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ePaper created 2017-03-14, 10:25:37 | version 1.49.03
CHEMISTRY AND PROCESS INDUSTRY H2O (+ CO2) O2 (+ oxidation product) e l e renewable energy solutions c t ri c it y air 2 C O H2 + CO2- reduction product electro-catalytic reactor fermentation separation final product 1 CO2 adsorption / desorption electrochemical technologies biotechnologies downstream processing PRODUCTION OF CHEMICALS FROM CO2 Tobias Gär tner, Lénárd - Ist van Csepei, Luciana Vieira, Fabian Stef fler, Thomas Michael Scherer, Si e g fr i e d Eg n e r, Vo lke r Si e b e r mixture of water-soluble C1 intermediates such as formate, formaldehyde or methanol using a gas diffusion cathode. At the same time, the process water of the fermentation is re- processed at the anode. The C1 intermediates of the cathode reaction are converted directly into isoprene and/or monoter- penes and lactic acid via an integrated fermentation process. In addition to the innovative combination of electrochemical and biotechnological procedural steps, the integration of the reactors into one system and the associated heat and material low management are also being investigated for the develop- ment of the technology platform. Catalysts for electrochemical conversion of CO2 A key step for CO2 activation in the low-pressure process line is the development of a gas diffusion electrode and its inte- gration into an electrochemical cell, in cooperation with Gas- katel GmbH. Firstly, mass transport via phase boundaries and multiple-electron transfer have to be optimized to CO2, and, secondly, suitable catalysts have to be developed in order to minimize the energy input in the conversion of H2O and CO2 to C1 intermediates. Since the start of the project, Fraunhofer IGB has already produced and characterized a large number of catalysts using various preparation methods. Inter alia, copper-based catalysts are used and also tested under continuous process conditions. For the simultaneous process water treatment, the use of boron-doped diamond electrodes is tested, which ensures an ideal hydroxyl radical production, thus enabling an effective process water treatment. Baseline situation and project goal In the coming decades, the use of CO2 as a source of carbon for the production of key chemicals by direct use of renewable energy will become strategically important. The advantage of this process is that not only are greenhouse gas emissions reduced, but CO2-neutral compounds are generated as well. CO2 sources from fermentation processes (e.g. alcoholic fer- mentation in breweries or distilleries) are generally available. Their CO2 content is high. However, only CO2 recovery from the air or exhaust gas streams will provide a signiicant CO2 share of the future need for the CO2-to-chemicals processes [1]. A further necessity is the use of renewable energy sources or chemical reduction equivalents such as hydrogen. These are usually decentralized under today’s conditions, which is in line with the power-to-gas technology [2]. Therefore, the project “Cost-effective CO2 conversion into chemicals via combination of Capture, ELectrochemical and BIochemical CONversion technologies – CELBICON” aims at new CO2-to- chemicals technologies, which (a) have a modular design and a scalability for decentralized use, (b) high material and energy eficiency, (c) low investment and operating costs, and (d) high robustness with simultaneous variability (Fig. 1). Technology platform The project, launched in March 2016, involves a high-pressure and a low-pressure process line. Fraunhofer IGB is developing a technology platform for the low-pressure line. An energy and resource-eficient integrated process is being developed to produce high-quality chemicals such as isoprene or lactic acid from atmospheric CO2 by combining electrochemical and biotechnological catalysis (Fig. 2). In the electrochemical step, the CO2 provided by Climeworks AG is converted into a 8 2