CO₂ capture performance of a novel synthetic CaO/sepiolite sorbent at calcium looping conditions

Highlights: •A novel synthetic sorbent was fabricated from CaO and sepiolite by hydration. •Hydration temperature has an important effect on CO₂ capture by CaO/sepiolite. •MgO and Ca₂SiO₄ are formed in calcined CaO/sepiolite for hydration at 95 °C. •MgO and Ca₂SiO₄ improve sintering resistance of CaO/sepiolite during cycles. -- Abstract: A novel synthetic sorbent was fabricated from CaO and sepiolite by the hydration and its CO₂ capture performance was investigated during the calcium looping cycles. The effects of the sorbent preparation conditions including preparation method, hydration temperature, hydration duration and sepiolite content on CO₂ capture by synthetic CaO/sepiolite sorbent were examined in a dual fixed-bed reactor. The results showed that CaO/sepiolite possesses higher CO₂ capture capacity than original CaO. CO₂ capture capacity of CaO/sepiolite after 10 cycles is 39% and 56% higher than those of hydrated CaO and original CaO, respectively. The hydration temperature has an important effect on CO₂ capture by CaO/sepiolite during the preparation. When the hydration temperature is 95 °C, the obtained CaO/sepiolite exhibits the highest cyclic CO₂ capture capacity, because the good supports such as MgO and Ca₂SiO₄ are formed in the calcined CaO/sepiolite at 95 °C, which can improve the sintering resistance of CaO during the cycles. However, these supports are not found in the calcined CaO/sepiolite at the other hydration temperatures. In addition, CaO/sepiolite possesses more porous structure, larger surface area and pore volume, compared to hydrated CaO and original CaO. After the 1st calcination, the volume of pores in 10–100 nm in diameter of CaO/sepiolite is much higher than those of hydrated CaO and original CaO, respectively, which facilitates CO₂ capture of the sorbent. CaO/sepiolite appears promising as an effective and low-cost CO₂ sorbent at calcium looping conditions.