Spray‐Dried Sodium Zirconate: A Rapid Absorption Powder for CO2 Capture with Enhanced Cyclic Stability

• Published in: ChemSusChem Vol. 10; no. 9; pp. 2059 - 2067
• Main Authors: Bamiduro, Faith, Ji, Guozhao, Brown, Andy P., Dupont, Valerie A., Zhao, Ming, Milne, Steven J.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 09.05.2017; John Wiley and Sons Inc
• Subjects: absorption; Bulk density; Carbon dioxide; Carbon sequestration; Carbonation; co2 capture; Diffusion rate; Dwell time; Growth models; High temperature; Hydrogen production; kinetic analysis; Nucleation; Phase separation; Reforming; Sodium; sodium zirconate; Spray drying; Thermogravimetric analysis; Thickness; Two dimensional analysis; Zirconium dioxide
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201700046

Improved powders for capturing CO2 at high temperatures are required for H2 production using sorption‐enhanced steam reforming. Here, we examine the relationship between particle structure and carbonation rate for two types of Na2ZrO3 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 CO2 conversion after a process‐relevant 5 min exposure to 15 vol % CO2. 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 (Na2CO3) within a crystalline ZrO2 particle matrix. Despite this phase separation, the reverse reaction to re‐form Na2ZrO3 could be achieved by heating each powder to 900 °C in N2 (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 Na2ZrO3 powder. Spray drying does the trick: We examine the relationship between particle structure and carbonation rate for two types of Na2ZrO3 powders. The hollow and perforated granular structure of spray‐dried Na2ZrO3 powders enables faster CO2 absorption than densely agglomerated conventional sorbents.