John Múnera

Operando Raman spectroscopic studies of lithium zirconates during CO2 capture at high temperature

Li2ZrO3 based sorbents were synthesized for CO2 capture at high temperature between 500 and 700 °C. Monoclinic ZrO2, tetragonal Li2ZrO3, Li2CO3, K2CO3 and LiKCO3 phases were detected by XRD and Raman spectroscopy. The sorbents showed high stability and moderate capture efficiency. The addition of K resulted in the improvement of capture efficiency from 0.052 g CO2 g mat−1 in materials without K to 0.083 g CO2 g mat−1 in the doped solid. Here, we report an experimental setup of Raman spectroscopy coupled with online mass spectrometry and a demonstration of its capabilities using lithium zirconates as sorbents for high temperature CO2 capture. Operando Raman spectroscopy allowed us to follow up the phase evolution during the capture process for the first time. The results obtained confirmed the presence of molten K and Li carbonates when the K-doped zirconates were exposed to CO2 at 500 °C.

A Study of the Adsorption Properties of Single Walled Carbon Nanotubes Treated with Nitric Acid

The changes observed in the properties of Single Walled Carbon Nanotubes (SWCNTs) after treatment with nitric acid are reported. The oxidized nanotube samples were characterized morphologically by scanning electron microscopy and structurally by Raman spectroscopy, thermogravimetric analysis, infrared spectroscopy and X-ray photoelectron spectroscopy. Gas adsorption was used to study the changes in the surface properties of the samples (including the changes in their porosity), as well as the changes in the adsorbate–adsorbent interactions which occurred as a result of the acid treatment. The adsorption studies were conducted using nitrogen at 77 K and CO2 at different temperatures between 263 K and 289 K at sub-atmospheric pressures. The isosteric heat was calculated from the data obtained and indicated a higher adsorbate–adsorbent interaction for the oxidized materials. A correlation was found between morphological and structural evolution and the adsorption properties of CO2, a probe gas which appears to be very suitable for characterizing the microporosity of these kinds of materials.