Investigation of the highly tunable selectivity to linear α-olefins in Fischer–Tropsch synthesis over silica-supported Co and CoMn catalysts by carburization–reduction pretreatment

Zheng, Jiao; Cai, Jian; Jiang, Feng; Xu, Yuebing; Liu, Xiaohao

doi:10.1039/c7cy01764b

Cited by 56 publications

(55 citation statements)

References 63 publications

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“…Figure c shows the H 2 ‐TPR profiles over Mn‐modified Fe 3 O 4 ‐ NaAc catalysts after calcination. It can be seen that a new reduction peak at around 315 °C appears with the addition of Mn; this is assigned to the reduction of MnO 2 to Mn 3 O 4 ,. The reduction peaks for Fe 3 O 4 ‐ NaAc at 410 and 624 °C are assigned to the reduction of Fe 3 O 4 to FeO, and FeO to α‐Fe, respectively, which distinctly shifts to lower temperature with the addition of Mn; this suggests that Mn could facilitate the reduction of Fe oxides.…”

Section: Resultsmentioning

confidence: 99%

“…The decreased Fe 3 O 4 content seems to be transformed into χ‐Fe 5 C 2 . Indeed, the χ‐Fe 5 C 2 content is substantially higher for both Fe 3 O 4 ‐ NaAc and 0.09Mn/Fe 3 O 4 ‐ NaAc compared to that for Fe 3 O 4 ‐ pur and 0.09Mn/Fe 3 O 4 ‐ pur , which is in well accordance with XRD patterns (Figure b); this could be ascribed to the promoted carburization of metallic α‐Fe into χ‐Fe 5 C 2 due to the presence of Na for facilitating CO dissociation …”

Section: Discussionmentioning

confidence: 99%

“…It can be seen that a new reduction peak at around 315 8C appears with the addition of Mn; this is assigned to the reduction of MnO 2 to Mn 3 O 4 . [39,40] The reduction peaks for Fe 3 O 4 -NaAc at 410 and 624 8C are assigned to the reduction of Fe 3 O 4 to FeO, and FeO to a-Fe, respectively, which distinctly shifts to lower temperature with the addition of Mn; this suggests that Mn could facilitate the reduction of Fe oxides. Figure S4 Figure 4a, for Fe 3 O 4pur catalyst, it can be seen that a broad desorption peak with the gradually increased intensity in the temperature range from 350 to 750 8C appears obviously.…”

Section: O 4 Catalystsmentioning

confidence: 99%

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Unravelling the New Roles of Na and Mn Promoter in CO₂ Hydrogenation over Fe₃O₄‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins

et al. 2018

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The direct production of light α‐olefins (C2=‐C4=) from CO2 is of great importance as this process can convert the greenhouse gas into the desired chemicals. In this study, the crucial roles of Na and Mn promoter in CO2 hydrogenation to produce light α‐olefins via the Fischer‐Tropsch synthesis (FTS) over Fe3O4‐based catalysts are investigated. The results indicate that both Na and Mn promoter can enhance the reducibility of Fe3O4. In situ XPS and DFT calculations show that Na facilitates the reduction by electron donation from Na to Fe as the oxygen vacancy formation energy is reduced by Na. In contrast, Mn promotes the reduction by the presence of oxygen vacancy in MnO as the oxygen in Fe oxide can spillover to the vacancy in MnO spontaneously. For un‐promoted Fe3O4 catalysts, CO2 hydrogenation dominantly produces light n‐paraffins. The addition of Na remarkably shifts the selectivity to light α‐olefins with a sharp decline in the selectivity to light n‐paraffins, which is attributed to the electron donation from Na to Fe resulting in the promoted CO dissociation and the favorable β‐H abstraction of surface short alkyl‐metal intermediates. The addition of Mn into Na‐containing Fe3O4 catalysts can obviously further enhance the selectivity to light α‐olefins as the spatial hindrance of Mn suppresses the chain growth to increase the amount of surface short alkyl‐metal intermediates.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: O 4 Catalystsmentioning

confidence: 99%

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Unravelling the New Roles of Na and Mn Promoter in CO₂ Hydrogenation over Fe₃O₄‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins

et al. 2018

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“…Then, carburization of the Co (111) phase using CO produces Co 2 C (111). The second reduction involving the Co 2 C (111) results in two phases: Co (101) and Co (002) …”

Section: Introductionmentioning

confidence: 99%

Activation and deactivation scenarios in a plasma‐synthesized Co/C catalyst for Fischer‐Tropsch synthesis

Aluha

Abatzoglou

2018

Can J Chem Eng

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A carbon‐supported cobalt nano‐catalyst (Co/C) synthesized through plasma was tested for Fischer‐Tropsch activity. Catalyst deactivation and activation protocols studied included in situ sample pre‐treatment at 673 K in gas flowing at the rate of 250 cm3 · min−1 in: (a) H2 only, (b) CO only, and (c) CO followed by H2, with each cycle lasting 24 h. The so‐treated catalyst samples were then tested for FTS activity for over 50 h of time‐on‐stream (TOS), at 2.2 MPa pressure and 493 or 518 K temperature in a 3‐phase continuously‐stirred tank slurry reactor (3‐φ‐CSTSR) using squalane (C30H62) as the carrier liquid phase. The feed gas composition of molar H2:CO = 1.7 comprising 50 % H2, 30 % CO, and 10 % CO2 balanced in Ar for mass balance determination, flowing at a gas hourly space velocity (GHSV) of 3360 cm3 · h−1 · g−1 of catalyst. Fresh catalysts and those reduced by CO‐only were completely inactive at 493 K and initial inactivity was attributed to the excessive C matrix formed around the metal nanoparticles during catalyst synthesis. The sample that was reduced by H2 only was the most active, although it showed the fastest declining activity due to cumulative high H2O vapour pressure in the FTS reactor, while the sample pre‐treated in both CO and H2 demonstrated a higher degree of stability with TOS.

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“…Furthermore, these authors observed that MnO x improved the dispersion of supported FeO x , facilitating its reduction and enhanching the carburization of FeO x . Interestingly, Xiaohao and co‐workers have recently investigated the addition of MnO x to a Co/SiO 2 FTS catalyst . These authors found that MnO x affects the formation of Co 2 C, a phase which has been recently shown to have a high selectivity towards lower olefins…”

Section: Resultsmentioning

confidence: 99%

Cobalt‐Iron‐Manganese Catalysts for the Conversion of End‐of‐Life‐Tire‐Derived Syngas into Light Terminal Olefins

Falkenhagen

Maisonneuve

Paalanen

et al. 2018

Chemistry A European J

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Co-Fe-Mn/γ-Al O Fischer-Tropsch synthesis (FTS) catalysts were synthesized, characterized and tested for CO hydrogenation, mimicking end-of-life-tire (ELT)-derived syngas. It was found that an increase of C -C olefin selectivities to 49 % could be reached for 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn/γ-Al O with Na at ambient pressure. Furthermore, by using a 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al O catalyst the selectivity towards the fractions of C and CH could be reduced, whereas the selectivity towards the fraction of C olefins could be improved to 12.6 % at 10 bar. Moreover, the Na/S ratio influences the ratio of terminal to internal olefins observed as products, that is, a high Na loading prevents the isomerization of primary olefins, which is unwanted if 1,3-butadiene is the target product. Thus, by fine-tuning the addition of promoter elements the volume of waste streams that need to be recycled, treated or upgraded during ELT syngas processing could be reduced. The most promising catalyst (5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al O ) has been investigated using operando transmission X-ray microscopy (TXM) and X-ray diffraction (XRD). It was found that a cobalt-iron alloy was formed, whereas manganese remained in its oxidic phase.

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Investigation of the highly tunable selectivity to linear α-olefins in Fischer–Tropsch synthesis over silica-supported Co and CoMn catalysts by carburization–reduction pretreatment

Abstract: An efficient strategy to tune the selectivity to α-olefins in FTS over Co-based catalysts has been developed.

Cited by 56 publications

References 63 publications

Unravelling the New Roles of Na and Mn Promoter in CO₂ Hydrogenation over Fe₃O₄‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins

Unravelling the New Roles of Na and Mn Promoter in CO₂ Hydrogenation over Fe₃O₄‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins

Activation and deactivation scenarios in a plasma‐synthesized Co/C catalyst for Fischer‐Tropsch synthesis

Cobalt‐Iron‐Manganese Catalysts for the Conversion of End‐of‐Life‐Tire‐Derived Syngas into Light Terminal Olefins

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Investigation of the highly tunable selectivity to linear α-olefins in Fischer–Tropsch synthesis over silica-supported Co and CoMn catalysts by carburization–reduction pretreatment

Abstract: An efficient strategy to tune the selectivity to α-olefins in FTS over Co-based catalysts has been developed.

Cited by 56 publications

References 63 publications

Unravelling the New Roles of Na and Mn Promoter in CO2 Hydrogenation over Fe3O4‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins

Unravelling the New Roles of Na and Mn Promoter in CO2 Hydrogenation over Fe3O4‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins

Activation and deactivation scenarios in a plasma‐synthesized Co/C catalyst for Fischer‐Tropsch synthesis

Cobalt‐Iron‐Manganese Catalysts for the Conversion of End‐of‐Life‐Tire‐Derived Syngas into Light Terminal Olefins

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Unravelling the New Roles of Na and Mn Promoter in CO₂ Hydrogenation over Fe₃O₄‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins

Unravelling the New Roles of Na and Mn Promoter in CO₂ Hydrogenation over Fe₃O₄‐Based Catalysts for Enhanced Selectivity to Light α‐Olefins