Mechanochemically and thermally induced CO2 transformations in the presence of silicate-based raw materials

Inglese

CCUS (Carbon Capture, Utilization, and Storage) is the acronym used in the scientific literature to indicate and include all the efforts addressed to control, re-use, and transform the CO2 in the atmosphere. It is in this pattern that the work of the present thesis has been developed, aimed at bringing a contribution to the study of the CO2 conversion into valuable products by resorting to “raw materials”, i.e. abundant and cheap minerals, as well as wastes arising from industrial processing of stone materials. The chemical reactivity of such solid systems has been studied by using mechanical energy and exploring different experimental conditions. Together with this, new composite catalysts based on modified silicate materials have been prepared by different routes and tested through thermal activation. The experimental activities covered different aspects, including the synthesis of new systems, the set-up of new chemical processes and activation routes, and a wide characterisation campaign, which was performed by resorting to several instrumental techniques. Mechanochemical activation of olivine-CO2-H2O and basalt-CO2-H2O systems resulted into high CO2 conversion and fast reaction kinetics formally occurring at room temperature and atmospheric pressure. This produced CO2 mineralisation products and CO2 reduction to hydrocarbons. Interesting data on innovative preparation routes and chemical compositions for environmental chemical processes were also obtained by studying thermally activated catalysts in the methanation reaction. The experimental trials performed either by the mechanochemically activated, either by thermally activated processes, allowed to highlight some mechanistic deductions relative to all the examined processes, although the detailed comprehension of all the steps of the complex reaction mechanisms, still requires further investigations