Spray‐Dried Sodium Zirconate: A Rapid Absorption Powder for CO(2) Capture with Enhanced Cyclic Stability

Improved powders for capturing CO(2) at high temperatures are required for H(2) production using sorption‐enhanced steam reforming. Here, we examine the relationship between particle structure and carbonation rate for two types of Na(2)ZrO(3) powders. Hollow spray‐dried microgranules with a wall thickness of 100–300 nm corresponding to the dimensions of the primary acetate‐derived particles gave about 75 wt % theoretical CO(2) conversion after a process‐relevant 5 min exposure to 15 vol % CO(2). A conventional powder prepared by solid‐state reaction carbonated more slowly, achieving only 50 % conversion owing to a greater proportion of the reaction requiring bulk diffusion through the densely agglomerated particles. The hollow granular structure of the spray‐dried powder was retained postcarbonation but chemical segregation resulted in islands of an amorphous Na‐rich phase (Na(2)CO(3)) within a crystalline ZrO(2) particle matrix. Despite this phase separation, the reverse reaction to re‐form Na(2)ZrO(3) could be achieved by heating each powder to 900 °C in N(2) (no dwell time). This resulted in a very stable multicycle performance in 40 cycle tests using thermogravimetric analysis for both powders. Kinetic analysis of thermogravimetric data showed the carbonation process fits an Avrami–Erofeyev 2 D nucleation and nuclei growth model, consistent with microstructural evidence of a surface‐driven transformation. Thus, we demonstrate that spray drying is a viable processing route to enhance the carbon capture performance of Na(2)ZrO(3) powder.