Catalysis Today 268 (2016) 46–59 Contents lists available at ScienceDirect Catalysis Today j o ur na l ho me page: www.elsevier.com/locate/cattod Electrochemically assisted synthesis of fuels by CO 2 hydrogenation over Fe in a bench scale solid electrolyte membrane reactor Esperanza Ruiz ∗ , Pedro J. Martínez, Ángel Morales, Gema San Vicente, Gonzalo de Diego, José María Sánchez Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Av. Complutense, 40, 28040 Madrid, Spain a r t i c l e i n f o Article history: Received 19 September 2015 Received in revised form 26 February 2016 Accepted 26 February 2016 Available online 11 March 2016 Keywords: Solid electrolyte Bench scale CO2 hydrogenation Fe-TiO2/YSZ Electrochemical promotion a b s t r a c t The electrochemically assisted synthesis of fuels by CO 2 hydrogenation was studied over a cheap, widespread and non-precious Fe catalyst in a bench scale oxygen ion conducting membrane (YSZ) reac- tor. The studies were performed under conditions representative of potential practical application i.e., under atmospheric pressure, at relatively low temperatures and high gas flow rates, with varying H 2 /CO 2 ratios and using gas compositions typical for postcombustion CO 2 capture exit streams and easily scalable catalyst-electrode configurations. The Fe-TiO 2 catalyst film was deposited by “dip-coating” and characterised both after pre-reduction and after testing. CO 2 conversion and selectivities to CH 3 OH and C 2 H 6 O can be enhanced up to 4, 50 and 1.7 times, respectively, by electrochemically controlled migration of O 2- promoting ions to or from the catalyst surface. The optimum temperature for the process was 325 ◦ C. Lower gas flow rates favoured the synthesis of CH 3 OH and C 2 H 6 O. CO 2 conversion and selectivities to CH 3 OH and C 2 H 6 O showed a maximum for a stoichiometric H 2 /CO 2 ratio of 3. Formation of C 3 H 6 and CO is strongly favoured for a H 2 /CO 2 ratio of 4 and 2, respectively, as a result of the increased and decreased hydrogen availability in the reaction system. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Due to the increase in CO 2 atmospheric levels and the dimin- ishing fossil fuel resources arising from wide spread production of energy by fossil fuels combustion, valorisation of CO 2 emissions to clean fuels is viewed as a complementary strategy to capture and storage for an effective quantitative reduction of the CO 2 emis- sions, allowing their recycling and, therefore, a more sustainable use of the energy resources. Chemical recycling of carbon dioxide from combustion power plants, as an energy carrier, can be accom- plished via its capture and subsequent hydrogenation to renewable, useful and environmentally neutral fuels (methane, methanol, dimethyl ether, etc.), provided that any available renewable energy source (wind, solar or hydraulic) is used for both production of nec- essary hydrogen (by water electrolysis) and chemical conversion of CO 2 . Moreover, it has been foreseen that increasing amounts of cheap CO 2 will be available from carbon sequestration in the near ∗ Corresponding author. E-mail address: esperanza.ruiz@ciemat.es (E. Ruiz). future. In this way, carbon dioxide can be chemically converted from a harmful greenhouse gas causing global warning into a valu- able, renewable, environmentally neutral and inexhaustible fuel source for the future [1–4]. Two main reactions can occur on co-feeding CO 2 and H 2 over a hydrogenation catalyst: x CO 2 + (2x - z + y)H 2 → C x H y O z + (2x - z)H 2 O (1) CO 2 + H 2 → CO + H 2 O△G ◦ = 19.9 kJ mol -1 (2) The former is the synthesis reaction resulting in the formation of hydrocarbons and/or oxygenates (alcohols or ethers). The latter is the reverse water gas shift (RWGS) reaction. Most studies on conventional catalytic hydrogenation of CO 2 to fuels, such as methanol and dimethyl ether, have been accom- plished using fixed-bed reactor configurations [3] of metal or metal oxide based catalysts supported on metal oxides [5] and at high pressures [6] to favour the CO 2 hydrogenation reaction. Electrochemical promotion is reported to be a very powerful tool, especially suitable for activation of very slow processes [7]. These processes if realized with conventional catalytic technologies need either extreme operating conditions (very high pressures and tem- http://dx.doi.org/10.1016/j.cattod.2016.02.025 0920-5861/© 2016 Elsevier B.V. All rights reserved.