سال انتشار: ۱۳۸۷

محل انتشار: دومین کنگره بین المللی علوم و فناوری نانو

تعداد صفحات: ۲

نویسنده(ها):

Reza Malek Abbaslou – Department of Chemical Engineering, University of Saskatchewan, Saskatoon, SK, S7N5C5 Canada
Mariane Trépanier –
Mohamad Irani – Research Institute of Petroleum Industry, Tehran, Iran, P.O.Box 14665-1998
Ahmad, Tavasoli –

چکیده:

The present work was undertaken with the aim of exploiting the beneficial effects of carbon nanotubes (CNT) support and the incorporation of both Cobalt and iron species on performance for Fischer-Tropsch synthesis (FTS). In particular, emphasis is placed on the formation of Co/Fe intermetallics and their effects on the selectivity of FT synthesis.ExperimentalPurified (>98%) Mknano-MWCNT was used as support for the preparation of FTS catalysts. Bimetallic Co-Fe catalysts containing a fixed amount of Co (10wt.%) and different amounts of Fe ( 0.5, 1, 1.5, 2 and 4wt.%), were prepared. For comparison, two reference catalysts of 10wt.%Co/CNT and 10wt.%Fe/CNt were also prepared. All impregnates were dried at 120 oC and calcined at 350 oC. The catalysts were characterized by BET, TEM, SEM, EDS, XRD, and TPR. The activity and selectivity of the catalysts were assessed using syngas with H2/CO of 2 as feed, P= 2 MPa and T= 220 and 280oC and the results were compared with those of Co10/CNt and Fe10/CNT catalysts in a fixed bed micro-reactor.Results and discussionThe TEM images of Co10Fe4/CNT catalyst with highest metal loading revealed that most of the metal particles were homogeneously distributed inside the tubes and the rest on the outer surface (Fig. 1). The particles inside the tubes are fairly uniform and the most abundant ones are 3-6 nm in size in accordance with the average inner diameter of the CNTs, whereas those on the outer surface have grown to about 4-12 nm. The average size of these small particles is 4.8 nm. The EDS analysis of Co10Fe4/CNT showed two separate phases of Co and iron particles and also an alloy phase containing both Co and Fe metals. In the XRD (Fig.2)of the catalysts CNT peaks are appeared at 25 and 43o, Co3O4 peaks are appeared at 31.5 and 36.8o and Fe2O3 peaks are appeared at 35.7o and 44.5o [1,2]. In addition to these peaks, XRD of the catalysts with 2 and 4wt% of Fe showed the characteristic diffractions of a bimetallic Co/Fe phase at 2θ value of 36.4o(Fig.2). In the TPR profile of the 10Co/CNT the two peaks at 332 and 445oC are appeared and assigned to the reduction of Co3O4 to CoO, and CoO to Coo [12]. The TPR of the 10Fe/CNT showed three broad peaks at 372, 414, and 527 oC corresponding to the following consecutive reduction steps: α-Fe2O3→Fe3O4→FeO→Feo. The TPR of the bimetallic catalysts with 0.5 and 1wt% of iron were similar to that of the C010/CNT, although the position of the both peaks is shifted toward higher temperatures. In TPR of the catalysts with 1.5, 2, and 4wt% of Fe in addition to the above mentioned three peaks, a reduction shoulder appeared in the temperature range of 550–۶۵۰oC, with a peak centered at 554, 564 and 573oC for 10Co1.5Fe/CNT, 10Co2Fe/CNT, and 10Co4Fe/CNT catalysts respectively. This peak with a broad tailing assigned to Co-Fe alloys