Friedrich Bergius and the Transformation of Coal Liquefaction from Empiricism to a Science-Based Technology Anthony N. Stranges Texas A8M University, College Station, TX 77843 The life history of an invention is similar to that of a human heing, in that the years of childhood are the most free from trouble. -Friedrich Bergius, The Melehett Lecture J.Institute Fuel 1934,8,69 An interestine theme in the histom of science is to exnlore the different ways in which technology has become increasinelv scientific. Prior to the neriod 1876-1900 mosr develoom&s in chemical, metall;rgical, petroleum, or electrical technology were empirical and not the result of applying scientific principles to their study. The high-pressure synthesis of ammonia was the first of the science-based chemical industries to emerge, and its success led to other highpressure investigations, one of which was the reaction hetween hydrogen and coal to give a liquid fuel. Friedrich Bertius (1884-1949) spent 13years investigating the conversion of coal to liquid fuels, and his work is a good example of its transition from empiricism to science in the first two decades of the 20th centurv. Bergius was born in ~oidschmieden,near Breslau, Germanv, in 1884. His father owned a small alumina-nroducine plant i n which Bergius acquired a familiarity with chemicz technoloev a t an earlv ace. His education in the nractice of chemical i e r h n n ~ o ~ c o ~ t i n ulater e d when his father sent him to Mulheim in the Ruhr district fur six months to ohserve the operation of the Friedrirh-Wilhelmshutte, a large metallurgical factory. Following hisstav in Milheim Hergius enrolled in the University of Breslau and then i.eipzig from which he received the PhD in chemistry in 1907 ( 1 ) . The 1880's also saw the emergence of theoretical or physical chemistry as a formal hranch of chemistry. Its investigations included elertrochemistrv. chemical eouilihria. catalvsis, and thermodynamic studi;; at high preLsures. H'alrher Nernst (1864-1941) and Fritz Haber (1868-1931) were two of the leaders in the new physical chemistry, and it was their expertise in the high-pressure study of gaseous reactions that caught Bergius's attention. Thus immediately after Bergius graduated from Leipzig he spent a year studying with Nernst in Berlin and six months with Haber in Karlsruhe. With Nernst and Haher, Bergius worked on the synthesis of ammonia and its equilibrium at high pressures. At this time. 1909. chemists were iust herinnine to recoenize the influence of pressure on reaction rates, in particular how pressure influenced a reaction's yield. With the mass action law (1867) of Cato Maximilian Guldberg (18361902) and Peter Waaee (1833-1900) and several ex~erimental determinations o f t h e equilibrium point a t different temperatures and pressures, they could calculate the composition of an
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Whether Bergius's unpuolished papers were lost or destroyed in me 1920's after he ceased work on coal liquefaction or dJring the World War I1 years is Lnknown. Tnere may be some Bergius papers n the large collection of German synthetic fuel documents in the archives at Texas A&M University. I am currently cataloging these papers and cannot say at this time whether they contain anything on Bergius.
Bergius ca. 1910 equilibrium mixture over a broad temperature and pressure range and determine the reaction conditions that gave the maximum yield of products (2). During his 18-month association with Nernst and Haher, Bergius said that he tried his hand "in these laboratories at syntheses by high-pressure techniques, with the then imperfect apparatuses and with little success." Yet the time he spent with Nernst and Haber clearly provided the impetus for his later investieations. Bereius had made a commitment to work in this new field saying as much in the foreword of his Habilitationschrift (1913) in which he argued that introducing to the laboratory new experimental high-pressure methods and instruments would lead to . Dromess - in chemistry (3). While Nernst and Haber confined their investieations to gases, Bergius expanded high-pressure researrh to include the reactions of gases with liquids and solids, svecificallv the reaction of hydrogen gas with crude petroleum, coal tar; and coal. His work opened an entirely new field of high-pressure reactions and was the beginning of a new science-based technology, the production of liquid fuels from coal. For his invention, which Bergius hoped someday would reduce significantly or perhaps even eliminate Germany's almost total dependence on imported petroleum, Bergius received the Volume 65 Number 9
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1931 Nobel Prize in chemistrv. His svnthetic fuel nrocess underwent extensive development in Germany and Britain in the 1930'sand earlv 1940's resultine in thecunstruction of 13 large plants that produced milli&s of barrels of petroleum from coal and coal tar. After World War I1 the 12 German plants were dismantled or modified to refine crude petroleum because the Allies prohibited any post-war production of synthetic fuels in Germany and because of the process's high cost (4). The single plant in Britain was a victim of economics (5). More recently in the 1970's, the aovernments of several nations including the United States ittempted to establish synthetic fuel kdustries but once again high costs caused their abandonment (6). What were the major prohlems of coal liquefaction technology to which Bergiusapplied the prinripleaof theuretical or physical chemistry beginning in 1913? In his initial experiments Bergius had shown that in agreement with Henri 1.e Chatelier's princinle (18881,an increase in pressure favored liquefaction and that a pressure of 200atm gave a yield of 70-85%. ~
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Calorimetric measurements carried out in a high-pressure autoclave also indicated that the reaction was exothermic and very sensitive to temperature change. At high temperatures coke formed reducing the liquid yield, whereas low temperatures led to a slow reaction rate. The first of Bergius's problems was, therefore, to design a high-pressure heating apparatus that permitted accurate temperature control, to within 5 1 0 "C of the liquefaction temperature, 430480 O C . Rergius carried out a large numher of experiments of hoth theoreticaland practial importance in investigating the influence of temperature (as well as pressure and time) on the liquefaction reaction (7).Rut his puhlished papers contain only the conclusions of his studies and unfortunately few samples of his data and calculations. There is also no known archival source of Bergius's unpublished papers or laboratory and plant reports.' The publication that shows best Bergius's application of recent theoretical developments is his 1913 dissertation on the calcium peroxide dissociation and the formation of artificial coal. In this lengthy study, which was Bergius's Habilitationschrift, he included extensive tables of temnerature and oressure variations and used Nernst's recently introduced approximation formula to calculate hoth the heat of reaction and the dissociation pressures for given temperatures (8).The Nernst approximation formulaappears below in which& and m a r e the equilihrium constant and the heat of reaction, respectively; T is the temperature in degrees Kelvin; x u is the difference between the sum of the moles of gaseous products and gaseous reactants, Cis Nernst's "conventional chemical constant" calculated from vapor pressure measurements and an empirical vapor pressure equation, with values between 2.5 and 4 for most substances; and x v C is the difference between the sum of the products' conventional chemical constants and that of the reactants (9). log K, =
4.57T
+ xu1.75 log T + ZvC
Because Bergius had carried out his high-pressure investigations on calcium peroxide and the formation and liquefaction of artificial coal shortly before attempting to liquefy natural coal, he probably continued to use this same experimental-theoretical approach in his research on coal liquefaction. Clearly, it represents only an extension of the methodology Bergius had adopted in his earlier high-pressure work, and it is most likely what he did to determine suitable reaction temneratures and oressures and therefore to desian . an appropriate temperature-control apparatus. The temnerature-control apparatus that Bergius finally day plait had in operation by 1921 in his bne metric ton
750
Journal of Chemical Education
at Rheinau near Mannheim used the heat-exchange principle with relatively unreactive nitroaen or carhon dioxide aas i s the heat-exchange medium. 1t;equired enclosing e&h reactor in a steel container or jacket, heating and compressing the heat-exchange gas to the pressure inside the rewtor, and then circulating the gas in thespace between the reactor and jacket. Equalizing the two pre&res was important, for the strength of the reactor's wrought-iron or pressed-steel walls decreased considerahlv at the working temnerature. 400-500 'C. Applying exteribr pressure also permitted con: struction of a reactor with relativelv thin walls. because onlv the outer jacket's walls had to withsknd the high pressure. A water column, one end connected bv a oine to the reactor. the other end to the jacket space, indfcaied any pressure differences. This indirect heating arrangement permitted very accurate temperature controiand was highly kconomic, for it recovered all the heat exchanged in the process (10). Asecond major problem that Bergius faced was the generation of hydrogen gas in quantities sufficient to liquefy coal. Once again Bergius applied the principles of chemical equilibrium to modify the temperature and pressure conditions of the water gas reaction and increase its hydrogen production. The water gas reaction was a well-known reaction hetween coke and steam that nroduced hvdroeen. . " . bv- far the most expensive raw materialked in the conversion of coal to petroleum. I t was cheaper than the electrolvtic process of . . obtaining hydrogen from water, hut i t had two serious disadvantages. As usually carried out, the reaction gave a mixture of hydrogen and carhon monoxide gas only a t a high temperature, 900 'C, and it required expensive equipment to comoress and liauefv the carhon monoxide for senaration. For coal liquefaction to he a technological and economic success, Bereius had to eliminate these disadvantaees and develop an inexpensive and reliable source of hy&ogen. From his equilibrium studies he found that running the reaction a t a much lower temperature, 300-600 OC, hut at a pressure 200 times higher, favored the production of carbon dioxide and hydrogen. This reduced the formation of carhon monoxide and the problem of separating it from hydrogen. He could then remove the carbon dioxide through ahsorption in lime (11).
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+
Ci,, HzOi,, e CO,,, + H,izl C,, 2H,0i,, s COZi,,+ 2H,
+
t
= 900 'C
t = 300-600 'C
The composition and structure of coal was another major ~ r o h l e mto which Bereius anolied the principles of theoretical chemistry to aid h< rese&h on c o d liqu~faction.In 1911 chemists knewvew little about the composition and molecular structure of coal. Many believed chat coal was merely carhon mixed with hydrogen-containing impurities. The researches of Bergius and others in 1910-1913 established, however, that coals and lignite contained two kinds of chemical compounds, carbonaceous compounds and bituminous compounds, and that structurally there were three, four, or five fused rings of carhon atoms:~y 1914 Bergius's investigations with hundreds of different coals showed that the younger brown coals and lignites were most suitable for liquefaction. They had a carbon content of less than 85%in the ash-free coal, and, on liquefying, their hydrogen content rose from about 6 to almost 15%..Hecould not liquefy anthracite or any coals that had an ash-free carhon content exceeding 85% (12). With some idea of the composition and structure of coal anda clear graspof the tempeiatureand pressureconditions required for its liquefaction, Hergius proposed a mechanism for-the reaction. He sueeested that liauefaction occurred in two stages: (1) converlik of the coai into heavy pitchlike oetroleum hvdrocarhons as a result of addine hvdroeen atbms a t 3 0 0 4 0 OC and 200 atm and (2) crack&"or silitting of the heavy pitchlike hydrocarbons into lighter liquid hy-
This hrief study on Bergius is only one example illustratinz how chemical technolon became increasingly scientific. H: was part of a movement that began in the late 19th century with the work of J. Willard Gihbs (1839-1903) a t Yale, Wilhelm Ostwald (1853-1932) in Leipzig, Jacohus van't Hoff (1852-1911) in Amsterdam, and Svante Arrhenius (1859-1927) in Uppsala. Up to that time the sciences, including chemistry, were mainly empirical. There were few scientific principles or theories to guide the experimentalists in their work. Technology was even more of an empirical experience. When Gihhs published his important phase rule in 1875-1876 be provided the theoretical foundation that transformed mineralogy, metallurgy, alloying, steel making, and other chemical technologies into more exact sciences (13).Within a few years, in 1887, Ostwald, van't Hoff, and Arrenhius established the Zeitschrift f i r physikalische Chemie, the first journal devoted to theoretical research in chemistry. Six years later Nernst published the first edition of his famous Theoretische Chemie and then his heat theorem in 1906. Bv 1909 Haher had a . n.~ l i e dthermodvnamic principles in synthesizing ammonia from its elements. His investigations led to the industrial production of ammonia and the emergence of one of the first science-based technologies. Other applications of theoretical principles to chemical technology, among them the coal liquefaction process of Friedrich Bergius, rapidly followed. Acknowledgment
Bergius. his wife Margareth. and daughter Renate, cs. 1915.
drocarbons a t about 450 "C. In other words, hy 1914 Bergius had established that coal liquefaction was both an addition and a cracking reaction (12):The next step in the transition of coal liquefaction from its empirical beginning to a sciencebased technology would be the introduction of catalysts to accelerate each reaction, hut Bergius bad neither experts skilled in catalysis nor the funds to investigate catalytic influence on the reaction rate systematically. Nevertheless, when Bergius concluded his research on high-pressure coal liquefaction in the mid-1920's he had shown the value of applying scientific principles to a new technology. His use of chemical thermodynamics and equilibrium studies enabled him to determine the temperature and pressure conditions that gave the greatest yield of liquid products. His study of coal's composition and structure showed the probable arrangement of its atoms and therefore which bonds between the atoms were most likely to break during liquefaction. Bergius then could propose a possible mechanism for the reaction and begin a search for suhstances to catalyze it. His research marks the beginning of coal liquefaction's transition from an empirical technology to a more exact science.
The Center for Energy and Mineral Resources, Texas A&M University, and the National Science Foundation Grant No. SES-8520001 have provided funding for this research. Special thanks to Kurt Irgolic, Department of Cbemistry, Texas A&M University, for his assistance in preparing this paper. Literature Clted -
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2. Ihde, A. J. The Deualopment of Modern Chamiatry: Harper 8 Row: New York, 1964, pp 408-410: Hiebert, E. N. D i c l i o ~ r yof Seienfific Biography: Seribnars: New York, 1970-1980: Val. 15, pp 432A53: Cropper, W. H. J. Chem.Edue. 1987.64.3-8. 3. Bergius, F.Die Anluandvng hoher Drurke beirhomiarhen Vorgnngan und eineNmhbildungdaaEnl~Mungspmzoss~sdar Sfsinkohle:Knapp:Halls, 1913: p 1;Brrgius. F. J. Soc. Chem. lad. 1913.32.4624167. 4. Sfrsnees.A. N. J. Chrm. Edue. 1983.60.617-625. A. N T ~ C ~ ~ culture O I . 1985,26,726757. 5. str.& 6. Strange8.A. N. J. Chem.Educ. 1983,60,617-625. 7. Bergius, F. Fuel 1927,6,213-216. 8 Bergius F. Die Anmendung h d e r Drucka bei chemisehen MrgongPn und sine Nachbildung des Enlrlohvngaprozess~sder Stsinkohla; Knepp: Halle. 1913; pp 2629. W - W
9. Nernst, W. Narhrichlm "on der Koniglichen Cesellrchft dor Wkso"4ehoften ru cattingen 19M, I; ema at. W. ~ h e ~ Heor e w ~ h m r e m ; ~ a r0.. r , ~ransl.;Methuen: London. 1926;pp 128-15< Nernst, W. Theoreticd Chemistry SUl-10th edn.. Codd, L. W., Transl.:Msemillan: London. 1923: pp 811431. 10. Bergiua, F. U.S. patont, 1,592,772, 13 July 1926 (filed 30 Aug. 1921): Bergius and L6iIlfner. S.,British patents 192,849 and 192,850.8 Mar. 1923 (filed 30 Nov. 1921). 11. Bergius,F.DieAniuondunghohor Drucke beirhrmisehen Vargong~nundeinaNnchbildungde~Enlsrehungsprazess~sdsrSt~inkohl~; Knapp: Halle, 1913:pp32-33:J. Soc. Chem. Ind. 1913.32.462-467, 12. Berglus F. Pmcmdings of the Intzrnofionai Conferenre on Bifvminova Cool, 1926; Camepie Institute: Pituburgh, 1927: pp 102131. . Tronr. Connecticut Aeod. Arts Sci. 1875-1878, 3, 108-248, 343-521; 13. Gihbs, J. W Bumatead. H. A.: Van Name. R.G.. Eds. Thc Scientific Pooera o i J . Willard Cibbs: Dover: NckYork, 1961; vol.1, pp 55-353.
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