Sabatier reaction

The Sabatier process or the Sabatier reaction, named after the French chemist Paul Sabatier, describes a chemical reaction that converts the carbon dioxide and hydrogen to methane and water.

Reaction

The reaction is described by the following reaction equations:

The reaction is highly exothermic: Per volume% CO2, the temperature rise is 60 K (first case ).

At elevated temperature and elevated pressure, the reaction proceeds by using a nickel catalyst, more effective is the use of ruthenium on an alumina substrate. Often a Sabatier process in conjunction with a hydrogen electrolysis is technically relevant, as can be produced as methane and oxygen (see power-to - gas).

The reaction equation is then

Life support systems of spacecraft and space stations

Currently is obtained on the International Space Station oxygen from the electrolysis of water. Here, the excess hydrogen is released into space. The consumption of oxygen by the astronauts carbon dioxide is released, which is chemically bound and is removed from the process. This solution assumes that regular, relatively large amounts of water to be transported to the ISS, which are then used for the extraction of oxygen, but also for consumption, hygiene and More. When planning for future, longer missions and to reduce the water demand alternatives to the previous concept to be investigated.

For example, NASA is currently researching the application of the Sabatier reaction to in the exhaled " steam " to regain the water. In addition to the CO2 2 H2 (H2 from electrolysis, which is powered by solar power ) to form water, which, unintentionally, methane ( CH4) is produced. This additional product would probably lay off into space. Since half of the required hydrogen would be lost in the form of methane, hydrogen would have to be replenished periodically. Nevertheless, so the cycle would significantly better closed and correspondingly less hydrogen compared to the previous process, which uses the much heavier water needed.

The reaction equations of the process are as follows:

Bosch reaction, which on the direct route

Water generated is also being studied for the described application. The deposition of solid carbon on the catalyst is preparing but have problems, since this is reduced by the effective area of the catalyst.

Production of rocket fuel on Mars

The Sabatier process with subsequent electrolysis of water (see above ) was identified as a key factor for cost reduction ( manned ) missions to Mars. This is produced and stored in the form of methane and oxygen by use of locally available resources ( In-Situ Resource Utilization ) rocket fuel. Be consumed from the earth brought the hydrogen and carbon dioxide, which forms the main constituent of the Martian atmosphere. The stoichiometric mixture of fuel components is 3.5: 1 ( parts by mass) of oxygen to methane, wherein only a value of 2 by the simple Sabatier process: 1 is achieved. To increase the yield of oxygen, it makes sense to, in addition to let the water gas shift reaction to proceed in the reverse order, resulting in the following equation

The reaction is slightly exothermic, and by electrolysis of water, a mixing ratio of 4 would: 1 (slight excess of oxygen ) reach. Alternatively, could the methane produced in the Sabatier reaction partially pyrolyze ( see previous section). The resulting hydrogen may be reused in the Sabatier reactor to achieve the desired quantities of product ratio.

For the practical implementation it is planned to transport in an offshore, unmanned mission to Mars a reactor that produces methane and oxygen as fuel. This can be used by the subsequent manned mission for expeditions to Mars and for the return flight. It is crucial that a weight reduction of 18 by applying the described technologies: 1 can be achieved. This is possible because only the light element hydrogen has to be transported to Mars, the comparatively heavier elements carbon and oxygen are, however, produced locally ( in situ).

Converting electricity

A new approach is the conversion of electricity into synthetic natural gas. In this case, hydrogen is produced by electrolysis with an efficiency 57-73 percent with excess power first. With the Sabatier process then hydrogen and carbon dioxide is converted to methane, the methane ( CH4) can be stored on site or fed into natural gas pipelines and stored in large underground gas storage. On combustion, in which, for Z. (2011) advanced gas turbine SGT 5-8000 H, the efficiency is 60.3 % and thus the loss in this process section 39.7%.

Developed by the Centre for Solar Energy and Hydrogen Research Baden- Württemberg ( STW ) in Stuttgart and the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES ) in Kassel and built with the participation of SolarFuel GmbH demonstration plant with an electrical output of 25 kilowatts was since 2009 on STW in operation. CO2 source here was the ambient air. The plant in a container transportable constituted was operated in early 2011 for a long time even on CO2 exhaust stream of biogas upgrading a Biogasanlasanlage EWE AG in Werlte on raw biogas and a biogas plant of the Energy Landscape Morbach. Evidence of the production of a DVGW -compliant Erdgassubstitutes was provided in all cases.

Within the subsequent, running from 1 April 2011 to 31 March 2014, sponsored by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety joint project power-to - gas was in Stuttgart in October 2012 from STW participation of IWES and SolarFuel a 250 - kW research facility is put into operation. In it, in particular the plant equipment is to be tested for fast dynamic control that is required for the appropriate use of such a system for compensating for the variable electricity generation photovoltaics and wind energy. With this system, the precursor for industrial use is also achieved. For system sizes between one and 20 megawatts economical operation is expected. The aim of the project is to lay the foundations for the commissioning of a first Audi to produce gas for motor vehicles used 6 -megawatt pilot plant at the location of the biogas plant Werlte the project partner EWE, whose construction has already begun by SolarFuel. The gas will be routed via the public natural gas network to the gas stations, the electricity from renewable energy invested Audi in addition to four wind turbines in the offshore wind farm Riffgat.