Ni/活性炭催化剂上乙醇羰基化性能演变研究

Performance Evolution of Ethanol Carbonylation on Ni/Activated Carbon Catalyst

中文关键词:  乙醇  羰基化  Ni/活性炭  失活

英文关键词:ethanol  carbonylation  Ni/activated carbon  deactivation

中文摘要:

      活性炭负载的Ni基催化剂(Ni/AC)在乙醇多相羰基化反应中具有良好的活性, 然而在反应过程中也存在着明显的失活, 因此明确催化剂在反应过程中的失活机理和原因对于提高催化剂的稳定性至关重要. 本文通过浸渍法制备了Ni/AC催化剂, 并对不同反应时间的催化剂进行表征分析. 研究结果表明, 在助催化剂碘乙烷的作用下, 反应初期Ni纳米颗粒再分散导致乙醇转化率升高, 而随着反应进行, Ni物种出现聚集的现象, 导致乙醇转化率明显降低. 在乙醇羰基化反应过程中, 催化剂中的积炭量不断增加, 导致催化剂的比表面积和孔体积不断减小; 结合相关表征发现积炭物种中存在产物丙酸、丙酸乙酯或含有丙酰基的中间体, 且积炭对催化剂的CO吸附有抑制作用, 从而使丙酸及丙酸乙酯的选择性降低. 进一步研究表明, 减少碘乙烷的比例会使催化剂的活性明显降低, 但催化稳定性有所提高.

英文摘要:

      Ni-based catalysts supported by activated carbon (Ni/AC) have been observed to display good activity for the heterogeneous ethanol carbonylation reaction. However, it has also been demonstrated that Ni/AC catalysts are susceptible to deactivation during the reaction process. Therefore, it is crucial to gain insight into the deactivation mechanism and the rationale during the reaction process, with an aim to enhance the catalyst's stability. In this study, the Ni/AC catalyst was prepared using an impregnation method, and the catalysts with varying reaction times were characterized and analyzed. The findings demonstrated that the re-dispersion of Ni nanoparticles in the presence of co-catalyst ethane iodide led to an enhancement in the initial ethanol conversion. Conversely, the aggregation of Ni species resulted in a notable reduction in the ethanol conversion over the 10 to 30 h period. The amount of carbon species deposited on the catalyst rises in conjunction with the duration of the reaction, which consequently results in a reduction in the specific surface area and pore volume of the catalyst. It was further determined that the carbon deposited species may contain propionic acid, ethyl propionate, or intermediates containing propionyl. The deposition of carbon significantly impeded the CO adsorption of the catalyst, resulting in a reduction in the selectivity of propionic acid and ethyl propionate. Subsequent investigation revealed that a reduction in the proportion of ethyl iodide led to a notable decline in catalyst activity, accompanied by an enhancement in catalytic stability.