Effect of the support on cobalt carbide catalysts for sustainable production of olefins from syngas

Abstract

Co2C-based catalysts with SiO2, γ-Al2O3, and carbon nanotubes (CNTs) as support materials were prepared and evaluated for the Fischer-Tropsch to olefin (FTO) reaction. The combination of catalytic performance and structure characterization indicates that the cobalt-support interaction has a great influence on the Co2C morphology and catalytic performance. The CNT support facilitates the formation of a CoMn composite oxide during calcination, and Co2C nanoprisms were observed in the spent catalysts, resulting in a product distribution that greatly deviates from the classical Anderson-Schulz-Flory (ASF) distribution, where only 2.4 C% methane was generated. The Co3O4 phase for SiO2-and γ-Al2O3-supported catalysts was observed in the calcined sample. After reduction, CoO, MnO, and low-valence CoMn composite oxide were generated in the γ-Al2O3-supported sample, and both Co2C nanospheres and nanoprisms were identified in the corresponding spent catalyst. However, only separated phases of CoO and MnO were found in the reduced sample supported by SiO2, and Co2C nanospheres were detected in the spent catalyst without the evidence of any Co2C nanoprisms. The Co2C nanospheres led to a relatively high methane selectivity of 5.8 C% and 12.0 C% of the γ-Al2O3-and SiO2-supported catalysts, respectively. These results suggest that a relatively weak cobalt-support interaction is necessary for the formation of the CoMn composite oxide during calcination, which benefits the formation of Co2C nanoprisms with promising catalytic performance for the sustainable production of olefins via syngas.

Effect of Reaction Pressures on Structure–Performance of Co2C-Based Catalyst for Syngas Conversion

“…The direct production of olefins via syngas conversion is an alternative process for the production of key chemical building blocks from non-petroleum-based sources. − More and more studies focus on the improvement of catalytic performance with high selectivity to lower olefins (C 2–4 = ) directly from syngas. , Recently, based on the concept of OX-ZEO bifunctional catalysis, Jiao et al reported that a composite catalyst (ZnCrO x/ MSAPO) affording two types of active sites with complementary properties could reach C 2–4 = selectivity as high as 80% . Cheng et al also found that the coupling of methanol-synthesis and methanol-to-olefins reactions with a bifunctional catalyst (ZnZrO x/ SAPO-34) can realize the direct conversion of syngas to lower olefins with high selectivity .…”

Direct Conversion of Syngas to Higher Alcohols over Multifunctional Catalyst: The Role of Copper-Based Component and Catalytic Mechanism

“…In addition, Co 2 C can be used instead of Cu component as the active site for CO nondissociative adsorption, − and the Co/Co 2 C interface acts as dual active sites for alcohol formation. The appropriate proportion of Co/Co 2 C was considered to show profound influence on selectivity and stability. , In our previous work, an effective strategy was developed by tuning chemical environment and synergistic relay reaction to promote the production of higher alcohols . It was found that the highly dispersed Rh δ+ or Ru δ+ species facilitated the stable existence of Co 2 C and catalyzed the coupling of syngas and in situ generated olefins to produce extra oxygenates via hydroformylation.…”

Syngas Conversion to Aromatics over the Co2C-Based Catalyst and HZSM-5 via a Tandem System

“…With the increasing serious shortage of petroleum resources, it is necessary to make full use of alternative nonpetroleum feedstocks. − Syngas (CO/H 2 ) can be generated from a variety of carbon-containing sources including coal, biomass, and natural gas. − Fischer–Tropsch synthesis (FTS) is a promising technology for the conversion of syngas to fuels and chemicals. − However, the main products of FTS are mostly linear paraffins with a broad Anderson–Schulz–Flory distribution. , For the purpose of high selectivity to value-added chemicals (such as olefins, alcohols, and aromatics) during the syngas conversion process, development of new catalyst systems is highly desirable . Aromatics are important chemical raw materials, mainly used as monomers for the production of various polymers such as polystyrene, phenolic resins, and so forth. , Aromatics can also be used as additive to increase the octane number of gasoline.…”