Fabrication of structurally improved KNaTiO3 pellets derived from cheap rutile sand for high-temperature CO2 capture

Official URL: https://dx.doi.org/10.1016/j.fuel.2023.129322

For the practical applications of CO2 sorbents, more studies on pellet rather than powder-type sorbents is a more mainstream research trend. In addition, high sorption kinetics, excellent cycling stability, and cheap raw precursors are far more important than its initial CO2 uptake value to a certain extent. Recently, alkali titanates have attracted growing attention as emerging and attractive high-temperature CO2 sorbent materials. Among the existing Na-doped alkali titanates, potassium sodium titanate (KNaTiO3) is one of the most promising high-temperature CO2 sorbent due to its high CO2 sorption rate and excellent cyclic stability. In order to promote its practical application in industry, a low-priced titanium ore was selected for the synthesis of KNaTiO3, and the optimized resulting sorbent maintained a rapid and reversible sorption capacity of 15.5 wt% after 100 cycles. Spherical pellets were fabricated by extrusion-spheronization method with cellulose and alumisol additives. The optimal pellets exhibited a relative compression strength of 4.15 MPa and an attrition rate of 1.2 wt% as well as maintaining a sorption capacity of 14.3 wt% after 50 cycles. It also showed superior CO2 capture kinetics, reaching a high CO2 removal rate of 92.5% within only 4 min (under 20% CO2). The role and mechanism of cellulose as pore-former were explored by SEM analysis and diffusion model fitting. In all, the optimized resulting sorbent pellets not only retained rapid CO2 sorption kinetics, high CO2 removal rate, excellent cyclic performance, but also ensure robust mechanical properties. These properties, as well as the low cost aspect, makes this newly developed KNaTiO3-based pellets to be highly promising for high temperature CO2 capture such as for biomass fired power plants or hydrogen production.