碳模板法改性的NaNO_(3)修饰MgO脱碳性能研究

Study on the CO_(2) Sorption Performance of NaNO_(3)-Promoted MgO Prepared via Carbon Template

镁基吸附剂是适用于IGCC电站与燃烧前CO_(2)捕集结合、最具发展前景的固体吸附剂之一。纯MgO吸附剂的理论吸附量很高,其实际CO_(2)吸附效果却并不理想,对其掺杂碱金属盐复合形貌改性是提高其吸附性能的有效手段。该文利用D-葡萄糖酸为碳源,以碳模板法制得了一种NaNO3改性MgO吸附剂,并提出两段吸附法进行循环实验。结果表明:碳模板法能使吸附剂呈现出高比表面积的纳米级薄片状颗粒,吸附温度提前,在小于300℃时诱导期缩短,吸附速率变快;利用其双峰吸附特性的两段吸附法更是能让其首个循环吸附量达到0.82g/g_(sorbent),在经历了8个循环时其CO_(2)吸附量仍能达到0.4g/g_(sorbent)。该文还使用双指数函数对其恒温吸附曲线进行了动力学分析,发现使用碳模板法负载的吸附剂无论是快速反应阶段还是产物层扩散阶段的反应系数都提高了一个数量级以上,两个阶段反应的活化焓均降低。

Magnesium-based sorbents has been recognized as one of the most promising candicates for pre-combustion CO_(2) capture technologies for IGCC power plants. Although the theoretical adsorption capacity of pure MgO sorbent is pretty high, it is clearly not ideal for its practical CO_(2) adsorption performance. Therefore, it is significant to improve the adsorption performance by modification with alkali salt and altering morphology. NaNO_(3) modified MgO adsorbent was prepared by carbon template, which used D-gluconic acid as carbon source, and the two-stage adsorption method was proposed at the same time. The results revealed that NaNO_(3)-promoted MgO prepared via carbon template can exhibit a sheet-like nano-particles with high specific surface area, decrease the initial sorption temperature,shorten the initial induction and enhance the CO_(2) sorption rate. And it is the two-stage adsorption, based on its unique bimodal sorption characteristic, allowed the CO_(2) uptake of MgO/NaNO_(3)-0.4 reached 0.82 g/g_(sorbent) at the first cycle and still 0.4 g/g_(sorbent) at the eighth cycle, respectively. The sorption kinetics were obtained through isothermal thermogravimetry and elucidated using a double exponential model, which demonstrated that the carbon template preparation can enhance both surface chemisorption and product layer diffusion more than one order of magnitude and the activation energy values decreased at both stages.