CO2 Hydrogenation on Unpromoted and M-Promoted Co/TiO2 Catalysts (M = Zr, K, Cs): Effects of Crystal Phase of Supports and Metal-Support Interaction on Tuning Product Distribution

Wenhui Li, Guanghui Zhang, Xiao Jiang, Yi Liu, Jie Zhu, Fanshu Ding, Zhongmin Liu, Xinwen Guo, Chunshan Song

Research output: Contribution to journalArticle

Abstract

Cobalt catalysts supported on TiO2 with different crystal forms (anatase and rutile) differ sharply in CO2 conversion and product selectivity for CO2 hydrogenation. The Co/rutile-TiO2 catalyst selectively catalyzed CO2 hydrogenation to CH4, while CO is the main product on the Co/anatase-TiO2 catalyst. In situ DRIFT (diffuse reflectance infrared Fourier transform) results have partially revealed the reaction pathway of CO2 hydrogenation on these two catalysts. On Co/rutile-TiO2, the reaction proceeds through the key intermediate formate species, which is further converted to CH4. Differently, the reaction on Co/anatase-TiO2 undergoes CO2 →∗CO, which desorbs to form gas-phase CO instead of subsequent hydrogenation. The strongly bonded∗CO is required to enhance the subsequent hydrogenation. By simply changing the calcination temperature of anatase TiO2, the product selectivity can be tuned from CO to CH4 with a significant increase in CO2 conversion due to the surface phase transition of the anatase to the rutile phase. The addition of Zr, K, and Cs further improves the CO, CO2, and H2 adsorption in both the capacity and strength over anatase- and rutile-supported catalysts. The Zr modification makes the reaction pathway over anatase-supported catalyst proceed via the intermediate formate species and enables the subsequent hydrogenation to CH4. In addition, the surface C/H ratio increases significantly in the presence of promoters (unpromoted < Zr-promoted < K-Zr-promoted ∼ Cs-Zr-promoted), which leads to the highest C2+ selectivity of 17% with 70% CO2 conversion over K-Zr-Co/anatase-TiO2 catalyst. These results reveal mechanistic insights into how the product distribution of Co/TiO2 catalysts can be manipulated through adjusting the adsorption performance and surface C/H ratio.

Original languageEnglish (US)
Pages (from-to)2739-2751
Number of pages13
JournalACS Catalysis
Volume9
Issue number4
DOIs
StatePublished - Apr 5 2019

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Catalyst supports
Titanium dioxide
Hydrogenation
Tuning
Metals
Crystals
Catalysts
Carbon Monoxide
formic acid
Adsorption
titanium dioxide
Calcination
Cobalt
Fourier transforms
Phase transitions
Infrared radiation
Gases

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)

Cite this

Li, Wenhui ; Zhang, Guanghui ; Jiang, Xiao ; Liu, Yi ; Zhu, Jie ; Ding, Fanshu ; Liu, Zhongmin ; Guo, Xinwen ; Song, Chunshan. / CO2 Hydrogenation on Unpromoted and M-Promoted Co/TiO2 Catalysts (M = Zr, K, Cs) : Effects of Crystal Phase of Supports and Metal-Support Interaction on Tuning Product Distribution. In: ACS Catalysis. 2019 ; Vol. 9, No. 4. pp. 2739-2751.
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abstract = "Cobalt catalysts supported on TiO2 with different crystal forms (anatase and rutile) differ sharply in CO2 conversion and product selectivity for CO2 hydrogenation. The Co/rutile-TiO2 catalyst selectively catalyzed CO2 hydrogenation to CH4, while CO is the main product on the Co/anatase-TiO2 catalyst. In situ DRIFT (diffuse reflectance infrared Fourier transform) results have partially revealed the reaction pathway of CO2 hydrogenation on these two catalysts. On Co/rutile-TiO2, the reaction proceeds through the key intermediate formate species, which is further converted to CH4. Differently, the reaction on Co/anatase-TiO2 undergoes CO2 →∗CO, which desorbs to form gas-phase CO instead of subsequent hydrogenation. The strongly bonded∗CO is required to enhance the subsequent hydrogenation. By simply changing the calcination temperature of anatase TiO2, the product selectivity can be tuned from CO to CH4 with a significant increase in CO2 conversion due to the surface phase transition of the anatase to the rutile phase. The addition of Zr, K, and Cs further improves the CO, CO2, and H2 adsorption in both the capacity and strength over anatase- and rutile-supported catalysts. The Zr modification makes the reaction pathway over anatase-supported catalyst proceed via the intermediate formate species and enables the subsequent hydrogenation to CH4. In addition, the surface C/H ratio increases significantly in the presence of promoters (unpromoted < Zr-promoted < K-Zr-promoted ∼ Cs-Zr-promoted), which leads to the highest C2+ selectivity of 17{\%} with 70{\%} CO2 conversion over K-Zr-Co/anatase-TiO2 catalyst. These results reveal mechanistic insights into how the product distribution of Co/TiO2 catalysts can be manipulated through adjusting the adsorption performance and surface C/H ratio.",
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CO2 Hydrogenation on Unpromoted and M-Promoted Co/TiO2 Catalysts (M = Zr, K, Cs) : Effects of Crystal Phase of Supports and Metal-Support Interaction on Tuning Product Distribution. / Li, Wenhui; Zhang, Guanghui; Jiang, Xiao; Liu, Yi; Zhu, Jie; Ding, Fanshu; Liu, Zhongmin; Guo, Xinwen; Song, Chunshan.

In: ACS Catalysis, Vol. 9, No. 4, 05.04.2019, p. 2739-2751.

Research output: Contribution to journalArticle

TY - JOUR

T1 - CO2 Hydrogenation on Unpromoted and M-Promoted Co/TiO2 Catalysts (M = Zr, K, Cs)

T2 - Effects of Crystal Phase of Supports and Metal-Support Interaction on Tuning Product Distribution

AU - Li, Wenhui

AU - Zhang, Guanghui

AU - Jiang, Xiao

AU - Liu, Yi

AU - Zhu, Jie

AU - Ding, Fanshu

AU - Liu, Zhongmin

AU - Guo, Xinwen

AU - Song, Chunshan

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AB - Cobalt catalysts supported on TiO2 with different crystal forms (anatase and rutile) differ sharply in CO2 conversion and product selectivity for CO2 hydrogenation. The Co/rutile-TiO2 catalyst selectively catalyzed CO2 hydrogenation to CH4, while CO is the main product on the Co/anatase-TiO2 catalyst. In situ DRIFT (diffuse reflectance infrared Fourier transform) results have partially revealed the reaction pathway of CO2 hydrogenation on these two catalysts. On Co/rutile-TiO2, the reaction proceeds through the key intermediate formate species, which is further converted to CH4. Differently, the reaction on Co/anatase-TiO2 undergoes CO2 →∗CO, which desorbs to form gas-phase CO instead of subsequent hydrogenation. The strongly bonded∗CO is required to enhance the subsequent hydrogenation. By simply changing the calcination temperature of anatase TiO2, the product selectivity can be tuned from CO to CH4 with a significant increase in CO2 conversion due to the surface phase transition of the anatase to the rutile phase. The addition of Zr, K, and Cs further improves the CO, CO2, and H2 adsorption in both the capacity and strength over anatase- and rutile-supported catalysts. The Zr modification makes the reaction pathway over anatase-supported catalyst proceed via the intermediate formate species and enables the subsequent hydrogenation to CH4. In addition, the surface C/H ratio increases significantly in the presence of promoters (unpromoted < Zr-promoted < K-Zr-promoted ∼ Cs-Zr-promoted), which leads to the highest C2+ selectivity of 17% with 70% CO2 conversion over K-Zr-Co/anatase-TiO2 catalyst. These results reveal mechanistic insights into how the product distribution of Co/TiO2 catalysts can be manipulated through adjusting the adsorption performance and surface C/H ratio.

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