Assessment of the potential use of zeolites synthesized from power plant fly ash to capture CO2 under post-combustion scenario

Abstract

Two types of zeolites (type X and type A) were synthesized from fly ash of two Brazilian coal based power plants via hydrothermal treatment after ash fusion with NaOH. The synthesized zeolites were characterized by means of XRF, XRD, SEM and gas adsorption (N2 and CO2 adsorption/desorption at − 196 and 0 °C, respectively). Pure CO2 and N2 adsorption equilibrium isotherms were performed at 50, 70 and 90 °C to measure the CO2 adsorption capacity and selectivity of CO2 over N2. CO2/N2 binary isotherms (15/85% v/v) were also obtained at the same temperatures. Commercial zeolitic materials used for CO2/N2 separation such as zeolite 13X and zeolite 4A underwent the same characterization and adsorption measurements as benchmarks to evaluate the performance of the synthesized zeolites. The synthesized materials from fly ash are promising low cost adsorbents for CO2 separation, reaching ca. 83% of the CO2 adsorption capacity of their commercial counterparts at 0.15 bar and 50 °C.