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Structural evolution in synthetic, Ca-based sorbents for carbon capture

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Liu, W 
González, B 
Dunstan, MT 
Saquib Sultan, D 
Pavan, A 


The carbonation of CaO-based materials at high temperatures (e.g. > 600°C) is a promising method of capturing CO₂ emitted from, e.g. the combustion of carbonaceous fuels. The resulting CaCO₃ can be regenerated by calcination at a temperature at which the equilibrium partial pressure exceeds that of the local partial pressure of CO₂ (e.g. 950°C). A process involving repeated cycles of carbonation and calcination of a calcareous material is called calcium looping. The capacity of a CaO-based sorbent to accept and reject CO₂ over many cycles is governed by a number of factors, such as chemical composition, surface morphology and pore structure, all of which often evolve with cycling. The present paper investigates the underlying mechanisms controlling the evolution of the micro-structures of a series of synthetic sorbents consisting of CaO mixed with the inert supports Ca₁₂Al₁₄O₃₃ and MgO. These sorbents were subjected to cycles of calcination and carbonation and were characterised using a variety of in situ and ex situ techniques. It was found that the balance between the degree of surface cracking during calcination and the extent of sintering during carbonation was responsible for changes in uptake during cycling, giving an increase in uptake for the supported CaO and a decrease for the unsupported CaO.



Carbon dioxide, Absorption, Reaction engineering, Materials, Sintering

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Chemical Engineering Science

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Elsevier BV
Engineering and Physical Sciences Research Council (EP/K030132/1)
The authors would like to thank the Australian Synchtrotron for the award of beamtime, and Justin Kimpton and Qinfen Gu for their help with the design and operation of the in situ gas flow capillary XRD cell. Mr Zlatko Zaracevic is acknowledged for the BET measurements. W.L acknowledges funding from the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme. B.G acknowledges the EU Research Fund for Coal and Steel (project number RFCR-CT-2012-00008). M.T.D acknowledges funding from the Cambridge Commonwealth Trusts and Trinity College, Cambridge and the EU ERC for an advanced fellowship for CPG. D.S.S acknowledges financial support by Engineering and Physical Sciences Research Council (EPSRC). C.D.L acknowledges funding by the Australian Research Council (Discovery Projects).