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Effect of K promotion of Fe and FeMn Fischer–Tropsch synthesis catalysts: Analysis at the site level using SSITKA

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Abstract.
Promoting a precipitated FeCuSiO2 catalyst with Mn has been shown to significantly improve its catalytic
activity for Fischer–Tropsch synthesis (FTS). Although the impact of K promotion on the activity of Fe
catalysts with and without Mn addition has been studied previously, no one has previously delineated
how K influences the concentration of active surface intermediates and the intrinsic site activities of
Fe and, more specifically, Mn-promoted Fe catalysts. This paper addresses that issue using steady-state
isotopic transient kinetic analysis (SSITKA). Adding K at relatively low concentrations to the base Fe and
Mn-promoted Fe catalysts improved the catalyst activity, but the activity of the catalysts declined with
the addition of an excess amount. The percentage of light olefins (C2–C4 fraction) and chain growth
probability (α) were enhanced, as expected with the presence of K, regardless of Mn addition. The
addition of K decreased the BET surface area and the concentration of surface exposed Fe0 atoms
(as determined by CO chemisorption). The intrinsic site activities (TOFITK) of all of the Fe catalysts
determined using SSITKA were essentially identical, regardless of the concentration of added K or Mn
promotion. This indicates that adding K to unpromoted or Mn-promoted Fe catalysts did not greatly
affect the activity of the active sites. Rather, the higher catalyst activities observed for the Fe and Mnpromoted Fe catalysts with K addition were due primarily to an increase in the number of active surface
intermediates leading to hydrocarbon products.

Keywords:
Fischer–Tropsch synthesis (FTS)
CO hydrogenation
Methanation
Steady-state isotopic transient kinetic
analysis (SSITKA)
Mn promotion
K promotion
Water–gas shift (WGS)
Fe-based FTS catalysts

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Informasi Detail

Judul Seri

Journal of Catalysis

No. Panggil

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Penerbit

London : Elsevier Inc.., 2008

Deskripsi Fisik

Journal of Catalysis 260 (2008) 7–16

Bahasa

English

ISBN/ISSN

00219517

Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

Versi lain/terkait

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