Hydrogenation of coal by Friedrich Bergius
This article appeared at the request of readers who were very interested in German technical subtleties. Here an interest arose in a topic that is quite well known - the production of motor fuel from coal. Quite a lot has been written about this, but, as a rule, without much detail. There were several methods, and I will devote special attention to them. Now the subject of consideration is the technology of coal hydrogenation, developed by Friedrich Bergius and improved by Matthias Peer, better known as the Bergius-Peer process.
Oddly enough, little is known about it, despite the fact that it was the most extensive coal-to-fuel technology used in Germany during the war. Even in Anton Lübke's detailed 1938 work "The German Raw Material Miracle", which describes almost all of Germany's achievements in raw material replacement, it is written that this process is expensive. And in post-war literature, including specialized literature, not much has been written about this process. Apparently, this is not without reason.
It all started with oil
The founder of technology, Friedrich Bergius, was born in Goldschmieden, near Breslau, into a family of hereditary German professors. Among his ancestors were Conrad Bergius (1544-1592), professor of rhetoric at the University of Wittenberg, Johann Bergius (1587-1658), professor of theology and rector of the University of Frankfurt (Oder), and Karl Julius Bergius (1804-1871), professor of economics at the University of Breslau. His father, Heinrich Bergius, was a chemist and owner of a factory in the suburbs of Breslau for the production of alumina, which was then used in the production of ceramics and porcelain. So Friedrich Bergius went into chemistry, studied at the University of Breslau, and then became interested in physical chemistry, that is, processes at high temperatures and under high pressure. He became an expert in high-pressure apparatus and in the laboratory of the famous chemist Fritz Haber in Karlsruhe he designed an autoclave for 300 atmospheres of pressure.
Friedrich Bergius
Bergius was initially involved in fundamental research into chemical reactions under pressure and temperature, but in 1910 his colleague Ludwig Landsberg, who became director of the Aktiengesellschaft für Petroleumindustrie in Nuremberg, led Friedrich Bergius astray, interested him in oil cracking and provided him with funding.
This circumstance is rarely mentioned, but Bergius's technology began with oil refining. The fact is that even in those days there was little good oil that gave a large yield of gasoline and gasoline fractions. While kerosene was mainly distilled from oil, few people cared. Meanwhile, the rapid growth of the automobile fleet led to an increase in gasoline consumption, and oil refining could not keep up with the growth in demand. The most far-sighted people, like Ludwig Landsberg, saw a way out in the development of technologies for refining heavy oil or heavy residue.
Cracking was already known then, not distillation, but pyrolysis of oil at a temperature of 450–550 degrees. But the “heat it up more” method did not always work and often produced a large amount of petroleum coke, clogging the columns. This is the problem Bergius tackled.
By May 1913, he had concluded that this problem could be solved by feeding highly compressed hydrogen into the autoclave, which would break down the heavy molecules into smaller ones and form low-boiling fractions. In fact, Bergius was the first to apply hydrocracking technology, which was developed in oil refining after World War II.
At the same time as these works, Bergius obtained artificial coal. Before him, many chemists tried to turn wood into coal, but they only got coke, not an analogue of natural coal. In his autoclaves, Bergius managed to solve this problem, and he was able to obtain an exact analogue of natural bituminous coal from wood. These studies led him to the idea that coal is a structure of unsaturated hydrocarbons, therefore, coal, like heavy fractions of oil, can attach hydrogen and turn into lighter fractions, such as diesel fuel, kerosene, gas oil and gasoline.
When there is hydrogen, why not experiment?
Thus, oil and coal were processed side by side using the hydrocracking method. But here Bergius faced another problem - a source of hydrogen. Electrolytic hydrogen was very expensive and required hydropower, which was in short supply in Germany. In Germany, hydrogen was obtained from water gas, obtained by the reaction of water vapor and hot coal. However, to separate hydrogen from carbon monoxide, it was necessary to liquefy the carbon monoxide, that is, cool it from +900 degrees to -192 degrees and compress it. This is an energy expenditure.
Bergius began to look for a simpler and more economical way to obtain hydrogen. He thought that under pressure he could oxidize carbon monoxide to carbon dioxide, which was easily absorbed by limestone. However, he discovered that under a pressure of 200 atmospheres and heating of 300-360 degrees, water, remaining liquid, behaves like an acid and reacts with the steel walls of the autoclave, releasing hydrogen. Bergius designed a special autoclave with iron reacting parts and built a small workshop in the suburbs of Hanover, which had six units of 40 liters each, producing 28 thousand liters of hydrogen per hour.
Using this source of hydrogen, Bergius conducted a series of experiments in which he showed that he could hydrogenate any oil, obtaining only gaseous or liquid products, leaving no coke. 50% of the oil was converted into gasoline.
Others would have stopped there, but then the devil nudged Bergius to experiment with coal. He took the previously obtained artificial coal and combined it with hydrogen under the pressure of 150 atmospheres and a temperature of 400-430 degrees. 80% of the coal turned into gas, liquid and a solid fraction, but soluble in gasoline. They immediately tried natural coal - the same result. In the fall of 1913, Bergius patented the technology of coal hydrogenation.
Heavy industrial beginning
During the First World War, Bergius tried to turn his laboratory method into an industrial technology. In 1915, he received funding and began building a continuous-cycle plant for converting coal into liquid products in Mannheim (70 km south of Frankfurt am Main). The construction of the plant cost 30 million Reichsmarks, and about 8 million Reichsmarks were spent on current expenses. But Bergius was unable to establish industrial production! Only in 1919, when the war was over, did he succeed in hydrogenating first crude oil and then coal.
The first problem was the continuity of production. Feeding coal and hydrogen into the reactor under high pressure was a serious technical problem. In general, in 1921, Bergius managed to design a reactor in which coal was fed by a special piston.
The second problem was temperature control. Hydrogenation produced heat, and increasing temperature led to coke formation, while decreasing temperature led to a decrease in the reaction rate. Bergius used nitrogen or carbon dioxide as a heat exchange gas pumped into the reactor, and by controlling its pressure, he could control the reactor temperature quite accurately and easily.
Having finally built the plant, Bergius tried about two hundred grades of coal in 1921-1925. For example, 100 kg of crushed coal was mixed with 40 kg of heavy oil, 5 kg of iron oxide powder was added as a catalyst and a means of removing sulfur compounds. 5 kg of hydrogen were added to the reactor. The result was 20 kg of gas (excess hydrogen, methane and ethane) and 128 kg of liquid and solid matter. When distilled, the liquid yielded 20 kg of gasoline with a boiling point of up to 230 degrees, 10 kg of liquid with a boiling point of 230-330 degrees and 51 kg of heavy oils with a boiling point above 330 degrees.
Incidentally, it was during this period that Bergius was the first to use steam conversion of methane and ethane into hydrogen and carbon dioxide.
The most curious thing was that the production was profitable. From 490 to 650 kg of liquid products with a cost price of 71 Reichsmarks were produced from a ton of coal. When distilled into gasoline, kerosene, diesel fuel and lubricating oils, products with a total cost of 141 Reichsmarks were obtained. That is, processing a ton of coal gave 70 Reichsmarks of profit. Erdöl- und Kohleverwertung AG, founded in 1914, which built this plant, survived very difficult times and existed until December 1941, when it was liquidated by decision of the main shareholder - IG Farbenindustrie.
large production
In 1925, Bergius sold his coal hydrogenation patents to Carl Bosch, head of the large chemical company BASF. Soon, on December 9, 1925, this company, together with several other companies, formed a powerful industrial giant - IG Farbenindustrie. Dr. Matthias Peer was appointed research director of this new company, who significantly improved the process inherited from Bergius.
Matthias Peer
Peer's signature on the testimony at the Nuremberg Trials
He divided the hydrogenation process into two parts. The first part was liquid-phase hydrogenation, in which a paste of coal dust and heavy oils reacted with hydrogen at a pressure of 230 atmospheres and a heating of 300 degrees. The result was 10-20% gases, 5-10% solids, 50-55% heavy oils, and 20-30% medium oils (kerosene, diesel fuel, and fuel oil). The second part was vapor-phase hydrogenation, which took medium oils that reacted with hydrogen at a pressure of 200-300 atmospheres and a heating of 400 degrees, using a catalyst. That phase produced 50-70% gasoline and petrol with a boiling point of up to 165 degrees.
The technology provided for the turnover of semi-finished products. Hydrogen was produced from gases, and heavy oils were returned to the stage of preparation of carbon paste. Pir did not try to split long molecules at once. Two or three passes, and the most stubborn molecules would succumb to splitting.
Improved process flow chart
Peer quickly brought the technology to the required perfection, and already in April 1927 the first Leuna-Werke plant was launched on the basis of the existing production of synthetic ammonia. In 1931 it produced 300 thousand tons of fuel per year. Subsequently, already within the framework of the four-year plan and construction during the war, 12 large gasoline plants were built with a total capacity of 4,2 million tons per year. These 12 plants produced 1938 million barrels or 1945 million tons of various fuels from 128 to 17,46.
Location of plants using the Bergius-Pier process in Germany
For example, the Wesseling plant in the town of the same name on the left bank of the Rhine south of Cologne, built in 1941 and producing its maximum output in 1943. Its capacity was 260 thousand tons per year, the plant produced 39,4 thousand tons of motor gasoline, 93,2 thousand tons of aviation gasoline, 72,8 thousand tons of diesel fuel, 21,1 thousand tons of gas, and a thousand tons of phenol. The raw material was brown coal. Hydrogen production reached 47,5 thousand cubic meters from brown coal and 36,5 thousand cubic meters from methane and ethane obtained during the process.
The liquid phase was produced in four reactors of 32 cubic meters each, operating under a pressure of 640 atmospheres and heating to 475 degrees. The paste consisted of heavy oils obtained earlier, 36% finely ground brown coal and 6,25% catalyst. The vapor phase was produced first in five reactors of 64 cubic meters each, and then in five reactors of 40 cubic meters each. These reactors had different catalysts, and thus the most complete and effective course of the hydrogenation reaction was achieved. Per ton of raw material, 620 cubic meters or 55,8 kg of hydrogen were consumed. The final yield of gasoline was approximately 35% of the mass of coal, and gasoline and diesel fuel - 45% by mass of coal.
The Pölitz plant during construction
The plants differed somewhat from each other in their hardware and technology, since they were built by different companies and adapted to different types of raw materials. Two plants processed brown coal, four plants processed brown coal tar, four plants processed hard coal, one processed coal tar pitch, and one more processed tar or oil. In the German economy, the Bergius-Pier process stood between oil refining, hard coal coking, and brown coal low-temperature carbonization (semi-coking), and could use raw materials and semi-finished products from all of these sources to produce high-quality motor fuel.
Reasons for misinformation
This story is curious in that there seems to be a deliberate misrepresentation of the nature of the Bergius-Pier technology. It is claimed that it is some kind of "synthesis", whereas in detail it is clear that it is hydrocracking of a mixture of coal and heavy oil.
Hydrocracking units, similar in their hardware design, technological parameters and products to the Bergius-Peer technology, are now operating at many oil refineries without raising any questions. On the contrary, hydrocracking is considered an important part of oil refining and a way to increase the yield of useful products and the depth of oil refining.
And so it turns out that the Bergius-Pier technology is “expensive-expensive”, while the same technology in physical and chemical sense, hydrocracking, suddenly turns out to be appropriate, profitable, and necessary.
The difference in raw materials is not so great. If, for example, coal tar, brown coal tar or pitch are fed to the hydrocracking unit instead of heavy vacuum gas oil, and if 20-30% of finely ground coal is added to the same heavy vacuum gas oil, the unit will cope with it perfectly. Bergius discovered in his first experiments with coal that not all coal can be hydrogenated. Coal grades in which the carbon content exceeded 85% were not amenable to hydrogenation. The best suited were gas coal (30-40% volatile substances) and brown coal (40-65% volatile substances), which in their characteristics were very close to heavy oil distillates, which are usually used for hydrocracking.
So why was it necessary to make up stories about the Bergius-Pier technology, that it was some kind of “synthesis”, and also terribly expensive? I think for two reasons. Firstly, the “patent robbery” of Germany after the end of World War II, especially since the owner of the patents for the Bergius-Pier process was IG Farbenindustrie, which was convicted for all sorts of things. Secondly, so that continental powers such as the USSR and China, which had more coal than oil in the 1950s and 1960s, would not undertake the development of an industry for hydrocracking all sorts of coal tars in remote areas that were very difficult to access even for strategic bombers. If Baku, the main source of oil in the USSR until the discovery of oil in Western Siberia, was under attack by the American aviation, then if the communists build hydrocracking plants in Siberia, they won't be available. Oil and control over it have always occupied a significant place in the strategic plans of the great powers.
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