Lithium orthosilicate: synthesis and CO2 capture studies by in-situ synchrotron radiation power X-ray diffraction

M. L. GRASSO; V. BLANCO; F. COVA; LAROCHETTE, P. ARNEODO; F. C. GENNARI

Thessaloniki

Conferencia; EuroMat2017; 2017

Federations of European Materials Society

Lithium orthosilicate (Li4SiO4) is an attractive material forhigh-temperatureCO2capture due to its large theoretical CO2 sorption capacity (about 36wt%), its potential regeneration/reuse and its low cost. However, different silicates could be formed in the Li-Si-O system during synthesis, capture and regeneration processes which influence the Li4SiO4 technological performance. In this study, synthesis of Li4SiO4 from a ball milled Li2CO3 and SiO2 mixturewas followed during annealing in air by means of in-situ synchrotron radiation powder X-ray diffraction (SR-PXD). Formation ofLi4SiO4 was detected from 530 °C, whereas the apparitionof Li2SiO3as intermediate phasewas observedbetween 495 and560 °C.As interesting result, combination of ball milling with high surface area SiO2 precursor decreased the synthesis temperature of Li4SiO4 formation bellow 600 °C, compared with conventional solid-state synthesis that require high temperature (> 700 °C). The kinetics of CO2 capture/release of as-synthesized Li4SiO4 was investigated by in-situ SR-PXD, ex-situ X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), thermogravimetric measurements (TG) and temperature programmed carbonation (TPC)under pure CO2 and CO2/N2 flows. It was demonstrated by SR-PXD that Li4SiO4 slowly transforms to Li2CO3 and SiO2 from 390 °C, reaching about 34wt% of CO2 sorption at 720 °C. TG curve displayed a first stage of CO2 capture between 200 and 650°C, which was associated with CO2 superficial reaction. Then, a second sharp stage occurredbetween 650 and 720 °C due toCO2 capture in the silicate bulk due to the activation of the diffusion processes.CO2 absorption/desorption cycles were performed between 500-720 °C to evaluate the regeneration of the materialand its correlation with structural and microstructural changes of Li4SiO4. The performance of the as-synthesized Li4SiO4 shows good properties evidencing that this material can contribute towards CO2 capture from flue gases emitted by power plants.