Metal oxide sorbents for carbon dioxide capture prepared by ultrasonic spray pyrolysis

Over the past 60 years, there has been a dramatic increase in the amount of carbon dioxide in the atmosphere. The rising CO2 levels can be traced to anthropogenic sources, the majority of which comes from burning fossil fuels for power generation. As a result, research is underway to incorporate CO2 capture into power plants using the integrated gasification combined cycle (IGCC), which is a method for cleaning flue gas produced from gasified coal. Presently, the lack of a cost-effective CO2 adsorbent is preventing the integration of CO2 capture into IGCC plants. There is much work being done on many classes of materials to solve this problem including supported amines, zeolites, activated carbons, metal oxides, lithium zirconates, hydrotalcites, and metal-organic frameworks. In the metal oxide class, calcium oxide is emerging as an attractive sorbent because it has a high capacity for CO2 (17.8 mmol g-1), is abundant in the form of limestone, and adsorbs CO2 at high temperatures, which can reduce costs by eliminating cooling of the gas for CO2 capture. Here, the results of CaO materials synthesized by ultrasonic spray pyrolysis (USP) are presented. It is shown that the morphology of USP-synthesized CaO sorbents can be easily controlled but that there is little difference between each sorbent in cyclic carbonation/calcination stability. Sorbents synthesized via USP, however, perform better than commercially available CaCO3. Finally, the effects of adding aluminum or magnesium binder phases on the cyclic stability and capacity of the sorbents are reported to greatly improve sorbent stability over 15 cycles