This presents a challenge in optimizing for a specific product range ( Masuku et al., 2015). The Fischer–Tropsch (FT) reaction is generally assumed to be kinetically determined ( Lu et al., 2017) with an Anderson–Schulz–Flory product distribution that describe the product range with a single parameter α ( Eze and Masuku, 2018). Biegler, in Computer Aided Chemical Engineering, 2019 1 Introduction In the absence of Ru, Auger spectrum of 2 showed the shoulder at 779.5 eV which was attributed to the formation of cobalt carbide species during the FT reaction.
Such effect could arise from a partial electron charge transfer from Co(0) to the more electronegative Ru(0), favoring the adsorption of O atoms formed upon CO dissociation on positively charged Co δ + at high Ru content ( Fig. Furthermore, in situ XPS analysis revealed that the CoNPs surface remained zero-valent during FT reaction using 2 with low Ru loading (0.1–0.2 wt%) as catalyst, while oxide-like cobalt nanoparticles (CoO X) were detected for catalytic materials with Ru content higher than 0.2 wt%. Thus, the lower amount of Co(0) sites in 2 system could be at the origin of its lower FT activity in comparison to 2. Unfortunately, the lack of surface reconstruction was observed for Ru-free 2 system, for which linear CO-Co(0) IR vibration band stays unchanged at 220 ☌. FT-IR experiments under flowing syngas at 220 ☌ and 1 bar showed the CoNPs surface reconstruction, creating more defected Co(0) with the highest Ru content (1.2 wt% of Ru). To understand this behavior, in situ characterizations were performed. It was observed that both catalytic parameters were maximized for catalysts with 0.1–0.2 wt% Ru. 222 The FT activity in terms of metal-time-yield and initial turnover frequency was analyzed for both Ru-free and Ru-doped catalytic materials. Martínez and coworkers investigated the influence of Ru concentration in the bimetallic 2 material (10 wt% of Co and 0.1–1.2 wt% of Ru) on FT synthesis. On the other hand, the presence of 13CH 4 was demonstrated at 250 ☌, confirming that FT process goes through a surface carbide mechanism ( Fig. When the reaction was performed at 210 ☌, a mixture of unlabeled hydrocarbons was observed, suggesting the absence of exchange between carbide C atoms at the metal surface and CO in the gas phase. Heating of the as-prepared nanomaterial at 250 ☌ under H 2 led to the carbon desorption and exclusive formation of methane. 218 It was demonstrated that iron carbide NPs can be labeled with 13C to study their role in the CO hydrogenation.
216,217 In 2016, Chaudret and coworkers proposed an elegant approach using labelled 13CO to monitor the reaction by gas-phase NMR spectroscopy and mass spectrometry. The role of carbides and their performance in FT is still not totally clear and represent a goal of current studies.
215 One of the difficulties to study this mechanism is related to the ability of zero-valent metals to give their corresponding oxides or carbides. The reaction mechanism for FT synthesis with iron catalysts has been reported by Devis.
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