Durability of CaO-CaZrO sub(3) Sorbents for High-Temperature CO sub(2) Capture Prepared by a Wet Chemical Method

Powders of CaO sorbent modified with CaZrO sub(3) have been synthesized by a wet chemical route. For carbonation and calcination conditions relevant to sorbent-enhanced steam reforming applications, a powder of composition 10 wt % CaZrO sub(3)/90 wt % CaO showed an initial rise in CO sub(2) uptake capacity in the first 10 carbonation-decarbonation cycles, increasing from 0.31 g of CO sub(2)/g of sorbent in cycle 1 to 0.37 g of CO sub(2)/g of sorbent in cycle 10 and stabilizing at this value for the remainder of the 30 cycles tested, with carbonation at 650 degree C in 15% CO sub(2) and calcination at 800 degree C in air. Under more severe conditions of calcination at 950 degree C in 100% CO sub(2), following carbonation at 650 degree C in 100% CO sub(2), the best overall performance was for a sorbent with 30 wt % CaZrO sub(3)/70 wt % CaO (the highest Zr ratio studied), with an initial uptake of 0.36 g of CO sub(2)/g of sorbent, decreasing to 0.31 g of CO sub(2)/g of sorbent at the 30th cycle. Electron microscopy revealed that CaZrO sub(3) was present in the form of less than or equal to 0.5 mu m cuboid and 20-80 nm particles dispersed within a porous matrix of CaO/CaCO sub(3); the nanoparticles are considered to be the principal reason for promoting multicycle durability.