Global warming, one of environmental concerns which occurs because of greenhouse gas emission like CO2, now becomes increasingly severe and causes wide range of impacts, especially extreme climate change reported worldwide. Therefore, researchers aim to reduce the emission of CO2 by converting to high value chemical products such as olefins and alcohol that can be used as an alternative energy. By the stated aim, market value of CO2 will be increased and stability of raw materials will be sustained. CO2 conversion needs to be conducted under high-pressure (reaction that overall moles of product are decreased) and high temperature (according to thermodynamics data) and produced several competitive reactions. Thus, based on the magnetic character of catalyst, the magnetic field was applied to control the reaction.
Hence, the collaborative research between the Faculty of Engineering, Kasetsart University and Synchrotron Light Research Institute (Public Organization) was organized to study an influence of magnetic field upon effectiveness of methanol synthesis via CO2 hydrogenation over iron and copper catalysts with two types of supports i.e. core–shell and infiltrate aluminosilicate. We also investigated phase change of both catalysts in a temperature range at 50 – 480 degree Celsius. In the study, the in situ x-ray absorption near-edge structure (XANES) measurement was performed at Time-resolved X-ray Absorption Spectroscopy (TRXAS) beamline. The results showed that CuO were totally reduced into Cu at 150 – 200 degree Celsius while the mixed phases of iron oxides (Hematite (Fe2O3), Magnetite (Fe3O4), and ferrous oxide (FeO)) were observed at 340 – 480 degree Celsius. However, at the end of reduction process, the Fe and FeO were obtained as a final species (Figure 1). These in situ XANES results suggested that the active species of iron for CO2 hydrogenation were Fe and FeO. Furthermore, under magnetic condition, we also found the enhancement of its catalytic efficiency. Although Cu is a diamagnetic material and its magnetic current flows in an opposite direction to magnetic field, it can be induced to express magnetic property when being placed near FeO in the field which well-enhance catalysis efficiency. The CO2 conversion rate over catalysts with 27.7 mT of magnetic field intensity at 260 degree Celsius was at 1.5 – 1.8 times higher than in a reaction without the field. In addition, Methanol and Dimethyl Ether (DME) selectivity percentages increased by 2.5 – 5.3 times when magnetic field was used. The higher rate was due to more active sites within catalysts when magnetic field is presented, causing catalysts to absorb CO2 and hydrogen more effectively. Therefore, the presence of magnetic field in this reaction highly enhances a carbon-neutral route of CO2 utilization.
Figure 1: In-situ Fe K-edge XANES spectra (before and after being reduced) of two catalysts:
(a) 10Fe/core-shell mesoporous aluminosilicate; and
(b) 10Fe-10Cu/core-shell mesoporous aluminosilicate and spectra of iron standards
Mr. Wasakorn Umchoo1, Dr. Yingyot Poo-arporn2, Dr. Waleeporn Donphai1,3, and Dr. Metta Chareonpanich1,3
1Department of Chemical Engineering, Faculty of Engineering, Kasetsart University
2Synchrotron Light Research Institute (Public Organization)
3Center for Nanoscale Materials Design for Green Nanotechnology and
Center for Advanced Studies in Nanotechnology for Chemical, Food and Agricultural Industries,
National Science and Technology Development Agency