Silica-Supported Cobalt Catalysts for Fischer–Tropsch Synthesis: Effects of Calcination Temperature and Support Surface Area on Cobalt Silicate Formation

Abstract

Cobalt silicate formation reduces the activity of the catalyst in Fischer-Tropsch synthesis (FTS). In this article, the effects of calcination temperature and support surface area on the formation of cobalt silicate are explored. FTS catalysts were prepared by incipient wetness impregnation of cobalt nitrate precursor into various silica supports. Deionized water was used as preparation medium. The properties of catalysts were characterized at different stages using FTIR, XRD and BET techniques. FTIR-ATR analysis of the synthesized catalyst samples before and after 48 h reaction identified cobalt species formed during the impregnation/calcination stage and after the reduction/reaction stage. It was found that in the reduction/reaction stage, metal-support interaction (MSI) added to the formation of irreducible cobalt silicate phase. Co/silica catalysts with lower surface area (300 m 2 /g) exhibited higher C 5? selectivity which can be attributed to less MSI and higher reducibility and dispersion. The prepared catalysts with different drying and calcination temperatures were also compared. Catalysts dried and calcined at lower temperatures exhibited higher activity and lower cobalt silicate formation. The catalyst sample calcined at 573 K showed the highest CO conversion and the lowest CH 4 selectivity.

A novel nano fischer‐tropsch catalyst for the production of hydrocarbons

“…The GC-MS results show that both catalysts have similar products profile, hydrocarbons ranging from C 6 to C 18 (Table 2, Figure 5) and are consistent with the literature [1,2]. FTS activity was reported as CO conversion rate (g CO/g Cat./h); therefore, it had the same trend (3) the filling of the support pores with hydrocarbon products which will prevents further CO hydrogenation by blocking the active cobalt sites, which needs to be further investigated [2,19]. Additionally, the Co/SiO 2 -NS favored the C 6 -C 8 alkanes and this warrants further investigation.…”

Reversible Redox Effect on Gas Permeation of Cobalt Doped Ethoxy Polysiloxane (ES40) Membranes

“…Firstly examining the role of cobalt oxides, the reduction process resulted in the formation of Co(II) as evidenced by the XPS analysis, which also corroborate with the Raman analysis. To be more specific, the reduction of cobalt oxide in the form of Co 3 O 4 at high temperatures (>350°C) produces thermodynamically-unstable intermediates in the form of Co(OH) 2 and CoO (equation 1)3536. This pathway was clearly evidenced by the presence of the Co(OH) 2 species in the infrared and the Raman spectra (Fig.…”

Characterization of Silica-Supported Cobalt Catalysts Prepared by Decomposition of Nitrates Using Dielectric-Barrier Discharge Plasma

“…Traditionally, the cobalt precursors in the prepared catalysts were transformed to oxides by thermal decomposition at certain temperatures. It has been reported that the decomposition temperature of Co(NO 3 ) 2 /SiO 2 ranges from 200 to 300°C depending on the status of the oxides [24][25][26][27]. In this paper, the catalyst was decomposed at 200 and 500°C in air or argon environment, and the percentage of weight loss due to temperature and time is shown in Table 1.…”