Free-Methane - from the Ionosphere of Mars Towards a Prototype Methanation Reactor: A Project Producing Fuels via Plasma Assisted Carbon Dioxide Hydrogenation

Abstract

A major challenge in the scientific research for strategies that use low-cost renewable energy is to design and develop heterogeneous /homogeneous catalysis processes that use waste CO₂ to produce fuels in a circular economy regime. In this paper a theoretical and experimental study aiming at reusing CO₂ and implementing a validated laboratory technology based on a prototype methanation reactor producing carbon neutral methane through the chemical conversion of CO₂ waste flue gases using renewable energies, is presented. The first operational line of the work is the theoretical, computational and experimental treatment of elementary reactive and non-reactive molecular processes occurring inside the reactor in order to optimize its operating conditions and to identify possible technological improvements that are more compatible with the environment. Experimental determinations of methane yield by the reactor have been carried out using CO₂ either taken from commercial bottles or produced from fermentation of wine and vegetable exhausted materials. To this end we have also undertaken a computational and experimental investigation of a new methanation pathway aimed at avoiding the use of the solid catalyst, by exploring mechanisms involving a plasma generation by electrical discharges or by vacuum ultraviolet (VUV) photons on CO₂ + H₂ gas mixtures. The measurements performed using a microwave discharge beam source developed in our laboratory gave useful indications on how to proceed to develop alternative solutions to the present Ni catalysed apparatus by resorting to a gas-phase-only process for the reduction of CO₂ to CH₄. These results demonstrate that the chemical reactivity of plasmas containing CO₂ should be strongly increased thanks to the presence of CO⁺ and O⁺ ions having a very high kinetic energy. These ionic species are produced via Coulomb explosion of CO₂²⁺ molecular dications by the same process responsible for the erosion of the atmosphere of Mars.