Effect of Pre-Treatment Conditions on the Activity and Selectivity of Cobalt-Based Catalysts for CO Hydrogenation

Abstract

We investigated the effect of pre-treatment conditions on the activity and selectivity of cobalt catalysts for Fischer–Tropsch synthesis (FTS) by varying both the reduction atmosphere and the reduction temperature. Catalysts supported on SiO2, Al2O3, and TiO2, prepared via incipient wetness impregnation, were evaluated, and activation temperatures in the range 250–350 °C were considered. Activation with syngas led to a better product selectivity (low CH4, high selectivity to liquid hydrocarbons, and low paraffin to olefin ratio (P/O)) than the catalysts reduced in H2 at lower activation temperatures. The CoxC species suppressed the hydrogenation reaction, and it is hypothesised that this resulted in the high selectivity of olefins observed for the syngas pre-treated catalysts. On the basis of the experimental results, we postulated that a synergistic effect between Co0 and CoxC promotes the production of the long chain hydrocarbons and suppresses the formation of CH4. In addition, for systems aimed at producing lower olefins, syngas activation is recommended, and for the FTS plants that focus on maximising the production of higher molecular weight products, H2 activation might be considered. These results provide insights for the future FTS catalyst design and for target product-driven operations.

Comparative Studies of Co/SBA‐15 Catalysts Synthesized with Different Silica Sources Including Coal Fly Ash for Fischer‐Tropsch Synthesis

“…The visible darker dense areas represent Co 3 O 4 particles, and the lighter areas correspond to the SBA‐15 support. The large Co 3 O 4 particles observed on the CPSFSBA‐15 support suggest that the support had a wider pore, thus distributing bigger particles [32] …”

Influence of pretreatment conditions on the catalytic behavior and structure of Fe‐Co‐Mn / MgO FTS nanocatalyst: Modeling and optimization using RSM

“…In many performed works on the pretreatment conditions' effect on the FTS, the influence of one to three factors was considered and the usual method was employed. [14][15][16][17] Although, in the present work, the influence of four pretreatment variables and the RSM method was used; the RSM method enables us to study and observe the influence of the several factors on the responses concurrently that could be the main advantage of the present work over the previous works.…”

“…The obtained values for reactions rate reveal the following orders: The results show that the sample reduced by hydrogen has shown the highest rate for carbon monoxide consumption (2.205 Â 10 À1 mmol/g.min) and hydrocarbon production (1.65 Â 10 À1 mmol/g.min) and also the lowest rate for methane production (0.551 Â 10 À1 mmol/g.min). Shiba et al have reported that 14 the catalyst pretreated in H 2 exhibited higher CO reaction rates compared to the samples reduced in syngas at all reduction temperatures. They have also observed that the CH 4 formation rate was higher for the syngas treated sample at 350 C.…”

“…12 It has been reported that the cobalt precursor and its pretreatment conditions strongly affected both the structure of supported cobalt species and their catalytic behavior in FT synthesis. 13 Shiba et al 14 demonstrated the effect of the pre-treatment conditions by comparing the catalytic performance of Co-based catalysts treated with syngas or H 2 at different temperatures. They have observed a lower CH 4 selectivity, higher C 5 + selectivity, and lower P/O ratio for the catalysts treated with syngas at 250 C compared to the catalysts reduced either with H 2 at 250 C or syngas at 350 C. Li et al 15 investigated the influence of reductant agent on the catalytic performance of promoted Co/TiO 2 catalyst for FTS.…”

Valorization of Plastic Wastes for the Development of Adsorbent Designed for the Removal of Emerging Contaminants in Wastewater

“…Catalyst design is crucial to regulate the creation of CNTs [90]. The composition, pretreatment conditions, preparation procedures, interactions with support, and shape of catalysts all significantly impact their stability, activity, and selectivity [91,92]. The synthesis of high yields of CNTs that are of excellent quality, a very stable and active catalyst, is a prerequisite [93].…”