Bergius Pier Procedure
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The Bergius Pier process (also known as the Bergius process or IG process ) is a process for liquefying coal through the direct hydrogenation of coal. The macromolecules of the coal are broken down into smaller molecules by hydrogen at high pressures and temperatures. The products are gaseous and liquid hydrocarbons that serve as fuels and lubricants . The German chemists Friedrich Bergius and Matthias Pier developed the process at the beginning of the 20th century.
The IG Farben built in 1927 in Leuna , the first hydrogenation after the Bergius-Pier process, more works followed in other countries. From the mid-1930s, the systems were of particular importance in the German Reich as part of the self-sufficiency efforts . In the post-war period, products based on crude oil predominantly replaced coal-based products in western countries . Bottlenecks in the oil supply during the oil crisis in the 1970s increased interest in the process again. In the Eastern Bloc countries , the hydrogenation plants remained in operation and have been gaining in importance again since the beginning of the 21st century as a result of sharply fluctuating oil prices.
The Nobel Foundation awarded the Nobel Prize for Chemistry in 1931 to Friedrich Bergius together with Carl Bosch “for their services to the discovery and development of the chemical high pressure process”.
history
In 1869, the French chemist Marcelin Berthelot carried out the first experiments to extract liquid hydrocarbons from coal. To do this, he allowed an excess of hydrogen iodide to act on carbon at temperatures of 270 ° C. At this temperature, hydrogen iodide breaks down into the elements and provides the hydrogen for the hydrogenation of carbohydrates. The reaction led to the formation of liquid hydrocarbons, but was of no industrial importance. Berthelot's experiments initiated further research in the field of carbohydrate hydrogenation. In Germany, the Kaiser Wilhelm Society founded the Kaiser Wilhelm Institute for Coal Research for this purpose .
"How nice it would be if liquid fuels could be produced economically from the solid fuel materials through a suitable reduction process!"
With these words the Nobel laureate Emil Fischer described his wish to solve a “fundamental problem of the heating fuel industry” on the occasion of the founding of this institute in 1912, especially in relation to Germany and its lack of liquid fossil fuels . The reduction process desired by Fischer, which could be transferred to chemical engineering, was finally developed by Friedrich Bergius.
Beginnings in Hanover and Essen
As a private lecturer for pure and applied physical chemistry at the Royal Technical University of Hanover , where he had completed his habilitation on the coaling process , Bergius carried out hydrogenation experiments on synthetic coal as early as 1910. Already first tests resulted in reproducible results, which at temperatures of 400 to 450 ° C and a hydrogen pressure of 150 bar in 80% yield gaseous and liquid hydrocarbons supplied. Bergius received a patent for his invention in 1913.
The transfer of the process from the laboratory to a large-scale plant proved difficult and required considerable financial resources. Through contacts with Karl Goldschmidt , Bergius joined the management of the Goldschmidt chemical factory in Essen, which initially financed the process development. In the period after the First World War , however, the financial means for the development of a suitable catalyst were lacking, which subsequently led to the termination of the cooperation.
Founding of IG Farben
The increasing degree of motorization and the beginning conversion of shipping and rail traffic to liquid fuels made the extraction of fuels and lubricants through coal hydrogenation appear as a profitable source of income. In addition, the experts on the Federal Oil Conservation Board expected in 1926 that global oil production would peak as early as 1929 , and that the oil reserves would be depleted alarmingly quickly. In contrast, the rich brown and hard coal deposits seemed to secure the supply of fuel for centuries.
Encouraged by the technical and commercial successes of high-pressure chemistry in the Haber-Bosch process , methanol production and isobutyl oil synthesis , Carl Bosch therefore directed BASF's research activities towards the high-pressure hydrogenation of lignite. In July 1925, BASF acquired part of the German Bergius patents and a year later most of the international rights from Royal Dutch Shell . BASF assigned the process development to Matthias Pier, a Nernst student who had already developed the high-pressure process for the production of methanol . In the ammonia and methanol apparatus, he carried out experiments on the catalytic hydrogenation of lignite tar with sulfur-containing catalysts such as iron and molybdenum sulfide . Carl Krauch , who later became head of the Reich Office for Economic Development , sponsored Piers' work.
The hydrogenation of coal in a suspension posed a challenge compared to the pure gas phase reactions and required considerable investments in process development. A high concentration of typical catalyst poisons required a high stability and selectivity of the catalyst in order to lead the reactions to the desired products with a very inhomogeneous raw material. In addition, there were technical difficulties such as the attack of hydrogen and hydrogen sulfide on the reactor material as well as problems with the separation of residual coal, ash and catalyst from the liquefied products.
Carl Bosch recognized that the acquisition of the capital required to transfer the process to chemical engineering required a broad financial basis, which ultimately led to the founding of IG Farben in 1925 . Because of its proximity to the central German lignite mining district and the experience it had in high-pressure technology, Bosch chose Leunawerke as its first production facility in 1927. Within five years, BASF overcame the technical difficulties and increased fuel emissions to around 100,000 tons per year. Compared to the products of indirect coal hydrogenation through the Fischer-Tropsch synthesis , the synthetic gasoline produced according to the Bergius-Pier process had a higher octane number .
IG Farben invested around 426 million Reichsmarks in the process up to 1931 , more than double the turnover of the BASF part of IG Farben that year. The Standard Oil of New Jersey acquired at this time the worldwide distribution rights for the procedure. The company Imperial Chemical Industries (ICI), Shell, Standard Oil and IG Farben founded in 1931, the International Hydrogenation Patents Company , to pool the resources and the know-how for the production of synthetic gasoline and the publication of discoveries limit.
The economic problems were greater than the technical ones. The production costs of Leuna petrol turned out to be partly higher than those for petrol production on the basis of crude oil. At times the price of petrol made from crude oil was below the price of the coal used. In addition, the pessimistic prognosis regarding recoverable oil reserves turned out to be wrong. The onset of the global economic crisis increased the net losses of IG Farben, which could not be compensated by the payment of license fees from Standard Oil of New Jersey.
time of the nationalsocialism
In 1933 representatives of IG Farben made contact with the National Socialist leadership in order to gain political support for the process. The Reich Ministry of Finance then granted protective tariffs in order to keep the synthetic gasoline competitive. In December 1933, the Feder-Bosch Agreement negotiated by the NSDAP's economic policy spokesman Gottfried Feder and Carl Bosch was signed , whereby IG Farben undertook to supply synthetic gasoline at a guaranteed price.
In 1936, in the memorandum he had written on the four-year plan , Hitler ordered the implementation of a four-year plan , including the aim of maximizing the expansion of facilities for the production of synthetic gasoline. Brown coal-gasoline AG (Brabag), with its four hydrogenation plants in Magdeburg , Böhlen , Schwarzheide and Zeitz , was to play a key role . A total of nine plants were built in the German Reich after the Fischer-Tropsch synthesis of Ruhrchemie and 14 after the high-pressure hydrogenation process of IG Farben.
The largest plants with a production capacity of more than 600,000 t / a (tons of fuel per year) operated in Pölitz, Leuna and Brüx. The 14 Bergius Pier hydrogenation plants together had a planned capacity of 3,866,000 t / a and the nine Fischer-Tropsch plants of 647,000 t / a. The planned annual capacity was not reached at all plants until 1943/44.
| Production data of hydrogenation plants according to the Bergius Pier method (selection) | ||||
|---|---|---|---|---|
|
Start of production |
Location | operator | Feedstock |
Production capacity 1943/44 in tons per year |
| 1927 | Leuna | IG colors | Brown coal | 650,000 |
| 1936 | Bohlen | BRABAG | Lignite tar | 250,000 |
| 1936 | Magdeburg | BRABAG | Lignite tar | 220,000 |
| 1936 | Scholven - Buer | Hibernia AG | Hard coal | 280,000 |
| 1937 | Bottrop- Welheim | Ruhröl GmbH | bad luck | 130,000 |
| 1939 | Gelsenberg | Gelsenkirchen-Petrol AG | Hard coal | 400,000 |
| 1939 | Tröglitz / Zeitz | BRABAG | Lignite tar | 280,000 |
| 1940 | Lützkendorf | Central German fuel and oil works AG | Tar, oil | 50,000 |
| 1940 | Poelitz | Hydrierwerke Pölitz AG | Coal, oil | 700,000 |
| 1941 | Wesseling | Union Rheinische Braunkohlen fuel AG | Brown coal | 260,000 |
| 1943 | Brus | North Bohemian Coal Works AG | Lignite tar | 600,000 |
| 1943 | Tin hammer | Oberschlesische Hydrierwerke AG | Coal, tar | 420,000 |
| until 1944 | Bergius Pier as a whole | 4,230,000 | ||
The maximum output of around 4.5 million tons, which was achieved together with the Fischer-Tropsch plants in the period from 1943 to the beginning of May 1944, cannot be equated with the annual production of synthetically produced aviation fuel , which various authors stated in the post-war period. The largest share of the IG process was made up of aviation fuels, but this was followed by gasoline and diesel fuel , heating oil, lubricating oil and other products (secondary products). At that time, neither jet fuel nor heating oil was produced with the Fischer-Tropsch synthesis, so that the proportion of fuel produced by this process was lower than with the IG process. Both processes could be used to produce gasoline and diesel oil, with the quality of the products being differentiated by different octane numbers and cetane numbers . Specifically, the production of all 21 hydrogenation plants in 1943 was 3 million tons of gasoline (vehicle and aviation fuel combined), 770,000 tons of lubricating oil and 430,000 tons of diesel fuel.
Second World War
Although the supply of fuel and lubricants was one of the most vulnerable parts of the war machine, a direct attack on the hydrogenation works did not take place until 1944. After the success of Operation Tidal Wave in the air raids on Ploiesti and the refineries and oil reserves there, the leadership of the allies declared Luftwaffe made the German hydrogenation plants a strategic target. On the evening of May 12, 1944, 935 bombers of the United States Army Air Forces launched a major attack on the Leuna, Böhlen, Tröglitz, Lützkendorf and Brüx hydrogenation plants. The destruction caused by these air raids temporarily shut down the five hydrogenation plants.
Up until May 29, 1944, the US bomber forces flew concentrated attacks against all 27 refinery and hydrogenation plants in the German sphere of influence. After that, the works were substantial, mostly completely destroyed. This threatened the complete collapse of the German fuel supply. Against this background, Adolf Hitler immediately and personally ordered “immediate measures to restart and protect the hydrogenation works” on May 30, 1944. With the mineral oil security plan , which was kept secret, an attempt was made within a very short time to rebuild the works and to transform the facilities into "hydrogenation fortresses" through the use of massive flak .
The repairs were only temporary as a result of ongoing air raids by the Allies. From September 1944 onwards, all German hydrogenation plants of the Wehrmacht could only deliver 11,000 tons of gasoline per month. The project initiated by Armaments Minister Albert Speer to relocate hydrogenation plants underground in tunnels with the help of thousands of skilled workers, forced laborers and prisoners was also unsuccessful. The completion did not succeed before the end of the war. Ultimately, the destruction of the German hydrogenation plants contributed to the German war machinery coming to a standstill.
Other countries
The possibilities of converting fossil fuels into liquid fuels and lubricants promoted other countries, in particular Great Britain and the USA, at least in the beginning in a comparable manner. The decisive factor was a thesis published by US scientists in 1925 and taken seriously worldwide, according to which global oil supplies would be exhausted in seven years, while motorization would increase inexorably. A year later, the United States Congress formed a committee to look for alternatives.
As a result, similar to IG Farben in Germany, Imperial Chemical Industries (ICI) in Great Britain and DuPont in the USA acquired economic and political importance. For the production of synthetic gasoline, two hydrogenation plants were built in Baton Rouge (Louisiana) and one in Baytown (Texas) in the USA from 1927 in cooperation with IG Farben . The largest hard coal hydrogenation plant in the world at the time went into operation in Billingham in north-east England in 1935 . During the opening ceremony, British Prime Minister Ramsay MacDonald stressed that building hydrogenation plants was "in the interests of national security". The planning for the plant began in 1931 and, according to official British information, was oriented towards a future war in order to be able to fall back on indigenous oil resources in the event of a sea blockade. The technical know-how was provided by IG Farben, which in February 1932 made an "Engineer Agreement" with ICI.
The British government subsidized both the construction of the plant and the fuel produced until October 1939. The Billingham plant had a capacity of 150,000 t / a (tons of fuel per year) and was not shut down until 1963. Under the strictest secrecy of the British government, construction began on another plant in Heysham in autumn 1939 , which went into operation in July 1941. The cost of construction was 10 million pounds sterling , at that time around 110 million Reichsmarks , and was borne entirely by the Air Ministry . The plant had an annual capacity of 1,500,000 tons, including 344,000 tons of aviation fuel and 55,000 tons of isooctane . Together, the two plants in Billingham and Heysham hydrogenated synthetic explosives and, from 1942, 500,000 tons of aviation fuel with an octane rating of 100 per year . The plant in Heysham was completely dismantled in 1946 and, according to the UN, it was able to process 4500 tons of crude oil per day (1,600. 000 t / a) for petrol, gas and heating oil in the Middle East ( Abadan ).
On the basis of a law of May 11, 1936, the Ministero delle Finanze issued , among other things, income tax , sales tax and share capital levy for companies that processed Italian coal through hydrogenation into synthetic products . In the same year Italy began building Bergius Pier hydrogenation plants in Bari and Livorno . Both plants went into operation in 1938 with an annual output of 180,000 tons each and worked in combination with existing petroleum refineries. In the period that followed, the facilities were expanded and, starting in 1940, supplied 450,000 tons of liquid oil products annually.
The operator of the hydrogenation works was the Azienda Nazionale Idrogenazione Combustibili (ANIC), a merger of Montecatini , Azienda Italiana Petroli Albanesi (AIPA) and Agip (now Eni ). During the heavy British and American day and night bombing of Livorno from May 19 to June 7, 1944, the center of the city and all surrounding industrial areas were completely destroyed. After the conquest of northern Italy, the Allied military government had the remains of the hydrogenation plant dismantled. From 1947, the ANIC had concrete plans to rebuild the plant, but these were not used in favor of a refinery . In contrast, the hydrogenation plant in Bari remained in operation until 1974 and was not finally closed until 1976.
Spain founded the national company Empresa Nacional Calvo Sotelo (today Repsol ) in 1942 and concluded an agreement with Germany in 1944 to set up a hydrogenation plant based on the IG process in Puertollano . In 1950 the Spanish government signed new contracts with BASF . The production of synthetic gasoline began here in 1956 and ended in 1966. This was followed by the switch to other chemical products, which are still hydrogenated in various Repsol plants today.
On April 5, 1944, the US government, under the auspices of the United States Bureau of Mines, passed the Synthetic Liquid Fuels Program by law and approved $ 30 million for the next five years (this would correspond to a purchasing power of $ 433,160,345 today). The aim of the program was "to support the construction and operation of hydrogenation plants for the production of synthetic liquid fuels from coal, oil shale, agricultural and forestry products and other materials for warfare, and to preserve and increase the nation's oil resources" .
Between 1945 and 1951, two special research facilities were built near Pittsburgh and Louisiana, Missouri . In 1949, the Louisiana plant produced 200 barrels of oil per day using the Bergius process. In 1953 the new Republican Budget Committee stopped funding the research. However, the Louisiana facility remained operational under the direction of the United States Department of the Army . In the years that followed, research was carried out on various hydrogenation processes in the USA under the name CtL by Kellog and in South Africa by Sasol , with the Fischer-Tropsch synthesis developing in particular.
In the wake of the oil price shock , the US government resumed research and development of synthetic plants from 1973. In 1979, after the second oil crisis , the US Congress approved the Energy Security Act to create Synthetic Fuels Corporation and approved approximately $ 88 million for synthetic fuel projects. Fully funded by the US government, the company focused on the development and construction of commercial hydrogenation plants. In addition to the Bergius-Pier process, the Lurgi-Ruhrchemie process was particularly important. After the 1985 oil glut, Synthetic Fuels Corporation was dissolved by the Reagan administration . By then, based on today's purchasing power, a total of $ 8 billion in public funds will have been used for the production of synthetic fuels in the USA .
Post-war Germany
After the end of the Second World War, the Allies initially ordered the shutdown of the hydrogenation plants in Germany. The Soviet Army had the Magdeburg, Rodleben and Pölitz hydrogenation works dismantled and rebuilt in Dzerzhinsk near Gorky . In Operation Ossawakim , the Soviet Union deported many of the engineers and scientists who had been working in the hydrogenation plants there. Likewise, as part of Operation Paperclip , the US government had German engineers and chemists, above all from Brabag , IG Farben and the Kaiser Wilhelm Institute for Coal Research , spend most of the time in Louisiana (Missouri) for the Synthetic Liquid Fuels Program .
When the hydrogenation ban was lifted at the beginning of the 1950s, the petroleum-based products were so inexpensive that restarting them in West Germany was not profitable. In the German Democratic Republic , however, the hydrogenation of lignite celberation was resumed and the products for foreign exchange procurement were sold in western countries. The last lignite hydrogenation plants were shut down in Zeitz in 1990.
Under the impression of the oil crisis , Helmut Schmidt announced in a government statement from July 1979 that the federal government wanted to subsidize the technology of carbohydrate hydrogenation. Veba and Ruhrkohle AG then built a test facility in Bottrop in 1981 for the hydrogenation of 200 tons of coal per day, which was shut down in 1993.
Applications in the present
Due to the low price of oil, no new coal hydrogenation projects were pursued in Europe, Japan, Russia and the United States until the late 1990s. According to information provided by RAG Aktiengesellschaft at the time, the process is only worthwhile when the price of petrol is 2.30 DM.
As a result of strongly fluctuating oil prices, hydrogenation plants using various technologies have been gaining in importance worldwide since the beginning of the 21st century. According to analysts, the threshold for economic viability is exceeded at an oil price of 60 US dollars per barrel.
In 2003, Shenhua Coal Liquefaction and Chemical Co. built a hydrogenation plant in Ejinhoro-Banner with an investment volume of over two billion dollars , which began testing operations in 2009. The local coal reserves in the Ordos area are estimated to be 160 billion tons of coal. For 2013, Shenhua reported a hydrogenation plant output of 866,000 tons of oil products.
raw materials
hydrogen
The hydrogen was generated via coal gasification with the help of a Winkler generator in a fluidized bed . In a series of exothermic and endothermic reactions , finely ground coal reacts with oxygen and water to form carbon dioxide and hydrogen. The use of pure oxygen versus air prevents the undesired lowering of the hydrogen partial pressure by atmospheric nitrogen during the subsequent hydrogenation. The oxygen production of the air separation plants operated at that time served almost exclusively this purpose. The fine division of the coal ensured good heat transfer, and the temperature inside the generator was more or less constant. The driving style did not produce any tar, and the gas obtained was free of hydrocarbons. Since the operating temperature of the fluidized bed gasifier had to be kept below the melting point of the ash, the Winkler generator was particularly suitable for the gasification of reactive types of coal.
The combustion of coal with oxygen to carbon monoxide (reaction 1) provided the energy for the endothermic generation of water gas (reaction 2). Carbon monoxide reacts in a reversible reaction to form carbon and carbon dioxide (reaction 3). The equilibrium between the reactants , which is established depending on the temperature and pressure, is called the Boudouard equilibrium after the French chemist Octave Leopold Boudouard . The resulting carbon is available for combustion again. Carbon monoxide can also react with water in a reversible reaction, the so-called water-gas shift reaction , to form carbon dioxide and hydrogen (reaction 4).
A pressure adsorption stage removes the resulting carbon dioxide from the gas mixture. After this step, pure hydrogen is available for the hydrogenation.
Brown coal
Lignite is a fossil fuel with a carbon content of around 58 to 73%. As a rule, it is geologically younger than hard coal and has a lower degree of coalification. The water content of raw lignite is 15 to 60%, depending on its origin, the content of inorganic ash components is between 3 and 20%. Compared to hard coal, lignite has a higher oxygen content, which is caused by humic acids . The high content of volatile components in lignite simplifies the conversion into liquid products by hydrogenation.
Lignite tar
Lignite tar results from the smoldering of lignite. The tar consists mainly of aliphatic hydrocarbons. When using lignite tar, a previous distillation is necessary, which separates more volatile components with a boiling point of up to 325 ° C. The distillate is hydrogenated in the gas phase hydrogenation, while the residue is hydrogenated in the bottom phase.
|
Content of hetero elements and hydrogen as well as the hydrogen requirement of various raw materials in the hydrogenation |
|||
|---|---|---|---|
| raw material |
Content of hetero elements per 100 g of carbon |
Hydrogen content per 100 g of carbon |
Hydrogen requirement in liters per kilogram of gasoline |
| Edible charcoal | 5.8 | 4.8 | 1210 |
| Gas flame coal | 12.6 | 6.5 | 1145 |
| Smoldering tar (gas flame coal) |
14.1 | 10.3 | 670 |
| Brown coal | 39.2 | 7.6 | 1350 |
| Brown coal tar | 9.7 | 12.2 | 1030 |
| oil | 1.9 | 14.7 | 246 |
Hard coal
Of the hard coals, gas flame coal was preferred , which by hydrogenation yielded up to 73% liquid hydrocarbons. In relation to anhydrous and ash-free coal, gas flame coal consists of about 80% carbon, 5% hydrogen, 12% oxygen, 1.5% nitrogen and 1.5% sulfur. The proportion of volatile components is 40%. At 10%, the water content is well below that of lignite. The preparation of the coal is made easier and the energy requirement compared to lignite is correspondingly lower. The ash content is also significantly lower than that of lignite.
Black coal tar
Coal tar or low-temperature tar is formed when coal is carbonized at temperatures below 700 ° C. Coal types with a high proportion of volatile substances, such as gas flame coal, were preferably used. The coal was finely chopped and added to a smoldering furnace from above. Smoldering coke was discharged as a solid product at the bottom of the smoldering furnace. The volatile constituents were drawn off at the smoldering furnace head and some of them were circulated as flushing gas. The purge gas was heated by combustion gases. Most of the volatile components were drawn off and liquefied in de-tarring systems and separated from the gasoline in an oil washer. The production volume in 1944 was around 200,000 tonnes of black coal tar.
catalyst
The process originally developed by Bergius did not use any special catalysts, but used the catalytic properties of the inorganic components of coal ash. The ash consisted of oxides, sulphates , silicates and phosphates of various elements, mostly iron and aluminum, as well as alkali and alkaline earth compounds . The coal sales achieved with this method were mostly unsatisfactory.
Catalysts for the sump phase hydrogenation
The development of a suitable catalyst proved to be difficult due to the large number of raw materials used, the fluctuations in the composition of the respective raw material and the high content of hetero elements. As a catalyst for the swamp phase hydrogenation, Matthias Pier initially used Bayermasse , sometimes in conjunction with goethite . This catalyst was insensitive to the sulfur impurities contained in the lignite and the hydrogen sulfide formed during the hydrogenation. Bayermass was produced in large quantities as an inexpensive by-product in the production of aluminum oxide from bauxite in the Bayer process . In addition to iron oxides, Bayer mass contains larger quantities of titanium oxide , aluminum oxide and silicon dioxide , as well as oxides or hydroxides of sodium, calcium, chromium, magnesium, copper and other metals. The coal sales generated with Bayer mass were in the range of about 50% and thus still too low for large-scale application. In addition, the reactors coked heavily, so that they had to be mechanically freed from unconverted coke.
A catalyst developed by Pier based on molybdenum oxide (MoO 3 ), zinc oxide and magnesium oxide , which was added to the sump phase as a powder, increased sales significantly. However, the need for expensive molybdenum oxide, some of which was recovered, significantly increased the cost of the process. In addition, the specific heavier catalyst phase partly settled on the bottom of the reactor and thus only took part in the catalytic conversion to a limited extent. In the search for cheaper alternatives, dust impregnated with iron sulfate and caustic soda from the cyclones of the Winkler generator turned out to be highly active. The dust consisted of about 65% carbon and was used as oil mash. In relation to the coal used, a catalyst content of around 10% was necessary to achieve a coal conversion of around 90%. The effect of the fine distribution of the catalyst by the Winkler dust played an important role in increasing the catalytic activity. This intensified the contact between the carbon and the catalyst. The catalyst also remained in the coal-oil phase and did not settle out. This variant of the catalyst developed by Pier in 1928 was used until the process was discontinued in 1959.
Gas phase hydrogenation catalysts
As one of the first catalysts for the pre-hydrogenation to convert the hetero compounds, Pier used the catalyst based on molybdenum oxide, zinc oxide and magnesium oxide, which was successfully tested in the sump phase. The remaining nitrogen compounds and the resulting ammonia quickly deactivated the contact used in the form of cubes.
Only contact on the basis of tungsten sulfide showed sufficient long-term activity for the pre-hydrogenation. The contact, which was precipitated from ammonium paratungstate and sulphurised with hydrogen sulphide, disintegrated during the subsequent thermal decomposition to form a stoichiometric tungsten sulphide of the form WS 2.15 . However, the hydrogenation activity of the contact was found to be very high. Contact hydrogenated benzene to cyclohexane and thus lowered the octane number of the products. The search for cheaper and less active contacts led to the use of contacts based on nickel sulfide in combination with tungsten sulfide or molybdenum sulfide on aluminum oxide. This type of catalyst corresponds to the hydrodesulfurization catalysts that were later used in petroleum refineries .
For the second stage of the gas phase hydrogenation, gasification, contacts were desired which had good hydrocracking and isomerization activity. From studies on the isomerization of paraffins, the suitability of acid-treated aluminosilicates as a catalyst for this reaction was known. Finally, a tungsten sulfide on hydrogen fluoride-activated fuller's earth contact was used as a catalyst for the gasoline process.
Reaction engineering
The Bergius-Pier process can be subdivided into the sub-steps of coal pulp production, sump phase hydrogenation and gas phase hydrogenation. The gas phase hydrogenation consisted of prehydrogenation and gasolineation. The products were worked up by distillation. To remove hydrogen sulfide and carbon dioxide, the gas phase was subjected to an alkazide scrubbing. Potassium N , N -dimethylglycinate, the potassium salt of dimethylglycine , formed an adduct with hydrogen sulfide or carbon dioxide at room temperature, which was broken down again into the starting products at temperatures above 100 ° C.
Coal pulp production
First, the brown coal was ground in a hammer mill to a grain size of five millimeters and then dried to a water content of 4%. Before drying , Bayer mass was added to the brown coal and an iron content of around 2.5% was set. After drying, it was re-ground to a grain size of one millimeter.
After adding about 15% grinding oil, the brown coal was processed into coal pulp in a pulp mill. Working under nitrogen as a protective gas minimized the oxidation of the lignite. In the next step, the mass was pumped to a heat exchanger, the regenerator, by means of a pulp press, with a solids content of 48% being set with further grinding oil. The coal pulp typically had an ash content of about 20%.
Bottom phase hydrogenation
The coal pulp, known as sump due to its high solids content, was hydrogenated in an exothermic reaction at temperatures of 450 to 500 ° C and hydrogen pressures of 200 to 700 bar. During this process, the heteroatoms of the organosulfur , organonitrogen and organo-oxygen compounds contained in the coal were almost completely converted into their volatile hydrogen compounds . Furthermore, the splitting and saturation of the hydrocarbons took place here.
First, a pulp press conveyed the coal pulp through two heat exchangers , called regenerators, and a preheater to the high-pressure furnace. In the regenerators, the coal rice was preheated with hot products from the hydrogenation. The preheater was used for heating with gas up to the reaction temperature of 450 to 500 ° C.
The processing of one cubic meter of coal pulp per hour required roughly the same reactor volume. A typical reactor, the high pressure furnace, had a diameter of about one meter, a height of 12 to 18 meters and a volume of about nine cubic meters. With a processing capacity of 250 cubic meters of coal pulp per hour, the hydrogenation consumed around 86,000 standard cubic meters of hydrogen. For this purpose, 360,000 standard cubic meters of hydrogen were circulated, partly to mix the coal pulp, partly with the addition of cold hydrogen, which absorbed the heat of hydrogenation. Methane and ethane as well as nitrogen, carbon monoxide and carbon dioxide accumulated in the circulating hydrogen. In order to minimize a reduction in the hydrogen partial pressure caused by these gases, the circulated gas was subjected to an oil wash at 250 bar before it entered the reactor. The hydrocarbons dissolved in the middle oil that came from the hydrogenation.
The middle oil was depressurized in two stages. In the first pressure release stage of 25 bar, the low molecular weight gases such as hydrogen, methane, carbon monoxide and carbon dioxide were released. In the second expansion stage at normal pressure, the liquid gases and some pentane were released.
The chemical structure of the products of the sump phase hydrogenation was still similar to the carbons used. Hard coal oils contained many aromatic compounds , while oils obtained from lignite mainly contained aliphatic hydrocarbons . The resulting oils were separated from non-hydrogenatable components of the coal by distillation. The catalyst remained in the non-hydrogenatable components. These non-distillable solids, which were rich in ash and catalyst components, could be reused in coal gasification to produce hydrogen.
Gas phase hydrogenation
The gas phase hydrogenation is divided into a pre-hydrogenation and what is known as gasolineation. In the pre-hydrogenation stage, the heteroelements not yet eliminated in the bottom phase are removed. The pre-hydrogenation became necessary because the acidic catalysts used in the gasoline process were very sensitive to poisoning by ammonia or other basic nitrogen compounds. In the pre-hydrogenation, the so-called A-middle oil, which had a high nitrogen content, was hydrorefined without cleavage. After the gasoline fraction had been separated off, the so-called, almost nitrogen-free B-middle oil was produced, which was subjected to a hydrocracking reaction in the gasoline process.
The target products, hetero-element-free hydrocarbons with the required boiling range as well as the correct viscosity and octane number, were created in the gasification stage. The gas phase hydrogenation consumed about 25% of the total hydrogen. Isomerization reactions took place without the need for hydrogen and the dehydrogenation of naphthenes to aromatics with the release of hydrogen.
Operating data of the Wesseling hydrogenation plant
The Wesseling plant had a nominal capacity of 260,000 tons per year. The plant reached its highest emissions in 1943, when the output was 39,400 tons of car gasoline, 93,200 tons of aviation fuel, 72,800 tons of diesel fuel and 21,100 tons of propellant gases. The plant also produced 1,000 tons of phenol.
Lignite served as the raw material. Hydrogen was produced partly from lignite, with 47,500 standard cubic meters being produced per hour, and partly from methane and other light hydrocarbons, with which 36,500 standard cubic meters of hydrogen were produced per hour. The conversion took place by means of iron oxide / chromium oxide contacts with subsequent carbon monoxide and carbon dioxide washing.
The sump phase hydrogenation took place in four reactor chambers with a total volume of 32 cubic meters, which were operated at a temperature of 475 ° C. and 650 bar, the hydrogen partial pressure being 475 bar. The lignite was pressed into the reactors as a pulp of 36% lignite with 6.25% catalyst in grind oil . After the phenols had been removed, about two thirds of the middle oil formed there consisted of aromatics, the remainder being made up of olefins, naphthenes and paraffins.
The pre-hydrogenation was carried out in eight reactors with a total volume of 64 cubic meters. Three reactors were equipped with tungsten sulfide contacts and five reactors with a nickel sulfide / molybdenum sulfide / tungsten sulfide on aluminum oxide contacts. The gasification took place in five reactors with a total volume of 40 cubic meters, in which hydrogen fluoride- activated tungsten sulfide on fuller's earth contact was used. The pre-hydrogenation and gasoline stages required a total of 620 standard cubic meters of hydrogen per ton of raw material throughput.
Products
The range of products depended on the chemical composition of the coal used, such as the degree of coalification or the ash content, as well as the reaction conditions such as hydrogen pressure, temperature and residence time . Lignite mainly supplies paraffinic products that are used as diesel fuel , while hard coal supplies higher-octane, aromatic products for use as motor gasoline .
Gases
Methane , ethane , propane and a mixture of n- butane and isobutane were obtained as gaseous products . The production of 100,000 tons of gasoline from lignite produced around 23,000 tons of liquefied gases, 10,000 tons of which were propane and 13,000 tons of a mixture of n - and isobutane. In winter about 5000 tons of butane remained in the gasoline, 8000 tons were available for the chemical industry. In addition, about 6,500 tons of ethane were produced. The gaseous hydrocarbons were formed by cracking reactions , with alkenes initially formed, which are immediately further hydrogenated to the corresponding alkanes .
The resulting gaseous hydrocarbons were divided into lean and rich gases. In addition to hydrogen, the lean gases mainly contained methane and part of the ethane, the rich gases mainly contained liquid gases and hardly any hydrogen. The gases were obtained mainly through the expansion of washing oils, during the distillation of the products and during the gasoline process.
petrol
Regardless of the raw material and the process parameters, the Bergius Pier process produced a paraffin and naphthenic gasoline with an engine octane number of 71 to 73. The olefin content was below 1%, the aromatic content was between 8 and 9% depending on the raw material. With the same raw materials and process parameters, tungsten sulphide / nickel sulphide on alumina contacts in the pre-hydrogenation and tungsten sulphide on alumina contacts in the gasoline stage produced the gasoline with the highest octane ratings. An aromatization stage with chromium oxide / vanadium pentoxide on activated carbon contacts increased the octane number to about 83.
| Typical analysis values of aviation fuel from various hydrogenation plants | ||||
|---|---|---|---|---|
| parameter |
Leuna (brown coal) |
Scholven (coal) |
Gelsenberg (hard coal) |
Pölitz (hard coal) |
| Density in g / cm³ | 0.719 | 0.738 | 0.740 | 0.730 |
| Start of boiling in ° C | 45 | 44 | 46 | 44 |
| End of boiling in ° C | 139 | 156 | 151 | 152 |
| % Paraffins | 51.5 | 37.5 | 36.5 | 48.5 |
| % Naphthenes | 38 | 53 | 54 | 43 |
| % Aromatics | 8.5 | 8.5 | 9 | 7.5 |
| % Olefins | 1 | 1 | 0.5 | 1 |
| MOZ | 71 | 73 | 73 | 72 |
Diesel fuel
The diesel fuels produced from lignite had a higher cetane number than those from hard coal , diesel fuels from systems with a higher process pressure were richer in paraffin and therefore more ignitable.
The density of the diesel was between 0.8 and 0.88 g / cm³. The cetane number was between 45 and 55 for diesels that were hydrogenated at pressures of 200 to 300 bar, and between 72 and 75 for diesels that were produced at high pressures of 600 bar. The hydrogen content was around 14%.
mechanism
Studies of model substances such as thiophene , phenol or pyridine in hydrofining reactions suggested that the catalytically active sites of the contacts are on the corners and edges of the catalyst crystallites. The reaction of hydrogen with surface-bound sulphide sulfur with the release of hydrogen sulphide creates a coordinatively unsaturated surface site at which heteroatom-containing substrates can bind. The catalytic cycle begins again with the formation of a new sulphide sulfur and an unsaturated organic residue.
In the Bergius Pier process, hydrogenation, hydrocracking and hydrorefining reactions such as hydrodenitrogenation and hydrodesulfurization run in parallel . The hydrofining reactions proceed according to the following reaction scheme:
The hydrogenation converts unsaturated hydrocarbons into richer hydrocarbons, hydrocracking reactions reduce the molar mass and lead to more easily liquid products. The hydrofining reactions eliminate the heteroatoms oxygen, nitrogen and sulfur in the product and generate water, ammonia and hydrogen sulfide. Cracking reactions generate low molecular weight alkenes, which are immediately hydrogenated to alkanes due to the high hydrogen pressure. Furthermore, they release carbon monoxide and carbon dioxide by breaking down ester or other oxygen-containing functional groups of the lignin structure of lignite. The entirety of the processes taking place was at times referred to as Berginizing coal.
Examples of different hydrogenation and hydrotreating reactions are shown in the following reaction scheme on a lignite fragment:
Process variants
The original Bergius process worked without specially added catalysts, but used the iron compounds found in coal ash as catalysts. Bergius came up with the idea of grinding brown coal with oil to form a coal pulp and hydrogenating it under high hydrogen pressure and temperatures of around 500 ° C. The process variants differ in the conduct of the reaction, the catalyst and the hydrogen source.
Pott Broche Trial
At the beginning of the 1930s Alfred Pott and Hans Broche developed a process in which tetralin and decalin are used as hydrogen-releasing solvents. Tetralin and decalin are oxidized to naphthalene , which can be separated off by distillation and reused after hydrogenation. Cresol or phenol are used as additional solvents .
The hydrogenation was carried out at temperatures between 415 and 435 ° C. and a pressure of about 100 bar. A Ruhröl plant produced 30,000 tons of coal oil between 1938 and 1944, which was used as a replacement for heavy heating oil in power plants.
H-coal process
In the H-Coal process developed by Hydrocarbon Research Inc. (HRI) in 1963, lignite is hydrogenated in a one-step process using a cobalt - molybdenum catalyst. To avoid deactivation, the catalyst is kept in constant motion in an "ebullated bed" (flowing bed = fluidized bed reactor ) , some of it is discharged and replaced by fresh catalyst. The various cracking and hydrogenation reactions take place in just one reactor with short reaction times, and the products have a high hydrogen-to-carbon ratio.
With financial support of $ 300 million from the United States Department of Energy , the State of Kentucky, and various oil companies, HRI built a pilot facility for a coal throughput of 200 to 600 tons per day.
Synthoil process
The Synthoil process was developed from 1969 onwards on behalf of the Energy Research and Development Administration / Fossil Energy (ERDA / FE), now part of the United States Department of Energy. The coal was mashed with a solvent. A cobalt-molybdenum catalyst was used as the catalyst, which worked at a temperature of 425 to 450 ° C. and a pressure of up to 280 bar. The target products were liquid fuels for use in power plants. Due to unsolved problems with the long-term activity of the catalyst, the process has so far only been tested on a pilot plant scale.
Shenhua Direct Coal Liquefaction Process
In the Shenhua Direct Coal Liquefaction Process , bituminous coal with a high content of inert components is hydrogenated. The plant, built in Inner Mongolia, is the only commercially operated carbohydrate plant in the world after World War II. The process essentially consists of two back-mixed reactor stages and a fixed-bed hydrotreater . A finely ground iron catalyst is used as the catalyst. The process works at a pressure of 170 bar and a temperature of around 450 ° C., with a conversion of over 90% on the coal used. The products obtained, such as naphtha , diesel oil and liquid gas, are largely free of sulfur and nitrogen.
literature
- Walter Krönig: The catalytic pressure hydrogenation of coals, tars and mineral oils (The IG process by Matthias Pier) . Springer Verlag, 1950. (Reprint: 2013, ISBN 978-3-642-50105-0 )
Web links
Individual evidence
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