Investigation of Olivine and Carbon Dioxide interaction through mechanically induced Serpentinization process.

ALESSANDRO TARAS; FABIANA GENNARI; GABRIELE MULAS; VALERIA FARINA; NADIA S. GAMBA; STEFANO ENZO; M. DOMENICA SIMULA; SEBASTIANO GARRONI

Sassari

Otro; Sardiniachem; 2019

Sezione Sardegna della Società Chimica Italiana

Global warming is the biggest threat we face these times. Climate change seems to be irreversible and it?s affecting ecosystems and consequently the health of the whole population. The energy demand, in continuous growth, has led to increased fuel consumption and then to the release in the atmosphere of a huge amount of carbon dioxide, CO2, which is the greenhouse gas with the major contributor to global warming.The Paris Agreement set out the commitment to reduce greenhouse emissions and to limit climate change, limiting the global temperature rise to 1,5 °C. Only 153 of 197 parties of the United Nation Framework Convention on Climate Change (UNFCCC) ratified the agreement, covering 84,7% of greenhouse gas emissions at present, but these contributions are not enough to the necessary reductions by 2030 to meet the 2°C pathway (above the pre-industrial level). Natural processes cannot absorb all the anthropogenic produced carbon dioxide in these centuries, so the development of key technologies and strategies for capture and conversion is urgently required. Carbon capture and storage technologies allow the capture of more than 90% of CO2 emissions produced mainly from fossil fuels combustion in industrial processes and electricity generation. An alternative to CCS, or linked to it, are the CO2 Capture Utilization technologies (CCU): captured CO2 is converted on different products via chemical, biochemical, photochemical or electrochemical reactions. These products may then be used as either feedstock for value-added chemicals (e.g. organic and inorganic carbonates, polymers, urea etc.), or as a medium for intermediate energy storage (e.g. methane, syngas).In this contest is included the present project, which aims to convert CO2 into Hydrocarbons through the Olivine Serpentinization process. Olivine is a natural mineral consisting of a solid solution of fayalite (Fe2SiO4) and forsterite (Mg2SiO4). In nature, these silicates bind 100 million tons of CO2 per year, according to a slow natural process by atmospheric agents. The CO2 sequestration in natural silicates is promoted by the occurrence of the serpentinization process. It is a widespread phenomenon on Earth during which mineral based silicates of Fe and Mg react with water to give H2 and minerals of the serpentine group [(Mg, Fe)3Si2O5(OH)4]. This involves the formation of extremely reducing fluids, rich in Hydrogen, so any species present, such as inorganic C, can be reduced. Therefore, CO2 reacts with H2 through a Fischer-Tropsch type or Sabatier mechanism to give CH4 and light hydrocarbons. Although is a thermodynamically favoured process, the rate of the reaction is very slow but the kinetics of the process can be increased through a preliminary treatment of the mineral. We focus our attention on the mechanochemical activation of Olivine in the presence of H2O and under CO2 atmosphere, to investigate the gas-solid reactions. The mechanochemical process was carried out in high energy laboratory mills, properly modified in order to control the dynamic parameters. Chemical reactivity and reaction rates were investigated under different experimental conditions, evidencing increased performances with respect to hydrothermal process reported in literature.