Power-to-Chemicals

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Power-to-Chemicals (German as: electricity to chemicals ) denotes a process in which excess electrical energy from renewable energy via electrolysis of water is used and further downstream steps for the production of chemical raw materials. Power-to-Chemicals is therefore a Power-to-X technology that can be used as part of the energy transition for sector coupling . Power-to-Chemicals is based on the power-to-gas process to which it is closely related. However, the products produced are not used for direct energy storage, but are intended for material use in order to be able to decarbonise the raw material production of the chemical industry in this way .

process

The starting point for the power-to-chemicals process is initially the electrolysis of water, in which water is split into oxygen and hydrogen . The hydrogen obtained in this way is then used in a second step together with carbon dioxide to produce a synthesis gas for a methanol synthesis to form methanol or a Fischer-Tropsch synthesis to form a mixture of gaseous and liquid hydrocarbons , which in turn serve as the starting material for a large number of other processes for producing ethylene , Propylene or other products and subsequent products based on them can be reused. Reacted with nitrogen , the hydrogen can also be used for the synthesis of ammonia and its salts, ammonium carbamate , ammonium carbonate and ammonium hydrogen carbonate , which are mainly used as fertilizers ( power-to-ammonia ).

background

Since the chemical industry both in energy production as well as in the materials converted fossil raw materials mainly to the fossil fuels oil and natural gas is based, must be the chemical industry with the shortage of raw materials and to protect the climate their raw materials are converted to renewable energy and carbon sources increasingly. In addition to biomass, alternatives to fossil chemical raw materials are hydrocarbons produced synthetically from carbon dioxide on the basis of Power-to-X technologies such as B. Power-to-Gas as well as carbons already present in the technosphere in the form of plastic and other products that can be fed into a circular economy through chemical recycling . Since carbon is the basis of organic chemical processes, one cannot speak of decarbonisation (“abandoning carbon”) in this case .

Power-to-gas systems make it possible to use renewable surplus electricity to produce synthetic raw materials based on water and carbon dioxide, from which more complex basic materials such as methane, methanol or polymers can be produced. Indirectly, power-to-chemicals, like power-to-gas, are a storage process for electrical energy, since in this way fossil fuels are substituted and are no longer required as raw material suppliers, but are potentially available for energetic purposes or in the ground can remain. In addition, power-to-chemicals plants can make the energy system and other storage systems more flexible, for example by providing control power or by using it in load management , and thus contribute to sector coupling.

The chemical industry in particular is a possible buyer of the products, but other branches of industry also have a high demand for hydrogen or other synthesis gases in some cases. For example, petroleum refineries , which have a significant hydrogen requirement for the production of fuels , could be supplied with hydrogen from power-to-gas plants, which could significantly reduce the CO 2 emissions from transport . With the use of power-to-chemicals, certain industrial processes can be decarbonised that are currently still supplied with fossil fuels. For example, German industry consumed more than 60 TWh of hydrogen in 2010, which was obtained almost entirely from fossil sources . From the point of view of the energy industry, it therefore makes sense to first meet the hydrogen needs of industry with power-to-chemicals before hydrogen is further processed into methane in the power-to-gas process, otherwise hydrogen from fossil methane / natural gas and artificial methane at the same time would be generated from hydrogen. The production of syngas for the chemical industry also has a higher environmental benefit than the production of methane using power-to-gas technology.

literature

Individual evidence

  1. ↑ Cf. Ulrich Bünger, Jan Michalski, Patrick Schmidt and Werner Weindorf, Hydrogen - Key Element of Power-to-X , in: Johannes Töpler, Jochen Lehmann (Eds.): Hydrogen and fuel cell. Technologies and market prospects . 2nd edition, Berlin - Heidelberg 2017, 327-368, here p. 329.
  2. ↑ Michael Sterner , Ingo Stadler (Ed.): Energy storage. Need, technologies, integration. 2nd Edition. Springer Verlag, Berlin / Heidelberg 2017, p. 169 and p. 190.
  3. ^ A b Michael Carus, Achim Raschka: Renewable Carbon Is Key to a Sustainable and Future-Oriented Chemical Industry. Industrial Biotechnology 14 (6), 2018; S. doi : 10.1089 / ind.2018.29151.mca .
  4. ↑ Michael Sterner , Ingo Stadler (ed.): Energy storage - demand, technologies, integration . Berlin - Heidelberg 2017, p. 677f.
  5. ↑ Michael Sterner , Ingo Stadler (ed.): Energy storage - demand, technologies, integration . Berlin - Heidelberg 2017, p. 31.
  6. ↑ Robert Schlögl : Learning from nature. Chemical reduction of CO 2 . In: Jochem Marotzke , Martin Stratmann (Hrsg.): The future of the climate. New insights, new challenges. A report from the Max Planck Society. Beck, Munich 2015, pp. 167-182, p. 178.
  7. ↑ Cf. Viktor Wesselak , Thomas Schabbach , Thomas Link, Joachim Fischer: Handbuch Regenerative Energietechnik. 3rd updated and expanded edition, Berlin - Heidelberg 2017, p. 763.
  8. ↑ Andre Sternberg, Andre Bardow: Life Cycle Assessment of Power-to-Gas: Syngas vs Methane . In: ACS Sustainable Chemistry & Engineering . tape 4 , no. 8 , 2016, p. 4156-4165 , doi : 10.1021 / acssuschemeng.6b00644 .