Conversion of Carbon Dioxide and Hydrogen To Hard Aliphatic Waxes

The present work describes the technological advances carried out within the EU Horizon 2020 project ICO2CHEM (From industrial CO2 streams to added value Fischer-Tropsch chemicals). The aim of the project is to study how a pilot-scale synthesis reactor technology can exploit waste CO2 from an industrial plant to produce hard aliphatic waxes. The integrated pilot plant is tested in a real industrial environment – the Industriepark Höchst in Frankfurt am Main (DE). Carbon dioxide is recovered from a biogas upgrading plant, while H2 is recovered from an on-site chlor-alkali plant. The key processes required for carbon dioxide capture and utilization are a reverse water-gas shift (RWGS) and a modular Fischer-Tropsch reactor (FT). In the ICO2CHEM project, RWGS and FT reactors are coupled in a mobile synthesis unit (MOBSU), that is a transportable container developed by project partners VTT from Finland and Ineratec from Germany, which allows flexibility of conversion of waste gases coming from several industrial sources (e.g., chemical plants or biogas-upgrading plants). The RWGS breaks catalytically the bonds of CO2 via the reaction CO2+H2CO+H2O. The syngas leaving the RWGS reactor undergoes a stepwise polymerization reaction over the Fischer-Tropsch catalyst to yield heavier carbon compounds (i.e., a syncrude), mainly composed of paraffins (ca. 95/96 wt.%) and olefins (ca. 5/4 wt.%). One of the challenges and goals of the project is increasing the synthesis yield of the high molecular weight fraction of products, i.e., waxes with carbon number C>45/50, used as synthetic raw materials for paint, coating and sealant additives by project partner Altana from Germany. Thus, in this study, we describe the conversion of waste gases to useful products with insight on the kinetics of the Fischer-Tropsch unit and the further scale-up from MOBSU to full-scale plant. The scale-up model considers an increment of the processed CO2 from about 10 to 300 kg/h. Kinetic studies have been performed on an FT cobalt catalyst manufactured by VTT, testing it at different process conditions (by varying temperature, pressure and feed composition). The final kinetic model has been implemented into a process simulator that solves mass and energy balances for the MOBSU, as well as for the scaled-up plant. Finally, it is possible to identifying the optimal configuration and operations of the full-scale plant components to maximize the wax throughput and CO2 emissions reduction.