Fischer−Tropsch Synthesis over Activated-Carbon-Supported Cobalt Catalysts:  Effect of Co Loading and Promoters on Catalyst Performance

Abstract

The effects of Co loading and K, Ce, and Zr promoters on initial activities and selectivities of activated-carbon-supported cobalt (Co/AC) Fischer-Tropsch synthesis (FTS) catalysts, were studied under conditions of 240 °C, 2.4 MPa, 650 h -1 , and H 2 /CO ) 2:1 in a fixed-bed reactor. The reduction and metal dispersion properties of the catalysts were investigated through temperature-programmed reduction (TPR) and CO chemisorption. Detectable hydrocarbons up to C 20 were formed on the Co/AC catalysts. Co loading affected initial syngas conversion and CH 4 selectivity in the following order: 20%Co > 15%Co > 10%Co > 7%Co, whereas it had an opposite effect on content of C 12 -C 20 in the liquid organic product. K, Ce, and Zr promoters remarkably changed the initial catalytic performance of the Co/AC catalysts. Addition of K to the Co/AC catalyst significantly decreased the FTS activity and CH 4 selectivity, but increased the water gas shift (WGS) activity. Addition of Ce improved the Co/AC catalyst activity, accompanied by high CH 4 selectivity. Neither CO 2 nor CH 4 selectivity changed greatly on the Zr-promoted Co/AC catalyst even though the Zr promoter increased the FTS activity. The TPR and CO adsorption studies showed that K, Ce, and Zr promoters improved Co dispersion and interaction between Co oxide and the AC surface, which might be the reasons for the subsequent catalyst performance, especially for the Ce-and Zr-promoted catalysts. The TPR study also showed that the reduction steps of the reductively decomposed Co/AC catalysts by pure H 2 are Co 3 O 4 f CoO f Co.

Effect of K, Mn and Cr on the Fischer–Tropsch Activity of Fe:Co/TiO2 Catalysts

“…The site specific activity (TON) of K promotion also goes through a maximum with K content, consistent with earlier literature reports [4]. Results for K promotion of Co are more ambiguous [30]. (ii) Cr promotion effects on Fe:Co are also consistent with literature reports on Fe promotion.…”

“…Reports also indicate that K promoted Co catalysts on SiO 2 inhibits Co reducibility [29] while on C [30] the role of K (ratio 15/2 Co/K; very high) is to decrease FT activity and CH 4 selectivity and increase WGS activity. Another role for K promotion on Fe appears to be to enhance graphite and metal carbide formation [31,32].…”

Effect of Vanadium Promotion on Activated Carbon-Supported Cobalt Catalysts in Fischer–Tropsch Synthesis

“…Our previous work indicated that activated carbonsupported Co catalyst favored the formation of C 10 -C 20 hydrocarbon in Fischer-Tropsch Synthesis [17]. Meantime, we have also reported that the addition of ZrO 2 into Co/AC catalyst could increase CO conversion and enhance the selectivity to C 10 -C 20 hydrocarbon [17,18].…”

Ruthenium particle size and cesium promotion effects in Fischer–Tropsch synthesis over high-surface-area graphite supported catalysts

“…11,12 Selection of a support with a proper interaction with the active phase (or metal precursor) is of prime importance because of the balance between the reducibility and the dispersion of the active phase that defines FTS performance. Supports such as alumina, 13,14 silica, 15,16 titania 17 and carbon materials 10,[18][19][20][21][22] have been reported by many groups. Among them, carbon materials are considered to be more inert than the conventional oxide materials.…”