In Situ Encapsulated CuCo@M-SiO 2 for Higher Alcohol Synthesis from Biomass-Derived Syngas

Kang

et al. 2022

ACS Catal.

Higher alcohol synthesis (HAS) from syngas through nonpetroleum carbon resources is quite prospective but still challenging owing to the unsatisfactory selectivity and catalytic stability. Here, we proposed a monodisperse ε′-(Co x Fe1–x )2.2C alloy carbide catalyst derived from Co x Fe3–x O4 spinel oxide nanoparticles, which was applied in the HAS reaction. The Co/Fe molar ratio showed a significant impact on the evolution of active sites, and the catalyst with a Co/Fe molar ratio of 1/2 contained the highest ε′-(Co x Fe1–x )2.2C content of 80.2%, which achieved the best selectivity and space time yield toward higher alcohols (HA) as high as 38.5% and 1.932 g g(Fe + Co) –1 h–1, outperforming most of the reported modified Fischer–Tropsch synthesis catalysts for HAS. Density functional theory calculations further confirmed that the formation of ε′-(Co x Fe1–x )2.2C alloy carbide became more difficult when the Co/Fe ratio exceeds 1/2. It is demonstrated that the ε′-(Co x Fe1–x )2.2C exhibited moderate bonding with CO, which is crucial for the balance between CO dissociation and CO insertion, thus increasing the HA selectivity. The Co1Fe2 catalyst with a robust CoFe alloy carbide structure exhibited stable catalytic performance for over 300 h because of the inhibition of phase separation and surface carbon deposition. These insights into the formation and properties of CoFe alloy carbide may provide possibilities for the development of bimetallic catalysts for HAS.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

A Monodisperse ε′-(Co_xFe_1–x)_2.2C Bimetallic Carbide Catalyst for Direct Conversion of Syngas to Higher Alcohols

Kang

et al. 2022

ACS Catal.

“…In some representative CoCu based catalysts for HAS, such as the ZnO/ZrO 2 modified CuCoAl, 55 CuCo@M-SiO 2 , 16 CuO/LaCoO 3 , 57 Co-Cu/CeO 2 , 58 and 3Cu-5Co/(Mn−Al) 19 catalysts, the reported optimal Co/Cu ratio was around 1−2, which was lower than the value of 2.5 in Co 2.5 Cu 1 -773. The higher optimal ratio of Co/Cu in this case may be due to the presence of additional Co species as active sites in catalyst, like the CoO and Co 2 SiO 4 species.…”

Section: ■ Results and Discussionmentioning

confidence: 97%

“…Great efforts have been made to improve the stability of CoCu catalysts for HAS. Using the encapsulation and confinement by the support as well as the strong metal–support interaction, the stability of catalysts can be significantly improved. − For example, mesoporous silica encapsulated CoCu bimetallic catalysts prepared by the solvent coordination-assisted impregnation strategy were proposed for HAS and showed a great stability over 300 h, which originated from the confinement and antiagglomeration effect of both the mesoporous support and solvent-derived carbon species. , In addition, a graphene-LaFeO 3 perovskite composite supported CoCu catalyst exhibited a good stability over 180 h, which was benefited from the strong interaction of CuCo alloy with LaFeO 3 . However, the preparation methods of the above catalysts were complicated.…”

Section: Introductionmentioning

confidence: 99%

Lamellar-Structured Silicate Derived Highly Dispersed CoCu Catalyst for Higher Alcohol Synthesis from Syngas

et al. 2022

Ind. Eng. Chem. Res.

The direct conversion of bioderived syngas to high value-added higher alcohols (HA) is quite promising in the energy field. CoCu based catalysts show great potential for higher alcohol synthesis (HAS). However, the catalytic performance and stability still need to be improved. Herein, by using a facile ammonia evaporation method combined with ion exchange, a series of lamellar-structured CoCu bimetallic silicates were prepared and evolved into highly dispersed and close interacted CoCu active sites, which showed excellent space time yield toward HA of 15.4 mmol·gcat –1·h–1 and superior stability over 500 h. It is demonstrated that the Co0 of the CoCu alloy (or some Co particles) favored CO dissociation, while the Cu and Coδ+ of CoO and Co2SiO4 species benefited the CO nondissociative adsorption, and the appropriate cooperation of those sites led to the optimal catalytic performance in HAS. Moreover, the different Co and Cu sites can be maintained owing to the presence of the Co–O–Si structure and resulting in excellent catalyst stability. This method for preparing highly dispersed and close interacted CoCu catalysts would provide guidance for further design of high-performance CoCu catalysts for HAS.

“…As shown in Figure , several intermediates or products such as CH 2 */CH 3 *, CH 3 CHO*, CH 3 O*/CH 3 CH 2 O*, HCOO*, and CH 4 were detected. The peaks at 2930 and 1461 cm –1 are attributed to the unsaturated C–H bond asymmetric stretching (ν as C–H ) and asymmetric bending (δ as C–H ) in CH 2 */CH 3 * species, which originate from the direct or H-assisted CO dissociation, and the peaks at 3016 cm –1 belong to the saturated C–H bond in CH 4 , which gradually increases with the prolonged time on stream. ,, The peak at 1580 cm –1 is attributed to CHO*, which dominated at the beginning of the reaction and was gradually weakened after 10 min . Meanwhile, the band at 1438 cm –1 attributed to CH 3 CHO* species emerged and became stronger, confirming that formation of CH 3 CHO* species follows the CO*/CHO* insertion mechanism, which was proposed by Xu et al and generally accepted for HAS catalyzed over modified F–T catalysts.…”

Section: Resultsmentioning

confidence: 99%

Janus Au–Fe_2.2C Catalyst for Direct Conversion of Syngas to Higher Alcohols

ACS Sustainable Chem. Eng.

Guo

et al. 2021

Higher alcohol synthesis (HAS) direct from syngas using Febased catalysts is quite promising, but there are still problems in the construction of intimate-contact and stable dual sites to obtain satisfactory higher alcohol selectivity and space time yield (STY). Herein, a series of Au−Fe 2.2 C catalysts derived from monodisperse Janus Au−Fe 3 O 4 nanoparticles with different Fe/Au ratios were prepared. The optimal catalyst with a Fe/Au molar ratio of 11.6 achieved the most Janus nanoparticles and exhibited the highest STY toward higher alcohols of 0.195 g g cat −1 h −1 and excellent catalytic stability over 200 h. The superior performance of this catalyst was attributed to the unique Au−Fe 2.2 C Janus structure, which could enhance both CO insertion and CO dissociation as well as their synergistic effect. The correlation of the CO adsorption behavior and STY toward alcohols was established as well, indicating that the balance between CO nondissociated adsorption and CO dissociated adsorption played an important role in enhancing the alcohol formation. Moreover, the strong interaction between Au and iron species in Janus nanoparticles could facilitate the formation of ε′-Fe 2.2 C and benefit the stability of the catalyst. These results may provide new ideas for the design and fabrication of high-performance catalysts with dual sites for HAS.