钙钛矿型载氧体的微波辅助合成与性能研究
发布时间：2018-09-06 11:41
【摘要】：CO2等温室气体的大量排放导致全球气候变暖,CO2减排成为重大紧迫需求。O2/CO2循环燃烧技术能大规模降低燃煤CO2排放,但制氧的高昂成本限制该技术发展。一种利用锅炉排出烟气中的二氧化碳和钙钛矿反应,生成氧气浓度较高的O2/CO2混合气体的链式制氧技术很有发展前景。为寻找一种释氧性能良好且结构稳定的钙钛矿型载氧体,本文通过正交实验改进了微波辅助溶胶凝胶法,合成了不同A位/B位组成的Ba-Co-O系列钙钛矿型金属氧化物,并通过固定床实验结合XRD和ESEM等分析手段对其反应特性以及循环性能等进行了实验研究。主要的实验内容和结论如下:固定床实验结果表明,A位、B位取代掺杂对钙钛矿载氧体的释氧性能有很大影响,A位应选择离子势小、离子半径大的碱土金属Ba,而B位应选择可变价离子势小的Co,BaCoO3-δ的释氧性能最好;BaCoO3-δ反应前后的ESEM图和XRD图得出,反应前样品蓬松多孔,主要是钙钛矿结构;反应后样品出现明显团聚,主要为BaCO3、Co3O4和CoO。BaCoO3-δ型载氧体与CO2反应释氧的最佳吸附、脱附温度都是850℃左右,释氧量随着吸附温度和脱附温度的增加先增加后减小;释氧量随着氧吸附时间增加而增加,超过30 min后增加缓慢;反应压力对反应影响很大,氧脱附量几乎随着压力增加呈线性增长。由正交实验得出微波辅助溶胶凝胶法的最佳条件为:pH值8,微波时间25 min,微波功率77%(额定功率700 W),马弗炉煅烧温度500℃,影响因素的主次顺序为:pH微波时间煅烧温度微波功率。ESEM图和XRD图分析得出正交实验制得的BaCoO3-δ均为钙钛矿相,偏酸性或强碱性前驱体溶液均不适合BaCoO3-δ钙钛矿晶体的生长,长时间大功率微波以及高温煅烧会使样品表面发生烧结。BaCoO3-δ的循环释氧性能良好,循环前后的ESEM图和BET结果表明循环后BaCoO3-δ样品变化不大,空隙减少不明显,能够为O2/CO2循环燃烧供给稳定的O2/CO2混合气体。
[Abstract]:Due to the large amount of greenhouse gas emissions such as CO2, global warming CO2 emission reduction becomes an urgent need. O2 / CO2 cycle combustion technology can greatly reduce CO2 emissions from coal combustion, but the high cost of oxygen production limits the development of this technology. A chain-type oxygen-making technology which uses the reaction of carbon dioxide and perovskite from flue gas from boiler to produce O2/CO2 mixed gas with high oxygen concentration has a good prospect. In order to find a perovskite-type oxygen carrier with good oxygen release performance and stable structure, the microwave-assisted sol-gel method was improved to synthesize Ba-Co-O series perovskite-type metal oxides with different A / B sites. The reaction characteristics and cyclic properties were studied by means of fixed bed experiment combined with XRD and ESEM. The main experimental contents and conclusions are as follows: the results of the fixed bed experiment show that the doping at the B site at the A site has a great influence on the oxygen release performance of perovskite oxygen carriers. The ion potential at the A site should be small. The Ba, of alkali earth metal with large ion radius and Co,BaCoO3- 未 with small variable valence ion potential should be chosen as the best oxygen releasing property. The ESEM and XRD diagrams before and after the reaction show that the sample is fluffy and porous, mainly perovskite structure. After the reaction, the samples showed obvious agglomeration, mainly the best adsorption of BaCO3,Co3O4 and CoO.BaCoO3- 未 oxygen carriers to CO2. The desorption temperature was about 850 鈩，
本文编号：2226239
[Abstract]:Due to the large amount of greenhouse gas emissions such as CO2, global warming CO2 emission reduction becomes an urgent need. O2 / CO2 cycle combustion technology can greatly reduce CO2 emissions from coal combustion, but the high cost of oxygen production limits the development of this technology. A chain-type oxygen-making technology which uses the reaction of carbon dioxide and perovskite from flue gas from boiler to produce O2/CO2 mixed gas with high oxygen concentration has a good prospect. In order to find a perovskite-type oxygen carrier with good oxygen release performance and stable structure, the microwave-assisted sol-gel method was improved to synthesize Ba-Co-O series perovskite-type metal oxides with different A / B sites. The reaction characteristics and cyclic properties were studied by means of fixed bed experiment combined with XRD and ESEM. The main experimental contents and conclusions are as follows: the results of the fixed bed experiment show that the doping at the B site at the A site has a great influence on the oxygen release performance of perovskite oxygen carriers. The ion potential at the A site should be small. The Ba, of alkali earth metal with large ion radius and Co,BaCoO3- 未 with small variable valence ion potential should be chosen as the best oxygen releasing property. The ESEM and XRD diagrams before and after the reaction show that the sample is fluffy and porous, mainly perovskite structure. After the reaction, the samples showed obvious agglomeration, mainly the best adsorption of BaCO3,Co3O4 and CoO.BaCoO3- 未 oxygen carriers to CO2. The desorption temperature was about 850 鈩，
本文编号：2226239
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