Effect of Zirconia Doping on the Structure and Stability of CaO-Based Sorbents for CO2 Capture during Extended Operating Cycles
Effect of Zirconia Doping on the Structure and Stability of CaO-Based Sorbents for CO2 Capture during Extended Operating Cycles
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DOI：
10.1021/jp207625c
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发表时间：
2011-12-22
影响因子：
3.7
通讯作者：
Smirniotis, Panagiotis G.
中科院分区：
文献类型：
--
作者：
Koirala, Rajesh;Gunugunuri, Krishna R.;Smirniotis, Panagiotis G.
采用火焰喷雾热解法（FSP）制备了一系列cao基吸附剂，并通过多种氧化锆负载原位掺杂，并在延长的操作周期内测试了它们的CO2捕获能力。其中，Zr/Ca摩尔比为5/10的吸附剂表现出最佳的性能和良好的稳定性，可循环1200次。该吸附剂在恶劣条件下表现出优异的耐高温烧结性能。其机械耐久性归因于形成分散良好的CaZrO3纳米颗粒，作为烧结的屏障，阻止CaO晶粒生长。x射线衍射（XRD）结果表明，制备的吸附剂中均有CaCO3和CaZrO3的生成。钙钛矿结构CaZrO3的峰值强度稳定在Zr/Ca = 5/10的摩尔比下。随着Zr掺杂量的增加，CaZrO3粒径减小，比表面积和孔体积增大，TPD主脱附峰向较低温度移动。Ca2p和Zr3d的电子结合能随着Zr含量的增加而减小，直至Zr掺杂5 mol / l，之后保持不变。同时，Ols电子结合能的XPS表明存在两种类型的氧，一种来自CaO，另一种来自CaZrO3。与Zr/Ca（5/10）吸附剂相比，Zr/Ca（6/10）吸附剂表面Zr的富集解释了CO2捕获能力急剧下降的原因。随着CaZrO3尺寸的减小和Zr/Ca摩尔比的微调，可以获得稳定的吸附剂，循环次数非常多，同时保持相对较高的CaO摩尔转化率（高达60%）。
A series of CaO-based sorbents are made using flame spray pyrolysis (FSP) and doped in situ by a wide range of zirconia loadings and tested for their CO2 capture during extended operating cycles. Among all these sorbents, the one with a Zr/Ca molar ratio of 5/10 exhibits optimum performance and remarkable stability up to 1200 cycles. That sorbent exhibited excellent resistance toward high temperature sintering under severe conditions. Its mechanical durability is attributed to the formation of well-dispersed CaZrO3 nanoparticles that act as a barrier against sintering, preventing CaO grain growth. X-ray diffraction (XRD) revealed the formation of CaCO3 and CaZrO3 in all sorbents made here. The peak intensity of the perovskite-structured CaZrO3 stabilizes at a molar ratio of Zr/Ca = 5/10. With increasing Zr doping, the CaZrO3 size decreases, the specific surface area and pore volume increase, while the major TPD desorption peak shifts to a lower temperature. Both Ca2p and Zr3d electron binding energies decrease with increasing Zr content up to 5 mols of Zr doping and remained constant beyond that. Also, XPS of the Ols electron binding energies suggests that there are two types of oxygen, one from CaO and another from CaZrO3. Surface enrichment of Zr of the Zr/Ca (6/10) sorbent explains the sharp drop in CO2 capture capacity compared to that of the Zr/Ca (5/10) sorbent. With the reduction of CaZrO3 size and fine-tuning of the Zr/Ca molar ratio, stable sorbents can be obtained for a very large number of cycles, while preserving relatively high CaO molar conversions (as high as 60%).