Abbas Mohamed, Zhang Juan, Lin Ke, Chen Jiangang
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China; Ceramics Department, National Research Centre, El-Bohouth Street, 12622 Cairo, Egypt.
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China.
Ultrason Sonochem. 2018 Apr;42:271-282. doi: 10.1016/j.ultsonch.2017.11.031. Epub 2017 Nov 24.
In this study, FeO nanocubes (NCs) decorated on RGO nanosheets (NSs) structures were successfully synthesized through an innovative and environmentally-friendly rapid sonochemical method. More importantly, iron(II) sulfate heptahydrate and GO were employed as precursors and water as reaction medium, meanwhile, NaOH within the generated free radicals from the high intensity ultrasound were sufficient as reducing and base agent in our clean synthesis. Moreover, the hydrothermal method as a conventional approach was employed to synthesize the same catalysts for the comparison with the ultrasonocation technique. The as-synthesized FeO and RGO/FeO NSs catalysts were exposed to industrially relevant Fischer-tropsch synthesis (FTS) conditions at various reaction temperatures (250-290 °C), and they subjected to fully characterization before and after FTS reaction using XRD, TEM, HRTEM, EDS mapping, XPS, FTIR, BET, H-TPR, H-TPD and CO-TPD to understand the structure-performance relationships. Notably, the catalysts produced using the sonochemical method had a better CO conversion rate [FeO (80%), RGO/FeO (82%)] than the hydrothermally synthesized catalysts. However, compared to the naked-FeO catalysts, the sonochemically and hydrothermally synthesized RGO-supported FeO catalysts had higher long chain hydrocarbon (C5+) selectivity values (72% and 67%) and C-C olefin/paraffin selectivity ratio (3.2 and 2) and low CH4 selectivity values (6% and 8.5%), respectively. This can be attributed to their high surface area, the degree of reducibility, and content of Hägg iron carbide (χ-FeC) as the most active phase of the FTS reaction. Proposed reaction mechanisms for the sonochemical and hydrothermal reaction synthesis of FeO and RGO/FeO nanoparticles are discussed. In conclusion, our developed surfactantless-sonochemical method holds promise for the eco-friendly synthesis of highly efficient catalysts materials for FTS reaction.
在本研究中，通过一种创新的环境友好型快速声化学方法成功合成了负载于氧化石墨烯纳米片（NSs）结构上的氧化亚铁纳米立方体（NCs）。更重要的是，以七水合硫酸亚铁和氧化石墨烯为前驱体，水为反应介质，同时，高强度超声产生的自由基中的氢氧化钠在我们的清洁合成中足以作为还原剂和碱剂。此外，采用水热法作为传统方法合成相同的催化剂，以便与超声化学技术进行比较。将合成的氧化亚铁和氧化石墨烯/氧化亚铁纳米片催化剂在不同反应温度（250 - 290℃）下置于与工业相关的费托合成（FTS）条件下，并在FTS反应前后使用XRD、TEM、HRTEM、EDS图谱、XPS、FTIR、BET、H-TPR、H-TPD和CO-TPD进行全面表征，以了解结构 - 性能关系。值得注意的是，使用声化学方法制备的催化剂具有比水热合成催化剂更好的CO转化率[氧化亚铁（80%），氧化石墨烯/氧化亚铁（82%）]。然而，与裸氧化亚铁催化剂相比，声化学法和水热法合成的负载氧化石墨烯的氧化亚铁催化剂分别具有更高的长链烃（C5+）选择性值（72%和67%）和碳 - 碳烯烃/石蜡选择性比（3.2和2）以及较低的CH4选择性值（6%和8.5%）。这可归因于它们的高表面积、还原度以及作为FTS反应最活跃相的 Hägg 碳化铁（χ-FeC）含量。讨论了氧化亚铁和氧化石墨烯/氧化亚铁纳米颗粒的声化学和水热反应合成的反应机理。总之，我们开发的无表面活性剂声化学方法有望用于生态友好地合成用于FTS反应的高效催化剂材料。
