Pore size effects on physicochemical properties of Fe-Co/K-Al 2 O 3 catalysts and their catalytic activity in CO 2 hydrogenation to light olefins

Thanapha Numpilai, Narong Chanlek, Yingyot Poo-Arporn, Suttipong Wannapaiboon, Chin Kui Cheng, Nuchanart Siri-Nguan, Thana Sornchamni, Paisan Kongkachuichay, Metta Chareonpanich, Günther Rupprechter, Jumras Limtrakul, Thongthai Witoon

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66 Scopus citations

Abstract

In this work, the hydrogenation of CO 2 to light olefins has been studied over the Fe-Co/K-Al 2 O 3 catalysts, while focusing on the impact by the pore sizes of Al 2 O 3 supports including 6.2 nm (S-Al 2 O 3 ), 49.7 nm (M-Al 2 O 3 ) and 152.3 nm (L-Al 2 O 3 ) on the structure and catalytic performance. The characterization results demonstrate that the pore sizes of the Al 2 O 3 supports play a vital role on the crystallite size of Fe 2 O 3 , the reducibility of Fe 2 O 3 and the adsorption-desorption of CO 2 and H 2 . The catalyst with the smallest pore size (CS-Al 2 O 3 ) allows the formation of a small Fe 2 O 3 crystallite size due to pore confinement effects, yielding a low active component (Fe) after reduction at 400 °C for 5 h. The catalysts with the larger pore sizes of 49.7 nm (CM-Al 2 O 3 ) and 152.3 nm (CL-Al 2 O 3 ) provide the larger Fe 2 O 3 crystallite sizes which require a longer reduction time for enhancing degree of reduction, resulting in a high metallic Fe content, leading to a high CO 2 conversion and a high selectivity toward hydrocarbon. Eliminating diffusion limitation by increasing the pore sizes of Al 2 O 3 supports can suppress the hydrogenation of olefins to paraffins and thus the largest pore catalyst (CL-Al 2 O 3 ) gives the highest olefins to paraffins ratio of 6.82. Nevertheless, the CL-Al 2 O 3 also favors the formation of C 5+ hydrocarbon. Therefore, the highest light olefins yield (14.38%) is achieved over the catalyst with appropriated pore size (CM-Al 2 O 3 ).

Original languageBritish English
Pages (from-to)581-592
Number of pages12
JournalApplied Surface Science
Volume483
DOIs
StatePublished - 31 Jul 2019

Keywords

  • Al O
  • CO hydrogenation
  • Fe-based catalysts
  • Light olefins
  • Pore sizes

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