Electricity as a raw material
Green energy for sustainable chemistry
The shift in energy and its concomitant low-CO2 electricity provide an opportunity to establish an electricity-driven production. Ten Fraunhofer institutes are developing and optimizing methods to utilize this electricity for the manufacturing of important basic chemicals. At the HANNOVER MESSE 2017 (April 24th to 28th, Hall 2, Booth C22), Fraun-hofer UMSICHT is presenting the Fraunhofer key project "Electricity as a raw material".
The stainless steel cylinder is located inside a massive metal frame with various hoses leading into it. With a diameter of 20 cm, it looks quite massive. However, its interior volume is surprisingly small – no larger than a beverage can. There is a reason for that: the cylinder is equipped with very thick steel walls that can withstand a pressure of 150 bar, 150 times the atmospheric pressure.
The prototype is located at Fraunhofer UMSICHT in Oberhausen (Germany). It is intended to manufacture alcohols such as ethanol from CO2 and water – important basic chemicals for the industry. However, the process is not driven by process heat generated from fossil fuel, but rather by green, regeneratively produced electricity.
Climate-friendly production of chemicals
The high pressure method is part of the Fraunhofer key project "Electricity as a raw material". "When talking about the shift in energy, the first thing that comes to mind is electro mobility," says project coordinator Dr. Hartmut Pflaum. But, as he points out, it is of equal importance to reduce the CO2-output of the industry. In order to manufacture chemicals, for example, quite often high temperatures are needed. The production is correspondingly energy-intensive, along with high CO2 emissions. In their key project, the Fraunhofer researchers are working on methods with which chemicals can be produced in climate-friendly manner in the future – specifically, with green electricity.
Already today, about 30 percent of our electricity is generated regeneratively. However, the production fluctuates: in case of sunshine and strong winds, wind turbines and solar cells deliver, in part, more electricity than is currently needed in the grid. "Electricity-based manufacturing methods can contribute towards an intelligent utilization of the supply and therefore the price fluctuations in the electric grid and can partially replace methods of fossil operation in the long-term," explains Dr. Pflaum.
This is made possible by electrochemistry. As part of the Fraunhofer key project "Electricity as a raw material", the specialists are focusing on the development of two different processes: on the one hand, they want to manufacture hydrogen peroxide (H2O2) – a disinfectant and bleaching agent – easily and reliably using electricity. On the other, they are trying to generate valuable basic chemicals such as ethene as well as various alcohols from electricity and CO2.
On-demand hydrogen peroxide production
Hydrogen peroxide is considered to be an environmentally friendly bleaching agent that is being utilized on a large scale for paper manufacturing, to bleach the cellulose. To date, the industry is producing the agent via the anthraquinone method. The latter, however, not only requires organic solvents but also copious amounts of energy. Therefore, the Fraunhofer researchers are exploring an alternative that works with electricity. The principle: similarly to a battery, the reactor contains a negative and a positive terminal. Once electricity is applied, protons are generated that can react with oxygen. Once success is achieved to optimally set the electricity and voltage values and the correct catalyst is being used, hydrogen peroxide is being generated. The challenge is to create conditions under which the hydrogen peroxide remains stable in a solution for an extended period of time.
Specifically, the researchers are developing two variants: In the first one, they are working on a reactor in which a membrane is separating the two terminals. It is of decisive importance to find a catalyst for the negative terminal that can set the reaction of hydrogen and oxygen into hydrogen peroxide in motion as effectively as possible. The second method is based on a diamond electrode. It is already being utilized for wastewater disinfection. The specialists are trying to modify it such that it can also manufacture hydrogen peroxide.
Both variants work, but the concentration of the hydrogen peroxide still needs to be increased. "In the end there is expected to be the insight which of the two methods is going to be working better," explained Dr. Pflaum. "Our objective is to bring both methods to near practical maturity." The vision: electrochemical reactors on the premises of a cellulose manufacturer always produce – potentially with the electricity from a neighboring wind park – as much bleaching agent as is needed by the paper manufacturer at any given time: hydrogen peroxide production on-demand.
Converting CO2 into products electrochemically
Another branch of the key project pursues a clearly more fundamental approach. Here, the specialists are trying to produce important basic chemicals that traditionally are generated from crude oil from electricity and CO2, instead. While an excess of CO2 exists, it is highly inert and only reluctantly forms compounds. "In order to it to react chemically, we have to activate it," explains Dr. Pflaum. "In the context of our key project, we are developing three prototypes that electrochemically convert CO2 into products."
- Ethene is a central intermediate product for the manufacturing of the standard plastic polyethylene. The Fraunhofer experts are developing a reactor that is based on a gas diffusion electrode. Therein, CO2 comes in contact with an electrolyte. With the help of a catalyst, ethene is generated at the electrode.
- Short-chained alcohols such ethanol and propanol serve as standard reaction partners in organic chemistry, but can also serve as fuel. With a novel high pressure reactor, the scientist are working on chemically activating compressed CO2 and letting it react with hydrogen to form alcohol molecules.
- Long-chained alcohols serve, among other things, as softeners, tensides, and fuel additives. To generate them in an environmentally friendly way, the researchers are developing a two-stage process: first, from water and CO2, they generate a synthesis gas consisting of carbon monoxide and hydrogen by means of high temperature electrolysis. This gas is then form chains of long alcohol molecules by means of a Fischer-Tropsch synthesis.
"Once we are able to show the feasibility of these processes, they become attractive alternatives for the chemical industry," according to Dr. Pflaum. Then, the new, climate-friendly methods could be developed further, jointly with the industry, into pilot plants.
HANNOVER MESSE 2017
Fraunhofer UMSICHT will be represented at the HANNOVER MESSE, April 24-28, 2017, at the joint booth of the Fraunhofer-Gesellschaft (Hall 2, Booth C22). The following exhibits will be on display:
A stack made of solid oxide cells for power-to-gas processes and vice versa that is stable at high temperatures.
Model of a high-pressure electrosynthesis apparatus
Replica of a high-pressure cell with integrated electrodes will be exhibited in a structure made of Plexiglas reminiscent of an advertising pillar. The cylindrical structure has a diameter of approx. 80 cm.
Membrane samples of a cost-efficient, proton-conducting membrane with a low fluorine content based on alternative polymer classes (size 7 cm x 7 cm) for electrochemical H2O2 synthesis.
Simulation, multi-criteria optimization, decision support: electrosynthesis application
Interactive software for the visualization and analysis of multivariate data records as well as for decision support.
Fraunhofer key project
With its key projects, the Fraunhofer-Gesellschaft sets strategic focal points to quickly convert scientific ideas into market-ready products and into specific solutions for the industry. The participating Fraunhofer institutes contribute their competencies and early on integrate industry partners. In the key project "Electricity as a raw material", ten institutes have joined forces: UMSICHT (overall control), IAP, ICT, IGB, IKTS, ISC, IST, ITWM, IVV and WKI. The project started on August 1, 2015 and has a planned completion date of July 31, 2018.