Highly Efficient CO_2 Sorbents: Development of Synthetic, Calcium- Rich Dolomites

摘要

The reaction of CaO with CO; is a promising approach for separating CO_2 from hot flue gases. The main issue associated with the use of naturally occurring CaCO_2, that is, limestone, is the rapid decay of its CO_2 capture capacity over repeated cycles of carbonation and calcination. Interestingly, dolomite, a naturally occurring equimolar mixture of CaCO, and MgCO_3, possesses a CO_2 uptake (bat remains almost constant with cycle number. However, owing to the large quantity of MgCO_3 in dolomite, the total CO_2 uptake is comparatively small. Here, we report the development of a synthetic Ca-rich dolomite using a coprecipitation technique, which shows both a very high and a stable CO_2 uptake over repeated cycles of calcination and carbonation. To obtain such aa excellent CO_2 uptake characteristic it was found to be crucial to mix the Ca~(2+) and Mg~(2+) on a molecular level, that is, within the crystalline lattice. For sorbents which were composed of mixtures of microscopic crystals of C_2CO_3 and MgCO_3, a decay behavior similar to natural limestone was observed. After 15 cycles, the CO_2 uptake of the best sorbent was 051 g CO_2/g sorbent exceeding the CO_2 uptake of limestone by almost 100%.