Storage and Cross-linked Infrastructures (SCI)
IMVT contributes to the Helmholtz Program “Storage and Cross-linked Infrastructures”, specifically to its topic “Synthetic Hydrocarbons”.
Background of the topic “Synthetic Hydrocarbons”
Today road traffic, air traffic and marine traffic all rely on liquid hydrocarbon fuels, which are mainly of fossil origin. The abundance, low cost, easy handling and high energy content per volume and weight of liquid hydrocarbons have been key factors responsible for the all-time success of gasoline, diesel and kerosene as energy carriers. This has created not only an extensive infrastructure for production and distribution of these fuels but also a fleet of more than 1 billion cars, trucks and buses, 320,000 general aviation aircraft and 260,000 registered ships in operation worldwide, not to mention the traffic facilities they use. For a future energy system based on renewable energies, in a long-term perspective, access to liquid hydrocarbon fuels from renewable primary energy sources such as wind and solar or biomass that would allow for continued use of this enormous investment is highly desirable. This is all the more so as some transport sectors such as air traffic and heavy load traffic depend on fuels with high energy content due to the required cruising range. Being essentially free of Sulphur and other noxious matter, synthetic hydrocarbons thereby clearly outperform their fossil counterparts from an air pollution point of view, and they can also be tailored towards further improved combustion behavior.
Basic routes from renewable electricity to synthetic hydrocarbons start e.g. with water or steam electrolysis to produce hydrogen at times when there is a surplus of electrical energy. CO2 serves as a carbon source and must be available at the electrolysis site. It may be delivered from a storage or distribution system or occur as a side-product from another process not linked to simultaneous power generation from fossil fuels to qualify the approach as CO2-neutral. Potential sources of CO2 are facilities, in which biomass is converted via thermochemical or catalytic routes or anaerobic digestion, chemical plants where CO2 is a by-product, cement plants, and the like. This option then also requires techniques for capturing CO2 from the process streams in place. Another option is direct capture of CO2 from air. With regard to production of liquid fuels from hydrogen and CO2 two established major catalytic routes exist: methanol or direct dimethyl ether (DME) synthesis with subsequent conversion to gasoline and Fischer-Tropsch (FT) synthesis producing long-chained hydrocarbons, which are then hydrocracked to diesel or kerosene. However, both routes require the reduction of CO2 with hydrogen to CO at high temperature as an upstream step to produce a more reactive synthesis gas.