Hydrogenation of carbon dioxide using LEDs energy

The hydrogenation of carbon dioxide into products such as methanol is a process which has been commonly performed in the industry. However, the energy required to carry out the reaction is high, and alternative routes to perform it with renewable energies have still too low efficiencies. Improving the efficiency working with energies such as solar energy is still a challenge.

Figure. 1. Inside view of different LED wavelengths used in the work

In this work, an experimental installation to use LEDs as energy source has been developed, as a previous step to use solar energy afterwards. The system allows to control perfectly light intensity, temperature, pressure and reactant flows, and the outlet stream can be directly analyzed by in-line gas chromatography. Visual light stimulation is provided by 36 LEDs, surrounding the reactor as shown in Figure 2.

Figure. 2. Microreactor assembly surrounded by white LEDs.

The reaction takes place in glass microreactors previously impregnated with Cu/ZnO catalysts, which have shown to increase the range of the solar spectrum used. The reason is the phenomenon known as surface plasmon resonance, that allows to increase the energy absorption at selected wavelengths changing the size and form of the nanoparticles of the catalyst.

First experiments working under low temperatures (50 – 70 ºC) and 20 bar have shown hopeful results, achieving CO2 conversion rates similar to other works working at much higher temperatures. A complete study of the influence of the variables such as pressure, temperature and reactant flows is being performed, in order to improve the efficiency of the process and to achieve the maximum CO2 conversion rate.

Sergio Muñóz

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