Novel preparation method of highly active Co/SiO2 catalyst for Fischer-Tropsch synthesis with chelating agents

Abstract

Co/SiO 2 catalysts were prepared by the incipient wetness method using the aqueous Co nitrate solution modified with various organic acids and/or chelating agents followed by drying and calcination. After H 2 reduction at 773 K, the catalyst prepared with nitrilotriacetic acid (NTA) showed Fischer-Tropsch synthesis (FTS) activity ca. 3 times higher than the catalyst without additives under mild reaction conditions (503 K, 1.1 MPa).

Improvement of the Fischer–Tropsch Synthesis Activity of Co/SiO2 Catalyst by the Stepwise Impregnation Method with Chelating Agents

“…The space time yield (STY) of C 10-20 hydrocarbon obtained with this catalyst was 110 g kg-cat -1 h -1 at 503 K and 1.1 MPa, which was ca. 3 times greater than that with the catalyst without chelating agents [19]. On the contrary, the use of the aqueous solution of Co nitrate and the chelating agents having larger complex formation constants such as ethylenediamine-N,N,N 0 ,N 0 -tetraacetic acid (EDTA) and/or trans-1,2-diaminocyclohexane-N,N,N 0 ,N 0 -tetraacetic acid (CyDTA) showed relatively weaker effects.…”

“…On the contrary, the use of the aqueous solution of Co nitrate and the chelating agents having larger complex formation constants such as ethylenediamine-N,N,N 0 ,N 0 -tetraacetic acid (EDTA) and/or trans-1,2-diaminocyclohexane-N,N,N 0 ,N 0 -tetraacetic acid (CyDTA) showed relatively weaker effects. A volcanotype dependency was found when CO conversion over these catalysts was plotted against their logarithmic complex formation constants [18]. The maximum conversion was obtained with the catalyst prepared with the chelating agent having an intermediate complex formation constant, i.e.…”

“…Apart from these studies, the authors recently investigated the FTS activity of Co/SiO 2 catalysts prepared from an aqueous solution containing both Co nitrate and the chelating agent or organic acid (Co 2+ /chelating agent or organic acid = 1 mol mol -1 , Co loading = 5 mass% as metallic Co) having various complex formation constants with Co 2+ [18]. It was found that the use of the aqueous solution of Co nitrate and nitrilotriacetic acid (NTA) as an impregnating solution improves CO conversion over Co/SiO 2 catalyst by a factor of 3.…”

“…Furthermore, H 2 uptakes on these catalysts correlate well with their conversions. Therefore, it was suggested that the complex formation with Co 2+ (1:1 complex) having an intermediate stability in the impregnating solution increases the number of surface metallic Co sites, leading to an active Co/SiO 2 catalyst [18,19]. However, detailed mechanism of the activity improvement by these chelating agents is still unclear yet.…”

Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation

“…The small particle size is attributed to the wetting effect of the citric acid on the carbon support which has two modes to aid the mechanism of small particle generation. Firstly, the interaction of citric acid with the support protonates the surface of the carbon [13,14], and secondly, the resulting citrate anion complexes Co 2+ to form an anionic species [30,31] to induce the strong electrostatic interaction between the anionic cobalt citrate complex and the positively-charged carbon surface. Since SEA is limited to a sterically-limited, close packed monolayer of the ionic complex (including the hydration sheath) [15], the loading of Co is limited by the surface area of the support and the size of the hydrated ionic complex.…”