BMA procedure

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The BMA process ( B lausäure from M ethane and A mmoniak) is a by Degussa (now Evonik Degussa ) developed process for the production of hydrocyanic acid (HCN), further also called hydrogen cyanide directly from ammonia and methane without oxygen is used . In this process, a catalytic dehydrogenation takes place in the synthesis step.

history

After laboratory tests in a heated tube had yielded yields of 90% based on ammonia and methane, the first approaches to a technical realization were made during the Second World War at the German calcium cyanamide works in Piesteritz . Development continued within Degussa after 1949, but it became apparent that the fundamentals of the process and the means for its technical realization had to be revised.

After extensive tests in the laboratory under the direction of E. Wagner, testing of a gas-fired technical furnace began in 1951. In 1954, the work had progressed so far that a pilot plant with a capacity of 6.5 t / month could be planned and installed. The furnace of this system was developed in cooperation with the companies Heinrich Koppers GmbH and Wistra Ofenbaugesellschaft mbH. Materials, construction elements and the specially developed catalytic converter were thoroughly tested in endurance tests that lasted for 6 months. In the spring of 1956, a plant with a capacity of 100 t / month was planned and built and put into operation in 1957.

Technical realization

Schematic representation of a plant according to the BMA method with the components 1 - cleaning tower for methane processing; 2 - ammonia evaporator; 3 - mixer; 4 - synthesis furnace (reaction: methane + ammonia → hydrogen cyanide + hydrogen); 5 - gas cooler; 6 - tower for cleaning with sulfuric acid; 7 - separation of the product mixture; 8 - distillation column

Degussa AG operates the large-scale production of hydrogen cyanide. The system consists of eight different components. In the first two parts, methane and ammonia are processed. In the cleaning system 1 , methane is cleaned with the aid of a platinum catalyst. Liquid ammonia is evaporated in the evaporator 2 and then mixed with methane gas in a certain ratio in the system part 3 . In order to prevent soot formation in the synthesis furnace, a slight stoichiometric excess of ammonia is usually set. Then the gas mixture in the synthesis furnace 4 is sent at 1,200 ° C. to 1,300 ° C. through thin ceramic tubes coated with a platinum catalyst on their inner wall. The endothermic reaction takes place inside the ceramic tube:


The product mixture consists of approx. 71.8% by volume of hydrogen, 22.9% by volume of hydrogen cyanide and 2.5% by volume of excess ammonia. Smaller amounts of unconsumed methane, carbon monoxide and nitrogen can also be detected. This mixture is first cooled in the gas cooler 5 and then washed with sulfuric acid in tower 6 , whereby the excess ammonia is separated from the products. The following reaction takes place here:


Then the hydrogen cyanide is separated from the hydrogen in 7 , here e.g. B. by absorption of HCN in water. The hydrocyanic acid is separated from the water in the distillation column 8 , whereby hydrogen cyanide gas is produced again and can be collected.
The yield of hydrogen cyanide is 90% based on methane and 80% based on ammonia.

variants

The BMA procedure is only of minor importance from a technical point of view. Plants for this synthesis of hydrogen cyanide are located in Germany, Belgium and the USA (Evonic Degussa) and in Switzerland ( Lonza ). There is also a process in which formamide is split into water and hydrocyanic acid and carried out at BASF . The Andrussow process is mainly used to produce hydrogen cyanide , especially for larger quantities. The Andrussow process differs from the BMA process in that oxygen is fed into the reactor. The heat of reaction for the formation of hydrocyanic acid is generated by the combustion of methane (and partly ammonia) in the reaction mixture itself, so that heat transfer is not necessary. Furthermore, larger amounts of hydrogen cyanide are produced in the synthesis of acrylonitrile in the Sohio process .

literature

Individual evidence

  1. ↑ a b Ulfert Onken, Arno Behr: Chemical Process Studies - Textbook of Technical Chemistry , Volume 3, 1st Edition, Georg Thieme Verlag, Stuttgart 1996, ISBN 3-13-687601-6 , pp. 296-297.
  2. ↑ CT Kautter, W. Leitenberger: Large-scale production of hydrogen cyanide according to Andrussow . In: Chemical engineering . tape 25 , no. December 12 , 1953, p. 697-701 , doi : 10.1002 / cite.330251202 ( PDF ).
  3. ↑ F. Endter: The technical synthesis of hydrogen cyanide from methane and ammonia without the addition of oxygen . In: Chemical engineering . tape 30 , no. 5 , May 1958, p. 305-310 , doi : 10.1002 / cite.330300506 ( PDF ).
  4. ↑ a b F. Endter: The technical synthesis of hydrogen cyanide from methane and ammonia without the addition of oxygen , chemical engineering, no. 30, 1958, pp. 305-310, doi: 10.1002 / cite.330300506 .
  5. ^ A b Wilhelm Keim, Arno Behr, Günter Schmitt: Basics of Industrial Chemistry, 1st edition, Otto Salle Verlag GmbH & Co., Frankfurt am Main, Verlag Sauerländer AG, Aarau 1986, ISBN 3-7935-5490-2 (Salle) , ISBN 3-7941-2553-3 (Sauerländer), pp. 313-314.
  6. ↑ a b Klaus Weissermel , Hans-Jürgen Arpe : Industrial Organic Chemistry, 5th Edition, Wiley-VCH Verlag GmbH, Weinheim 1998, ISBN 3-527-28856-2 , pp. 50-51.