profitability. E v e n in industry, research and development still are organized mostly i n separate departments for technical chemistry and Verfahrens technik whose members cooperate, but may also be rivals. O n l y about ten years ago three German universities—Erlangen, Karlsruhe, and Dortmund—founded independent departments of chemi cal engineering according to the American concept. During the past several years the novel problems arising from the shortage of raw materials etc. have enhanced the demand of chemical engineers con siderably. Unemployed organic chemists are placed in temporary courses into chemical engineering—circumstantial evidence that the rejecting attitude described above has changed completely (17). The long-range development i n the German Democratic Republic does not greatly differ (16).

An Illustration of the Historical Development of German Chemical Engineering W e may now ask: what are the reasons for this separate development in Germany and what are its consequences? The emergence of the facts is so manifold and often accidental that a survey of theory and practice (taken as a whole) can be given only intuitively and subjectively. Such a picture then can be compared with the more systematic development in the United States as for instance described by O. A. Hougen in his report Seven Decades of Chemical Engineering (18). According to the author's experience gained during nearly 60 years of activity, half in industry and half at the university, the development of American and German chemical engineering presents itself in Figure 1. About 1890, which was prior to the synthesis of alizarin and indigo, the U n i t e d States enjoyed a position of organizational superiority because they recognized the importance of chemical engineering as an independ ent discipline.


HISTORY O F C H E M I C A L ENGINEERING


252



14.

SCHOENEMANN


253

At that time education i n pure chemistry had reached a high stand ard i n Germany where since the beginning of last century the technical schools teaching trade methods i n order to support the textile industry and their auxiliary productions (lead-chamber sulfuric acid, hydrochloric acid, the Deacon process, etc.) had affiliated chemical departments that took up Liebig's system of chemistry, and later on conventional physical chemistry and mathematics. In time these schools developed to such a degree that towards the end of last century they were technical schools of university level. The same branches had been introduced in all of the traditional universities. The decisive impetus for chemical engineering came from the dyestuff industry. As shown by the formulae of alizarin synthesis i n Figure 2, fuming sulfuric acid was required which at that time was produced by roasting ferrosulfate. In view of its exorbitant price, Rudolf Knietsch of B A S F , the leading chemist of that time, was directed to the production of S 0 b y catalytic oxidation of S O with air (19). The son of a blacksmith he first became a locksmith, then an engine driver; later on he found the time to graduate from high school and finally to study chemistry. 3

a

ANTHRACENE

• Ο ANTRAQUINONE Ο H S0 2

4

+ S0

3

• 3

Η

ANTHRAQUI Ν Ο Ν Ε SULFURIC ACID

Ο ΝαΟΗ

• Ο

OH ALIZARIN

Ο

Figure 2. Synthesis of alizarin



254


HAAS*

Figure 3. KnietscKs original diagrams of SO3 catalysis Although Knietsch's original diagrams of his laboratory experiments in S 0 catalysis are nearly 100 years old, they look rather modern. The sequence (see Figure 3) representing the degree of conversion i n its dependence on the various reaction factors proves that he had a clear insight into the complex interaction between reaction velocity and equi l i b r i u m . F o r this reaction he invented the ingenious tube-bundle reactor whose feed for the fixed bed inside the tubes was preheated in countercurrent by the hot reaction mixture outside of the tubes. Supported by the profits made with alizarin, Heinrich von Brunck of B A S F (20, 21) could tackle the synthesis of the "king of dyestuffs" of that time—indigo. Several processes were tried out, and success came only after 17 years when 18,000,000 marks had been spent on this develop ment, an amount of money that equaled the capital stock of the company. The indigo synthesis demonstrates how in an admirable effort a company summons all of its energy for years in order to achieve one single objec tive. The intermediates of the abandoned indigo processes became the origin of independent productions thus prompting industrial diversifica tion (see Figure 4). 3



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The success achieved with indigo encouraged B A S F to cope with larger tasks and helped to raise funds for developing the catalytic highpressure synthesis of ammonia, then the big world problem. This syn thesis, as realized by Fritz Haber and Carl Bosch (20-25) is known by everyone. Its fundamental achievements mark the turning point on the way leading from the traditional batch processes to modern continuous catalytic mass production. Today reactor capacities have reached 1700 tons/day at 2.4 m i n diameter and 34 m i n length and at a pressure of 330 atm and a temperature of 500°C. Historically it is of interest that i n 1905 C a r l E n g l e r , head of the Chemical Department of Karlsruhe Technical School, i n his position as member of the board of B A S F , invited the attention of that company to the ammonia experiments of his assistant F r i t z Haber. It is important for the further development of chemical

0

NH2

coo*

ÏÏ.

'

(f^NHCHg'COQM

VJ,

CIC^COOM

Cl-CM -CH^OH

C00H

2

r

Q[

Figure 4. Consecutive products of the indigo syntheses



256


Figure 5. Coal hydrogénation plant in 1927 engineering that A l w i n Mittasch (22) developed the principle of the mixed catalysts which i n our times have had such a far-reaching influence on chemical syntheses. The columns of Figure 1 indicate that further progress was made in Germany from 1925 until 1950. During this period the development of high-pressure techniques proceeded along two different lines. One was the hydrogénation of coal and crude oil bottoms into motor fuel as fundamentally solved by Friedrich Bergius (26), who together with C a r l Bosch was awarded the Nobel Prize in 1932. In 1927 the first industrial gasoline plant with a capacity of 100,000 tons/year (see Figure 5) was erected by B A S F , at that time part of the I G Farben group (27). It is impossible to mention all of the problems involved such as those of the steel quality, of catalysts resistant to sulfur, of pumping ground coal i n the form of slurry, of exactly controlling the enormous reaction heat, and of control technique, etc. However, coal hydrogénation was no economic success as a consequence of the competition of the cheap excess production of motor fuel caused by the improvement of oil field explora tion and crude oil cracking. In comparison with the indigo synthesis, development cost reached an even higher level, amounting to 40% of the



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257

share capital of the whole I G Farben group, which was comprised of six big works (28). In the following decades, however, when high-pressure hydrogénation was applied to the oil industry, great successes were achieved, for instance the increase of gasoline yield by hydrogénation of residues, the aromatization of gasoline, and the production of pure aro matic and unsaturated hydrocarbons. In 1921, Fritz Winkler discovered, i n connection with the highpressure syntheses, the principle of fluidization, a further valuable con tribution to chemical engineering. Starting from Winkler's first rough sketches (see Figure 6) the realization of a generator gas capacity of 50 000 m / h r (see Figure 7) required only ten years (20, 21). The application of oxygen from the rational mass production by the Linde-Frànkl air liquification allowed the production of water-gas and hydrogen. The whole field of synthesis gas production from coal—the only raw material being available i n Germany—is a typical German development. The fiuidized-bed principle was extended to the catalytic cracking of petro l e u m , the roasting of pyrite, the oxidation of naphthalene into phthalic acid, and the production of olefins, etc. The other line of development in high-pressure techniques were the syntheses of methanol and isopropyl alcohol. Later on, in combination with olefin and acetylene chemistry these syntheses opened up the great field of highly selective catalytic processes for pure organic compounds. 3

Figure 6. Fritz Winkler s sketch of his discovery of thefluidized bed



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Figure 7. Fluidized-hed gas generator of50,000 m /hr capacity 3

First there was the chemistry of olefins which owing to Germany's oil deficiency could not be obtained by cracking, but had to be produced by hydrogénation of acetylene originating from coal via calcium carbide. At the beginning of the 1920's, acetylene was used first for addition reactions at normal pressure; the most important product was acetaldehyde which via aldol, 1,3-butanediol, and butadiene led to synthetic rubber. Other important products were ethylene oxide, acrylic esters, styrene, etc. A t the end of the 1920's, Walter Reppe (29, 30, 31, 32) started his experiments on catalytic reactions with acetylene under pressure. O n the basis of his studies, which soon were known all over the world as Reppe chemistry, it was possible to construct complicated organic com pounds of high value from simple building stones. F r o m the standpoint of the chemical engineer the greatness of his achievement was that the



14.

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259

dangerous manipulation of acetylene under pressure from which every one had recoiled could be realized and steadily improved by means of minute experiments, often carried out contrary to the safety instructions of that time. The conditions on which the various kinds of acetylene decomposition, as e.g. slow reaction, explosion, and detonation, origi nated were investigated for each synthesis reaction. Thus safe operating conditions were created, for instance by always maintaining definite par tial pressures and avoiding empty volumina of vessels and tubes. In 1940, a large plant for 30,000 tons/year of synthetic rubber was erected on the basis of acetylene and formaldehyde (see Figure 8). It was the first industrial application of the trickle-bed reactor. After the produc tion of synthetic rubber had been abandoned, butynediol became the

Figure 8. Butynediol plant


260

HISTORY O F C H E M I C A L ENGINEERING

Table I . Oxo and Reppe Syntheses ^ *

1

CH -CH=CH 3

2

CH -CH -CH -CHO 3

2

2

d

+ CO+H2

C H - C H " C H - CH 0H

L

3

2

2

2

BUTANOL

CH 0H+C0

2.

C

3

0

/

» CH C00H

J

3

ACETIC ACID

3.

CO+HOH

NiBr

respect.* H OR

CuJ

CH3BCH+

U.

CH = CH-C00H

2

2

-C00R


ACRYLIC ACID

5

CH =CH -CO HOH 2

2

ST^'

• CH - CH-COOH

H

3

200 C 300at W

6.

CH -CH-CH *3CO 2H20 3

J

+

2

L

* « * » 5 + org base

The Separate Development of Chemical Engineering in Germany

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