Controlled Oxidation State of Ti in MgO-TiO₂ Composite for CO₂ Capture

Abstract

Mesoporous MgO-TiO2 sorbents denoted as (xMgO-TiO2) with different Mg/Ti molar ratios were synthesized by single step evaporation-induced self-assemble (EISA) method for its application to CO2 capture. The effect of Mg/Ti molar ratio of mesoporous MgO-TiO2 sorbents on their physicochemical properties, oxidation state of titanium, and CO2 adsorption performance was investigated. The phase of xMgO-TiO2 was transformed in the sequence of MgTiO3 (Mg/Ti = 1.0 and 2.0) -> MgO-MgTi2O4 (Mg/Ti = 3.0 and 4.0) -> MgO-Mg2TiO4 (Mg/Ti = 5.0). However, with the increasing Mg/Ti molar ratio, CO2 adsorption performance increased in the order of MgTiO3 < MgO-MgTi2O4 < MgO-Mg2TiO4. Among the sorbents tested 3.0MgO-TiO2 showed the best CO2 adsorption performance corresponding to similar to 1 mmol/g (4.39 wt.%). It was observed that the MgTi2O4 (Ti3+-O-Mg2+) could create highly basic sites compared to MgTiO3 and Mg2TiO4. In the process of CO2 adsorption, high surface area (111.4 m(2)/g), large pore volume (0.45 cm(3)/g) as well as appropriate basic sites of Mg-O-Ti make it a plausible candidate for CO2 adsorption.