Abstract

In this work, we demonstrate an efficient and high-performance catalyst for the production of light olefins from synthesis gas employing manganese (Mn)-mediated graphene oxide. First the CO hydrogenation reaction was catalyzed using bimetallic alumina supported-cobalt-manganese catalysts with various ratio of cobalt to Mn (1:1, 1:2, 1:3, 2:1 and 3:1). After the determination of the effect of different ratios on C₂–C₄ light olefin production, the efficiency of nanoporous graphene and reduced graphene oxide as support at an optimum ratio of bimetallic Co–Mn/Al₂O₃ catalyst were evaluated. The catalysts were characterized by BET, TPR, FTIR, RAMAN, TGA, XRD, FESEM, ICP, and XPS measurements. The reactions carried out in a fixed bed reactor under the constant condition (320 °C, atmospheric pressure, H₂/CO = 1). It was identified that light olefin selectivity of the catalysts varies with different ratios. By increasing of the amount of Mn up to 1, methane formation decreased and light olefin selectivity increased. Conversely, with the further increase of the amount of Mn, light olefin selectivity decreases. This phenomenon is attributed to varying the degrees of Mn incorporation in the Co₃O₄ particles, which causes different degrees of reduction limiting the available metallic Co surface area. Also, the advantages of reduced graphene oxide supported nanoparticles (NPs) included higher conversion and C₂–C₄ light olefin selectivity in comparison with the graphene supported catalyst. The obtained results from the TPR revealed that the NPs reducibility was higher for the RGO supported catalyst. An increase of selectivity and conversion of Co–Mn/RGO catalyst is likely due to altering the surface interactions of NPs with the functional groups on reduced graphene oxide which was confirmed with XPS, FTIR and Raman analyses.

中文翻译：

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Mn和还原型氧化石墨烯对费-托反应的影响：一种由合成气生产轻质烯烃的有效催化剂

摘要

在这项工作中，我们证明了一种有效的高性能催化剂，用于使用锰（Mn）介导的氧化石墨烯从合成气生产轻质烯烃。首先，使用钴与锰的各种比例（1：1、1：2、1：3、2：1和3：1）的双金属氧化铝负载的钴锰催化剂催化CO的氢化反应。确定了不同比例对C ₂ -C ₄轻质烯烃生产的影响后，在最佳双金属Co-Mn / Al ₂ O ₃比例下，纳米多孔石墨烯和还原型氧化石墨烯作为载体的效率评估催化剂。通过BET，TPR，FTIR，RAMAN，TGA，XRD，FESEM，ICP和XPS测量来表征催化剂。反应在恒定条件（320℃，大气压，H ₂ / CO ＝ 1）下在固定床反应器中进行。已经确定，催化剂的轻烯烃选择性随不同比例而变化。通过增加Mn的量直至1，甲烷的形成减少并且轻烯烃的选择性增加。相反，随着Mn含量的进一步增加，轻烯烃的选择性降低。该现象归因于改变Co ₃ O ₄中Mn的结合程度。颗粒，导致不同程度的还原，限制了可用的金属Co表面积。同样，与石墨烯负载的催化剂相比，还原的氧化石墨烯负载的纳米颗粒（NPs）的优点包括更高的转化率和C ₂ -C ₄轻烯烃的选择性。TPR的结果表明，RGO负载催化剂的NPs还原性更高。XPS，FTIR和拉曼分析证实，Co-Mn / RGO催化剂的选择性和转化率的提高可能是由于改变了NPs与还原型氧化石墨烯上官能团的表面相互作用。