Publications

Electrically polarized amorphous silica (aSiO2) is demonstrated to be an efficient and viable metal-free heterogeneous catalyst for the conversion of CO2 into valuable chemical products. The catalyst was prepared applying a thermoelectric polarization process in air to commercially available aSiO2 nanoparticles. Four polarization temperatures were assayed (150, 500, 800 and 1000 degrees C), the larger structural and chemical changes induced by the polarization treatment being observed at 150 and 500 degrees C. The polarization at such temperatures reduced considerably the electrical resistance of calcined aSiO2, while no significant change was detected at 800 and 1000 degrees C. Polarized aSiO2 was tested as heterogeneous catalysts for the reaction of CO2 with water at mild reaction conditions (120 degrees C, 6 bar of CO2, 40 mL of water, 72 h). The highest catalytic activity was observed with aSiO2 polarized at 150 degrees C, which was attributed to the structural defects induced during the thermoelectric polarization treatment. Thus, CO2 was converted into a mixture of formic acid (39.9%), acetic acid (44.4%) and dioxane (15.7%). Although the catalytic process was not selective, the yields were not only very high but also allowed obtaining a significant amount of dioxane, a product with four carbon atoms, which is very unusual in processes catalyzed by polarized ceramics. In summary, polarized aSiO2 can be used as a sustainable and low-cost raw material to prepare metal-free catalysts by means of a thermoelectric polarization process at 150 degrees C. This catalyst is capable of capturing CO2 to produce valuable chemical products by applying mild reaction conditions.

JTD Keywords: Alloy, Atom, Basis-sets, Bone, Catalysts, Hydroxyapatite, Nanocomposites, Nanoparticles, Oxidation, Performance