598 / 2019-01-20 12:36:25

Effect of organic precursors on the preparation of CaO sorbents for carbonate looping cycles

CO2 capture; CaO sorbent; wet mixing; citric acid

全体主题 > 燃料利用与化学循环技术

Global warming caused by greenhouse gases such as CO2 receives increasing attention in recent decades. The CaO-based high temperature carbonate looping cycles has been considered as one of the most promising CO2 capture technologies for its wide availability of raw materials and theoretical high adsorption capacity. However, the capture capacity of CaO dereases sharply with the increase of cycle numbers due to the sintering of CaO. Many methods have been applied to modify CaO sorbents including wet mixing, template synthesis and sol-gel combustion synthesis. In these methods, some organic materials are usually added during the preparation process, and the combustion of these organic materials produces a large amount of pores in the CaO sorbents, thereby improving the anti-sintering ability of the sorbents. However, there are few related studies on the influence of the content and type of organic compounds on the preparation process.
In this paper,a wet mixing-combustion method was used to synthesis CaO-based sorbents. Different amounts of organic citric acid were added during the preparation process to investigate their effects on the characterization and cyclic performance of CaO sorbents. The mass ratios of citric acid to CaO were 50:50, 60:40, 70:30 and 80:20, respectively. The reults showed that the mass ratio of citric acid significantly affected the cyclic performance of the sorbents. The addition of citric acid prevented the sintering of CaO crystal, increased the BET surface area and total pore volume. With the increase of the amount of citric acid, the pores of the sorbent become more abundant and the cyclic performance is also improved. SEM images showed the mass ratio of citric acid also greatly affected the grain size of CaO. Considering the cost of materials used, the optimal mass ratio of citric acid to CaO was 70:30, achieving the highest capture capacity of over 0.4 g CO2/g sorbent after 20 cycles. Further analysis suggested the linear relationship between the mass ratio of citric acid of critic acid and BET surface area of the sorbents.