Conversion of CO2 by non- thermal inductively-coupled plasma catalysis

CO2 decomposition is a very strongly endothermic reaction where very high temperatures are required to thermally dissociate CO2. Radio frequency inductively-coupled plasma enables to selectively activate and dissociate CO2 at room temperature. Tuning the flow rate and the frequency of the radio frequency inductively-coupled plasma gives high yields of CO under mild conditions. Finally the discovery of a plasma catalytic effect has been demonstrated for CO2 dissociation that shows a significant increase of the CO yield by metallic meshes. The metallic meshes become catalysts under exposure to plasma to activate the recombination reaction of atomic O to yield O2, thereby reducing the reaction to convert CO back to CO2. Inductively-coupled hybrid plasma catalysis allows access to study and to utilize high CO2 conversion in a non-thermal plasma regime. This advance offers opportunities to investigate the possibility to use radio frequency inductively-coupled plasma to store superfluous renewable electricity into high-valuable CO in time where the price of renewable electricity is plunging.</p

Dry Reforming of Methane under Mild Conditions Using Radio Frequency Plasma

Dry reforming of methane (DRM) is a challenging process wherein methane reacts with CO2 to give syngas. This reaction is strongly endothermic, typically requiring temperatures higher than 500 °C. Catalysts can be used, but the high temperatures (which are a thermodynamic requirement) often lead to catalyst deactivation. Herein, the reaction from another conceptual direction is approached, using low‐power radio frequency inductively coupled plasma (RF‐ICP). It is demonstrated that this system can give high conversions of methane and CO2 at near‐ambient temperatures. Importantly, the energy costs in this system are considerably lower compared with other plasma‐driven DRM processes. Furthermore, it is shown that the yield of hydrogen can be increased by minimizing the C2 compound formation. The factors that govern the DRM process and discuss Hα emission and its influence on H atom recycling in the process are examined.</p

Enhancing CO2 plasma conversion using metal grid catalysts

The synergy between catalysis and plasma chemistry often enhances the yield of chemical reactions in plasma-driven reactors. In the case of CO2 splitting into CO and O2, no positive synergistic effect was observed in earlier studies with plasma reactors, except for dielectric barrier discharges, that do not have a high yield and a high efficiency. Here, we demonstrate that introducing metal meshes into radio frequency-driven plasma reactors increases the relative reaction yield by 20%–50%, while supported metal oxide catalysts in the same setups have no effect. We attribute this to the double role of the metal mesh, which acts both as a catalyst for direct CO2 dissociation as well as for oxygen recombination.</p

What to do with CO2?: Towards valuable chemicals using plasma and catalysis

This thesis describes different ways of converting CO2 to high value-added chemicals. For that, we tested traditional (γ-Al2O3, TiO2 and MgO based catalysts) and non-traditional (MAX phase and MXene based catalysts) materials in different thermocatalytic reactions: butane dry reforming (where CO2 reacts with butane to produce syngas), reverse water-gas shift (RWGS, where CO2 reacts with H2 to CO and H2O), and butane oxidative dehydrogenation (ODH) to produce butenes. In addition to thermal-catalysis, we used plasma-catalysis to perform CO2 splitting and CO2 hydrogenation to methanol. Overall, we found that Ti-based MAX phases are promising supports for CO2 conversion reactions due to their stability, acidity and electronic properties. We have also shown that MXenes are promising catalysts in redox reactions due to their electronic properties and their ability to stabilise vacancy sites. Regarding plasma-enhanced catalysis, we have seen that metal oxide supported catalysts are able to improve CO2 conversion and tune the selectivity in a DBD plasma setup, near ambient temperature and pressure. The metal loading and the metal oxide dispersion played important roles during CO2 hydrogenation. Similar materials had no catalytic effect during CO2 splitting in RF plasma. Nevertheless, we found that metal meshes can also act as catalysts under these conditions, increasing the CO yield

What to do with CO2?: Towards valuable chemicals using plasma and catalysis

This thesis describes different ways of converting CO2 to high value-added chemicals. For that, we tested traditional (γ-Al2O3, TiO2 and MgO based catalysts) and non-traditional (MAX phase and MXene based catalysts) materials in different thermocatalytic reactions: butane dry reforming (where CO2 reacts with butane to produce syngas), reverse water-gas shift (RWGS, where CO2 reacts with H2 to CO and H2O), and butane oxidative dehydrogenation (ODH) to produce butenes. In addition to thermal-catalysis, we used plasma-catalysis to perform CO2 splitting and CO2 hydrogenation to methanol. Overall, we found that Ti-based MAX phases are promising supports for CO2 conversion reactions due to their stability, acidity and electronic properties. We have also shown that MXenes are promising catalysts in redox reactions due to their electronic properties and their ability to stabilise vacancy sites. Regarding plasma-enhanced catalysis, we have seen that metal oxide supported catalysts are able to improve CO2 conversion and tune the selectivity in a DBD plasma setup, near ambient temperature and pressure. The metal loading and the metal oxide dispersion played important roles during CO2 hydrogenation. Similar materials had no catalytic effect during CO2 splitting in RF plasma. Nevertheless, we found that metal meshes can also act as catalysts under these conditions, increasing the CO yield

A Critical Look at Direct Catalytic Hydrogenation of Carbon Dioxide to Olefins

One of the main initiatives for fighting climate change is to use carbon dioxide as a resource instead of waste. In this respect, thermocatalytic carbon dioxide hydrogenation to high‐added‐value chemicals is a promising process. Among the products of this reaction (alcohols, alkanes, olefins, or aromatics), light olefins are interesting because they are building blocks for making polymers, as well as other important chemicals. Olefins are mainly produced from fossil fuel sources, but the increasing demand of plastics boosts the need to develop more sustainable synthetic routes. This review gives a critical overview of the most recent achievements in direct carbon dioxide hydrogenation to light olefins, which can take place through two competitive routes: the modified Fischer–Tropsch synthesis and methanol‐mediated synthesis. Both routes are compared in terms of catalyst development, reaction performance, and reaction mechanisms. Furthermore, practical aspects of the commercialization of this reaction, such as renewable hydrogen production and carbon dioxide capture, compression, and transport, are discussed. It is concluded that, to date, the catalysts used in the carbon dioxide hydrogenation reaction give a wide product distribution, which reduces the specific selectivity to lower olefins. More efforts are needed to reach better control of the C/H surface ratio and interactions within the functionalities of the catalyst, as well as understanding the reaction mechanism and avoiding deactivation. Renewable H2 production and carbon dioxide capture and transport technologies are being developed, although they are currently still too expensive for industrial application