Jahandar Lashaki Masoud, Ziaei-Azad Hessam, Sayari Abdelhamid
Centre for Catalysis Research and Innovation (CCRI), Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.
ChemSusChem. 2017 Oct 23;10(20):4037-4045. doi: 10.1002/cssc.201701439. Epub 2017 Sep 26.
The hydrothermal stability of triamine-grafted, large-pore SBA-15 CO adsorbents was studied by using steam stripping. Following two 3 h cycles of steam regeneration, lower CO uptakes, lower CO /N ratios, and slower adsorption kinetics were observed relative to fresh samples, particularly at the lowest adsorption temperature (25 °C). CO adsorption measurements for a selected sample exposed to 48 h of steam stripping depicted that after the initial loss during the first exposure to steam (3-6 h), the adsorptive properties stabilized. For higher adsorption temperatures (i.e., 50 and 75 °C), however, all adsorptive properties remained almost unchanged after steaming, indicating the significance of diffusional limitations. Thermogravimetric analysis and FTIR spectroscopy on grafted samples before and after steam stripping showed no amine leaching and no change in the chemical nature of the amine groups, respectively. Also, a six-cycle CO adsorption/desorption experiment under dry conditions showed no thermal degradation. However, N adsorption measurement at 77 K showed significant reductions in the BET surface area of the grafted samples following steaming. Based on the pore size distribution of calcined, grafted samples before and after steaming, it is proposed that exposure to steam restructured the grafted materials, causing mass transfer resistance. It is inferred that triamine-grafted, large-pore SBA-15 adsorbents are potential candidates for CO capture at relatively high temperatures (50-75 °C; for example, flue gas) combined with steam regeneration.
通过蒸汽汽提研究了三胺接枝的大孔SBA-15 CO吸附剂的水热稳定性。相对于新鲜样品，在进行两个3小时的蒸汽再生循环后，观察到CO吸附量降低、CO/N比降低以及吸附动力学变慢，特别是在最低吸附温度（25°C）下。对选定样品进行48小时蒸汽汽提后的CO吸附测量表明，在首次暴露于蒸汽（3-6小时）期间的初始损失之后，吸附性能趋于稳定。然而，对于较高的吸附温度（即50和75°C），汽提后所有吸附性能几乎保持不变，这表明扩散限制的重要性。对蒸汽汽提前后接枝样品进行的热重分析和FTIR光谱分析分别表明没有胺浸出且胺基的化学性质没有变化。此外，在干燥条件下进行的六循环CO吸附/解吸实验表明没有热降解。然而，77K下的N吸附测量表明汽提后接枝样品的BET表面积显著降低。基于煅烧后接枝样品在汽提前后的孔径分布，提出暴露于蒸汽会使接枝材料发生重构，从而导致传质阻力。据推断，三胺接枝的大孔SBA-15吸附剂是在相对较高温度（50-75°C；例如烟道气）下结合蒸汽再生进行CO捕集的潜在候选材料。
