Macro-structured materials for methanol synthesis from biogas by non-thermal plasma – MACROPLAS

The simultaneous recovery of CH4 and CO2, the main constituents of biogas, is of great interest and is fully in line with the issue of global warming linked to the increase in greenhouse gas emissions. Biogas obtained by anaerobic fermentation of agricultural waste is widely used in Europe to locally supply heat or electricity delivered to the grid. Also, when energy needs are lower, it becomes important to offer other outlets for biogas, such as the production of chemical compounds (methanol or hydrocarbons) which is considered as an alternative to the use of fossil carbon. However, the cost of the on-site process requires significant advances and breakthrough processes are sought after, among them the use of a non-thermal plasma (PNT) is of great interest. In a non-thermal plasma the gas is partially ionized, it is made up of ions, radicals, electrons and excited species. It is particularly suited to the operation of relatively small units and can therefore be perfectly combined with anaerobic digestion. It also has the advantage of operating at atmospheric pressure and room temperature in "on / off" mode.
The synthesis of methanol under plasma discharge was demonstrated at the end of the 90s, therefore the proof of concept of the project exists. However, there are many challenges to be taken up in order to improve energy efficiency and increase the selectivity in high added value products, this last aspect requires coupling plasma and solid catalyst. Numerous studies have been carried out but the development of new catalysts and the understanding of the interactions between plasma and solid must be deepened. It is in fact expected that an optimal catalyst under plasma discharge is not the most efficient in conventional thermal catalysis since the presence of a solid in the plasma zone modifies the discharge and vice versa. Furthermore, the use of materials in powder form, conventionally used in catalysis, is poorly suited to plasma-catalysis coupling because the gas volume (in which the plasma is generated) is limited to the space between the catalyst grains. Therefore, we consider that the use of shaped materials is necessary in order to make the most of the plasma-catalysis coupling. This is also based on work which has shown the good stability of the discharge in foams or monoliths.
In this project, the teams of IRCER in Limoges, PPrime and IC2MP in Poitiers propose to coordinate their research work in order to propose a route for the direct synthesis of methanol from methane and carbon dioxide using an original route coupling non-thermal plasma and geopolymer foams. In fact, geopolymer materials are promising candidate for this application due to their synthesis at low temperature with adaptable porosity and easy shaping.
The present project aims at acquiring new insights into the coupling of plasma and a catalyst by using ceramic geopolymer foams possessing macro-porosity thought to favor the transformation of biogas into methanol. The ambitiousness of the project relies not only on the use of new shaped macro-porous catalyst but also on the development of numerical simulation for a better understanding of plasma-catalysis interaction. To reach such a target, an interdisciplinary approach will be used, mobilizing chemists and physicists. The simultaneous research efforts will be developed within three tasks (i) synthesis of new shaped catalytic geopolymer materials, (ii) evaluation of catalytic performances and kinetic data acquisition (iii) thorough analysis of the basic physical mechanisms involved at the plasma/catalyst interface.