Characterization of new Co and Ru on α-WC catalysts for Fischer-Tropsch reaction

Abstract

An investigation of the performances in Fischer-Tropsch reaction of 1wt% M/WC(X) (M = Co, Ru; X = A, B), where A is a tungsten carbide protected by free carbon and B is a clean tungsten carbide, was carried out. Supported catalysts performances were compared to those of the parent tungsten carbides at 473 K and 20 bar. It was found that WC(A) produces mainly hydrocarbons but also 20-40% alcohols, whereas WC(B) activity is only towards linear alkanes. Before catalytic test, a reduction in pure hydrogen allows obtaining Co 0 and Ru 0 dispersed on layers of free carbon covering the WC core for the WC(A), and on a surface free of oxygen for WC(B). Co as Ru dispersions are improved on WC(B) compared to WC(A). A direct consequence is that Co/WC(B) has a better activity than Co/WC(A). Ru-W alloy formation could be responsible of the inobservance of a better activity for Ru/WC(B). On contrary, addition of Ru on WC(A) highly increases the activity and the production of heavy hydrocarbons. This beneficial effect, not observed with cobalt, could be attributed to a better dispersion of ruthenium on a carbon polymeric surface of WC.

Effect of carburization protocols on molybdenum carbide synthesis and study on its performance in CO hydrogenation

“…Specifically, the MoC760 catalyst showed the highest ˛ (0.42), and the lowest ˛ (0.34 and 0.35) were observed for MoC630 and MoC700, respectively, while MoC550 got a moderate value of ˛ (0.39). The variation of ˛ for our catalysts was consistent with that of GribovalConstant et al (0.33-0.43) [55].…”

“…In comparison, both MoC630 and MoC700 exhibited high initial activity (higher than 70%) and reached a steady-state activity (ca. 60%) at a time on stream of 72 h. It is noted that the initial activity of MoC760 was the lowest among all catalysts which increased Table 4 for our catalysts were obtained based on the CO chemisorption, and some data reported in literatures are shown for comparison [14,22,24,25,29,[55][56][57]. The CO conversion and CO consumption rate were different from each study due to different reaction conditions.…”

“…The study of Ranhotra et al [24] reported a relative low TOF for CH 4 (0.027 s −1 ) without the contribution of other carbon-containing products. It is also noted that only few CO hydrogenation was conducted at higher pressure (>1 atm) [25,29,55,57], while the TOF value was reported only by Schaidle and Thompson [57]. In their study, the TOF was 0.004 s −1 at a reaction temperature of 200 • C, while a higher TOF (0.36 s −1 ) was achieved at 290 • C. It is noteworthy that their catalyst was a mixture of Mo 2 C (hcp) and Mo 2 C (fcc).…”

Chemisorption of C3 hydrocarbons on cobalt silica supported Fischer?Tropsch catalysts

“…The energy (777-778 eV) of Co2p 3/2 lines and spinorbital splitting (15.0 eV) are typical of cobalt metal phase in CoN1 and CoN2 samples [27][28][29]. This suggests a higher relative concentration of cobalt metal phase, and therefore a higher extent of cobalt reduction.…”

“…Following the Shirley background subtraction and binding energy alignment, the sum of areas of Co2p XPS peaks in the catalysts and in the reference compounds has been normalized. The sets of linked parameters for Co 2+ and Co metallic species (energy center separation, width and height ratio, Gaussian/ Lorentzian form, asymmetry) have been determined from the XPS spectra of Co 2+ ions in oxidized CoAcl sample and of Co 0 atoms in the reference sample of Co metal [29]. The relative amount of Co metal phase (table 1) has been estimated from fitting the experimental and simulated XPS profiles.…”