II International Symposium on Carbon for Catalysis ABSTRACTS

OP-I-1
COBALT ON CARBON NANOFIBER CATALYSTS – STUDY OF PARTICLE SIZE
AND PROMOTER EFFECTS IN FISCHER TROPSCH CATALYSIS
de Jong K.P., Bezemer G.L.
Inorganic Chemistry and Catalysis, Debye Institute, Utrecht University
Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
e-mail: k.p.dejong@chem.uu.nl
Carbon nanofibers hold great potential as catalyst support material [1,2]. Supported
cobalt catalysts are used to convert synthesis gas (H 2 /CO) to higher alkanes and alkenes in the
so-called Fischer Tropsch (FT) process. As synthesis gas can be produced from a variety of
feedstocks including natural gas, heavy oil, coal and biomass and the products of FT can be
used as high-quality transportation fuels the research on cobalt catalysts is increasing. The use
of chemically inert carbon nanofibers as support material might limit the extent of interaction
with cobalt and possible promoters used in the final catalyst. In this contribution we report on
a study of (i) the effects of the cobalt particle size and (ii) the effects on manganese oxide
promotion on cobalt.
Carbon nanofibers (CNF) were produced from H 2 /CO over a Ni/SiO 2 catalyst as reported
before [3]. The raw material was purified by washing with caustic solution followed by reflux
in concentrated nitric acid. The latter treatment not only removed nickel but also gave rise to
surface oxidation that facilitated catalyst preparation [4]. The deposition of cobalt onto CNF
was carried out using several preparation techniques, viz. ion-adsorption, impregnation and
drying and deposition precipitation. The cobalt loading was varied between 1-22 wt%. The
catalysts were reduced at 350 °C prior to catalysis. Following reduction and passivation a
10%wt Co/CNF was impregnated with Mn(<strong>II</strong>) nitrate aqueous solution to arrive at loadings
ranging from 0.02-1 %wt Mn. Characterization of the catalysts involved hydrogen
chemisorption, XPS, (S)TEM, XRD and XANES/EXAFS. FT experiments were carried out at
H 2 /CO = 2 v/v, either at 1 bar and 220 °C or at 35 bar and 210 °C.
Co/CNF with cobalt particle size ranging from 2.7 to 24 nm with relatively narrow
particle sizes were obtained. A representative TEM of Co/CNF with an average particle size
of 13 nm is displayed together with the specific activity based on the amount of cobalt (CTY)
for the series of catalyst.
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